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ECEN5533 Modern Commo Theory Dr. George Scheets Lesson #23 12 November 2013

ECEN5533 Modern Commo Theory Dr. George Scheets Lesson #23 12 November 2013. Read Section 6.4 – 6.5 Problems: 9.2, 9.4, 9.7, 6.2, 6.3 Reworked Quiz #2 due various dates Reworked Exam #2 due various dates Exam # 2 < 14 Nov (remote DL) Design #2, 14 Nov (local), < 21 Nov (remote DL).

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ECEN5533 Modern Commo Theory Dr. George Scheets Lesson #23 12 November 2013

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  1. ECEN5533 Modern Commo TheoryDr. George Scheets Lesson #23 12 November 2013 • Read Section 6.4 – 6.5 • Problems: 9.2, 9.4, 9.7, 6.2, 6.3 • Reworked Quiz #2 due various dates • Reworked Exam #2 due various dates • Exam #2 < 14 Nov (remote DL) • Design #2, 14 Nov (local), < 21 Nov (remote DL)

  2. ECEN5533 Modern Commo TheoryDr. George Scheets Lesson #24 14 November 2013 • Read Section 6.6 - 6.9, 7.1 • Problems: 5,8, 6.4, 6.5, 9.8, 9.9 • Reworked Quiz #2 due various dates • Reworked Exam #2 due various dates • Design #2, 14 Nov (local), < 21 Nov (remote DL)

  3. ECEN5533 Modern Commo TheoryDr. George Scheets Lesson #25 19 November 2013 • Read Section 7.2 - 7.3 • Problems: 6.9, 6.11, 6.13, 7.1, 7.3 • Reworked Exam #2 due various dates • Design #2due < 21 Nov (remote DL) • Final Exam(Local) Thursday, 12 December, 0800-0950(Remote) on or before 19 December

  4. ECEN5533 Modern Commo TheoryDr. George Scheets Lesson #26 21 November 2013 • Read Section 7.4 - 7.6, 12.1 • Problems 7.7, 7.10, 7.12, 7.16, 12.3 • Reworked Exam #2 due various dates • Design #2 due < 21 Nov (remote DL) • Late Fee = -1 point per working day • Final Exam(Local) Thursday, 12 December, 0800-0950(Remote) on or before 19 December

  5. ECEN5533 Modern Commo TheoryDr. George Scheets Lesson #27 26 November 2013 • Read Section 12.2 - 12.4 • Problems 12.4, 12.9-12.11, 12.21 • Reworked Exam #2 due various dates • Reworked Design #2 due various dates • Comprehensive Final Exam (No Rework) • (Local) Thursday, 12 December, 0800-0950 • (Remote) on or before 19 December

  6. ECEN5533 Modern Commo TheoryDr. George Scheets Lesson #28 3 December 2013 • Radar Problems (available online) • Reworked Design #2 due various dates • Comprehensive Final Exam (No Rework) • (Local) Thursday, 12 December, 0800-0950 • (Remote) on or before 19 December

  7. ECEN5533 Modern Commo TheoryDr. George Scheets Lesson #29 5 December 2013 • Reworked Design #2 due various dates • Comprehensive Final Exam (No Rework) • (Local) Thursday, 12 December, 0800-0950 • (Remote) on or before 19 December

  8. Point Spreads of Completed Stuff • Quiz #1 (20 points)Hi = 19.4, Low = 7.3, Ave = 14.35, σ = 3.64 • Quiz #2 (20 points)Hi = 20, Low = 10.6, Ave = 16.17, σ = 3.20 • Exam #1 (100 points)Hi = 96, Low = 69, Ave = 83.60, σ = 9.78A > 90, B > 76, C > 66, D > 56 • Exam #2 (100 points)Hi = 90, Low = 60, Ave = 73.80, σ = 10.46A > 87, B > 72, C > 62, D >52 • Design #1 (70 points)Hi = 69, Low = 46, Ave = 59.30, σ = 6.88

  9. Design #2: Digital Satellite RFP Lowest Working Bid$74.10 MillionStephen Swanson Promoted to Senior Engineer II at MegaMoron 16FSK @ 7.9 GHz (↑ in BW $, ↓ BER) 35-1 Compression, No FEC 2 orbital paths, 3 satellites/path, 7246 miles 12x12 RCVR & 2x2 XMTR sat antenna 9 dB margin Moved $$ to satellites: Earth units $376.85 MegaMoron

