ECEN5533 Modern Communications Theory Lecture #79 September 2014 Dr. George Scheets n Read 5.6 – 5.9 n Scan Design Problem #1 n Problems 5.14 & 5.15 n Quiz #1 (Chapter 1) [4.5 < Uncorrected Scores < 18.5] u Remote DL: No later than 11 September u Reworked Quiz due 16 September (Live) n Exam #1 u Local: 18 September u Remote DL: No later 25 September

ECEN5533 Modern Communications Theory Lecture #811 September 2014 Dr. George Scheets n Problems 5.16 – 5.18, 5.21 n Quiz #1 (Chapter 1) u Remote DL: No later than 11 September u Reworked Quiz due 16 September (Live) n Exam #1 u Local: 18 September u Remote DL: No later 25 September n Design Problem #1 u Due 25 September (Live) u Not Later than 2 October (DL)

ECEN5533 Modern Commo Theory Lesson #9 16 September 2014 Dr. George Scheets n Read n Problems: 2.1, 2.7, 2.9, 2.11 n Quiz #1 (Chapter 1) u Reworked Quiz due 16 September (Live) u 1 week after return (DL) n Exam #1 (covers Chapter 1, 5, and Chapter 2 Sampling Theory) u Local: Next Time! u Remote DL: No later 25 September n Design Problem #1 u Due 25 September (Live) u Not Later than 2 October (DL) n Any graded HW is accepted late u Cost is -1 point per working day

Design #1: RoboCop RFP n Design an RF Public Safety Commo system for the city of Metropolis. u Info Sinks can be anywhere in city u Provide system analysis for worst case link. (0,0) (59,47) Info Source (51,39)

Design #1: RoboCop RFP n Configure Transmitter Site (1) u Where to locate? u Height of tower f(worst case distance) u Power Out u Uplink center frequency u Where be the electronics ? Info Source (51,39)

Design #1: RoboCop RFP n Path Loss is cubed not squared (4πd/λ) 3 n Antenna Gain n Two sectors n Hi Gain n Low Gain n Design for Worst Case G/Ls ratio. G Hi G Lo G Hi /L s1 G Lo /L s2

Design #1: RoboCop RFP n Configure Standard Receiver System u 21,200 units u Specify LNA Preamp Converts RF signal to IF or baseband u IC Amps Process RF or baseband, output baseband n All choices have $$$ impact u Many extra credit points available

Use a Spread Sheet!!! n Can use again (with mods) on Design 2 n Tie in costs to design choices u Can see how changes affect cost n Get a system (any system) that works u Output power > 1/4 watt & SNR > 32 dB u Anything over the minimum is Margin!!! F System delivers 1/2 w & 35 dB SNR? Increase Margin by 3 dB n Adjust parameters to reduce Costs u Get some of those extra credit points!

Grading n Real World RFP: u 1 team gets full credit u Everyone else gets a zero n Partial credit u Awarded on Quizzes & Tests u NOT AWARDED ON DESIGN PROJECTS! n Real world designs don't get partial credit u Either Work or They Don't n Double check your work!!! Use a spreadsheet

Testable Material Communication Theory LectureTextbook Homework Anything inside the circles is fair game... but overlapped areas are more likely.

To Maximize your score… n Budget your time n Tackle all the problems u Partial Credit is awarded n Show intermediate results n Obtain correct answer n Tests are full period, 4 pages, 100 points u Open book & notes u HW rework for < 1/2 of lost points

Low Noise Amps

System Temperature n k*T system *W n *G system = Noise power out of system n T system is referred to the front of an ideal system u SNR out = P r / k*T system *W n n A high gain device on the front end helps lower T system n Power Spectrum G X (f) u Key item for analyzing block diagrams

Tracking Noise Power 1/2 ∑ 10 8 ∑ Cable Amp 12.42( ) 24.01( ) 36.43( ) 18.22( ) 96.29( ) 114.5( ) 114.5(10 -7 ) Output SNR = dB

Tracking Noise Power 10 8 ∑ 1/2 ∑ Amp Cable 12.42( ) 96.29( ) 108.7( ) 108.7(10 -7 ) 24.01( ) 108.7(10 -7 ) 54.35(10 -7 ) Output SNR = dB

