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February, 2005 1 - 1RF100a(c) 2005 Scott Baxter v2.0
Wireless CDMA RF Engineering: Week 1Wireless CDMA RF
Engineering: Week 1
Course RF100
February, 2005 1 - 2RF100a(c) 2005 Scott Baxter v2.0
Integrated RF/CDMA/Performance Training
•Wireless Industry Intro.•Modulation Techniques•Mult. Access Methods•Wireless system Architectures•RF Propagation
•Physics•Mechanisms•Models•Link Budgets•Margins•Pred. Tools•Meas. Tools
•Wireless Antennas•Intro: Principles•Families/Types•Choosing the right antenna•Selecting ants. •Other devices•Tests/Problems
•Traffic Engineering•Units, principles•Traffic tables•Wireless appls.
•Introduction to CDMA•Spread Sp. Principles•CDMA’s Codes•Fwd & Rev Channels•System Architecture•Power Control•Phone Architecture•Handoff Process
•Ec/Io, Eb/No•phone’s limitations
•Call Processing•CDMA Messages
•CDMA Flow Examples•Critical CDMA Issues
•Interference control•Managing Soft HO%•Capacity constraints
•Forward big picture•Reverse big picture
•Sys Architecture details•Lucent•Nortel•Motorola
•System Growth Mgt.•Stopgap measures•Longterm strategies•Multiple carriers•Intercarrier Handoff
•Intro to Optimization•Perspectives
•Bottom-up: mobile•Top-down: OMs
•Survey of Tools•Performance Goals•Design Implications
Monday Tuesday Wednesday Thursday Friday
Course RF100: RF Introduction, CDMA Principles, Understanding System Design & Performance Issues
Course RF200: Optimization Principles, Tools, Techniques, and Real-Life Examples/Exercises
•Optimization Overview•RF100 Fast Review•General Q&A•Meet the CDMA performance indicators•Signatures of CDMA transmission problems•The classic CDMA death scenario•Introduction to Performance Data•System-side tools and their implications
•Intro to Mobile Tools•Collection Tools
•Grayson, LCC, HP•PN Scanners
•HP, Grayson, Berkeley
•Post-processing•Analyzer, DeskCat
•Drive-test Demo files•Grayson•LCC
•Intro to Post-Processing•Analyzer, DeskCat
•Handsets as test tools•Drive-Test Demo Lab
•RSAT/Collect 2000!•Grayson Inspector
•Data Analysis and Post-Processing
•Analyzer, DeskCat•what events did you see?•Identifying root causes•Parameter & configuration changes
•Operators’ Corporate RF Benchmarking Overview•PN Scanner Lab
•HP, Grayson, Berkeley•Gathering data, interpreting problems
•Applied Optimization•common scenarios
Day 1 Day 2 Day 3 Day 4
February, 2005 1 - 3RF100a(c) 2005 Scott Baxter v2.0
Wireless Systems:How did we get here? What’s it all about?
Wireless Systems:How did we get here? What’s it all about?
RF100 Chapter 1
MTS, IMTS
February, 2005 1 - 4RF100a(c) 2005 Scott Baxter v2.0
Radio Hasn’t Been Around Long!
Days before radio.....• 1680 Newton first suggested
concept of spectrum, but for visible light only
• 1831 Faraday demonstrated that light, electricity, and magnetism are related
• 1864 Maxwell’s Equations: spectrum includes more than light
• 1890’s First successful demos of radio transmission
UN S
LF HF VHF UHF MW IR UV XRAY
February, 2005 1 - 5RF100a(c) 2005 Scott Baxter v2.0
First Wired Communication: TelegraphySamuel F.B. Morse had the idea of the telegraph on a sea cruise in the 1833. He studied physics for two years, and In 1835 demonstrated a working prototype, which he patented in 1837.Derivatives of Morse’ binary code are still in use today The US Congress funded a demonstration line from Washington to Baltimore, completed in 1844.1844: the first commercial telegraph circuits were coming into use. The railroads soon were using them for train dispatching, and the Western Union company resold idle time on railroad circuits for public telegrams, nationwide1857: first trans-Atlantic submarine cable was installed
Samuel F. B. Morseat the peak of his career
Field Telegraphyduring the US Civil War, 1860’s
Submarine Cable Installationnews sketch from the 1850’s
February, 2005 1 - 6RF100a(c) 2005 Scott Baxter v2.0
Wired Communication for Everyone: Telephony
By the 1870’s, the telegraph was in use all over the world and largely taken for granted by the public, government, and business. In 1876, Alexander Graham Bell patented his telephone, a device for carrying actual voices over wires. Initial telephone demonstrations sparked intense public interest and by the late 1890’s, telephone service was available in most towns and cities across the USA
Telephone Line Installation Crew1880’s
Alexander Graham Bell and his phonefrom 1876 demonstration
February, 2005 1 - 7RF100a(c) 2005 Scott Baxter v2.0
Radio Milestones1888: Heinrich Hertz, German physicist, gives lab demo of existance of electromagnetic waves at radio frequencies1895: Guglielmo Marconi demonstrates a wireless radio telegraph over a 3-km path near his home it Italy1897: the British fund Marconi’s development of reliable radio telegraphy over ranges of 100 kM1902: Marconi’s successful trans-Atlantic demonstration 1902: Nathan Stubblefield demonstrates voice over radio1906: Lee De Forest invents “audion”, triode vacuum tube
• feasible now to make steady carriers, and to amplify signals1914: Radio became valuable military tool in World War I1920s: Radio used for commercial broadcasting1940s: first application of RADAR - English detection of incoming German planes during WW II1950s: first public marriage of radio and telephony -MTS, Mobile Telephone System1961: transistor developed: portable radio now practical1961: IMTS - Improved Mobile Telephone Service1970s: Integrated circuit progress: MSI, LSI, VLSI, ASICs1979, 1983: AMPS cellular demo, commercial systems
Guglielmo Marconiradio pioneer, 1895
Lee De Forestvacuum tube inventor
MTS, IMTS
February, 2005 1 - 8RF100a(c) 2005 Scott Baxter v2.0
Overview of the Radio SpectrumFrequencies Used by Wireless Systems
3 4 5 6 7 8 9 10 12 14 16 18 20 22 24 26 28 30 GHz30,000,000,000 i.e., 3x1010 Hz
Broadcasting Land-Mobile Aeronautical Mobile TelephonyTerrestrial Microwave Satellite
0.3 0.4 0.5 0/6 0.7 0.8 0.9 1.0 1.2 1.4 1.6 1.8 2.0 2.4 3.0 GHz3,000,000,000 i.e., 3x109 Hz
UHF TV 14-69UHF GPSDCS, PCSCellular
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.2 1.4 1.6 1.8 2.0 2.4 3.0 MHz3,000,000 i.e., 3x106 Hz
AM LORAN Marine
3 4 5 6 7 8 9 10 12 14 16 18 20 22 24 26 28 30 MHz30,000,000 i.e., 3x107 Hz
Short Wave -- International Broadcast -- Amateur CB
30 40 50 60 70 80 90 100 120 140 160 180 200 240 300 MHz300,000,000 i.e., 3x108 Hz
FM VHF TV 7-13VHF LOW Band VHFVHF TV 2-6
February, 2005 1 - 9RF100a(c) 2005 Scott Baxter v2.0
In the late 1970’s, the FCC (USA Federal Communications Commission) allocated 40 MHz. of spectrum in the 800 MHz. range for public mobile telephony. FCC adopted Bell Lab’s AMPS (Advanced
Mobile Phone System) standard, creating cellular as we know it today
• The USA was divided into 333 MSAs(Metropolitan Service Areas) and over
300 RSAs (Rural Service Areas)In 1987, FCC allocated an additional 10 MHz. of “expanded spectrum”By 1990, all MSAs and RSAs had competing licenses granted and at least one system operating. In the 1990’s, additional technologies were developed for cellular
• TDMA (IS-54,55,56, IS-136) (also, GSM in Europe/worldwide)• CDMA (IS-95)
US Operators did not pay for their spectrum, although processing fees (typically $10,000’s) were charged to cover license administrative cost
Development of North American Cellular
333 MSAs300+ RSAs
February, 2005 1 - 10RF100a(c) 2005 Scott Baxter v2.0
North American Cellular Spectrum
In each MSA and RSA, eligibility for ownership was restricted• “A” licenses awarded to non-telephone-company applicants only• “B” licenses awareded to existing telephone companies only • subsequent sales are unrestricted after system in actual operation
Downlink Frequencies(“Forward Path”)
Uplink Frequencies(“Reverse Path”)
824 835 845 870 880 894
869
849
846.5825
890
891.5
Frequency, MHz
Paging, ESMR, etc.A B A B
Ownership andLicensing
Frequencies used by “A” Cellular OperatorInitial ownership by Non-Wireline companies
Frequencies used by “B” Cellular OperatorInitial ownership by Wireline companies
February, 2005 1 - 11RF100a(c) 2005 Scott Baxter v2.0
Development of North America PCS
51 MTAs493 BTAs
A D B E F C unlic.data
unlic.voice A D B E F C
1850 MHz.
1910 MHz.
1990 MHz.
1930 MHz.
15 15 155 5 5 15 15 155 5 5
PCS SPECTRUM ALLOCATIONS IN NORTH AMERICA
By 1994, US cellular systems were seriously overloaded and looking for capacity relief
• The FCC allocated 120 MHz. of spectrum around 1900 MHz. for new wireless telephony known as PCS (Personal Communications Systems), and 20 MHz. for unlicensed services
• allocation was divided into 6 blocks; 10-year licenses were auctioned to highest bidders
PCS Licensing and Auction Details• A & B spectrum blocks licensed in 51 MTAs (Major Trading Areas )
• Revenue from auction: $7.2 billion (1995) • C, D, E, F blocks were licensed in 493 BTAs (Basic Trading Areas)
• C-block auction revenue: $10.2 B, D-E-F block auction: $2+ B (1996)• Auction winners are free to choose any desired technology• About half the C-block winners were unable to pay for their licenses. They
wrangled in and out of court, with final disposition in 2005.
February, 2005 1 - 12RF100a(c) 2005 Scott Baxter v2.0
Major PCS Auction WinnersThe Largest Players, Areas, and Technologies
Sprint PCS• Began as partnership of Sprint, TCI, Cox Cable• Bid & won in 2/3 of US markets A or B blocks• Sprint won D and/or E blocks in remaining markets• CDMA: Mix of Nortel, Lucent, Motorola
AT&T Wireless Systems• Bid & won a majority of markets in A&B Blocks• will combine and integrate service between its new
PCS 1900 systems and its former McCaw cellular 800 MHz. properties
• IS-136: mix of Lucent and Ericsson equipmentOther CDMA Operators
• Primeco: partnership of various operators• GTE, others
GSM Operators• Western Wireless, OmniPoint, BellSouth, GTE,
Powertel, Pacific Bell• Mix of Ericsson, Nokia, and Nortel networks
For auction details, check www.fcc.gov
Sprint PCSCDMA
AT&T WirelessIS-136
PrimecoCDMA
Western Wireless
Pacific Bell
PowertelBellSouth
OmniPoint
Aerial
GSM
February, 2005 1 - 13RF100a(c) 2005 Scott Baxter v2.0
Progress in Radio Technology Development
Systems, Signals, & Devices
RADAR
Spark Vacuum Tubes
Discrete Transistors
MSILSI
VLSI, ASICS
DevicesModulation CW AM FMFSK PM PSK QAM DQPSK GMSK
Radio Communication SystemsMobile Telephony30-50MHz
150MHz450MHz800MHz
1900MHzAM Bcst1MHz FM Bcst100MHzVHF-TV Bcst
UHF-TV Bcst
HFAmateurMarine
Military
VHFLand Mobile
MicrowavePoint-to-Point
MicrowaveSatellite
1910 1920 1930 1940 1950 1960 1970 1980 1990 2000Time
February, 2005 1 - 14RF100a(c) 2005 Scott Baxter v2.0
Evolution of Wireless Telephony
Standards, Technologies, & Capacity
1960 1990
Standards EvolutionMTS150MHz IMTS150MHz
450MHz
AMPS800MHz N_AMPSD-AMPS
CDMA
PCS1900MHz GSMCDMAAMPS, etc
ESMR800MHz
System Capacity Evolution - UsersDozens Hundreds 100,000’s 1,000,000’s
Technology EvolutionAnalog AM, FM Digital Modulation
DQPSKGMSK
Access StrategiesFDMATDMACDMA
Vacuum Tubes Discrete Transistors MSI LSI VLSI, ASICs
AMPS = Advanced Mobile Phone System N_AMPS = Narrowband AMPS (Motorola)D-AMPS = Digital AMPS (IS-54 TDMA)
ESMR = Enhanced Specialized Mobile Radio
PCS-1900 = Personal Communication SystemsFDMA = Frequency Division Multiple AccessTDMA = Time Division Multiple AccessCDMA = Code Division Multiple Access
February, 2005 1 - 15RF100a(c) 2005 Scott Baxter v2.0
Trends in Radio Communications
Time
Cost per Subscriber
System Complexity
System Capacity
Radio Frequencies Used
Analog Digital
Centralized Distributed
Technology:
System Organization:
Summary: Wireless Economics and Logistics
February, 2005 2 - 1RF100 v2.0 (c) 2005 Scott Baxter
Wireless Systems:Modulation Schemes and Bandwidth
Wireless Systems:Modulation Schemes and Bandwidth
RF100 Chapter 2
fc
fc
Upper Sideband
Lower Sideband
fc
fc
I axis
Q axis
a
b
φc
QPSK
I axis
Q axis
c
a
φ
b
p
r
vπ/4 shifted DQPSK
1 0 1 0
1 0 1 0
1 0 1 0
February, 2005 2 - 2RF100 v2.0 (c) 2005 Scott Baxter
Characteristics of a Radio Signal
The purpose of telecommunications is to send information from one place to anotherOur civilization exploits the transmissible nature of radio signals, using them in a sense as our “carrier pigeons”To convey information, some characteristic of the radio signal must be altered (I.e., ‘modulated’) to represent the informationThe sender and receiver must have a consistent understanding of what the variations mean to each other
• “one if by land, two if by sea”Three commonly-used RF signal characteristics which can be varied for information transmission:
• Amplitude• Frequency• Phase
SIGNAL CHARACTERISTICS
S (t) = A cos [ ωc t + ϕ ]
The complete, time-varying radio signal
Amplitude (strength) of the signal
Natural Frequencyof the signal
Phase of the signal
Compare these Signals:
Different Amplitudes
Different Frequencies
Different Phases
February, 2005 2 - 3RF100 v2.0 (c) 2005 Scott Baxter
AM: Our First “Toehold” for Transmission
The early radio pioneers could only turn their crude transmitters on and off. They could form the dots and dashes of Morse code. Thefirst successful radio experiments happened during the mid-1890’s by experimenters in Italy, England, Kentucky, and elsewhere.By 1910, vacuum tubes gave experimenters better control over RF power generation. RF power could now be linearly modulated in step with sound vibrations. Voices and music could now be transmitted!! Still, nobody anticipated FM, PM, or digital signals. Commercial public AM broadcasting began in the early 1920’s. Despite its disadvantages and antiquity, AM is still alive:
• AM broadcasting continues today in 540-1600 KHz.• AM modulation remains the international civil aviation standard,
used by all commercial aircraft (108-132 MHz. band).• AM modulation is used for the visual portion of commercial
television signals (sound portion carried by FM modulation)• Citizens Band (“CB”) radios use AM modulation• Special variations of AM featuring single or independent
sidebands, with carrier suppressed or attenuated, are used for marine, commercial, military, and amateur communicationsSSB
LSB USB
February, 2005 2 - 4RF100 v2.0 (c) 2005 Scott Baxter
Amplitude Modulation (“AM”) DetailsTIME-DOMAIN VIEWof AM MODULATOR
x(t) = [1 + amn(t)]cos ωc twhere:
a = modulation index (0 < a <= 1)mn(t) = modulating waveform
ωc = 2π fc, the radian carrier freq.
Σa
1
+
+
x(t)
cos ωc
mn(t)
AM is “linear modulation” -- the spectrum of the baseband signal translates directly into sidebands on both sides of the carrier frequencyDespite its simplicity, AM has definite drawbacks which complicate its use for wireless systems:
• Only part of an AM signal’s energy actually carries information (sidebands); the rest is the carrier
• The two identical sidebands waste bandwidth
• AM signals can be faithfully amplified only by linear amplifiers
• AM is highly vulnerable to external noise during transmission
• AM requires a very high C/I (~30 to 40 dB); otherwise, interference is objectionable
FREQUENCY-DOMAIN VIEW
Volta
ge
Frequency0 fc
mn(t)BASEBAND
x(t)
UPPERSIDEBAND
LOWERSIDEBAND
CARRIER
February, 2005 2 - 5RF100 v2.0 (c) 2005 Scott Baxter
Circuits to Generate & Detect AM Signals
AM modulation can be simply accomplished in a saturated amplifier
• superimpose the modulating waveform on the supply voltage of the saturated amplifier
AM de-modulation (detection) can be easily performed using a simple envelope detector
• example: half-wave rectifier• this “non-coherent” detection
works well if S/N >10 dB.AM demodulation can also be performed by coherent detectors
• incoming signal is mixed (multiplied) with a locally generated carrier
• enhances performance when S/N ratio is poor (<10 dB.)
TIME-DOMAIN VIEW:AM MODULATOR
x(t)∼
∼
cos ωc
mn(t)
[1 + amn(t)]
Sat.
Lin.
TIME-DOMAIN VIEW:AM DETECTOR(non-coherent)
x(t)∼
mn(t)
information
RF carrier
Modulated signal
February, 2005 2 - 6RF100 v2.0 (c) 2005 Scott Baxter
Better Quality: Frequency Modulation (“FM”)Frequency Modulation (FM) is a type of angle modulation
• in FM, the instantaneous frequency of the signal is varied by the modulating waveform
Advantages of FM• the amplitude is constant
– simple saturated amplifiers can be used
– the signal is relatively immune to external noise
– the signal is relatively robust; required C/I values are typically 17-18 dB. in wireless applications
Disadvantages of FM• relatively complex detectors are
required• a large number of sidebands are
produced, requiring even larger bandwidth than AM
TIME-DOMAIN VIEW
sFM(t) =A cos [ωc t + mω m(x)dx+ϕ0 ]t
t0where:
A = signal amplitude (constant)ωc = radian carrier frequency
mω = frequency deviation indexm(x) = modulating signal
ϕ0 = initial phase
FREQUENCY-DOMAIN VIEW
Volta
ge
Frequency0 fc
SFM(t)UPPERSIDEBANDS
LOWERSIDEBANDS
February, 2005 2 - 7RF100 v2.0 (c) 2005 Scott Baxter
Circuits to Generate and Detect FM Signals
One way to build an FM signal is a voltage-controlled oscillator
• the modulating signal varies a reactance (varactor, etc.) or otherwise changes the frequency of the oscillator
• the modulation may be performed at a low intermediate frequency, then heterodyned to a desired communications frequency
FM de-modulation (detection) can be performed by any of several types of detectors
• Phase-locked loop (PLL)• Pulse shaper and integrator• Ratio Detector
TIME-DOMAIN VIEW:FM MODULATOR
sFM(t)m(x) ~VCO
x
LO
HPA
TIME-DOMAIN VIEW:FM DETECTOR
x
LO
LNA PLLsFM(t) m(x)
information
FM modulated signal
February, 2005 2 - 8RF100 v2.0 (c) 2005 Scott Baxter
The Inventor of FMMajor Edwin H. Armstrong was one of the most famous
inventors in the early history of radio. In 1918, he invented the superheterodyne circuit -- and implemented the basic mixing principle of heterodyne frequency conversion used in virtually all modern radio receivers. Others got the credit.
In 1933, he invented wide-band frequency modulation. Armstrong’s primary motivation was to improve the audio quality of broadcast transmission, which had suffered from noise and static because it used AM modulation.
Promotion and commercial development of FM placed Armstrong in competition with David Sarnoff and Radio Corporation of America. Sarnoff and RCA were promoting television, and worried Armstrong’s FM would compete with TV and slow its public acceptance.
Mainly due to RCA influence, the US FCC decided to change the frequencies allocated for FM broadcasting, obsoletinghundreds of FM transmitters and 500,000+ home receivers Armstrong had helped finance as an FM demonstration.
In 1954, despondent over these setbacks, Armstrong took his life. But today, the technology he started is used not only in broadcasting and the sound portion of TV, but also in land mobile and first-generation analog cellular systems.
Edwin Howard Armstrong1890 - 1954
February, 2005 2 - 9RF100 v2.0 (c) 2005 Scott Baxter
Sister of FM: Phase Modulation (“PM”)Phase Modulation (PM) is a type of anglemodulation, closely related to FM
• the instantaneous phase of the signal is varied according to the modulating waveform
Advantages of PM: very similar to FM• the amplitude is constant
– simple saturated amplifiers can be used
– the signal is relatively immune to external noise
– the signal is relatively robust; required C/I values are typically 17-18 dB. in wireless applications
Disadvantages of PM• relatively complex detectors are
required, just like FM• a large number of sidebands are
produced, just like FM, requiring even larger bandwidth than AM
TIME-DOMAIN VIEW
sPM(t) =A cos [ωc t + mω m(x) +ϕ0 ]
where:A = signal amplitude (constant)ωc = radian carrier frequencymω = phase deviation index
m(x) = modulating signalϕ0 = initial phase
FREQUENCY-DOMAIN VIEW
Volta
ge
Frequency0 fc
SFM(t)UPPERSIDEBANDS
LOWERSIDEBANDS
information
Phase-modulated signal
February, 2005 2 - 10RF100 v2.0 (c) 2005 Scott Baxter
Circuits to Generate and Detect PM SignalsPM and FM signals are identical with only one exception: in FM, the analog modulating signal is inherently de-emphasized by 1/FConsequences of this realization:
• the same types of circuitry can be used to generate and detect both analog PM or FM, determined by filtering the modulating signal at baseband
• FM has poorer signal-to-noise ratio than PM at high modulating frequencies. Therefore, pre-emphasis and de-emphasis are often used in FM systems
TIME-DOMAIN VIEW:FM DETECTOR FOR PM
x
LO
LNA PLLsFM(t) m(x)
The phase of an FM signal is proportional to the integral of the
amplitude of the modulating signal.
The phase of a PM signal is proportional to the amplitude of the modulating
signal.
TIME-DOMAIN VIEW:PHASE MODULATOR
sFM(t)m(x)
~ Phase Shifter
x
LO
HPA
information
Phase-modulated signal
February, 2005 2 - 11RF100 v2.0 (c) 2005 Scott Baxter
How Much Bandwidth do Signals Occupy?
The bandwidth occupied by a signal depends on:
• input information bandwidth• modulation method
Information to be transmitted, called “input” or “baseband”
• bandwidth usually is small, much lower than frequency of carrier
Unmodulated carrier• the carrier itself has Zero bandwidth!!
AM-modulated carrier• Notice the upper & lower sidebands• total bandwidth = 2 x baseband
FM-modulated carrier• Many sidebands! bandwidth is a
complex Bessel function• Carson’s Rule approximation 2(F+D)
PM-modulated carrier• Many sidebands! bandwidth is a
complex Bessel function
Voltage
Time
Time-Domain(as viewed on an
Oscilloscope)
Frequency-Domain(as viewed on a
Spectrum Analyzer)Voltage
Frequency0
fc
fc
Upper Sideband
Lower Sideband
fc
fc
February, 2005 2 - 12RF100 v2.0 (c) 2005 Scott Baxter
Claude Shannon: The Einstein of Information Theory
The core idea that makes CDMA possible was first explained by Claude Shannon, a Bell Labs research mathematicianShannon's work relates amount of information carried, channel bandwidth, signal-to-noise-ratio, and detection error probability
• It shows the theoretical upper limit attainable
In 1948 Claude Shannon published his landmark paper on information theory, A Mathematical Theory of Communication. He observed that "the fundamental problem of communication is that of reproducing at one point either exactly or approximately a message selected at another point." His paper so clearly established the foundations of information theory that his framework and terminology are standard today.Shannon died Feb. 24, 2001, at age 84.
SHANNON’S CAPACITY EQUATION
C = Bω log2 [ 1 + ]S N
Bω = bandwidth in HertzC = channel capacity in bits/secondS = signal powerN = noise power
February, 2005 2 - 13RF100 v2.0 (c) 2005 Scott Baxter
Digital Sampling and VocodingDigital Sampling and Vocoding
February, 2005 2 - 14RF100 v2.0 (c) 2005 Scott Baxter
Introduction to Digital Modulation
The modulating signals shown in previous slides were all analog. It is also possible to quantize modulating signals, restricting them to discrete values, and use such signals to perform digital modulation. Digital modulation has several advantages over analog modulation:Digital signals can be more easily regenerated than analog
• in analog systems, the effects of noise and distortion are cumulative: each demodulation and remodulationintroduces new noise and distortion, added to the noise and distortion from previous demodulations/remodulations.
• in digital systems, each demodulation and remodulation produces a cleanoutput signal free of past noise and distortion
Digital bit streams are ideally suited to multiplexing - carrying multiple streams of information intermixed using time-sharing
transmission
demodulation-remodulation
transmission
demodulation-remodulation
transmission
demodulation-remodulation
February, 2005 2 - 15RF100 v2.0 (c) 2005 Scott Baxter
Theory of Digital Modulation: SamplingVoice and other analog signals first must be converted to digital form (“sampled”) before they can be transmitted digitallyThe sampling theorem gives the requirements for successful sampling
• The signal must be sampled at least twice during each cycle of fM , its highest frequency. 2 x fM is called the Nyquist Rate.
• to prevent “aliasing”, the analog signal is low-pass filtered so it contains no frequencies above fM
Required Bandwidth for Samples, p(t)• If each sample p(t) is expressed as
an n-bit binary number, the bandwidth required to convey p(t) as a digital signal is at least N*2* fM
• this follows Shannon’s Theorem: at least one Hertz of bandwidth is required to convey one bit per second of data
• Notice: lots of bandwidth required!
The Sampling Theorem: Two Parts•If the signal contains no frequency higher than fM Hz., it is completely described by specifying its samples taken at instants of time spaced 1/2 fM s.•The signal can be completely recovered from its samples taken at the rate of 2 fMsamples per second or higher.
m(t)
Sampling
Recoverym(t)
p(t)
February, 2005 2 - 16RF100 v2.0 (c) 2005 Scott Baxter
The Mother of All Telephone Signals: DS-0
Telephony has adopted a world-wide PCM standard digital signal, using a 64 kb/s stream derived from sampled voice dataVoice waveforms are band-limited (see curve)
• upper cutoff beyond 3500-4000 Hz. to avoid aliasing
• rolloff below 300 Hz. For less sensitivity to “hum” picked up from AC power mains
Voice waveforms sampled 8000 times/second• A>D conversion has 1 byte (8 bit)
resolution; thus 256 voltage levels possible • 8000 samples x 1 byte = 64,000 bits/second• Levels are defined logarithmically rather
than linearly, to handle a wider range of audio levels with minimum distortion
– µ-law companding is used in North America & Japan
– A-law companding is used in most other countries
-10dB
-20dB
-30dB
-40dB
0 dB
100 300 1000 3000 10000Frequency, Hz
C-Message Weighting
t
012345687910111213141516
4
16
13
15
8
3 48
A-LAWy= sgn(x) A|x|
ln(1+ A) for 0 ≤ x≤ 1A
(where A = 87.6)
y= sgn(x) ln(1+ A|x)|ln(1+ A) for 1
A < x ≤1
µ-Lawy = sgn(x) ln(1+ µ|x|)
ln(1 + µ)(whereµ = 255)
Companding
Band-Limiting
x = analog audio voltagey = quantized level (digital)
February, 2005 2 - 17RF100 v2.0 (c) 2005 Scott Baxter
Was Digital Supposed to Give More Capacity!?
A DS-0 telephone signal, carrying one person talking, is a 64,000 bits/second data stream.Shannon’s theorem tells us we’ll need at least 64,000 Hz. of bandwidth to carry this signal, even with the most advanced modulation techniques (QPSK, etc.)But regular analog cellular signals are only 30,000 Hz. wide! So does a digital signal require more bandwidth than analog?!!YES -- unless we do something fancy, like compression.We DO use compression, to reduce the number of bits being transmitted, thereby keeping the bandwidth as small as we canThe compressing device is called a Vocoder (voice coder). It both compresses the signal being sent, and expands the signal being receivedEvery digital mobile phone technology uses some type of Vocoder
• There are many types, with many different characteristics
February, 2005 2 - 18RF100 v2.0 (c) 2005 Scott Baxter
Vocoders: Compression vs. Distortion
Objective: to significantly reduce the number of bits which must be transmitted, but without creating objectionable levels of distortionWe are concerned mainly with telephone applications, with voice signal already band-limited to 4 kHz. max. and sampled at 8 kHz.The objective is toll-quality voice reproductionGeneral Categories of Speech Coders
• Waveform Coders– attempt to re-create the input waveform– good speech quality but at relatively high bit rates
• Vocoders– attempt to re-create the sound as perceived by humans– quantize and mimic speech-parameter-defined properties– lower bit rates but at some penalty in speech quality
• Hybrid Coders– mixed approach, using elements of Waveform Coders &
Vocoders– use vector quantization against a codebook reference– low bit rates and good quality speech
February, 2005 2 - 19RF100 v2.0 (c) 2005 Scott Baxter
Meet some Families of Speech Coders
Waveform Coders
PCM (pulse-code modulation), APCM (adaptive PCM)DPCM (differential PCM), ADPCM (adaptive DPCM)DM (delta modulation), ADM (adaptive DM)CVSD (continuously variable-slope DM)APC (adaptive predictive coding)RELP (residual-excited linear prediction)SBC (subband coding)ATC (adaptive transform coding)
Hybrid CodersMPLP (multipulse-excited linear prediction)RPE (regular pulse-excited linear prediction)VSELP (vector-sum excited linear prediction)CELP (code-excited linear prediction)
VocodersChannel, Formant, Phase, Cepstral, or HomomorphicLPC (linear predictive coding)STC (sinusoidal transform coding)MBE (multiband excitation), IMBE (improved MBE)
Objective: to significantly reduce the number of bits which must be transmitted, but without creating objectionable levels of distortionWe are concerned mainly with telephone applications, with voice signal already band-limited to 4 kHz. max. and sampled at 8 kHz.The objective is toll-quality voice reproductionA few different strategies and algorithms used in voice compression:
February, 2005 2 - 20RF100 v2.0 (c) 2005 Scott Baxter
Speech Coders Used Mobile Technologies:Vocoders are usually described by their output rate (8 kilobits/sec, etc.) and the type of algorithm they use. Here’s a list of the vocoders used in currently popular wireless technologies:
bits/sec64k32k32k16k
13/7/4/2 v13k9.6k
8k6.7k6.4k
8/4/2/1 v8/4/2/1 v
4.8k2.4k
Algorithmlog PCMADPCM
LD-CELPAPC
QCELPRPE-LTP
MPLP
VSELPVSELPIMBE
QCELPQCELPCELP
LPC-10
Standard (Year)CCITT G.711 (1972)CCITT G.721 (1984)CCITT G.728 (1992)Inmarsat-B (1985)CTIA, IS-54/J-Std008 (1995) CDMAPan-European DMR, GSM (1991)BTI Skyphone (1990)
CTIA IS-54 (1993) TDMAJapanese DMR (1993)Inmarsat-M (1993)Enhanced Vocoder, 1997 CDMACTIA, IS-95 (1993) CDMAUS, FS-1016 (1991)US, FS-1015 (1977)
MOS4.34.14.0
n/availn/avail
3.53.4
3.53.43.4
n/avail3.43.22.3
8k EFRC IS-136 (1997) TDMA enhanced n/avail
February, 2005 2 - 21RF100 v2.0 (c) 2005 Scott Baxter
The Latest Vocoder Technology, 2005
CDMA Family:• SMV (selective multirate vocoder)
ETSI GSM/WCDMA Family• AMR (adaptive multirate vocoder)
February, 2005 2 - 22RF100 v2.0 (c) 2005 Scott Baxter
Digital ModulationDigital Modulation
February, 2005 2 - 23RF100 v2.0 (c) 2005 Scott Baxter
Modulation by Digital Inputs
For example, modulate a signal with this digital waveform. No more continuous analog variations, now we’re “shifting”between discrete levels. We call this “shift keying”.
• The user gets to decide what levels mean “0” and “1” -- there are no inherent values
Steady Carrier without modulationAmplitude Shift Keying
ASK applications: digital microwaveFrequency Shift Keying
FSK applications: control messages in AMPS cellular; TDMA cellular
Phase Shift KeyingPSK applications: TDMA cellular,
GSM & PCS-1900
Our previous modulation examples used continuously-variable analog inputs. If we quantize the inputs, restricting them to digital values, we will produce digital modulation.
Voltage
Time1 0 1 0
1 0 1 0
1 0 1 0
1 0 1 0
February, 2005 2 - 24RF100 v2.0 (c) 2005 Scott Baxter
Digital Modulation SchemesThere are many different schemes for digital modulation, each a compromise between complexity, immunity to errors in transmission, required channel bandwidth, and possible requirement for linear amplifiersLinear Modulation Techniques
• BPSK Binary Phase Shift Keying• DPSK Differential Phase Shift Keying• QPSK Quadrature Phase Shift Keying IS-95 CDMA forward link
– Offset QPSK IS-95 CDMA reverse link– Pi/4 DQPSK IS-54, IS-136 control and traffic channels
Constant Envelope Modulation Schemes• BFSK Binary Frequency Shift Keying AMPS control channels• MSK Minimum Shift Keying• GMSK Gaussian Minimum Shift Keying GSM systems, CDPD
Hybrid Combinations of Linear and Constant Envelope Modulation• MPSK M-ary Phase Shift Keying• QAM M-ary Quadrature Amplitude Modulation• MFSK M-ary Frequency Shift Keying FLEX paging protocol
Spread Spectrum Multiple Access Techniques• DSSS Direct-Sequence Spread Spectrum IS-95 CDMA• FHSS Frequency-Hopping Spread Spectrum
February, 2005 2 - 25RF100 v2.0 (c) 2005 Scott Baxter
Modulation used in CDMA Systems
CDMA mobiles use offset QPSK modulation
• the Q-sequence is delayed half a chip, so that I and Q never change simultaneously and the mobile TX never passes through (0,0)
CDMA base stations use QPSK modulation
• every signal (voice, pilot, sync, paging) has its own amplitude, so the transmitter is unavoidably going through (0,0) sometimes; no reason to include 1/2 chip delay
Base Stations: QPSKQ Axis
I Axis
ShortPN Q
Σ
cos ωt
sin ωt
User’schips
ShortPN I
Mobiles: OQPSKQ Axis
I Axis
ShortPN Q
Σ
cos ωt
sin ωt
User’schips
1/2 chip
ShortPN I
February, 2005 2 - 26RF100 v2.0 (c) 2005 Scott Baxter
CDMA Base Station Modulation Views
The view at top right shows the actual measured QPSK phase constellation of a CDMA base station in normal serviceThe view at bottom right shows the measured power in the code domain for each walsh code on a CDMA BTS in actual service
• Notice that not all walsh codes are active
• Pilot, Sync, Paging, and certain traffic channels are in use
February, 2005 3 - 1RF100 v2.0 (c) 2005 Scott Baxter
Wireless Systems:Multiple Access Technologies & Standards
Wireless Systems:Multiple Access Technologies & Standards
Chapter 3
February, 2005 3 - 2RF100 v2.0 (c) 2005 Scott Baxter
Multiple Access Technologies
FDMA (example: AMPS)Frequency Division Multiple Access• each user has a private frequency (at
least in their own neighborhood)
TDMA (examples: IS-54/136, GSM)Time Division Multiple Access• each user has a private time on a private
frequency (at least in their own neighborhood)
CDMA (examples: IS-95, J-Std. 008)Code Division Multiple Access• users co-mingle in time and frequency
but each user has a private code (at least in their own neighborhood)
FrequencyTime
Power
FrequencyTime
Power
FrequencyTime
Power
FDMA
TDMA
CDMA
February, 2005 3 - 3RF100 v2.0 (c) 2005 Scott Baxter
Conventional Technologies:Recovering the Signal / Avoiding Interference
In ordinary radio technologies, the desired signal must be stronger than all interference by at least a certain margin called C/I (carrier-to-interference ratio)
• the type of signal modulation determines the amount of interference which can be tolerated, and thus the required C/I
In conventional systems, the C/I is controlled mainly by the distance between co-channel cells
• frequency usage is planned so that co-channel users don’t have interference worse than C/I
• any undesired interference we face is coming from the nearest co-channel cells, far away
• if the signal is delicate, then we need a big C/I and the co-channel cells must be very far away
• if the signal is more rugged, we can tolerate more interference (smaller C/I) allowing the co-channel cells a bit closer without bad effects
2
3
4
5 6
7
4
6
47 2
7
2
5
35
36
1
1
1
1
1
1
1
AMPS-TDMA-GSM
Figure of Merit: C/I(carrier/interference ratio)
AMPS: +17 dBTDMA: +14 to 17 dB
GSM: +7 to 9 dB.
February, 2005 3 - 4RF100 v2.0 (c) 2005 Scott Baxter
Handoffs and C/I
One purpose of handoff is to keep the call from dropping as the mobile moves out of range of individual cellsAnother purpose of handoff is to ensure the mobile is using the cell with the best signal strength and best C/I at all timesNotice in the signal graphs at lower right how the mobile’s C/I is maintained at a usable level as it goes from cell to cell
A B
RSSI, dBm
-120
-50
C DSites
C/I
AB
CD
AMPS
Tech-nology
NAMPSTDMAGSM
CDMA
Analog FM
ModulationType
Analog FMDPQSKGMSK
QPSK/OQPSK
30 kHz.
Channel Bandwidth
10 kHz.30 kHz.
200 kHz.1,250 kHz.
C/I ≅ 17 dB
Quality Indicator
C/I ≅ 17 dBC/I ≅ 17 dBC/I ≅ 17 dBEb/No ≅ 6dB
February, 2005 3 - 5RF100 v2.0 (c) 2005 Scott Baxter
CDMA: Using A New Dimension
All CDMA users occupy the same frequency at the same time! Frequency and time are not used as discriminatorsCDMA operates by using a new dimension, CODING, to discriminate between users
• In CDMA, we do not try to immediately recover the pulses of energy from each user. Instead, we watch long groups of the totals of everybody’s pulses, and detect little patterns which are the “signature” of the user we wish to decode
In CDMA, the interference originates mainly from nearby users in the same general areaEach user is a small voice in a roaring crowd -- but with a uniquely recoverable code
CDMA
Figure of Merit: C/IAMPS: +17 dB
TDMA: +14 to +17 dBGSM: +7 to 9 dB.
CDMA: -10 to -17 dB.Although the CDMA C/I is negative, the decoding process recovers the user’s energy while discarding others’energy. The final net result is Eb/No, typically about +6 db.We’ll study this in detail later.
February, 2005 3 - 6RF100 v2.0 (c) 2005 Scott Baxter
The CDMA Migration Path to 3G
1xEV-DORev. A
IS-856
1250 kHz.59 active
users
Higher data rates on data-
only CDMA carrier
3.1 Mb/sDL
1.8 Mb/sUL
RL FLSpectrum
1xEV-DORev. 0IS-856
1250 kHz.59 active
users
High data rates on data-only
CDMA carrier
2.4 Mb/sDL
153 Kb/sUL
CDMAone CDMA2000 / IS-2000
Technology
Generation
SignalBandwidth,
#Users
Features:Incremental
Progress
1G
AMPS
DataCapabilities
30 kHz.1
First System,Capacity
&Handoffs
None,2.4K by modem
2G
IS-95A/J-Std008
1250 kHz.20-35
First CDMA,
Capacity,Quality
14.4K
2G
IS-95B
1250 kHz.25-40
•Improved Access•Smarter Handoffs
64K
2.5G? 3G
IS-2000:1xRTT
1250 kHz.50-80 voice
and data
•Enhanced Access
•Channel Structure
153K307K230K
3G
1xEV-DV1xTreme
1250 kHz.Many packet
users
High data rates on
Data-Voice shared CDMA carrier
5 Mb/s
3G
IS-2000:3xRTT
F: 3x 1250kR: 3687k
120-210 per 3 carriers
Faster data rates on shared 3-carrier bundle
1.0 Mb/s
RL FLRL FLRL FLRL FLRL FLRL FLRL FL
February, 2005 3 - 7RF100 v2.0 (c) 2005 Scott Baxter
Modulation Techniques of 1xEV Technologies
1xEV, “1x Evolution”, is a family of alternative fast-data schemes that can be implemented on a 1x CDMA carrier.1xEV DO means “1x Evolution, Data Only”, originally proposed by Qualcomm as “High Data Rates” (HDR).
• Up to 2.4576 Mbps forward, 153.6 kbps reverse
• A 1xEV DO carrier holds only packet data, and does not support circuit-switched voice
• Commercially available in 20031xEV DV means “1x Evolution, Data and Voice”.
• Max throughput of 5 Mbps forward, 307.2k reverse
• Backward compatible with IS-95/1xRTT voice calls on the same carrier as the data
• Not yet commercially available; work continues
All versions of 1xEV use advanced modulation techniques to achieve high throughputs.
QPSKCDMA IS-95,
IS-2000 1xRTT,and lower ratesof 1xEV-DO, DV
16QAM1xEV-DOat highest
rates
64QAM1xEV-DVat highest
rates
February, 2005 3 - 8RF100 v2.0 (c) 2005 Scott Baxter
GSM Technology Migration Path to 3G
Integrated voice/data(Future rates to 12 MBPS using adv.
modulation?)
Technology
Generation
SignalBandwidth,
#Users
Features:Incremental
Progress
1G
variousanalog
DataCapabilities
various
various
various
2G
GSM
200 kHz.7.5 avg.
Europe’sfirst Digitalwireless
none
2.5G or 3?
GPRS
200 kHz.Many
Pkt. users
•Packet IP access
•Multiple attached
users
9-160 Kb/s(conditionsdetermine)
3G
EDGE
200 kHz.fast data
many users
8PSK for 3x Faster data rates
than GPRS
384 Kb/smobile user
3GUMTSUTRA
WCDMA3.84 MHz.up to 200+voice users
and data
2Mb/sstatic user
February, 2005 3 - 9RF100 v2.0 (c) 2005 Scott Baxter
TDMA IS-136 Technology Migration Path to 3G
2G
CDPD
30 kHz.Many
Pkt Usrs
19.2kbps
US PacketDataSvc.
Technology
Generation
SignalBandwidth,
#Users
Features:Incremental
Progress
DataCapabilities
2GTDMAIS-54
IS-136
30 kHz.3 users
USA’sfirst
Digitalwireless
none
2.5G or 3?
GPRS
200 kHz.Many
Pkt. users
•Packet IP access
•Multiple attached
users
9-160 Kb/s(conditionsdetermine)
3G
EDGE
200 kHz.fast data
many users
8PSK for 3x Faster data rates
than GPRS
384 Kb/smobile user
3GUMTSUTRA
WCDMA3.84 MHz.up to 200+voice users
and data
Integrated voice/data(Future rates to 12 MBPS using adv.
modulation?)
1G
AMPS
30 kHz.1
First System,Capacity
&Handoffs
None,2.4K by modem
2Mb/sstatic user
2G
GSM
200 kHz.7.5 avg.
Europe’sfirst
Digitalwireless
none
the familiar GSM path!
February, 2005 3 - 10RF100 v2.0 (c) 2005 Scott Baxter
Not BWA; for comparison only
802.16
BPSK to256QAMOFDM
54 Mb/s
TDD, FDDvarious
2-11 GHz10-66 GHz
802.20Mobile BWA
4G: Broadband Wireless Access Technologies
Technology
ModulationType
Max RawData Rate
AccessMethod
FrequencyBand
InfraredIRDA
various
4 Mb/s
Single User perOptical Carrier
Optical
802.11b
CCK
11 Mb/s
DSSS
2.4 GHz
802.11a
BPSK, QPSK,16QAM, or
64QAM
54 Mb/s
DSSS
5 GHz
HIPERLANType 1
FSK orGMSK
23.5 Mb/s
OFDM
5 GHz
HIPERLANType 2
BPSK, QPSK,16QAM, or
64QAM
54 Mb/s
various.
