Class 1 UMTS Training
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Transcript of Class 1 UMTS Training
UMTS Overview
The Universal Mobile Telecommunications System (UMTS) is a third
generation wireless telecommunication system and follows in the footsteps of GSM and
GPRS. Since GSM was standardized in the 1980s, huge progress has been made in many
areas of telecommunication. This allowed system designers at the end of the 1990s to
design a new system that went far beyond the capabilities of GSM and GPRS.
UMTS combines the properties of the circuit-switched voice network with the
properties of the packet-switched data network and offers a multitude of new possibilities
compared to the earlier systems. UMTS was not defined from scratch and reuses a lot of
GSM and GPRS.
UMTS Radio Theory
The Basic Principles of Wireless Communication
I. 3G services
II. Multiple Access Technologies
III. Spectrum Planning
IV. Spreading Technology
V. Coding And Interleave Technology
VI. Modulation
UMTS Radio mechanism
I. UMTS Data transmission Procedure
II. Channel Coding of UMTS
III. Spreading Technology of UMTS
IV. Modulation of UMTS
UMTS Radio Theory
The Basic Principles of Wireless Communication
I. 3G servicesII. Multiple Access Technologies
III. Spectrum Planning
IV. Spreading Technology
V. Coding And Interleave Technology
VI. Modulation
UMTS Radio mechanism
I. UMTS Data transmission Procedure
II. Channel Coding of UMTS
III. Spreading Technology of UMTS
IV. Modulation of UMTS
3G Services
Data:I. 144 kbps High speed and driving
II. 384 kbps Modest speed and walking
III. 2 Mbps Low speed and indoor
Voice
I. 4.75Kb/s --12.2Kb/s
II. 64kb/s (Video Phone)
Information transmission at variable rate according to bandwidth requirements
Delay requirements of different service
3G Services Radio Transmission Technology Requirements
3G Services
3G Services
The Basic Principles of Wireless Communication
I. 3G services
II. Multiple Access TechnologiesIII. Spectrum Planning
IV. Spreading Technology
V. Coding And Interleave Technology
VI. Modulation
UMTS Radio mechanism
I. UMTS Data transmission Procedure
II. Channel Coding of UMTS
III. Spreading Technology of UMTS
IV. Modulation of UMTS
UMTS Radio Theory
Multiple Access Technologies
Duplex mode
TDD mode
Uplink and downlink has the same frequency
Adaptable to any frequency band
Suitable for both asymmetric and
symmetric services
TDD ( Time division duplex,
Such as TD-SCDMA)
FDD mode
Uplink and downlink has the different
frequency
Paired frequency bands are needed
Suitable for symmetric services
FDD( Frequency division duplex, Such as
WCDMA and CDMA2000)
Multiple Access Technologies
Multiple access technologies enable various users access public
communication line but without interference.
Why Multiple Access?
I. Increased capacity: serve more users
II. Reduced capital requirements since
fewer media can carry the traffic
III. Decreased per-user expense
Types of Transmission Medium:
I. Twisted pair
II. Coaxial cable
III. Fiber optic cable
IV. Air interface (radio signals)
Three methods are frequently used:
I. FDMA
II. TDMA
III. CDMA
Each pair of users enjoys a
dedicated, private circuit
through the transmission
medium, unaware that
theother users exist.
Multiple Access Technologies
A. Frequency Division Multiple Access means dividing the whole available spectrum
into many single radio channels (transmit/receive carrier pair). Each channel can
transmit one-way voice or control information. Analog cellular system is a typical
example of FDMA structure.
B. Time Division Multiple Access means that the wireless carrier of one bandwidth is
divided into multiple time division channels in terms of time (or called timeslot).
Each user occupies a timeslot and receives/transmits signals within this specified
timeslot. Therefore, it is called time division multiple access. This multiple access
mode is adopted in both digital cellular system and GSM.
C. Code division Multiple Access (CDMA) is a multiple access mode implemented
by Spreading Modulation. Unlike FDMA and TDMA, both of which separate the
user information in terms of time and frequency, CDMA can transmit the
information of multiple users on a channel at the same time. The key is that every
information before transmission should be modulated by different Spreading Code
to broadband signal, then all the signals should be mixed and send. The mixed
signal would be demodulated by different Spreading Code at the different receiver.
Because all the Spreading Code is orthogonal, only the information that was be
demodulated by same Spreading Code can be reverted in mixed signal.
