Post on 26-Dec-2015
ECEN5533 Modern Communications TheoryLecture #7 9 September 2014Dr. George Scheets
ECEN5533 Modern Communications TheoryLecture #7 9 September 2014Dr. George Scheets
Read 5.6 – 5.9Read 5.6 – 5.9 Scan Design Problem #1Scan Design Problem #1 Problems 5.14 & 5.15 Problems 5.14 & 5.15 Quiz #1 (Chapter 1) [4.5 Quiz #1 (Chapter 1) [4.5 << Uncorrected Scores Uncorrected Scores << 18.5] 18.5]
Remote DL: No later than 11 SeptemberRemote DL: No later than 11 September Reworked Quiz due 16 September (Live)Reworked Quiz due 16 September (Live)
Exam #1Exam #1 Local: 18 SeptemberLocal: 18 September Remote DL: No later 25 SeptemberRemote DL: No later 25 September
ECEN5533 Modern Communications TheoryLecture #8 11 September 2014Dr. George Scheets
ECEN5533 Modern Communications TheoryLecture #8 11 September 2014Dr. George Scheets
Problems 5.16 – 5.18, 5.21 Problems 5.16 – 5.18, 5.21 Quiz #1 (Chapter 1) Quiz #1 (Chapter 1)
Remote DL: No later than 11 SeptemberRemote DL: No later than 11 September Reworked Quiz due 16 September (Live)Reworked Quiz due 16 September (Live)
Exam #1Exam #1 Local: 18 SeptemberLocal: 18 September Remote DL: No later 25 SeptemberRemote DL: No later 25 September
Design Problem #1Design Problem #1 Due 25 September (Live)Due 25 September (Live) Not Later than 2 October (DL)Not Later than 2 October (DL)
ECEN5533 Modern Commo TheoryLesson #9 16 September 2014Dr. George Scheets
ECEN5533 Modern Commo TheoryLesson #9 16 September 2014Dr. George Scheets
Read 2.1 - 2.4Read 2.1 - 2.4 Problems: 2.1, 2.7, 2.9, 2.11Problems: 2.1, 2.7, 2.9, 2.11 Quiz #1 (Chapter 1) Quiz #1 (Chapter 1)
Reworked Quiz due 16 September (Live)Reworked Quiz due 16 September (Live) 1 week after return (DL)1 week after return (DL)
Exam #1 (covers Chapter 1, 5, and Chapter 2 Sampling Theory)Exam #1 (covers Chapter 1, 5, and Chapter 2 Sampling Theory) Local: Next Time!Local: Next Time! Remote DL: No later 25 SeptemberRemote DL: No later 25 September
Design Problem #1Design Problem #1 Due 25 September (Live)Due 25 September (Live) Not Later than 2 October (DL)Not Later than 2 October (DL)
Any graded HW is accepted lateAny graded HW is accepted late Cost is -1 point per working dayCost is -1 point per working day
Design #1: RoboCop RFPDesign #1: RoboCop RFP Design an RF Public Safety Commo systemDesign an RF Public Safety Commo system
for the city of Metropolis.for the city of Metropolis. Info Sinks can be anywhere in cityInfo Sinks can be anywhere in city Provide system analysis for worst case link.Provide system analysis for worst case link.
(0,0)
(59,47)
Info Source(51,39)
Design #1: RoboCop RFPDesign #1: RoboCop RFP
Configure Transmitter Site (1)Configure Transmitter Site (1) Where to locate? Where to locate?
Height of tower f(worst case distance)Height of tower f(worst case distance) Power OutPower Out Uplink center frequencyUplink center frequency Where be the electronicsWhere be the electronics??
Info Source(51,39)
Design #1: RoboCop RFPDesign #1: RoboCop RFP
Path Loss is cubed not squaredPath Loss is cubed not squared (4πd/λ)3
Antenna GainAntenna Gain Two sectorsTwo sectors
Hi GainHi Gain Low GainLow Gain
Design for WorstDesign for WorstCase G/Ls ratio.Case G/Ls ratio.
GHi
GLo
GHi/Ls1
GLo/Ls2
Design #1: RoboCop RFPDesign #1: RoboCop RFP
Configure Standard Receiver SystemConfigure Standard Receiver System 21,200 units21,200 units Specify LNA PreampSpecify LNA Preamp
Converts RF signal to IF or basebandConverts RF signal to IF or baseband IC AmpsIC Amps
Process RF or baseband, output basebandProcess RF or baseband, output baseband All choices have $$$ impactAll choices have $$$ impact
Many extra credit points available Many extra credit points available
Use a Spread Sheet!!!Use a Spread Sheet!!! Can use again (with mods) on Design 2Can use again (with mods) on Design 2 Tie in costs to design choicesTie in costs to design choices
Can see how changes affect costCan see how changes affect cost Get a system (any system) that worksGet a system (any system) that works
Output power Output power >> 1/4 watt & SNR 1/4 watt & SNR >> 32 dB 32 dB Anything over the minimum is Margin!!!Anything over the minimum is Margin!!!
