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Term Paper Reminders

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Term Paper Reminders

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  1. ECEN5553 Telecom SystemsDr. George ScheetsWeek #12Read [25] "Riding the Data Tsunami in the Cloud"[26] "The Next Challenge for Cellular Networks: Backhaul"[27a] "How BYOD Has Changed the IT Landscape"[27b] :The Bring-Your-Own-Device Dilemma"Exam 2 Results to date (90 points max) Hi = 88.8, Low = 58.8, Ave. = 77.92, σ = 8.27Term Paper 8 November (Local) 15 November (Remote DL)

  2. Term Paper Reminders • Statement not "Common Knowledge"? • Cite in Main Body of the Paper • Don't plagiarize! • Copied word for word? Cite it & put in "quotes". • Don't cut & paste, and then change a few words. • Probe Further • Don't Get too Bubbly • Watch out for dated references • Good Score • Good Read, Factually Correct, Follows Outline

  3. Paper Delivery • No Paper Copies • Submit Electronically via EMail or D2L... • Word Perfect • Word • Writer (Open Office) .odf files • PDF

  4. Web Citations • Provide sufficient info so I can pull up your article!! Use common sense. • http://web site/directory/filename is best(include author, title, year if available) • Don't just put http://web site • author, title, journal, year (found via Search Engine XYZ) is fine • Beware the long URL generated by search engines • Sometimes they work. Sometimes they don't.

  5. Example) SSD 3 bit code words • Transmit each bit thrice, P(Code Bit Error) = .1 • Legal Transmitted code words; 000, 111 • Possible received code words000, 111 (appears legal, 0 or 3 bits in error) 001, 010, 100 (clearly illegal, 1 or 2 bits in error)011, 101, 110 (clearly illegal, 1 or 2 bits in error)P(No bits in error) = .9*.9*.9 = .729P(One bit in error) = 3*.92*.1 = .243P(Two bits in error) = 3*.9*.12 = .027P(Three bits in error) = .1*.1*.1 = .001 • Decoder takes 3 bits at a time & outputs 1 bit. Majority Rules.72.9% + 24.3% = 97.2% of time correct bit is output .1% + 2.7% = 2.8% of time incorrect bit is output • Improved performance @ 3x the required bit rate

  6. SSD 3:1 FEC Source Coder: Input = 1 bit. Output = Input + two parity bits. Source Channel Coder data bits R bps Symbol rate transmitted must triple compared to no FEC case, or 8-Ary signaling must be used. code bits 3R bps code bits data bits Source Decoder: Looks at blocks of 3 bits. Outputs 1 bit. Symbol Detector: Single sample Channel P(data bit error) = .028 P(code bit error) = .1 3:1 FEC offers superior performance than simpler no FEC code system.

  7. Example) MFD No Coding • Probability of a Bit Error will improve over that of Single Sample Detector to, say, P(Bit Error) = .02 • No Coding: Transmit each Data Bit Once • Legal Transmitted data‘words’; 0, 1 • Possible received data words0, 1 (legal or 1 bit in error, no way to tell)P(Data Bit OK) = .98P(Data Bit in error) = .02

  8. Matched Filter Detector & No coding: Block Diagram • Matched Filter shows reduced bit errors compared to SSD • Improvement decreases as symbol rate increases Source Channel Coder Symbol Detector: Matched Filter Channel P(Bit Error) = .02

  9. Example) MFD 2 bit code words • Suppose you transmit each bit twice, smaller bit width will cause P(Code Bit Error) to increase to, say 0.03 • Legal Transmitted code words; 00, 11 • Possible received code words00, 11 (appears legal, 0 or 2 bits in error) 01, 10 (clearly illegal, 1 bit in error)P(No code bits in error) = .97*.97 = .9409P(One code bit in error) = 2*.97*.03 = .0582P(Both code bits in error) = .03*.03 = .0009 • Decoder takes 2 code bits at a time and outputs 1 data bitIf illegal code word received, it can guess 0 or 1.94.09% + 5.82%(1/2) = 97% of time correct bit output .09% + 5.82%(1/2) = 3% of time the incorrect bit is output • FEC makes it worse: 3% data bit error vs 2% No Coding

  10. Typical FEC Performance Coded Plot changes as type of symbol, type of detector, and type of FEC coder change. P(BE) Uncoded Plot changes as type of symbol, and type of detector change. Last example is operating here. SNR There generally always is a cross-over point. The max possible P(BE) = 1/2.

