OFDMA performance in 11ax September 2015 OFDMA performance in 11ax Date: 2015-09-14 Authors: Name Affiliations Address Phone Email Suhwook Kim LG Electronics 19, Yangjea-daero 11gil, Seocho-gu, Seoul 137-130, Korea +82-2-6912-6589 suhwook.kim@lge.com Hyeyoung Choi hy0117.choi@lge.com Jeongki Kim jeongki.kim@lge.com Kiseon Ryu kiseon.ryu@lge.com HanGyu Cho hg.cho@lge.com Suhwook Kim, LG Electronics
September 2015 Introduction The performance of OFDMA depends on both PHY and MAC, i.e., OFDMA resource unit structure, traffic and scheduling, feedback and link adaptation, and etc. This contribution addresses OFDMA performance using PHY/MAC integrated simulator Based on the new PHY structure and numerology which have been agreed in specification framework document [1] Based on three topologies Topology 1, 2 is one BSS case and Topology 3 is OBSS case (residential scenario (SS1)) [2] Suhwook Kim, LG Electronics
Simulation Setup: OFDMA operation September 2015 Simulation Setup: OFDMA operation UL operation Suhwook Kim, LG Electronics
Simulation Setup: OFDMA operation September 2015 Simulation Setup: OFDMA operation UL operation AP sends trigger frame by contending with AC_BE Trigger frame is transmitted by MCS 0, duplicated format in every 20 MHz channels (assuming 74 bytes long) STAs which are allocated by trigger frame send data frame MCS, transmission subband, and maximum frame length of data frame are addressed in the trigger frame If the station doesn’t have any queued data frame, it doesn’t send anything If the station doesn’t have enough data frame to fill maximum frame length, it adds padding bits to data frame STAs don’t perform CCA AP sends each BA frame in same subband with its data frame BA frame is transmitted by MCS 0 Contending of STAs is not permitted Suhwook Kim, LG Electronics
Simulation Setup: OFDMA operation September 2015 Simulation Setup: OFDMA operation DL operation Suhwook Kim, LG Electronics
Simulation Setup: OFDMA operation September 2015 Simulation Setup: OFDMA operation DL operation AP sends data frame by contending with AC_BE If AP doesn’t have enough data frame to 4 stations, some subband can be empty and wasted The STA in head of AP’s queue should be selected as primary destination Frame length is determined by primary destination Padding bits can be used in secondary destinations STA sends each BA frame in same subband with its data frame BA frame is transmitted by MCS 0 Suhwook Kim, LG Electronics
Simulation Setup: Scheduler September 2015 Simulation Setup: Scheduler Scheduling resource Maximum allocation per one station is 1 RU 1 RU: 242-tone (total 4 RUs in 80 MHz) Two simple scheduling policy Random AP selects STAs randomly Queue length AP selects STAs in order of each queue’s length 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
Random Scheduler Example UL case DL case September 2015 Random Scheduler Example UL case AP selects four STAs randomly in STA A ~ F DL case STA B is determined as primary destination AP selects three STAs randomly in STA C, STA A, STA D, and STA E Suhwook Kim, LG Electronics
Queue length Scheduler September 2015 Queue length Scheduler Example UL case AP selects STA F, E, C, A in order of each queue’s length DL case STA B is determined as primary destination AP selects STA A, E STA C or D will be selected randomly Suhwook Kim, LG Electronics
Simulation Setup: Frame length and padding September 2015 Simulation Setup: Frame length and padding Example UL case DL case Suhwook Kim, LG Electronics