System delivers 1/2 w & 35 dB SNR?System delivers 1/2 w & 35 dB SNR?Increase Margin by 3 dBIncrease Margin by 3 dB
Adjust parameters to reduce CostsAdjust parameters to reduce Costs Get some of those extra credit points!Get some of those extra credit points!
GradingGrading Real World RFP: Real World RFP:
1 team gets full credit1 team gets full credit Everyone else gets a zeroEveryone else gets a zero
Partial credit Partial credit Awarded on Quizzes & TestsAwarded on Quizzes & Tests NOT AWARDED ON DESIGN PROJECTS!NOT AWARDED ON DESIGN PROJECTS!
Real world designs don't get partial creditReal world designs don't get partial credit Either Work or They Don'tEither Work or They Don't
Double check your work!!! Double check your work!!! Use a spreadsheetUse a spreadsheet
Testable MaterialTestable Material
Communication Theory
Lecture Textbook
Homework
Anything inside the circles is fair game...but overlapped areas are more likely.
To Maximize your score…To Maximize your score… Budget your timeBudget your time Tackle all the problemsTackle all the problems
Partial Credit Partial Credit isis awarded awarded Show intermediate resultsShow intermediate results Obtain correct answerObtain correct answer
Tests are full period, 4 pages, 100 pointsTests are full period, 4 pages, 100 points Open book & notesOpen book & notes HW rework for HW rework for << 1/2 of lost points 1/2 of lost points
Low Noise AmpsLow Noise Amps
System TemperatureSystem Temperature
k*Tk*Tsystemsystem*W*Wnn*G*Gsystemsystem = =
Noise power out of systemNoise power out of system TTsystemsystem is referred to the is referred to the front front of an ideal systemof an ideal system
SNRSNRoutout = P = Pr r / k*T/ k*Tsystemsystem*W*Wnn
A high gain device on the front end helps lower A high gain device on the front end helps lower TTsystemsystem
Power Spectrum GPower Spectrum GXX(f)(f)
Key item for analyzing block diagramsKey item for analyzing block diagrams
Tracking Noise PowerTracking Noise Power
1/2∑ 108∑
Cable Amp
12.42(10-15)
24.01(10-15)
36.43(10-15) 18.22(10-15)
96.29(10-15)
114.5(10-15)
114.5(10-7)
Output SNR = 16.40 dB
Tracking Noise PowerTracking Noise Power
108∑ 1/2∑
Amp Cable
12.42(10-15)
96.29(10-15)
108.7(10-15) 108.7(10-7)
24.01(10-15)
108.7(10-7)
54.35(10-7)
Output SNR = 19.64 dB
MultipathMultipath
Multipath (20 m antenna height)Multipath (20 m antenna height)
Multipath (10 m antenna height)Multipath (10 m antenna height)
Urban Ray TracingUrban Ray Tracing
Image Source: IEEE Communications Magazine
Effect of Ionosphere (f < 35 MHz)Effect of Ionosphere (f < 35 MHz)
Line of Sight & Ground Wave
Ionosphere MultipathIonosphere Multipath
"Cue Ball" Earth"Cue Ball" Earth
Using Earth ContoursUsing Earth Contours
RF Link Equations...RF Link Equations...
are accurate forare accurate for Line of Sight Line of Sight Far Field Far Field No Multipath No Multipath
give a useful average forgive a useful average for Line of Sight Line of Sight Far Field Far Field Multipath Multipath
RF Link Equations...RF Link Equations...
can give ball park results forcan give ball park results for No Line of Sight No Line of Sight Far Field Far Field Multipath Multipathifif path loss is increased path loss is increased
Radio Horizon is 4/3 Optical HorizonRadio Horizon is 4/3 Optical Horizon
Analog to Digital Conversion)Part 1...Analog to Digital Conversion)Part 1...
Sampler
analoginputx(t)
discrete timeoutput
xs(t)
transmitter side
SamplingSampling Ideal SamplerIdeal Sampler
Minimum Sampling FrequencyMinimum Sampling Frequency > 2 * W > 2 * Wabsabs
Real World Realizable SamplerReal World Realizable Sampler Unable to build brick wall filtersUnable to build brick wall filters Must sample about 10% faster than 2*WMust sample about 10% faster than 2*Wabsabs
Output is discrete timeOutput is discrete time But contains info to reconstruct originalBut contains info to reconstruct original
Voltage is still Continuous Voltage is still Continuous Infinite Precision → Infinite # of bits/sampleInfinite Precision → Infinite # of bits/sample
Analog to Digital Conversion)Analog to Digital Conversion)
Sampler
analoginputx(t)
discrete time
signal
xs(t)
transmitter side
SourceCoder
bitstream
Analog to Digital ConversionAnalog to Digital Conversion
AnalogLow Pass
Filter
estimateof analog
input
discrete time signal
estimate
receiver side
SourceDecoder
bitstream
Video UndersamplingVideo Undersampling
Typical TV Video has 30 frames/secondTypical TV Video has 30 frames/second Frame = Still PictureFrame = Still Picture
Car CommercialCar CommercialWheel spokes moving the wrong wayWheel spokes moving the wrong wayWheel spokes stationary, car movingWheel spokes stationary, car moving→ fs not high enough→ fs not high enough
24 bit color 224 = 16.78 M colors24 bit color 224 = 16.78 M colors
256 Colors256 Colors
16 Colors16 Colors
Example) Coding aMicrophone Output
Example) Coding aMicrophone Output
time (sec)
m(t) volts (air pressure)
Energy from about 500 - 3,500 Hz.