Multiple Access Technologies
CDMA Application
Multiple Access Technologies
I. Users are distinguished by scrambling codes and OVSF codes
II. Self-interference system
III. CDMA system is restricted to interference (GSM system is restricted to frequency
resources)
The Basic Principles of Wireless Communication
I. 3G services
II. Multiple Access Technologies
III.Spectrum PlanningIV. Spreading Technology
V. Coding And Interleave Technology
VI. Modulation
UMTS Radio mechanism
I. UMTS Data transmission Procedure
II. Channel Coding of UMTS
III. Spreading Technology of UMTS
IV. Modulation of UMTS
UMTS Radio Theory
Single Frequency Network
Spectrum Planning
IMT-2000 Spectrum Allocation
Spectrum Planning
3G Spectrum Allocation in Sudan
Spectrum Planning
Allocated Spectrum
Main Operating Frequency Band:FDD mode:1920-1980 MHz / 2110-2170 MHz
TDD mode:1880-1920MHz、2010-2025 MHz
The Basic Principles of Wireless Communication
I. 3G services
II. Multiple Access Technologies
III. Spectrum Planning
IV.Spreading TechnologyV. Coding And Interleave Technology
VI. Modulation
UMTS Radio mechanism
I. UMTS Data transmission Procedure
II. Channel Coding of UMTS
III. Spreading Technology of UMTS
IV. Modulation of UMTS
UMTS Radio Theory
Spreading Technology
Spread Spectrum Principles:
SHANON Formula
• C = B * log2(1+S/N)
Where:
C is capacity of channel, b/s
B is signal bandwidth, Hz
S is average power for signal, W
N is average power for noise, W
It is the basic principle and theory for spread spectrum communications.
Spreading Technology
Spread Spectrum Principles:
User information bits are spread over a wide bandwidth by multiplying high speed
spread code(chip)
Spread signal bandwidth W wider than original signal bandwidth Rb
Spreading Technology
Spread Spectrum Principles:
Spreading Technology
Spread Spectrum Principles:
White noise refers to a statistical model for signals and signal sources, rather than to any specific signal
Spreading Mode
Spreading Technology
Direct sequence spread spectrum (DS-SS)Base band data is spread by multiplication of pseudo-noise sequence and base-band
pulse, the pseudo-noise sequence generated by the pseudo-noise generator
BER subject to Multiple Access Interference and near-far effect
Power control can overcome the near-far effect, but it is limited by power detection
accuracy
WCDMA uses DS_SS
Frequency hopping spread spectrum FH-SS)Data is transmitted in the random channel by the carrier frequency hopping
Before FH again, data is transmitted using traditional narrowband modulation
No near-far effect
DS-SS communication system
Spreading Technology
A technology of transmission after spreading signal spectrum.
Spreading Technology
Spread Spectrum Principles
Spreading Technology
Spread Spectrum Principles
Any Code Channel can be extracted from the received composite signal by
using the “right” orthogonal code
Energy for transmitting signal can be lower than interference and noise
Direct spread technique
Spreading Technology
Concept of Orthogonal Code
Orthogonal: the result
of multiplying and
sum is 0
Example of orthogonal code
Sketch map of Spreading and Despreading
Example of orthogonal code
Spreading Communication Characteristics
I. High anti-multi-path-interference capability
II. Anti-sudden-pulse
III. High security
IV. Lower transmitting power
V. Easy to implement large-capacity Multiple Access Communication
VI. Occupied frequency band is wide
VII.Complex realization
The Basic Principles of Wireless Communication
I. 3G services
II. Multiple Access Technologies
III. Spectrum Planning
IV. Spreading Technology
V. Coding And Interleave TechnologyVI. Modulation
UMTS Radio mechanism
I. UMTS Data transmission Procedure
II. Channel Coding of UMTS
III. Spreading Technology of UMTS
IV. Modulation of UMTS
UMTS Radio Theory
Purpose of Channel Coding
Coding And Interleave Technology
By adding redundant information in the original data stream,
receivers can detect and correct the error signal, and improve data
transmission rates.
Effect:
1. Enhance the correlation among symbols so as to recover the signal when
interference occurs
2. Provides better error correction at receiver, but brings increment of the delay
Principle of Channel Codingv:-
Coding And Interleave Technology
I. Error-correcting ability obtains by adding redundancy in the original data
II. Convolutional coding and Turbo coding (1/2,1/3)are widely applied.
III. Increase noneffective load and transmission time
IV. Suitable to correct few non-continuous errors
Example of ½ Convolutional Coding
Channel coding Types
WCDMA Channel Coding
Coding And Interleave Technology
During the transmission, there are many interferences and fading. To guarantee
reliable transmission, system should overcome these influence through the channel
coding which includes convolution and interleaving.
