1. ECEN4533 Data Communications Lecture #331 April 2013 Dr. George Scheets n Read VoIP Tutorial n Web 25 & 26 n Exam #2, 8 April n Corrected Quizzes due 10 April

2. ECEN4533 Data Communications Lecture #343 April 2013 Dr. George Scheets n Problems: Exam #2 2010 & (1st Half) 2011 n Exam #2, 8 April u Probability & Queuing (including) up to RF (excluding) n Corrected Designs due u 5 April (Live) u 1 Week after return (DL) n Corrected Quizzes due 10 April??

3. ECEN4533 Data Communications Lecture #355 April 2013 Dr. George Scheets n Problems: Exam #2 2012 & 2011 (2nd Half) n Exam #2: 8 April (Live), < 15 April (DL) u Probability & Queuing (including) up to RF (excluding) n Corrected Designs due u Today (Live) u 1 week after return (DL) n Corrected Quizzes due u 10 April (Live) u 1 week after return (DL)

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

5. Tsega Debele $17,057.31 QoS Internet

6. Voice Calls: Trunk Capacity Limit G.711 Example

7. Voice Calls: M2E Delay Limit G.711 Example

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

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

10. Voice Calls Possible Over an OC-12 Trunk (G.729 Fixed Rate Coder) Number of Frames per Packet Trunk Voice calls supportable 0 10000 20000 30000 40000 1234567891011 100 msec 150 msec POTS can support 8,192 calls on an OC-12

11. Multipath: One Reflection

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

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

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

15. Fall 2002 Final n 'Average' based on 1 test chosen at random 126.00 out of 150 u One point average X 1 n 'Average' based on 10 tests chosen randomly 109.44 out of 150 u Ten point average X 10 n Actual Midterm Average 106.85 out of 150

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

17. Averages n N point average? S.I. points? σ 2 average = σ 2 points /N n N point average? Self-Similar points? σ 2 average = σ 2 points /N 2(1-H) u If Statistically Independent, H = 1/2

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

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

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

21. Two Omni Array Example 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.) λ/2 Directivity Strength

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

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

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

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

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

27. 10BaseT & Switched Hub PC Switched Hub 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 Switched Hub Logical Bus & Physical Star This system can move up to 20 Mbps

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

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

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

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