  11. MFD 2:1 FEC 2R code bps Source Coder: Input = 1 bit. Output = Input + Parity bit. Source Channel Coder R data bps R app. bps 2R code bps Source Decoder: Looks at blocks of 2 bits. Outputs 1 bit. Symbol Detector: Matched Filter Channel P(data bit error) = .03 P(code bit error) = .03

  12. Example) MFD 3 bit code words • Transmit each bit thrice, P(Bit Error) again increases to, say 0.04, due to further increase in the bit rate. • Legal Transmitted code words; 000, 111 • Possible received code words000, 111 (appears legal, 0 or 3 bits in error) 001, 010, 100 (clearly illegal, 1 or 2 code bits in error)011, 101, 110 (clearly illegal, 1 or 2 code bits in error)P(No code bits in error) = .96*.96*.96 = .884736P(One code bit in error) = 3*.962*.04 = .110592P(Two code bits in error) = 3*.96*.042 = .004608P(Three code bits in error) = .04*.04*.04 = .000064 • Decoder takes 3 bits at a time & outputs 1 bit. Majority Rules.88.4736% + 11.0592% = 99.5328% of time correct bit is output .0064% + .4608% = 0.4672% of time incorrect bit is output • FEC makes Data BER better (.5% vs 2%) @ thrice the bit rate

  13. MFD 3:1 FEC 3R code bps Source Coder: Input = 1 bit. Output = Input + two parity bits. Source Channel Coder R application bps R app. bps 3R code bps Source Decoder: Looks at blocks of 3 bits. Outputs 1 bit. Symbol Detector: Matched Filter Channel P(app. bit error) = .005 P(code bit error) = .04

  14. Typical FEC Performance FEC allows target P(BE) to be reached with lower received SNR, but a higher bit rate must be transmitted. Used a lot in power limited environments. P(BE) Coded Uncoded Received SNR Different FEC codes will have different curves!

  15. Very Large Array Parabolics Directional antennas. Larger size → narrower beam. Narrower beam → energy more focused (XMTR) Narrower beam → better at picking up weak signal (RCVR) image source: Wikipedia

  16. Arecibo Radio Telescope (305 m) Direct TV Antenna (1/2 m)

  17. Omni-Directional Antenna Array Belkin Wireless Pre-N Router F5D8230-4 Steerable beams. source: http://www.pcmag.com/article2/0,1759,1822020,00.asp

  18. Two Omni Array Example λ/2 fc = 300 MHz λ = 1 meter Same signal fed to both antennas. Beam shoots out both sides at 90 degree angle. (Far side not shown.) Directivity Strength

  19. Two Omni Array Example λ/2 fc = 300 MHz λ = 1 meter Signal to right antenna delayed by 333.3 picosecond ( = 10% wavelength) with respect to right antenna. Directivity Strength

  20. Two Omni Array Example λ/2 fc = 300 MHz λ = 1 meter Signal to left antenna delayed by 333.3 picosecond ( = 10% wavelength) with respect to right antenna. Directivity Strength

  21. Two Omni Array Example λ/2 fc = 300 MHz λ = 1 meter Signal to left antenna delayed by 833.3 picosecond ( = 25% wavelength) with respect to right antenna. Directivity Strength

  22. Two Omni Array Example λ/2 fc = 300 MHz λ = 1 meter Signal to left antenna delayed by 1 2/3 nanosecond ( = 50% wavelength) with respect to right antenna. Directivity Strength

  23. I/O LAN Antenna Combinations • SISO • Common Today • SIMO, MISO, & MIMO • Starting to see use on newest wireless LAN's • SIMO & MISOCan help cancel effects of multi-path • MIMOCan provide spatial diversity • Increases amount of usable RF bandwidth