  10. BER for Coherent Orthogonal M-FSK • As M = 2k ↑, BER ↓ • BW required ↑ • For M-ASK, M-PSK or M-QAM • As M = 2k ↑, BER ↑ • BW stays same… • If Baud rate unchanged Image Source: Bernard Sklar's Digital Communcations

  11. Anything in Circles is Fair Gameon Final Exam S Read HW Notes

  12. Bit Error Rate Unsatisfactory? • System designer has several options: • Use FEC codes • Increase received signal power • Use more effective modulation technique • Best for baseband: + & - square pulses • Best for RFBinary system? PSKM-Ary system? QPSK or QAM • Slow down the transmitted message symbol rate • Decrease receiver Tsystem

  13. Rate 1/2 Turbo Coder • uk (data) & vk (parity bits) are transmitted to far side • vk = v1k 1/2 of the time & v2k other half Source: Figure 8.26 from Sklar's Digital Communications

  14. Rate 1/2 Turbo Decoder ← Matched Filter • xk (corrupted data) & yk (corrupted parity bits) • yk = y1k 1/2 of the time & y2k other half ← Matched Filter Source: Figure 8.27 from Sklar's Digital Communications

  15. Rate 1/2 Turbo Coding Performance • P(data bit error) = 0.00001 when Eb/No = 0.2 dB & 18 reps • P(bit error) = 0.07395 for BPSK when Eb/No = 0.2 dB Source: Figure 8.28 from Sklar's Digital Communications

  16. Performance Improved Performance • Uncoded BPSK • Hard coded Block or Convolutional BPSK • Soft coded Convolutional BPSK • 2 dB increase in effective Eb/No Compared to Hard Convolutional Decoding • Turbo Coded BPSK • Big time increase in effective Eb/No • Can get you close to Shannon Limit • All of above require an increase in the bit rate • Need more bandwidth, or go M-Ary • Trellis Coded Modulation • 3 db – 6 dB increase in effective Eb/No • Doesn't require an increase in bit rate

  17. Spread Spectrum • Direct Sequence • Frequency Hopping • Advantages: • Interference Suppression • Privacy • Multipath Effects are Reduced • Code Division Multiple Access • Disadvantages: • Hardware More Complex

  18. DSSS - Transmit Side +1 Traffic (9 Kbps) time -1 Spreading Signal 27 Kcps +1 +1 +1 time -1 -1 -1 +1 +1 +1 +1 time Transmitted Signal 27 Kcps -1 -1

  19. Wireless X 27 Kcps Square Pulses RF Transmitter BPSK output 27 Kcps 90% of power in 54 KHz BW centered at fc Hertz cos(2πfct) RCVR Front End BPSK input 27 Kcps + noise Low Pass Filter 27 Kcps Square Pulses + filtered noise X cos(2πfct)

  20. +1 +1 +1 +1 time Received Signal 27 Kcps -1 -1 Despreading Signal 27 Kcps +1 +1 +1 time -1 -1 -1 Recovered Traffic 9 Kbps +1 time DSSS-Receiver -1

  21. DSSS Receiver • If the proper source is transmitting... • ...and the receiver has the correct despread sequence... • ...and the sequence is properly synchronized... • ...the original message is recovered.

  22. DSSS Receiver • If another source is transmitting... • ...the receiver will have the wrong despread sequence... • ...and the output will be garbage.

  23. +1 +1 +1 -1 -1 Received Signal #2 27 Kcps +1 +1 +1 time +1 -1 Despreading Signal 27 Kcps +1 +1 +1 time DSSS-Receiver -1 -1 -1 Recovered Garbage from 2nd signal +1 +1 time

  24. +1 +1 -1 -1 Recovered Garbage at 2nd receiver +1 +1 time +1 +1 Receiver Matched Filter Detector time Message Output is a random sequence of 0’s & 1’s

  25. DSSS Receiver • If both sources are transmitting... • ...the bit detector will be fed the sum of the results.

  26. +2 -2 +1 +2 +1 -1 -1 +1 Recovered Traffic 9 Kbps time -1 Recovered Garbage from 2nd signal +1 +1 time Input to Matched Filter Detector (sum) time DSSS-Receiver

  27. +2 -2 +2 Input to Matched Filter Detector (sum) time TBit Receiver Matched Filter Detector Output +1 time -1 Additional signals transmitting at the same time increase the apparent noise seen by our system. Message BER will increase.