5 GHz
Bluetooth
GFSKFH
1 Mb/s
various
2.4 GHz
BLUETOOTH
802.11A, B, WIFI, WILAN
Infrared IRDA
High Hopes!
February, 2005 3 - 11RF100 v2.0 (c) 2005 Scott Baxter
Hig
h-Ti
er $
$$Lo
w-T
ier $
1G: AMPS
4G – Evolution or Revolution?
There’s a revolution going on!• New 2.5G services arriving now, new 3G arriving 2002 through 2005• A groundswell of commercial (and even free!) WILAN deployment
3G networks and 4G networks have their own unique advantagesUltimately 3G and 4G will be integrated by wireless operators!
Technology Environment Service Provider/Infrastructure Owner
PSTN IP/VPNs
2G: TDMA, GSM, IS95 CDMA, IDEN
2.5G: GPRS, EDGE3G: IS2000 1xRTT, 1xEV DO, 1xEV DVUMTS WCDMA4G: Wireless LAN802.11b “Wi-Fi”802.11a, gHIPERLAN Type 1HIPERLAN Type 2BluetoothInfrared freenetworks.org
Near-Universal Macro-Coverage
Hotspots
February, 2005 3 - 12RF100 v2.0 (c) 2005 Scott Baxter
Global and US Wireless Snapshot 4Q 2003
Total Worldwide Wireless customers surpassed total worldwide landline customers at year-end 2002, with 1,00,080,000 of each.2/3 of worldwide wireless customers use the GSM technologyCDMA is second-most-prevalent with 17.0%In the US, CDMA is the most prevalent technology at 45.7%Both CDMA and GSM are growing in the US
• most IS-136 TDMA systems are converting to GSM + GPRS + EDGE
Worldwide USATotal Wireless Users
GSM usersCDMA usersTDMA usersIDEN users
Analog users
1,320,000,000 100%870,000,000 65.9%224,000,000 17.0%124,000,000 9.4%68,000,000 5.2%34,000,000 2.6%
141,000,000 100%33,732,506 23.9%64,503,287 45.7%26,375,232 18.6%11,978,382 8.5%4,510,594 3.2%
February, 2005 3 - 13RF100 v2.0 (c) 2005 Scott Baxter
Other Misc.
A Quick Survey of Wireless Data Technologies
This summary is a work-in-progress, tracking latest experiences and reports from all the high-tier (provider-network-oriented) 2G and 3G wireless data technologiesHave actual experiences to share, latest announced details, or corrections to the above? Email to [email protected]. Thanks for your comments!
PAGINGETSI / GSMUS CDMA
IS-136
ANALOGAMPS Cellular
9.6 – 4.8 kb/sw/modem
IS-136 TDMA19.2 – 9.6 kb/s
GSM CSD9.6 – 4.8 kb/s
GSM HSCSD32 – 19.2 kb/s
IDEN19.2 – 19.2 kb/s
IS-9514.4 – 9.6 kb/s
IS-95B64 -32 kb/s
CDPD19.2 – 4.8 kb/sdiscontinued
GPRS40 – 30 kb/s DL
15 kb/s UL
EDGE200 - 90 kb/s DL
45 kb/s UL
1xRTT RC3153.6 – 80 kb/s
1xRTT RC4307.2 – 160 kb/s
1xEV-DO2400 – 600 DL153.6 – 76 UL
1xEV-DO A3100 – 800 DL1800 – 600 UL
1xEV-DV5000 - 1200 DL307 - 153 UL
WCDMA 0384 – 250 kb/s
WCDMA 12000 - 800 kb/s
WCDMA HSPDA12000 – 6000 kb/s
Flarion OFDM1500 – 900 kb/s
TD-SCDMAIn Development
Mobitex9.6 – 4.8 kb/s
obsolete
February, 2005 3 - 14RF100 v2.0 (c) 2005 Scott Baxter
Wireless System CapacityEach wireless technology (AMPS,
NAMPS, D-AMPS, GSM, CDMA) uses a specific modulation type with its own unique signal characteristicsSignal Bandwidth determines how many RF signals will “fit” in the operator’s licensed spectrumRobustness of RF signal determines tolerable level of interference and necessary physical separation of cochannelcellsNumber of users per RF signal directly affects capacityIn the following page, we will develop the number of users and traffic in erlangs per site for each of the popular wireless technologies
AMPS, D-AMPS, N-AMPS
CDMA
30 30 10 kHz Bandwidth
200 kHz
1250 kHz
1 3 1 Users
8 Users
22 Users1
1
11
11
11
111
111
1 23
4
43
2
56 17
Typical Frequency Reuse N=7
Typical Frequency Reuse N=4
Typical Frequency Reuse N=1
Vulnerability:C/I ≅ 17 dB
Vulnerability:C/I ≅ 6.5-9 dB
Vulnerability:EbNo ≅ 6 dB
February, 2005 3 - 15RF100 v2.0 (c) 2005 Scott Baxter
Comparison of Wireless System Capacities
Fwd/Rev Spectrum kHz. 12,500 12,500 12,500 15,000 15,000 15,000 5,000 5,000 5,000 Technology AMPS TDMA CDMA TDMA GSM CDMA TDMA GSM CDMAReq'd C/I or Eb/No, db 17 17 6 17 12 6 17 12 6Freq Reuse Factor, N 7 7 1 7 4 1 7 4 1RF Signal BW, kHz 30 30 1250 30 200 1250 30 200 1250Total # RF Carriers 416 416 9 500 75 11 166 25 3RF Sigs. per cell @N 59 59 9 71 18 11 23 6 3# Sectors per cell 3 3 3 3 3 3 3 3 3#CCH per sector 1 1 0 1 0 0 1 0 0RF Signals per sector 18 18 9 22 6 11 6 2 3Voicepaths/RF signal 1 3 22 3 8 22 3 8 22SH average links used 1 1 1.66 1 1 1.66 1 1 1.66Unique Voicepaths/carrier 1 3 13.253 3 8 13.253 3 8 13.253Voicepaths/Sector 18 54 198 66 48 242 18 16 66Unique Voicepaths/Sector 18 54 119 66 48 145 18 16 39P.02 Erlangs per sector 11.5 44 105.5 55.3 38.4 130.9 11.5 9.83 30.1P.02 Erlangs per site 34.5 132 316.5 165.9 115.2 392.7 34.5 29.49 90.3Capacity vs. AMPS800 1 3.8 9.2 4.8 3.3 11.4 1.0 0.9 2.6
800 Cellular (A,B) 1900 PCS (A, B, C) 1900 PCS (D, E, F)
February, 2005 3 - 16RF100 v2.0 (c) 2005 Scott Baxter
Capacity of Multicarrier CDMA Systems
Fwd/Rev Spectrum kHz. 12,500 1,800 3,050 4,300 5,550 6,800 8,050 9,300 10,550 11,800 13,050 14,300 Technology AMPS CDMA CDMA CDMA CDMA CDMA CDMA CDMA CDMA CDMA CDMA CDMA
Req'd C/I or Eb/No, db 17 6 6 6 6 6 6 6 6 6 6 6Freq Reuse Factor, N 7 1 1 1 1 1 1 1 1 1 1 1
RF Signal BW, kHz 30 1250 1250 1250 1250 1250 1250 1250 1250 1250 1250 1250Total # RF Carriers 416 1 2 3 4 5 6 7 8 9 10 11
RF Sigs. per cell @N 59 1 2 3 4 5 6 7 8 9 10 11# Sectors per cell 3 3 3 3 3 3 3 3 3 3 3 3#CCH per sector 1 0 0 0 0 0 0 0 0 0 0 0
RF Signals per sector 18 1 2 3 4 5 6 7 8 9 10 11Voicepaths/RF signal 1 22 22 22 22 22 22 22 22 22 22 22
SH average links used 1 1.66 1.66 1.66 1.66 1.66 1.66 1.66 1.66 1.66 1.66 1.66Unique Voicepaths/carrier 1 13.3 13.3 13.3 13.3 13.3 13.3 13.3 13.3 13.3 13.3 13.3
Voicepaths/Sector 18 22 44 66 88 110 132 154 176 198 220 242Unique Voicepaths/Sector 18 13 26 39 53 66 79 92 106 119 132 145
P.02 Erlangs per sector 11.5 7.4 18.4 30.1 43.1 55.3 67.7 80.2 93.8 105.5 119.1 130.9P.02 Erlangs per site 34.5 22.2 55.2 90.3 129.3 165.9 203.1 240.6 281.4 316.5 357.3 392.7
Capacity vs. AMPS800 1 0.64 1.60 2.6 3.7 4.8 5.9 7.0 8.2 9.2 10.4 11.4
f
1 2 3 4 5 6 7 8 9 1011
CDMA Carrier Frequencies
February, 2005 4 - 1RF100 v2.0 (c) 2005 Scott Baxter
Physical Principles of Propagation
Physical Principles of Propagation
Chapter 4 Section A
February, 2005 4 - 2RF100 v2.0 (c) 2005 Scott Baxter
Introduction to Propagation
Propagation is the heart of every radio link. During propagation, many processes act on the radio signal.
• attenuation– the signal amplitude is reduced by various natural mechanisms. If there
is too much attenuation, the signal will fall below the reliable detection threshold at the receiver. Attenuation is the most important single factor in propagation.
• multipath and group delay distortions– the signal diffracts and reflects off irregularly shaped objects, producing a
host of components which arrive in random timings and random RF phases at the receiver. This blurs pulses and also produces intermittent signal cancellation and reinforcement. These effects are overcome through a variety of special techniques
• time variability - signal strength and quality varies with time, often dramatically• space variability - signal strength and quality varies with location and distance• frequency variability - signal strength and quality differs on different
frequenciesTo master propagation and effectively design wireless systems, you must know:
• Physics: understand the basic propagation processes • Measurement: obtain data on propagation behavior in area of interest• Statistics: analyze known data, extrapolate to predict the unknown• Modelmaking: formalize all the above into useful models
February, 2005 4 - 3RF100 v2.0 (c) 2005 Scott Baxter
Frequency and Wavelength: Implications
Radio signals in the atmosphere propagate at almost speed of light
λ = wavelengthC = distance propagated in 1 secondF = frequency, Hertz
The wavelength of a radio signal determines many of its propagation characteristics
• Antenna elements size are typically in the order of 1/4 to 1/2 wavelength
• Objects bigger than a wavelength can reflect or obstruct RF energy
• RF energy can penetrate into a building or vehicle if they have apertures a wavelength in size, or larger
λ/2
λ = C / Ffor AMPS: F= 870 MHz
λ = 0.345 m = 13.6 inches
for PCS-1900: F = 1960 MHzλ = 0.153 m = 6.0 inches
February, 2005 4 - 4RF100 v2.0 (c) 2005 Scott Baxter
Propagation Effects of Earth’s Atmosphere
Earth’s unique atmosphere supports life (ours included) and also introduces many propagation effects -- some useful, some troublesomeSkywave Propagation: reflection from Ionized Layers
• LF and HF frequencies (below roughly 50 MHz.) are routinely reflected off layers of the upper atmosphere which become ionized by the sun
• this phenomena produces intermittent world-wide propagation and occasional total outages
• this phenomena is strongly correlated with frequency, day/night cycles, variations in earth’s magnetic field, 11-year sunspot cycle
• these effects are negligible for wireless systems at their much-higher frequencies
February, 2005 4 - 5RF100 v2.0 (c) 2005 Scott Baxter
More Atmospheric Propagation Effects
Attenuation at Microwave Frequencies• rain droplets can substantially attenuate RF
signals whose wavelengths are comparable to, or smaller than, droplet size
• rain attenuations of 20 dB. or more per km. are possible
• troublesome mainly above 10 GHz., and in tropical areas
• must be considered in reliability calculations during path design
• not major factor in wireless systems propagationDiffraction, Wave Bending, Ducting
• signals 50-2000 MHz. can be bent or reflected at boundaries of different air density or humidity
• phenomena: very sporadic unexpected long-distance propagation beyond the horizon. May last minutes or hours
• can occur in wireless systems
Refraction by air layers
Ducting by air layers
>100 mi.
“Rain Fades” onMIcrowave Links
February, 2005 4 - 6RF100 v2.0 (c) 2005 Scott Baxter
Dominant Mechanisms of Mobile PropagationMost propagation in the mobile
environment is dominated by these three mechanisms:Free space
• No reflections, no obstructions– first Fresnel Zone clear
• Signal spreading is only mechanism• Signal decays 20 dB/decade
Reflection• Reflected wave 180°out of phase• Reflected wave not attenuated much• Signal decays 30-40 dB/decade
Knife-edge diffraction• Direct path is blocked by obstruction• Additional loss is introduced• Formulae available for simple cases
We’ll explore each of these further...
Knife-edge Diffraction
Reflection with partial cancellation
BA
d
D
Free Space
February, 2005 4 - 7RF100 v2.0 (c) 2005 Scott Baxter
Free-Space PropagationThe simplest propagation mode• Antenna radiates energy which spreads in space• Path Loss, db (between two isotropic antennas)
= 36.58 +20*Log10(FMHZ)+20Log10(DistMILES )• Path Loss, db (between two dipole antennas)
= 32.26 +20*Log10(FMHZ)+20Log10(DistMILES )• Notice the rate of signal decay:• 6 db per octave of distance change, which is
20 db per decade of distance changeFree-Space propagation is applicable if:• there is only one signal path (no reflections)• the path is unobstructed (i.e., first Fresnel zone
is not penetrated by obstacles)
First Fresnel Zone =Points P where AP + PB - AB < λ/2 Fresnel Zone radius d = 1/2 (λD)^(1/2)
1st Fresnel Zone
BA
d
D
Free Space “Spreading” Lossenergy intercepted by receiving antenna is proportional to 1/r2
r
February, 2005 4 - 8RF100 v2.0 (c) 2005 Scott Baxter
Reflection With Partial Cancellation
Mobile environment characteristics:• Small angles of incidence and reflection• Reflection is unattenuated (reflection coefficient =1)• Reflection causes phase shift of 180 degrees
Analysis• Physics of the reflection cancellation predicts signal
decay of 40 dB per decade of distance
Heights Exaggerated for Clarity
HTFT
HTFT
DMILES
Comparison of Free-Space and Reflection Propagation ModesAssumptions: Flat earth, TX ERP = 50 dBm, @ 1950 MHz. Base Ht = 200 ft, Mobile Ht = 5 ft.
Received Signal in Free Space, DBMReceived Signal inReflection Mode
DistanceMILES
-52.4-69.0
1-58.4-79.2
2-64.4-89.5
4-67.9-95.4
6-70.4-99.7
8-72.4-103.0
10-75.9-109.0
15-78.4-113.2
20
Path Loss [dB ]= 172 + 34 x Log (DMiles )- 20 x Log (Base Ant. HtFeet)
- 10 x Log (Mobile Ant. HtFeet)
SCALE PERSPECTIVE
February, 2005 4 - 9RF100 v2.0 (c) 2005 Scott Baxter
Signal Decay Rates in Various Environments
We’ve seen how the signal decays with distance in two basic modes of propagation:Free-Space
• 20 dB per decade of distance• 6 db per octave of distance
Reflection Cancellation• 40 dB per decade of distance• 12 db per octave of distance
Real-life wireless propagation decay rates are typically somewhere between 30 and 40 dB per decade of distance
Signal Level vs. Distance
-40
-30
-20
-10
0
Distance, Miles1 3.16 102 5 7 86
One Octaveof distance (2x)
One Decadeof distance (10x)
February, 2005 4 - 10RF100 v2.0 (c) 2005 Scott Baxter
Knife-Edge DiffractionSometimes a single well-defined obstruction blocks the path, introducing additional loss. This calculation is fairly easy and can be used as a manual tool to estimate the effects of individual obstructions.First calculate the diffraction parameter ν from the geometry of the pathNext consult the table to obtain the obstruction loss in dbAdd this loss to the otherwise-determined path loss to obtain the total path loss.Other losses such as free space and reflection cancellation still apply, but computed independently for the path as if the obstruction did not exist
H
R1 R2
ν
attendB
0-5
-10-15-20-25
-4 -3 -2 -1 0 1 2 3-5
( + )ν = -H2λ
1 1R1 R2
February, 2005 4 - 11RF100 v2.0 (c) 2005 Scott Baxter
Local Variability: Multipath Effects
The free-space, reflection, and diffraction mechanisms described earlier explain signal level variations on a large scale, but other mechanisms introduce small-scale local fadingSlow Fading occurs as the user moves over hundreds of wavelengths due to shadowing by local obstructionsRapid Fading occurs as signals received from many paths drift into and out of phase
• the fades are roughly λ/2 apart in space:7 inches apart at 800 MHz., 3 inches
apart at 1900 MHz• fades also appear in the frequency
domain and time domain• fades are typically 10-15 db deep,
occasionally deeper• Rayleigh distribution is a good model
for these fadesthese fades are often called “Rayleigh fades”
Multi-path Propagation
A
d
10-15 dBλ/2
Rayleigh Fading
February, 2005 4 - 12RF100 v2.0 (c) 2005 Scott Baxter
Combating Rayleigh Fading: Space Diversity
Fortunately, Rayleigh fades are very short and last a small percentage of the timeTwo antennas separated by several wavelengths will not generally experience fades at the same time“Space Diversity” can be obtained by using two receiving antennas and switching instant-by-instant to whichever is bestRequired separation D for good decorrelation is 10-20λ
• 12-24 ft. @ 800 MHz.• 5-10 ft. @ 1900 MHz.
Signal received by Antenna 1
Signal received by Antenna 2
Combined Signal
D
February, 2005 4 - 13RF100 v2.0 (c) 2005 Scott Baxter
Space Diversity Application Limitations
Space Diversity can be applied only on the receiving end of a link. Transmitting on two antennas would:
• fail to produce diversity, since the two signals combine to produce only one value of signal level at a given point -- no diversity results.
• produce objectionable nulls in the radiation at some angles
Therefore, space diversity is applied only on the “uplink”, i.e.., reverse path
• there isn’t room for two sufficiently separated antennas on a mobile or handheld
Signal received by Antenna 1
Signal received by Antenna 2
Combined Signal
D
February, 2005 4 - 14RF100 v2.0 (c) 2005 Scott Baxter
Using Polarization DiversityWhere Space Diversity Isn’t Convenient
Sometimes zoning considerations or aesthetics preclude using separate diversity receive antennas Dual-polarized antenna pairs within a single radome are becoming popular
• Environmental clutter scatters RF energy into all possible polarizations
• Differently polarized antennas receive signals which fade independently
• In urban environments, this is almost as good as separate space diversity
Antenna pair within one radome can be V-H polarized, or diagonally polarized
• Each individual array has its own independent feedline
• Feedlines connected to BTS diversity inputs in the conventional way; TX duplexing OK
Antenna AAntenna BCombined
A B A B
V+Hor\+/
February, 2005 4 - 15RF100 v2.0 (c) 2005 Scott Baxter
The Reciprocity PrincipleDoes it apply to Wireless?
Between two antennas, on the same exact frequency, path loss is the same in both directionsBut things aren’t exactly the same in cellular --
• transmit and receive 45 MHz. apart• antenna: gain/frequency slope?• different Rayleigh fades
up/downlink• often, different TX & RX antennas• RX diversity
Notice also the noise/interference environment may be substantially different at the two endsSo, reciprocity holds only in a general sense for cellular
-148.21 db@ 835.03 MHz
-151.86 db@ 870.03 MHz
-148.21 db@ 870.03 MHz
February, 2005 4 - 16RF100 v2.0 (c) 2005 Scott Baxter
Propagation ModelsPropagation Models
Chapter 4 Section B
February, 2005 4 - 17RF100 v2.0 (c) 2005 Scott Baxter
Types Of Propagation Models And Their Uses
Simple Analytical models • Used for understanding and
predicting individual paths and specific obstruction cases
General Area models• Primary drivers: statistical• Used for early system
dimensioning (cell counts, etc.)Point-to-Point models
• Primary drivers: analytical• Used for detailed coverage
analysis and cell planningLocal Variability models
• Primary drivers: statistical• Characterizes microscopic level
fluctuations in a given locale, confidence-of-service probability
Simple Analytical• Free space (Friis formula)• Reflection cancellation• Knife-edge diffraction
Area• Okumura-Hata• Euro/Cost-231• Walfisch-Betroni/Ikegami
Point-to-Point• Ray Tracing
- Lee’s Method, others• Tech-Note 101• Longley-Rice, Biby-C
Local Variability• Rayleigh Distribution• Normal Distribution• Joint Probability Techniques
Examples of various model types
February, 2005 4 - 18RF100 v2.0 (c) 2005 Scott Baxter
General Principles Of Area Models
Area models mimic an averagepath in a defined areaThey’re based on measured data alone, with no consideration of individual path features or physical mechanismsTypical inputs used by model:
• Frequency• Distance from transmitter to
receiver• Actual or effective base
station & mobile heights• Average terrain elevation • Morphology correction loss
(Urban, Suburban, Rural, etc.)Results may be quite different than observed on individual paths in the area
RSSI, dBm
-120
-110
-100
-90
-80
-70
-60
-50
0 3 6 9 12 15 18 21 24 27 30 33
Distance from Cell Site, km
FieldStrength,dBµV/m
+90
+80
+70
+60
+50
+40
+30
+20
Green Trace shows actual measured signal strengths on a drive test radial, as determined by real-world physics.Red Trace shows the Okumura-Hata prediction for the same radial. The smooth curve is a good “fit” for real data. However, the signal strength at a specific location on the radial may be much higher or much lower than the simple prediction.
February, 2005 4 - 19RF100 v2.0 (c) 2005 Scott Baxter
The Okumura Model: General Concept
The Okumura model is based on detailed analysis of exhaustive drive-test measurements made in Tokyo and its suburbs during the late 1960’s and early 1970’s. The collected date included measurements on numerous VHF, UHF, and microwave signal sources, both horizontally and vertically polarized, at a wide range of heights.
The measurements were statistically processed and analyzed with respect to almost every imaginable variable. This analysis was distilled into the curves above, showing a median attenuation relative to free space loss Amu (f,d) and correlation factor Garea (f,area), for BS antenna height ht = 200 m and MS antenna height hr = 3 m.
Okumura has served as the basis for high-level design of many existing wireless systems, and has spawned a number of newer models adapted from its basic concepts and numerical parameters.
Med
ian
Atte
nuat
ion
A(f,
d), d
B
1
2
5
40
70
80
100
100 3000500Frequency f, MHz
10
50
70 Urban Area
d, k
m
30
850
26
35
100 200 300 500 700 1000 2000 3000Frequency f, (MHz)
5
10
15
20
25
30
Cor
rect
ion
fact
or, G
area
(dB
)
9 dB
850 MHz
Open area
Quasi open area
Suburban area
February, 2005 4 - 20RF100 v2.0 (c) 2005 Scott Baxter
Structure of the Okumura Model
The Okumura Model uses a combination of terms from basic physical mechanisms and arbitrary factors to fit 1960-1970 Tokyo drive test dataLater researchers (HATA, COST231, others) have expressed Okumura’s curves as formulas and automated the computation
Path Loss [dB] = LFS + Amu(f,d) - G(Hb) - G(Hm) - Garea
Free-Space Path Loss Base Station
Height Gain= 20 x Log (Hb/200)
Mobile StationHeight Gain
= 10 x Log (Hm/3)
Amu(f,d) Additional Median Lossfrom Okumura’s Curves
Med
ian
Atte
nuat
ion
A(f,d
), dB
1
2
5
40
70
80
100
100 3000500
Frequency f, MHz10
50
70 Urban Area
d, k
m
30
850
26
Morphology Gain0 dense urban5 urban10 suburban17 rural
35
100 200 300 500 700 1000 2000 3000Frequency f, (MHz)
5
10
15
20
25
30
Cor
rect
ion
fact
or, G
area
(dB
)
850 MHz
Open area
Quasi open area
Suburban area
February, 2005 4 - 21RF100 v2.0 (c) 2005 Scott Baxter
The Hata Model: General Concept
The Hata model is an empirical formula for propagation loss derived from Okumura’s model, to facilitate automatic calculation.The propagation loss in an urban area is presented in a simple general format A + B x log R, where A and B are functions of frequency and antenna height, R is distance between BS and MS antennasThe model is applicable to frequencies 100 MHz-1500 MHz, distances 1-20 km, BS antenna heights 30-200 m, MS antenna heights 1-10 mThe model is simplified due to following limitations:
• Isotropic antennas • Quasi-smooth (not irregular) terrain • Urban area propagation loss is presented as the standard formula• Correction equations are used for other areas
Although Hata model does not imply path-specific corrections, it has significant practical value and provide predictions which are very closely comparable with Okumura’s model
February, 2005 4 - 22RF100 v2.0 (c) 2005 Scott Baxter
Hata Model General Concept and Formulas
Formulas for median path loss are:(1) - Standard formula for urban areas(2) - For suburban areas(3) - For rural areas
Formulas for MS antenna ht. gain correction factor A(hm)(4) - For a small to medium sizes cities(5) and (6) - For large cities
f - carrier frequency, MHzhb and hm - BS and MS
antenna heights, md - distance between BS
and MS antennas, km
(1) LHATA (urban) [dB] =69.55 + 26.16 x log ( f ) + [ 44.9 - 6.55 x log ( hb ) ] x log ( d ) -13.82 x log ( hb ) - A ( hm )
(2) LHATA (suburban) [dB] = LHATA (urban) - 2 x [ log ( f/28 ) ]2 - 5.4
(3) LHATA (rural) [dB] =LHATA (urban) - 4.78 x [ log ( f ) ]2 - 18.33 x log ( f ) -40.98
(4) A ( hm ) [dB] = [ 11 x log ( f ) - 0.7 ] x hm - [ 1.56 x log ( f ) - 0.8 ]
(5) A ( hm ) [dB] = 8.29 x [ log ( 1.54 x hm ) ]2 - 1.1 (for f<= 300 MHz.)
(6) A ( hm ) [dB] = 3.2 x [ log ( 1175 x hm ) ]2 - 4.97 (for f > 300 MHz.)
Environmental Factor C0 dense urban-5 urban-10 suburban-17 rural
February, 2005 4 - 23RF100 v2.0 (c) 2005 Scott Baxter
The COST-231 model was developed by European COoperative for Scientific and Technical Research committee. It extends the HATA model to the 1.8-2 GHz. band in anticipation of PCS use.COST-231 is applicable for frequencies 1500-2000 MHz, distances 1-20 km, BS antenna heights 30-200 m, MS antenna heights 1-10 mParameters and variables:
• f is carrier frequency , in MHz• hb and hm are BS and MS antenna heights (m)• d is BS and MS separation, in km• A(hm) is MS antenna height correction factor
(same as in Hata model)• Cm is city size correction factor: Cm=0 dB for
suburbs and Cm=3 dB for metropolitan centers
The EURO COST-231 Model
LCOST (urban) [dB] = 46.3 + 33.9 x log ( f ) + [ 44.9 - 6.55 x log ( hb ) ] x log ( d ) + Cm -13.82 x log ( hb ) - A ( hm )
EnvironmentalFactor C1900-2 dense urban-5 urban
-10 suburban-26 rural
February, 2005 4 - 24RF100 v2.0 (c) 2005 Scott Baxter
Examples of Morphological ZonesSuburban: Mix of residential and business communities. Structures include 1-2 story houses 50 feet apart and 2-5 story shops and offices.Urban: Urban residential and office areas (Typical structures are 5-10 story buildings, hotels, hospitals, etc.)Dense Urban: Dense business districts with skyscrapers (10-20 stories and above) and high-rise apartments
Suburban SuburbanSuburban
UrbanUrbanUrban
Dense Urban Dense UrbanDense Urban
Although zone definitions are arbitrary, the examples and definitions illustrated above are typical of practice in North American PCS designs.
February, 2005 4 - 25RF100 v2.0 (c) 2005 Scott Baxter
Example Morphological Zones
Rural - Highway: Highways near open farm land, large open spaces, and sparsely populated residential areas. Typical structures are 1-2 story houses, barns, etc.Rural - In-town: Open farm land, large open spaces, and sparsely populated residential areas. Typical structures are 1-2 story houses, barns, etc.SuburbanSuburban
RuralRural
Suburban
Rural
Rural Rural -- HighwayHighwayRural - Highway
Notice how different zones may abruptly adjoin one another. In the case immediately above, farm land (rural) adjoins built-up subdivisions (suburban) -- same terrain, but different land use, penetration requirements, and anticipated traffic densities.
February, 2005 4 - 26RF100 v2.0 (c) 2005 Scott Baxter
The MSI Planet General Model
Pr - received power (dBm)Pt - transmit ERP (dBm)Hb - base station effective antenna heightHm - mobile station effective antenna heightDL - diffraction loss (dB) K1 - intercept K2 - slopeK3 - correction factor for base station antenna height gainK4 - correction factor for diffraction loss (accounts for clutter heights)K5 - Okumura-Hata correction factor for antenna height and distanceK6 - correction factor for mobile station antenna height gainKc - correction factor due to clutter at mobile station locationKo - correction factor for street orientation
Pr = Pt + K1 + k2 log(d) + k3 log(Hb) + K4 DL + K5 log(Hb) log(d)+ K6 log (Hm) + Kc + Ko
This is the general model format used in MSI’s popular PlaNET propagation prediction software for wireless systems. It includes terms similar to Okumura-Hata and COST-231 models, along with additional terms to include effects of specific obstructions and clutter on specific paths in the mobile environment.
February, 2005 4 - 27RF100 v2.0 (c) 2005 Scott Baxter
Typical Model Results Including Environmental Correction
-2-5
-10-26
TowerHeight,
mEIRP
(watts)C,dB
Range,kmf =1900 MHz.
Dense UrbanUrban
SuburbanRural
30303050
200200200200
2.523.504.810.3
COST-231/Hata
f = 870 MHz.Okumura/Hata
0-5
-10-17
TowerHeight,
mEIRP
(watts)C,dB
Range,km
Dense UrbanUrban
SuburbanRural
30303050
200200200200
4.04.96.7
26.8
February, 2005 4 - 28RF100 v2.0 (c) 2005 Scott Baxter
Propagation at 1900 MHz. vs. 800 MHz.
Propagation at 1900 MHz. is similar to 800 MHz., but all effects are more pronounced.
• Reflections are more effective• Shadows from obstructions are deeper• Foliage absorption is more attenuative• Penetration into buildings through openings is more effective,
but absorbing materials within buildings and their walls attenuate the signal more severely than at 800 MHz.
The net result of all these effects is to increase the “contrast” of hot and cold signal areas throughout a 1900 MHz. system, compared to what would have been obtained at 800 MHz.Overall, coverage radius of a 1900 MHz. BTS is approximately two-thirds the distance which would be obtained with the same ERP, same antenna height, at 800 MHz.
February, 2005 4 - 29RF100 v2.0 (c) 2005 Scott Baxter
Walfisch-Betroni/Walfisch-Ikegami Models
Ordinary Okumura-type models do work in this environment, but the Walfisch models attempt to improve accuracy by exploiting the actual propagation mechanisms involved
Path Loss = LFS + LRT + LMS
LFS = free space path loss (Friis formula)LRT = rooftop diffraction lossLMS = multiscreen reflection loss
Propagation in built-up portions of cities is dominated by ray diffraction over the tops of buildings and by ray “channeling” through multiple reflections down the street canyons
-20 dBm-30 dBm-40 dBm-50 dBm-60 dBm-70 dBm-80 dBm-90 dBm
-100 dBm-110 dBm-120 dBm
Signal Level
Legend
Area View
February, 2005 4 - 30RF100 v2.0 (c) 2005 Scott Baxter
Statistical TechniquesDistribution Statistics Concept
An area model predicts signal strength Vs. distance over an area
• This is the “median” or most probable signal strength at every distance from the cell
• The actual signal strength at any real location is determined by local physical effects, and will be higher or lower
• It is feasible to measure the observed median signal strength M and standard deviation σ
• M and σ can be applied to find probability of receiving an arbitrary signal level at a given distance
Median Signal Strength
σ,dB
Occurrences
RSSI
Normal Distribution
RSSI,dBm
Distance
Model is tweaked to produce “Best-Fit” curve
Signal Strength Predicted Vs. Observed
Observed Signal Strength
50% of observeddata is above curve
50% of observeddata is below curve
February, 2005 4 - 31RF100 v2.0 (c) 2005 Scott Baxter
Statistical TechniquesPractical Application Of Distribution Statistics
General Approach:• Use favorite model to predict Signal
Strength• Analyze measured data, obtain:
– median signal strength M(build histogram of observed
vs. measured data)– standard deviation of error, σ
(determine from histogram) • add an extra allowance into model
– drop curve so a desired % of observations are above model predictions
Median Signal Strength
σ,dB
Occurrences
RSSI
Normal Distribution
RSSI,dBm
Distance
25% of locations exceed blue curve
50% exceed red
75% exceed black
SIGNAL STRENGTH vs DISTANCE
Min signal req’d for operation
Cell radius for 75% reliability
at edge
Cell radius for 25% reliability
at edgeCell radius for 50% reliability
at edge
February, 2005 4 - 32RF100 v2.0 (c) 2005 Scott Baxter
Cell Edge Area Availability And Probability Of Service
Overall probability of service is best close to the BTS, and decreases with increasing distance away from BTSFor overall 90% location probability within cell coverage area, probability will be 75% at cell edge
• Result derived theoretically, confirmed in modeling with propagation tools, and observed from measurements
• True if path loss variations are log-normally distributed around predicted median values, as in mobile environment
• 90%/75% is a commonly-used wireless numerical coverage objective
• Recent publications by Nortel’s Dr. Pete Bernardin describe the relationship between area and edge reliability, and the field measurement techniques necessary to demonstrate an arbitrary degree of coverage reliability
Statistical View ofCell Coverage
Area Availability:90% overall within area
75%at edge of area
90%
75%
February, 2005 4 - 33RF100 v2.0 (c) 2005 Scott Baxter
Application Of Distribution Statistics: ExampleLet’s design a cell to deliver at least -95 dBm to at least 75% of the locations at the cell edge (This will provide coverage to 90% of total locations within the cell)Assume that measurements you have made show a 10 dB standarddeviation σOn the chart:
• To serve 75% of locations at the cell edge , we must deliver a median signal strength which is.675 times σ stronger than -95 dBm
• Calculate:- 95 dBm + ( .675 x 10 dB ) = - 88 dBm
• So, design for a median signal strength of -88 dBm!
Standard Deviations from Median (Average) Signal Strength
Cumulative Normal Distribution
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
-3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3
75%
0.675σ
February, 2005 4 - 34RF100 v2.0 (c) 2005 Scott Baxter
Statistical Techniques:Normal Distribution Graph & Table For Convenient Reference
Cumulative Normal Distribution
Standard Deviation from Mean Signal Strength
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
-3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3
CumulativeProbability
0.1%1%5%10%
StandardDeviation
-3.09-2.32-1.65-1.28-0.84 20%-0.52 30%
0.675 75%
0 50%0.52 70%
0.84 80%1.28 90%1.65 95%2.35 99%3.09 99.9%3.72 99.99%4.27 99.999%
February, 2005 4 - 35RF100 v2.0 (c) 2005 Scott Baxter
Building PenetrationStatistical Characterization
Statistical techniques are effective against situations that are difficult to characterize analytically
• Many analytical parameters, all highly variable and complex
Building coverage is modeled using existing outdoor path loss plus an additional “building penetration loss”
• Median value estimated/sampled • Statistical distribution determined• Standard deviation estimated or
measured• Additional margin allowed in link
budget to offset assumed lossTypical values are shown at left
Building penetration
Typical Penetration Losses, dBcompared to outdoor street level
EnvironmentType
(“morphology”)
MedianLoss,
dB
Std.Dev.σ, dB
Urban Bldg. 15 8Suburban Bldg. 10 8
Rural Bldg. 10 88 4Typical Vehicle
Dense Urban Bldg. 20 8
Vehicle penetration
February, 2005 4 - 36RF100 v2.0 (c) 2005 Scott Baxter
Composite Probability Of ServiceAdding Multiple Attenuating Mechanisms
For an in-building user, the actual signal level includes regular outdoor path attenuation plus building penetration lossBoth outdoor and penetration losses have their own variabilitieswith their own standard deviationsThe user’s overall composite probability of service must include composite median and standard deviation factors
σCOMPOSITE = ((σOUTDOOR)2+(σPENETRATION)2)1/2
LOSSCOMPOSITE = LOSSOUTDOOR+LOSSPENETRATION
Building
Outdoor Loss + Penetration Loss
February, 2005 4 - 37RF100 v2.0 (c) 2005 Scott Baxter
Composite Probability of ServiceCalculating Fade Margin For Link Budget
Example Case: Outdoor attenuation σ is 8 dB., and penetration loss σ is 8 dB. Desired probability of service is 75% at the cell edgeWhat is the composite σ? How much fade margin is required?
Composite Probability of ServiceCalculating Required Fade Margin
EnvironmentType
(“morphology”)MedianLoss,
dB
Std.Dev.σ, dB
Urban Bldg. 15 8Suburban Bldg. 10 8
Rural Bldg. 10 88 4Typical Vehicle
Dense Urban Bldg. 20 8
BuildingPenetration
Out-DoorStd.Dev.σ, dB
8888
8
CompositeTotal
AreaAvailabilityTarget, %
90%/75% @edge90%/75% @edge90%/75% @edge90%/75% @edge
90%/75% @edge
FadeMargin
dB
7.67.67.66.0
7.6
σCOMPOSITE = ((σOUTDOOR)2+(σPENETRATION)2)1/2
= ((8)2+(8)2)1/2 =(64+64)1/2 =(128)1/2 = 11.31 dBOn cumulative normal distribution curve, 75%
probability is 0.675 σ above median. Fade Margin required =
(11.31) • (0.675) = 7.63 dB.Cumulative Normal Distribution
Standard Deviations from Median (Average) Signal Strength
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
-3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3
75%
.675
February, 2005 4 - 38RF100 v2.0 (c) 2005 Scott Baxter
CommercialPropagation Prediction
Software
CommercialPropagation Prediction
Software
Chapter 4 Section C
February, 2005 4 - 39RF100 v2.0 (c) 2005 Scott Baxter
Point-To-Point Path-Driven Prediction Models
Use of models based on deterministic methods• Use of terrain data for construction of path profile• Path analysis (ray tracing) for obstruction, reflection analysis• Appropriate algorithms applied for best emulation of underlying
physics• May include some statistical techniques• Automated point-to-point analysis for enough points to appear
to provide large “area” coverage on raster or radial gridCommonly-used Resources
• Terrain databases• Morphological/Clutter Databases• Databases of existing and proposed sites• Antenna characteristics databases• Unique user-defined propagation models
February, 2005 4 - 40RF100 v2.0 (c) 2005 Scott Baxter
Path-Driven Propagation Prediction Tools Data Structure
Geographic “Overlay” Format:Output Map(s) on screen or plotter
• Coverage– field strengths @ probability– probabilities @ field strength
• Best-Server• C/I (Adjacent Channel & Co-
Channel)Cell locations, cell gridTerrain elevation data
• USGS & Commercial databases• Satellite or aerial photography
Clutter data• Roads, rivers, railroads, etc.• State, county, MTA, BTA
boundariesTraffic density overlayLand use overlay
February, 2005 4 - 41RF100 v2.0 (c) 2005 Scott Baxter
The World as “seen” by a Propagation Prediction Tool
Propagation tools use a terrain database, clutter data for land use, and vectors to represent features and traffic levels. The figure at right is a 3-D view of such databases in the area of this demonstration. Notice the granularity of the data and the very mild terrain undulations in the area, exaggerated 8 times in this view.
February, 2005 4 - 42RF100 v2.0 (c) 2005 Scott Baxter
Survey Of Commercially Available Tools
A wide variety of software tools are available for propagation prediction and system design Some tools are implemented on PC/DOS/Windows platforms, others on more powerful UNIX platformCapabilities and user interfaces vary greatlySeveral of the better-known tools for cellular RF engineering are shown in the table at right
RF Prediction Software Tools•Qualcomm
•QEDesign CDMA Tool(Unix)
•MSI•PlaNet (Unix)
•LCC•CellCad (Unix)•ANet (DOS PC)
•CNET•Wings (Unix)•Solutions (mainframe)
•ComSearch•IQSignum (Unix)
•AT&T•PACE (DOS PC)
•Motorola•proprietary (Unix)
•TEC Cellular: Wizard (DOS)•Elebra: CONDOR, CELTEC•Virginia Tech MPRG
•SMT-Plus Indoor Site Planning Tool
February, 2005 4 - 43RF100 v2.0 (c) 2005 Scott Baxter
Composite Coverage PlotA composite coverage plot shows the overall coverage produced by each sector in the field of view The color of each pixel corresponds to the signal level of the strongest server at that pointSuch plots are useful for identifying coverage holes and overall coverage extent
February, 2005 4 - 44RF100 v2.0 (c) 2005 Scott Baxter
Equal Power Handoff Boundaries Plot
A Best Server Plot or in CDMA terms, an Equal Power Handoff Boundaries plot paints each pixel with a unique color to identify the best-serving sector at that point
• the boundaries shown are the equal-power points between cells
This type of plot is extremely useful in creating initial neighbor lists and identifying areas of no dominant serverSome tools (MSI Planet) can generate automatic neighbor lists from such a plot
February, 2005 4 - 45RF100 v2.0 (c) 2005 Scott Baxter
Qualcomm’s QEDesign
Qualcomm’s commercial tool QEDesign offers a number of features targeted at CDMA system design and analysis. The figures above show the output of its microcell propagation analysis tool in the Washington, DC area, and a three-dimensional view of an antenna pattern. Other features of this package include live cursor mode in which the user can drag the cursor about and see in near-real-time the line-of-sight area visible from the selected location, or a coverage footprint calculated from that location.
February, 2005 4 - 46RF100 v2.0 (c) 2005 Scott Baxter
General Survey Of Tool Features
Universal Basic Features of Most Tools
Automatically calculates signal strength at many points over a geographic area
• Use databases of terrain data, environmental conditions, land use, building “clutter”, estimated geographic traffic distribution, etc.