Simulation Setup: Parameters September 2015 Simulation Setup: Parameters Simulator Type PHY/MAC Integrated simulator Tx Power (AP/STA) 23/17dBm (Topology 1, 2), 20/15dBm (Topology 3) Antenna Gain (AP/STA) 0/-2 dBi Traffic Model DL only, UL only (CBR) BSS Bandwidth 80MHz Noise Figure Noise Floor -101dBm per 20MHz Rate Control Algorithm Fixed MCS (Topology 1, 2), Open Loop Link Adaption (Topology 3) [3] MSDU size (bytes) 1472 Feedback GENIE Max Retx 10 Symbol length 4 usec (legacy), 16usec (OFDMA) Metrics Throughput, *Latency [4] Queue Size AP: 2000 * # of associated STA, STA:2000 * The transmission latency is measured from the time that MAC receives a packet till the time that PHY starts transmitting. Suhwook Kim, LG Electronics
Simulation Setup: Topologies September 2015 Simulation Setup: Topologies We used 3 topologies to analysis OFDMA performance in 11ax Topology 1 and 2 are single BSS case Pathlosses between AP and each STA are homogeneous in topology 1 But they are heterogeneous in topology 2 By topology 1 and 2, we can verify general OFDMA operation and scheduling scheme Topology 3 is modified residential scenario in SS1 By topology 3, we can expect performance gain of 11ax OFDMA in OBSS environment Suhwook Kim, LG Electronics
Topology 1 Topology description Simulation setting 1 AP and 10 STAs September 2015 Topology 1 Topology description 1 AP and 10 STAs AP and all STAs are co-located Simulation setting Fixed MCS MCS 0: 8.6 Mbps in 242 tones (total 34.4 Mbps) MCS 9: 114.7 Mbps in 242 tones (total 454.8 Mbps) Traffic; CBR DL only or UL only High rate: 4 Mbps per STA in MCS 0, 50 Mbps per STA in MCS9 Low rate: 2 Mbps per STA in MCS 0, 20 Mbps per STA in MCS9 TXOP limit: 5 msec in DL only, 4.6 msec in UL only Suhwook Kim, LG Electronics
Topology 1 – UL Throughput performance September 2015 Topology 1 – UL Throughput performance High rate traffic Low rate traffic Observation High rate traffic : Throughput gain is 40~50%. The main factors of throughput gain are resolving collision and new PHY structure Low rate traffic : OFDMA couldn’t show meaningful throughput gain because legacy network can support traffic load Tput [Mbps] Legacy Random Queue MCS 0, 4 Mbps 20.98 29.98 (43% ↑) MCS 9, 50 Mbps 268.64 399.76 (49% ↑) 399.78 (49% ↑) Tput [Mbps] Legacy Random Queue MCS 0, 2 Mbps 19.00 19.99 (5.2% ↑) MCS 9, 20 Mbps 199.27 199.86 (0.3% ↑) 199.82 (0.3% ↑) Suhwook Kim, LG Electronics
Topology 1 – UL Latency performance September 2015 Topology 1 – UL Latency performance High rate traffic Low rate traffic Observation High rate traffic: Latency gain is 30~50%. Low rate traffic: Latency gain is about 90%. AP sent trigger frame very frequently, so STAs can send data without contending Tput [Mbps] Legacy Random Queue MCS 0, 4 Mbps 2712.7 1503.0 (45% ↓) 1501.5 (45% ↓) MCS 9, 50 Mbps 786.9 542.0 (31% ↓) 533.4 (32% ↓) Tput [Mbps] Legacy Random Queue MCS 0, 2 Mbps 385.9 14.1 (96% ↓) 7.1 (98% ↓) MCS 9, 20 Mbps 89.7 8.0 (91% ↓) 10.9 (88% ↓) Suhwook Kim, LG Electronics
Topology 1 – DL Throughput performance September 2015 Topology 1 – DL Throughput performance High rate traffic Low rate traffic Observation High rate traffic : Throughput gain is about 20%. Collision resolving effect disappeared in DL case. Only numerology gain remained Low rate traffic : No OFDMA gain Tput [Mbps] Legacy Random Queue MCS 0, 4 Mbps 26.46 31.11 (18% ↑) 31.12 (18% ↑) MCS 9, 50 Mbps 333.13 416.73 (25% ↑) Tput [Mbps] Legacy Random Queue MCS 0, 2 Mbps 20.00 20.00 (-) MCS 9, 20 Mbps 199.93 199.91 (-) 199.92 (-) Suhwook Kim, LG Electronics
Topology 1 – DL Latency performance September 2015 Topology 1 – DL Latency performance High rate traffic Low rate traffic Observation High rate traffic: Latency gain is 20~40%. Low rate traffic: Latency gain is 20~80%. Tput [Mbps] Legacy Random Queue MCS 0, 4 Mbps 2031.0 1335.3 (34% ↓) 1331.0 (34% ↓) MCS 9, 50 Mbps 683.5 513.1 (25% ↓) 511.0 (25% ↓) Tput [Mbps] Legacy Random Queue MCS 0, 2 Mbps 4.69 1.13 (76% ↓) MCS 9, 20 Mbps 2.68 2.02 (25% ↓) 0.72 (73% ↓) Suhwook Kim, LG Electronics