  28. Different channels use some of the bandwidth all of the time. FDM FDMAWDM frequency 1 2 3 4 5 time

  29. Different channels use all of the bandwidth some of the time. Predictable time assignments. TDMTDMA frequency 1 2 3 time 1 etc.

  30. Different channels use all of the bandwidth all of the time. CDMA frequency Channels use different codes. Other channels cause noise-like interference. time

  31. CDMA: 3D View frequency code #3 code #2 code #1 time

  32. CDMA vs FDMA • Example) Given 10 MHz Channel & Coding Gain of 1,000 • CDMA will support 75 users • FDMA will support 900 users • All things being equal...Power Out, Path Loss, Antenna Gains, etc. • In real world, all things aren't always equal

  33. CDMA vs FDMA (or TDMA) • Narrowband Noise • May knock out some FDMA or TDMA channels • Severe Multi-path Environment • May knock out some FDMA channels • Easier to add users • Transmit with different code (CDMA) • Must find empty time slot or frequency band • Easier to use Variable Rate Coder • Voice Coder with Silence Suppression • Doubles potential capacity

  34. Radar Antenna XMTR Switch RCVR Same antenna normally used. Either Transmitter or Receiver connected at any time.

  35. F-15 Eagle RCS ≈ Barn Door?

  36. F-117 Nighthawk RCS ≈ Hummingbird = 0.025 m2?

  37. B-2 Spirit RCS ≈ 0.1 m2?

  38. Voyager IIhttp://voyager.jpl.nasa.gov/index.html • Launch • August 1977 • Jupiter fly-by • July 1979 • Saturn fly-by • August 1981 • Uranus fly-by • January 1986 • Neptune fly-by • August 1989 • 15.0 Billion Km • 100.1 AU • November 2012 Source: JPL source: http://heavens-above.com

  39. VoyagerSpacecraft source: September 1990 IEEE Communications Magazine

  40. NASA Deep Space Network70 m diameter parabolic source: http://deepspace.jpl.nasa.gov

  41. Voyager FEC Coding source: Science, Summer 1990

  42. NO CODE CODING BER Performance at Jupiter Target BER: Imaging 5(10-3) Non-Imaging: 5(10-5) Command: 1(10-5) source: Science, Summer 1990

  43. CODING Same System Configuration as at Jupiter CODING Slowed bit rate compared to Jupiter BER Performance at Saturn Target BER: Imaging 5(10-3) Non-Imaging: 5(10-5) Command: 1(10-5) source: Science, Summer 1990

  44. CODING Reduced R Increased Aer Decreased Tsys compared to Saturn BER Performance at Uranus CODING Same System Configuration as at Saturn Target BER: Imaging 5(10-3) Non-Imaging: 5(10-5) Command: 1(10-5) source: Science, Summer 1990

  45. Signal * Wideband Noise

  46. CODING Same System Configuration as at Uranus CODING Reduced R Increased Aer Rebuilt antennas Additional coupling BER Performance at Neptune Target BER: Imaging 5(10-3) Non-Imaging: 5(10-5) Command: 1(10-5) source: Science, Summer 1990

  47. NRAO's Very Large Array image source: http://www.vla.nrao.edu/

  48. MIMO • Used in latest Cell & Wireless LAN protocols • Potential Benefits • Steerable Beams • Increased antenna gain • Spatial Multiplexing • Transmit several signals over (ideally) independent paths • Increase usable BW • Spatial Diversity • Several Versions of XMTR signal received • Improves BER

  49. MIMO antenna Belkin Wireless Pre-N Router F5D8230-4 source: http://www.pcmag.com/article2/0,1759,1822020,00.asp

  50. MIMO Example λ/2 fc = 300 MHz λ = 1 meter Same signal fed to both antennas. Beam shoots out both sides at 90 degree angle. Directivity Strength

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