• User-definable 3-dimensional antenna patterns
• Automatically analyzes paths, selects appropriate algorithms based on path geometry
• Produces plots of coverage, C/I, etc.Used for analysis of sites, interference, frequency planning, C/I evaluation, etc.Drawback: requires significant computation power, time and RF staff special training
-20 dBm-30 dBm-40 dBm-50 dBm-60 dBm-70 dBm-80 dBm-90 dBm-100 dBm-110 dBm-120 dBm
Signal Level
Legend
C/ILegend
>20 dB<20 dB<17 dB<14 dB
February, 2005 4 - 47RF100 v2.0 (c) 2005 Scott Baxter
General Survey Of Tool Features, Continued
Popular Features of Advanced Tools
Accepts measurement input, can automatically generate predicted-vs-measured statistics and map displaysAutomatic hexagon-manipulation grid utilityMaintains cell sites in relational database
• Easy manipulation, import, exportFlexible user interface allows multitaskingAllows multiple user-defined propagation modelsThree dimensional terrain viewRoads, boundaries, coastline easily overlaid onto any display
A
A
AA
A A
AA
A AA
A A
A
A
Pred. MeasMean -76 -72Std. Dv 9 12Samples 545 545
Area Name: DALLAS
Site Name
Subs: 100,000
Site # LatitudeLongitudeType Capacity
Number of Sites5 Total Capacity (Erlangs)221
SITE - 1SITE - 2SITE - 3SITE - 4SITE - 5
A1A2A3A4A5
33/17/4633/20/0833/16/5033/10/2833/25/21
96/08/3396/11/4996/12/1496/11/5196/03/53
S322S211S332S1101
77379188
Date: Initial Service
7
8
9
1
3
2
1
3
24
5
6
7
8
9
7
8
9
1
3
2
6
4
6
10
11
February, 2005 4 - 48RF100 v2.0 (c) 2005 Scott Baxter
General Survey Of Tool Features, Continued
More Popular Advanced Features
Produces plots of server boundaries, C/I plots, handoff boundaries, etc.Allows interactive change of antenna number, type, orientation, power and tiltUsing growth-scaleable traffic input mask, can predict traffic carried by each site, # channels required
• Can automatically highlight cells not meeting specified grade of service
Algorithms for automatic frequency planning and optimizationUser can define or “mask” cells to be changed or unchanged during automatic optimization
43
2
56
1743
2
56
17
CELL ERL Channels14 8.3 1722 2.1 526X 1.7 426Y 23 3126Z 14 20
February, 2005 4 - 49RF100 v2.0 (c) 2005 Scott Baxter
General Survey Of Tool Features, Continued
More Popular Advanced Features
Identification of server and interferer signal levels in live cursor mode upon graphical coverage displayGenerates bin C/I & coverage statistics for system evaluationPredicted handoff analysis
• Statistical analysis of most likely handoff candidates
• Automatic generation of neighbor cell lists
• Percentage probability of handover
Runs on powerful workstations to minimize computation time
Cell 51 -82 dBmCell 76 -97 dBmC/I +15 dB
Cell 18Cell 24 48%Cell 16 22%Cell 17 18%Cell 05 8%Cell 22 4%
C/I Pct. of Area>20 dB 93.0%<20 dB 7.0%<17 dB 2.2%
February, 2005 4 - 50RF100 v2.0 (c) 2005 Scott Baxter
Resolution Of Terrain Databases
Elevation data in terrain databases can be stored in any of several formats:
• Contour vectors: lines of constant elevation in vector segment form, digitized from topographic maps
• Elevation sample points on rectangular grids with fixed spacing
• Elevation sample points on latitude-longitude grids with spacing of a fixed number of arc-seconds
• Data can be converted from one format to another
10m
10m
3 arc-seconds
3 arc-seconds
February, 2005 4 - 51RF100 v2.0 (c) 2005 Scott Baxter
Resolution Of Terrain Databases, Continued
It is useful to know the horizontal spacing in feet between sample points in a terrain database using arc-seconds, i.e., latitude-longitude spacingNorth-South spacing is constant, everywhere on the planet
• 1 arc-second = 101.34 feet• 1 degree = 69.096 miles
East-West sample spacing varies with the cosine of the North Latitude
• = 101.34 feet/arcsecond at the Equator
• = 0 feet/arcsecond at Poles• = 101.34 ft. * Cos (N Lat)
per arcsecond, everywhere
N30º
N60º
(North Pole) N90º
(Equator) 0º
S30º
S60º
(South Pole) S90º
Latitude
0º Greenwich, UK
W 30º
W 60º
W 90º
W 120º
Longitude
1sec.101.34 ft
101.34 ft * Cos (N Latº )
February, 2005 4 - 52RF100 v2.0 (c) 2005 Scott Baxter
CommercialMeasurement Tools
CommercialMeasurement Tools
Chapter 4 Section D
February, 2005 4 - 53RF100 v2.0 (c) 2005 Scott Baxter
Propagation Data Collection Philosophy
RF testing of sites is usually performed for one of two reasons:Drive Testing for model calibration
• Prior to cell design of a wireless system, accurate models of propagation in the area must be developed for use by the prediction software. A significant number of typical sites are evaluated using the test transmitter and receiver to determine signal decay rates and to get a fairly accurate understanding of the effects of typical clutter in the area.
• Tests are also conducted to evaluate the additional attenuation which the signal suffers during penetration of typical buildings and vehicles.
• The focus is on developing models generally applicable to the area, not on the performance of specific individual sites.
Drive Testing for site evaluation• Although propagation models for an area already have been refined,
coverage of a particular site is so critical, or its environment so variable due to urban clutter, that it is essential to actually measure the coverage and interference it will produce. The focus is on this specific site.
February, 2005 4 - 54RF100 v2.0 (c) 2005 Scott Baxter
CW or Modulated Test Signals?Can measurements of unmodulated RF carriers provide adequate propagation data for system design, or is it advisable to use amodulated RF signal similar to the type which will be radiated by actual BTS in the contemplated system?
• CW (continuous wave, i.e., unmodulated carriers) transmitters are moderately priced ($10K-$25K). CW-only receivers are priced from $5K to over $20K.
• Technology-specific GSM or CDMA modulated test transmitter-receiver systems are available, at costs in the $100,000-$275,000 range per TX-RX system.
Multiple Sites Simultaneously
Multipath Characteristics
Modulated Systems CW Systems
FER, BER statistics
Too expensive!
Delay Spread
Yes
Yes
Usually Not. However, DSP post-processing can yield some multipath data using various transforms. (Not
commercially available yet.)
NoPropagation Loss Mapping Yes Yes
February, 2005 4 - 55RF100 v2.0 (c) 2005 Scott Baxter
Summary of Commercial Data Collection Tools
Measurement data can be collected manually, but it is simply too tedious to obtain statistically useful quantities by handThere are many commercial data collection systems available to automate the collection processMany modern propagation prediction software packages have the capability to import measurement data, compare it with predicted values, and generate statistical outputs (mean error, standard deviation, etc.).
Commercial Measurement Systems•Agilent (formerly HP)
•Digital receiver with spectrum analyzer and PN scanner capabilities; handset data collection capabilities
•Andrew (formerly Grayson):•Invex device and collection software•Interpreter post-processing tool
•COMARCO•configurable multi-device tool with scanners, receivers, handset data capture
•Ericsson TEMS tool•handset capture
•Qualcomm•CAIT tool (Common Air Interface Tester)
•Willtech•Bluerose tool with handset, PN scanner, and receiver functions)
•ZKSAM•collection tool and postprocessingmodule
February, 2005 4 - 56RF100 v2.0 (c) 2005 Scott Baxter
Elements of Typical Measurement Systems
WirelessReceiver
PC or Collector
GPSReceiver
DeadReckoning
Main FeaturesField strength measurement
• Accurate collection in real-time• Multi-channel, averaging
capabilityLocation Data Collection Methods:
• Global Positioning System (GPS)• Dead reckoning on digitized map
database using on-board compass and wheel revolutions sensor
• A combination of both methods is recommended for the best results
Ideally, a system should be calibrated in absolute units, not just raw received power level indications
• Record normalized antenna gain, measured line loss
February, 2005 4 - 57RF100 v2.0 (c) 2005 Scott Baxter
Typical Test Transmitter Operations
Typical Characteristics• portable, low power needs• weatherproof or weather resistant• regulated power output• frequency-agile: synthesized
Operational Concerns• spectrum coordination and proper
authorization to radiate test signal• antenna unobstructed• stable AC power• SAFETY:
– people/equipment falling due to wind, or tripping on obstacles
– electric shock– damage to rooftop
February, 2005 4 - 58RF100 v2.0 (c) 2005 Scott Baxter
Example of Mobile Receiver: Andrew’s Invex3G Tool
100 MB ethernet connection to PCthe eight card slots can hold receivers or dual-phone cardsthere’s also room for two internal PN scannersMultiple Invex units can be cascaded for multi-phone load-test applicationsCards are field-swappable - Users can reconfigure the unit in the field for different tasks without factory assistanceReceivers and decoders are installed only for the appropriate technologies and frequency bandsInternal GPS or external GPS may be used, with or without dead-reckoning capabilities
February, 2005 4 - 59RF100 v2.0 (c) 2005 Scott Baxter
Selecting and Tuning Propagation Models
Parameters of propagation models must be adjusted for best fit to actual drive-test measured data in the area where the model is appliedThe figure at right shows drive-test signal strengths obtained using a test transmitter at an actual test site Tools automate the process of comparing the measured data with its own predictions, and deriving error statisticsPrediction model parameters then can be “tuned” to minimize observed error
February, 2005 4 - 60RF100 v2.0 (c) 2005 Scott Baxter
Measured Data vs. Model Predictions
Is the propagation model approximately correct?• Is the data scatter small enough to justify use of a model?• correct slope to match data• correct position up/down on Y-axis?
February, 2005 4 - 61RF100 v2.0 (c) 2005 Scott Baxter
Analysis of Measured vs. Predicted
Several tools produce histograms showing the distribution of thedifferences between measured and predicted valuesThe mean of the difference between predicted and measured is a very important quantity. It should be small (on order of a few dB).The standard deviation of the difference also should be small. If it is substantially larger than 8 dB., then either:
• the environment is very diverse (perhaps it should be broken into pieces with separate models for better fit) or
• the slope of the model is significantly different than the observed slope of the measurements (review the Sig. vs. Dist. graph)
February, 2005 4 - 62RF100 v2.0 (c) 2005 Scott Baxter
Displaying Error Distribution by Location
Suppose a major hill blocked the signal in one direction, or the antenna pattern had an unexpected minimum in that directionThis would cause the data in the shadowed region to differ substantially from data in all remaining directionsSome tools can display the error values on a map like the one at right, to provide quick visual evidence for recognizing this type of problem
February, 2005 5 - 1RF100 v2.0 (c) 2005 Scott Baxter
Radiating Systems for Wireless Networks
Radiating Systems for Wireless Networks
Chapter 5
Dipole
Typical WirelessOmni Antenna
Isotropic
February, 2005 5 - 2RF100 v2.0 (c) 2005 Scott Baxter
Antennas for WirelessAntennas for Wireless
Chapter 5 Section A
February, 2005 5 - 3RF100 v2.0 (c) 2005 Scott Baxter
Understanding Antenna RadiationThe Principle Of Current Moments
An antenna is just a passive conductor carrying RF current
• RF power causes the current flow
• Current flowing radiates electromagnetic fields
• Electromagnetic fields cause current in receiving antennas
The effect of the total antenna is the sum of what every tiny “slice” of the antenna is doing
• Radiation of a tiny “slice” is proportional to its length times the current in it
• remember, the current has a magnitude and a phase!
TX RX
Width of banddenotes current
magnitude
Zero currentat each end
Maximum currentat the middle
Current induced inreceiving antennais vector sum of
contribution of everytiny “slice” of
radiating antenna
each tiny imaginary “slice”of the antennadoes its share
of radiating
February, 2005 5 - 4RF100 v2.0 (c) 2005 Scott Baxter
Different Radiation In Different DirectionsEach “slice” of the antenna produces a definite amount of radiation at a specific phase angleStrength of signal received varies, depending on direction of departure from radiating antenna
• In some directions, the components add up in phase to a strong signal level
• In other directions, due to the different distances the various components must travel to reach the receiver, they are out of phase and cancel, leaving a much weaker signal
An antenna’s directivity is the same for transmission & reception
TXMaximumRadiation:contributions
in phase, reinforce
MinimumRadiation:contributionsout of phase,
cancel
MinimumRadiation:contributionsout of phase,
cancel
February, 2005 5 - 5RF100 v2.0 (c) 2005 Scott Baxter
Antenna Polarization
To intercept significant energy, a receiving antenna must be oriented parallel to the transmitting antenna
• A receiving antenna oriented at right angles to the transmitting antenna is “cross-polarized”; will have very little current induced
• Vertical polarization is the default convention in wireless telephony• In the cluttered urban environment, energy becomes scattered and
“de-polarized” during propagation, so polarization is not as critical• Handset users hold the antennas at seemingly random angles…..
TX
ElectromagneticField
current almostno
current
Antenna 1VerticallyPolarized
Antenna 2Horizontally
Polarized
RX
RF current in a conductor causes electromagnetic fields that seek to induce current flowing in the samedirection in other conductors.
The orientation of the antenna is called its polarization.
Coupling between two antennas is proportional to the cosine of the angle of their relative orientation
February, 2005 5 - 6RF100 v2.0 (c) 2005 Scott Baxter
Antenna Gain
Antennas are passive devices: they do not produce power
• Can only receive power in one form and pass it on in another, minus incidental losses
• Cannot generate power or “amplify”However, an antenna can appear to have “gain”compared against another antenna or condition. This gain can be expressed in dB or as a power ratio. It applies both to radiating and receivingA directional antenna, in its direction of maximum radiation, appears to have “gain” compared against a non-directional antennaGain in one direction comes at the expense of less radiation in other directionsAntenna Gain is RELATIVE, not ABSOLUTE
• When describing antenna “gain”, the comparison condition must be stated or implied
Omni-directionalAntenna
DirectionalAntenna
February, 2005 5 - 7RF100 v2.0 (c) 2005 Scott Baxter
Reference Antennas
Isotropic Radiator• Truly non-directional -- in 3 dimensions• Difficult to build or approximate physically,
but mathematically very simple to describe• A popular reference: 1000 MHz and above
– PCS, microwave, etc.Dipole Antenna
• Non-directional in 2-dimensional plane only• Can be easily constructed, physically
practical• A popular reference: below 1000 MHz
– 800 MHz. cellular, land mobile, TV & FM
IsotropicAntenna
(watts or dBm) ERP Effective Radiated Power Vs. DipoleEffective Radiated Power Vs. Isotropic
Gain above Dipole referenceGain above Isotropic radiator
(watts or dBm) EIRP dBddBi
Quantity Units Dipole Antenna
Notice that a dipolehas 2.15 dB gaincompared to an isotropic antenna.
February, 2005 5 - 8RF100 v2.0 (c) 2005 Scott Baxter
Effective Radiated Power
An antenna radiates all power fed to it from the transmitter, minus any incidental losses. Every direction gets some amount of powerEffective Radiated Power (ERP) is the apparentpower in a particular direction
• Equal to actual transmitter power times antenna gain in that direction
Effective Radiated Power is expressed in comparison to a standard radiator
• ERP: compared with dipole antenna• EIRP: compared with Isotropic antenna
AB
ERP B A (ref)
100w275w
ReferenceAntenna
TX100 W
A
DirectionalAntenna TX
100 W
B
Example: Antennas A and B each radiate 100 watts fromtheir own transmitters. Antenna A is our reference, ithappens to be isotropic.Antenna B is directional. In its maximum direction, itssignal seems 2.75 stronger than the signal from antennaA. Antenna B’s EIRP in this case is 275 watts.
February, 2005 5 - 9RF100 v2.0 (c) 2005 Scott Baxter
Antenna Gain And ERPExamples
Many wireless systems at 1900 & 800 MHz use omni antennas like the one shown in this figureThese patterns are drawn to scale in E-field radiation units, based on equal power to each antennaNotice the typical wireless omni antenna concentrates most of its radiation toward the horizon, where users are, at the expense of sending less radiation sharply upward or downwardThe wireless antenna’s maximum radiation is 12.1 dB stronger than the isotropic (thus 12.1 dBi gain), and10 dB stronger than the dipole (so 10 dBd gain).
IsotropicDipoleOmni
12.1 dBi10dBd
Gain Comparison
Isotropic
Dipole
Typical WirelessOmni Antenna
Gain 12.1 dBi or 10 dBd
February, 2005 5 - 10RF100 v2.0 (c) 2005 Scott Baxter
Radiation PatternsKey Features And Terminology
An antenna’s directivity is expressed as a series of patternsThe Horizontal Plane Pattern graphs the radiation as a function of azimuth (i.e..,direction N-E-S-W)The Vertical Plane Pattern graphs the radiation as a function of elevation (i.e.., up, down, horizontal)Antennas are often compared by noting specific landmark points on their patterns:
• -3 dB (“HPBW”), -6 dB, -10 dB points
• Front-to-back ratio• Angles of nulls, minor lobes, etc.
Typical ExampleHorizontal Plane Pattern
0 (N)
90(E)
180 (S)
270(W)
0 -10
-20
-30 dB
Notice -3 dB points
Front-to-back Ratio
10 dBpoints
MainLobe
a MinorLobe
nulls orminima
February, 2005 5 - 11RF100 v2.0 (c) 2005 Scott Baxter
In phase
Out of phase
How Antennas Achieve Their Gain
Quasi-Optical Techniques (reflection, focusing)• Reflectors can be used to concentrate
radiation– technique works best at microwave frequencies,
where reflectors are small• Examples:
– corner reflector used at cellular or higher frequencies
– parabolic reflector used at microwave frequencies
– grid or single pipe reflector for cellular
Array techniques (discrete elements)• Power is fed or coupled to multiple
antenna elements; each element radiates• Elements’ radiation in phase in some
directions• In other directions, a phase delay for each
element creates pattern lobes and nulls
February, 2005 5 - 12RF100 v2.0 (c) 2005 Scott Baxter
Types Of Arrays
Collinear vertical arrays• Essentially omnidirectional in
horizontal plane• Power gain approximately
equal to the number of elements
• Nulls exist in vertical pattern, unless deliberately filled
Arrays in horizontal plane• Directional in horizontal
plane: useful for sectorization• Yagi
– one driven element, parasitic coupling to others
• Log-periodic– all elements driven– wide bandwidth
All of these types of antennas are used in wireless
RF power
RF power
CollinearVerticalArray
Yagi
Log-Periodic
February, 2005 5 - 13RF100 v2.0 (c) 2005 Scott Baxter
Omni AntennasCollinear Vertical Arrays
The family of omni-directional wireless antennas:Number of elements determines
• Physical size• Gain• Beamwidth, first null angle
Models with many elements have very narrow beamwidths
• Require stable mounting and careful alignment
• Watch out: be sure nulls do not fall in important coverage areas
Rod and grid reflectors are sometimes added for mild directivity
Examples: 800 MHz.: dB803, PD10017, BCR-10O, Kathrein 740-198
1900 MHz.: dB-910, ASPP2933
beamwidth
Angleof
firstnull
θ
-3 dB
Vertical Plane Pattern
Number ofElements
PowerGain
Gain,dB
Angleθ
0.00 n/a3.01 26.57°4.77 18.43°6.02 14.04°6.99 11.31°7.78 9.46°8.45 8.13°9.03 7.13°9.54 6.34°10.00 5.71°10.41 5.19°10.79 4.76°11.14 4.40°
1234567891011121314
1234567891011121314 11.46 4.09°
Typical Collinear Arrays
February, 2005 5 - 14RF100 v2.0 (c) 2005 Scott Baxter
Sector AntennasReflectors And Vertical Arrays
Typical commercial sector antennas are vertical combinations of dipoles, yagis, or log-periodic elements with reflector (panel or grid) backing
• Vertical plane pattern is determined by number of vertically-separated elements
– varies from 1 to 8, affecting mainly gain and vertical plane beamwidth
• Horizontal plane pattern is determined by:
– number of horizontally-spaced elements
– shape of reflectors (is reflector folded?)
Vertical Plane PatternUp
Down
Horizontal Plane PatternN
E
S
W
February, 2005 5 - 15RF100 v2.0 (c) 2005 Scott Baxter
Example Of Antenna Catalog Specifications
Frequency Range, MHz.Gain - dBd/dBiVSWRBeamwidth (3 dB from maximum)PolarizationMaximum power input - WattsInput Impedance - OhmsLightning ProtectionTermination - StandardJumper Cable
Electrical DataAntenna Model ASPP2933 ASPP2936 dB910C-M
1850-1990 1850-1990 1850-19703/5.1
<1.5:132°
Vertical400
50Direct Ground
N-FemaleOrder Sep.
6/8.1<1.5:1
15°Vertical
40050
Direct GroundN-Female
Order Sep.
10/12.1<1.5:1
5°Vertical
40050
Direct GroundN-Female
Order Sep.
Mechanical DataAntenna ModelOverall length - in (mm)Radome OD - in (mm)Wind area - ft2 (m2)Wind load @ 125 mph/201 kph lb-f (n)Maximum wind speed - mph (kph)Weight - lbs (kg)Shipping Weight - lbs (kg)Clamps (steel)
ASPP293324 (610)
1.1 (25.4).17 (.0155)
4 (17)140 (225)
4 (1.8)11 (4.9)
ASPA320
ASPP293636 (915)
1.0 (25.4).25 (.0233)
6 (26)140 (225)
6 (2.7)13 (5.9)
ASPA320
dB910C-M77 (1955)
1.5 (38).54 (.05)
14 (61)125 (201)
5.2 (2.4)9 (4.1)
Integral
February, 2005 5 - 16RF100 v2.0 (c) 2005 Scott Baxter
Example Of Antenna Catalog Radiation Pattern
Vertical Plane Pattern • E-Plane (elevation plane)• Gain: 10 dBd• Dipole pattern is superimposed at
scale for comparison (not often shown in commercial catalogs)
• Frequency is shown• Pattern values shown in dBd• Note 1-degree indices through
region of main lobe for most accurate reading
• Notice minor lobe and null detail!
February, 2005 5 - 17RF100 v2.0 (c) 2005 Scott Baxter
Other RF ElementsOther RF Elements
Chapter 5 Section B
February, 2005 5 - 18RF100 v2.0 (c) 2005 Scott Baxter
Antenna Systems
Antenna systems include more than just antennasTransmission Lines
• Necessary to connect transmitting and receiving equipmentOther Components necessary to achieve desired system function
• Filters, Combiners, Duplexers - to achieve desired connections• Directional Couplers, wattmeters - for measurement of performance
Manufacturer’s system may include some or all of these items• Remaining items are added individually as needed by system operator
F R
Duplexer
Combiner
BPF
TX
RX
TXTransmission LineJumper
Jumpers
DirectionalCoupler
Antenna
February, 2005 5 - 19RF100 v2.0 (c) 2005 Scott Baxter
Characteristics Of Transmission Lines
Physical CharacteristicsType of line
• Coaxial, stripline, open-wire
• Balanced, unbalancedPhysical configuration
• Dielectric:– air– foam
• Outside surface– unjacketed– jacketed
Size (nominal outer diameter)• 1/4”,1/2”, 7/8”, 1-1/4”,
1-5/8”, 2-1/4”, 3”Foam
DielectricAir
Dielectric
Typical coaxial cablesUsed as feeders in wireless applications
February, 2005 5 - 20RF100 v2.0 (c) 2005 Scott Baxter
Transmission LinesSome Practical Considerations
Transmission lines practical considerations• Periodicity of inner conductor
supporting structure can cause VSWR peaks at some frequencies, so specify the frequency band when ordering
• Air dielectric lines– lower loss than foam-dielectric; dry air
is excellent insulator – shipped pressurized; do not accept
delivery if pressure leak• Foam dielectric lines
– simple, low maintenance; despite slightly higher loss
– small pinholes and leaks can allow water penetration and gradual attenuation increases
FoamDielectric
AirDielectric
February, 2005 5 - 21RF100 v2.0 (c) 2005 Scott Baxter
Characteristics Of Transmission Lines, Continued
Electrical CharacteristicsAttenuation
• Varies with frequency, size, dielectric characteristics of insulation
• Usually specified in dB/100 ft and/or dB/100 m
Characteristic impedance Z0 (50 ohms is the usual standard; 75 ohms is sometimes used)
• Value set by inner/outer diameter ratio and dielectric characteristics of insulation
• Connectors must preserve constant impedance (see figure at right)
Velocity factor• Determined by dielectric characteristics
of insulation. Power-handling capability
• Varies with size, conductor materials, dielectric characteristics
dD
Characteristic Impedanceof a Coaxial Line
Zo = ( 138 / ( ε 1/2 ) ) Log10 ( D / d )ε = Dielectric Constant
= 1 for vacuum or dry air
February, 2005 5 - 22RF100 v2.0 (c) 2005 Scott Baxter
Transmission LinesSpecial Electrical Properties
Transmission lines have impedance-transforming properties
• When terminated with same impedance as Zo, input to line appears as impedance Zo
• When terminated with impedance different from Zo, input to line is a complex function of frequency and line length. Use Smith Chart or formulae to compute
Special case of interest: Line section one-quarter wavelength long has convenient properties useful in matching networks
• ZIN = (Zo2)/(ZLOAD)
Zo=50Ω ZLOAD=50Ω
ZIN = 50Ω
Matched condition
Zo=50ΩZLOAD=
83-j22Ω
ZIN = ?Mismatched condition
Zo=50ΩZLOAD=100ΩZIN=25Ω
λ/4
ZIN= ZO2
/ ZLOAD
Deliberate mismatchfor impedance transformation
February, 2005 5 - 23RF100 v2.0 (c) 2005 Scott Baxter
Transmission LinesImportant Installation Practices
Respect specified minimum bending radius!
• Inner conductor must remain concentric, otherwise Zo changes
• Dents, kinks in outer conductor change Zo
Don’t bend large, stiff lines (1-5/8” or larger) to make direct connection with antennas Use appropriate jumpers, weatherproofed properly.Secure jumpers against wind vibration.
ObserveMinimumBendingRadius!
February, 2005 5 - 24RF100 v2.0 (c) 2005 Scott Baxter
Transmission LinesImportant Installation Practices, Continued
During hoisting• Allow line to support its own
weight only for distances approved by manufacturer
• Deformation and stretching may result, changing the Zo
• Use hoisting grips, messenger cable
After mounting• Support the line with proper
mounting clamps at manufacturer’s recommended spacing intervals
• Strong winds will set up damaging metal-fatigue-inducing vibrations
200 ft~60 mMax.
3-6 ft
February, 2005 5 - 25RF100 v2.0 (c) 2005 Scott Baxter
RF FiltersBasic Characteristics And Specifications
Types of Filters• Single-pole:
– pass
– reject (notch)• Multi-pole:
– band-pass– band-reject
Key electrical characteristics• Insertion loss• Passband ripple• Passband width
– upper, lower cutoff frequencies
• Attenuation slope at band edge• Ultimate out-of-band attenuation
Typical bandpass filters have insertion loss of 1-3 dB. andpassband ripple of 2-6 dB.
Bandwidth is typically 1-20% of center frequency, depending on application. Attenuation slope and out-of-band attenuation depend on # of poles & design
Typical RF bandpass filter0
Atte
nuat
ion,
dB
Frequency, megaHertz
passband rippleinsertion loss
-3 dB passbandwidth
February, 2005 5 - 26RF100 v2.0 (c) 2005 Scott Baxter
RF FiltersTypes And Applications
Filters are the basic building blocks of duplexers and more complex devicesMost manufacturers’ network equipment includes internal bandpass filters at receiver input and transmitter outputFilters are also available for special applications Number of poles (filter elements) and other design variables determine filter’s electrical characteristics
• Bandwidth rejection• Insertion loss• Slopes• Ripple, etc.
Notice construction: RF input excites one quarter-wave element and electromagnet fields propagate from element to element, finally exciting the last element which is directly coupled to the output.
Each element is individually set and forms a pole in the filter’s overall response curve.
Typical RF Bandpass Filter
∼λ/4
February, 2005 5 - 27RF100 v2.0 (c) 2005 Scott Baxter
Basics Of Transmitting Combiners
Allows multiple transmitters to feed single antenna, providing
• Minimum power loss from transmitter to antenna
• Maximum isolation between transmitters
Combiner types• Tuned
– low insertion loss ~1-3 dB– transmitter frequencies must be
significantly separated• Hybrid
– insertion loss -3 dB per stage– no restriction on transmitter
frequencies• Linear amplifier
– linearity and intermodulation are major design and operation issues
Typical tuned combinerapplication
TX TX TX TX TX TX TX TX
Antenna
Typical hybrid combinerapplication
TX TX TX TX TX TX TX TX
Antenna
~-3 dB
~-3 dB
~-3 dB
February, 2005 5 - 28RF100 v2.0 (c) 2005 Scott Baxter
Duplexer Basics
Duplexer allows simultaneous transmitting and receiving on one antenna
• Nortel 1900 MHz BTS RFFEsinclude internal duplexer
• Nortel 800 MHz BTS does not include duplexer but commercial units can be used if desired
Important duplexer specifications• TX pass-through insertion loss• RX pass-through insertion loss• TX-to-RX isolation at TX
frequency (RX intermodulationissue)
• TX-to-RX isolation at RX frequency (TX noise floor issue)
• Internally-generated IMP limit specification
fR fT
RX TX
Antenna
Duplexer
Principle of operationDuplexer is composed of individualbandpass filters to isolate TX fromRX while allowing access to antennafor both. Filter design determinesactual isolation between TX and RX,and insertion loss TX-to-Antennaand RX-to-Antenna.
February, 2005 5 - 29RF100 v2.0 (c) 2005 Scott Baxter
Directional Couplers
Couplers are used to measure forward and reflected energy in a transmission line; it has 4 ports:
• Input (from TX), Output (to load)
• Forward and Reverse SamplesSensing loops probe E& I in line
• Equal sensitivity to E & H fields• Terminations absorb induced
current in one direction, leaving only sample of other direction
Typical performance specifications• Coupling factor ~20, ~30,
~40 dB., order as appropriate for application
• Directivity ~30-~40 dB., f($)– defined as relative
attenuation of unwanteddirection in each sample
Principle of operation
ZLOAD= 50Ω
Input
Reverse Sample
Forward Sample
RT
RT
Typical directional coupler
Main line’s E & I induce equal signals in sense loops. E is direction-independent, but I’s polarity depends on direction andcancels sample induced in one direction.Thus sense loop signals are directional.One end is used, the other terminated.
February, 2005 5 - 30RF100 v2.0 (c) 2005 Scott Baxter
Basics of Antenna TestingBasics of Antenna Testing
Chapter 5 Section C
February, 2005 5 - 31RF100 v2.0 (c) 2005 Scott Baxter
Testing Communications Feedlines and Antennas
AC power wiring and voice telephone wiring do not require extremely critical wiring practices
• just make sure the connections and insulation are good, heat is not allowed to build up, and you’ll have good results
• AC power frequencies and audio signal frequencies have wavelengths of many miles
– a few feet of wire won’t radiate much energyHigh frequency RF wiring practice is much more critical since signal wavelengths are only a few inches or feet
• any bend or protruding bit of wire can serve as an unintentional antenna, “leaking” energy
• even splices and connections can leak energy unless their shape and dimensions are closely controlled
• abrupt changes in cable shape “reflect” energy back down the transmission line, causing many problems
Precisely shaped cables and connectors, careful installation and accurate testing are required to avoid significant antenna system performance problems
February, 2005 5 - 32RF100 v2.0 (c) 2005 Scott Baxter
Forward and Reflected Energy
In a perfect antenna system, the transmission line and the antenna have the same impedance
• we say they are “impedance matched”All the energy from the transmitter passes through and is radiated from the antenna
• virtually no energy is reflected back to the transmitter
Transmission Line
Antenna
TransmitterForward PowerVirtually no reflected power
50Ω50Ω
50Ω
February, 2005 5 - 33RF100 v2.0 (c) 2005 Scott Baxter
Forward and Reflected Energy
Transmission Line
Antenna
Transmitter
Significant Reflected Power
50Ω
42-j17Ω
Forward Power
dent or kink37Ω
In a damaged antenna system, the impedance match is not good• there could be a dent, kink, or a spot with water in the transmission
line– the different impedance in the line at this spot will cause some of
the energy to be reflected backwards• the antenna could be damaged or dangling, causing it to have an
altered impedance– the antenna’s different impedance will reflect some of the energy
backwards down the lineThe Site Master® Distance-To-Fault mode will be helpful in finding the location of the damage
February, 2005 5 - 34RF100 v2.0 (c) 2005 Scott Baxter
How Much Reflection? Four Ways to Say ItThere are four ways of expressing how much energy is being reflected
• different users like different methodsVoltage Standing Wave Ratio (VSWR) (used by hobbyists and consumers)
• the reflected voltage is in phase with the incident voltage at some places and out of phase at others
• VSWR is the ratio of Vmax/VminReflected Power as % of Forward Power (used by field personnel in some industries)
• just divide Rev by Fwd, use percentReturn Loss (used by field personnel)
• how many db weaker is the reflected energy than the forward energy
Reflection Coefficient (academic users)• vector ratio of reflected/incident voltage
or current• usually expressed as a polar vector, with
magnitude and phase
Vmax
Vmin
SWR: Standing Wave Ratio
= Vmax/ Vmin
FORWARD
REFLECTED
Reflected Power (%)
= 100 x RevPwr
FwdPwr
FORWARD
REFLECTED
Return Loss (db)
= 10 x Log10
RevPwrFwdPwr
FORWARD
REFLECTED
Reflection Coefficient (vector ratio)Vreflected
Vincident
=
February, 2005 5 - 35RF100 v2.0 (c) 2005 Scott Baxter
Comparing Reflection Reports in Different FormsReflection expressed in one form can be converted and expressed in the other formsFor example, consider a VSWR of 1.5 : 1
• this is 4% reflected power• this is a return loss of 14 db• to calculate the reflection coefficient, the
phase of the reflection is also needed
VSWR vs. Return Loss
VSWR
0
10
20
30
40
50
1 1.5 2 2.5 3
FORWARD
REFLECTED
Reflected Power (%)
= 100 x RevPwr
FwdPwr
FORWARD
REFLECTED
Return Loss (db)
= 10 x Log10
RevPwrFwdPwr
FORWARD
REFLECTED
Reflection Coefficient (vector ratio)Vreflected
Vincident
=
Vmax
Vmin
SWR: STANDING WAVE RATIO= Vmax/ Vmin
=
Reflected PowerForward Power
Reflected PowerForward Power
1 +
1 -
February, 2005 5 - 36RF100 v2.0 (c) 2005 Scott Baxter
Swept Return Loss and TDR Measurements
It’s a good idea to take swept and TDR return loss measurements of a new antenna at installation and to recheck periodically
• maintain a printed or electronically stored copy of the analyzer output for comparison
• most types of antenna or transmission line failures are easily detectable by comparison with stored data
What is the maximum acceptable value of return loss as seen in sketch above?Given:
Antenna VSWR max spec is 1.5 : 1 between f1 and f2Transmission line loss = 3 dB.
Consideration & Solution:From chart, VSWR of 1.5 : 1 is a return loss of -14 dB, measured at the antennaPower goes through the line loss of -3 db to reach the antenna, and -3 db to returnTherefore, maximum acceptable observation on the ground is -14 -3 -3 = - 20 dB.
Site Master®-10
-20
-30f1 f2
Jumper
Feedline
Jumper
Antenna
February, 2005 5 - 37RF100 v2.0 (c) 2005 Scott Baxter
Example Frequency Sweep Test Plot
February, 2005 5 - 38RF100 v2.0 (c) 2005 Scott Baxter
Example Distance-to-Fault Plot
February, 2005 5 - 39RF100 v2.0 (c) 2005 Scott Baxter
Some Antenna Application Considerations
Some Antenna Application Considerations
Chapter 5 Section D
February, 2005 5 - 40RF100 v2.0 (c) 2005 Scott Baxter
Near-Field/Far-Field Considerations
Antenna behavior is very different close-in and far outNear-field region: the area within about 10 times the spacing between antenna’s internal elements
• Inside this region, the signal behaves as independent fields from each element of the antenna, with their individual directivity
Far-field region: the area beyond roughly 10 times the spacing between the antenna’s internal elements
• In this region, the antenna seems to be a point-source and the contributions of the individual elements are indistinguishable
• The pattern is the composite of the arrayObstructions in the near-field can dramatically alter the antenna performance
Near-field
Far-field
February, 2005 5 - 41RF100 v2.0 (c) 2005 Scott Baxter
Local Obstruction at a Site
Obstructions near the site are sometimes unavoidable Near-field obstructions can seriously alter pattern shapeMore distant local obstructions can cause severe blockage, as for example roof edge in the figure at right
• Knife-edge diffraction analysis can help estimate diffraction loss in these situations
• Explore other antenna mounting positions
Diffractionover
obstructing edge
Local obstruction example
February, 2005 5 - 42RF100 v2.0 (c) 2005 Scott Baxter
Estimating Isolation Between Antennas
Often multiple antennas are needed at a site and interaction is troublesomeElectrical isolation between antennas
• Coupling loss between isotropic antennas one wavelength apart is 22 dB
• 6 dB additional coupling loss with each doubling of separation
• Add gain or loss referenced from horizontal plane patterns
• Measure vertical separation between centers of the antennas
– vertical separation usually is very effective
One antenna should not be mounted in main lobe and near-field of another
• Typically within 10 feet @ 800 MHz• Typically 5-10 feet @ 1900 MHz
February, 2005 5 - 43RF100 v2.0 (c) 2005 Scott Baxter
Visually Estimating Depression Anglesin the field
Before considering downtilt, beamwidths, and depression angles, do some personal experimentation at a high site to gain a sense of the angles involvedVisible width of fingers, etc. can be useful approximate benchmark for visual evaluationMeasure and remember width of your own chosen referencesStanding at a site, correlate your sightings of objects you want to cover with angles in degrees and the antenna pattern
distance
width
angle = arctangent (width / distance)
Visually estimating angleswith tools always at hand
Typical AnglesThumb widthNail of forefingerAll knuckles
~2 degrees~1 degree~10 degrees
“Calibrate” yourself using the formula!
February, 2005 5 - 44RF100 v2.0 (c) 2005 Scott Baxter
Antenna DowntiltWhat’s the goal?
Downtilt is commonly used for two reasons1. Reduce Interference
• Reduce radiation toward a distant co-channel cell
• Concentrate radiation within the serving cell
2. Prevent “Overshoot”• Improve coverage of
nearby targets far below the antenna
– otherwise within “null” of antenna pattern
Are these good strategies?How is downtilt applied?
Scenario 2
Cell AScenario 1
Cell B
February, 2005 5 - 45RF100 v2.0 (c) 2005 Scott Baxter
Consider Vertical Depression Angles
Basic principle: important to match vertical pattern against intended coverage targets
• Compare the angles toward objects against the antenna vertical pattern -- what’s radiating toward the target?
• Don’t position a null of the antenna toward an important coverage target!
Sketch and formula • Notice the height and horizontal
distance must be expressed in the same units before dividing (both in feet, both in miles, etc.)
θ = ArcTAN ( Vertical distance / Horizontal distance )
Horizontaldistance
Verticaldistance
θ Depression angle
February, 2005 5 - 46RF100 v2.0 (c) 2005 Scott Baxter
Types Of Downtilt
Mechanical downtilt• Physically tilt the antenna• The pattern in front goes
down, and behind goes up• Popular for sectorization
and special omni applications
Electrical downtilt• Incremental phase shift is
applied in the feed network• The pattern “droops” all
around, like an inverted saucer
• Common technique when downtilting omni cells
February, 2005 5 - 47RF100 v2.0 (c) 2005 Scott Baxter
Reduce Interference Scenario 1
The Concept:Radiate a strong signal toward everything within the serving cell, but significantly reduce the radiation toward the area of Cell B
The Reality:When actually calculated, it’s surprising how small the difference in angle is between the far edge of cell A and the near edge of Cell B
• Delta in the example is only 0.3 degrees!!
• Let’s look at antenna patterns
Cell A ConceptCell B
weakstrong
θ1 = ArcTAN ( 150 / ( 4 * 5280 ) ) = -0.4 degrees
θ2 = ArcTAN ( 150 / ( 12 * 5280 ) ) = -0.1 degrees
Reality
12 miles4
height difference
150 ft θ2θ1
February, 2005 5 - 48RF100 v2.0 (c) 2005 Scott Baxter
Reduce InterferenceScenario 1 , Continued
It’s an attractive idea, but usually the angle between edge of serving cell and nearest edge of distant cell is just too small to exploit
• Downtilt or not, can’t get much difference in antenna radiation between θ1 and θ2
• Even if the pattern were sharp enough, alignment accuracy and wind-flexing would be problems
– delta θ in this example is less than one degree!
• Also, if downtilting -- watch out for excessive RSSI and IM involving mobiles near cell!
Soft handoff and good CDMA power control is more important
-0.4-0.1
θ1 = -0.4 degrees
θ2 = -0.1 degrees
February, 2005 5 - 49RF100 v2.0 (c) 2005 Scott Baxter
Avoid Overshoot Scenario 2
Application concern: too little radiation toward low, close-in coverage targetsThe solution is common-sense matching of the antenna vertical pattern to the angles where radiation is needed
• Calculate vertical angles to targets!!• Watch the pattern nulls -- where do
they fall on the ground?• Choose a low-gain antenna with a
fat vertical pattern if you have a wide range of vertical angles to “hit”
• Downtilt if appropriate• If needed, investigate special “null-
filled” antennas with smooth patterns
Scenario 2
February, 2005 5 - 50RF100 v2.0 (c) 2005 Scott Baxter
Other Antenna Selection Considerations
Before choosing an antenna for widespread deployment, investigate:
Manufacturer’s measured patterns• Observe pattern at low end of band, mid-band, and high end of band• Any troublesome back lobes or minor lobes in H or V patterns?• Watch out for nulls which would fall toward populated areas• Be suspicious of extremely symmetrical, “clean” measured patterns• Obtain Intermod Specifications and test results (-130 or better)• Inspect return loss measurements across the band
Inspect a sample unit• Physical integrity? weatherproof? • Dissimilar metals in contact anywhere?• Collinear vertical antennas: feed method? • End (compromise) or center-fed (best)?• Complete your own return loss measurements, if possible• Ideally, do your own limited pattern verification
Check with other users for their experiences
February, 2005 6 - 1RF100 v2.0 (c)2005 Scott Baxter
Traffic EngineeringTraffic Engineering
Chapter 6
Typical Traffic Distributionon a Cellular System
0%10%20%30%40%50%60%70%80%90%
100%
Hour
SUN
MON
TUE
WED
THU
FRI
SAT
# Trunks
Efficiency %
Capacity,Erlangs
1 50
80%
41
February, 2005 6 - 2RF100 v2.0 (c)2005 Scott Baxter
A Game of Avoiding Extremes
The traffic engineer must walk a fine line between two problems:Overdimensioning
• too much cost• insufficient resources to construct• traffic revenue is too low to
support costs• very poor economic efficiency!
Underdimensioning• blocking• poor technical performance
(interference)• capacity for billable revenue is low• revenue is low due to poor quality• users unhappy, cancel service• very poor economic efficiency!
February, 2005 6 - 3RF100 v2.0 (c)2005 Scott Baxter
Dimensioning the System:An Interactive, Iterative Process
Some traffic engineering decisions trigger resource acquisition
• additional blocks of numbers from the local exchange carrier
• additional cards for various functions in the switch and peripherals
• additional members in PSTN trunk groups; additional T-1/E-1s to busy sites
Some traffic engineering decisions trigger more engineering
• adding additional carriers to congested areas
• adding additional cells to relieve blocking• finding short-term fixes for unanticipated
problemsThis course is concerned primarily with determining the number of voice channels required in cells, with the related site engineering and frequency or code planning
DMS-MTXCell
PSTN Office
February, 2005 6 - 4RF100 v2.0 (c)2005 Scott Baxter
Basics of Traffic EngineeringTerminology & Concept of a Trunk
Traffic engineering in telephony is focused on the voice paths which users occupy. They are called by many different names:• trunks• circuits• radios (AMPS, TDMA), transceivers (“TRXs” in GSM),
channel elements (CDMA)Some other common terms are:• trunk group
– a trunk group is several trunks going to the same destination, combined and addressed in switch translations as a unit , for traffic routing purposes
• member– one of the trunks in a trunk group
February, 2005 6 - 5RF100 v2.0 (c)2005 Scott Baxter
Units of Traffic Measurement
General understanding of telephone traffic engineering began around 1910. An engineer in the Danish telephone system, Mr. Erlang, was one of the first to master the science of trunk dimensioning and publish the knowledge for others. In his honor,the basic unit of traffic is named the Erlang. An Erlang of traffic is one circuit continuously used during an observation period one hour long.
Other units have become popular among various users:CCS (Hundred-Call-Seconds)MOU (Minutes Of Use)It’s easy to convert between traffic units if the need arises:
1 Erlang = 60 MOU = 36 CCS
Traffic is expressed in units of Circuit Time
February, 2005 6 - 6RF100 v2.0 (c)2005 Scott Baxter
How Much Traffic Can One Trunk Carry?Traffic studies are usually for periods of one hourIn one hour, one trunk can carry one hour of traffic -- One ErlangIf nothing else matters, this is the limit!If anyone else wants to talk -- sorry!
Absolute Maximum Capacityof One Trunk
One Trunk
One ErlangConstantTalker
It’s not acceptable to keep all trunks busy all the time. There must be a reserve to accommodate new talkers! How much?