The first is convolution that is used for anti-interference. Through the technology,
many redundant bits will be inserted in original information. When error code is
caused by interference, the redundant bits can be used to recover the original
information.
In WCDMA network, both Convolution code and Turbo code are used.
Convolution code applies to voice service while Turbo code applies to high rate
data service.
Principle of Interleave Technology
Coding And Interleave Technology
In channel coding , there is another technology named interleaving. Communications over
radio channel are characterized by fast fading that can cause large numbers of consecutive
errors. Most coding schemes perform better on random data errors than on blocks of errors.
By interleaving the data, no two adjacent bits are transmitted near to each other, and the
data errors are randomized.
Note: - Interleaving period is 10,20,40 and 80 ms
Principle of Interleave Technology
Coding And Interleave Technology
Advantage:
Interleave is to change the sequence of data to random the unexpected errors
Advance the correcting validity
Disadvantage:
Increase the processing delay
Especially, Several independent random errors may intertwined for the unexpected
error.
Encoding and Interleaving
Coding And Interleave Technology
The Basic Principles of Wireless Communication
I. 3G services
II. Multiple Access Technologies
III. Spectrum Planning
IV. Spreading Technology
V. Coding And Interleave Technology
VI.Modulation
UMTS Radio mechanism
I. UMTS Data transmission Procedure
II. Channel Coding of UMTS
III. Spreading Technology of UMTS
IV. Modulation of UMTS
UMTS Radio Theory
Definition:-
Modulation is the process where the amplitude, frequency, or phase of an electronic
or optical signal carrier is changed in order to transmit information.
Using symbol stand for one or more bits to improve communication effectiveness
Classification:-
Analog Modulation (AM, FM & PM)
Digital Modulation (ASK, FSK & PSK)
Modulation
The Basic Principles of Wireless Communication
I. 3G services
II. Multiple Access Technologies
III. Spectrum Planning
IV. Spreading Technology
V. Coding And Interleave Technology
VI. Modulation
UMTS Radio mechanism
I. UMTS Data transmission process ProcedureII. Channel Coding of UMTS
III. Spreading Technology of UMTS
IV. Modulation of UMTS
UMTS Radio Theory
UMTS Data transmission process Procedure
UMTS Radio mechanism
WCDMA Source Coding
Source coding can increase the transmitting efficiency.
1. AMR (Adaptive Multi-Rate) Speech
A integrated speech codec with 8 source rates.
The AMR bit rates can be controlled by the RAN
depending on the system load and
Quality of the speech connections.
2. Video Phone Service
H.324 is used for VP Service in CS domain.
Includes: video codec, speech codec, data protocols,
multiplexing and etc.
AMR is compatible with current mobile communication system (GSM,
IS-95, PDC and so on), thus, it will make multi-mode terminal design easier.
The Basic Principles of Wireless Communication
I. 3G services
II. Multiple Access Technologies
III. Spectrum Planning
IV. Spreading Technology
V. Coding And Interleave Technology
VI. Modulation
UMTS Radio mechanism
I. UMTS Data transmission process Procedure
II. Channel Coding of UMTSIII. Spreading Technology of UMTS
IV. Modulation of UMTS
UMTS Radio Theory
Convolutional Code
Channel Coding of UMTS
Mainly used in the voice channel and control signal channel
Coding rate is ½ and 1/3.
Characteristics of Convolutional code:-
Easy decode
Short delay
Generally use the Viterbi Algorithm
Channel bit error rate is10 -3 magnitude
Suitable to realtime service
e.g. speech and video service.