Topology 2 Topology description Simulation setting 1 AP and 10 STAs September 2015 Topology 2 Topology description 1 AP and 10 STAs Simulation setting Fixed MCS TXOP limit: 5 msec Traffic DL only or UL only High rate: 115 Mbps per STA Low rate: 25 Mbps per STA DL MCS UL MCS STA 1, 10 4 (51.6Mbps) 2 (25.8Mbps) STA 2, 9 6 (77.4Mbps) 3 (34.4Mbps) STA 3, 8 7 (86.0Mbps) 5 (68.8Mbps) STA 4, 7 9 (114.7Mbps) 8 (103.2Mbps) STA 5, 6 Suhwook Kim, LG Electronics
Topology 2 – Throughput performance September 2015 Topology 2 – Throughput performance High rate traffic Low rate traffic Observation High rate traffic : UL throughput gain is about 50% and DL gain is 20%. Gain is similar with topology 1 Low rate traffic : DL gain is very low, but UL gain is very high. Because there is hidden terminal problem in legacy network, so legacy network shows very low throughput Tput [Mbps] Legacy Random Queue UL, 115 Mbps 162.50 241.69 (49% ↑) 241.43 (49% ↑) DL, 115 Mbps 238.29 288.19 (21% ↑) 294.20 (23% ↑) Tput [Mbps] Legacy Random Queue UL, 25 Mbps 53.69 188.20 (251% ↑) 174.51 (225% ↑) DL, 25 Mbps 238.15 249.57 (4.8% ↑) 249.42 (4.7% ↑) Suhwook Kim, LG Electronics
Topology 2 – Latency performance September 2015 Topology 2 – Latency performance High rate traffic Low rate traffic Observation High rate traffic: Latency gain is 20~60%. Gain is similar with topology 1 Low rate traffic: Latency gain is 60~90%. Generally latency gain is more higher in low rate traffic case than in high rate traffic Tput [Mbps] Legacy Random Queue UL, 115 Mbps 2624.9 939.8 (64% ↓) 943.8 (64% ↓) DL, 115 Mbps 981.1 786.7 (20% ↓) 793.0 (19% ↓) Tput [Mbps] Legacy Random Queue UL, 25 Mbps 3081.1 529.4 (83% ↓) 1173.6 (62% ↓) DL, 25 Mbps 101.7 22.4 (78% ↓) 5.7 (94% ↓) Suhwook Kim, LG Electronics
Topology 3 Topology description Simulation setting September 2015 Topology 3 Topology description 20 APs (Fixed location: center of room) 4 or 10 STAs per one AP (Random location) Simulation setting Open Loop Link Adaption [1] Traffic DL only or UL only High rate: 20 Mbps per STA in 4-STA-SIM, 8 Mbps per STA in 10-STA-SIM Low rate: 2 Mbps per STA TXOP limit: 5 msec Channelization: Random choice in three channels Suhwook Kim, LG Electronics
Topology 3 – UL Throughput performance September 2015 Topology 3 – UL Throughput performance High rate traffic Low rate traffic Observation High rate traffic : Throughput gain is 30~70%. Low rate traffic : Throughput gain is 30~250%. Even though traffic load is very low, legacy network couldn’t fully support that traffic because of OBSS interference and hidden terminal. But OFDMA can support. Tput [Mbps] Legacy Random Queue 4 STA, 20 Mbps 36.13 60.94 (69% ↑) 61.79 (71% ↑) 10 STA, 8 Mbps 41.23 55.09 (34% ↑) 61.65 (50% ↑) Tput [Mbps] Legacy Random Queue 4 STA, 2 Mbps 6.04 7.98 (32% ↑) 7.97 (32% ↑) 10 STA, 2 Mbps 5.66 19.39 (243% ↑) 18.42 (225% ↑) Suhwook Kim, LG Electronics
Topology 3 – UL Latency performance September 2015 Topology 3 – UL Latency performance High rate traffic Low rate traffic Observation High rate traffic: Latency gain is 40~90%. Low rate traffic: Latency gain is 25~80%. Unlike topology 1 and 2, latency gain is higher in high rate traffic than low rate traffic Tput [Mbps] Legacy Random Queue 4 STA, 20 Mbps 2712.7 1503.0 (45% ↓) 1501.5 (45% ↓) 10 STA, 8 Mbps 1978.1 302.7 (85% ↓) 212.0 (89% ↓) Tput [Mbps] Legacy Random Queue 4 STA, 2 Mbps 45.6 10.3 (77% ↓) 33.9 (26% ↓) 10 STA, 2 Mbps 194.8 55.1 (72% ↓) 97.0 (50% ↓) Suhwook Kim, LG Electronics
Topology 3 – DL Throughput performance September 2015 Topology 3 – DL Throughput performance High rate traffic Low rate traffic Observation High rate traffic : Throughput gain is about 80%. Unlike topology 1 and 2, DL gain is higher than UL gain in topology 3. Main factors are MAC overhead and OBSS interference. Low rate traffic : No OFDMA gain Tput [Mbps] Legacy Random Queue 4 STA, 20 Mbps 43.20 78.87 (83% ↑) 79.31 (84% ↑) 10 STA, 8 Mbps 43.46 79.64 (83% ↑) 80.92 (86% ↑) Tput [Mbps] Legacy Random Queue 4 STA, 2 Mbps 8.00 8.00 (-) 10 STA, 2 Mbps 20.00 20.00 (-) Suhwook Kim, LG Electronics
