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11ax PAR Verification through OFDMA

This contribution evaluates the performance of OFDMA in meeting the 11ax PAR target of four times throughput enhancement. Indoor and outdoor scenarios are considered, and OFDMA gains are analyzed based on contention overhead, numerology, and transmit power.

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11ax PAR Verification through OFDMA

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  1. 11ax PAR Verification through OFDMA Date: 2017-01-16 Authors: Suhwook Kim, LG Electronics

  2. Introduction • The goal of this contribution is to verify that the target of 11ax PAR is met through OFDMA • i.e. four times throughput enhancement • We have addressed OFDMA performance based on PHY/MAC-integrated simulation from September 2015 [1]~[11] • In last meeting, we could achieve up to 5.9 times OFDMA throughput gain in Outdoor OBSS case Suhwook Kim, LG Electronics

  3. Main update in this submission • We evaluate OFDMA gain when the number of STA is varied • We considered indoor and outdoor scenarios Suhwook Kim, LG Electronics

  4. Simulation Parameters [12] Suhwook Kim, LG Electronics

  5. Simulation Setup for Indoor scenario • Topology description • Modified Residential scenario – 1floor only • 20 APs (Fixed location: center of room) • 4, 8, 16 STAs per one BSS (Random location) • MCS and BW is fixed (Best performance) • In OFDMA, DL and UL portion is 1:1 CH1 CH2 CH3 Suhwook Kim, LG Electronics

  6. Simulation Result for Indoor scenario • Sum Throughput and OFDMA gain Suhwook Kim, LG Electronics

  7. Discussion for Indoor scenario • OFDMA gain can be analyzed in three factors • Contention overhead: OFDMA can reduce contention overhead by collision • Numerology: OFDMA enhances frequency utilization • Transmit power gain: In uplink transmission, a STA can use more higher MCS in OFDMA because it will transmit a frame in narrow frequency band • In indoor scenario, OFDMA gain is not much and mainly obtained by numerology change • RTS/CTS is used and the number of STAs is under 16, so contention overhead can be mitigated in legacy system • AP and STAs are very close so they already used high MCS in legacy system Suhwook Kim, LG Electronics

  8. Simulation Setup for Outdoor scenario • Topology description • Modified Outdoor Large BSS – 1 tier only • 7 APs • 16 or 37 or 74 STAs per one BSS • Minimum distance from AP: 15 meters • Maximum distance from AP: 55 meters • MCS and BW is fixed (Best performance) • In OFDMA, DL and UL portion is 1:1 Suhwook Kim, LG Electronics

  9. Simulation Result for OBSS • Sum Throughput and OFDMA gain Suhwook Kim, LG Electronics

  10. Discussion for OBSS • In Outdoor scenario, however, three factors still work • Even though RTS/CTS is used, the number of STAs is relatively large, so contention overhead by collision cannot be ignorable in legacy system • Numerology gain is obvious • UMi channel is not appropriate for wideband transmission, so legacy system couldn’t utilize 80 MHz whole channel. But OFDMA can use 80 MHz channel by 37 RUs with more higher MCS Suhwook Kim, LG Electronics

  11. Simulation History – 1 • We have evaluated a lot of simulations about OFDMA • In September 2015 meeting, we firstly addressed OFDMA performance [2] • Topologies were simple single BSS and Residential scenario • Traffic was DL only or UL only, and not full buffer model • RTS/CTS is not used • OFDMA gain in Residential scenario was 1.8 in DL only and 1.7 UL only • In November 2015 meeting, we added DL&UL mixed traffic model [4] • OFDMA gain was 5.9 in DL&UL mixed full buffer traffic • In January/March 2016 meeting, we evaluated (MU)RTS/CTS [5][6] • OFDMA gain dropped to 1.3 when RTS/CTS is used Suhwook Kim, LG Electronics

  12. Simulation History – 2 • In July 2016 meeting, we evaluated TCP traffic model[7] • OFDMA showed better TCP performance in TCP/UDP mixed traffic • However, sum throughput of TCP&UDP is enhanced 1.4 times • In September 2016 meeting, we changed simulation scenario to Outdoor [10] • We used UMi and NLOS channel model • Traffic model is full buffered model • Topology was simple single BSS • All stations were co-located or evenly distributed • OFDMA gain was up to 15 times when all stations are located in 55 meters from AP • OFDMA gain is 2.7 when stations are evenly distributed Suhwook Kim, LG Electronics

  13. Simulation History – 3 • In November 2016 meeting, we adopted Outdoor Large BSS scenario in SSD [11] • We could achieve 5.9 OFDMA gain in Outdoor OBSS case • In this meeting, we evaluated OFDMA gain when the number of STAs is varied • In outdoor scenario, OFDMA can provide four times throughput enhancement when the number of STAs is larger than 16 • In indoor scenario, however, OFDMA gain is limited even though the number of STAs is changed Suhwook Kim, LG Electronics

  14. Conclusion • Through long simulation work, we have been able to analyze OFDMA performance as follows • OFDMA gain can be limited by RTS/CTS especially in indoor case • In general, OFDMA gain increases when the number of STAs increases • OFDMA can support more TCP traffic • In terms of verifying 11ax PAR requirement, we can achieve four times throughput gain in outdoor scenario using OFDMA only • OFDMA gain can be more improved by optimization • Scheduler(RU size, RU allocation, etc..), DL/UL portion, etc.. • To achieve four times in indoor scenario we may adopt Spatial Reuse and/or MU-MIMO Suhwook Kim, LG Electronics

  15. Reference • [1] ~ [10] 11-15/1095r1 ~ r10 OFDMA performance in 11ax • [11] 11-16/1363r0 11ax PAR Verification through OFDMA • [12] 11-14/0980r14 Simulation Scenarios Suhwook Kim, LG Electronics

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