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OFDMA performance in 11ax

OFDMA performance in 11ax. Date: 2016-07-25. Authors:. Introduction. From September 2015 meeting, we have addressed OFDMA performance using PHY/MAC integrated simulator [1]~[7] DL only, UL only DL and UL mixed Single BSS, OBSS(Residential) MU-RTS/CTS

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OFDMA performance in 11ax

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  1. OFDMA performance in 11ax Date: 2016-07-25 Authors: Suhwook Kim, LG Electronics

  2. Introduction • From September 2015 meeting, we have addressed OFDMA performance using PHY/MAC integrated simulator [1]~[7] • DL only, UL only • DL and UL mixed • Single BSS, OBSS(Residential) • MU-RTS/CTS • Full buffer traffic, low rate traffic Suhwook Kim, LG Electronics

  3. Simulator update • We had used only UDP (CBR) traffic in our simulator • UDP is very simple • Full buffer traffic model is widely used to evaluate communication system simulation • There are, however, so many TCP traffic in real world • Performance on TCP traffic may be different from UDP traffic because of its characteristics • So, we have implemented TCP model in our simulator • TCP traffic defined in our EMD[8] • TCP operation (TCP-Reno) Suhwook Kim, LG Electronics

  4. Traffic model • Traffic model in EMD • UDP • Wireless Display • TCP • Buffered Video Streaming (e.g., Youtube, Netflix) • Video Conferencing • Multicast Video Streaming • Gaming • Virtual Desktop Infrastructure • VoIP • FTP • HTTP Suhwook Kim, LG Electronics

  5. Topology • Topology description • Single BSS • Number of STA: 6 ~ 18 • Distance between STA: 10 meter … … … … TCP Case 1: Case 2: TCP UDP Suhwook Kim, LG Electronics

  6. Simulation cases • Case 1: TCP only • Number of STAs: 6, 9, 12, 15, 18 • Case 2: TCP and UDP mixed • Number of STAs: 12 • 6 STAs for TCP: left side of AP • 6 STAs for UDP: right side of AP • TCP traffic: Buffered Video Class 6 (15.6 Mbps) • Case 2-1 • fixed UDP DL: 15 Mbps • variable UDP UL: 1, 3, 5, 7, 9, 10, 13, 15, 17, 20, 30 Mbps • Case 2-2 • variable UDP DL: 10, 20, 30, 40 Mbps • fixed UDP UL: 1 Mbps Suhwook Kim, LG Electronics

  7. Buffered Video Streaming • Traffic class: BV1(2 Mbps) ~ BV6(15.6 Mbps) • DL: TCP Video data (MAX 1500 Byte) • UL: TCP ACK (40 Byte) • Reason why BV6 is selected in this simulation • Highest required data rate in TCP traffic: sensitive to network status • Video traffic: most favorite content in nowadays • DL oriented: more common traffic direction Suhwook Kim, LG Electronics

  8. Legacy vs. OFDMA on TCP OFDMA Legacy • TCP ACK will be sent by CSMA/CA manner • STA doesn’t have to wait for sending TCP ACK • TCP ACK will be sent by scheduled manner • STA has to wait for sending TCP ACK • If AP received TCP ACK, it increases congestion window (it means AP will send more data in next time) • If AP received TCP NACK, it decreases congestion window (it means AP will send less data in next time) Suhwook Kim, LG Electronics

  9. TCP timeout • TCP timeout has critical impact on performance • Condition • MAC Queuing delay + Data TX delay + ACK Access delay > Timeout • Operation • AP will retransmit only one TCP segment and wait for TCP ACK • set congestion window to minimum (data rate decreases dramatically) • increase congestion window after receiving TCP ACK Suhwook Kim, LG Electronics

  10. Simulation Setup: Parameters *drop-free TCP transmission: no TCP queue drop and achieving maximum data rate Suhwook Kim, LG Electronics