Channel Coding of UMTS
Turbo Code
Used in Data service channel
Code Rate is 1/3
Can be implemented in the transmission for large block and long delay services
Turbo coding structure is based on two or more weak error control code
combinations. The information bits are interleaved in the two Encoder, and generate
two information flow. At last, this information can be multiplexed and punctured
Decoding needs cycle iterative calculation
Characteristics of Turbo Codes
Complex decoding
Use the LOG-MAP arithmetic
Channel bit error rate is 10-6 magnitude
Very suitable to non-realtime package service which is BER sensitive & delay
insensitive, e.g. WWW, FTP, E_mail, multimedia transmission
The Basic Principles of Wireless Communication
I. 3G services
II. Multiple Access Technologies
III. Spectrum Planning
IV. Spreading Technology
V. Coding And Interleave Technology
VI. Modulation
UMTS Radio mechanism
I. UMTS Data transmission process Procedure
II. Channel Coding of UMTS
III.Spreading Technology of UMTSIV. Modulation of UMTS
UMTS Radio Theory
Spreading Technology of UMTS
Spreading Process of UMTS
Spreading can increase the capability of overcoming interference.
Bit, Symbol, Chip
Bit : data after source coding
Symbol: data after channel coding and interleaving
Chip: data after spreading
Process Gain
Process gain differs for each service.
If the service bit rate is greater, the process gain is smaller, UE needs more power
for this service, then the coverage of this service will be smaller, vice versa.
For common services, the bit rate of voice call is 12.2kbps, the bit rate of
video phone is 64kbps, and the highest packet service bit rate is 384kbps(R99). After
the spreading, the chip rate of different service all become 3.84Mcps.
Spreading Technology of UMTS
Correlation
Correlation measures similarity between any two arbitrary signal, on other
hand determine the Identical and Orthogonal signals
Correlation is used to measure similarity of any two arbitrary signals. It is
computed by multiplying the two signals and then summing (integrating) the
result over a defined time windows. The two signals in figure (a) are identical and
therefore their correlation is 1 or 100 percent. In figure (b) , however, the two
signals are uncorrelated, and therefore knowing one of them does not provide any
information on the other.
Figure (a)
Figure (b)
Correlation
Cross Correlation: related to the multi-user interference characteristic
Auto Correlation: related to the multi-path interference characteristic
Orthogonal Code Usage - Coding
De-CodingCoding
Spreading Technology of UMTS
Channelization Code
OVSF Code (Orthogonal Variable Spreading Factor)
SF = chip rate / symbol rate
High data rates → low SF code
Low data rates → high SF code
Orthogonal codes are easily generated by starting with a seed of 1, repeating the 1
horizontally and vertically, and then complementing the -1 diagonally. This process is to
be continued with the newly generated block until the desired codes with the proper
length are generated. Sequences created in this way are referred as “Walsh” code.
Spreading code uses OVSF code, for keeping the orthogonality of different subscriber
physical channels. OVSF can be defined as the code tree illustrated in the following
diagram.
Spreading code is defined as Cch SF, k,, where, SF is the spreading factor of the code,
and k is the sequence of code, 0≤k≤SF-1. Each level definition length of code tree is SF
spreading code, and the left most value of each spreading code character is corresponding
to the chip which is transmitted earliest.
Spreading Technology of UMTS
Channelization Code
WCDMA Channelization Code
For uplink, Channelization code ( OVSF code ) is used to separate different physical
channels of one connection
For downlink, Channelization code ( OVSF code ) is used to separate different
connections in a cell
Purpose of Channelization Code
For voice service (AMR), downlink SF is 128, it means there are 128 voice services
maximum can be supported in one WCDMA carrier;
For Video Phone (64k packet data) service, downlink SF is 32, it means there are 32
voice services maximum can be supported in one WCDMA carrier.
WCDMA Scrambling Code – Gold Sequence
Scrambling codes Properties
38 400 chip long sequences
Repeated every 10 ms
Coming from Pseudo Noise sequences
For uplink, Scrambling code (Gold sequence) is used to separate different connection
For downlink, Scrambling code (Gold sequence) is used to separate different cell
Scrambling code sequence Generator
I. Gold sequence is made by two m sequence.
II. m sequence is generate by a series of shift-registers, and the period is 2n-1, here n
is the length of the shift-registers.
WCDMA Scrambling Code – Gold Sequence
Characteristic of Scrambling code
There are 224 Uplink Scrambling Codes, they are used to distinguish different users
in one cell.
There are 218 -1 Downlink Scrambling Codes, used to distinguish different cells
Scrambling codes usually used are the first 8192 codes, which are code 0,1
,……,8191. They are divided into 512 aggregations each aggregation has 1
primary scrambling code (PSC) and 15 secondary scrambling codes (SSC).
The 512 primary scrambling codes are divided further into 64 primary
scrambling code groups , with 8 primary scrambling codes in each group.
