OFDMA performance in 11ax

1. OFDMA performance in 11ax Date:2015-11-12 Authors: Suhwook Kim, LG Electronics

2. Introduction • The key feature of 11ax is OFDMA. • In the previous meeting, we initially addressed OFDMA performance using PHY/MAC integrated simulator • OFDMA shows better performance in throughput and latency • This presentation provides update on it. Suhwook Kim, LG Electronics

3. Update on Simulation Environments • Traffic direction • UL only or DL only  DL & UL mixed traffic • Trigger frame generation • Trigger frame is generated in UL only case • Trigger frame is generated every Ttrg period and trigger frame has priority over DL data frame • AP Queue handling • AP’s queue can be fully buffered by data frames for a certain receiver  Number of queued frame for a certain receiver is limited Suhwook Kim, LG Electronics

4. Simulation Setup: Scheduler • Scheduling resource • Maximum allocation per one station is 1 RU • 1 RU: 242-tone (total 4 RUs in 80 MHz) • Scheduling policy • Random: AP selects STAs randomly • In DL case, • primary destination is fixed (Head of AP’s queue) • frame length is determined by A-MPDU length to primary destination (legacy spec rule) Suhwook Kim, LG Electronics

5. Simulation Setup: Frame length and padding • UL • UL TXOP length is always fixed in one simulation drop • DL • DL TXOP length is variable (depends on primary destination) DL TXOP Length UL TXOP Length Suhwook Kim, LG Electronics

6. Simulation Setup: Parameters * The transmission latency is measured from the time that MAC receives a packet till the time that PHY starts transmitting. Suhwook Kim, LG Electronics

7. Topology • Topology description • 20 APs (Fixed location: center of room) • 4 or 10 STAs per one AP (Random location) • Simulation setting • Open Loop Link Adaption [3] • Channelization: Fixed channelization CH1 CH2 CH3 Suhwook Kim, LG Electronics

8. Simulation cases • Case 1: 4 STAs, DL/UL 10 Mbps • Case 2: 4 STAs, DL/UL 1 Mbps • Case 3: 10 STAs, DL/UL 4 Mbps • Case 4: 10 STAs, DL/UL 1 Mbps • Case 5: 4 STAs, DL/UL 10 Mbps, Ttrg varies • Case 6: 4 STAs, DL/UL 10 Mbps, UL TXOP length varies • Case 7: 4 STAs, DL/UL 50 Mbps, Ttrg varies • Case 8: 4 STAs, DL/UL 50 Mbps, UL TXOP length varies Suhwook Kim, LG Electronics

9. Simulation Result – Case 1 • 4 STAs for 1 AP, Ttrg = 10 msec • Data rate: DL 10 Mbps, UL 10 Mbps (Medium level) • Max DL TXOP: 5 msec, UL TXOP: 5 msec • Observation • No STA’s contending → AP can get TXOP easily → DL Tput ↑ • No STA’s contending → No UL Collision → UL Tput ↑ & UL PER ↓ Suhwook Kim, LG Electronics

10. Simulation Result – Case 2 • 4 STAs for 1 AP, Ttrg = 10 msec • Data rate: DL 1 Mbps, UL 1 Mbps (Low level) • Max DL TXOP: 5 msec, UL TXOP: 5 msec • Observation • Very low rate traffic → meet the maximum Suhwook Kim, LG Electronics

11. Simulation Result – Case 3 • 10 STAs for 1 AP, Ttrg = 10 msec • Data rate: DL 4 Mbps, UL 4 Mbps (Medium level) • Max DL TXOP: 5 msec, UL TXOP: 5 msec • Similar with Case 1 (4 STA case) • No STA’s contending → AP can get TXOP easily → DL Tput ↑ • No STA’s contending → No UL Collision → UL Tput ↑ & UL PER ↓ Suhwook Kim, LG Electronics

12. Simulation Result – Case 4 • 10 STAs for 1 AP, Ttrg = 10 msec • Data rate: DL 1 Mbps, UL 1 Mbps (Low level) • Max DL TXOP: 5 msec, UL TXOP: 5 msec • Similar with Case 2 (4 STA case) • Very low rate traffic → meet the maximum Suhwook Kim, LG Electronics

13. Simulation Result – Case 5 • 4 STAs for 1 AP • Data rate: DL 10 Mbps, UL 10 Mbps (Medium level) • Ttrg : 10, 15, 20 msec • Max DL TXOP: 5 msec, UL TXOP: 5 msec • Observation • Ttrg of 20msec is enough for offered UL traffic. • DL has more opportunity when Ttrg increases Suhwook Kim, LG Electronics

14. Simulation Result – Case 6 • 4 STAs for 1 AP, Ttrg = 10 msec • Data rate: DL 10 Mbps, UL 10 Mbps (Medium level) • Max DL TXOP: 5 msec, UL TXOP: 3, 4, 5 msec • Observation • Ttrg of 20msec is enough for offered UL traffic. • DL has more opportunity when Ttrg increases Suhwook Kim, LG Electronics