Topology 3 – DL Latency performance September 2015 Topology 3 – DL Latency performance High rate traffic Low rate traffic Observation High rate traffic: Latency gain is about 98~99%. Low rate traffic: Latency is very low in legacy and OFDMA. Gain is not clear Tput [Mbps] Legacy Random Queue 4 STA, 20 Mbps 3497 2.17 (99% ↓) 2.92 (99% ↓) 10 STA, 8 Mbps 799.8 15.1 (98% ↓) 14.3 (98% ↓) Tput [Mbps] Legacy Random Queue 4 STA, 2 Mbps 0.19 0.29 (53% ↑) 0.37 (95% ↑) 10 STA, 2 Mbps 1.35 1.27 (6% ↓) 1.12 (17% ↓) Suhwook Kim, LG Electronics
OFDMA performance tendency September 2015 OFDMA performance tendency We could observe following tendency in our limited simulation Single BSS case Throughput gain UL OFDMA > DL OFDMA high traffic load > low traffic load OBSS case DL OFDMA > UL OFDMA OBSS > single BSS However, we need more elaborate simulations to confirm these tendencies Latency gain UL OFDMA > DL OFDMA low traffic load > high traffic load Latency gain DL OFDMA > UL OFDMA No gain in DL Suhwook Kim, LG Electronics
Next Step Following items will be added to OFDMA simulation September 2015 Next Step Following items will be added to OFDMA simulation Different resource unit (26 tones, 52 tones, 106 tones, 484 tones) DL & UL mixed traffic Short packet traffic Feedback modeling More sophisticated scheduler Contending by STAs and CCA after trigger frame MU-RTS/CTS Suhwook Kim, LG Electronics
September 2015 Conclusion We addressed OFDMA performance using PHY/MAC integrated simulator Performance metrics are throughput and latency Performance gain of OFDMA depends on topology, traffic direction, and traffic load OFDMA shows 20~80% throughput gain in high loaded traffic In low traffic load, throughput gain is limited Random scheduler and queue length scheduler show similar performance Suhwook Kim, LG Electronics
Reference [1] 11-15/0132r7 Spec Framework September 2015 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
Backup Slide - Topology 1, UL, MCS 0 September 2015 Backup Slide - Topology 1, UL, MCS 0 Suhwook Kim, LG Electronics
Topology 1 – UL, MCS 0, 4 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 20.98 29.98 Latency [msec] 2712.7 1503.0 1501.5 Suhwook Kim, LG Electronics
Topology 1 – UL, MCS 0, 2 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 19.00 19.99 Latency [msec] 385.9 14.1 7.1 Suhwook Kim, LG Electronics
Topology 1 – UL, MCS 0, 4 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 20.98 29.98 Latency [msec] 2712.7 1503.0 1501.5 Suhwook Kim, LG Electronics
Topology 1 – UL, MCS 0, 2 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 19.00 19.99 Latency [msec] 385.9 14.1 7.1 Suhwook Kim, LG Electronics
Topology 1 – UL, MCS 0, 2 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 19.00 19.99 Latency [msec] 385.9 14.1 7.1 Suhwook Kim, LG Electronics
Backup Slide - Topology 1, UL, MCS 9 September 2015 Backup Slide - Topology 1, UL, MCS 9 Suhwook Kim, LG Electronics
Topology 1 – UL, MCS 9, 50 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 268.64 399.76 399.78 Latency [msec] 786.9 542.0 533.4 Suhwook Kim, LG Electronics
Topology 1 – UL, MCS 9, 20 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 199.27 199.86 199.823 Latency [msec] 89.7 8.0 10.9 Suhwook Kim, LG Electronics
Topology 1 – UL, MCS 9, 50 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 268.64 399.76 399.78 Latency [msec] 786.9 542.0 533.4 Suhwook Kim, LG Electronics
Topology 1 – UL, MCS 9, 20 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 199.27 199.86 199.823 Latency [msec] 89.7 8.0 10.9 Suhwook Kim, LG Electronics
Topology 1 – UL, MCS 9, 20 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 199.27 199.86 199.823 Latency [msec] 89.7 8.0 10.9 Suhwook Kim, LG Electronics