February, 2005 6 - 7RF100 v2.0 (c)2005 Scott Baxter
Traffic Engineering And Queuing Theory
Traffic engineering is an application of a science called queuing theory
• Queuing theory relates user arrival statistics, number of servers, and various queue strategies, with the probability of a user receiving service
• If waiting is not allowed, and a blocked call simply goes away, Erlang-Bformula applies (popular in wireless)
• If unlimited waiting is allowed before a call receives service, the Erlang-Cformula applies
• If a wait is allowed but is limited in time, Binomial & Poisson formulae apply
• Engset formulae apply to rapid, packet-like transactions such as paging channels
Ticket counter analogy
User population
Queue
Servers
Queues we face in everyday life
1) for telephone calls2) at the bank3) at the gas station4) at the airline counter
February, 2005 6 - 8RF100 v2.0 (c)2005 Scott Baxter
Offered And Carried TrafficOffered traffic is what users attempt to originateCarried traffic is the traffic actually successfully handled by the systemBlocked traffic is the traffic that could not be handled
• Since blocked call attempts never materialize, blocked traffic must be estimated based on number of blocked attempts and average duration of successful calls
CarriedTraffic
BTS BTS BTS BTS BTS BTS
OfferedTraffic
BSCMTX
BlockedTraffic
PSTN or otherWireless user
TOff = NCA x TCD
TOff = Offered trafficNCA = Number of call attemptsTCD = Average call duration
Offered Traffic = Carried Traffic + Blocked Traffic
February, 2005 6 - 9RF100 v2.0 (c)2005 Scott Baxter
Blocking is inability to get a circuit when one is neededProbability of Blocking is the likelihood that blocking will happenIn principle, blocking can occur anywhere in a wireless system:
• not enough radios, the cell is full• not enough paths between cell site and switch• not enough paths through the switching complex• not enough trunks from switch to PSTN
Blocking probability is usuallyexpressed as a percentage
using a “shorthand” notation:• P.02 is 2% probability, etc.• Blocking probability sometimes
is called “Grade Of Service”Most blocking in cellular systems
occurs at the radio level.• P.02 is a common goal at the
radio level in a system
Principles of Traffic EngineeringBlocking Probability / Grade of Service
PSTN Office
DMS-MTX
Cell
Cell
Cell
P.001 P.005
P.02
P.005
Typical Wireless SystemDesign Blocking Probabilities
February, 2005 6 - 10RF100 v2.0 (c)2005 Scott Baxter
Number of Trunks vs. Utilization Efficiency
Imagine a cell site with just one voice channel. At a P.02 Grade of Service, how much traffic could it carry?
• The trunk can only be used 2% of the time, otherwise the blocking will be worse than 2%.
• 98% availability forces 98% idleness. It can only carry .02 Erlangs. Efficiency 2%!
Adding just one trunk relieves things greatly. Now we can use trunk 1 heavily, with trunk 2 handling the overflow. Efficiency rises to 11%
The Principle of Trunking EfficiencyFor a given grade of service, trunk
utilization efficiency increases as the number of trunks in the pool grows larger.
• For trunk groups of several hundred, utilization approaches 100%.
# Trunks
Efficiency %
Capacity,Erlangs
1 50
80%
41
Erl Eff%Trks12
0.020.22
2%11%
Erlang-B P.02 GOS
February, 2005 6 - 11RF100 v2.0 (c)2005 Scott Baxter
Number of Trunks,Capacity, and Utilization Efficiency
The graph at left illustrates the capacity in Erlangs of a given number of trunks, as well as the achievable utilization efficiencyFor accurate work, tables of traffic data are available
• Capacity, Erlangs• Blocking Probability
(GOS)• Number of Trunks
Notice how capacity and utilization behave for the numbers of trunks in typical cell sites
051015202530354045
Capacity and Trunk UtilizationErlang-B for P.02 Grade of Service
Trunks
0102030405060708090
50403020100UtilizationEfficiencyPercent
Capacity,Erlangs
February, 2005 6 - 12RF100 v2.0 (c)2005 Scott Baxter
Traffic Engineering & System Dimensioning
Using Erlang-B Tables to determine Number of Circuits Required
A = f (E,n)
Probability of blocking
0.0001 0.002 0.02
7
E
n
12
300
2.935
0.2
Capacity in Erlangs
Number of available circuits
February, 2005 6 - 13RF100 v2.0 (c)2005 Scott Baxter
Erlang-B Traffic TablesAbbreviated - For P.02 Grade of Service Only
#TrunksErlangs #TrunksErlangs #Trunks #TrunksErlangs #TrunksErlangs #TrunksErlangs #TrunksErlangs #TrunksErlangs1 0.0204 26 18.4 51 41.2 76 64.9 100 88 150 136.8 200 186.2 250 235.82 0.223 27 19.3 52 42.1 77 65.8 102 89.9 152 138.8 202 188.1 300 285.73 0.602 28 20.2 53 43.1 78 66.8 104 91.9 154 140.7 204 190.1 350 335.74 1.09 29 21 54 44 79 67.7 106 93.8 156 142.7 206 192.1 400 385.95 1.66 30 21.9 55 44.9 80 68.7 108 95.7 158 144.7 208 194.1 450 436.16 2.28 31 22.8 56 45.9 81 69.6 110 97.7 160 146.6 210 196.1 500 486.47 2.94 32 23.7 57 46.8 82 70.6 112 99.6 162 148.6 212 198.1 600 587.28 3.63 33 24.6 58 47.8 83 71.6 114 101.6 164 150.6 214 200 700 688.29 4.34 34 25.5 59 48.7 84 72.5 116 103.5 166 152.6 216 202 800 789.310 5.08 35 26.4 60 49.6 85 73.5 118 105.5 168 154.5 218 204 900 890.611 5.84 36 27.3 61 50.6 86 74.5 120 107.4 170 156.5 220 206 1000 999.112 6.61 37 28.3 62 51.5 87 75.4 122 109.4 172 158.5 222 208 1100 109313 7.4 38 29.2 63 52.5 88 76.4 124 111.3 174 160.4 224 21014 8.2 39 30.1 64 53.4 89 77.3 126 113.3 176 162.4 226 21215 9.01 40 31 65 54.4 90 78.3 128 115.2 178 164.4 228 213.916 9.83 41 31.9 66 55.3 91 79.3 130 117.2 180 166.4 230 215.917 10.7 42 32.8 67 56.3 92 80.2 132 119.1 182 168.3 232 217.918 11.5 43 33.8 68 57.2 93 81.2 134 121.1 184 170.3 234 219.919 12.3 44 34.7 69 58.2 94 82.2 136 123.1 186 172.4 236 221.920 13.2 45 35.6 70 59.1 95 83.1 138 125 188 174.3 238 223.921 14 46 36.5 71 60.1 96 84.1 140 127 190 176.3 240 225.922 14.9 47 37.5 72 61 97 85.1 142 128.9 192 178.2 242 227.923 15.8 48 38.4 73 62 98 86 144 130.9 194 180.2 244 229.924 16.6 49 39.3 74 62.9 99 87 146 132.9 196 182.2 246 231.825 17.5 50 40.3 75 63.9 100 88 148 134.8 198 184.2 248 233.8
Erlangs
February, 2005 6 - 14RF100 v2.0 (c)2005 Scott Baxter
The Equation behind the Erlang-B Table
Pn(A) =
An
n!
1 + + ... +A1!
An
n!
Pn(A) = Blocking Rate (%)with n trunksas function of traffic A
A = Traffic (Erlangs)n = Number of Trunks
Offered Traffic lost due to blocking
Numberof
Trunks
time
max # oftrunks
average# of busychannelsOffered
Traffic,A
The Erlang-B formula is fairly simple to implement on hand-held programmable calculators, in spreadsheets, or popular programming languages.
February, 2005 6 - 15RF100 v2.0 (c)2005 Scott Baxter
Wireless Traffic Variation with Time:A Cellular Example
Peak traffic on cellular systems is usually daytime business-related traffic; on PCS systems, evening traffic becomes much more important and may actually contain the system busy hourEvening taper is more gradual than morning riseWireless systems for PCS and LEC-displacement have peaks of residential traffic during early evening hours, like wirelinesystemsFriday is the busiest day, followed by other weekdays in backwards order, then Saturday, then SundayThere are seasonal and annual variations, as well as long term growth trends
Typical Traffic Distributionon a Cellular System
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Hour
SUN
MON
TUE
WED
THU
FRI
SAT
Actual traffic from a cellular system in the mid-south USA in summer 1992. This system had 45 cells and served an area of approximately 1,000,000 population.
February, 2005 6 - 16RF100 v2.0 (c)2005 Scott Baxter
Busy-Hour
In telephony, it is customary to collect and analyze traffic in hourly blocks, and to track trends over months, quarters, and years
• When making decisions about number of trunks required, we plan the trunks needed to support the busiest hour of a normalday
• Special events (disasters, one-of-a-kind traffic tie-ups, etc.) are not considered in the analysis (unless a marketing-sponsored event)
Which Hour should be used as the Busy-Hour?• Some planners choose one specific hour and use it every day• Some planners choose the busiest hour of each individual day
(“floating busy hour”)• Most common preference is to use “floating (bouncing)” busy
hour determined individually for the total system and for each cell, but to exclude special events and disasters
• In the example just presented, 4 PM was the busy hour every day
February, 2005 6 - 17RF100 v2.0 (c)2005 Scott Baxter
Wireline telephone systems have a big advantage in traffic planning.
• They know the addresses where their customers generate the traffic!
Wireless systems have to guess where the customers will be next
• on existing systems, use measured traffic data by sector and cell
– analyze past trends
– compare subscriber forecast
– trend into future, find overloads
• for new systems or new cells, we must use all available clues
11 711
1019
85 7
652
73
8 167 166
99
7
Existing SystemTraffic In Erlangs
Where is the Traffic?
February, 2005 6 - 18RF100 v2.0 (c)2005 Scott Baxter
Traffic Clues
Subscriber Profiles: • Busy Hour Usage, Call Attempts, etc.
Market Penetration: • # Subscribers/Market Population• use Sales forecasts, usage forecasts
Population Density• Geographic Distribution
Construction ActivityVehicular Traffic Data
• Vehicle counts on roads• Calculations of density on major
roadways from knowledge of vehicle movement, spacing, market penetration
Land Use Database: Area ProfilesAerial Photographs: Count Vehicles!
22,100
3620 66201230
51104215
920
Vehicular Traffic
Land UseDatabases
Population Density
27 mE/Sub in BH
103,550 Subscribers1,239,171 Market Population
adding 4,350 subs/month
new Shopping Center
February, 2005 6 - 19RF100 v2.0 (c)2005 Scott Baxter
Traffic Density Along RoadwaysNumber of lanes and speed are the main variable determining number of vehicles on major highways
• Typical headway ~1.5 seconds• Table and figure show capacity of 1
lane When traffic stops, users generally increase calling activityMultiply number of vehicles by percentage penetration of population to estimate number of subscriber vehicles
Vehicle Speed,MPH
Vehicle Spacing,
feet
Vehicles per mile,per lane
0 20 26410 42 12620 64 8330 86 6145 119 4460 152 35
Vehicle spacing 20 ft. @stopRunning Headway 1.5 seconds
Vehicles per mile
Vehicle Spacing At Common Roadway Speeds0
50 MPH40 MPH30 MPH20 MPH10 MPH0 MPH
100 200 300 400 500 600 700 800 feet
February, 2005 6 - 20RF100 v2.0 (c)2005 Scott Baxter
Methodical Estimation of Required Trunks
Modern propagation prediction tools allow experimentation and estimation of traffic levelsEstimate total overall traffic from subscriber forecastsForm traffic density outlines from market knowledge, forecastsOverlay traffic density on land use data; weight by land useAccumulate intercepted traffic into serving cells,
• obtain Erlangs per cell & sector
From tables, determine number of trunks required per cell/sectorModern software tools automate major parts of this process
Cell Grid
Land Use
TrafficDensity 3.5%
27mE
February, 2005 6 - 21RF100 v2.0 (c)2005 Scott Baxter
Determining Number of Trunksrequired for a new Growth Cell
When new growth cells are added, they absorb some of the traffic formerly carried by surrounding cellsTwo approaches to estimating traffic on the new cell and on its older neighbors:
• if blocking was not too severe, you can estimate redistributed traffic in the area based on the new division of coverage
• if blocking is severe, (often the case), users will stop trying to call in locations where they’ve learned to expect blocking. Users are self-programming!!
– reapply basic traffic assumptions in the area, like engineering new system, for every nearby cell
– watch out! overall traffic in the area may increase to fill the additional capacity and the new cell itself may block as soon as it goes in service
February, 2005 6 - 22RF100 v2.0 (c)2005 Scott Baxter
Dimensioning System Administrative Functions
System administrative functions also require traffic engineering input. While these functions are not necessarily performed by the RF engineer, they require RF awareness and understanding.Paging
• The paging channel has a definite capacity which must not be exceeded. When occupancy approaches this limit, the system mustbe divided into zones, and zone paging implemented.
• Impact of Short Message Service (and others) must be consideredAutonomous Registration
• Autonomous registration involves numerous parameters and the registration attempts must be monitored and controlled to avoid overloading.
February, 2005 7 - 1RF100 v2.0 (c) 2005 Scott Baxter
Technical Introduction to CDMA
Technical Introduction to CDMA
Course RF100 Chapter 7
February, 2005 7 - 2RF100 v2.0 (c) 2005 Scott Baxter
Course Outline
Basic CDMA Principles• Coding• Forward and Reverse Channels
CDMA Operational Details• Multiplexing, Forward and Reverse Power Control
CDMA Handset ArchitectureCDMA HandoffsCDMA Network ArchitectureCDMA Messaging and Call FlowOptional TopicsWireless Multiple Access TechnologiesOverview of Current Technologies
• Capacity; CDMA Overlays, Spectrum Clearing
February, 2005 7 - 3RF100 v2.0 (c) 2005 Scott Baxter
Section A
How Does CDMA Work?Introduction to Basic Principles
How Does CDMA Work?Introduction to Basic Principles
February, 2005 7 - 4RF100 v2.0 (c) 2005 Scott Baxter
CDMA: Using A New Dimension
All CDMA users occupy the same frequency at the same time! Frequency and time are not used as discriminatorsCDMA operates by using CODING to discriminate between usersCDMA interference comes mainly from nearby usersEach user is a small voice in a roaring crowd -- but with a uniquely recoverable code
CDMA
Figure of Merit: C/I(carrier/interference ratio)
AMPS: +17 dBTDMA: +14 to +17 dB
GSM: +7 to 9 dB.CDMA: -10 to -17 dB.CDMA: Eb/No ~+6 dB.
February, 2005 7 - 5RF100 v2.0 (c) 2005 Scott Baxter
Two Types of CDMA
There are Two types of CDMA:Frequency-Hopping
• Each user’s narrowband signal hops among discrete frequencies, and the receiver follows in sequence
• Frequency-Hopping Spread Spectrum (FHSS) CDMA is NOTcurrently used in wireless systems, although used by the military
Direct Sequence• narrowband input from a user is
coded (“spread”) by a user-unique broadband code, then transmitted
• broadband signal is received; receiver knows, applies user’s code, recovers users’ data
• Direct Sequence Spread Spectrum(DSSS) CDMA IS the method used in IS-95 commercial systems
User 1
Code 1
Composite
Time Frequency
+=
Direct Sequence CDMA
User 1 User 2 User 3 User 4 Frequency Hopping CDMA
User 3 User 4 User 1 unused User 2
User 1 User 4 User 3 User 2 unused
Frequency
unused User 1 User 2 User 4 User 3
February, 2005 7 - 6RF100 v2.0 (c) 2005 Scott Baxter
DSSS Spreading: Time-Domain View
At Originating Site:Input A: User’s Data @ 19,200 bits/secondInput B: Walsh Code #23 @ 1.2288 McpsOutput: Spread spectrum signal
At Destination Site:Input A: Received spread spectrum signalInput B: Walsh Code #23 @ 1.2288 McpsOutput: User’s Data @ 19,200 bits/second just as originally sent Drawn to actual scale and time alignment
via air interface
XORExclusive-OR
Gate
1
1
Input A: Received Signal
Input B: Spreading Code
Output: User’s Original Data
Input A: User’s Data
Input B: Spreading Code
Spread Spectrum Signal
XORExclusive-OR
Gate
Originating Site
Destination Site
February, 2005 7 - 7RF100 v2.0 (c) 2005 Scott Baxter
Spreading from a Frequency-Domain View
Traditional technologies try to squeeze signal into minimum required bandwidthCDMA uses larger bandwidth but uses resulting processing gain to increase capacity
Spread Spectrum Payoff:Processing Gain
Spread SpectrumTRADITIONAL COMMUNICATIONS SYSTEM
SlowInformation
SentTX
SlowInformationRecovered
RX
NarrowbandSignal
SPREAD-SPECTRUM SYSTEM
FastSpreadingSequence
SlowInformation
SentTX
SlowInformationRecovered
RX
FastSpreadingSequence
WidebandSignal
February, 2005 7 - 8RF100 v2.0 (c) 2005 Scott Baxter
The CDMA Spread Spectrum Payoff:Would you like a lump-sum, or monthly payments?
Shannon's work suggests that a certain bit rate of information deserves a certain bandwidthIf one CDMA user is carried alone by a CDMA signal, the processing gain is large - roughly 21 db for an 8k vocoder.
• Each doubling of the number of users consumes 3 db of the processing gain
• Somewhere above 32 users, the signal-to-noise ratio becomes undesirable and the ultimate capacity of the sector is reached
Practical CDMA systems restrict the number of users per sector to ensure processing gain remains at usable levels
# Users Processing Gain1 21 db
2 18 db
4 15 db
8 12 db
16 9 db
32 6 db
64…..Uh, Regis, can I justtake the money I've already
won, and go home now?
CDMA Spreading Gain
Consider a user with a 9600 bps vocoder talking on a
CDMA signal 1,228,800 hzwide. The processing gain is 1,228,800/9600 = 128, which
is 21 db. What happens if additional users are added?
February, 2005 7 - 9RF100 v2.0 (c) 2005 Scott Baxter
CDMA Uses Code Channels
A CDMA signal uses many chips to convey just one bit of information Each user has a unique chip pattern, in effect a code channelTo recover a bit, integrate a large number of chips interpreted by the user’s known code patternOther users’ code patterns appear random and integrate in a random self-canceling fashion, don’t disturb the bit decoding decision being made with the proper code pattern
Building aBuilding aCDMA SignalCDMA Signal
Bitsfrom User’s Vocoder
Symbols
Chips
Forward Error Correction
Coding and Spreading
February, 2005 7 - 10RF100 v2.0 (c) 2005 Scott Baxter
CDMA: The Code “Magic” “behind the Veil”
Σ
if 1 =if 0 =
1
AnalogSummingUsers
QPSK RF
Σ
DemodulatedReceived
CDMA SignalDespreading Sequence(Locally Generated, =0)
matchesopposite
Decision:
Matches!( = 0 )
TimeIntegration
1
Opposite( =1)
+10
-26
Received energy: Correlation
-16
BTS
This figure illustrates the basic technique of CDMA signal generation and recovery.The actual coding process used in IS-95 CDMA includes a few additional layers, as we’ll see in following slides.
February, 2005 7 - 11RF100 v2.0 (c) 2005 Scott Baxter
Spreading: What we do, we can undo
Sender combines data with a fast spreading sequence, transmits spread data streamReceiver intercepts the stream, uses same spreading sequence to extract original data
ORIGINATING SITE DESTINATION
SpreadingSequence
SpreadingSequence
InputData
RecoveredData
Spread Data Stream
February, 2005 7 - 12RF100 v2.0 (c) 2005 Scott Baxter
“Shipping and Receiving” via CDMA
Whether in shipping and receiving, or in CDMA, packaging is extremely important!Cargo is placed inside “nested” containers for protection and to allow addressingThe shipper packs in a certain order, and the receiver unpacks in the reverse orderCDMA “containers” are spreading codes
FedE
x
Data Mailer
FedE
x
DataMailer
Shipping Receiving
February, 2005 7 - 13RF100 v2.0 (c) 2005 Scott Baxter
CDMA’s Nested Spreading Sequences
CDMA combines three different spreading sequences to create unique, robust channelsThe sequences are easy to generate on both sending and receivingends of each link“What we do, we can undo”
SpreadingSequence
ASpreadingSequence
BSpreadingSequence
CSpreadingSequence
CSpreadingSequence
BSpreadingSequence
A
InputDataX
RecoveredDataX
X+A X+A+B X+A+B+C X+A+B X+ASpread-Spectrum Chip Streams
ORIGINATING SITE DESTINATION
February, 2005 7 - 14RF100 v2.0 (c) 2005 Scott Baxter
One of the CDMA Spreading Sequences:Walsh Codes
64 “Magic” Sequences, each 64 chips longEach Walsh Code is precisely Orthogonal with respect to all other Walsh Codes
• it’s simple to generate the codes, or• they’re small enough to use from ROM
WALSH CODES# ---------------------------------- 64-Chip Sequence ------------------------------------------0 00000000000000000000000000000000000000000000000000000000000000001 01010101010101010101010101010101010101010101010101010101010101012 00110011001100110011001100110011001100110011001100110011001100113 01100110011001100110011001100110011001100110011001100110011001104 00001111000011110000111100001111000011110000111100001111000011115 01011010010110100101101001011010010110100101101001011010010110106 00111100001111000011110000111100001111000011110000111100001111007 01101001011010010110100101101001011010010110100101101001011010018 00000000111111110000000011111111000000001111111100000000111111119 0101010110101010010101011010101001010101101010100101010110101010
10 001100111100110000110011110011000011001111001100001100111100110011 011001101001100101100110100110010110011010011001011001101001100112 000011111111000000001111111100000000111111110000000011111111000013 010110101010010101011010101001010101101010100101010110101010010114 001111001100001100111100110000110011110011000011001111001100001115 011010011001011001101001100101100110100110010110011010011001011016 000000000000000011111111111111110000000000000000111111111111111117 010101010101010110101010101010100101010101010101101010101010101018 001100110011001111001100110011000011001100110011110011001100110019 011001100110011010011001100110010110011001100110100110011001100120 000011110000111111110000111100000000111100001111111100001111000021 010110100101101010100101101001010101101001011010101001011010010122 001111000011110011000011110000110011110000111100110000111100001123 011010010110100110010110100101100110100101101001100101101001011024 000000001111111111111111000000000000000011111111111111110000000025 010101011010101010101010010101010101010110101010101010100101010126 001100111100110011001100001100110011001111001100110011000011001127 011001101001100110011001011001100110011010011001100110010110011028 000011111111000011110000000011110000111111110000111100000000111129 010110101010010110100101010110100101101010100101101001010101101030 001111001100001111000011001111000011110011000011110000110011110031 011010011001011010010110011010010110100110010110100101100110100132 000000000000000000000000000000001111111111111111111111111111111133 010101010101010101010101010101011010101010101010101010101010101034 001100110011001100110011001100111100110011001100110011001100110035 011001100110011001100110011001101001100110011001100110011001100136 000011110000111100001111000011111111000011110000111100001111000037 010110100101101001011010010110101010010110100101101001011010010138 001111000011110000111100001111001100001111000011110000111100001139 011010010110100101101001011010011001011010010110100101101001011040 000000001111111100000000111111111111111100000000111111110000000041 010101011010101001010101101010101010101001010101101010100101010142 001100111100110000110011110011001100110000110011110011000011001143 011001101001100101100110100110011001100101100110100110010110011044 000011111111000000001111111100001111000000001111111100000000111145 010110101010010101011010101001011010010101011010101001010101101046 001111001100001100111100110000111100001100111100110000110011110047 011010011001011001101001100101101001011001101001100101100110100148 000000000000000011111111111111111111111111111111000000000000000049 010101010101010110101010101010101010101010101010010101010101010150 001100110011001111001100110011001100110011001100001100110011001151 011001100110011010011001100110011001100110011001011001100110011052 000011110000111111110000111100001111000011110000000011110000111153 010110100101101010100101101001011010010110100101010110100101101054 001111000011110011000011110000111100001111000011001111000011110055 011010010110100110010110100101101001011010010110011010010110100156 000000001111111111111111000000001111111100000000000000001111111157 010101011010101010101010010101011010101001010101010101011010101058 001100111100110011001100001100111100110000110011001100111100110059 011001101001100110011001011001101001100101100110011001101001100160 000011111111000011110000000011111111000000001111000011111111000061 010110101010010110100101010110101010010101011010010110101010010162 001111001100001111000011001111001100001100111100001111001100001163 0110100110010110100101100110100110010110011010010110100110010110
EXAMPLE:Correlation of Walsh Code #23 with Walsh Code #59
#23 0110100101101001100101101001011001101001011010011001011010010110#59 0110011010011001100110010110011010011001011001100110011010011001Sum 0000111111110000000011111111000011110000000011111111000000001111
Correlation Results: 32 1’s, 32 0’s: Orthogonal!!
Unique Properties:Mutual Orthogonality
February, 2005 7 - 15RF100 v2.0 (c) 2005 Scott Baxter
Other Sequences: Generation & Properties
Other CDMA sequences are generated in shift registersPlain shift register: no fun, sequence = length of registerTapped shift register generates a wild, self-mutating sequence 2N-1 chips long (N=register length)
• Such sequences match if compared in step (no-brainer, any sequence matches itself)
• Such sequences appear approximately orthogonal if compared with themselves not exactly matched in time
• false correlation typically <2%
A Tapped, Summing Shift Register
Sequence repeats every 2N-1 chips,where N is number of cells in register
An Ordinary Shift Register
Sequence repeats every N chips,where N is number of cells in register
A Special Characteristic of SequencesGenerated in Tapped Shift Registers
Compared In-Step: Matches Itself
Complete Correlation: All 0’sSum:Self, in sync:
Sequence:
Compared Shifted: Little Correlation
Practically Orthogonal: Half 1’s, Half 0’sSum:Self, Shifted:
Sequence:
February, 2005 7 - 16RF100 v2.0 (c) 2005 Scott Baxter
Original IS-95 CDMA PN Scrambling
Short PN Scrambling
New CDMA2000 1x Complex Scrambling
Another CDMA Spreading Sequence:The Short PN Code, used for Scrambling
The short PN code consists of two PN Sequences, I and Q, each 32,768 chips long
• Generated in similar but differently-tapped 15-bit shift registers
• the two sequences scramble the information on the I and Q phase channels
Figures to the right show how one user’s channel is built at the bTS
IQ
32,768 chips long26-2/3 ms.
(75 repetitions in 2 sec.)Σ
RF: cos ωt
RF: sin ωt
user’ssymbols
QPSK-modulated
RFOutput
Same information duplicatedon I and Q
Walsh
I-sequence
Q-sequence
Σ
RF:cos ωt
sin ωtRF
user’ssymbols
QPS
K
Out
put
Walsh
Seria
l to
Para
llel
Σ
Σ
+
DifferentInformationon I and Q
Complex Scrambling
I-sequence
Q-sequence
-+
+
February, 2005 7 - 17RF100 v2.0 (c) 2005 Scott Baxter
Generating the PN Long Codeat a desired Timing Offset
Every phone and every BTS channel element has a Long Code generator• Long Code State Register makes long code at system reference timing• A Mask Register holds a user-specific unique pattern of bits
Each clock pulse drives the Long Code State Register to its next state• State register and Mask register contents are added in the Summer• Summer contents are modulo-2 added to produce just a single bit output
The output bits are the Long Code, but shifted to the user’s unique offset
LONG CODE STATE REGISTER dynamic contents, zero timing shift
MASK REGISTER unique steady contents cause unique timing shift
SUMMER holds dynamic modulo-2 sum of LC State and Mask registers
Each clock cycle, all the Summer bits are added into a single-bit modulo-2 sum
The shifted Long Code emerges, chip by chip!
clock
February, 2005 7 - 18RF100 v2.0 (c) 2005 Scott Baxter
Different Masks ProduceDifferent Long PN Offsets
Ordinary mobiles use their ESNs and the Public Long Code Mask to produce their unique Long Code PN offsets
• main ingredient: mobile ESNMobiles needing greater privacy use the Private Long Code Mask
• instead of 32-bit ESN, the mask value is produced from SSD Word B in a calculation similar to authentication
Each BTS sector has an Access Channel where mobiles transmit for registration and call setup
• the Access Channel Long Code Mask includes Access Channel #, Paging Channel #, BTS ID, and Pilot PN
• The BTS transmits all of these parameters on the Paging Channel
fixed AC# PC# BASE_ID PILOT PN
LONG CODE STATE REGISTER
SUMMING REGISTER
LONG CODE STATE REGISTER
SUMMING REGISTER
fixed PERMUTED ESN
LONG CODE STATE REGISTER
SUMMING REGISTER
calculated PRIVATE LONG CODE MASK
ACCESS CHANNEL (IDLE MODE)USING THE ACCESS CHANNEL LONG CODE MASK
TRAFFIC CHANNEL – NORMALUSING THE PUBLIC LONG CODE MASK
TRAFFIC CHANNEL – PRIVATEUSING THE PRIVATE LONG CODE MASK
February, 2005 7 - 19RF100 v2.0 (c) 2005 Scott Baxter
Putting it All Together: CDMA Channels
The three spreading codes are used in different ways to create the forward and reverse linksA forward channel exists by having a specific Walsh Code assigned to the user, and a specific PN offset for the sectorA reverse channel exists because the mobile uses a specific offset of the Long PN sequence
BTS
WALSH CODE: Individual UserSHORT PN OFFSET: Sector
LONG CODE OFFSET: individual handset
FORWARD CHANNELS
REVERSE CHANNELS
LONG CODE:Data
Scrambling
WALSH CODES:used as symbolsfor robustness
SHORT PN:used at 0 offset
for tracking
OneSector
February, 2005 7 - 20RF100 v2.0 (c) 2005 Scott Baxter
Section B
IS-95 CDMA Forward and Reverse Channels
IS-95 CDMA Forward and Reverse Channels
February, 2005 7 - 21RF100 v2.0 (c) 2005 Scott Baxter
How a BTS Builds the Forward Code Channels
BSC orAccess Manager
BTS (1 sector)
FECWalsh #1
Sync FECWalsh #32
FECWalsh #0
FECWalsh #12
FECWalsh #27
FECWalsh #44
Pilot
Paging
Vocoder
Vocoder
Vocoder
Vocoder
more more
Short PN CodePN Offset 246
Trans-mitter,
Sector X
Switch
more
a Channel Element
A Forward Channel is identified by:its CDMA RF carrier Frequencythe unique Short Code PN Offset of the sectorthe unique Walsh Code of the user
FECWalsh #23
ΣQ
ΣI
x
x+
cos ωt
sin ωt
I Q
February, 2005 7 - 22RF100 v2.0 (c) 2005 Scott Baxter
Functions of the CDMA Forward Channels
PILOT: WALSH CODE 0• The Pilot is a “structural beacon” which
does not contain a character stream. It is a timing source used in system acquisition and as a measurement device during handoffs
SYNC: WALSH CODE 32• This carries a data stream of system
identification and parameter information used by mobiles during system acquisition
PAGING: WALSH CODES 1 up to 7• There can be from one to seven paging
channels as determined by capacity needs. They carry pages, system parameters information, and call setup orders
TRAFFIC: any remaining WALSH codes• The traffic channels are assigned to
individual users to carry call traffic. All remaining Walsh codes are available, subject to overall capacity limited by noise
Pilot Walsh 0
Walsh 19
Paging Walsh 1Walsh 6
Walsh 11
Walsh 20Sync Walsh 32
Walsh 42
Walsh 37Walsh 41
Walsh 56Walsh 60
Walsh 55
February, 2005 7 - 23RF100 v2.0 (c) 2005 Scott Baxter
Code Channels in the Reverse DirectionBSC, CBSC,Access
Manager
Switch BTS (1 sector)
Channel Element
Access Channels
Vocoder
Vocoder
Vocoder
Vocoder
more more
Receiver,Sector X
A Reverse Channel is identified by:its CDMA RF carrier Frequencythe unique Long Code PN Offsetof the individual handset
Channel Element
Channel Element
Channel Element
Long Code Gen
Long Code Gen
Long Code Gen
Long Code Gen
more
a Channel Element
LongCodeoffset Long
Codeoffset Long
Codeoffset
LongCodeoffset
LongCodeoffset
LongCodeoffset
Channel Element
Long Code Gen
February, 2005 7 - 24RF100 v2.0 (c) 2005 Scott Baxter
REG
1-800242
4444
BTS
Although a sector can have up to seven paging channels, and each paging channel can have up to 32 access channels, nearly all systems today use only one paging
channel per sector and only one access channel per paging channel.
Functions of the CDMA Reverse ChannelsThere are two types of CDMA Reverse Channels:
TRAFFIC CHANNELS are used by individual users during their actual calls to transmit traffic to the BTS
• a reverse traffic channel is really just a user-specific public or private Long Code mask
• there are as many reverse Traffic Channels as there are CDMA phones in the world!
ACCESS CHANNELS are used by mobiles not yet in a call to transmit registration requests, call setup requests, page responses, order responses, and other signaling information
• an access channel is really just a public long code offset unique to the BTS sector
• Access channels are paired to Paging Channels. Each paging channel can have up to 32 access channels.
February, 2005 7 - 25RF100 v2.0 (c) 2005 Scott Baxter
Summing Up Original IS-95 CDMA Channels
Existing IS-95A/JStd-008 CDMA uses the channels above for call setup and traffic channels – all call processing transactions use these channels
• traffic channels are 9600 bps (rate set 1) or 14400 bps (rate set 2)IS-2000 CDMA is backward-compatible with IS-95, but offers additional radio configurations and additional kinds of possible channels
• These additional modes are called Radio Configurations• IS-95 Rate Set 1 and 2 are IS-2000 Radio Configurations 1 & 2
FORWARD CHANNELS
BTS
W0: PILOT
W32: SYNC
W1: PAGING
Wn: TRAFFIC
REVERSE CHANNELS
ACCESS
TRAFFIC
February, 2005 7 - 26RF100 v2.0 (c) 2005 Scott Baxter
The Channels at Phase One 1xRTT Launch
CDMA2000 1xRTT has a rich variety of traffic channels for voice and fast dateThere are also optional additional control channels for more effective operation
Includes PowerControl Subchannel
Enhanced Access Channel
CommonControl Channel
DedicatedControl Channel
Reverse FundamentalChannel (IS95B comp.)
Reverse Supplemental Channel
Access Channel(IS-95B compatible)
R-TRAFFIC
REVERSE CHANNELS
R-Pilot
R-CCCH
R-DCCH
R-FCH
R-SCH
R-EACH
1
1
0 or 1
0 or 1
0 to 2
R-ACH or
1
BTS
Dedicated Control Channel
Same coding as IS-95B,Backward compatible
Same coding as IS-95B,Backward compatible
Same coding as IS-95B,Backward compatible
Broadcast Channel
Quick Paging Channel
Common Power Control Channel
Common Assignment Channel
Common Control Channels
Forward Traffic Channels
Fundamental Channel
SupplementalChannels IS-95B only
SupplementalChannels RC3,4,5
F-TRAFFIC
FORWARD CHANNELS
F-Pilot
F-Sync
PAGING
F-BCH
F-QPCH
F-CPCCH
F-CACH
F-CCCH
F-DCCH
1
1
1 to 7
0 to 8
0 to 3
0 to 4
0 to 7
0 to 7
0 or 1
F-FCH
F-SCH
F-SCH
1
0 to 7
0 to 2
IS-95B only
Users:Users:0 to many0 to many
How manyPossible:
See Course 332 for more details.
February, 2005 7 - 27RF100 v2.0 (c) 2005 Scott Baxter
Basic CDMA Network Architecture
Access Manageror (C)BSC
Switch BTS
Ch. Card ACC
Σα
Σβ
Σχ
TFU1
GPSRBSM
CDSU
CDSU
SBSVocodersSelectors
CDSU
CDSU
CDSU
CDSU
CDSU
CMSLM
LPP LPPENET
DTCs
DMS-BUS
TxcvrA
TxcvrB
TxcvrC
RFFEA
RFFEB
RFFEC
TFU
GPSR
GPS GPS
IOC
PSTN
CDSU DISCOCDSU
DISCO 1
DISCO 2
DS0 in T1Packets
ChipsRFChannel
ElementVocoder
February, 2005 7 - 28RF100 v2.0 (c) 2005 Scott Baxter
Forward Traffic Channel: Generation Details from IS-95
Walshfunction
PowerControl
Bit
I PN
9600 bps4800 bps2400 bps1200 bps
or14400 bps7200 bps3600 bps1800 bps
(From Vocoder)
ConvolutionalEncoding and
Repetition SymbolPuncturing(13 kb only)
1.2288 McpsLong PN Code
Generation
19.2ksps
800 Hz
R = 1/2
Q PNDecimator Decimator
User AddressMask
(ESN-based)
19.2ksps
1.2288 Mcps
Scrambling
bits symbols chips
19.2ksps
28.8ksps
CHANNEL ELEMENT
MUX
BlockInterleaving
February, 2005 7 - 29RF100 v2.0 (c) 2005 Scott Baxter
Reverse Traffic Channel: Generation Details from IS-95
9600 bps4800 bps2400 bps1200 bps
or 14400 bps7200 bps3600 bps1800 bps
28.8ksps
R = 1/3
1.2288McpsUser Address
MaskLong
PN CodeGenerator
28.8ksps Orthogonal
ModulationData Burst
Randomizer
307.2kcps
1.2288Mcps
Q PN(no offset)
I PN(no offset)
D
1/2 PNChipDelay
DirectSequenceSpreading
R = 1/2
ConvolutionalEncoder &Repetition
BlockInterleaver
February, 2005 7 - 30RF100 v2.0 (c) 2005 Scott Baxter
Section C
IS-95 Operational DetailsVocoding, Multiplexing, Power Control
IS-95 Operational DetailsVocoding, Multiplexing, Power Control
February, 2005 7 - 31RF100 v2.0 (c) 2005 Scott Baxter
Variable Rate Vocoding & Multiplexing
Vocoders compress speech, reduce bit rate, greatly increasing capacityCDMA uses a superior Variable Rate Vocoder
• full rate during speech• low rates in speech pauses• increased capacity• more natural sound
Voice, signaling, and user secondary data may be mixed in CDMA frames
DSP QCELP VOCODER
Codebook
PitchFilter
FormantFilter
Coded Result Feed-back
20ms Sample
Frame Sizesbits
Full Rate Frame1/2 Rate Frame1/4 Rt.1/824/36
48/7296/144
192/288
Frame Contents: can be a mixture ofPrimaryTraffic(Voice or
data)
Signaling(System
Messaging)
Secondary(On-Air
activation, etc)
February, 2005 7 - 32RF100 v2.0 (c) 2005 Scott Baxter
How Power Control Works
800 Power Control Bits per second!
TX RF Digital
BTSBSC
Eb/NoSetpoint
Bad FER?Raise Setpoint
Stronger thansetpoint?
OpenLoop Closed
LoopReverse Link
REVERSE LINK POWER ADJUSTMENT
RX RF Digital
IS-95, 1xRTTALL SAME METHOD
TXPO = -(RXdbm) -C + TXGA
MOBILE
FEI Bits Mark Bad Frames Received
BSCSyncPilot
Paging
Short PN
Trans-mitter,
Sector XΣ I QUser 1User 2User 3
Voc-oder
BTS (1 sector)
Forward Link
FORWARD LINK POWER ADJUSTMENT
Selec-tor
MOBILE
Eb/NoSetpoint
FEI Bits
Bad FrameCounterPMRM POWER MEAS. REPORT MSG “2 bad in last 4, Help!!”
POWER CONTROL BITSTREAM RIDING ON MOBILE PILOT
DGU
IS-95 RS1Method
IS-95 RS2Method1xRTTMethod
February, 2005 7 - 33RF100 v2.0 (c) 2005 Scott Baxter
Details of Reverse Link Power Control
TXPO Handset Transmit Power• Actual RF power output of the
handset transmitter, including combined effects of open loop power control from receiver AGC and closed loop power control by BTS
• can’t exceed handset’s maximum (typ. +23 dBm)
TXGA Transmit Gain Adjust• Sum of all closed-loop
power control commands from the BTS since the beginning of this call
TXPODUP x ≈ IF
LNA
Subscriber Handset
R
R
R
S
Rake
Σ ViterbiDecoder
Vocoder
∼
FECOrthMod
Long PN
xx
xIF Mod
I
Q
x ~LO Open Loop
LO
Closed Loop Pwr Ctrl
IF
Receiver>>
<<Transmitter
PA
BTS
Typical TXPO:+23 dBm in a coverage hole0 dBm near middle of cell-50 dBm up close to BTS
0 dB
-10 dB
-20 dB
Typical Transmit Gain Adjust
Time, Seconds
TXPO = -(RXdbm) -C + TXGAC = +73 for 8K vocoder systems= +76 for 13K vocoder systems
February, 2005 7 - 34RF100 v2.0 (c) 2005 Scott Baxter
Section D
A Quick Introduction to CDMA Messages and Call Processing
A Quick Introduction to CDMA Messages and Call Processing
February, 2005 7 - 35RF100 v2.0 (c) 2005 Scott Baxter
Messages in CDMA
In CDMA, most call processing events are driven by messagesSome CDMA channels exist for the sole purpose of carrying messages; they never carry user’s voice traffic
• Sync Channel (a forward channel)• Paging Channel (a forward channel)• Access Channel (a reverse channel)• On these channels, there are only messages, continuously all
of the timeSome CDMA channels exist just to carry user traffic
• Forward Traffic Channel• Reverse Traffic Channel• On these channels, most of the time is filled with traffic and
messages are sent only when there is something to doAll CDMA messages have very similar structure, regardless of thechannel on which they are sent
February, 2005 7 - 36RF100 v2.0 (c) 2005 Scott Baxter
How CDMA Messages are Sent
CDMA messages on both forward and reverse traffic channels are normally sent via dim-and-burstMessages include many fields of binary dataThe first byte of each message identifies message type: this allows the recipient to parse the contentsTo ensure no messages are missed, all CDMA messages bear serial numbers and important messages contain a bit requesting acknowledgmentMessages not promptly acknowledged are retransmitted several times. If not acknowledged, the sender may release the callField data processing tools capture and display the messages for study
MSG_TYPE (‘00000110’)
ACK_SEQ
MSG_SEQ
ACK_REQ
ENCRYPTION
ERRORS_DETECTED
POWER_MEAS_FRAMES
LAST_HDM_SEQ
NUM_PILOTS
PILOT_STRENGTH
RESERVED (‘0’s)
8
3
3
1
2
5
10
2
4
6
0-7
NUM_PILOTS occurrences of this field:
Field Length (in bits)
EXAMPLE: A POWER MEASUREMENT
REPORT MESSAGE
t
February, 2005 7 - 37RF100 v2.0 (c) 2005 Scott Baxter
Message Vocabulary: Acquisition & Idle StatesSync Channel
Sync Channel Msg
Pilot Channel
No Messages
Paging Channel
Access Parameters Msg
System Parameters Msg
CDMA Channel List Msg
Extended SystemParameters Msg
Extended NeighborList Msg
Global ServiceRedirection Msg
Order Msg•Base Station Acknowledgment
•Lock until Power-Cycled• Maintenance required
many others…..
AuthenticationChallenge Msg
Status Request Msg
Feature Notification Msg
TMSI Assignment Msg
Channel AssignmentMsg
SSD Update Msg
Service Redirection Msg
General Page Msg
Null Msg Data Burst Msg
Access Channel
Registration Msg
Order Msg• Mobile Station Acknowldgment• Long Code Transition Request
• SSD Update Confirmationmany others…..
Origination Msg
Page Response Msg
Authentication ChallengeResponse Msg
Status Response Msg
TMSI AssignmentCompletion Message
Data Burst Msg
BTS
February, 2005 7 - 38RF100 v2.0 (c) 2005 Scott Baxter
Message Vocabulary: Conversation State
Reverse Traffic Channel
Order Message• Mobile Sta. Acknowledgment
•Long Code Transition Request
• SSD Update Confirmation• Connect
Authentication ChallengeResponse Msg
Flash WithInformation Msg
Data Burst Message
Pilot StrengthMeasurement Msg
Power MeasurementReport Msg
Send Burst DTMF Msg
OriginationContinuation Msg
Handoff Completion Msg
Parameters ResponseMessage
Service Request Msg
Service Response Msg
Service ConnectCompletion Message
Service Option ControlMessage
Status Response Msg
TMSI AssignmentCompletion Message
Forward Traffic ChannelOrder Msg
• Base Station Acknowledgment • Base Station Challenge
Confirmation• Message Encryption Mode
AuthenticationChallenge Msg
Alert WithInformation Msg
Data Burst Msg
Analog HandoffDirection Msg
In-Traffic SystemParameters Msg
Neighbor ListUpdate Msg
Send Burst DTMF Msg
Power ControlParameters Msg.
Retrieve Parameters Msg
Set Parameters Msg
SSD Update Msg
Flash WithInformation Msg
Mobile StationRegistered Msg
Status Request Msg
Extended HandoffDirection Msg
Service Request Msg
Service Response Msg
Service Connect Msg
Service OptionControl Msg
TMSI Assignment Msg
February, 2005 7 - 39RF100 v2.0 (c) 2005 Scott Baxter
Section E
CDMA Handset ArchitectureCDMA Handoffs
CDMA Handset ArchitectureCDMA Handoffs
February, 2005 7 - 40RF100 v2.0 (c) 2005 Scott Baxter
What’s In a Handset? How does it work?
