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ECEN4533 Data Communications Lecture #33 1 April 2013 Dr. George Scheets

ECEN4533 Data Communications Lecture #33 1 April 2013 Dr. George Scheets. Read VoIP Tutorial Web 25 & 26 Exam #2, 8 April Corrected Quizzes due 10 April. ECEN4533 Data Communications Lecture #34 3 April 2013 Dr. George Scheets. Problems: Exam #2 2010 & (1st Half) 2011

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ECEN4533 Data Communications Lecture #33 1 April 2013 Dr. George Scheets

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  1. ECEN4533 Data CommunicationsLecture #33 1 April 2013Dr. George Scheets • Read VoIP Tutorial • Web 25 & 26 • Exam #2, 8 April • Corrected Quizzes due 10 April

  2. ECEN4533 Data CommunicationsLecture #34 3 April 2013Dr. George Scheets • Problems: Exam #2 2010 & (1st Half) 2011 • Exam #2, 8 April • Probability & Queuing (including) up to RF (excluding) • Corrected Designs due • 5 April (Live) • 1 Week after return (DL) • Corrected Quizzes due 10 April??

  3. ECEN4533 Data CommunicationsLecture #35 5 April 2013Dr. George Scheets • Problems: Exam #2 2012 & 2011 (2nd Half) • Exam #2: 8 April (Live), < 15 April (DL) • Probability & Queuing (including) up to RF (excluding) • Corrected Designs due • Today (Live) • 1 week after return (DL) • Corrected Quizzes due • 10 April (Live) • 1 week after return (DL)

  4. 2013 OSU ECE Spring Banquet Sponsored in part by: • Hosted by Student Branch of IEEE • Wednesday, 17 April, at Meditations • Doors open at 5:30 pm, meal at 6:00 pm • Cash Bar • Sign up in ES202 to reserve your seat(s) • $5 a head (for a $16 meal!) • if pay in advance and resume submittedto OSUIEEEresume@gmail.com< 5:00 pm, 15 April. Otherwise $8. • Speaker: Dr. Matt PerryDirector, SiArch • Dress is Business Casual • Many door prizes available!+10 points extra credit • All are invited!

  5. MegaMoron Tsega Debele $17,057.31 QoS Internet

  6. Voice Calls: Trunk Capacity LimitG.711 Example

  7. Voice Calls: M2E Delay LimitG.711 Example

  8. Best choice here 475 frames/packet (60 msec packet assembly delay) Will support 21 calls Supportable VoIP Calls

  9. Example VoIP Network OC-3 Access 2 1 Voice Switch/ Gateway Routers B Voice Switch/ Gateway 3 4 OC-12 VoIP Backbone A 20 msec end-to-end propagation delay G.729 Coders

  10. Voice Calls Possible Over an OC-12 Trunk(G.729 Fixed Rate Coder) 40000 100 msec 150 msec 30000 Trunk Voice calls supportable 20000 POTS can support 8,192 calls on an OC-12 10000 0 1 2 3 4 5 6 7 8 9 10 11 Number of Frames per Packet

  11. . 5 8 10 - 5 ´ 6.501 10 Received Power . 5 6 10 P i . 5 4 10 pr1 i Antenna . 5 2 10 Height: 20 meters - 7 ´ 1.791 10 0 0 20 40 60 80 100 120 15 dist1 115 i Multipath: One Reflection

  12. 10Base5 & 10Base2 (Obsolete)Used CSMA/CD (Polite Conversation) Coax Cable PC PC Printer Logical & Physical Bus All nodes monitor traffic Nodes share 10 Mbps 10Base2 "T" connection 10Base5 "Vampire Tap" Images from Wikipedia

  13. 802.3 Flow Chart (NIC) No Packet to Send? Drop Packet. Notify Higher Layer Yes Yes No Set Collision Couter = 0 16th Collision? Back-Off Yes Traffic on Network? Bump Collision Counter by +1 No Yes Send Packet Collision? Jam No

  14. 802.11 Flow Chart (Simplified) No Packet to Send? Binary Exponential Back-off Used (Similar to 802.3) Min Wait: 0 Max Wait: 51.2 msec No Media Quiet? Back-off Yes No Media Quiet? Quiet for IFS? No Yes Yes Transmit ACK received? No Yes

  15. Fall 2002 Final • 'Average' based on 1 test chosen at random126.00 out of 150 • One point average X1 • 'Average' based on 10 tests chosen randomly109.44 out of 150 • Ten point average X10 • Actual Midterm Average106.85 out of 150

  16. Wireless Design Options • Adjust Transmitter Power Out • Reduce System Noise • Signal off antenna very small • Thermal Noise off antenna ≈ 80*10-15 watts • 20 MHz Bandwidth • Stuck with this • Electronic Noise can be >> • Can be reduced with $$ • Slow down XMTR symbol rate (= 1/T) • Allows more accurate average in T seconds

  17. Averages • N point average? S.I. points?σ2average = σ2points/N • N point average? Self-Similar points? σ2average = σ2points/N2(1-H) • If Statistically Independent, H = 1/2

  18. 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

  19. Satcom & Flat Panel Antenna Arrays USS Lake Champlain: Aegis Guided Missile Cruiser image source: wikipedia

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

  21. 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

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

  23. 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

  24. 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

  25. 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

  26. 10BaseT & Shared Hub PC Twisted Pair Cabling PC Hub PC PC Logical Bus & Physical Star Shared hub (OSI Level 1) copies input bits to all outputs. All nodes monitor traffic.

  27. 10BaseT & Switched Hub PC PC Switched Hub PC PC Logical Bus & Physical Star Switched Hub (OSI Level 1 & 2) copies packet to proper output. Only the destination monitors traffic.

  28. 10BaseT & Switched Hub PC PC Switched Hub PC PC Logical Bus & Physical Star This system can move up to 20 Mbps

  29. 802.11 & Omni Antenna PC PC PC PC Only 1 node can transmit at a time. If 2nd node talks, received signal will be garbled.

  30. 802.11 & MIMO Antennas PC PC PC PC Nodes could transmit on the same frequency, at the same time, focusing energy where it needs to go.

  31. Digital Communication Systemwith Analog Source Source Outputs continuous waveform. Source Coder Converts samples to a bit stream. May compress. Sampler Samples waveform. Low Pass Filter Smoothes replica so it more closely resembles original source. Source Decoder Converts bit stream to replica of original source. Digital Communication System (see next slide)

  32. Layer 2→6 IP, TCP, etc. Digital Communication System Source Data, Digitized audio or video. Outputs bits. Modulator Converts bits to a symbol suitable for channel. Layer 6→2 IP, TCP, etc. FEC Adds extra parity bits. Optional FEC Decoder Examines blocks of bits. If possible, corrects or detects bit errors. Outputs estimate of bit stream. Symbol Detector Examines received symbol & outputs 1 (binary) or more (M-Ary) bits. Channel Attenuates, distorts, & adds noise to symbols.

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