A/D ConvertorA/D Convertor
time (sec)
m(t) volts (air pressure)
Step #1)Sample the waveform at rate > 2*Max Frequency.Convert samples to a bit stream.Wired telephone voice is sampled at 8,000 samples/second.
1/8000 second
A/D ConvertorA/D Convertor
time (sec)
m(t) volts (air pressure)
Step #2)Convert the sample voltages to a bit stream.Suppose m(t1) = 3.62 volts...
3.62 v
t1
A/D ConverterA/D Converter Simplest technique is PCMSimplest technique is PCM
Wired Telephone SystemWired Telephone System Audio Compact Disks Audio Compact Disks
Pulse Code ModulationPulse Code ModulationRound off to N possible voltages Round off to N possible voltages Equal length Code word is assigned toEqual length Code word is assigned to
each voltageeach voltageN Typically a Power of 2N Typically a Power of 2LogLog22N bits per code wordN bits per code word
A/D Convertor. 1 bit/sample.A/D Convertor. 1 bit/sample.
time (sec)
Example) N = 2. Assign 0 or 1 to voltage.
0 < Voltage < +5v, Assign Logic 1-5v < Voltage < 0, Assign Logic 0
3.62 v, output a 1
t1
Bit Stream Out = 1111110000111...
A/D Convertor. 1 bit/sample.A/D Convertor. 1 bit/sample.Example) N = 2. Assign 0 or 1 to voltage.
Far side gets... 1111110000111 (13 samples)Need to output 13 voltages.What does a 1 represent? A 0?
Receive a 1? Output +2.5 v (mid-range)Receive a 0? Output -2.5 v (mid-range)
Hold the voltage until next sample
0 < Voltage < +5v, Assign Logic 1-5v < Voltage < 0, Assign Logic 0
A/D Convertor. 1 bit/sample.A/D Convertor. 1 bit/sample.
Input to the transmitter.Output at the receiver.
Considerable Round-Off error exists.
+2.5 v
-2.5 v
time (sec)
Example) N = 4. Assign 00, 01, 10 or 11.
2.5 < Voltage < 5 , Assign 110 < Voltage < 2.5, Assign 10-2.5 < Voltage < 0, Assign 00-5 < Voltage < -2.5, Assign 01
3.62 v, Assign 11
t1
Bit Stream Out =11111011111100 000000101011...
+2.5 v
-2.5 v
A/D Convertor. 2 bits/sampleA/D Convertor. 2 bits/sample
A/D Convertor. 2 bits/sample.A/D Convertor. 2 bits/sample.
Input to the transmitter.Output at the receiver.
Receive 11? Output 3.75vReceive 10? Output 1.25vReceive 00? Output -1.25vReceive 01? Output -3.75vReduced Round-Off error exists.
+3.75 v
+1.25 v
-1.25 v
-3.75 v
Wired Telephone Local LoopWired Telephone Local Loop
WWNN = 3.5 KHz = 3.5 KHz
Low PassFilter
SamplerFs = 8 KHz
TwistedPair Cable
NonuniformQuantize256 levels
PCM Coder
8 bits/sample
64 Kbps
Telephone Local Loop: VoiceTelephone Local Loop: Voice
Decode256 levels
Hold1/8000 sec
64 Kbps
Low PassFilter
Analog Out
Compact DiskCompact Disk
WWNN = 20 KHz = 20 KHz
Low PassFilter
SamplerFs = 44.1 KHz
AudioSource
Quantize65,536 levels
Code16 bits/sample
705.6 Kbps
Compact DiskCompact Disk
Decode65,536 levels
Hold1/44,100 sec
705.6 Kbps
Low PassFilter
Analog Out
Audio (from NPR)Audio (from NPR)
"… before a joint session of Congress for "… before a joint session of Congress for his 2nd State of the Union speech, this is his 2nd State of the Union speech, this is actually the first…"actually the first…"
1/8th Second of Voice1/8th Second of Voice
1/8th Second of Voice1/8th Second of Voice
1/8th Second of Voice1/8th Second of Voice
Sampling & Quantizing ExamplesSampling & Quantizing Examples fs = 16 KHzfs = 16 KHz
4096 quantiles 4096 quantiles 256 quantiles (approximate phone quality)256 quantiles (approximate phone quality) 32 quantiles 32 quantiles 4 quantiles (generally 2 levels used!)4 quantiles (generally 2 levels used!)
4096 quantiles4096 quantiles fs = 16 KHzfs = 16 KHz fs = 8 KHz (some interference)fs = 8 KHz (some interference) fs = 2 KHzfs = 2 KHz fs = 1 KHzfs = 1 KHz