ReceiverRF SectionIF, Detector
TransmitterRF Section
Vocoder
Digital Rake Receiver
Traffic CorrelatorPN xxx Walsh xx ΣTraffic CorrelatorPN xxx Walsh xxTraffic CorrelatorPN xxx Walsh xx
Pilot SearcherPN xxx Walsh 0
Viterbi Decoder,Convl. Decoder,Demultiplexer
CPUDuplexer
TransmitterDigital Section
Long Code Gen.
Open Loop Transmit Gain Adjust
Messages
Messages
Audio
Audio
Packets
Symbols
SymbolsChips
RF
RF
AGC
time-
alig
ned
su
mm
ing
pow
er
Traffic CorrelatorPN xxx Walsh xx
∆tcont
rol
bits
February, 2005 7 - 41RF100 v2.0 (c) 2005 Scott Baxter
The Rake Receiver
Every frame, handset uses combined outputs of the three traffic correlators (“rake fingers”)Each finger can independently recover a particular PN offset andWalsh codeFingers can be targeted on delayed multipath reflections, or even on different BTSsSearcher continuously checks pilots
Handset Rake Receiver
RF
PN Walsh
PN Walsh
PN Walsh
SearcherPN W=0
ΣVoice,Data,
Messages
Pilot Ec/Io
BTS
BTS
February, 2005 7 - 42RF100 v2.0 (c) 2005 Scott Baxter
CDMA Soft Handoff Mechanics
CDMA soft handoff is driven by the handset• Handset continuously checks available pilots• Handset tells system pilots it currently sees• System assigns sectors (up to 6 max.), tells handset• Handset assigns its fingers accordingly• All messages sent by dim-and-burst, no muting!
Each end of the link chooses what works best, on a frame-by-frame basis!
• Users are totally unaware of handoff
Handset Rake Receiver
RFPN Walsh
PN Walsh
PN Walsh
SearcherPN W=0
ΣVoice,Data,
Messages
Pilot Ec/Io
BTS
BSCSwitch
BTS
Sel.
February, 2005 7 - 43RF100 v2.0 (c) 2005 Scott Baxter
The Complete Rules of Soft Handoff
The Handset considers pilots in sets• Active: pilots of sectors actually in use• Candidates: pilots mobile requested, but
not yet set up & transmitting by system• Neighbors: pilots told to mobile by system,
as nearby sectors to check• Remaining: any pilots used by system but
not already in the other sets (div. by PILOT_INC)
Handset sends Pilot Strength Measurement Message to the system whenever:
• It notices a pilot in neighbor or remaining set exceeds T_ADD
• An active set pilot drops below T_DROP for T_TDROP time
• A candidate pilot exceeds an active by T_COMP
The System may set up all requested handoffs, or it may apply special manufacturer-specific screening criteria and only authorize some
65
Remaining
ActiveCandidateNeighbor 20
PILOT SETS
Min. M
embers
Req’d. B
y Std.
T_COMPT_ADD T_DROPT_TDROP
HANDOFF PARAMETERS
Exercise: How does a pilot in one set migrate into another set, for all cases? Identify the trigger, and the messages involved.
February, 2005 7 - 44RF100 v2.0 (c) 2005 Scott Baxter
Softer Handoff
Each BTS sector has unique PN offset & pilot Handset will ask for whatever pilots it wantsIf multiple sectors of one BTS simultaneously serve a handset, this is called Softer HandoffHandset can’t tell the difference, but softer handoff occurs in BTS in a single channel elementHandset can even use combination soft-softer handoff on multiple BTS & sectors
Handset Rake Receiver
RFPN Walsh
PN Walsh
PN Walsh
SearcherPN W=0
ΣVoice,Data,
Messages
Pilot Ec/Io
BTS
BSCSwitchSel.
February, 2005 7 - 45RF100 v2.0 (c) 2005 Scott Baxter
What is Ec/Io?
Ec/Io• “cleanness” of the pilot
– foretells the readability of the associated traffic channels
• guides soft handoff decisions• digitally derived: ratio of good
to bad energy seen by the search correlator at the desired PN offset
• Never appears higher than Pilot’s percentage of serving cell’s transmitted energy
• Can be degraded by strong RF from other cells, sectors
– Imperfect orthogonality, other PNs are ~-20 dB.
• Can be degraded by noise
Ec/Io dB
-25 -15 -10 0
Ec
Io
Energy of desired pilot alone
Total energy received
February, 2005 7 - 46RF100 v2.0 (c) 2005 Scott Baxter
CDMA Call ProcessingCDMA Call Processing
Section F
February, 2005 7 - 47RF100 v2.0 (c) 2005 Scott Baxter
Let’s Acquire the System!Let’s Acquire the System!
Example 1
February, 2005 7 - 48RF100 v2.0 (c) 2005 Scott Baxter
Find a Frequency with a CDMA RF Signal
Mobile scans forward link frequencies:(Cellular or PCS, depending on model)
History ListPreferred Roaming List
until a CDMA signal is found.NO CDMA?! Go to AMPS,
or to a power-saving standby mode
HISTORYLIST/MRU
Last-used:FreqFreqFreqFreqFreqetc.
FREQUENCY LISTS:PREFERREDROAMINGLIST/PRL
System1System2System3System4System5etc.
Forward Link Frequencies(Base Station Transmit)
A D B E F C unlic.data
unlic.voice A D B E F C
1850MHz. 1910MHz. 1990 MHz.1930MHz.
1900 MHz. PCS Spectrum
824 MHz. 835 845 870 880 894
869
849
846.5825
890
891.5
Paging, ESMR, etc.A B A B
800 MHz. Cellular Spectrum
Reverse Link Frequencies(Mobile Transmit)
February, 2005 7 - 49RF100 v2.0 (c) 2005 Scott Baxter
How Idle Mobiles Choose CDMA CarriersAt turnon, Idle mobiles use proprietary algorithms to find the initial CDMA carrier intended for them to useWithin that CDMA signal, two types of paging channel messages could cause the idle mobile to choose another frequency: CDMA Channel List Message and GSRM
Go to last frequency from MRU
Strongest PN, read
SyncIs SID
permitted?
No Signal
Preferred Only Bit 0
Denied SIDRead
Paging Channel
CDMA Ch List Message
Global Svc Redir Msg
HASH using IMSI
my ACCOLC? redirect
Is better SID
available?
PRLMRU Acq IdxYes
NoF1F2F3
to Analog
to another CDMA frequency or system
ConfigMessages:
remain
Steps from the CDMA standards
Steps from proprietary
SDAs
Proprietary SDA
databases
Start
LegendTypical MobileSystem Determination Algorithm
February, 2005 7 - 50RF100 v2.0 (c) 2005 Scott Baxter
4. Is This the Right System to Use?Scan the PRL for Anything Better
It’s not enough just to find a CDMA signal
• We want the CDMA signal of our own system or a favorite roaming partner
Phones look in the PRL to see if there is a more preferred signal than whatever they find first
• They check frequencies in the Acquisition Table until they find the best system, or look down the list level by level
ROAMING LIST
Roaming List Type: IS-683APreferred Only: FALSEDefault Roaming Indicator: 0Preferred List ID: 10018
ACQUISITION TABLE
INDEX ACQ TYPE CH1 CH2 CH3 CH4 CH5 CH6 CH7 CH8 CH90 6 500 425 825 575 850 325 6251 6 575 625 500 4252 6 50 100 75 475 825 850 175 2503 6 25 200 350 375 725 50 475 175 2504 1 Both5 6 450 500 350 575 6506 6 675 500 600 575 4757 6 250 50 1758 6 550 375 425 6259 6 75 50 175 250
10 6 200 250 175 5011 6 425 500 575 25 325 65012 6 500 575 475 25 67513 6 500 625 350 50 375 775 575 725 42514 6 650 500 675 25 75 425 50 57515 6 25 50 375 350 250 17516 6 425 550 225 725 750 77517 6 200 50 175 375 25018 6 825 850 92519 6 350 325 375 675 25 1175 725 600 10020 6 750 725 77521 6 325 725 350 750 375 775 425 575 62522 6 1150 117523 6 350 875 325 375 117524 6 25 1175 825 200 75 175 25025 6 50 200 25 100 250 7526 6 500 1075 850 82527 1 A28 1 B29 5 A30 5 B31 5 C32 5 D33 5 E34 5 F35 4 A36 4 B37 4 Both38 6 350 82539 6 25 10040 6 675 600 750 850 1175 77541 6 85042 6 65043 6 450 47544 6 325 350 375 1025 1050 107545 6 150 475 625 67546 6 1025 1050 1075
SYSTEM TABLE
INDEX SID NIDNEG/ PREF GEO PRI
ACQ INDEX
ROAM IND
296 4144 65535 Pref NEW SAME 13 1297 4812 65535 Pref SAME MORE 21 1298 205 65535 Pref SAME SAME 4 0299 208 65535 Pref SAME MORE 37 0300 208 65535 Pref SAME SAME 4 0301 342 65535 Pref SAME MORE 37 0302 342 65535 Pref SAME SAME 4 0303 478 65535 Pref SAME SAME 4 0304 1038 65535 Pref SAME SAME 4 0305 1050 65535 Pref SAME SAME 4 0306 1058 65535 Pref SAME SAME 4 0307 1375 65535 Pref SAME SAME 4 0308 1385 65535 Pref SAME MORE 4 0309 143 65535 Pref SAME MORE 37 0310 143 65535 Pref SAME MORE 4 0311 4103 65535 Pref NEW SAME 3 1312 4157 65535 Pref SAME MORE 2 1313 312 65535 Pref SAME SAME 4 0314 444 65535 Pref SAME MORE 37 0315 444 65535 Pref SAME SAME 4 0316 1008 65535 Pref SAME SAME 4 0317 1012 65535 Pref SAME SAME 4 0318 1014 65535 Pref SAME SAME 4 0319 1688 65535 Pref SAME MORE 4 0320 113 65535 Pref SAME MORE 37 0321 113 65535 Pref SAME SAME 4 0322 179 65535 Pref SAME MORE 37 0323 179 65535 Pref SAME SAME 4 0324 465 65535 Pref SAME SAME 4 0325 2119 65535 Pref SAME MORE 4 0326 2094 65535 Pref SAME MORE 4 0327 1005 65535 Pref SAME SAME 4 0328 1013 65535 Pref SAME SAME 4 0
a G
EO G
RO
UP
a G
EO G
RO
UP
Clim
b!
PRL: Preferred Roaming ListProgrammed into each phone by the system
operator; can be updated over the air.
February, 2005 7 - 51RF100 v2.0 (c) 2005 Scott Baxter
Find Strongest Pilot, Read Sync Channel
Rake Fingers
Reference PN
Active Pilot
Ec/
Io
00
32K512
ChipsPN
1. Pilot Searcher Scans the Entire Range of PNs
All PN Offsets0
-20
98/05/24 23:14:09.817 [SCH] MSG_LENGTH = 208 bitsMSG_TYPE = Sync Channel MessageP_REV = 3MIN_P_REV = 2SID = 179NID = 0PILOT_PN = 168Offset IndexLC_STATE = 0x0348D60E013SYS_TIME = 98/05/24 23:14:10.160LP_SEC = 12LTM_OFF = -300 minutesDAYLT = 0PRAT = 9600 bpsRESERVED = 1
2. Put Rake finger(s) on strongest available PN, decode Walsh 32, and read Sync Channel Message
SYNC CHANNEL MESSAGE
Handset Rake Receiver
RF≈ x ≈
LO Srch PN??? W0
F1 PN168 W32F2 PN168 W32F3 PN168 W32
February, 2005 7 - 52RF100 v2.0 (c) 2005 Scott Baxter
The Configuration Messages
After reading the Sync Channel, the mobile is now capable of reading the Paging Channel, which it now monitors constantlyBefore it is allowed to transmit or operate on this system, the mobile must collect a complete set of configuration messages Collection is a short process -- all configuration messages are repeated on the paging channel every 1.28 secondsThe configuration messages contain sequence numbers so the mobile can recognize if any of the messages have been freshly updated as it continues to monitor the paging channel
• Access parameters message sequence number• Configuration message sequence number• If a mobile notices a changed sequence number, or if 600
seconds passes since the last time these messages were read, the mobile reads all of them again
February, 2005 7 - 53RF100 v2.0 (c) 2005 Scott Baxter
Go to Paging Channel, Get Configured
Rake Fingers
Reference PN
Active Pilot
Ec/
Io
00
32K512
ChipsPN
All PN Offsets0
-20
Keep Rake finger(s) on strongest available PN, decode Walsh 1,
and monitor the Paging Channel
Read the Configuration Messages
Access Parameters Msg
System Parameters Msg
CDMA Channel List Msg
Extended SystemParameters Msg (*opt.)
(Extended*) NeighborList Msg
Global ServiceRedirection Msg (*opt.)
Now we’re ready to operate!!
Handset Rake Receiver
RF≈ x ≈
LO Srch PN??? W0
F1 PN168 W01F2 PN168 W01F3 PN168 W01
February, 2005 7 - 54RF100 v2.0 (c) 2005 Scott Baxter
Two Very Important Configuration Messages
98/05/24 23:14:10.427 [PCH] MSG_LENGTH = 184 bitsMSG_TYPE = Access Parameters MessagePILOT_PN = 168 Offset IndexACC_MSG_SEQ = 27ACC_CHAN = 1 channelNOM_PWR = 0 dB INIT_PWR = 0 dB PWR_STEP = 4 dBNUM_STEP = 5 Access Probes MaximumMAX_CAP_SZ = 4 Access Channel Frames MaximumPAM_SZ = 3 Access Channel FramesPersist Val for Acc Overload Classes 0-9 = 0Persist Val for Acc Overload Class 10 = 0Persist Val for Acc Overload Class 11 = 0Persist Val for Acc Overload Class 12 = 0Persist Val for Acc Overload Class 13 = 0Persist Val for Acc Overload Class 14 = 0Persist Val for Acc Overload Class 15 = 0Persistance Modifier for Msg Tx = 1 Persistance Modifier for Reg = 1 Probe Randomization = 15 PN chipsAcknowledgement Timeout = 320 msProbe Backoff Range = 4 Slots MaximumProbe Sequence Backoff Range = 4 Slots Max.Max # Probe Seq for Requests = 2 SequencesMax # Probe Seq for Responses = 2 SequencesAuthentication Mode = 1Random Challenge Value = Field OmittedReserved Bits = 99
ACCESS PARAMETERS MESSAGE98/05/24 23:14:11.126 [PCH] MSG_LENGTH = 264 bitsMSG_TYPE = System Parameters MessagePILOT_PN = 168 Offset IndexCONFIG_MSG_SEQ = 0SID = 179 NID = 0REG_ZONE = 0 TOTAL_ZONES = 0 ZONE_TIMER = 60 minMULT_SIDS = 0 MULT_NID = 0 BASE_ID = 8710BASE_CLASS = Public MacrocellularPAGE_CHAN = 1 channelMAX_SLOT_CYCLE_INDEX = 0HOME_REG = 0 FOR_SID_REG = 0 FOR_NID_REG = 1POWER_UP_REG = 0 POWER_DOWN_REG = 0PARAMETER_REG = 1 REG_PRD = 0.08 secBASE_LAT = 00D00'00.00N BASE_LONG = 000D00'00.00EREG_DIST = 0SRCH_WIN_A = 40 PN chipsSRCH_WIN_N = 80 PN chipsSRCH_WIN_R = 4 PN chipsNGHBR_MAX_AGE = 0PWR_REP_THRESH = 2 framesPWR_REP_FRAMES = 56 framesPWR_THRESH_ENABLE = 1PWR_PERIOD_ENABLE = 0PWR_REP_DELAY = 20 framesRESCAN = 0T_ADD = -13.0 Db T_DROP = -15.0 dB T_COMP = 2.5 dBT_TDROP = 4 secEXT_SYS_PARAMETER = 1RESERVED = 0GLOBAL_REDIRECT = 0
SYSTEM PARAMETERS MESSAGE
February, 2005 7 - 55RF100 v2.0 (c) 2005 Scott Baxter
Four Additional Configuration Messages
98/05/24 23:14:10.946 [PCH] MSG_LENGTH = 104 bitsMSG_TYPE = Extended System Parameters MessagePILOT_PN = 168 Offset IndexCONFIG_MSG_SEQ = 0 RESERVED = 0PREF_MSID_TYPE = IMSI and ESNMCC = 000 IMSI_11_12 = 00 RESERVED_LEN = 8 bitsRESERVED_OCTETS = 0x00 BCAST_INDEX = 0RESERVED = 0
EXTENDED SYSTEM PARAMETERS
98/05/17 24:21.566 Paging Channel: Global Service RedirectionPILOT_PN: 168, MSG_TYPE: 96, CONFIG_MSG_SEQ: 0Redirected access overload classes: 0, 1 , RETURN_IF_FAIL: 0, DELETE_TMSI: 0, Redirection to an analog system: EXPECTED_SID = 0 Do not ignore CDMA Available indicator on the redirected analog systemAttempt service on either System A or B with the custom system selection process
GLOBAL SERVICE REDIRECTION
98/05/24 23:14:11.486 [PCH]MSG_LENGTH = 216 bitsMSG_TYPE = Neighbor List MessagePILOT_PN = 168 Offset IndexCONFIG_MSG_SEQ = 0PILOT_INC = 4 Offset IndexNGHBR_CONFIG = 0 NGHBR_PN = 220 Offset IndexNGHBR_CONFIG = 0 NGHBR_PN = 52 Offset IndexNGHBR_CONFIG = 0 NGHBR_PN = 500 Offset IndexNGHBR_CONFIG = 0 NGHBR_PN = 8 Offset IndexNGHBR_CONFIG = 0 NGHBR_PN = 176 Offset IndexNGHBR_CONFIG = 0 NGHBR_PN = 304 Offset IndexNGHBR_CONFIG = 0 NGHBR_PN = 136 Offset IndexNGHBR_CONFIG = 0 NGHBR_PN = 384 Offset IndexNGHBR_CONFIG = 0 NGHBR_PN = 216 Offset IndexNGHBR_CONFIG = 0 NGHBR_PN = 68 Offset IndexNGHBR_CONFIG = 0 NGHBR_PN = 328 Offset IndexNGHBR_CONFIG = 0 NGHBR_PN = 112 Offset IndexRESERVED = 0
NEIGHBOR LIST
98/05/24 23:14:10.786 [PCH]MSG_LENGTH = 72 bitsMSG_TYPE = CDMA Channel List MessagePILOT_PN = 168 Offset IndexCONFIG_MSG_SEQ = 0CDMA_FREQ = 283RESERVED = Field Omitted
CDMA CHANNEL LIST MESSAGE
February, 2005 7 - 56RF100 v2.0 (c) 2005 Scott Baxter
Let’s do an Idle Mode Handoff!
Let’s do an Idle Mode Handoff!
Example 2
February, 2005 7 - 57RF100 v2.0 (c) 2005 Scott Baxter
Idle Mode Handoff
An idle mobile always demodulates the best available signal• In idle mode, it isn’t possible to do soft handoff and listen to
multiple sectors or base stations at the same time -- the paging channel information stream is different on each sector, not synchronous -- just like ABC, NBC, CBS, and CNN TV news programs aren’t in word-sync for simultaneous viewing
• Since a mobile can’t combine signals, the mobile must switch quickly, always enjoying the best available signal
The mobile’s pilot searcher is constantly checking neighbor pilotsIf the searcher notices a better signal, the mobile continues on the current paging channel until the end of the current superframe, then instantly switches to the paging channel of the new signal
• The system doesn’t know the mobile did this! (Does NBC’s Tom Brokaw know you just switched your TV to CNN?)
On the new paging channel, if the mobile learns that registration is required, it re-registers on the new sector
February, 2005 7 - 58RF100 v2.0 (c) 2005 Scott Baxter
Idle Mode on the Paging Channel: Meet the Neighbors, track the Strongest Pilot
Ec/
IoAll PN Offsets
00
32K512
ChipsPN
0
-20
Neighbor Set
The phone’s pilot searcher constantly checks the pilots listed in the Neighbor List Message
If the searcher ever notices a neighbor pilot substantially stronger than the current reference pilot, it becomes the new reference pilot
and the phone switches over to its paging channel on the next superframe.This is called an idle mode handoff.
Rake Fingers
Reference PN
Active Pilot
SRCH_WIN_A
SRCH_WIN_N
Mobile Rake RX
Srch PN??? W0
F1 PN168 W01F2 PN168 W01F3 PN168 W01
February, 2005 7 - 59RF100 v2.0 (c) 2005 Scott Baxter
Phone Operation on the Access Channel
A sector’s Paging Channel announces 1 (typ) to 32 (max) Access Channels: PN Long Code offsets for mobiles to use if accessing the system.
• For mobiles sending Registration, Origination, Page Responses
• Base Station always listening!On the access channel, phones are not yet under BTS closed-loop power control!Phones access the BTS by “probing” at power levels determined by receive power and an open loop formula
• If “probe” not acknowledged by BTS within ACC_TMO (~400 mS.), phone will wait a random time (~200 mS) then probe again, stronger by PI db.
• There can be 15 max. (typ. 5) probes in a sequence and 15 max. (typ. 2) sequences in an access attempt
• most attempts succeed on first probe!The Access Parameters message on the paging channel announces values of all related parameters
ACCESS
RV TFC
BTS
Channel Assnmt. Msg.
Origination Msg
Base Sta. Acknlgmt. Order
TFC frames of 000s
TFC preamble of 000s
Base Sta. Acknlgmt. Order
Mobile Sta. Ackngmt. Order
Service Connect Msg.
Svc. Connect Complete Msg
Base Sta. Acknlgmt. Order
Call is Established!
MSProbing
PAGING
FW TFC
PAGING
RV TFC
FW FC
RV TFC
FW TFC
FW TFC
A Successful Access Attempt
a Probe Sequencean Access Attempt
Success!
an Access Probe
February, 2005 7 - 60RF100 v2.0 (c) 2005 Scott Baxter
Let’s Register!Let’s Register!
Example 3
February, 2005 7 - 61RF100 v2.0 (c) 2005 Scott Baxter
Registration
Registration is the process by which an idle mobile lets the system know it’s awake and available for incoming calls
• this allows the system to inform the mobile’s home switch of the mobile’s current location, so that incoming calls can be delivered
• registration also allows the system to intelligently page the mobile only in the area where the mobile is currently located, thereby eliminating useless congestion on the paging channels in other areas of the system
There are many different conditions that could trigger an obligation for the mobile to register
• there are flags in the System Parameters Message which tell the mobile when it must register on the current system
February, 2005 7 - 62RF100 v2.0 (c) 2005 Scott Baxter
An Actual Registration
16:18:27.144 Access Channel: Registration ACK_SEQ: 7 MSG_SEQ: 1 ACK_REQ: 1 VALID_ACK: 0ACK_TYPE: 0MSID_TYPE: 3, ESN: [0x 01 99 0d fc]MFR 1, Reserved 38, Serial Number 69116,IMSI: (Class: 0, Class_0_type: 1) [0x 01 8d 31 74 29 36]00-416-575-0421AUTH_MODE: 0REG_TYPE: Timer-basedSLOT_CYCLE_INDEX: 2MOB_P_REV: 1EXT_SCM: 1SLOTTED_MODE: 1MOB_TERM: 1
REGISTRATION MESSAGE
18:26.826 [PCH] System Parameters Message Pilot_PN: 32CONFIG_MSG_SEQ: 14 SID: 16420 NID: 0,REG_ZONE: 0 TOTAL_ZONES: 0 Zone timer length (min): 1MULT_SIDS: 0 MULT_NIDS: 0 BASE_ID: 1618 BASE_CLASS: ReservedPAG_CHAN: 1 MAX_SLOT_CYCLE_INDEX: 2 HOME_REG: 1 FOR_SID_REG: 1 FOR_NID_REG: 1, POWER_UP_REG: 1 POWER_DOWN_REG: 1 PARAMETER_REG: 1 Registration period (sec): 54 Base station 0°00´00.00¨ Lon., 0°00´00.00° Lat. REG_DIST: 0SRCH_WIN_A (PN chips): 28 SRCH_WIN_N (PN chips): 100, SRCH_WIN_R (PN chips): 130 NGHBR_MAX_AGE: 2PWR_REP_THRESH: 2 PWR_REP_FRAMES (frames): 15PWR_THRESH_ENABLE: 1 PWR_PERIOD_ENABLE: 0, PWR_REP_DELAY: 1 (4 frames) RESCAN: 0, T_ADD: -14.0dB T_DROP: -16.0dB T_COMP: 2.5dB, T_TDROP: 4s EXT_SYS_PARAMETER: 1 EXT_NGHBR_LIST: 1 GLOBAL_REDIRECT: 0
SYSTEM PARAMETERS MESSAGE
16:18:27.506 Paging Channel: Order ACK_SEQ: 1 MSG_SEQ: 0 ACK_REQ: 0 VALID_ACK: 1 MSID_TYPE: 2 IMSI: (Class: 0, Class_0_type: 3) [0x 02 47 8d 31 74 29 36] (302) 00-416-575-0421Order type: Base Station Acknowledgement Order
BASE STATION ACKNOWLEDGMENT
The System Parameters Message tells all mobiles when they should register.
This mobile notices that it is obligated to register, so it transmits a Registration
Message.
The base station confirms that the mobile’s registration message was received. We’re officially registered!
February, 2005 7 - 63RF100 v2.0 (c) 2005 Scott Baxter
Let’s Receive an incoming Call!
Let’s Receive an incoming Call!
Example 4
February, 2005 7 - 64RF100 v2.0 (c) 2005 Scott Baxter
Receiving an Incoming Call
All idle mobiles monitor the paging channel to receive incoming calls.When an incoming call appears, the paging channel notifies the mobile in a General Page Message.A mobile which has been paged sends a Page Response Message on the access channel.The system sets up a traffic channel for the call, then notifies the mobile to use it with a Channel Assignment Message.The mobile and the base station notice each other’s traffic channel signals and confirm their presence by exchanging acknowledgment messages.The base station and the mobile negotiate what type of call this will be -- I.e., 13k voice, etc.The mobile is told to ring and given a “calling line ID” to display.When the human user presses the send button, the audio path is completed and the call proceeds.
February, 2005 7 - 65RF100 v2.0 (c) 2005 Scott Baxter
An Actual Page and Page Response
98/05/24 23:14:46.425 [ACH] Page Response MessageMSG_LENGTH = 216 bitsMSG_TYPE = Page Response MessageACK_SEQ = 1 MSG_SEQ = 2 ACK_REQ = 1VALID_ACK = 1 ACK_TYPE = 2MSID_TYPE = IMSI and ESN MSID_LEN = 9 octetsESN = 0xD30E415C IMSI_CLASS = 0IMSI_CLASS_0_TYPE = 0 RESERVED = 0IMSI_S = 6153300644AUTH_MODE = 1AUTHR = 0x307B5 RANDC = 0xC6 COUNT = 0MOB_TERM = 1 SLOT_CYCLE_INDEX = 0MOB_P_REV = 3 SCM = 106REQUEST_MODE = Either Wide Analog or CDMA OnlySERVICE_OPTION = 32768 PM = 0NAR_AN_CAP = 0 RESERVED = 0
PAGE RESPONSE MESSAGE
98/05/24 23:14:46.127 [PCH] General Page MessageMSG_LENGTH = 128 bits MSG_TYPE = General Page MessageCONFIG_MSG_SEQ = 1 ACC_MSG_SEQ = 20CLASS_0_DONE = 1CLASS_1_DONE = 1 RESERVED = 0BROADCAST_DONE = 1 RESERVED = 0ADD_LENGTH = 0 bits ADD_PFIELD = Field OmittedPAGE_CLASS = 0 PAGE_SUBCLASS = 0MSG_SEQ = 1 IMSI_S = 6153300644SPECIAL_SERVICE = 1SERVICE_OPTION = 32768RESERVED = Field Omitted
GENERAL PAGE MESSAGE
98/05/24 23:14:46.768 [PCH] Order MessageMSG_LENGTH = 112 bitsMSG_TYPE = Order MessageACK_SEQ = 2 MSG_SEQ = 0 ACK_REQ = 0VALID_ACK = 1 ADDR_TYPE = IMSI ADDR_LEN = 40 bitsIMSI_CLASS = 0 IMSI_CLASS_0_TYPE = 0 RESERVED = 0 IMSI_S = 6153300644ORDER = Base Station Acknowledgement OrderADD_RECORD_LEN = 0 bitsOrder-Specific Fields = Field Omitted RESERVED = 0
BASE STATION ACKNOWLEDGMENT
The system pages the mobile, 615-330-0644.
The base station confirms that the mobile’s page response was received. Now the
mobile is waiting for channel assignment,expecting a response within 12 seconds.
The mobile responds to the page.
February, 2005 7 - 66RF100 v2.0 (c) 2005 Scott Baxter
Channel Assignment and Traffic Channel Confirmation
18:14:47.598 Reverse Traffic Channel: Order ACK_SEQ: 0 MSG_SEQ: 0 ACK_REQ: 0 ENCRYPTION: 0Mobile Station Acknowledgement Order
MOBILE STATION ACKNOWLEDGMENT
18:14:47.027 Paging Channel: Channel Assignment ACK_SEQ: 2 MSG_SEQ: 1 ACK_REQ: 0 VALID_ACK: 1MSID_TYPE: 2 IMSI: (Class: 0, Class_0_type: 0) [0x 01 f8 39 6a 15] 615-330-0644 ASSIGN_MODE: Traffic Channel AssignmentADD_RECORD_LEN: 5 FREQ_INCL: 1 GRANTED_MODE: 2CODE_CHAN: 43 FRAME_OFFSET: 2ENCRYPT_MODE: Encryption disabledBAND_CLASS: 800 MHz cellular bandCDMA_FREQ: 283
CHANNEL ASSIGNMENT MESSAGE
18:14:47.581 Forward Traffic Channel: Order ACK_SEQ: 7 MSG_SEQ: 0 ACK_REQ: 1 ENCRYPTION: 0 USE_TIME: 0 ACTION_TIME: 0Base Station Acknowledgement Order
BASE STATION ACKNOWLEDGMENT
Only about 400 ms. after the base station acknowledgment order, the mobile receives
the channel assignment message.
The base station is already sending blank frames on
the forward channel,using the assigned Walsh code.
The mobile sees at least two good blank frames in a row on
the forward channel, and concludes this is the right traffic channel. It sends a preamble of two blank frames of its own on the reverse traffic channel.
The base station acknowledges receiving the mobile’s preamble.
The mobile station acknowledges the base station’s acknowledgment.
Everybody is ready!
February, 2005 7 - 67RF100 v2.0 (c) 2005 Scott Baxter
Service Negotiation and Mobile Alert
18:14:47.835 Reverse Traffic Channel: Service Connect Completion ACK_SEQ: 1 MSG_SEQ: 3 ACK_REQ: 1 ENCRYPTION: 0 SERV_CON_SEQ: 0
SERVICE CONNECT COMPLETE MSG.
18:14:47.760 Forward Traffic Channel: Service Connect ACK_SEQ: 0 MSG_SEQ: 1 ACK_REQ: 0 ENCRYPTION: 0USE_TIME: 0 ACTION_TIME: 0 SERV_CON_SEQ: 0Service Configuration: supported Transmission: Forward Traffic Channel Rate (Set 2): 14400, 7200, 3600, 1800 bps Reverse Traffic Channel Rate (Set 2): 14400, 7200, 3600, 1800 bps Service option: (6) Voice (13k) (0x8000) Forward Traffic Channel: Primary Traffic Reverse Traffic Channel: Primary Traffic
SERVICE CONNECT MESSAGENow that both sides have arrived on the
traffic channel, the base station proposes that the requested call
actually begin.
The mobile agrees and says its ready to play.
18:14:47.961 Forward Traffic Channel: Alert With Information ACK_SEQ: 3 MSG_SEQ: 1 ACK_REQ: 1 ENCRYPTION: 0SIGNAL_TYPE = IS-54B Alerting ALERT_PITCH = Medium Pitch (Standard Alert)SIGNAL = Long RESERVED = 0RECORD_TYPE = Calling Party NumberRECORD_LEN = 96 bitsNUMBER_TYPE = National NumberNUMBER_PLAN = ISDN/Telephony Numbering PlanPI = Presentation Allowed SI = Network ProvidedCHARi = 6153000124 RESERVED = 0 RESERVED = 0
ALERT WITH INFORMATION MESSAGE
The base station orders the mobile to ring, and gives it the calling party’s number to display.
18:14:48.018 Reverse Traffic Channel: Order ACK_SEQ: 1 MSG_SEQ: 4 ACK_REQ: 0ENCRYPTION: 0 Mobile Station Acknowledgement Order
The mobile says it’s ringing.
SERVICE CONNECT COMPLETE is a major milestone in call processing. Up until now, this was an access attempt.
Now it is officially a call.
February, 2005 7 - 68RF100 v2.0 (c) 2005 Scott Baxter
The Human Answers! Connect Order
The mobile has been ringing for several seconds. The human user finally comes over and presses the send
button to answer the call.
Now the switch completes the audio circuit and the two callers can talk!
18:14:54.920 Forward Traffic Channel: Order ACK_SEQ: 0 MSG_SEQ: 1 ACK_REQ: 0 ENCRYPTION: 0 USE_TIME: 0 ACTION_TIME: 0 Base Station Acknowledgement Order
BASE STATION ACKNOWLEDGMENT
18:14:54.758 Reverse Traffic Channel: Order ACK_SEQ: 6 MSG_SEQ: 0 ACK_REQ: 1 ENCRYPTION: 0 Connect Order
CONNECT ORDER
February, 2005 7 - 69RF100 v2.0 (c) 2005 Scott Baxter
Let’s make an Outgoing Call!Let’s make an Outgoing Call!
Example 5
February, 2005 7 - 70RF100 v2.0 (c) 2005 Scott Baxter
Placing an Outgoing Call
The mobile user dials the desired digits, and presses SEND.Mobile transmits an Origination Message on the access channel.The system acknowledges receiving the origination by sending a base station acknowledgement on the paging channel.The system arranges the resources for the call and starts transmitting on the traffic channel.The system notifies the mobile in a Channel Assignment Message on the paging channel.The mobile arrives on the traffic channel.The mobile and the base station notice each other’s traffic channel signals and confirm their presence by exchanging acknowledgment messages.The base station and the mobile negotiate what type of call this will be -- I.e., 13k voice, etc.The audio circuit is completed and the mobile caller hears ringing.
February, 2005 7 - 71RF100 v2.0 (c) 2005 Scott Baxter
Origination17:48:53.144 Access Channel: Origination ACK_SEQ: 7 MSG_SEQ: 6 ACK_REQ: 1 VALID_ACK: 0 ACK_TYPE: 0 MSID_TYPE: 3 ESN: [0x 00 06 98 24] MFR 0 Reserved 1 Serial Number 170020 IMSI: (Class: 0, Class_0_type: 0) [0x 03 5d b8 97 c2] 972-849-5073AUTH_MODE: 0 MOB_TERM: 1SLOT_CYCLE_INDEX: 2 MOB_P_REV: 1 EXT_SCM: 1DualMode: 0 SLOTTED_MODE: 1 PowerClass: 0REQUEST_MODE: CDMA only SPECIAL_SERVICE: 1 Service option: (6) Voice (13k) (0x8000) PM: 0 DIGIT_MODE: 0 MORE_FIELDS: 0 NUM_FIELDS: 11Chari: 18008900829 NAR_AN_CAP: 0
ORIGINATION MESSAGE
17:48:53.487 Paging Channel: Order ACK_SEQ: 6 MSG_SEQ: 0 ACK_REQ: 0 VALID_ACK: 1 MSID_TYPE: 2IMSI: (Class: 0, Class_0_type: 0) [0x 03 5d b8 97 c2] 972-849-5073 Base Station Acknowledgment Order
BASE STATION ACKNOWLEDGMENT
The mobile sends an origination message
on the access channel.
The base station confirms that the origination message
was received.17:48:54.367 Paging Channel: Channel Assignment ACK_SEQ: 6 MSG_SEQ: 1 ACK_REQ: 0 VALID_ACK: 1MSID_TYPE: 2 IMSI: (Class: 0, Class_0_type: 0) [0x 03 5d b8 97 c2] 972-849-5073 ASSIGN_MODE: Traffic Channel Assignment, ADD_RECORD_LEN: 5 FREQ_INCL: 1 GRANTED_MODE: 2CODE_CHAN: 12 FRAME_OFFSET: 0 ENCRYPT_MODE: Encryption disabled BAND_CLASS: 1.8 to 2.0 GHz PCS band CDMA_FREQ: 425
CHANNEL ASSIGNMENT MESSAGE
The base station sends a Channel Assignment
Message and the mobile goes to the traffic channel.
February, 2005 7 - 72RF100 v2.0 (c) 2005 Scott Baxter
Traffic Channel Confirmation
17:48:54.835 Reverse Traffic Channel: Order ACK_SEQ: 0 MSG_SEQ: 0 ACK_REQ: 0 ENCRYPTION: 0 Mobile Station Acknowledgment Order
MOBILE STATION ACKNOWLEDGMENT17:48:54.757 Forward Traffic Channel: Order ACK_SEQ: 7 MSG_SEQ: 0 ACK_REQ: 1 ENCRYPTION: 0USE_TIME: 0 ACTION_TIME: 0 Base Station Acknowledgment Order
BASE STATION ACKNOWLEDGMENT
The base station is already sending blank frames on
the forward channel,using the assigned Walsh code.
The mobile sees at least two good blank frames in a row on
the forward channel, and concludes this is the right traffic channel. It sends a preamble of two blank frames of its own on the reverse traffic channel.
The base station acknowledges receiving the mobile’s preamble.
The mobile station acknowledges the base station’s acknowledgment.
Everybody is ready!
February, 2005 7 - 73RF100 v2.0 (c) 2005 Scott Baxter
Service Negotiation and Connect Complete
17:48:55.137 Reverse Traffic Channel: Service Connect Completion ACK_SEQ: 1, MSG_SEQ: 0, ACK_REQ: 1, ENCRYPTION: 0, SERV_CON_SEQ: 0
SERVICE CONNECT COMPLETE MSG.
17:48:55.098 Forward Traffic Channel: Service Connect ACK_SEQ: 7 MSG_SEQ: 1 ACK_REQ: 1 ENCRYPTION: 0USE_TIME: 0 ACTION_TIME: 0 SERV_CON_SEQ: 0 Service Configuration Supported Transmission: Forward Traffic Channel Rate (Set 2): 14400, 7200, 3600, 1800 bpsReverse Traffic Channel Rate (Set 2): 14400, 7200, 3600, 1800 bpsService option: (6) Voice (13k) (0x8000) Forward Traffic Channel: Primary TrafficReverse Traffic Channel: Primary Traffic
SERVICE CONNECT MESSAGENow that the traffic channel is working
in both directions, the base station proposes that the requested call
actually begin.
The mobile agrees and says its ready to play.
17:48:55.779 Forward Traffic Channel: Order ACK_SEQ: 0 MSG_SEQ: 0 ACK_REQ: 0 ENCRYPTION: 0USE_TIME: 0 ACTION_TIME: 0 Base Station Acknowledgment Order
BASE STATION ACKNOWLEDGMENT
The base station agrees. SERVICE CONNECT COMPLETE is a major milestone in call processing. Up until now, this was an access attempt.
Now it is officially a call.
Now the switch completes the audio circuit and the two callers can talk!
February, 2005 7 - 74RF100 v2.0 (c) 2005 Scott Baxter
Let’s End a Call!Let’s End a Call!
Example 6
February, 2005 7 - 75RF100 v2.0 (c) 2005 Scott Baxter
Ending A Call
A normal call continues until one of the parties hangs up. Thataction sends a Release Order, “normal release”. The other side of the call sends a Release Order, “no reason given”.
• If a normal release is visible, the call ended normally.At the conclusion of the call, the mobile reacquires the system.
• Searches for the best pilot on the present CDMA frequency• Reads the Sync Channel Message• Monitors the Paging Channel steadily
Several different conditions can cause a call to end abnormally:• the forward link is lost at the mobile, and a fade timer acts• the reverse link is lost at the base station, and a fade timer acts• a number of forward link messages aren’t acknowledged, and the
base station acts to tear down the link• a number of reverse link messages aren’t acknowledged, and the
mobile station acts to tear down the link
February, 2005 7 - 76RF100 v2.0 (c) 2005 Scott Baxter
A Beautiful End to a Normal Call
17:49:21.715 Reverse Traffic Channel: Order ACK_SEQ: 1 MSG_SEQ: 1 ACK_REQ: 1 ENCRYPTION: 0 Release Order (normal release)
MOBILE RELEASE ORDER
BASE STATION ACKNOWLEDGMENT17:49:21.936 Forward Traffic Channel: Order ACK_SEQ: 1 MSG_SEQ: 2 ACK_REQ: 0 ENCRYPTION: 0, USE_TIME: 0 ACTION_TIME: 0 Base Station Acknowledgement Order
At the end of a normal call, this mobile user pressed end.
The mobile left the traffic channel, scanned to find the best pilot, and read
the Sync Channel Message.
BASE STATION RELEASE ORDER17:49:21.997 Forward Traffic Channel: Order ACK_SEQ: 1 MSG_SEQ: 3 ACK_REQ: 0 ENCRYPTION: 0USE_TIME: 0 ACTION_TIME: 0 Release Order (no reason given)
17:49:22.517 Sync Channel MSG_TYPE: 1 Sync Channel MessageP_REV: 1 MIN_P_REV: 1SID: 4112 NID: 2 Pilot_PN: 183 LC_STATE: 0x318fe5d84a5 SYS_TIME: 0x1ae9683dcLP_SEC: 9 LTM_OFF: -10 DAYLT: 1 Paging Channel Data Rate: 9600 CDMA_FREQ: 425
SYNC CHANNEL MESSAGE
The base station acknowledged receiving the message, then sent
a release message of its own.
February, 2005 7 - 77RF100 v2.0 (c) 2005 Scott Baxter
Let’s receive Notificationof a Voice Message!
Let’s receive Notificationof a Voice Message!
Example 7
February, 2005 7 - 78RF100 v2.0 (c) 2005 Scott Baxter
Feature Notification
98/06/30 21:16:44.368 [PCH] Feature Notification MessageMSG_LENGTH = 144 bitsMSG_TYPE = Feature Notification MessageACK_SEQ = 0MSG_SEQ = 0ACK_REQ = 1VALID_ACK = 0ADDR_TYPE = IMSIADDR_LEN = 56 bitsIMSI_CLASS = 0IMSI_CLASS_0_TYPE = 3RESERVED = 0MCC = 302IMSI_11_12 = 00IMSI_S = 9055170325RELEASE = 0RECORD_TYPE = Message WaitingRECORD_LEN = 8 bitsMSG_COUNT = 1RESERVED = 0
FEATURE NOTIFICATION MESSAGE
The Feature Notification Message on the Paging Channel tells a specific mobile it has voice messages waiting.
There are other record types to notify the mobile of other features.
The mobile confirms it has received the notification by sending a Mobile Station Acknowledgment Order on the access
channel.
MOBILE STATION ACKNOWLEDGMENT
February, 2005 7 - 79RF100 v2.0 (c) 2005 Scott Baxter
Let’s do a Handoff!Let’s do a Handoff!
Example 8
February, 2005 7 - 80RF100 v2.0 (c) 2005 Scott Baxter
The Call is Already Established. What Next?E
c/Io
All PN Offsets
0
032K
512Chips
PN
0
-20
Neighbor Set
The call is already in progress. PN 168 is the only active signal,and also is our timing reference.
Continue checking the neighbors.
If we ever notice a neighbor with Ec/Io above T_ADD,ask to use it! Send a Pilot Strength Measurement Message!
T_ADD
Rake Fingers
Reference PN
Active Pilot
10752
16832002
50014080
220
! !
Mobile Rake RX
Srch PN??? W0
F1 PN168 W61F2 PN168 W61F3 PN168 W61
February, 2005 7 - 81RF100 v2.0 (c) 2005 Scott Baxter
Mobile Requests the Handoff!
