1. OFDMA performance in 11ax
July 2016
OFDMA performance in 11ax
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. Month Year
doc.: IEEE yy/xxxxr0
July 2016
Introduction
From September 2015 meeting, we have addressed OFDMA performance using PHY/MAC integrated simulator [1]~[7]
DL only, UL only
DL and UL mixed
Single BSS, OBSS(Residential)
MU-RTS/CTS
Full buffer traffic, low rate traffic
Suhwook Kim, LG Electronics
John Doe, Some Company

3. Simulator update We had used only UDP (CBR) traffic in our simulator
Month Year
doc.: IEEE yy/xxxxr0
July 2016
Simulator update
We had used only UDP (CBR) traffic in our simulator
UDP is very simple
Full buffer traffic model is widely used to evaluate communication system simulation
There are, however, so many TCP traffic in real world
Performance on TCP traffic may be different from UDP traffic because of its characteristics
So, we have implemented TCP model in our simulator
TCP traffic defined in our EMD[8]
TCP operation (TCP-Reno)
Suhwook Kim, LG Electronics
John Doe, Some Company

4. Traffic model Traffic model in EMD UDP TCP Wireless Display
July 2016
Traffic model
Traffic model in EMD
UDP
Wireless Display
TCP
Buffered Video Streaming (e.g., Youtube, Netflix)
Video Conferencing
Multicast Video Streaming
Gaming
Virtual Desktop Infrastructure
VoIP
FTP
HTTP
Suhwook Kim, LG Electronics

5. … … … … Topology Topology description Single BSS Number of STA: 6 ~ 18
Month Year
doc.: IEEE yy/xxxxr0
July 2016
Topology
Topology description
Single BSS
Number of STA: 6 ~ 18
Distance between STA: 10 meter … …
Case 1: …
TCP …
Case 2:
TCP
UDP
Distance from AP
5 m
15 m
25 m
35 m
45 m
55 m
65 m
75 m
85 m
OFDMA-MCS(D/U)
9 / 9
9 / 7
8 / 6
7 / 4
5 / 3
4 / 3
4 / 2
3 / 1
Legacy-MCS(D/U)
8 / 5
Suhwook Kim, LG Electronics
John Doe, Some Company

6. Simulation cases Case 1: TCP only Case 2: TCP and UDP mixed
July 2016
Simulation cases
Case 1: TCP only
Number of STAs: 6, 9, 12, 15, 18
Case 2: TCP and UDP mixed
Number of STAs: 12
6 STAs for TCP: left side of AP
6 STAs for UDP: right side of AP
TCP traffic: Buffered Video Class 6 (15.6 Mbps)
Case 2-1
fixed UDP DL: 15 Mbps
variable UDP UL: 1, 3, 5, 7, 9, 10, 13, 15, 17, 20, 30 Mbps
Case 2-2
variable UDP DL: 10, 20, 30, 40 Mbps
fixed UDP UL: 1 Mbps
Suhwook Kim, LG Electronics

7. Buffered Video Streaming
July 2016
Buffered Video Streaming
Traffic class: BV1(2 Mbps) ~ BV6(15.6 Mbps)
DL: TCP Video data (MAX 1500 Byte)
UL: TCP ACK (40 Byte)
Reason why BV6 is selected in this simulation
Highest required data rate in TCP traffic: sensitive to network status
Video traffic: most favorite content in nowadays
DL oriented: more common traffic direction
Suhwook Kim, LG Electronics

8. Legacy vs. OFDMA on TCP OFDMA Legacy July 2016
TCP ACK will be sent by CSMA/CA manner
STA doesn’t have to wait for sending TCP ACK
TCP ACK will be sent by scheduled manner
STA has to wait for sending TCP ACK
If AP received TCP ACK, it increases congestion window (it means AP will send more data in next time)
If AP received TCP NACK, it decreases congestion window (it means AP will send less data in next time)
Suhwook Kim, LG Electronics

9. TCP timeout TCP timeout has critical impact on performance Condition
July 2016
TCP timeout
TCP timeout has critical impact on performance
Condition
MAC Queuing delay + Data TX delay + ACK Access delay > Timeout
Operation
AP will retransmit only one TCP segment and wait for TCP ACK
set congestion window to minimum (data rate decreases dramatically)
increase congestion window after receiving TCP ACK
Suhwook Kim, LG Electronics

10. Simulation Setup: Parameters
July 2016
Simulation Setup: Parameters
Simulator Type
PHY/MAC Integrated simulator
Tx Power (AP/STA)
20/15 dBm
Antenna Gain (AP/STA)
0/-2 dBi
Traffic Model
TCP (Buffered Video class 6), UDP (CBR)
TCP Timeout: 100 msec
BSS Bandwidth
80MHz
OFDMA parameter
Random scheduler, 4 RUs(242 tones)
EDCA parameter
TCP: Default AC_VI, UDP: Default AC_BE
MSDU size (bytes)
1500
Feedback
GENIE
RTS/CTS
OFDMA: OFF, Legacy: ON
Max Retx 10
Symbol length
4 usec (legacy), 16usec (OFDMA)
Metrics
Throughput, Number of drop-free TCP transmission*
Queue Size
MAC Queue: AP: 2000 * # of associated STA, STA: 2000
TCP Queue: AP: 2000 * # of associated STA, STA: 2000
*drop-free TCP transmission: no TCP queue drop and achieving maximum data rate
Suhwook Kim, LG Electronics

11. Simulation Result – Case 1
Month Year
doc.: IEEE yy/xxxxr0
July 2016
Simulation Result – Case 1
TCP only
Suhwook Kim, LG Electronics
John Doe, Some Company