Multipath

Multipath (20 m antenna height)

Multipath (10 m antenna height)

Urban Ray Tracing Image Source: IEEE Communications Magazine

Effect of Ionosphere (f < 35 MHz) Line of Sight & Ground Wave

Ionosphere Multipath

"Cue Ball" Earth

Using Earth Contours

RF Link Equations... n are accurate for Line of Sight Far Field No Multipath n give a useful average for Line of Sight Far Field Multipath

RF Link Equations... n can give ball park results for No Line of Sight Far Field Multipath if path loss is increased n Radio Horizon is 4/3 Optical Horizon

Analog to Digital Conversion) Part 1... Sampler analog input x(t) discrete time output x s (t) transmitter side

Sampling n Ideal Sampler u Minimum Sampling Frequency > 2 * W abs n Real World Realizable Sampler u Unable to build brick wall filters u Must sample about 10% faster than 2*W abs n Output is discrete time u But contains info to reconstruct original n Voltage is still Continuous u Infinite Precision → Infinite # of bits/sample

Analog to Digital Conversion) Sampler analog input x(t) discrete time signal x s (t) transmitter side Source Coder bit stream

Analog to Digital Conversion Analog Low Pass Filter estimate of analog input discrete time signal estimate receiver side Source Decoder bit stream

Video Undersampling n Typical TV Video has 30 frames/second u Frame = Still Picture n Car Commercial Wheel spokes moving the wrong way Wheel spokes stationary, car moving → fs not high enough

24 bit color 2 24 = M colors

256 Colors

16 Colors

Example) Coding a Microphone Output time (sec) m(t) volts (air pressure) Energy from about ,500 Hz.

A/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 Convertor time (sec) m(t) volts (air pressure) Step #2) Convert the sample voltages to a bit stream. Suppose m(t1) = 3.62 volts v t1

A/D Converter n Simplest technique is PCM u Wired Telephone System u Audio Compact Disks n Pulse Code Modulation Round off to N possible voltages Equal length Code word is assigned to each voltage N Typically a Power of 2 Log 2 N bits per code word

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 v, output a 1 t1 Bit Stream Out =

A/D Convertor. 1 bit/sample. Example) N = 2. Assign 0 or 1 to voltage. Far side gets (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. Input to the transmitter. Output at the receiver. Considerable Round-Off error exists v -2.5 v

time (sec) Example) N = 4. Assign 00, 01, 10 or < Voltage < 5, Assign 11 0 < Voltage < 2.5, Assign < Voltage < 0, Assign < Voltage < -2.5, Assign v, Assign 11 t1 Bit Stream Out = v -2.5 v A/D Convertor. 2 bits/sample

A/D Convertor. 2 bits/sample. Input to the transmitter. Output at the receiver. Receive 11? Output 3.75v Receive 10? Output 1.25v Receive 00? Output -1.25v Receive 01? Output -3.75v Reduced Round-Off error exists v v v v

Wired Telephone Local Loop n W N = 3.5 KHz Low Pass Filter Sampler F s = 8 KHz Twisted Pair Cable Nonuniform Quantize 256 levels PCM Coder 8 bits/sample 64 Kbps

Telephone Local Loop: Voice Decode 256 levels Hold 1/8000 sec 64 Kbps Low Pass Filter Analog Out

Compact Disk n W N = 20 KHz Low Pass Filter Sampler F s = 44.1 KHz Audio Source Quantize 65,536 levels Code 16 bits/sample Kbps

Compact Disk Decode 65,536 levels Hold 1/44,100 sec Kbps Low Pass Filter Analog Out

Audio (from NPR) n "… before a joint session of Congress for his 2nd State of the Union speech, this is actually the first…"

1/8th Second of Voice

Sampling & Quantizing Examples  fs = 16 KHz  4096 quantiles  256 quantiles (approximate phone quality)  32 quantiles  4 quantiles (generally 2 levels used!)  4096 quantiles  fs = 16 KHz  fs = 8 KHz (some interference)  fs = 2 KHz  fs = 1 KHz