98/05/24 23:14:02.205 [RTC] Pilot Strength Measurement MessageMSG_LENGTH = 128 bitsMSG_TYPE = Pilot Strength Measurement MessageACK_SEQ = 5 MSG_SEQ = 0 ACK_REQ = 1ENCRYPTION = Encryption Mode DisabledREF_PN = 168 Offset Index (the Reference PN)PILOT_STRENGTH = -6.0 dBKEEP = 1PILOT_PN_PHASE = 14080 chips (PN220+0chips)PILOT_STRENGTH = -12.5 dBKEEP = 1PILOT_PN_PHASE = 32002 chips (PN500 + 2 chips)PILOT_STRENGTH = -11.0 dBKEEP = 1RESERVED = 0
PILOT STRENGTH MEASUREMENT MESSAGE
98/05/24 23:14:02.386 [FTC] Order MessageMSG_LENGTH = 64 bitsMSG_TYPE = Order MessageACK_SEQ = 0 MSG_SEQ = 0 ACK_REQ = 0ENCRYPTION = Encryption Mode DisabledUSE_TIME = 0 ACTION_TIME = 0ORDER = Base Station Acknowledgment OrderADD_RECORD_LEN = 0 bitsOrder-Specific Fields = Field Omitted RESERVED = 0
BASE STATION ACKNOWLEDGMENT
Just prior to this message, this particular mobile already was in handoff with PN 168 and 220. This pilot strength measurement message reports PN 500 has increased above T_Add, and the mobile wants to use it too.
The base station acknowledges receiving the Pilot Strength Measurement Message.
February, 2005 7 - 82RF100 v2.0 (c) 2005 Scott Baxter
System Authorizes the Handoff!
98/05/24 23:14:02.926 [FTC] Extended Handoff Direction MessageMSG_LENGTH = 136 bitsMSG_TYPE = Extended Handoff Direction MessageACK_SEQ = 0 MSG_SEQ = 6 ACK_REQ = 1ENCRYPTION = Encryption Mode DisabledUSE_TIME = 0 ACTION_TIME = 0 HDM_SEQ = 0SEARCH_INCLUDED = 1 SRCH_WIN_A = 40 PN chipsT_ADD = -13.0 dB T_DROP = -15.0 dB T_COMP = 2.5 dBT_TDROP = 4 secHARD_INCLUDED = 0 FRAME_OFFSET = Field OmittedPRIVATE_LCM = Field Omitted RESET_L2 = Field OmittedRESET_FPC = Field Omitted RESERVED = Field OmittedENCRYPT_MODE = Field Omitted RESERVED = Field OmittedNOM_PWR = Field Omitted NUM_PREAMBLE = Field OmittedBAND_CLASS = Field Omitted CDMA_FREQ = Field OmittedADD_LENGTH = 0PILOT_PN = 168 PWR_COMB_IND = 0 CODE_CHAN = 61PILOT_PN = 220 PWR_COMB_IND = 1 CODE_CHAN = 20PILOT_PN = 500 PWR_COMB_IND = 0 CODE_CHAN = 50RESERVED = 0
HANDOFF DIRECTION MESSAGEThe base station sends a HandofDirection Message authorizing the mobile to begin soft handoff with all three requested PNs. The pre-existing link on PN 168 will continue to use Walsh code 61, the new link on PN220 will use Walsh Code 20, and the new link on PN500 will use Walsh code 50.
The mobile acknowledges it has received the Handoff Direction Message.
98/05/24 23:14:02.945 [RTC] Order MessageMSG_LENGTH = 56 bits MSG_TYPE = Order MessageACK_SEQ = 6 MSG_SEQ = 6 ACK_REQ = 0ENCRYPTION = Encryption Mode DisabledORDER = Mobile Station Acknowledgment OrderADD_RECORD_LEN = 0 bitsOrder-Specific Fields = Field Omitted RESERVED = 0
MOBILE STATION ACKNOWLEDGMENT
February, 2005 7 - 83RF100 v2.0 (c) 2005 Scott Baxter
Mobile Implements the Handoff!
The mobile searcher quickly re-checks all three PNs. It still hears their pilots!
The mobile sends a Handoff Completion Message, confirming it still wants to go
ahead with the handoff.
BASE STATION ACKNOWLEDGMENT
98/05/24 23:14:02.985 [RTC] Handoff Completion MessageMSG_LENGTH = 72 bits MSG_TYPE = Handoff Completion MessageACK_SEQ = 6 MSG_SEQ = 1 ACK_REQ = 1ENCRYPTION = Encryption Mode DisabledLAST_HDM_SEQ = 0PILOT_PN = 168 Offset IndexPILOT_PN = 220 Offset IndexPILOT_PN = 500 Offset IndexRESERVED = 0
HANDOFF COMPLETION MESSAGE
The base station confirms it has received the mobile’s Handoff Completion message, and will continue with all of the links active.
98/05/24 23:14:03.085 [FTC] Forward Traffic Channel: Order ACK_SEQ: 1 MSG_SEQ: 1 ACK_REQ: 0 ENCRYPTION: 0 USE_TIME: 0 ACTION_TIME: 0 Base Station Acknowledgement Order
February, 2005 7 - 84RF100 v2.0 (c) 2005 Scott Baxter
Neighbor List Updated, Handoff is Complete!
98/05/24 23:14:03.245 [RTC] Order MessageMSG_LENGTH = 56 bits MSG_TYPE = Order MessageACK_SEQ = 7 MSG_SEQ = 7 ACK_REQ = 0ENCRYPTION = Encryption Mode DisabledORDER = Mobile Station Acknowledgement OrderADD_RECORD_LEN = 0 bitsOrder-Specific Fields = Field OmittedRESERVED = 0
MOBILE STATION ACKNOWLEDGMENT
98/05/24 23:14:03.166 [FTC] Neighbor List Update MessageMSG_LENGTH = 192 bitsMSG_TYPE = Neighbor List Update MessageACK_SEQ = 1 MSG_SEQ = 7 ACK_REQ = 1ENCRYPTION = Encryption Mode DisabledPILOT_INC = 4 Offset IndexNGHBR_PN = 164 Offset IndexNGHBR_PN = 68 Offset IndexNGHBR_PN = 52 Offset IndexNGHBR_PN = 176 Offset IndexNGHBR_PN = 304 Offset IndexNGHBR_PN = 136 Offset IndexNGHBR_PN = 112 Offset IndexNGHBR_PN = 372 Offset IndexNGHBR_PN = 36 Offset IndexNGHBR_PN = 8 Offset IndexNGHBR_PN = 384 Offset IndexNGHBR_PN = 216 Offset IndexNGHBR_PN = 328 Offset IndexNGHBR_PN = 332 Offset IndexNGHBR_PN = 400 Offset IndexNGHBR_PN = 96 Offset IndexRESERVED = 0
NEIGHBOR LIST UPDATE MESSAGE
In response to the mobile’s Handoff Completion Message, the base station assembles a new composite neighbor list including all the neighbors of each of the three active pilots.This is necessary since the mobile could be traveling toward any one of these pilots and may need to request soft handoff with any of them soon.
The mobile confirms receiving the Neighbor List Update Message. It is
already checking the neighbor list and will do so continuously from now on.
The handoff is fully established.
February, 2005 7 - 85RF100 v2.0 (c) 2005 Scott Baxter
Handoff Now In Effect, but still check Pilots!E
c/Io
All PN Offsets
0
032K
512Chips
PN
0
-20
Neighbor Set
Continue checking each ACTIVE pilot. If any are less than T_DROP and remain so for T_TDROP time, send Pilot Strength Measurement Message, DROP IT!!
Continue looking at each NEIGHBOR pilot. If any ever rises above T_ADD, send Pilot Strength Measurement Message, ADD IT!
T_ADD
Rake Fingers
Reference PN
Active Set
10752
16832002
50014080
220
T_DROP
Mobile Rake RX
Srch PN??? W0
F1 PN168 W61F2 PN500 W50F3 PN220 W20
February, 2005 7 - 86RF100 v2.0 (c) 2005 Scott Baxter
The Complete Picture of Handoff & Pilot Sets
T_ADD
Ec/
IoAll PN Offsets
00
32K512
ChipsPN
0
-20
Neighbor Set
SRCH_WIN_N
Active Set
Candidate SetT_DROP
SRCH_WIN_A
Remaining SetT_ADD
SRCH_WIN_R
SRCH_WIN_A
T_DROP
Rake Fingers
Reference PN
Pilots of sectors now used for communication
Pilots requested by mobile but not set up by system
Pilots suggested by system for more checking
All other pilots divisible by PILOT_INC but not presently in Active, Candidate, or Neighbor sets
Mobile Rake RX
Srch PN??? W0
F1 PN168 W61F2 PN500 W50F3 PN220 W20
February, 2005 7 - 87RF100 v2.0 (c) 2005 Scott Baxter
Deeper Handoff Details:Search Windows & TimingDeeper Handoff Details:
Search Windows & Timing
Section G
February, 2005 7 - 88RF100 v2.0 (c) 2005 Scott Baxter
The Pilot Searcher’s Measurement Process
The searcher checks pilots in nested loops, much like meshed gears. Actives and candidatesoccupy the fastest-spinning wheel. Neighbors are next, advancingone pilot for each Act+Cand. revolution.Remaining is slowest, advancing one pilot each time the Neighbors revolve.
CURRENT PILOT SET CONTENTSA A A
C
N N N N N N N N N N N N
R R R R R R R R R R R R
R R R R R R R R R R R R
R R R R R R R R R R R R
R R R R R R R R R R R R
R R R R R R R R R R R R
R R R R R R R R R R R R
R R R R R R R R R R R R
R R R R R R R R R R R R
R R R R R R R R R R R R
R R R R
31
12112
PILOT SEARCHER VIEWED IN SEQUENCE: Typical Elapsed Time = 4 secondsA A A C N
R
A A A C A A A C A A A C A A A C A A A C A A A CN N N N N N
A A A C N A A A C A A A C A A A C A A A C A A A C A A A CN N N N N
A A A CN A A A C A A A C A A A C A A A C A A A C A A A CN N N N N N
N A A A C A A A C A A A CN N N R A A A C N A A A C A A A C A A AN N
C A A A C A A A CN N N
R
A A A C N A A A C A A A C A A AN N C A A AN
C A A A CN N Only 3 of 112 remaining set pilots have been checked thus far!
A
N
R
R
R
R
R
R
R
NN
N
N
NN N N
AA
February, 2005 7 - 89RF100 v2.0 (c) 2005 Scott Baxter
A Quick Primer on Pilot Search WindowsThe phone chooses one strong sector and “locks” to it, accepting its offset at “face value”and interpreting all other offsets by comparison to itIn messages, system gives to handset a neighbor list of nearby sectors’ PNsPropagation delay “skews” the apparent PN offsets of all other sectors, making them seem earlier or later than expectedTo overcome skew, when the phone searches for a particular pilot, it scans an extra wide “delta” of chips centered on the expected offset (called a “search window”) Search window values can be datafilledindividually for each Pilot set:There are pitfalls if the window sizes are improperly set
• too large: search time increases• too small: overlook pilots from far away• too large: might misinterpret identity of a
distant BTS’ signal One chip is 801 feet or 244.14 m
1 mile=6.6 chips; 1 km.= 4.1 chips
PROPAGATION DELAYSKEWS APPARENT PN OFFSETS
BTSBTSA
B
33Chips
4 Chips
If the phone is locked to BTS A, thesignal from BTS B will seem 29 chipsearlier than expected.If the phone is locked to BTS B, thesignal from BTS A will seem 29 chipslater than expected.
February, 2005 7 - 90RF100 v2.0 (c) 2005 Scott Baxter
Setting Pilot Search Window SizesWhen the handset first powers up, it does an exhaustive search for the best pilot. No windows are used in this process.On the paging channel, the handset learns the window sizes SRCH_WIN_A, N, R and uses them when looking for neighbors both in idle mode and during calls.When a strong neighbor is requested in a PSMM, the former neighbor pilot is now a candidate. Its offset is precisely remembered and frequently rechecked and tracked by the phone.Window size for actives and candidates can be small, since their exact position is known. Only search wide enough to include multipath energy!
• This greatly speeds up overall searching!Most post-processing tools deliver statistics on the spread (in chips) between fingers locked to the same pilot. These statistics literally show us how wide the SRCH_WIN_A should be set.Neighbor and Remaining search windows should be set to accommodate the maximum intercelldistances which a mobile might experience
SEARCH WINDOW SETTINGSAND PROPAGATION DISTANCES
Window Size (Chips)
14 (±7)
DatafillValue
N,R Delta Distance
4 1.0620 (±10)
40 (±20)28 (±14)
Miles KM.
56789101112131415
60 (±30)80 (±40)
100 (±50)130 (±65)160 (±80)226 (±113)320 (±160)452 (±226)
1.711.52 2.442.12 3.423.03 4.884.55 7.326.07 9.777.59 12.29.86 15.912.1 19.517.1 27.624.3 39.134.3 55.2
February, 2005 7 - 91RF100 v2.0 (c) 2005 Scott Baxter
Handoff Problems: “Window” Dropped Calls
Calls often drop when strong neighbors suddenly appear outside the neighbor search window and cannot be used to establish soft handoff.Neighbor Search Window SRCH_WIN_N should be set to a width at least twice the propagation delay between any site and its most distant neighbor site Remaining Search Window SRCH_WIN_R should be set to a width at least twice the propagation delay between any site and another site which might deliver occasional RF into the service area
A
B
1 mi.7 Chips
BTS
BTS
SITUATION 1 Locked to distant site, can’t see
one nearby12 miles80 ChipsSRCH_WIN_N = 130BTS A is reference.BTS B appears (7-80) chipsearly due to its closer distance.This is outside the 65-chip window.Mobile can’t see BTS B’s pilot, but its strong signal blinds us and the call drops.
Travel
mountains
A
B
1 mi.7 Chips
BTS
BTS
SITUATION 2Locked to nearby
site, can’t see distant one12 miles80 Chips
Travel
SRCH_WIN_N = 130BTS B is reference.BTS A appears (80-7) chipslate due to its farther distance.This is outside the 65-chip window.Mobile can’t see BTS A’s pilot.
mountains
February, 2005 7 - 92RF100 v2.0 (c) 2005 Scott Baxter
Overall Handoff Perspective
Soft & Softer Handoffs are preferred, but not always possible• a handset can receive BTS/sectors simultaneously only on one
frequency • all involved BTS/sectors must connect to a networked BSCs.
Some manufacturers do not presently support this, and so are unable to do soft-handoff at boundaries between BSCs.
• frame timing must be same on all BTS/sectorsIf any of the above are not possible, handoff still can occur but can only be “hard” break-make protocol like AMPS/TDMA/GSM
• intersystem handoff: hard• change-of-frequency handoff: hard• CDMA-to-AMPS handoff: hard, no handback
– auxiliary trigger mechanisms available (RTD)
February, 2005 7 - 93RF100 v2.0 (c) 2005 Scott Baxter
Section H
CDMA Network ArchitectureCDMA Network Architecture
February, 2005 7 - 94RF100 v2.0 (c) 2005 Scott Baxter
BASE STATIONCONTROLLER
SUPPORTFUNCTIONS
BASE STATIONS
Mobile TelephoneSwitching Office
PSTNLocal CarriersLong Distance
CarriersATM Link
to other CDMANetworks(Future)
Structure of a Typical Wireless SystemHLR
Voice Mail System SWITCH
HLR Home Location Register(subscriber database)
February, 2005 7 - 95RF100 v2.0 (c) 2005 Scott Baxter
Signal Flow: Two-Stage Metamorphosis
BSC-BSMMTX BTS
Ch. Card ACC
Σα
Σβ
Σχ
TFU1
GPSRBSM
CDSU
CDSU
SBSVocodersSelectors
CDSU
CDSU
CDSU
CDSU
CDSU
CMSLM
LPP LPPENET
DTCs
DMS-BUS
TxcvrA
TxcvrB
TxcvrC
RFFEA
RFFEB
RFFEC
TFU
GPSR
GPS GPS
IOC
PSTN
CDSU DISCOCDSU
DISCO 1
DISCO 2
DS0 in T1Packets
ChipsRFChannel
ElementVocoder
February, 2005 7 - 96RF100 v2.0 (c) 2005 Scott Baxter
Nortel CDMA Network Architecture
Nortel CDMA Network Architecture
www.nortel.com
February, 2005 7 - 97RF100 v2.0 (c) 2005 Scott Baxter
NORTEL CDMA System Architecture
BSC-BSMMTX BTS
CDSU DISCO
Ch. Card ACC
Σα
Σβ
Σχ
TFU1
GPSRBSM
CDSU
CDSU
DISCO 1
DISCO 2
SBSVocodersSelectors
CDSU
CDSU
CDSU
CDSU
CDSU
CDSU
CMSLM
LPP LPPENET
DTCs
DMS-BUS
TxcvrA
TxcvrB
TxcvrC
RFFEA
RFFEB
RFFEC
TFU
GPSR
PSTN & Other MTXs
GPS GPS
IOC
Billing
February, 2005 7 - 98RF100 v2.0 (c) 2005 Scott Baxter
Switch: The Nortel MTX
Primary functions• Call Processing• Mobility Management
– HLR-VLR access– Intersystem call delivery (IS-41C)– Inter-MTX handover (IS-41C)
• Billing Data Capture• Calling Features & Services• Collecting System OMs, Pegs
High reliability, redundancy
MTX
CMSLM
LPP ENET
DTCs
DMS-BUS
PSTN & Other MTXs
CDMABSC
Unch. T1
IOC
CDMASBS
MAP,VDUs
Billing
LPP
CCS7
Ch.T1
ChT1
February, 2005 7 - 99RF100 v2.0 (c) 2005 Scott Baxter
The Nortel BSC
Primary functions• vocoding• soft handoff management• FER-based power control• routing of all traffic and control
packetsScaleable architecture
• expand SBS to keep pace with traffic growth
• expandable DISCO
BSC
TFU1
GPSRBSM
CDSUCDSU
DISCO 1
DISCO 2
SBSVocodersSelectors
CDSU
CDSU
CDSU
CDSU
CDSU
CDSU
GPS
MTX(voicetrunks)
MTXLPP
BTSs
T1 channelized (24 DS0)T1 unchannelizedBCN link (HDLC)
February, 2005 7 - 100RF100 v2.0 (c) 2005 Scott Baxter
The Nortel BTS
Base Transceiver StationPrimary function: Air link
• generate, radiate, receive CDMA RF signal IS-95/J.Std. 8
• high-efficiency T1 backhaul• test capabilities
Configurations• 1, 2, or 3 sectors• 800 MHz.: indoor• 1900 MHz.: self-contained outdoor,
remotable RFFEs• new 1900 MHz. indoor, 800 MHz. &
1900 MHz. multi-carrier options
BTS
CDSU DISCO
Ch. Card ACC
Σα
Σβ
Σχ
TxcvrA
TxcvrB
TxcvrC
RFFEA
RFFEB
RFFEC
TFU
GPSRGPS
BSC
February, 2005 7 - 101RF100 v2.0 (c) 2005 Scott Baxter
The Nortel BSM
Base Station ManagerPrimary functions: OA&M for CDMA components
• Configuration management– BSC, BTS configuration and
parameters• Fault management
– Alarm Reporting• Performance management
– interface for CDMA statistics and peg counts collection
• Security management• Unix-based
BSC BTS
CDSU DISCO
Ch. Card ACC
Σα
Σβ
Σχ
TFU1
GPSR
CDSU
CDSU
DISCO 1
DISCO 2
SBSVocodersSelectors
CDSU
CDSU
CDSU
CDSU
CDSU
CDSU
TxcvrA
TxcvrB
TxcvrC
RFFEA
RFFEB
RFFEC
TFU
GPSR
GPS GPS
BSM
X-Windows terminals
Ethernet LAN
BSM Workstation
GNP TELCOWORKSERVER
SHELF---------HIGH
AVAILABILITY
NORTEL CDMA BSM
BCN Links
February, 2005 7 - 102RF100 v2.0 (c) 2005 Scott Baxter
Summary of CDMA Capacity Considerations
BSC-BSMMTX BTS
Ch. Card ACC
Σα
Σβ
Σχ
TFU1
GPSRBSM
CDSU
CDSU
SBSVocodersSelectors
CDSU
CDSU
CDSU
CDSU
CDSU
CMSLM
LPP LPPENET
DTCs
DMS-BUS
TxcvrA
TxcvrB
TxcvrC
RFFEA
RFFEB
RFFEC
TFU
GPSR
GPSGPS
IOC
PSTN
CDSU DISCOCDSU
DISCO 1
DISCO 2
Sufficient vocoders/selectors required in BSC SBS, one per
simultaneous call on the system. 8 Vocoders per SBS card, 12 cards per shelf, 4 shelves per
SBS cabinet.
One T-1 can carry all traffic originated by a
one-carrier BTS; special consideration required if
daisy-chaining
Forward RF Capacity: links use available
BTS TX power
Sufficient channel elements required for traffic of all sectors: one CE per link; 20
CE per Channel Card
64 Walsh Codes/sector
64 Walsh Codes/sector
64 Walsh Codes/sector
DISCO has 192 ports
max. Each BTS uses 1, SBS shelf 1, LPP CIU 1,
Link 2, Ctrl. 2, BSM 4.
Typical CM processorcapacity considerations
PSTN trunk groups must be dimensioned to
support erlang load.
DTC & ENET: One port per Vocoder plus one port per
outgoing trunk.
CDMA LPP: One pair CIUs and One pair CAUs per
approx. 600 erlangs
Reverse RF Capacity: links cause noise floor rise, use mobile power
February, 2005 7 - 103RF100 v2.0 (c) 2005 Scott Baxter
Lucent CDMA Network Architecture
Lucent CDMA Network Architecture
www.lucent.com
February, 2005 7 - 104RF100 v2.0 (c) 2005 Scott Baxter
Lucent CDMA System Architecture
5ESS-2000 DCSECP BTS
ChannelUnit
Cluster
ACU
Σα
Σβ
Σχ
Baseband Combiner & Radio
Baseband Combiner & Radio
Baseband Combiner & Radio
PSTN & Other MTXs
ExecutiveCellular
Processor Complex (ECPC)
Circuit SwitchPlatform
CDMA SpeechHandling Equipment
Packet SwitchPlatform
February, 2005 7 - 105RF100 v2.0 (c) 2005 Scott Baxter
The Lucent ECP
Executive Cellular ProcessorPrimary functions
• Call Processing• Mobility Management
– HLR-VLR access– Intersystem call delivery (IS-41C)– Inter-MTX handover (IS-41C)
• Billing Data Capture• Calling Features & Services• Collecting System OMs, Pegs
High reliability, redundancy
ECP
ExecutiveCellular
Processor Complex (ECPC)
February, 2005 7 - 106RF100 v2.0 (c) 2005 Scott Baxter
The Lucent #5ESS and Access Manager
Primary functions• vocoding• soft handoff management• FER-based power control• routing of all traffic and control
packetsScaleable architecture
• expand speech handlers• expandable packet switch
5ESS-2000 DCS
PSTN & Other MTXs
Circuit SwitchPlatform
CDMA SpeechHandling Equipment
Packet SwitchPlatform
February, 2005 7 - 107RF100 v2.0 (c) 2005 Scott Baxter
The Lucent BTS
Primary function: Air link • generate, radiate, receive
CDMA RF signal IS-95/J.Std. 8• high-efficiency T1 backhaul• test capabilities
BTSChannel
UnitCluster
ACU
Σα
Σβ
Σχ
Baseband Combiner & Radio
Baseband Combiner & Radio
Baseband Combiner & Radio
February, 2005 7 - 108RF100 v2.0 (c) 2005 Scott Baxter
Motorola CDMA Network Architecture
Motorola CDMA Network Architecture
www.motorola.com
February, 2005 7 - 109RF100 v2.0 (c) 2005 Scott Baxter
Motorola CDMA System ArchitectureOMC-R
CBSC
PCSCPersonal
CommunicationsSwitching
Center
PSTNDSC
EMX-2500or
EMX-5000
Mobility Manager
Transcoder
OMC-RProcessor
ApplicationProcessor
(or SC-UNO)
BTS (SC9600/4800/2400)
Group LineInterface (GLI)
MultichannelCDMA Card (MCC)
BTS (SC614T/611)
MotorolaAdvancedWidebandInterface(MAWI)
PCLocal
MaintenanceFacility
February, 2005 7 - 110RF100 v2.0 (c) 2005 Scott Baxter
The Motorola PCSC
Personal Communications Switching CenterPrimary functions
• Call Processing• HLR-VLR access• Intersystem call delivery (IS-41C)• Billing Data Capture• Calling Features & Services
PSTNDSC
EMX-2500or
EMX-5000
EMX-2500
EMX-5000
February, 2005 7 - 111RF100 v2.0 (c) 2005 Scott Baxter
The Motorola CBSC
Centralized Base Station ControllerMobility Manager
• allocation of BTS resources• handoff management• Call management & supervision
Transcoder• vocoding• soft handoff management• FER-based power control• routing of all traffic and control
packets
CBSC
Mobility Manager
Transcoder
February, 2005 7 - 112RF100 v2.0 (c) 2005 Scott Baxter
The Motorola BTS Family
Primary function: Air link • generate, radiate, receive
CDMA RF signal IS-95/J.Std. 8
• high-efficiency T1 backhaul
• test capabilitiesBTS (SC9600/4800/2400)
Group LineInterface (GLI)
MultichannelCDMA Card (MCC)
BTS (SC614T/611)
MotorolaAdvancedWidebandInterface(MAWI)
PCLocal
MaintenanceFacility
SC611 Microcell
SC4852SC614T
February, 2005 7 - 113RF100 v2.0 (c) 2005 Scott Baxter
Section I
Introduction to OptimizationIntroduction to Optimization
February, 2005 7 - 114RF100 v2.0 (c) 2005 Scott Baxter
What is Performance Optimization?
The words “performance optimization” mean different things to different people, viewed from the perspective of their own jobsSystem Performance Optimization includes many different smaller processes at many points during a system’s life
• recognizing and resolving system-design-related issues (can’t build a crucial site, too much overlap/soft handoff, coverage holes, etc.)
• “cluster testing” and “cell integration” to ensure that new base station hardware works and that call processing is normal
• “fine-tuning” system parameters to wring out the best possible call performance
• identifying causes of specific problems and customer complaints, and fixing them
• carefully watching system traffic growth and the problems it causes - implementing short-term fixes to ease “hot spots”, and recognizing problems before they become critical
February, 2005 7 - 115RF100 v2.0 (c) 2005 Scott Baxter
Performance Optimization Phases/Activities
hello
RF Design and Cell Planning
New Cluster Testing and
Cell Integration
Solve SpecificPerformance
Problems
Well-System Performance Management
Capacity Optimization
Growth Management:
Optimizing both Performance and Capital
Effectiveness
Cover desired area; have capacity for anticipated traffic
Ensure cells properly constructed and
configured to give normal performance
Identify problems from complaints or statistics; fix them!
Ensure present ‘plant’is giving best possible
performance
Manage congested areas for most
effective performance
Overall traffic increases and congestion;
competition for capital during tight times
Phase Drivers/Objectives Activities Main Tools Success Indicators
Plan cells to effectively cover as needed and divide traffic
load appropriately
Drive-test: coverage, all handoff boundaries, all call
events and scenarios
Detect, Investigate, Resolve performance problems
Watch stats: Drops, Blocks, Access Failures; identify/fix hot
spots
Watch capacity indicators; identify problem areas, tune parameters & configuration
Predict sector and area exhaustion: plan and validate effective growth plan, avoid
integration impact
Prop. Models,Test Transmitters,
planning tools Model results
Drive-test tools;cell diagnostics and
hardware test
All handoffs occur; all test cases
verified
Drive-test tools, system stats,
customer reports
Identified problems are
resolved
System statisticsAcceptable levels and good trends for all indicators
Smart optimization of parameters;
system statistics
Stats-Derived indicators; carried
traffic levels
Traffic analysis and trending tools;
prop. models for cell spliiting; carrier
additions
Sectors are expanded soon
after first signs of congestion;
capital budget remains within
comfortable bounds
February, 2005 7 - 116RF100 v2.0 (c) 2005 Scott Baxter
Good Performance is so Simple!!
One, Two, or Three good signals in handoff• Composite Ec/Io > -10 db
Enough capacity• No resource problems – I’ve got what I
need
BTS BTS
BTS
Pilot
Paging
TrafficChannels
In use
availablepower
Sync
BTS
A
BTS
B
BTS
C
Ec/Io -10
FORWARDLINK
February, 2005 7 - 117RF100 v2.0 (c) 2005 Scott Baxter
Bad Performance Has Many CausesWeak Signal / Coverage HolePilot Pollution
• Excessive Soft HandoffHandoff Failures, “Rogue” mobiles
• Missing Neighbors• Search Windows Too Small• BTS Resource Overload / No Resources
– No Forward Power, Channel Elements
– No available Walsh Codes– No space in Packet Pipes
Pilot “Surprise” ambush; Slow HandoffsPN Plan errorsSlow Data Problems: RF or IP congestionImproper cell or reradiator configurationHardware and software failuresBut on analysis, all of these problems’ bad effects happen because the simple few-signal ideal CDMA environment isn’t possible.
360
+41
+8
360+33cA
BBTS
BTS
BTS BPN 99
BTS APN 100
1 mile 11 miles
ACTIVE SEARCH WINDOW
xPilot
PagingSync
TrafficChannels
In Use
NoAvailablePower!B
TS Sector Transmitter
CEsVocodersSelectors
BTS Rx PwrOverload
February, 2005 7 - 118RF100 v2.0 (c) 2005 Scott Baxter
Aeronautical Analogy: Tools for Problem Investigation
To study the cause of an aeronautical accident, we try to recover the Flight Data Recorder and the Cockpit Voice Recorder.
To study the cause of a CDMA call processing accident, we review data from the Temporal Analyzer and the Layer 3 Message Files -- for the same reasons.
Control & Parameters Messaging
BTS
1150011500
114.50118.25125.75
AeronauticalInvestigations
CDMAInvestigations
Flight Data Recorder Cockpit Voice Recorder
Temporal Analyzer Data Layer 3 Message Files
February, 2005 7 - 119RF100 v2.0 (c) 2005 Scott Baxter
Starting Optimization on a New SystemRF Coverage Control
• try to contain each sector’s coverage, avoiding gross spillover into other sectors
• tools: PN Plots, Handoff State Plots, Mobile TX plotsSearch Window Settings
• find best settings for SRCH_WIN_A, _N, _R• especially optimize SRCH_WIN_A per sector using collected
finger separation data; has major impact on pilot search speedNeighbor List Tuning
• try to groom each sector’s neighbors to only those necessary but be alert to special needs due to topography and traffic
• tools: diagnostic data, system logsAccess Failures, Dropped Call Analysis
• finally, iterative corrections until within numerical goals
Getting these items into shape provides a solid baseline and foundation from which future performance issues can be addressed.
February, 2005 7 - 120RF100 v2.0 (c) 2005 Scott Baxter
Solving Problems on Existing Systems
CDMA optimization is very different from optimization in analog technologies such as AMPS
AMPS: a skilled engineer with a handset or simple equipment can hear, diagnose, and correct many common problems
• co-channel, adjacent channel, external interferences• dragged handoffs, frequency plan problems
CDMA impairments have one audible symptom: Dropped Call• voice quality remains excellent with perhaps just a hint of garbling
even as the call approaches dropping in a hostile RF environment
Successful CDMA Optimization requires:• recognition and understanding of common reasons for call failure• capture of RF and digital parameters of the call prior to drop• analysis of call flow, checking messages on both forward and reverse
links to establish “what happened”, where, and why
February, 2005 7 - 121RF100 v2.0 (c) 2005 Scott Baxter
CDMA Problems Attacked in Optimization
Excessive Access Failures• typical objectives: <2% (IS-95B will bring improvements)
Excessive Dropped Calls• typical objective: ~1%, <2%
Forward Link Interference• typical objective: eliminate situations which prevent handoff!
Slow Handoff• typical objective: eliminate situations which delay handoff!
Handoff Pilot Search Window Issues• avoid handoff drops!
Excessive Soft Handoff• control coverage, not T_Add/T_Drop, to manage soft handoff levels (~<50%)
Grooming Neighbor Lists• “if you need it, use it!”
Software Bugs, Protocol Violations• Neither system software, nor mobile software, nor the CDMA standard is
perfect. Don’t humbly accept problems -- dig in and find out what’s happening!
February, 2005 7 - 122RF100 v2.0 (c) 2005 Scott Baxter
Sources of CDMA Data and Tools for Processing
CDMA optimization data flows from three places:• Switch• CDMA peripherals (CBSC & BTS)• Handset
Each stream of data has a family of software and hardware tools for collection and analysis
CBSCSwitch BTS
CDSU DISCO
Ch. Card ACC
ΣαΣβΣχ
TFU1GPSR
CDSUCDSU
DISCO 1DISCO 2
SBSVocodersSelectors
CDSUCDSUCDSUCDSUCDSUCDSU
CMSLM
LPP LPPENET
DTCs
DMS-BUS
Txcvr ATxcvr BTxcvr C
RFFE ARFFE BRFFE C
TFU1GPSR
IOC
BSM
Data AnalysisPost-Processing
Tools
IS-95/J-STD-008 Messages
IS-95/J-STD-8 Messages
Switch Datapegs, logs
Mobile DataPost-Processing
Tools
Mobile Data Capture Tools
HandsetMessages
ExternalAnalysis
Tools
PC-based
PC-based
Unix-based,PC-basedVarious
CDMA NETWORK EQUIPMENT HANDSET
System Internal Messages
February, 2005 7 - 123RF100 v2.0 (c) 2005 Scott Baxter
Department Store Analogy: Tops-Down, Bottoms-Up
Some things are easier to measure from the customer side!
Complex!!! Simpler
System Phone
Neighbor ListsData Analysis
SoftwareTrans-
mission
Configuration
Provisioning
PSTN Trunking
Dropped Calls
CoverageAccess Failures
Switch
BTS
CBSC
InterferenceAdministration
Data CaptureField Tools
Profits
Complex!!! Simpler
Management Test Shopper
Labor Relations
Cost
sTaxe
s Insurance
Suppliers
Leases
Capital
Stocking
Distribution
Loss
esAdvertis
ing
Selection
ConveniencePrice
Service
February, 2005 7 - 124RF100 v2.0 (c) 2005 Scott Baxter
Aeronautical Analogy: Tools for Problem Investigation
To study the cause of an aeronautical accident, we try to recover the Flight Data Recorder and the Cockpit Voice Recorder.
To study the cause of a CDMA call processing accident, we review data from the Temporal Analyzer and the Layer 3 Message Files -- for the same reasons.
Control & Parameters Messaging
BTS
1150011500
114.50118.25130.75
AeronauticalCase
CDMA Case
Flight Data Recorder Cockpit Voice Recorder
Temporal Analyzer Data Layer 3 Message Files
February, 2005 7 - 125RF100 v2.0 (c) 2005 Scott Baxter
So S L O W ! ! Where’s My Data?!!
Some sessions are tormented by long latency and slow throughputWhere is the problem? Anywhere between user and distant host:
• Is the mobile user’s data device mis-configured and/or congested?• Is the BTS congested, with no power available to produce an SCH?• Poor RF environment, causing low rates and packet retransmission?• Congestion in the local IP network (PCU, R-P, PDSN FA)?• Congestion in the wireless operator’s backbone (‘OSSN’) network?• Congestion in the PDSN HA?• Congestion in the outside-world internet or Private IP network?• Is the distant host congested, with long response times?
IP D
ata
Envir
onm
entCDMA RF Environment
CDMA IOS PPPTraditional Telephony
IP Data Environment
t1t1 v CESEL
t1
R-P Interface
PDSN/Foreign Agent
PDSNHome Agent
BackboneNetworkInternet
VPNs
PSTN
T TSECURE TUNNELS
AuthenticationAuthorization
AccountingAAA
BTS
(C)BSC/Access ManagerSwitch WirelessMobile Device
•Coverage Holes•Pilot Pollution•Missing Neighbors•Fwd Pwr Ovld•Rev Pwr Ovld•Search Windows•Island Cells•Slow Handoff
February, 2005 7 - 126RF100 v2.0 (c) 2005 Scott Baxter
Finding Causes of Latency and Low Throughput
IP network performance can be measured using test serversProblems between mobile a local test server? The problem is local
• check RF conditions, stats: poor environment, SCH blocking?• if the RF is clean, investigate BSC/PCU/R-P/PDSN-FA
Local results OK, problems accessing test server at PDSN-HA?• problem is narrowed to backbone network, or PDSN-HA
Results OK even through test server at PDSN-HA• then the problem is in the public layers beyond.
IP D
ata
Envir
onm
entCDMA RF Environment
CDMA IOS PPPTraditional Telephony
IP Data Environment
t1t1 v CESEL
t1
R-P Interface
PDSN/Foreign Agent
PDSNHome Agent
BackboneNetworkInternet
VPNs
PSTN
T TSECURE TUNNELS
AuthenticationAuthorization
AccountingAAA
BTS
(C)BSC/Access ManagerSwitch WirelessMobile Device
•Coverage Holes•Pilot Pollution•Missing Neighbors•Fwd Pwr Ovld•Rev Pwr Ovld•Search Windows•Island Cells•Slow Handoff
TestServer
TestServer
TestServer
February, 2005 7 - 127RF100 v2.0 (c) 2005 Scott Baxter
Autonomous Data CollectionBy Subscriber Handsets
Autonomous Data CollectionBy Subscriber Handsets
February, 2005 7 - 128RF100 v2.0 (c) 2005 Scott Baxter
Autonomous Collection:A New Way to See Network Performance
An exciting new trend in network RF performance is to embed datacollection software on mobile platformsOffers big advantages for RF optimization cost/effectiveness
t1t1 v SEL
t1
R-P Interface
PDSN/Foreign Agent
PDSNHome Agent
BackboneNetworkInternet
VPNs
PSTN
T TSECURE TUNNELS
AuthenticationAuthorization
AccountingAAA
BTS
(C)BSC/Access ManagerSwitch
Collection Server•software download•collected data upload•data management, analysis
BTS
BTS
BTS
February, 2005 7 - 129RF100 v2.0 (c) 2005 Scott Baxter
Using Autonomous Collection
A Server downloads software to a large population of subscriber mobilesMobiles collect on custom profiles
• all or groups of mobiles can be enabled/disabled• new triggers can be rapidly developed and downloaded when desired
Mobiles upload compacted packets to server driven by custom triggers• may be immediately if needed, or at low-traffic pre-programmed times• collected data can include location/GPS/call event/L3
messaging/timestamps/etc.Server manages data, provides filtering and reportingPerformance optimizers use terminals and post-processing software
t1t1 vSELt1
R-P Interface
PDSN/Foreign Agent
PDSNHome Agent
BackboneNetworkInternet
VPNs
PSTN
T TSECURE TUNNELSAuthentication
AuthorizationAccounting
AAABTS
(C)BSC/Access ManagerSwitch
Collection Server•software download•collected data upload•data management, analysis
BTS
BTS
BTS
February, 2005 7 - 130RF100 v2.0 (c) 2005 Scott Baxter
Advantages of Autonomous Collection
Mobile-reported data can be location-binned
• post-processing provides visual identification of problem areas
Collection can be rapidly enabled per cell or area for immediate investigation of problem reportsRequires less employee drive time for collectionCustomer mobiles cover area more densely than drivetestersCustomer mobiles include in-building populationsIndividual mobile identification can be included with customer permission for direct customer service interaction
February, 2005 7 - 131RF100 v2.0 (c) 2005 Scott Baxter
Conventional Field ToolsConventional Field Tools
February, 2005 7 - 132RF100 v2.0 (c) 2005 Scott Baxter
CDMA Field Test ToolsField Collection Tools using Handset Data
There are many commercial CDMA field test toolsCharacteristics of many test tools:
• capture data from data ports on commercial handsets• log data onto PCs using proprietary software• can display call parameters, messaging, graphs, and maps• store data in formats readable for post-processing analysis• small and portable, easy to use in vehicles or even on foot
A few considerations when selecting test tools:• does it allow integration of network and mobile data?• Cost, features, convenience, availability, and support• new tools are introduced every few months - investigate!
QualcommMDM, CAIT
Grayson
Comarco
Willtech
EricssonTEMS
Motorola
PN Scanners
Agilent(HP + SAFCO)
Agilent(HP + SAFCO)
BerkeleyVaritronics
Grayson Qualcomm
DTI Willtech
February, 2005 7 - 133RF100 v2.0 (c) 2005 Scott Baxter
Qualcomm’s MDM: Mobile Diagnostic Monitor
The Qualcomm Mobile Diagnostic Monitor was the industry’s first field diagnostic tool
• used industry-wide in the early deployment of CDMA
• pictures at right from Sprint’s first 1996-7 CDMA trials in Kansas City
Qualcomm’s Mobile Diagnostic Monitor • CDMA handset (customer provided)• Proprietary connecting cable• PC software for collection and field pre-
analysis– Temporal analyzer display mode– Messaging
February, 2005 7 - 134RF100 v2.0 (c) 2005 Scott Baxter
Grayson’s Invex3G Tool
100 MB ethernet connection to PCthe eight card slots can hold receivers or dual-phone cardsthere’s also room for two internal PN scannersMultiple Invex units can be cascaded for multi-phone load-test applicationsCards are field-swappable -Users can reconfigure the unit in the field for different tasks without factory assistance
February, 2005 7 - 135RF100 v2.0 (c) 2005 Scott Baxter
This mobile is in a 2-way soft handoff (two green FCH walsh codes assigned) in the middle of a downlink SCH burst. Notice walsh code #3, 4 chips long, is assigned as an SCH but only on one sector, and the downlink data speed is 153.6kb/s.
153.6kb/s
Grayson Invex 1x Data Example
February, 2005RF100 v2.0 (c) 2005 Scott BaxterTechnical Introduction to Wireless -- ©1997 Scott Baxter - V0.0 136
F-SCH rates 153.6 kbps; R-SCH 76.8kbps
PN Scanner Data
Grayson Invex 1xData Example
Current Data Task StatusLayer-3 Messages
CDMA Status
February, 2005 7 - 137RF100 v2.0 (c) 2005 Scott Baxter
WillTech Tools
Blue Rose platform can manage multiple phones and collect data
• Internal processor manages test operations independently for stand-alone operation
• Internal PCMCIA flash card provides storage
• An external PC can display collected data during or after data collection
February, 2005 7 - 138RF100 v2.0 (c) 2005 Scott Baxter
Agilent Drive-Test Tools
Agilent offers Drive-Test tools• Serial interfaces for up to four
CDMA phones• A very flexible digital receiver
with several modesPN Scanner
• Fast, GPS-locked, can scan two carrier frequencies
Spectrum Analyzer• Can scan entire 800 or 1900
mHz. BandsBase-Station Over-Air Tester (BOAT)
• Can display all walsh channel activity on a specific sector
• Useful for identifying hardware problems, monitoring instantaneous traffic levels, etc.
Post-Processing tool: OPAS32
February, 2005 7 - 139RF100 v2.0 (c) 2005 Scott Baxter
Comarco Mobile Tools
X-Series Units for more data-intensive collection activities
• Multiple handsets can be collected
• Data is displayed and collected on PC
LT-Series provides integrated display and logging"Workbench" Post-Processing tool analyzes drive-test files
February, 2005 7 - 140RF100 v2.0 (c) 2005 Scott Baxter
PN Scanners
Why PN scanners? Because phones can’t scan remaining set fast enough, miss transient interfering signalsBerkeley Varitronics
• high-resolution, GPS-locked– full-PN scan speed 26-2/3 ms.
• 2048 parallel processors for very fast detection of transient interferors
Agilent (formerly Hewlett-Packard)• high resolution, GPS-locked
– full-PN scan speed 1.2 sec.• Integrated with spectrum analyzer and
phone call-processing toolGrayson Wireless
• New digital receiver provides CDMA PN searcher and and sector walsh domain displays
February, 2005 7 - 141RF100 v2.0 (c) 2005 Scott Baxter
Post-Processing ToolsPost-Processing tools display drive-test files
for detailed analysis - Faster, more effective than studying data playback with collection tools aloneActix Analyzer
• Imports/analyzes data from almost every brand of drive-test collection tool
Grayson Interpreter• Imports/analyzes data from Grayson
Wireless Inspector, Illuminator, and Invex3G
Agilent OPAS32• Imports/analyzes a variety of data
Nortel RF Optimizer• Can merge/analyze drive-test and
Nortel CDMA system dataWavelinkComarco "Workbench" ToolVerizon/Airtouch internal tool “DataPro”
OPAS32
COMARCO
February, 2005 7 - 142RF100 v2.0 (c) 2005 Scott Baxter
Maintenance Features of CDMA Handsets
Maintenance Features of CDMA Handsets
Drive-Tests: Phones
February, 2005 7 - 143RF100 v2.0 (c) 2005 Scott Baxter
Handsets as Tools: Simple but always Available!
