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OFDMA performance in 11ax. Date: 2015-11-16. Authors:. Introduction. We addressed OFDMA performance using PHY/MAC integrated simulator in previous meeting OFDMA shows better performance in our simulation cases
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OFDMA performance in 11ax Date: 2015-11-16 Authors: Suhwook Kim, LG Electronics
Introduction • We addressed OFDMA performance using PHY/MAC integrated simulator in previous meeting • OFDMA shows better performance in our simulation cases • After previous meeting, we enhanced OFDMA simulator based on discussion in previous meeting • We will address new OFDMA simulation results in this presentation Suhwook Kim, LG Electronics
Previous works • We addressed OFDMA performance based on • DL only and UL only traffic direction case • single BSS topology and residential scenario • high rate and low rate CBR traffic case • 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 • In general, OFDMA shows better latency performance • Random scheduler and queue length scheduler show similar performance • Because scheduler was very simple and AP’s queue wasn’t manageable Suhwook Kim, LG Electronics
Simulation enhancement • AP Queue handling • Before: AP’s queue can be fully buffered by data frames for a certain receiver • After: Number of queued frame for a certain receiver is limited • Traffic direction • Before: UL only or DL only • After: DL & UL mixed traffic • Trigger frame generation • Before: Trigger frame is generated every short time in UL only case (AP only transmitted trigger frame) • After: Trigger frame is generated every Ttrg period and trigger frame has priority over data frame Suhwook Kim, LG Electronics
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
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
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
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
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
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
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 → No Tput gain • UL OFDMA transmission → UL interference ↑ → DL PER ↑ • No STA’s contending → No UL Collision → UL PER ↓ Suhwook Kim, LG Electronics
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 STAs 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
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 STAs case) • Very low rate traffic → No Tput gain • UL OFDMA transmission → UL interference↑ → DL PER ↑ • No STA’s contending → No UL Collision → UL PER ↓ Suhwook Kim, LG Electronics
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 • Throughputs are similar • Long Ttrg → UL interference↓ → DL/UL PER ↓ Suhwook Kim, LG Electronics
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 • Throughputs are similar • UL TXOP length↓ → UL interference↓ → DL/UL PER ↓ Suhwook Kim, LG Electronics
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
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
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 • More sophisticated scheduler • Contending by STAs and CCA after trigger frame • MU-RTS/CTS Suhwook Kim, LG Electronics
Conclusion • We addressed OFDMA performance on DL and UL mixed traffic case • OFDMA still show throughput/latency gain except very low rate traffic case • Also we addressed trend of OFDMA performance on variable trigger frame generation periods and UL TXOP lengths • T rigger frame generation period and UL TXOP length have an effect on DL/UL performance Suhwook Kim, LG Electronics
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- Latency analysis Suhwook Kim, LG Electronics
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
Simulation Result – Case 1 Suhwook Kim, LG Electronics
Simulation Result – Case 2 Suhwook Kim, LG Electronics
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
Simulation Result – Case 3 Suhwook Kim, LG Electronics
Simulation Result – Case 4 Suhwook Kim, LG Electronics
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
Simulation Result – Case 5 Suhwook Kim, LG Electronics
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
Simulation Result – Case 6 Suhwook Kim, LG Electronics
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
Simulation Result – Case 7 Suhwook Kim, LG Electronics
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
Simulation Result – Case 8 Suhwook Kim, LG Electronics