Backup Slide - Topology 1, DL, MCS 0 September 2015 Backup Slide - Topology 1, DL, MCS 0 Suhwook Kim, LG Electronics
Topology 1 – DL, MCS 0, 4 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 26.46 31.11 31.12 Latency [msec] 2031.0 1335.3 1331.0 Suhwook Kim, LG Electronics
Topology 1 – DL, MCS 0, 2 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 20.00 Latency [msec] 4.69 1.13 Suhwook Kim, LG Electronics
Topology 1 – DL, MCS 0, 4 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 26.46 31.11 31.12 Latency [msec] 2031.0 1335.3 1331.0 Suhwook Kim, LG Electronics
Topology 1 – DL, MCS 0, 2 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 20.00 Latency [msec] 4.69 1.13 Suhwook Kim, LG Electronics
Backup Slide - Topology 1, DL, MCS 9 September 2015 Backup Slide - Topology 1, DL, MCS 9 Suhwook Kim, LG Electronics
Topology 1 – DL, MCS 9, 50 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 333.13 416.73 Latency [msec] 683.5 513.1 511.0 Suhwook Kim, LG Electronics
Topology 1 – DL, MCS 9, 20 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 199.93 199.91 199.92 Latency [msec] 2.68 2.02 0.72 Suhwook Kim, LG Electronics
Topology 1 – DL, MCS 9, 50 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 416.73 Latency [msec] 683.5 513.1 511.0 Suhwook Kim, LG Electronics
Topology 1 – DL, MCS 9, 20 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 199.93 199.91 199.92 Latency [msec] 2.68 2.02 0.72 Suhwook Kim, LG Electronics
Backup Slide - Topology 1, UL September 2015 Backup Slide - Topology 1, UL Suhwook Kim, LG Electronics
Topology 2 – UL, 115Mbps September 2015 Legacy Random Queue Throughput [Mbps] 162.50 241.69 241.43 Latency [msec] 2624.9 939.8 943.8 Suhwook Kim, LG Electronics
Topology 2 – UL, 25 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 53.69 188.20 174.51 Latency [msec] 3081.1 529.4 1173.6 Suhwook Kim, LG Electronics
Topology 2 – UL, 115Mbps September 2015 Legacy Random Queue Throughput [Mbps] 162.50 241.69 241.43 Latency [msec] 2624.9 939.8 943.8 Suhwook Kim, LG Electronics
Topology 2 – UL, 25 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 53.69 188.20 174.51 Latency [msec] 3081.1 529.4 1173.6 Suhwook Kim, LG Electronics
Backup Slide - Topology 2, DL September 2015 Backup Slide - Topology 2, DL Suhwook Kim, LG Electronics
Topology 2 – DL, 115Mbps September 2015 Legacy Random Queue Throughput [Mbps] 238.29 288.19 294.20 Latency [msec] 981.1 786.7 793.0 Suhwook Kim, LG Electronics
Topology 2 – DL, 25 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 238.15 249.57 249.42 Latency [msec] 101.7 22.4 5.7 Suhwook Kim, LG Electronics
Topology 2 – DL, 115Mbps September 2015 Legacy Random Queue Throughput [Mbps] 238.29 288.19 294.20 Latency [msec] 981.1 786.7 793.0 Suhwook Kim, LG Electronics
Backup Slide - Topology 3, UL September 2015 Backup Slide - Topology 3, UL Suhwook Kim, LG Electronics
Topology 3 – UL, 10 STA, 8 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 41.23 55.09 61.65 Latency [msec] 1978.1 302.7 212.0 Suhwook Kim, LG Electronics
Topology 3 – UL, 10 STA, 2 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 5.66 19.39 18.42 Latency [msec] 194.8 55.1 97.0 Suhwook Kim, LG Electronics
Topology 3 – UL, 4 STA, 2 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 6.04 7.98 7.97 Latency [msec] 45.6 10.3 33.9 Suhwook Kim, LG Electronics
Backup Slide - Topology 3, DL September 2015 Backup Slide - Topology 3, DL Suhwook Kim, LG Electronics
Topology 3 – DL, 10 STA, 8 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 43.46 79.64 80.92 Latency [msec] 799.8 15.1 14.3 Suhwook Kim, LG Electronics
Topology 3 – DL, 10 STA, 2 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 20.00 Latency [msec] 1.35 1.27 1.12 Suhwook Kim, LG Electronics
Topology 3 – DL, 4 STA, 2 Mbps September 2015 Legacy Random Queue Throughput [Mbps] 8.00 Latency [msec] 0.19 0.29 0.37 Suhwook Kim, LG Electronics