15. Simulation Result – Case 7 • 4 STAs for 1 AP • Data rate: DL 50 Mbps, UL 50 Mbps (Full buffered) • Ttrg : 10, 15, 20, 25 msec • Max DL TXOP: 5 msec, UL TXOP: 5 msec • Observation • Long Ttrg → DL TX ↑ → DL Tput ↑ • Long Ttrg → UL TX ↓ → UL Tput ↓ Suhwook Kim, LG Electronics

16. Simulation Result – Case 8 • 4 STAs for 1 AP, Ttrg = 10 msec • Data rate: DL 50 Mbps, UL 50 Mbps (Full buffered) • Max DL TXOP: 5 msec, UL TXOP: 3, 4, 5 msec • Observation • UL TXOP length↓ → DL TX ↑ → DL Tput ↑ • UL TXOP length↓ → UL TX ↓ → UL Tput ↓ Suhwook Kim, LG Electronics

17. Next Step • Following items will be added to OFDMA simulation • Different resource unit (26 tones, 52 tones, 106 tones, 484 tones) • Short packet traffic • Feedback modeling • Other schedulers • Contending by STAs and CCA after trigger frame • MU-RTS/CTS • Different scenarios/traffic model Suhwook Kim, LG Electronics

18. Conclusion • We addressed OFDMA performance on DL and UL mixed traffic case • OFDMA generally show throughput/latency gain • We initially addressed trend of OFDMA performance on variable trigger frame generation period and UL TXOP length • T rigger frame generation period and UL TXOP length have an effect on DL/UL performance Suhwook Kim, LG Electronics

19. Reference • [1] 11-15/0132r7 Spec Framework • [2] 11-14/0980r14 Simulation Scenarios • [3] 11-14/620r0 link adaptation for PHY SLS calibration • [4] 11-14/0571r10 11ax Evaluation Methodology Suhwook Kim, LG Electronics

20. Backup Slide- Latency analysis Suhwook Kim, LG Electronics

21. Simulation Result – Case 1 & 2 • 4 STAs for 1 AP, Ttrg = 10 msec • Data rate: DL 1/10 Mbps, UL 1/10 Mbps • Max DL TXOP: 5 msec, UL TXOP: 5 msec • Observation • Medium rate → AP can get TXOP easily → DL Latency ↓ • Medium rate → No UL collision → UL Latency ↓ • Very low rate → Inefficient trigger frame transmission ↑ → DL Data TX ↓ → DL Latency ↑ Suhwook Kim, LG Electronics

22. Simulation Result – Case 1 Suhwook Kim, LG Electronics

23. Simulation Result – Case 2 Suhwook Kim, LG Electronics

24. Simulation Result – Case 3 & 4 • 10 STAs for 1 AP, Ttrg = 10 msec • Data rate: DL 1/4 Mbps, UL 1/4 Mbps • Max DL TXOP: 5 msec, UL TXOP: 5 msec • Similar with Case 1&2 (4 STA case) • Medium rate → AP can get TXOP easily → DL Latency ↓ • Medium rate → No UL collision → UL Latency ↓ • Very low rate → Inefficient trigger frame transmission ↑ → DL Data TX ↓ → DL Latency ↑ Suhwook Kim, LG Electronics

25. Simulation Result – Case 3 Suhwook Kim, LG Electronics

26. Simulation Result – Case 4 Suhwook Kim, LG Electronics

27. Simulation Result – Case 5 • 4 STAs for 1 AP • Data rate: DL 10 Mbps, UL 10 Mbps • Ttrg : 10, 15, 20 msec • Max DL TXOP: 5 msec, UL TXOP: 5 msec • Observation • Long Ttrg → DL TX ↑ → DL Latency ↓ • Long Ttrg → UL TX ↓ → UL Latency ↑ Suhwook Kim, LG Electronics

28. Simulation Result – Case 5 Suhwook Kim, LG Electronics

29. Simulation Result – Case 6 • 4 STAs for 1 AP, Ttrg = 10 msec • Data rate: DL 10 Mbps, UL 10 Mbps • Max DL TXOP: 5 msec, UL TXOP: 3, 4, 5 msec • Observation • UL TXOP length↓ → DL TX ↑ → DL Latency ↓ • UL PER↓ → UL Retransmission ↓ → UL Latency ↓ Suhwook Kim, LG Electronics

30. Simulation Result – Case 6 Suhwook Kim, LG Electronics

31. Simulation Result – Case 7 • 4 STAs for 1 AP • Data rate: DL 50 Mbps, UL 50 Mbps • Ttrg : 10, 15, 20, 25 msec • Max DL TXOP: 5 msec, UL TXOP: 5 msec • Observation • Long Ttrg → DL TX ↑ → DL Latency ↓ • Long Ttrg → UL TX ↓ → UL Latency ↑ Suhwook Kim, LG Electronics

32. Simulation Result – Case 7 Suhwook Kim, LG Electronics

33. Simulation Result – Case 8 • 4 STAs for 1 AP, Ttrg = 10 msec • Data rate: DL 50 Mbps, UL 50 Mbps • Max DL TXOP: 5 msec, UL TXOP: 3, 4, 5 msec • Observation • UL TXOP length↓ → DL TX ↑ → DL Latency ↓ • UL TXOP length↓ → UL TX ↓ → UL Latency ↑ Suhwook Kim, LG Electronics

34. Simulation Result – Case 8 Suhwook Kim, LG Electronics