WCDMA Scrambling Code – Gold Sequence
Numbering rule for Downlink Scrambling Codes
WCDMA Code Functions
Channelization code :
for separation of physical channels in the uplink and separation of users
in the downlink
Scrambling code :
for separation of users/terminals in the uplink and cells/sectors in the
downlink.
Spreading code & scrambling code
Cch:spread code
Relative to service rate,extended to 3.84Mchips/s
A kind of orthogonal code
Cscrambling:scrambling code
Have no effect on signal bandwidth
Downlink for identifier cell,uplink identifier terminal
A pseudo-random sequence
Code Multiplexing
Downlink Transmission on a Cell Level
Code Multiplexing
Uplink Transmission on a Cell Level
Spreading and Despreading
Spreading Technology of UMTS
Spreading and Despreading
Spreading Technology of UMTS
Spreading and Despreading
Spreading Technology of UMTS
During the process of receiving the expected correct signal that belongs to the
subscriber, complete synchronous despreading codes are adopted for the despreading
operation. After obtaining the despreading data, the correlation receiver integrates the
resulting products, then get the integration data.
Signals of other subscribers using different spreading codes are actually the interference
signals to the first subscriber. In this case, multiply the signals and the despreading code of
the first subscriber to get the despreading signal, and then perform integration. Finally, an
interference signal with a signal value fluctuating along with 0 will be got. It can be
viewed that the signal amplitude of the subscriber increases by 8 times than that of the
other interference systems in average. That is to say, the correlation detection increases the
expected subscriber signal by the multiple of spreading factor value within the
interference of CDMA system. This effect is called “Processing Gain”, and it is the basic
characteristic of the spreading system. Elementarily, this kind of correlation receivers are
adopted for the BTS and UE in theWCDMA system. Because the existence of multi-path
propagation and multi receiving antennas, multiple correlation receivers are necessary for
retrieving the signal energy from all the paths or antennas. And the collection of these
correlation receivers forms the CDMA RAKE receiver.
Processing Gain
Spreading Technology of UMTS
PG=Wc/Rb (Where Wc : Chip rate , Rb : Service bit rate)
Transmitter/receiver can obtain gain after spread/despread
The narrower original signal bandwidth, the larger Pg , the better
The higher PG, the more anti-interference capability system has.
Relation between Eb/N0 and PG
Spreading Technology of UMTS
The Basic Principles of Wireless Communication
I. 3G services
II. Multiple Access Technologies
III. Spectrum Planning
IV. Spreading Technology
V. Coding And Interleave Technology
VI. Modulation
UMTS Radio mechanism
I. UMTS Data transmission process Procedure
II. Channel Coding of UMTS
III. Spreading Technology of UMTS
IV.Modulation of UMTS
UMTS Radio Theory
Modulation Overview
Modulation of UMTS
Modulation Overview
Modulation of UMTS
Modulation Overview
Modulation of UMTS
QPSK: Quadrature Phase Shift Keying . Phase shift keying in which four
different phase angles are used.
Modulation Overview
Modulation of UMTS
Modulation Methods in UMTS
BPSK (Binary Phase Shift Keying) in Uplink channles
QPSK (Quadrature Phase Shift Keying) in Downlink channels
16QAM (16-state Quadrature Amplitude Modulation) in HSDPA
Demodulation
Modulation of UMTS
QPSK Constellation Diagram
Principle of RAKE Receiver
RAKE receiver help to overcome on the multi-path fading and enhance the
receive performance of the system
When WCDMA systems were designed for cellular systems, the inherent wide bandwidth signals with their orthogonal
Walsh functions were natural for implementing a RAKE receiver. InWCDMA system, the bandwidth is wider than the
coherence bandwidth of the cellular. Thus, when the multi-path components are resolved in the receiver, the signals from
each tap on the delay line are uncorrelated with each other. The receiver can then combine themusing any of the combining
schemes. The WCDMA system then uses the multi-path characteristics of the channel to its advantage to improve the
operation of the system.
I. The RAKE receiver take advantage of multi-path diversity
II. The RAKE receiver processes the received signal
Identify the time delay positions at which significant energy arrives
Allocate correlation receivers (RAKE fingers) to those peaks
Within each Rake finger, track the fast-changing phase and amplitude values
Adjust the phase, remove the values originating from fast-fading
Combine the demodulated and phase-adjusted symbols across all active fingers
Present them to the decoder for further processing
III. This processing is called Maximal Ratio Combining
Principle of RAKE Receiver
WCDMA Signal Demodulation process
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