  11. Simulation Result – Case 1 • TCP only Suhwook Kim, LG Electronics

  12. Simulation Result – Case 1 • TCP only *drop-free TCP transmission: no TCP queue drop and achieving maximum data rate Suhwook Kim, LG Electronics

  13. Discussion • Result • OFDMA shows better performance over legacy • Data rate of each TCP transmission • Number of drop-free TCP transmission • OFDMA gain over legacy significantly increases with the number of STAs transmitting TCP data • Analysis • TCP ACK transmission can be more failed by collision and hidden terminal when there are many TCP traffic in legacy system • Even though RTS/CTS is used, STA fails to transmit TCP ACK within TCP timeout bound sometimes Suhwook Kim, LG Electronics

  14. Simulation Result – Case 2 - 1 • TCP and UDP mixed, variable UDP UL Suhwook Kim, LG Electronics

  15. Simulation Result – Case 2 - 1 • TCP and UDP mixed, variable UDP UL *drop-free TCP transmission: no TCP queue drop and achieving maximum data rate Suhwook Kim, LG Electronics

  16. Simulation Result – Case 2 - 1 • TCP and UDP mixed, variable UDP UL Suhwook Kim, LG Electronics

  17. Simulation Result – Case 2 - 1 • TCP and UDP mixed, variable UDP UL Suhwook Kim, LG Electronics

  18. Discussion • Result • OFDMA shows better TCP performance in TCP/UDP mixed traffic • Even though there are a little throughput drop in UDP traffic in OFDMA, total throughput of TCP + UDP is enhanced • Analysis • TCP traffic is very sensitive about surroundings channel load • TCP ACK transmission can be more challenging job for STA in TCP and UDP mixed traffic because of long ACK access delay • When the number of UDP STA is increased, TCP STA couldn’t get TXOP to send TCP ACK easily Suhwook Kim, LG Electronics

  19. Simulation Result – Case 2 - 2 • TCP and UDP mixed, variable UDP DL Suhwook Kim, LG Electronics

  20. Discussion • Result • OFDMA shows better TCP performance in TCP/UDP mixed traffic even though UDP UL rate is very low • Analysis • In high rate UDP case, AP spent most time to send data for UDP station • TCP ACK transmission can be more challenging job in TCP and UDP mixed traffic because of MAC queuing delay Suhwook Kim, LG Electronics

  21. Conclusion • We observed that OFDMA shows a better TCP performance by well protecting TCP ACK from congestion • OFDMA gain will be increased by exploiting flexible RU (here we only used 242 RU) and a better scheduler (here we used random scheduler) • Will be done in next step Suhwook Kim, LG Electronics

  22. Reference • [1] ~ [7] 11-15/1095r0 ~ r6 • [8] 11-14/0571r12 11ax Evaluation Methodology • [9] 11-14/620r0 link adaptation for PHY SLS calibration Suhwook Kim, LG Electronics

  23. Appendix Suhwook Kim, LG Electronics

  24. Simulation Result – Case 2 - 1 • TCP and UDP mixed, variable UDP UL Suhwook Kim, LG Electronics

  25. Simulation Result – Case 2 - 1 • TCP and UDP mixed, variable UDP UL Suhwook Kim, LG Electronics

  26. Simulation Result – Case 2 - 2 • TCP and UDP mixed, variable UDP DL *drop-free TCP transmission: no TCP queue drop and achieving maximum data rate Suhwook Kim, LG Electronics

  27. Simulation Result – Case 2 - 2 • TCP and UDP mixed, variable UDP DL Suhwook Kim, LG Electronics

  28. Simulation Result – Case 2 - 2 • TCP and UDP mixed, variable UDP DL Suhwook Kim, LG Electronics

  29. Simulation Result – Case 2 - 2 • TCP and UDP mixed, variable UDP DL Suhwook Kim, LG Electronics

  30. Simulation Result – Case 2 - 2 • TCP and UDP mixed, variable UDP DL Suhwook Kim, LG Electronics

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