Most CDMA handsets provide some form of maintenance display (“Debug Mode”) as well as instrumentation access
• all CDMA drive-test tools use handsets as their “front-ends”Using the handset as a manual tool without Commercial Test Tools:
Enter the maintenance mode by special sequence of keystrokesDisplayed Parameters
• PN Offset, Handset Mode, Received RF Level , Transmit Gain AdjustMaintenance Display Applications
• best serving cell/sector• simple call debugging (symptoms of weak RF, forward link
interference, etc.)Handset Limitations during manual observation
• no memory: real-time observations only; no access to messages or call details; serving PN offset not updated during voice calls
February, 2005 7 - 144RF100 v2.0 (c) 2005 Scott Baxter
Older Qualcomm/Sony Maintenance Displays
MAIN MENU 1:Volume2:Call Info3:Security
D
FEATURES 41:AutoAnswer2:AutoRetry3:Scratch
D
Menu
4
0
ENTER FIELDSERVICE CODE
******
D
DEBUG 01:Screen2:Test Calls3:CDMA Only
D
DEBUG 04:Errors5:Clr Errors6:13K Voice
D
318 2 9DX A 7F
D
1
00000 0See following
legend for maintenance
display values(* or correct code, if different)
Press This: See This: continue: See This:
*
*
February, 2005 7 - 145RF100 v2.0 (c) 2005 Scott Baxter
Qualcomm & Sony Phones with Jog Dials
Enter 111111Press dial in for OPTIONSDial to FIELD DEBUG, pressenter Field Debug Security Codepress Screen
February, 2005 7 - 146RF100 v2.0 (c) 2005 Scott Baxter
Interpreting the QCP Maintenance Display
318 2 94X A 7F
D
PN Offset
0 - Pilot Channel Acquisition Substate1 - Sync Channel Acquisition Substate2 - MS Idle State3 - System Access State4 - Traffic Channel State
Receive State
Receive Power
UnsupportedA = active pilotsX = exit reason
Transmit Adjust80 -10980 -10900 00A -514 -101E -1528 -20
FFF5E6D7C8B9AA9B8C80
-67-70-75-80-85-90-95-100-105-109
QCP-1900
QCP-800
-64-67-72-77-82-87-92-97-102-106
Receive Power Conversion:RXdbm=XXDEC / 3 - 63.25 (800 MHz)RXdbm=XXDEC / 3 - 66.25 (1900 MHz)(if XX>7F, use XX = XXDEC-256)Transmit Gain Adjust Conversion:TXADJdb=XXDEC / 2Transmit Power Output Conversion:TXdbm= -73 -RXDBM - TXADJdb (800 MHz)TXdbm= -76 -RXDBM - TXADJdb (1900 MHz)
February, 2005 7 - 147RF100 v2.0 (c) 2005 Scott Baxter
Kyocera 2035 Maintenance Mode
Steps to enter maintenance mode:111111EnterOptions: DebugEnterEnter Field Debug Code
• 000000Field DebugDebug ScreenEnterBasicEnter
February, 2005 7 - 148RF100 v2.0 (c) 2005 Scott Baxter
Kyocera 6035 Maintenance Mode
111111Jog > OptionsJog > DebugOpen flip to continueEnter Code
• 0 0 0 0 0 0OKSCREEN
February, 2005 7 - 149RF100 v2.0 (c) 2005 Scott Baxter
Early Samsung Maintenance Display
8
01
00000 0See following
legend for maintenance
display values(* or correct code, if different)
Press This: See This: continue: See This:
*
*
Menu Main Menu ↑1:Call Logs2:Phone Book
SVC
Setup ↑1:Auto Retry2:Anykey Ans
SVC
Service Code??????
SVC
Debug Menu ↑1:Screen2:Test Calls
SVC
Debug Menu ↑3:Errors4:Erase Error
SVC
S04379 SI0 1T-63 D105-06P016 CH0600
SVC
February, 2005 7 - 150RF100 v2.0 (c) 2005 Scott Baxter
Samsung SCH-3500 Maintenance Display
Here are the steps to enter maintenance mode:MENUSETUP0 (undocumented “trap door”)000000 (operator’s code)Screen
See the Samsung idle and in-call maintenance screens at the end of the Samsung phones.
February, 2005 7 - 151RF100 v2.0 (c) 2005 Scott Baxter
Samsung SCH-8500 Maintenance Display
Here are the steps to enter maintenance mode:[Menu] [down][down][down][down] [down][down][down] Setup/Tool [OK] [0] Service Code ?????? [0] [4] [0] [7] [9] [3] Screen [OK]
See the Samsung idle and in-call maintenance screens at the end of the Samsung phones.
February, 2005 7 - 152RF100 v2.0 (c) 2005 Scott Baxter
Samsung SCH-A500 Maintenance Display
Here are the steps to enter maintenance mode:Select settingsselect displayselectenter 0enter 040793
See the Samsung idle and in-call maintenance screens at the end of the Samsung phones.
February, 2005 7 - 153RF100 v2.0 (c) 2005 Scott Baxter
Samsung SCH-A460 Maintenance Display
Enter the following to enter maintenance mode:# # D E B U G[OK][OK]
See the Samsung idle and in-call maintenance screens at the end of the Samsung pages.
February, 2005 7 - 154RF100 v2.0 (c) 2005 Scott Baxter
Samsung “Uproar” Maintenance Display
The “uproar” is no longer in production but included an MP3 player -- the ultimate consumer device.If you’re still enjoying one, here are the steps to enter the maintenance display:
1. Press the MENU button.2. Press 9 on the keypad.3. Then press and hold the * key
until the field service code screen appears.
4. Then type in the field service code 040793
February, 2005 7 - 155RF100 v2.0 (c) 2005 Scott Baxter
Interpreting Samsung Maintenance Display:Acquisition, Idle, and Access States
Transmit Power Output Calculation:TXdbm= -73 -RXDBM - TXADJdb (800 MHz)TXdbm= -76 -RXDBM - TXADJdb (1900 MHz)
S04379 SI0 1T-63 D085-06P016 CH0600
svc
PN Offset
0 - Pilot Channel Acquisition Substate1 - Sync Channel Acquisition Substate2 - MS Idle State3 - System Access State4 - Traffic Channel State5,6,7 - various call service options
Processing StateReceive Power,
dbmTransmit
Gain Adjust,db
Display toggles between:System Identifier (SID)Network Identifier (NID)
Frequency(channel #)
Ec/Io, db(primary PN only)
Slot Cycle Index
February, 2005 7 - 156RF100 v2.0 (c) 2005 Scott Baxter
Interpreting Samsung Maintenance Display:Traffic Channel State
Transmit Power Output Calculation:TXdbm= -73 -RXDBM - TXADJdb (800 MHz)TXdbm= -76 -RXDBM - TXADJdb (1900 MHz)
TV1 RV8 08 7T-63 D085-06P016 CH0600
svc
PN Offset
0 - Pilot Channel Acquisition Substate1 - Sync Channel Acquisition Substate2 - MS Idle State3 - System Access State4 - Traffic Channel State5,6,7 - various call service options
Processing StateReceive Power,
dbmTransmit Gain Adjust,
db
TransmitVocoder Rate
1 = 1/82 = 1/44 = 1/28 = Full
Frequency(channel #)
Walshcode
assigned
Receive Vocoder
Rate
Ec/Io, db(primary PN only)
February, 2005 7 - 157RF100 v2.0 (c) 2005 Scott Baxter
Entering Denso Debug Mode
Enter ##DEBUG (##33284)Scroll down to SAVEPress OKHighlight SERVICE SCREENPress OK
If you want to make a test call, dial the digits and press OK while in idle mode
CBV: 3957ABU: 3954 ABT: 031ARF: 0000 CCL: 01SID: 04157NID: 00001CH: 0100 RSSI: 093DPN: 084 TX:-46BFRM:0000000968TFRM:0000135712FER:% 000.71LT: 036:06:36LG: -086:45:36EC: -16 -63 -63PN: 084 084 084FNGLK: Y Y NWLSH: 01 01 01ACT: 084 484 096-01 -01 200CND: 220 332 200200 332 NGH: 076080 340 068 196O56 320 220 316344 488 196 200392 124 128 084224 008 084
D
February, 2005 7 - 158RF100 v2.0 (c) 2005 Scott Baxter
Denso Maintenance Display
CBV: 3957ABV: 3954 ABT: 031ARF: 0000 CCL: 01SID: 04157NID: 00001CH: 0100 RSSI: 093DPN: 084 TX:-46BFRM:0000000968TFRM:0000135712FER:% 000.71LT: 036:06:36LG: -086:45:36EC: -16 -63 -63PN: 084 084 084FNGLK: Y Y NWLSH: 01 01 01ACT: 084 484 096-01 -01 200CND: 220 332 200200 332 NGH: 076080 340 068 196O56 320 220 316344 488 196 200392 124 128 084224 008 084
DCharging Battery Voltage
Average Battery Voltage Average Battery Temperature
System IDNetwork ID
RF Channel FrequencyDigital PN Offset
Received Signal StrengthEstimated Transmitter
Power OutputNumber of Bad Frames
Number of Good Frames Frame Erasure Rate, PercentBase Station coordinates
Current status of Rake Fingers
Active Pilot Set
Candidate Pilot SetNeighbor Pilot Set
February, 2005 7 - 159RF100 v2.0 (c) 2005 Scott Baxter
Early Sanyo Dual-Band Phones
press menu 7, 0enter in DEBUGM (332846) screens are similar to QCP phones
7
0
48233 6
Press This:
Menu
318 2 94X A 7F
D
February, 2005 7 - 160RF100 v2.0 (c) 2005 Scott Baxter
Sanyo SPC-4500 Maintenance Display
Choose the following:DISPLAYOK0OKEnter Code: 0 0 0 0 0 0Debug MenuSCREENOK
February, 2005 7 - 161RF100 v2.0 (c) 2005 Scott Baxter
Sanyo SPC-4900 Maintenance Display
##040793select MENU/OK buttonscroll to save Phone #select
PN offset
Call Proc. StateReceivePower
Io
ChannelFrequency
February, 2005 7 - 162RF100 v2.0 (c) 2005 Scott Baxter
Entering Maintenance Mode: Motorola StarTacContact your service provider to obtain your phone’s Master
Subscriber entity Lock (MSL). Then enter the following:FCN 000000 000000 0 RCL You'll be prompted for your MSL, enter it and press STO.
• New prompts will appear, Press STO in response to each prompt until no more appear. Don’t delay -continue quickly and enter:
FCN 0 0 * * T E S T M O D E STO • The display will briefly show US then just '.
Press 55#.• Step 1 will appear with its current setting displayed.
Press * to accept and move on to the next step. Repeat for steps 2-8.
Step 9 (Option byte 2) is the only step requiring manual changes. Enter 1 0 0 0 0 0 0 0 (The leftmost bit now set to '1' is what enables test mode.)Now press STO to accept the entry and exit back to the ' prompt.Power off and back on.You should now be in test mode!
February, 2005 7 - 163RF100 v2.0 (c) 2005 Scott Baxter
February, 2005 7 - 164RF100 v2.0 (c) 2005 Scott Baxter
RX Power BatteryCondition
N5 N5M failureBS BS Ack failureWO L3 WFO State TimeoutMP Max Probe FailurePC Paging Channel lossRR Reorder or Release on PCH?? Unknown Condition
ChannelNumber
#Neighbors
Local Time#
ActivesStrongest Active
PN Ec/IoStrongest NeighborPN Ec/Io
# Cand-idates Call Proc
StateLast Call
Exit Reason# Drops
# CallsLast Call FER%
NIDSIDRx Powerdbm (Io)
Tx Powerdbm
CurrentService Option
Last Call IndicatorNI No Indication yetMR Mobile ReleaseBR Base Sta. ReleaseTC Traffic Channel LostL2 Layer 2 Ack FailNC No Channel Assn Msg
Current Service Option8V 8K voice originalIL 8K loopback8EV 8K EVRC8S 8K SMS13L 13K loopback
13S 13K SMS8MO 8K Markov OldDAT Data8M 8K Markov New13M 13K Markov New13V 13K Voice
Call Processing StatesCP CP ExitRST CP RestartRTC RestrictedPLT Pilot AcquisitionSYN Sync AcquisitionTIM Timing ChangeBKS Background SchIDL IdleOVD OverheadPAG Paging
ORG Call OriginationSMS Short Message SvcORD Order ResponseREG RegistrationTCI Tfc Ch InitializationWFO Waiting for OrderWFA Waiting for AnswerCON Conversation stateREL ReleaseNON No State
February, 2005 7 - 165RF100 v2.0 (c) 2005 Scott Baxter
Motorola V120C Series
MENU 073887* Enter 000000 for security code. Scroll down to Test Mode. Enter subscriber entity lock code if required by your phone
Same maintenance display as shown for Startac
February, 2005 7 - 166RF100 v2.0 (c) 2005 Scott Baxter
Motorola V60C
MENU 073887* Enter 000000 for security code. Scroll down to Test Mode. Enter subscriber entity lock code if required by your phone
Same maintenance display as shown for Startac
February, 2005 7 - 167RF100 v2.0 (c) 2005 Scott Baxter
Audiovox 8100, 9155
Press ##27732726 [End] Select the Debug screen.PN, channel#, SID, NID, mode (13K, EVRC, etc) Ec/Io, RX Level, TX Level.You cannot make a call while in any of the maintenance screens.
February, 2005 7 - 168RF100 v2.0 (c) 2005 Scott Baxter
NeoPoint Phones
Although NeoPoint went out of business in June, 2001, there are still some NeoPointhandsets in general usePress the M (menu) keySelect Preferences (using the up-arrow key)Enter 040793Choose Debug Screen [Select]Now you’re in maintenance mode!
February, 2005 7 - 169RF100 v2.0 (c) 2005 Scott Baxter
GoldStar TouchPoint
To enter maintenance mode, just key in: # # D E B U G SAVE
February, 2005 7 - 170RF100 v2.0 (c) 2005 Scott Baxter
Nokia 6185 Maintenance Display
Enter *3001#12345# MENUScroll down to Field testPress SelectScroll up to EnabledPress OKPower the phone off and onYou should now be in Field test mode
February, 2005 7 - 171RF100 v2.0 (c) 2005 Scott Baxter
Older Nokia Models Maintenance Display
Enter *3001#12345# MENUScroll down to Field testPress SelectScroll up to EnabledPress OKPower the phone off and onYou should now be in Field test mode and the following screens will be available:
February, 2005 7 - 172RF100 v2.0 (c) 2005 Scott Baxter
Maintenance Display Screens of Nokia Handsets
CSST
XXXXX
RSSICCCC
RXTX
CS StateIdle: PN Offset
TFC: #Actv, FERRSSI dBm
Paging Channel #RX power, dbmTX power, dbm
Screen 1: General
CSSTPGCH
CURSOFER
CS StatePaging Channel #
Current Service OptionFrame Error Rate
Screen 2: Paging CH Info
Mobile MINMobile Station ESN
Preferred Sys 1=AMPS, 2=CDMA
OwnNumberESN
P
A Operator Selected(1=A, 2=B, 3=both
Screen 4: NAM Info
Primary Channel ASecondary Channel A
PPCASPCA
Screen 5: NAM Info
Primary Channel BSecondary Channel B
PPCBSPCB
Local UseAccess Overload Class
LA
Current SIDCurrent NID
SIDNID
Screen 6: BS & Access. Info.
DBUS (Handsfree?)DBUS
BASE_ID (sys par msg)P_REV (sync msg)
BASE#P_REV
Screen 7: BS Protocol Rev. Level
MIN_P_REV (sync msg.MIN_P_REV
CS StateDate from System Time
CSSTMMDDYY
Screen 8: Time Information
System TimeHHMMSS
The following screens appear in field test mode on Nokia HD881 series of Handsets:
February, 2005 7 - 173RF100 v2.0 (c) 2005 Scott Baxter
Nokia Maintenance Display Screens (continued)
TADDTDROP
TATD
Screen 9: Acquisition Information
TCOMPTCTTDROPTT
Active WindowWW1Neighbor WindowWW2
Remaining WindowWW3
Pilot PN OffsetEc/Io in 1/2 db units
PPNEC
Screen 10: Active Set (#1-3)
Keep? 1KPilot PN Offset
Ec/Io in 1/2 db unitsPPNEC
Keep? 1KPilot PN Offset
Ec/Io in 1/2 db unitsPPNEC
Keep? 1K
Pilot PN OffsetEc/Io in 1/2 db units
PPNEC
Screen 11: Active Set (#4-6)
Keep? 1KPilot PN Offset
Ec/Io in 1/2 db unitsPPNEC
Keep? 1KPilot PN Offset
Ec/Io in 1/2 db unitsPPNEC
Keep? 1K
February, 2005 7 - 174RF100 v2.0 (c) 2005 Scott Baxter
Nokia Maintenance Display Screens (continued)
NBR 1 PN OffsetEc/Io in 1/2 db units
PPNEC
Screen 12: Neighbor Set (#1-5)
NBR 2 PN OffsetEc/Io in 1/2 db units
PPNEC
NBR 3 PN OffsetEc/Io in 1/2 db units
PPNEC
NBR 4 PN OffsetEc/Io in 1/2 db units
PPNEC
NBR 5 PN OffsetEc/Io in 1/2 db units
PPNEC
NBR 6 PN OffsetEc/Io in 1/2 db units
PPNEC
Screen 13: Neighbor Set (#6-10)
NBR 7 PN OffsetEc/Io in 1/2 db units
PPNEC
NBR 8 PN OffsetEc/Io in 1/2 db units
PPNEC
NBR 9 PN OffsetEc/Io in 1/2 db units
PPNEC
NBR 10 PN OffsetEc/Io in 1/2 db units
PPNEC
NBR 11 PN OffsetEc/Io in 1/2 db units
PPNEC
Screen 14: Neighbor Set (#11-15)
NBR 12 PN OffsetEc/Io in 1/2 db units
PPNEC
NBR 13 PN OffsetEc/Io in 1/2 db units
PPNEC
NBR 14 PN OffsetEc/Io in 1/2 db units
PPNEC
NBR 15 PN OffsetEc/Io in 1/2 db units
PPNEC
NBR 16 PN OffsetEc/Io in 1/2 db units
PPNEC
Screen 15: Neighbor Set (#16-20)
NBR 17 PN OffsetEc/Io in 1/2 db units
PPNEC
NBR 18 PN OffsetEc/Io in 1/2 db units
PPNEC
NBR 19 PN OffsetEc/Io in 1/2 db units
PPNEC
NBR 20 PN OffsetEc/Io in 1/2 db units
PPNEC
February, 2005 7 - 175RF100 v2.0 (c) 2005 Scott Baxter
Nokia Maintenance Display Screens (continued)
CAND 1 PN OffsetEc/Io in 1/2 db units
PPNEC
Screen 16: Candidate Set (#1-5)
CAND 2 PN OffsetEc/Io in 1/2 db units
PPNEC
CAND 3 PN OffsetEc/Io in 1/2 db units
PPNEC
CAND 4 PN OffsetEc/Io in 1/2 db units
PPNEC
CAND 5 PN OffsetEc/Io in 1/2 db units
PPNEC
Task NameWorst-Cs Stack Free Sp
TASKNFREE
Screen 17-22: Task Stack Ck Info
Overflow ind. by shift2=sys stack overflow
Task StackSys Stack
Screen 23: Stack Status Info.
Screen 24: Codec Registers
February, 2005 7 - 176RF100 v2.0 (c) 2005 Scott Baxter
Novatel Merlin C201 Card
Enter # # D E B U G to enter maintenance mode.To exit, just click “OK” box in the Debug window.
February, 2005 7 - 177RF100 v2.0 (c) 2005 Scott Baxter
Audiovox Thera Maintenance Mode Screens
How to enterDebug Mode:
[ctrl] [D] [enter]
Advanced Usr Pwd:##DEBUG [enter]
Protocol Statistics
February, 2005 7 - 178RF100 v2.0 (c) 2005 Scott Baxter
What’s New in CDMA2000?What’s New in CDMA2000?
The Future is Here! CDMA2000
February, 2005 7 - 179RF100 v2.0 (c) 2005 Scott Baxter
What’s New in CDMA2000?
CDMA2000 is the next-generation family of CDMA standardsCDMA2000 Phase I: 1xRTT
Independent I and Q modulation almost doubles capacity, compared to old IS-95 modulation with I and Q duplicationNew types of channels are provided
• “fundamental” channels like IS-95 traffic channels, but better coded so they require less air-interface capacity; circuit-switched
• new “supplemental” channels can carry fast data (153K, 230K, even 307Kbps); assigned for packet bursts, not continuously
• also optional new administrative channels for smoother operations• a sector can carry a dynamic “mix” of both new channel types, as well
as old IS-95 traffic channels simultaneously!CDMA2000 Phase II: 1xEV DO, 1xEV DV, and 3xRTT
3xRTT: Faster data on a bundle of 3 1x carriers; probably won’t be used1xEV DO: 1x Evolution, Data Only (IS-856) Qualcomm & Lucent
• Fast data up to 2.4 Mbps on a dedicated 1.2 MHz. CDMA Carrier1xEV DV: 1x Evolution, Data and Voice “1Xtreme” Motorola & Nokia
• Fast data up to 5 Mbps on a 1.2 MHz. carrier still supporting a mix of fast data and voice traffic
February, 2005 7 - 180RF100 v2.0 (c) 2005 Scott Baxter
The CDMA Migration Path to 3G
1xEV-DORev. A
IS-856
1250 kHz.59 active
users
Higher data rates on data-
only CDMA carrier
3.1 Mb/sDL
1.8 Mb/sUL
RL FLSpectrum
1xEV-DORev. 0IS-856
1250 kHz.59 active
users
High data rates on data-only
CDMA carrier
2.4 Mb/sDL
153 Kb/sUL
CDMAone CDMA2000 / IS-2000
Technology
Generation
SignalBandwidth,
#Users
Features:Incremental
Progress
1G
AMPS
DataCapabilities
30 kHz.1
First System,Capacity
&Handoffs
None,2.4K by modem
2G
IS-95A/J-Std008
1250 kHz.20-35
First CDMA,
Capacity,Quality
14.4K
2G
IS-95B
1250 kHz.25-40
•Improved Access•Smarter Handoffs
64K
2.5G? 3G
IS-2000:1xRTT
1250 kHz.50-80 voice
and data
•Enhanced Access
•Channel Structure
153K307K230K
3G
1xEV-DV1xTreme
1250 kHz.Many packet
users
High data rates on
Data-Voice shared CDMA carrier
5 Mb/s
3G
IS-2000:3xRTT
F: 3x 1250kR: 3687k
120-210 per 3 carriers
Faster data rates on shared 3-carrier bundle
1.0 Mb/s
RL FLRL FLRL FLRL FLRL FLRL FLRL FL
February, 2005 7 - 181RF100 v2.0 (c) 2005 Scott Baxter
Modulation Techniques of 1xEV Technologies
1xEV, “1x Evolution”, is a family of alternative fast-data schemes that can be implemented on a 1x CDMA carrier.1xEV DO means “1x Evolution, Data Only”, originally proposed by Qualcomm as “High Data Rates” (HDR).
• Up to 2.4576 Mbps forward, 153.6 kbps reverse
• A 1xEV DO carrier holds only packet data, and does not support circuit-switched voice
• Commercially available in 20031xEV DV means “1x Evolution, Data and Voice”.
• Max throughput of 5 Mbps forward, 307.2k reverse
• Backward compatible with IS-95/1xRTT voice calls on the same carrier as the data
• Not yet commercially available; work continues
All versions of 1xEV use advanced modulation techniques to achieve high throughputs.
QPSKCDMA IS-95,
IS-2000 1xRTT,and lower ratesof 1xEV-DO, DV
16QAM1xEV-DOat highest
rates
64QAM1xEV-DVat highest
rates
February, 2005 7 - 182RF100 v2.0 (c) 2005 Scott Baxter
Channel Structure of 1xEV-DO vs. 1xRTTCHANNEL STRUCTURE
IS-95 and 1xRTT• many simultaneous users, each
with steady forward and reverse traffic channels
• transmissions arranged, requested, confirmed by layer-3 messages – with some delay……
1xEV-DO -- Very Different:• Forward Link goes to one user at a
time – like TDMA!• users are rapidly time-multiplexed,
each receives fair share of available sector time
• instant preference given to user with ideal receiving conditions, to maximize average throughput
• transmissions arranged and requested via steady MAC-layer walsh streams – very immediate!
BTS
IS-95 AND 1xRTTMany users’ simultaneous forward
and reverse traffic channelsW0W32W1W17W25W41
W3
W53
PILOTSYNC
PAGINGF-FCH1F-FCH2F-FCH3
F-SCH
F-FCH4
AP
1xEV-DO AP (Access Point)
ATs (Access Terminals)
1xEV-DO Forward Link
February, 2005 7 - 183RF100 v2.0 (c) 2005 Scott Baxter
Power Management of 1xEV-DO vs. 1xRTT
POWER MANAGEMENTIS-95 and 1xRTT:
• sectors adjust each user’s channel power to maintain a preset target FER
1xEV-DO IS-856:• sectors always operate at
maximum power• sector output is time-
multiplexed, with only one user served at any instant
• The transmission data rate is set to the maximum speed the user can receive at that moment
PILOT
PAGINGSYNC
Maximum Sector Transmit Power
User 123
45 5 5678
time
pow
er
IS-95: VARIABLE POWER TO MAINTAIN USER FER
time
pow
er
1xEV-DO: MAX POWER ALWAYS,DATA RATE OPTIMIZED
February, 2005 7 - 184RF100 v2.0 (c) 2005 Scott Baxter
CDMA Network for Circuit-Switched Voice Calls
The first commercial IS-95 CDMA systems provided only circuit-switched voice calls
t1t1 v CESEL
t1PSTN
BTS
(C)BSC/Access ManagerSwitch
February, 2005 7 - 185RF100 v2.0 (c) 2005 Scott Baxter
CDMA 1xRTT Voice and Data Network
CDMA2000 1xRTT networks added two new capabilities:• channel elements able to generate and carry independent streams of
symbols on the I and Q channels of the QPSK RF signal– this roughly doubles capacity compared to IS-95
• a separate IP network implementing packet connections from the mobile through to the outside internet
– including Packet Data Serving Nodes (PDSNs) and a dedicated direct data connection (the Packet-Radio Interface) to the heart of the BSC
The overall connection speed was still limited by the 1xRTT air interface
t1t1 v CESEL
t1
PDSNForeign Agent
PDSNHome Agent
BackboneNetworkInternet
VPNs
PSTN
AuthenticationAuthorization
AccountingAAA
BTS
(C)BSC/Access ManagerSwitch
February, 2005 7 - 186RF100 v2.0 (c) 2005 Scott Baxter
1xEV-DO Overlaid On Existing 1xRTT Network
1xEV-DO requires faster resource management than 1x BSCs can give• this is provided by the new Data Only Radio Network Controller (DO-RNC)
A new controller and packet controller software are needed in the BTS to manage the radio resources for EV sessions
• in some cases dedicated channel elements and even dedicated backhaul is used for the EV-DO traffic
The new DO-OMC administers the DO-RNC and BTS PCF additionExisting PDSNs and backbone network are used with minor upgradingThe following sections show Lucent, Motorola, and Nortel’s specific solutions
t1t1 v CESEL
t1
PDSNForeign Agent
PDSNHome Agent
BackboneNetworkInternet
VPNs
PSTN
AuthenticationAuthorization
AccountingAAA
BTS
(C)BSC/Access ManagerSwitch CE
DORadio
NetworkController
DO-OMC
February, 2005 7 - 187RF100 v2.0 (c) 2005 Scott Baxter
3G Information ResourcesBibliography - Articles - Web Links
3G Information ResourcesBibliography - Articles - Web Links
February, 2005 7 - 188RF100 v2.0 (c) 2005 Scott Baxter
Bibliography, 3G Air Interface Technologies“3G Wireless Demystified” by Lawrence Harte, Richard Levine, and Roman Kitka488pp. Paperback, 2001 McGraw Hill, ISSBN 0-07-136301-7 $50. For both non-technical and
technical readers. An excellent starting point for understanding all the major technologies and the whole 3G movement. Comfortable plain-language explanations of all the 2G and 3G air interfaces, yet including very succinct, complete, and rigorously correct technical details. You will still want to read books at a deeper technical level in your chosen technology, and may sometimes turn to the applicable standards for finer details, but this book will give you what you won’t find elsewhere -- how everything relates in the big picture, and probably everything you care to know about technologies other than your own.
"Wireless Network Evolution 2G to 3G" by Vijay K. Garg. 764pp. 2002 Prentice-Hall, Inc. ISBN 0-13-028077-1. $80. Excellent technical tutorial and reference. The most complete and comprehensive technical detail seen in a single text on all these technologies: IS-95 2G CDMA, CDMA2000 3G CDMA, UMTS/WCDMA, Bluetooth, WLAN standards (802.11a, b, WILAN). Includes good foundation information on CDMA air interface traffic capacity, CDMA system design and optimization, and wireless IP operations. Excellent level of operational detail for IS-95 systems operating today as well as thorough explanations of 2.5G and 3G enhancements.
"3G Wireless Networks" by Clint Smith and Daniel Collins. 622pp. Paperback. 2002 McGraw-Hill, ISBN 0-07-136381-5. $60. An excellent overview of all 3G technologies coupled with good detail of network architectures, channel structures, and general operational details. Good treatment of both CDMA2000 and UMTS/WCDMA systems.
“WCDMA: Towards IP Mobility and Mobile Internet” by Tero Ojanpera and Ramjee Prasad. 476pp. 2001 Artech House, ISSBN 1-58053-180-6. $100. The most complete and definitive work on UMTS (excellent CDMA2000, too!). CDMA principles, Mobile Internet, RF Environment & Design, Air Interface, WCDMA FDD standard, WCDMA TDD, CDMA2000, Performance, Heirarchical Cell Structures, Implementation, Network Planning, Basic IP Principles, Network Architectures, Standardization, Future Directions. This is a MUST HAVE for a one-book library!
February, 2005 7 - 189RF100 v2.0 (c) 2005 Scott Baxter
More Bibliography, 3G Air Interface Technologies
“The UMTS Network and Radio Access Technology” by Dr. Jonathan P. Castro, 354 pp. 2001 John Wiley, ISBN 0 471 81375 3, $120. An excellent, well-organized, and understandable exploration of UMTS. Includes radio interface, channel explanations, link budgets, network architecture, service types, ip network considerations, a masterful tour de force through the entire subject area. Very readable, too!
“WCDMA for UMTS” by Harri Holma and Antti Toskala, 322 pp. 2000 Wiley, ISBN 0 471 72051 8, $60. Very good overall treatment of UMTS. Excellent introduction to 3G and summary of standardization activities, every level of UMTS/UTRA. Good overview of CDMA-2000, too!
“The GSM Network - GPRS Evolution: One Step Towards UMTS” 2nd Edition by Joachim Tisal, 227pp. paperback, 2001 Wiley, ISBN 0 471 49816 5, $60. Readable but not overwhelming introduction to GSM in all its aspects (140pp), DECT (11pp), GPRS (6pp), UMTS (7pp), WAP (25pp), EDGE (10pp).
February, 2005 7 - 190RF100 v2.0 (c) 2005 Scott Baxter
Bibliography, The IP Aspect of 3G“Mobile IP: Design, Principles and Practices” by Charles E. Perkins, 275 pp., 200, 1998 Addison-
Wesley, ISBN 0-201-63469-4. $60. Comprehensive view of Mobile IP including home and foreign agents, advertisement, discovery, registration, datagrams, tunneling, encapsulation, route optimization, handoffs, firewalls, IPv6, DHCP. Tour-de-force of mobile IP techniques.
“Mobile IP Technology for M-Business” by Mark Norris, 291 pp., 2001 Artech House, ISSBN 1-58053-301-9. $67. GPRS overview and background, Mobile IP, Addressing, Routing, M-business, future prospects, IPv4, IPv6, Bluetooth & IrDA summaries.
“TCP/IP Explained” by Phillip Miller, 1997 Digital Press, ISBN 1-55558-166-8, 518pp. $50. In-depth understanding of the Internet protocol suite, network access and link layers, addressing, subnetting, name/address resolution, routing, error reporting/recovery, network management. IF you’re not already strong in TCP/IP, you’ll need this to fully master Mobile IP.
“Cisco Networking Academy Program: First-Year Companion Guide” edited by Vito Amato, 1999 Cisco Press, ISBN 1-57870-126-0, 438pp. Textbook supporting a year-long course on networking technologies for aspiring LAN/WAN (and 3G) technicians and engineers. It covers every popular networking technology (including all its elements and devices) in deep and practical detail. Excellent real-world understanding of TCP/IP, as well as the nuts-and-bolts of everything from physical components to protocols to actual devices such as routers, switches, etc. You might even want to take the evening courses at a local community college near you.
“Cisco Networking Academy Program: Engineering Journal and Workbook, Volume I” edited by Vito Amato, 1999 Cisco Press, ISBN 1-57870-126-x, 291pp. The workbook for the First Year Companion Guide above. If you want some external structure in your self-study, this workbook will hold your hand as you climb every step of the ladder, and will lead you step by step through the sister textbook, ensuring you absorb everything you need to know.
February, 2005 7 - 191RF100 v2.0 (c) 2005 Scott Baxter
Bibliography - General CDMA“IS-95 CDMA and CDMA2000: Cellular/PCS Systems Implementation” by Vijay K. Garg. 422 pp.
2000 Prentice Hall, ISBN 0-13-087112-5, $90. IS-95 and CDMA2000 Access technologies, DSSS, IS-95 air interface, channels, call processing, power control, signaling, soft handoff, netw. planning, capacity, data. CDMA2000 layers, channels, coding, comparison w/ WCDMA.
“CDMA Systems Engineering Handbook” by Jhong Sam Lee and Leonard E. Miller, 1998 ArtechHouse, ISBN 0-89006-990-5. Excellent treatment of CDMA basics and deeper theory, cell and system design principles, system performance optimization, capacity issues. Recommended.
“CDMA RF System Engineering” by Samuel C. Yang, 1998 Artech House, ISBN 0-89006-991-3. Good general treatment of CDMA capacity considerations from mathematical viewpoint.
“CDMA Internetworking: Deploying the Open A-Interface” by Low and Schneider. 616 pp. 2000 Prentice Hall, ISBN 0-13-088922-9, $75. A tour-de-force exposition of the networking between the CDMA BSC, BTS, and mobile, including messaging and protocols of IS-634. Chapters on SS7, Call Processing, Mobility Management, Supplementary Services, Authentication, Resource Management (both radio and terrestrial), 3G A-Interface details. One-of-a-kind work!
"CDMA: Principles of Spread Spectrum Communication" by Andrew J. Viterbi. 245 p. Addison-Wesley 1995. ISBN 0-201-63374-4, $65. Very deep CDMA Theory. Prestige collector’s item.
February, 2005 7 - 192RF100 v2.0 (c) 2005 Scott Baxter
Bibliography - General Wireless
“Mobile and Personal Communication Services and Systems” by Raj Pandya, 334 pp. 2000 IEEE Press, $60. IEEE order #PC5395, ISBN 0-7803-4708-0. Good technical overview of AMPS, TACS< NMT, NTT, GSM, IS-136, PDC, IS-95, CT2, DECT, PACS, PHS, mobile data, wireless LANs, mobile IP, WATM, IMT2000 initiatives by region, global mobile satellite systems, UPT, numbers and identities, performance benchmarks.
“Wireless Telecom FAQs” by Clint Smith, 2001 McGraw Hill, ISBN 0-07-134102-1. Succint, lucid explanations of telecom terms in both wireless and landline technologies. Includes cellular architecture, AMPS, GSM, TDMA, iDEN, CDMA. Very thorough coverage; an excellent reference for new technical people or anyone wishing for clear explanations of wireless terms.
"Mobile Communications Engineering" 2nd. Edition by William C. Y. Lee. 689 pp. McGraw Hill 1998 $65. ISBN 0-07-037103-2 Lee’s latest/greatest reference work on all of wireless; well done.
February, 2005 7 - 193RF100 v2.0 (c) 2005 Scott Baxter
Web Links and Downloadable Resources
Scott Baxter: http://www.howcdmaworks.comLatest versions of all courses are downloadable. Category - Username - PasswordIntro - (none required) - (none required)RF/CDMA/Performance - shannon - hertz3G - generation - thirdGrayson - telecom - allenAgilent - nitro - viper
Dr. Ernest Simo’s Space2000: http://www.cdmaonline.com/ and http://www.3Gonline.com/
CDG: http://www.cdg.org (check out the digivents multimedia viewable sessions)The IS-95 and IS-2000 CDMA trade marketing webside, CDMA cheerleaders.
GSM: http://www.gsmworld.comThe GSM Association website. Worldwide GSM marketing cheerleaders but also includes some excellent GSM and GPRS technical overview whitepapers and documents; latest user figures.
UWCC: http://www.uwcc.comThe IS-136 TDMA trade marketing website, TDMA cheerleaders.
RCR News: http://www.rcrnews.comWireless Industry trade publication - regulatory, technical, business, marketing news.Subscribers can access text archives of past articles; very handy in researching events.
Wireless Week: http://www.wirelessweek.comWireless Industry trade publication - regulatory, technical, business, marketing news.
February, 2005 7 - 194RF100 v2.0 (c) 2005 Scott Baxter
More Web Links
3GPP: http://www.3gpp.org/The operators’ harmonization group concerned mainly with ETSI-related standards
3GPP2: http://www.3gpp2.org/The operators’ harmonization group concerned mainly with IS-95-derived CDMA standards
ITU: http://www.itu.int/imt/
ETSI: http://www.etsi.fr/
UMTS forum: http://www.umts-forum.org/
GSM MoU: http://www.gsmworld.com/
TIA: http://www.tiaonline.org/
T1: http://www.t1.org/
ARIB: http://www.arib.or.jp/arib/english/index.html
TTC: http://www.ttc.or.jp/
TTA: http://www.tta.or.kr/
ETRI: http://www.etri.re.kr/
RAST: http://www.rast.etsi.fi/
February, 2005 Supplement - 1RF100 v2.0 (c) 2005 Scott Baxter
Course RF100 SupplementCourse RF100 Supplement
February, 2005 Supplement - 2RF100 v2.0 (c) 2005 Scott Baxter
Supplemental Topics
Link BudgetsHard Handoff StrategiesReradiatorsSome Operational Measurements and Capacity Considerations3G Systems
February, 2005 Supplement - 3RF100 v2.0 (c) 2005 Scott Baxter
Section A
Link BudgetsLink Budgets
February, 2005 Supplement - 4RF100 v2.0 (c) 2005 Scott Baxter
Link Budget Example: Usage Model and Service Assumptions
This section outlines the number of subscribers and amount of traffic by yearThis section shows the variability of outdoor and indoor signals, and the building penetration loss
Interactive Initial System Design Example v1.2fill in GREEN fieldsYELLOW fields calculate automatically
Step 1. Basic Business Plan Details
Year Launch 1 2 3 4 5Population 3,886,000 3,949,350 4,012,700 4,076,050 4,139,400 4,202,750Penetration, % 0.05% 1.85% 3.72% 5.64% 7.60% 9.57%#Customers 1,781 72,933 149,453 229,941 314,451 402,360BH Erl/Cust 0.1 0.05 0.045 0.05 0.05 0.05Total BH erl 178.1 3,646.7 6,725.4 11,497.0 15,722.6 20,118.0
2. Enter building penetration loss and standard deviations from measurements.
Composite Probability Of Service & Required Fade MarginEnvironment
Type ("morphology")
Building Median
Loss, dB
Building Std. Dev,
dB
Outdoor Std. Dev,
dB.
Composite Standard Deviation
Desired Reliability at Cell Edge, %
Fade Margin,
dB.Dense Urban 20 8 8 11.31 75.0% 7.63Urban 15 8 8 11.31 75.0% 7.63Suburban 15 8 8 11.31 75.0% 7.63Rural 10 8 8 11.31 75.0% 7.63Highway 8 6 8 10.00 75.0% 6.74
February, 2005 Supplement - 5RF100 v2.0 (c) 2005 Scott Baxter
Reverse Link Budget Example
The Reverse Link Budget describes how the energy from the phone is distributed to the base station, including the major components of loss and gain within the system
3. Construct Link Budgets
Reverse Link Budget
Term or Factor GivenDense Urb. Urban Suburban Rural Highway Formula
MS TX Power (dbm) (+) 23MS antenna gain and body loss (+/-) 0MS EIRP (dBm) (+) 23.00 23.00 23.00 23.00 23.00 AFade Margin, (dB) (-) -7.63 -7.63 -7.63 -7.63 -6.74 BSoft Handoff Gain (dB) (+) 4 4 4 4 4 CReceiver Interf. Margin (dB) (-) -3 -3 -3 -3 -3 DBuilding Penetration Loss (dB) (-) -20.00 -15.00 -15.00 -10.00 -8.00 EBTS RX antenna gain (dBi) (+) 17 17 17 17 17 FBTS cable loss (dB) (-) -3 -3 -3 -3 -3 G
kTB (dBm/14.4 KHz.) -132.4 HBTS noise figure (dB) 6.5 I
Eb/Nt (dB) 5.9 JBTS RX sensitivity (dBm) (-) -120.0 -120.0 -120.0 -120.0 -120.0 H+I+J
Survivable Uplink Path Loss (dB) (+) 130.4 135.4 135.4 140.4 143.3
A+B+C+D+E+F+G-(H+I+J)
February, 2005 Supplement - 6RF100 v2.0 (c) 2005 Scott Baxter
Forward Link Budget Example
This section shows the forward link power distribution, and compares the relative balance of the forward and reverse links
Forward Link Budget
Term or Factor GivenDense Urb. Urban Suburban Rural Highway Formula
BTS TX power (dBm) (+) 45 45 45 45 45BTS TX power (watts) 31.62 31.62 31.62 31.62 31.62% Power for traffic channels 74.0% 74.0% 74.0% 74.0% 74.0%Number of Traffic Channels in use 19 19 19 19 19BTS cable loss (dB) (-) -3 -3 -3 -3 -3BTS TX antenna gain (dBi) (+) 17 17 17 17 17BTS EIRP/traffic channel (dBm) (+,-) 44.9 44.9 44.9 44.9 44.9 AFade margin (dB) (-) -7.63 -7.63 -7.63 -7.63 -6.74 BReceiver interference margin (db) (-) -3 -3 -3 -3 -3 CBuilding Penetration Loss (dB) (-) -20.0 -15.0 -15.0 -10.0 -8.0 DMS antenna gain & body loss (dB) (+,-) 0 0 0 0 0 E
kTB (dBm/14.4 KHz.) -132.4Subscriber RX noise figure (dB) 10.5
Eb/Nt (dB) 6Subscriber RX sensitivity (dBm) (-) -115.9 -115.9 -115.9 -115.9 -115.9 F
Survivable Downlink Path Loss, dB (+) 130.2 135.2 135.2 140.2 143.1A+B+C+D
+E-F
Forward/Reverse Link Balance DenseUrban Urban Suburban Rural Highway
Which link is dominant? Reverse Reverse Reverse Reverse ReverseWhat advantage, dB? 0.2 0.2 0.2 0.2 0.2
February, 2005 Supplement - 7RF100 v2.0 (c) 2005 Scott Baxter
Link Budgets: What is the Radius of a Cell?
This section uses the Okumura-Hata/Cost-231 model to describe the frequency, antenna heights, and environmental factors, and their relationship on the cell’s coverage distance
4. Explore propagation model to figure coverage radius of cell.
Frequency, MHz. 870Subscriber Antenna Height, M 1.5
DenseUrban Urban Suburban Rural Highway
Base Station Antenna Height, M 20 20 30 50 50
DenseUrban Urban Suburban Rural Highway
Environmental Correction, dB -2 -5 -10 -17 -17Coverage Radius, kM 1.30 2.17 6.87 20.86 25.40
Coverage Radius, Miles 0.81 1.35 4.27 12.96 15.78
February, 2005 Supplement - 8RF100 v2.0 (c) 2005 Scott Baxter
Link Budgets: Putting It All Together
Step 4 estimates the number of cells required to serve each distinct environment within the systemSteps 5, 6, and 7 estimate the RF coverage from each cell, and the number of cells required
5. Calculate number of cells required for coverage, ignoring traffic considerations.
Dense TotalUrban Urban Suburban Rural Highway # Cells
Covered Area of this type, kM 2 55 450 1700 3400 1400 RequiredOne cell's coverage in this zone, kM 2 5.35 14.73 148.46 1367.34 2026.72 for System
# Cells required to cover zone 10.3 30.6 11.5 2.5 0.7 55.5
6. What is the traffic capacity (in erlangs) of your chosen BTS configuration, year-by-year?
Year Launch 1 2 3 4 5Erlangs which one BTS can carry 18.3 18.3 90 90 450 450
7, 8. What is the total busy-hour erlang traffic on your system? How many BTS are required?