  24. Bit Error Rate Unsatisfactory? System designer has several options: • Use FEC codes • Increase received signal power • Crank up transmitter power out • Use directional antennas • Use more effective modulation technique • Slow down the transmitted symbol rate • Use less noisy receiver electronics

  25. Voyager II Deep Space Probe • Used all of previous techniques on downlink: • 2:1 FEC Coding (different code than in previous examples) • Increasingly sophisticated earth receive antennas • Binary PSK signaling • Reduced bit rates • Cryogenically cooled receiver electronics • Flight history • Launch , August 1977 • Jupiter fly-by, July 1979, Message bit rate: 115.2 Kbps • Saturn fly-by, August 1981, Message bit rate: 44 Kbps • Uranus fly-by, January 1986, Message bit rate: 29.9 Kbps • Neptune fly-by, August 1989, Message bit rate: 21.6 Kbps • Now well past Pluto. NASA is still in contact.

  26. Pre-Cellular Mobile Telephony source: Telecommunications by Warren Hioki, 1st Edition

  27. Cellular Telephone System ISP source: Telecommunications by Warren Hioki, 1st Edition

  28. Cellular Telephony Advantages: • Frequency Reuse • Reduced Transmitter Power Out • Reduced Multipath Problems • Reduced brain damage? • Subdividing Cells increases System Capacity • More Reliable due to cell overlap

  29. Cellular Telephony Disadvantages: • More complex • More installation hassles • BS to MTSO link & switching requirements can get out of hand

  30. 1987 Mobile Phone source: September 1987 Electronic Design Magazine

  31. One Big Cell 30 Channels could support 30 users

  32. Seven Smaller Cells Set #2 10 Channels Set #1 10 Channels Can Support 70 Users with same Channel set. Set #3 10 Channels

  33. Mobile Traffic Source: "The Great Spectrum Famine", IEEE Spectrum Magazine, October 2010.

  34. London, 1995

  35. Hidden Cell Towers sources: businessweek.com mobilitydigest.com

  36. Cellular Telephony - OperationPower Up & Intermittently Thereafter • Mobile tunes to strongest control channel • Mobile communicates with BS/MTSO • Local MTSO notes in database mobile is active & which cell it's in • If mobile is roaming, Home MTSO is notified, typically via SS7 or SIP Signaling

  37. Cellular Telephony - OperationMobile to Wired call • Mobile transmits # to BS/MTSO • Uses Control Channel • Unused voice RF channel is assigned • Mobile tunes to assigned channels • BS & MTSO coordinate Backhaul • MTSO places call via CO to wired unit • Could be via PSTN or VoIP

  38. Cellular Telephony - Operation Wired to Mobile call • Signaling info shipped to home MTSO • Home MTSO checks database • Mobile in home area? Mobile is paged • Mobile not in home area? Signaling info is forwarded to local MTSO Local MTSO database indicates Mobile's cellMobile is paged & tunes to assigned RF channel • End-to-End Voice channel is set up • BS & MTSO coordinate Backhaul • MTSO & CO coordinate Long Haul

  39. Cellular Telephony - Operation • HandoffMTSO/BS/Mobile decides signal getting too weakAdjacent cells are polledUnused voice RF channels in the new cell is assignedMobile tunes to assigned channelMTSO reroutes traffic: Old BS  MTSO to New BS  MTSOMay cause glitch up to about 100 msec

  40. RIP Advanced Mobile Phone System (AMPS) • 1st Generation U.S. Cellular • Analog FDMA • 30 KHz FM channels • # of subscribers peaked in 1999 • February 18, 2008 • FCC no longer required carriers to support • Should now be called OMPS

  41. Different channels use some of the frequency all of the time. FDMFDMA frequency 1 2 3 4 Cell 1Cell 2 AMPS time

  42. Combo of TDM & FDM(GSM) TDMA/FDMA frequency 10 1 4 7 Cell 1Cell 2 11 2 5 8 12 3 6 9 time 10 1 4 7 etc.

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