doc.: IEEE 802.11-15/1095r9
July 2016
OFDMA performance in 11ax
Date: 2016-07-25
Authors:
Name
Suhwook Kim
Hyunhee Park
Jeongki Kim
Kiseon Ryu
HanGyu Cho
Submission
Affiliations
LG Electronics
LG Electronics
LG Electronics
LG Electronics
LG Electronics
Address
19, Yangjea-daero
11gil, Seocho-gu,
Seoul 137-130, Korea
Slide 1
Phone
+82-2-6912-6589
Email
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
July 2016
Introduction
• From September 2015 meeting, we have addressed
OFDMA performance using PHY/MAC integrated
simulator [1]~[7]
–
–
–
–
–
Submission
DL only, UL only
DL and UL mixed
Single BSS, OBSS(Residential)
MU-RTS/CTS
Full buffer traffic, low rate traffic
Slide 2
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
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)
Submission
Slide 3
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
July 2016
Traffic model
• Traffic model in EMD
– UDP
• Wireless Display
– TCP
•
•
•
•
•
•
•
•
Submission
Buffered Video Streaming (e.g., Youtube, Netflix)
Video Conferencing
Multicast Video Streaming
Gaming
Virtual Desktop Infrastructure
VoIP
FTP
HTTP
Slide 4
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
July 2016
Topology
• Topology description
– Single BSS
– Number of STA: 6 ~ 18
– Distance between STA: 10 meter
10m
10 m
10 m
···
Case 1:
Case 2:
···
…
…
Distance from AP
STA
STA
AP
STA
STA
TCP
TCP
UDP
…
…
5m
15 m
25 m
35 m
45 m
55 m
65 m
75 m
85 m
OFDMA-MCS(D/U) 9 / 9
9/9
9/7
8/6
7/4
5/3
4/3
4/2
3/1
Legacy-MCS(D/U)
9/9
9/7
8/5
7/4
5/3
4/2
4/2
3/1
Submission
9/9
Slide 5
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
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
Submission
Slide 6
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
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
Submission
Slide 7
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
July 2016
Legacy vs. OFDMA on TCP
OFDMA
Legacy
• TCP ACK will be sent by CSMA/CA manner
• STA doesn’t have to wait for sending TCP
ACK
STA
• TCP ACK will be sent by scheduled manner
• STA has to wait for sending TCP ACK
STA
AP
AP
CSMA/CA
• 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)
Submission
Slide 8
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
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
STA
TCP
STA
MAC
AP
MAC
AP
TCP
TCP Data
MAC Queuing delay
Data TX delay
TCP ACK
ACK Access delay
Submission
Slide 9
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
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
Submission
Slide 10
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
July 2016
Simulation Result – Case 1
• TCP only
Submission
Slide 11
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
July 2016
Simulation Result – Case 1
• TCP only
*drop-free TCP transmission: no TCP queue drop and achieving maximum data rate
Submission
Slide 12
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
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
Submission
Slide 13
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
July 2016
Simulation Result – Case 2 - 1
• TCP and UDP mixed, variable UDP UL
Submission
Slide 14
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
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
Submission
Slide 15
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
July 2016
Simulation Result – Case 2 - 1
• TCP and UDP mixed, variable UDP UL
Submission
Slide 16
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
July 2016
Simulation Result – Case 2 - 1
• TCP and UDP mixed, variable UDP UL
Submission
Slide 17
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
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
Submission
Slide 18
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
July 2016
Simulation Result – Case 2 - 2
• TCP and UDP mixed, variable UDP DL
Submission
Slide 19
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
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
Submission
Slide 20
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
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
Submission
Slide 21
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
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
Submission
Slide 22
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
Appendix
Submission
Slide 23
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
July 2016
Simulation Result – Case 2 - 1
• TCP and UDP mixed, variable UDP UL
Submission
Slide 24
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
July 2016
Simulation Result – Case 2 - 1
• TCP and UDP mixed, variable UDP UL
Submission
Slide 25
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
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
Submission
Slide 26
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
July 2016
Simulation Result – Case 2 - 2
• TCP and UDP mixed, variable UDP DL
Submission
Slide 27
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
July 2016
Simulation Result – Case 2 - 2
• TCP and UDP mixed, variable UDP DL
Submission
Slide 28
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
July 2016
Simulation Result – Case 2 - 2
• TCP and UDP mixed, variable UDP DL
Submission
Slide 29
Suhwook Kim, LG Electronics
doc.: IEEE 802.11-15/1095r9
July 2016
Simulation Result – Case 2 - 2
• TCP and UDP mixed, variable UDP DL
Submission
Slide 30
Suhwook Kim, LG Electronics