Year Launch 1 2 3 4 5Total System Busy-Hour Erlangs 178.1 3,646.7 6,725.4 11,497.0 15,722.6 20,118.0
Capacity of One BTS, erlangs 18.3 18.3 90 90 450 450# BTS required to handle all the traffic 9.7 199.3 74.7 127.7 34.9 44.7
9. Examine your market, #BTS required for coverage and capacity; estimate totalnumber of BTS required.
Year Launch 1 2 3 4 5#BTS req'd just to achieve coverage 55.5 55.5 55.5 55.5 55.5 55.5
#BTS required just to carry traffic 9.7 199.3 74.7 127.7 34.9 44.7
Estimated total #BTS required 56.3 206.8 206.8 206.8 206.8 206.8
February, 2005 Supplement - 9RF100 v2.0 (c) 2005 Scott Baxter
Section B
Hard Handoff StrategiesHard Handoff Strategies
February, 2005 Supplement - 10RF100 v2.0 (c) 2005 Scott Baxter
Co-Channel CDMA Intersystem Handoff IssuesCochannel Hard Handoff Border Interference Problems
Consider two adjacent CDMA systems:• Same frequency• Not yet equipped for intersystem soft handoff, so only hard handoff is
possible between them; “dragged” handoffs become a big problemHandoff Performance Results:
• Mobiles CAN see pilots from adjoining system, so mobile-directed handoff is possible
• However, the handoff will be hard and mobiles can use only one system or the other, not both
• “dragging” mobiles cause severe interference in border cells• capacity, access failures, dropped calls, all will be poor in border area
BSC1 SW1
SW2 BSC2
Frequency 1
DallasFort Worth
Interference
February, 2005 Supplement - 11RF100 v2.0 (c) 2005 Scott Baxter
Use Intersystem Soft Handoff:Avoid Border Area Interference Problems
Consider two adjacent CDMA systems:• Same frequency• ATM connection between BSCs allows soft handoff
Handoff Performance Results:• Mobiles CAN see pilots from adjoining system, so mobile-directed
handoff is possible• Intersystem soft handoff is possible, so simultaneous power control is
possible for mobiles in border area• Border RF environment is the same as internal RF environment, no
special problems
BSC1 SW1
SW2 BSC2
Frequency 1
DallasFort Worth
Intersystem Soft HandoffATM link
no problems
February, 2005 Supplement - 12RF100 v2.0 (c) 2005 Scott Baxter
Avoid Interference, Use Different Frequencies?Hard Handoff Logistical Problems
Consider two adjacent CDMA systems:• Suppose intersystem soft handoff is not available• Systems are deliberately on different frequencies. This definitely
avoids interference in the border area, but causes other complicationsHandoff Logistical Problems:
• Mobiles on one system can’t see the pilots of adjoining cells on the other system! So, the mobiles will never request trans-border handoff
• Some method must be employed to force unsuspecting mobiles into transborder handoffs
• Common solutions: 1) implement intersystem soft handoff, 2) Pilot beacon cells, 3) auxiliary trigger mechanisms (Ec/Io, RTD, etc.)
Frequency 1
Frequency 2
BSC1 SW1
SW2 BSC2Dallas
Fort Worth
F2 Mobiles can’t see F1 pilots!
F1 Mobiles can’t see F2 pilots!
February, 2005 Supplement - 13RF100 v2.0 (c) 2005 Scott Baxter
One Solution to the Multi-Frequency Problem2-Frequency Trigger Method: Beacon Cells
The Beacon Solution• A pilot beacon cell is a “mannequin” -- a signal which can be seen by
arriving mobiles from the other system on their own frequency, inducing them to request handoff as soon as it is appropriate
• When mobiles request soft handoff with the beacon, the old system steps in and instructs the mobiles to do intersystem hard handoff to the real cell which the mobiles are approaching on the other system
Special Logistical Concerns with Beacons• Of course, it’s possible for mobiles of one system to “wake up” looking
at the pilot of a beacon cell in the border area, rather than a real cell.• Therefore, a beacon cell must transmit not only its pilot, but also a
sync channel and a paging channel with global service redirection
Frequency 1
Frequency 2
BSC1 SW1
SW2 BSC2Dallas
Fort Worth
F2 Mobiles can see F2 beacon
F1 Mobiles can see F1 beacon
February, 2005 Supplement - 14RF100 v2.0 (c) 2005 Scott Baxter
Another Solution for Multi-Frequency HandoffsBridge Cells, RTD Trigger in Boundary Sectors
All along the intersystem border, a one-cell-thick “transition zone” is created. The “bridge” cells in this zone are equipped with dual equipment, one set operating on each system.
• The outlooking sector of each bridge cell is tagged in the site database as a “boundary sector”. Whenever a mobile is served exclusively by a boundary sector, the system continuously monitors that mobile’s round trip delay (RTD).
• When the mobile’s RTD passes upward through a datafilled threshold, the system steps in and orders a hard handoff to the matching sector of the bridge cell on the other system
– this ensures the handoffs happen in clean environments with highprobability of success
– disadvantage: more BTS hardware needed than otherwise
Frequency 1
Frequency 2
BSC1 SW1
SW2 BSC2
DallasFort WorthBoundary Sector
Boundary Sector
February, 2005 Supplement - 15RF100 v2.0 (c) 2005 Scott Baxter
Another Solution for Multi-Frequency HandoffsArbitrary Ec/Io Trigger Mechanisms
Outlooking sectors of border cells are tagged as “boundary sectors” in the system database
• Whenever a mobile is served exclusively by a boundary sector, the system frequently interrogates the mobile with pilot measurementrequest messages
• When the mobile’s reports the boundary sector’s Ec/Io is below a preset threshold, the system immediately commands a hard handoffto a previously defined sector on the other system. Everyone hopes (prays?) that sector is able to hear the mobile for a successful handoff.
– The Ec/Io trigger threshold is sometimes a fixed value (usually 11 db above the T_Drop in the serving sector, although some networks’ later software allows an arbitrary trigger level to be set
Frequency 1
Frequency 2
BSC1 SW1
SW2 BSC2
DallasFort WorthBoundary Sector
Boundary Sector
February, 2005 Supplement - 16RF100 v2.0 (c) 2005 Scott Baxter
CDMA/AMPS Overlay Systems: Handdown
CDMA mobiles approaching the edge of CDMA coverage must hand down to AMPS
• however, CDMA mobiles cannot see AMPS signals during CDMA calls, and therefore will not request handoff
Methods for triggering CDMA-to-AMPS Handdown: the same ones we considered for CDMA-CDMA intersystem handoff
• beacon cells• bridge cells with RTD trigger• arbitrary Ec/Io thresholds on boundary sectors
Once a CDMA phone hands down to analog, it cannot be handed back up during the same call (due to long CDMA acquisition time)
CDMA Overlay
AMPS Existing System
February, 2005 Supplement - 17RF100 v2.0 (c) 2005 Scott Baxter
CDMA/AMPS Overlays: CDMA Acquisition
System acquisition is primarily controlled by the mobile• dual-mode mobiles look for CDMA first, then AMPS if needed
Distant mobiles may find unreliable CDMA signals beyond the edge of CDMA coverage, originate calls likely to drop
• most systems transmit Global Service Redirection Messages on all out-looking sectors to immediately force any distant mobiles to reacquire on AMPS
– hence no CDMA originations on outermost CDMA sectors!– However, still possible to soft-handoff into outer sectors
Many operators request handset manufacturers to add feature of periodic rechecking by idle handsets seeking to acquire CDMA
CDMA Overlay
AMPS Existing System
February, 2005 Supplement - 18RF100 v2.0 (c) 2005 Scott Baxter
Section C
ReradiatorsReradiators
February, 2005 Supplement - 19RF100 v2.0 (c) 2005 Scott Baxter
Cell RR
Wireless Reradiators
Reradiators (also called “boosters”, “repeaters”, “cell enhancers”) are amplifying devices intended to add coverage to a cell site Reradiators are transparent to the host Wireless system
• A reradiator amplifies RF signals in both directions, uplink and downlink
• The system does not control reradiators and has no knowledge of anything they do to the signals they amplify, on either uplink or downlink
Careful attention is required when using reradiators to solve coverage problems
• to achieve the desired coverage improvement
• to avoid creating interference• to ensure the active search window is large
enough to accommodate both donor signal and reradiator signal as seen by mobiles
Reradiators are a ‘“crutch” with definite application restrictions. Many operators prefer not to use re-radiators at all. However, reradiators are a cost-effective solution for some problems.
February, 2005 Supplement - 20RF100 v2.0 (c) 2005 Scott Baxter
Wireless Reradiators
Two types of Reradiators commonly are applied to solve two types of situations:
• “filling in” holes within the coverage area of a cell site -- valleys and other obstructed locations, convention centers, etc.
– Low-Power broadbandreradiators are used for this purpose (AMPS, TDMA, GSM, CDMA)
• expanding the service area of a cell to large areas beyond its natural coverage area
– High-Power, channelized frequency-translating reradiatorsare used for this purpose
– Only used in AMPS, TDMA; not currently feasible for CDMA
CellRR
Cell RR
February, 2005 Supplement - 21RF100 v2.0 (c) 2005 Scott Baxter
Wireless ReradiatorsPropagation Path Loss Considerations
To solve a coverage problem using a reradiator, path loss and link budget must be considered
• how much reradiator gain is required?• how much reradiator output power is required?• what type of antennas would be best? • how much antenna isolation is needed?• how big will the reradiator footprint be?• how far can the reradiator be from the cell?• will the reradiator interfere with the cell in other areas?• What is the propagation delay through the reradiator, in chips?• Will search windows need to be adjusted for compensation?
CellRR
ERP
GainPath Loss
Path Loss (free space??)
Gain
RRGain
Line Loss
Signal Levelin target area
(free spaceusually applies)
February, 2005 Supplement - 22RF100 v2.0 (c) 2005 Scott Baxter
Wireless ReradiatorsSearch Window Considerations
A reradiator introduces additional PN delay• typically 5 to 30 chips • the energy seen by the mobile and by the base station is
spread out over a wider range of delays
DonorCell
RR
ReradiatorSignal
Direct Signal fromDonor Cell
Delay = ? chips
DON’T FORGET THE WINDOWS!Search Windows must be widened byapproximately 2 x reradiator delay toensure capture of both donor and reradenergy by mobile and base station.•Srch_Win_A, Srch_Win_R, Srch_Win_N•Base station Acquisition & Demodulationsearch windows
Reference PNDonor Energy Reradiator Energy
February, 2005 Supplement - 23RF100 v2.0 (c) 2005 Scott Baxter
In a few special cases, it is possible to reradiate useful Wireless coverage without any amplifiers involved!Link budget is marginal
• donor cell must be nearby• high-gain antenna required toward
donor cell• distance from RR to user must be
small– ≅100 feet feasible w/omni
antenna– ≅500 feet w/directional antenna
Passive Wireless ReradiatorsTypical Link Budget
Donor cell EIRPPath Loss Donor<>RR
RR Donor Ant. GainSignal Level into Line
RR Line LossRR Serving Ant. GainPath Loss RR<>UserSignal Level @ User
+52-102+22-28-6
+12-69-91
dBmdBdBidBmdBdBidBdBm
Passive ReradiatorLink Budget Example
DonorCell
ERP
Path Loss
Path Loss (250 ft., free space)
(2.1 miles,free space) Basement Auditorium, etc.
Line Loss-6 db
February, 2005 Supplement - 24RF100 v2.0 (c) 2005 Scott Baxter
Broadband Low-Power Wireless Reradiators
Used mainly for filling small “holes” in coverage area of a cellInput and output on same frequency
• usable gain: must be less than isolation between antennas, or oscillation occurs
• this gain restriction seriously limits available coverage
• Typically achievable isolations: 70-95 dB
• Good point: every channel in donor cell is re-radiated
BPF:Uplink
BPF:Downlink
Wireless Spectrum
Frequency
Cell
BroadbandReradiator
UnavoidableCoupling
Combiner
Combiner
February, 2005 Supplement - 25RF100 v2.0 (c) 2005 Scott Baxter
Broadband low-power reradiators can deliver useful signal levels over footprints up to roughly 1 mile using nearby donor cellsLink budget is usually very “tight”
• paths can’t be seriously obstructed• antenna isolation must be at least
10 db more than desired RR gain• can’t overdrive reradiator 3rd.
order IM
Broadband Low-Power Wireless ReradiatorsTypical Link Budget
DonorCell RR
ERP
GainPath Loss
Path Loss (1/2 mile,
free space)
Gain
RRGain
Line Loss
Signal Levelin target area
(6 miles,free space)
Donor cell EIRPPath Loss Donor<>RR
RR Donor Ant. GainRR Line Loss
Signal Level into RRRR Gain
RR Power OutputRR Line Loss
RR Serving Ant. GainPath Loss RR<>UserSignal Level @ User
+52-111+12
-3-50+50+0-3
+12-89.4-80.4
dBmdBdBidBdBmdBdBmdBdBidBdBm
Broadband ReradiatorLink Budget Example
February, 2005 Supplement - 26RF100 v2.0 (c) 2005 Scott Baxter
Other Reradiator Issues
Amplification of Undesired Signals• The reradiator is a broadband device capable of amplifying
other signals near the intended CDMA carrier, both on uplink and downlink. Will these signals capture unwanted traffic, cause unwanted interference, or overdrive CDMA handsets or the base station?
Linearity• CDMA reradiators must be carefully adjusted to ensure they
are not overdriven. Overdriving would produce clipping or other nonlinearities, resulting in code interference
Traffic Capacity• Re-radiators may introduce enough new traffic to create
overloads in the donor cellAlarms
• Separate arrangements must be made for integrating alarms and surveillance reports from reradiators into the system
February, 2005 Supplement - 27RF100 v2.0 (c) 2005 Scott Baxter
Section D
Operational MeasurementsSome Capacity ConsiderationOperational Measurements
Some Capacity Consideration
February, 2005 Supplement - 28RF100 v2.0 (c) 2005 Scott Baxter
Total Blocked Call Percentage Example
This is an example of a cumulative system-wide total blocked call percentage chart maintained by one PCS customer
Total Block Call Percentage
1.0%1.5%2.0%2.5%3.0%3.5%4.0%4.5%5.0%5.5%6.0%6.5%7.0%7.5%8.0%
Date
Perc
ent
Blkd
February, 2005 Supplement - 29RF100 v2.0 (c) 2005 Scott Baxter
Dropped Call Percentage Tracking Example
Dropped call percentage tracking by a PCS customer.
Total Drop Call Percentage
0.0%
0.5%
1.0%
1.5%
2.0%
2.5%
3.0%
3.5%
4.0%
4.5%
5.0%
Date
Perc
ent
%Drops
February, 2005 Supplement - 30RF100 v2.0 (c) 2005 Scott Baxter
Total System Daily MOU Example
Total system daily MOU plotted by a PCS customer
Daily Total System MOU
0
50000
100000
150000
200000
250000
300000
Date
MO
U
Daily Total System MOU
February, 2005 Supplement - 31RF100 v2.0 (c) 2005 Scott Baxter
“Top Ten” Performance Tracking Example
Many operators use scripts or spreadsheet macros to produce ranked lists of sites with heavy traffic, performance problems, etc.
Call Attempts
Eng Site
MSC Site Call Att
Call Succ
%Call Succ
Block Calls
%Blck Calls
Acc Fail
%Acc Fail
Drop Calls
%Drop Calls Call Attempts
6.1 13X 2561 2234 87.2 130 5.1 130 5.1 145 5.72.1 2X 2244 2017 89.9 101 4.5 101 4.5 93 4.11.2 1Y 1922 1743 90.7 83 4.3 83 4.3 66 3.464.3 93Z 1833 1549 84.5 137 7.5 136 7.4 110 6.0108.2 30Y 1740 1589 91.3 46 2.6 45 2.6 83 4.81.3 1Z 1630 1495 91.7 31 1.9 31 1.9 81 5.063.2 57Y 1623 1486 91.6 49 3.0 49 3.0 66 4.1102.2 4Y 1615 1495 92.6 18 1.1 18 1.1 70 4.3108.1 30X 1490 1387 93.1 27 1.8 27 1.8 54 3.643.3 42Z 1488 1410 94.8 4 0.3 4 0.3 53 3.6
0
500
1000
1500
2000
2500
3000
6.1
2.1
1.2
64.3
108.
2
1.3
63.2
102.
2
108.
1
43.3
Sector
Cal
ls
% Blocked Calls September 5, 1997Eng Site
MSC Site Call Att
Call Succ
%Call Succ
Block Calls
%Blck Calls
Acc Fail
%Acc Fail
Drop Calls
%Drop Calls % Blocked Calls
64.3 93Z 1833 1549 84.5 137 7.5 136 7.4 110 6.06.1 13X 2561 2234 87.2 130 5.1 130 5.1 145 5.763.3 57Z 1282 1098 85.7 65 5.1 65 5.1 90 7.02.1 2X 2244 2017 89.9 101 4.5 101 4.5 93 4.11.2 1Y 1922 1743 90.7 83 4.3 83 4.3 66 3.463.2 57Y 1623 1486 91.6 49 3.0 49 3.0 66 4.164.1 93X 1027 926 90.2 30 2.9 30 2.9 58 5.726.3 35Z 855 698 81.6 24 2.8 24 2.8 112 13.1108.2 30Y 1740 1589 91.3 46 2.6 45 2.6 83 4.81.3 1Z 1630 1495 91.7 31 1.9 31 1.9 81 5.0
0.01.02.03.04.05.06.07.08.0
64.3 6.1
63.3 2.1
1.2
63.2
64.1
26.3
108.
2
1.3
Sector%
February, 2005 Supplement - 32RF100 v2.0 (c) 2005 Scott Baxter
Lucent Reports
This figure shows various operating statistics available throughAutoPace from Lucent systems
• forward power control status• origination failures and dropped calls
Highlight by CDMA_Acs Chn_Oc (2,1,0, ) Mean: 28.2 Std Dev: 27.83 Sort by Sys/ECP/Ce ll/Name /Antenna ID /Ant_Name
Sys/ECP/Ce ll/Name /Antenna ID /Ant_Name CDMA_Acs CDMA_Avg CDMA_Fwd CDMA_Fwd CDMA CDMA_Pg CDMA_Pk CDMA_Pk CDMA_Rev CDMA_RevChn_Oc Sq_DG PCOLdur PCOLcnt Intcpt_Msg Ch_Ocpn Acs_ChOc Pg_ChOc PCOLdur PCOLcnt
TOTALS 5,921.00 1,123,466 581.00 339.00 0.00 489,506 91,989 555,984 305.00 6.00 179 2 1 JACKSON 1 Antenna:1 30.00 6,187.00 12.00 4.00 0.00 2,771.00 985.00 3,264.00 0.00 0.00 179 2 1 JACKSON 2 Antenna:2 28.00 6,157.00 4.00 4.00 0.00 2,763.00 563.00 3,140.00 0.00 0.00 179 2 1 JACKSON 3 Antenna:3 10.00 6,088.00 2.00 1.00 0.00 2,754.00 281.00 3,197.00 0.00 0.00 179 2 2 WILDER 1 Antenna:1 27.00 6,168.00 0.00 0.00 0.00 2,795.00 563.00 3,125.00 0.00 0.00 179 2 2 WILDER 2 Antenna:2 13.00 5,016.00 0.00 0.00 0.00 2,756.00 422.00 3,120.00 0.00 0.00 179 2 2 WILDER 3 Antenna:3 13.00 4,818.00 0.00 0.00 0.00 2,766.00 281.00 3,155.00 0.00 0.00 179 2 3 MARKET 1 Antenna:1 4.00 6,200.00 0.00 0.00 0.00 2,760.00 140.00 3,100.00 0.00 0.00 179 2 3 MARKET 2 Antenna:2 10.00 6,073.00 0.00 0.00 0.00 2,731.00 422.00 3,195.00 0.00 0.00 179 2 3 MARKET 3 Antenna:3 55.00 6,580.00 5.00 3.00 0.00 2,809.00 845.00 3,391.00 0.00 0.00
Highlight by %CDMA Est Ca lls (2,1,0, ) Mean: 96.71 Std Dev: 1.22 Sort by %CDMA Est Ca lls
Sys/ECP/Ce ll/Name /Labe l %CDMA ReAcquir CCE CDMA_CE Prim_CS %Prim_CS Sec_CS %CDMA %CDMA CDMA %CDMA T otCDMA CDMAT otlEst Ca lls ed_Ca lls e rlangs Usage CE_Use CE_Use CE_Use SoftHO Use SUFa il Lost_Ca ll Lost Ca lls Fa ilures Origins
TOTALS 96.83 2.84 6,580 2,368,959 1,451,816 61.28 917,143 38.72 2.79 1,722.00 1.17 7,856.00 5,069.00 179 2 67 MARSHALL 93.55 3.22 62.60 22,535.00 9,300.00 41.27 13,235.00 58.73 6.14 15.00 1.67 95.00 65.00
179 2 10 TIGER 93.58 2.61 128.68 46,323.00 19,788.00 42.72 26,535.00 57.28 5.68 42.00 2.18 208.00 143.00 179 2 28 LEATHERWOOD 94.18 3.89 71.45 25,722.00 13,689.00 53.22 12,033.00 46.78 5.44 20.00 1.18 143.00 89.00
179 2 30 SHEPHERDS 94.36 2.38 63.54 22,873.00 11,113.00 48.59 11,760.00 51.41 3.62 10.00 0.89 77.00 47.00 179 2 121 PENTAGON 94.44 5.26 36.16 13,016.00 8,448.00 64.90 4,568.00 35.10 3.68 64.00 5.98 108.00 73.00
179 2 1 COLLEGE 94.67 2.65 76.37 27,494.00 15,965.00 58.07 11,529.00 41.93 4.64 15.00 0.98 102.00 67.00 179 2 45 MARYLAND 94.73 2.06 115.21 41,476.00 23,219.00 55.98 18,257.00 44.02 5.04 35.00 1.44 206.00 141.00 179 2 16 AVONDALE 94.90 2.99 98.26 35,372.00 20,059.00 56.71 15,313.00 43.29 4.47 41.00 1.78 178.00 130.00
February, 2005 Supplement - 33RF100 v2.0 (c) 2005 Scott Baxter
BTSC MO Attributes
Attribute Name DataType
Seq.Number
Access,Range Description
BlockedOriginationsNoTCE word16 0x0002A42
Pfull
Number of originations blocked because no idle channel elements were available
BlockedOriginationsNoFwdCap 0x0002B43
Number of originations blocked due to lack of BTS forward link excess capacity
BlockedOriginationsNoRevCap 0x0002C44
Number of originations blocked due to lack of reverse link capacity
BlockedHandoffsNoTCE 0x0002D45
Number of handoffs blocked because no idle channel elements were available
BlockedHandoffsNoFwdCap 0x0002E46
Number of handoffs blocked due to lack of BTS forward link excess capacity
BlockedHandoffsNoRevCap 0x0002F47
Number of handoffs blocked due to lack of reverse link capaicty
SuccessfulOriginations 0x0003048 Number of successful originations
SuccessfulHandoffs 0x0003149 Number of successful handoffs
word16
word16
word16
word16
word16
word16
word16
Pfull
Pfull
Pfull
Pfull
Pfull
Pfull
Pfull
Each attribute is a periodic counter maintained during the 15-minute automatic logging period.
February, 2005 Supplement - 34RF100 v2.0 (c) 2005 Scott Baxter
Nortel FA MO AttributesEach attribute is a periodic counter maintained during the 15-minute automatic logging period.
FA MO Sequence Number OM name
FA MO Sequence Number OM name
16 TCEUtilMaximum 2D soft4softer1Alpha17 NumOfTCsConfigured 2E soft4softer1Beta18 soft1softer1Alpha 2F soft4softer1Gamma19 soft1softer1Beta 30 soft4softer2AlphaBeta1A soft1softer1Gamma 31 soft4softer2BetaGamma1B soft1softer2AlphaBeta 32 soft4softer2GammaAlpha1C soft1softer2BetaGamma 33 soft4softer31D soft1softer2GammaAlpha 34 soft5softer1Alpha1E soft1softer3 35 soft5softer1Beta1F soft2softer1Alpha 36 soft5softer1Gamma20 soft2softer1Beta 37 soft5softer2AlphaBeta21 soft2softer1Gamma 38 soft5softer2BetaGamma22 soft2softer2AlphaBeta 39 soft5softer2GammaAlpha23 soft2softer2BetaGamma 3A soft6softer1Alpha24 soft2softer2GammaAlpha 3B soft6softer1Beta25 soft2softer3 3C soft6softer1Gamma26 soft3softer1Alpha 3D TimeNotInUse27 soft3softer1Beta28 soft3softer1Gamma29 soft3softer2AlphaBeta2A soft3softer2BetaGamma2B soft3softer2GammaAlpha2C soft3softer3
February, 2005 Supplement - 35RF100 v2.0 (c) 2005 Scott Baxter
Nortel BTSC MO Events
Event Report Name TypeEvent Report
Seq.Number Description
Each event counter is maintained during the 15-minute automatic logging period.
BTSCPerformanceData PerformanceData 0x000?0?
Includes as parameters all attributes with P access documented in the attribute table for
this MO.
FA MO Events
Event Report Name TypeEvent Report
Seq.Number Description
Each event counter is maintained during the 15-minute automatic logging period.
FAPerformanceData PerformanceData 0x000?0?
Includes as parameters all attributes with P access documented in the attribute table for
this MO.
February, 2005 Supplement - 36RF100 v2.0 (c) 2005 Scott Baxter
Nortel BTSC MO Report Example
XYZ 19971120 BTSC MO Report+----+----------------------------+------+------+------+------+------+------+------+------+|BTS | Start Date/Time - |OBlock|OBlock|OBlock|HBlock|HBlock|HBlock| Succ | Succ || | End Date/Time |No TCE|No Fwd|No Rev|No TCE|No Fwd|No Rev| Origs|Handof|+----+----------------------------+------+------+------+------+------+------+------+------+| 1|1997/11/20 01:30:00-02:00:00| 0| 0| 0| 0| 0| 0| 3| 5|| 1|1997/11/20 12:00:00-12:30:00| 0| 0| 0| 0| 0| 0| 46| 314|| 1|1997/11/20 12:30:00-13:00:00| 0| 0| 0| 0| 0| 0| 76| 470|| 1|1997/11/20 13:00:00-13:30:00| 0| 0| 0| 0| 0| 0| 45| 414|| 1|1997/11/20 13:30:00-14:00:00| 0| 0| 0| 0| 0| 0| 55| 375|| 1|1997/11/20 14:00:00-14:30:00| 0| 0| 0| 0| 0| 0| 50| 525|| 1|1997/11/20 14:30:00-15:00:00| 0| 0| 0| 0| 0| 0| 72| 433|| 1|1997/11/20 15:00:00-15:30:00| 0| 0| 0| 0| 0| 0| 66| 412|| 1|1997/11/20 15:30:00-16:00:00| 0| 0| 0| 0| 0| 0| 53| 323|| 1|1997/11/20 16:00:00-16:30:00| 0| 0| 0| 0| 0| 0| 63| 342|| 1|1997/11/20 16:30:00-17:00:00| 0| 0| 0| 0| 0| 0| 51| 331|| 1|1997/11/20 17:00:00-17:30:00| 0| 0| 0| 0| 0| 0| 39| 323|| 1|1997/11/20 17:30:00-18:00:00| 0| 0| 0| 0| 0| 0| 51| 310|| 1|1997/11/20 18:00:00-18:30:00| 0| 0| 0| 0| 0| 0| 45| 237|| 1|1997/11/20 18:30:00-19:00:00| 0| 0| 0| 0| 0| 0| 31| 299|| 1|1997/11/20 19:00:00-19:30:00| 0| 0| 0| 0| 0| 0| 37| 282|| 1|1997/11/20 19:30:00-20:00:00| 0| 0| 0| 0| 0| 0| 19| 143|| 1|1997/11/20 20:00:00-20:30:00| 0| 0| 0| 0| 0| 0| 18| 96|| 1|1997/11/20 20:30:00-21:00:00| 0| 0| 0| 0| 0| 0| 33| 192|| 1|1997/11/20 21:00:00-21:30:00| 0| 0| 0| 0| 0| 0| 25| 226|| 1|1997/11/20 21:30:00-22:00:00| 0| 0| 0| 0| 0| 0| 15| 235|| 1|1997/11/20 22:00:00-22:30:00| 0| 0| 0| 0| 0| 0| 15| 216|| 1|1997/11/20 22:30:00-23:00:00| 0| 0| 0| 0| 0| 0| 9| 162|| 1|1997/11/20 23:00:00-23:30:00| 0| 0| 0| 0| 0| 0| 3| 40|| |Totals for BTS 1 | 0| 0| 0| 0| 0| 0| 1235| 8895|
February, 2005 Supplement - 37RF100 v2.0 (c) 2005 Scott Baxter
Nortel FAMO Report Example
XYZ 19971120 FA MO Report+----+----------------------------+---------+---------+-----+-------+-------+-------+-----+---+|BTS | Start Date/Time - | MOU | MOU | CE/ | MOU | MOU | MOU |%Soft|Max|| | End Date/Time | CE | Traffic | User| Alpha | Beta | Gamma | HO |TCE|+----+----------------------------+---------+---------+-----+-------+-------+-------+-----+---+| 1|1997/11/20 07:00:00-07:30:00| 41.99| 33.35| 1.26| 11.77| 4.62| 16.96|20.58| 15|| 1|1997/11/20 07:00:00-07:30:00| 73.06| 46.22| 1.58| 17.72| 14.10| 14.39|36.75| 15|| 1|1997/11/20 08:00:00-08:30:00| 109.87| 66.05| 1.66| 24.78| 20.21| 21.06|39.88| 15|| 1|1997/11/20 10:00:00-10:30:00| 153.79| 89.81| 1.71| 41.85| 32.19| 15.77|41.60| 15|| 1|1997/11/20 10:30:00-11:00:00| 181.09| 102.19| 1.77| 43.60| 28.22| 30.38|43.57| 15|| 1|1997/11/20 11:00:00-11:30:00| 152.59| 84.73| 1.80| 37.61| 18.51| 28.61|44.47| 15|| 1|1997/11/20 11:30:00-12:00:00| 143.70| 89.16| 1.61| 39.66| 24.78| 24.72|37.95| 15|| 1|1997/11/20 12:00:00-12:30:00| 156.58| 89.52| 1.75| 25.51| 21.91| 42.10|42.83| 15|| 1|1997/11/20 12:30:00-13:00:00| 165.54| 89.97| 1.84| 44.41| 22.89| 22.67|45.65| 15|| 1|1997/11/20 13:00:00-13:30:00| 170.36| 99.19| 1.72| 52.81| 24.58| 21.79|41.78| 15|| 1|1997/11/20 13:30:00-14:00:00| 145.34| 93.71| 1.55| 41.88| 24.05| 27.77|35.53| 15|| 1|1997/11/20 14:00:00-14:30:00| 189.61| 121.49| 1.56| 52.43| 30.99| 38.06|35.93| 15|| 1|1997/11/20 14:30:00-15:00:00| 153.65| 108.08| 1.42| 47.58| 37.52| 22.99|29.65| 15|| 1|1997/11/20 15:00:00-15:30:00| 165.08| 106.66| 1.55| 49.00| 29.69| 27.97|35.39| 15|| 1|1997/11/20 15:30:00-16:00:00| 159.27| 94.72| 1.68| 42.04| 28.43| 24.25|40.53| 15|| 1|1997/11/20 16:00:00-16:30:00| 172.52| 114.62| 1.51| 56.57| 28.50| 29.55|33.56| 15|| 1|1997/11/20 16:30:00-17:00:00| 156.83| 105.46| 1.49| 53.29| 30.38| 21.80|32.76| 15|| 1|1997/11/20 17:00:00-17:30:00| 129.13| 82.52| 1.56| 31.50| 24.28| 26.73|36.10| 15|| 1|1997/11/20 17:30:00-18:00:00| 134.80| 81.76| 1.65| 35.80| 30.20| 15.77|39.35| 15|| 1|1997/11/20 18:00:00-18:30:00| 96.91| 60.49| 1.60| 27.80| 15.38| 17.31|37.58| 15|| 1|1997/11/20 18:30:00-19:00:00| 124.25| 73.62| 1.69| 22.37| 30.93| 20.33|40.75| 15|| 1|1997/11/20 19:00:00-19:30:00| 75.50| 41.14| 1.83| 18.03| 14.88| 8.24|45.50| 15|| 1|1997/11/20 19:30:00-20:00:00| 40.58| 23.56| 1.72| 12.50| 5.72| 5.33|41.95| 15|| 1|1997/11/20 20:00:00-20:30:00| 51.14| 29.81| 1.72| 13.26| 10.37| 6.19|41.71| 15|| 1|1997/11/20 20:30:00-21:00:00| 102.45| 55.26| 1.85| 16.36| 18.49| 20.41|46.07| 15|| 1|1997/11/20 21:00:00-21:30:00| 108.48| 74.86| 1.45| 28.32| 17.26| 29.27|30.99| 15|| 1|1997/11/20 21:30:00-22:00:00| 109.92| 68.50| 1.60| 26.53| 19.22| 22.75|37.68| 15|| 1|1997/11/20 22:00:00-22:30:00| 86.58| 59.36| 1.46| 26.09| 15.11| 18.15|31.45| 15|| 1|1997/11/20 22:30:00-23:00:00| 94.96| 63.48| 1.50| 27.73| 20.85| 14.90|33.15| 15|| 1|1997/11/20 23:00:00-23:30:00| 28.07| 20.76| 1.35| 9.06| 8.14| 3.55|26.04| 15|| |Totals for BTS 1 | 3690.90| 2280.64| 1.62| 980.80| 655.61| 644.22|38.21| 15|
February, 2005 Supplement - 38RF100 v2.0 (c) 2005 Scott Baxter
Section E
Basics of Interference, Noise and CDMA Capacity
Basics of Interference, Noise and CDMA Capacity
February, 2005 Supplement - 39RF100 v2.0 (c) 2005 Scott Baxter
The Noise Floor
Even when no interference, a received signal must compete with the always-present noise in the receiver itselfAmbient heat causes electrons everywhere to move around, producing “thermal noise” in every electronic circuitThe noise power is proportional to absolute temperature and the receiving bandwidth; see equation at rightWhat this means for a CDMA receiver:
• There is an unavoidable noise of -113.1 dbm in the bandwidth of a CDMA signal, 1.2288 MHz.
See the spreadsheet “Noise.xls” below
THERMAL NOISE
Nt = kTBwhere:Nt = thermal noise powerK = Boltzmann’s Constant
= 1.3806 x 10-23
T = Temperature (Kelvin)= 290ºK room temperature
B = bandwidth
T, deg K BW, Hz Noise, dbm RX NF RX Sens. Remarks290 1 -174.0 0.0 -174.0 Theoretical Baseline290 1,228,800 -113.1 5.0 -108.1 Typical CDMA Uplink at BTS receiver290 1,228,800 -113.1 8.0 -105.1 Typical CDMA Downlink at Mobile Receiver
Thermal Noise Floor, Bandwidth, and Receiver Sensitivity
This noise is sometimes called “Johnson Noise”,
“White Noise”, and “Background Noise”
February, 2005 Supplement - 40RF100 v2.0 (c) 2005 Scott Baxter
Reverse Link Noise Floor Rise Due To TrafficThe first user on a sector must satisfy:
• User’s signal + CDMA processing gain must equal BTS thermal noise + BTS noise figure + desired Eb/No
The second user on a sector must satisfy• all the above PLUS first user’s energy• and the first user must also slightly
increase to match, maintaining its qualityEach additional user faces more interfering power from existing users, etc., etc.For given starting conditions, there is a number of users that drives the situation out of control – users must transmit more power than a CDMA mobile can produce
• This number of users is the “Pole Point”; this is the “Pole Capacity” of the sector
V = Voice Activity FactorW = Spreading BandwidthNo= P.S.D. of Thermal NoisePt = Mobile TxR = Vocoder Rate
February, 2005 Supplement - 41RF100 v2.0 (c) 2005 Scott Baxter
Loading and the Noise Floor
For two standard cell configurations, the spreadsheet shows the calculated pole point capacity and the intended operating limit at 50% of pole capacityThe graph shows the calculated receive power at a BTS for zero to 42 users under typical conditions
• notice a 10 db rise occurs with just 12 users• a 15 db rise occurs with just 15 users• this cell’s capacity needs optimization!
Explore the Noise Floor Rise spreadsheet to see the effects of target Eb/No, BTS noise figure, and other parameters on the results
3-Sector BTS Pole Capacity
Per Sector
6-Sector BTS Pole Capacity
Per SectorOperating Limit: 50% Pole 20.9 18.5
100% Pole Point #Users 41.8 37.0Processing Gain 128.00 128.00
#Sectors 3 6Sectorization Gain 2.55 4.50
Voice Activity Factor 0.40 0.40Adjacent Cell Interference 0.60 0.60
Target Eb/No, ratio 4.17 4.17Radio Configuration RC1 RC1
Vocoder EVRC EVRCChip Rate 1,228,800 1,228,800 Data Rate 9,600 9,600
Required Eb/No, db 6.20 6.20
Noise Floor Rise Due To Loading
-120
-100
-80
-60
-40
-20
00 5 10 15 20 25 30 35 40 45
Number of Users
BTS
RX d
B
February, 2005 Supplement - 42RF100 v2.0 (c) 2005 Scott Baxter
What’s So Important About Noise Floor?
In theory, the capacity of a sector isn’t affected by the noise floor• as long as they’re strong enough, the desired number of
mobiles can use the sector simultaneouslyBut the range of the sector is directly determined by the noise floor
• when the noise floor is elevated by interference, the usable range of the cell shrinks proportionally
• users at the cell edge may be unable to access, unable to keep a call from dropping, unable to achieve high data rates, unable to keep acceptable FER
The noise floor at the BTS receiver is the point in the CDMA system most vulnerable to external interference
February, 2005 Supplement - 43RF100 v2.0 (c) 2005 Scott Baxter
Recognizing Interference: Do I have it?!!
Clues that you might have an interference problem:• Bad Stats: increased blocking, TCCFs, access failures, drops
worse than expected even in heavy traffic areas• clusters of several sectors with over 10% blocking• customer complaints of severe impairments, usually localized• increased noise floor in BTS statistics – both peak and average• depressed data throughput compared to healthy sectors
Field Observations• Visible non-CDMA signals on a spectrum analyzer • pockets in good-coverage areas where Ec/Io is poor due to
interference
February, 2005 Supplement - 44RF100 v2.0 (c) 2005 Scott Baxter
Interference? Track It Down!
OK, so you’ve got some solid evidence that interference is going on. How can you identify the source of the interference, and dosomething about it?For Reverse Link Interference:Identify the affected sectors to recognize affected areaField Investigation Normally Will Be Required
• look into BTS multicoupler outputs to identify interferer• spectrum analyzer and yagi antenna
– direction toward interferer from surrounding high sites –remember to use BP filter if needed to suppress strong fundamental so you can see true interference only
– triangulate to locate interferer– locate the source
February, 2005 Supplement - 45RF100 v2.0 (c) 2005 Scott Baxter
Identifying and Handling Interference Sources
Source will usually be a communications-related or power-related device; at building entry, ask if anyone is doing communications activities in that buildingUse company procedures for dealing with the interferer owner to obtain short-term resolutionLong-term resolution
• is signal unauthorized or unintended?– repair equipment if defective– does suppression meet required specs? add filter if needed
February, 2005 Supplement - 46RF100 v2.0 (c) 2005 Scott Baxter
Major Sources of Interference
Reverse Link• INTERNAL: maximum traffic loading is maximum acceptable
interference, just from “friendly fire”• Rogue Mobiles – a mobile needing handoff into the victim site but
unable to get it and transmitting high levels as it approaches• In-channel Narrowband Interferers
– military, land mobile, law enforcement, industrial• In-channel Unstable, parasitic, transmitters • In-band strong mobile signals of other operators on adjacent blocks• Broadband: welding shops, arcing signs and bulbs, utility transformers
and power lines with arcing insulators, dirty LANs• Oscillating or noisy in-building amplifiers, repeaters, and television
master antenna systems with booster amplifiers• sources can be very small, but near the BTS
Forward Link• symptom: localized interference, usually on one carrier (not all)• sources usually stronger than in reverse link case, easier to find
February, 2005 Supplement - 47RF100 v2.0 (c) 2005 Scott Baxter
Triangulation
Triangulation is the process of locating a transmitting source by measuring radial distance or direction of the received signal from several different pointsTriangulation can be used to pinpoint the geographic position of a user or interfererThe drawing shows the basic principle of triangulation.
• The emitter’s location is found by measuring the relative direction of the signal from three different locations.
• The area where the radials overlap becomes search area for the emitter’s exact location.
1
February, 2005 Supplement - 48RF100 v2.0 (c) 2005 Scott Baxter
Triangulation – Rounds Two and Up
The first round of triangulation will identify the vicinity of the emitter. However, the search area may still be impractically large.Another round of triangulation from closer points surrounding the search area may be required.When completed you should have 3 new intersecting lines which reveal the approximate location of the interferer within a triangle of uncertainty. This method can also be used to find interferers inside a large building.
1
February, 2005 Supplement - 49RF100 v2.0 (c) 2005 Scott Baxter
Site Configuration Principles
Antenna Isolation• Vertical separation highly effective
vs other operators but not desirable among our own antennas due to F/R imbalance
• Horizontal IsolationEstimating Isolation
• assume free space loss and published antenna patterns for “worst-case” maximum coupling scenario
Each operator should set minimum separation guidelines for general construction, based on intermodconsiderations of their own and their neighbors’ frequency bands and signal characteristics
Isolation
A widely-accepted general principle is to do whatever is required to achieve 40 db or better isolation between all antennas.
February, 2005 Supplement - 50RF100 v2.0 (c) 2005 Scott Baxter
Observed Isolations between PCS Antennas
Typical observed isolations between commonly-used PCS antennas at various horizontal and vertical separations
• thanks to Don Button and EMS Wireless
February, 2005 Supplement - 51RF100 v2.0 (c) 2005 Scott Baxter
IntermodulationIntermodulation
Section F
February, 2005 Supplement - 52RF100 v2.0 (c) 2005 Scott Baxter
Modulation and Mixing vs. Intermodulation
When two signals are intentionally combined in a non-linear device we call the effect modulation
• Amplitude modulator, or quad phase modulator• Mixer, down or up converter in superheterodyne
When two (or more) signals are unintentionally combined in a non-linear device, we call the effect intermodulation (a pejorative term)
An analogy: Botanists use soil to grow plants. But on your living room carpet, soil is just dirt.IM signals increase system noise, or cause distinctive recognizable interference signals
February, 2005 Supplement - 53RF100 v2.0 (c) 2005 Scott Baxter
Intermod Basics
Definition: Intermodulation (“IM”) is the unintended mixing of legitimate RF signals, producing undesired signals (‘intermodulation products’) on unrelated frequencies possibly already being used for other services
• IM can devastate reception on certain frequencies at base stations and other communication facilities
Intermodulation occurs because signals are passing through a nonlinear device, allowing each signal to alter the waveshape of the others
• the frequencies of the intermodproducts are sums and differences of multiples of the original signal frequencies, and can be calculated exactly
• the strength of the intermodproducts depends on the degree of nonlinearity of the circuits involved, and can be predicted with good accuracy using measured “intercept” levels
Power transfer characteristicsof typical amplifier or other device
Noise floor
Input power (dBm)
Outputpower(dBm)
Third orderintercept
point
Third orderintermodulation
products
Predictedpower
ff1 f2
Non-linear deviceInput Output
f3f1-2f2 3f2-2f1f1 f2
2f2-f12f1-f2