12. Simulation Result – Case 1
Month Year
doc.: IEEE yy/xxxxr0
July 2016
Simulation Result – Case 1
TCP only
*drop-free TCP transmission: no TCP queue drop and achieving maximum data rate
Suhwook Kim, LG Electronics
John Doe, Some Company

13. Discussion Result Analysis OFDMA shows better performance over legacy
July 2016
Discussion
Result
OFDMA shows better performance over legacy
Data rate of each TCP transmission
Number of drop-free TCP transmission
OFDMA gain over legacy significantly increases with the number of STAs transmitting TCP data
Analysis
TCP ACK transmission can be more failed by collision and hidden terminal when there are many TCP traffic in legacy system
Even though RTS/CTS is used, STA fails to transmit TCP ACK within TCP timeout bound sometimes
Suhwook Kim, LG Electronics

14. Simulation Result – Case 2 - 1
Month Year
doc.: IEEE yy/xxxxr0
July 2016
Simulation Result – Case 2 - 1
TCP and UDP mixed, variable UDP UL
Suhwook Kim, LG Electronics
John Doe, Some Company

15. Simulation Result – Case 2 - 1
Month Year
doc.: IEEE yy/xxxxr0
July 2016
Simulation Result – Case 2 - 1
TCP and UDP mixed, variable UDP UL
*drop-free TCP transmission: no TCP queue drop and achieving maximum data rate
Suhwook Kim, LG Electronics
John Doe, Some Company

16. Simulation Result – Case 2 - 1
Month Year
doc.: IEEE yy/xxxxr0
July 2016
Simulation Result – Case 2 - 1
TCP and UDP mixed, variable UDP UL
Suhwook Kim, LG Electronics
John Doe, Some Company

17. Simulation Result – Case 2 - 1
Month Year
doc.: IEEE yy/xxxxr0
July 2016
Simulation Result – Case 2 - 1
TCP and UDP mixed, variable UDP UL
Suhwook Kim, LG Electronics
John Doe, Some Company

18. Discussion Result Analysis
July 2016
Discussion
Result
OFDMA shows better TCP performance in TCP/UDP mixed traffic
Even though there are a little throughput drop in UDP traffic in OFDMA, total throughput of TCP + UDP is enhanced
Analysis
TCP traffic is very sensitive about surroundings channel load
TCP ACK transmission can be more challenging job for STA in TCP and UDP mixed traffic because of long ACK access delay
When the number of UDP STA is increased, TCP STA couldn’t get TXOP to send TCP ACK easily
Suhwook Kim, LG Electronics

19. Simulation Result – Case 2 - 2
Month Year
doc.: IEEE yy/xxxxr0
July 2016
Simulation Result – Case 2 - 2
TCP and UDP mixed, variable UDP DL
Suhwook Kim, LG Electronics
John Doe, Some Company

20. Discussion Result Analysis
July 2016
Discussion
Result
OFDMA shows better TCP performance in TCP/UDP mixed traffic even though UDP UL rate is very low
Analysis
In high rate UDP case, AP spent most time to send data for UDP station
TCP ACK transmission can be more challenging job in TCP and UDP mixed traffic because of MAC queuing delay
Suhwook Kim, LG Electronics

21. July 2016
Conclusion
We observed that OFDMA shows a better TCP performance by well protecting TCP ACK from congestion
OFDMA gain will be increased by exploiting flexible RU (here we only used 242 RU) and a better scheduler (here we used random scheduler)
Will be done in next step
Suhwook Kim, LG Electronics

22. July 2016
Reference
[1] ~ [7] 11-15/1095r0 ~ r6
[8] 11-14/0571r12 11ax Evaluation Methodology
[9] 11-14/620r0 link adaptation for PHY SLS calibration
Suhwook Kim, LG Electronics

23. Appendix
Suhwook Kim, LG Electronics

24. Simulation Result – Case 2 - 1
Month Year
doc.: IEEE yy/xxxxr0
July 2016
Simulation Result – Case 2 - 1
TCP and UDP mixed, variable UDP UL
Suhwook Kim, LG Electronics
John Doe, Some Company

25. Simulation Result – Case 2 - 1
Month Year
doc.: IEEE yy/xxxxr0
July 2016
Simulation Result – Case 2 - 1
TCP and UDP mixed, variable UDP UL
Suhwook Kim, LG Electronics
John Doe, Some Company

26. Simulation Result – Case 2 - 2
Month Year
doc.: IEEE yy/xxxxr0
July 2016
Simulation Result – Case 2 - 2
TCP and UDP mixed, variable UDP DL
*drop-free TCP transmission: no TCP queue drop and achieving maximum data rate
Suhwook Kim, LG Electronics
John Doe, Some Company

27. Simulation Result – Case 2 - 2
Month Year
doc.: IEEE yy/xxxxr0
July 2016
Simulation Result – Case 2 - 2
TCP and UDP mixed, variable UDP DL
Suhwook Kim, LG Electronics
John Doe, Some Company

28. Simulation Result – Case 2 - 2
Month Year
doc.: IEEE yy/xxxxr0
July 2016
Simulation Result – Case 2 - 2
TCP and UDP mixed, variable UDP DL
Suhwook Kim, LG Electronics
John Doe, Some Company

29. Simulation Result – Case 2 - 2
Month Year
doc.: IEEE yy/xxxxr0
July 2016
Simulation Result – Case 2 - 2
TCP and UDP mixed, variable UDP DL
Suhwook Kim, LG Electronics
John Doe, Some Company

30. Simulation Result – Case 2 - 2
Month Year
doc.: IEEE yy/xxxxr0
July 2016
Simulation Result – Case 2 - 2
TCP and UDP mixed, variable UDP DL
Suhwook Kim, LG Electronics
John Doe, Some Company