1. 11ax PAR Verification through OFDMA
January 2017
11ax PAR Verification through OFDMA
Date:
Authors:
Name
Affiliations
Address
Phone
Suhwook Kim
LG Electronics
19, Yangjea-daero 11gil, Seocho-gu, Seoul , Korea
Hyunhee Park
Jeongki Kim
Kiseon Ryu
HanGyu Cho
Suhwook Kim, LG Electronics

2. January 2017
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
January 2017
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]
January 2017
Simulation Parameters [12]
Simulator Type
PHY/MAC Integrated simulator
Tx Power (AP/STA)
30/15 dBm (Outdoor), 20/15 dBm (Indoor)
Antenna Gain (AP/STA)
0/-2 dBi
RX sensitivity
-92 dBm
Traffic Model
UDP UL/DL mixed, Full buffer
BSS Bandwidth
80MHz
OFDMA parameter
Random scheduler (1 RU for 1 STA)
26, 52, 106, 242 tones RU
EDCA parameter
Default AC_BE
MSDU size (bytes)
1500 bytes for Legacy, 500 bytes for OFDMA
Feedback
GENIE
RTS/CTS
OFDMA: OFF, Legacy: ON
Max Retx 10
Symbol length
4 usec (legacy), 16usec (OFDMA)
Metrics
Throughput
Queue Size
MAC Queue: AP: 2000 * # of associated STA, STA: 2000
Suhwook Kim, LG Electronics

5. Simulation Setup for Indoor scenario
January 2017
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
January 2017
Simulation Result for Indoor scenario
Sum Throughput and OFDMA gain
Suhwook Kim, LG Electronics

7. Discussion for Indoor scenario
January 2017
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
January 2017
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
January 2017
Simulation Result for OBSS
Sum Throughput and OFDMA gain
Suhwook Kim, LG Electronics

10. January 2017
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. January 2017
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. January 2017
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. January 2017
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. January 2017
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
January 2017
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