1. OFDMA performance in 11ax
November 2015
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. Introduction The key feature of 11ax is OFDMA.
November 2015
Introduction
The key feature of 11ax is OFDMA.
In the previous meeting, we initially addressed OFDMA performance using PHY/MAC integrated simulator
OFDMA shows better performance in throughput and latency
This presentation provides update on it.
Suhwook Kim, LG Electronics

3. Update on Simulation Environments
November 2015
Update on Simulation Environments
Traffic direction
UL only or DL only
 DL & UL mixed traffic
Trigger frame generation
Trigger frame is generated in UL only case
Trigger frame is generated every Ttrg period and trigger frame has priority over DL data frame
AP Queue handling
AP’s queue can be fully buffered by data frames for a certain receiver
 Number of queued frame for a certain receiver is limited
Suhwook Kim, LG Electronics

4. Simulation Setup: Scheduler
November 2015
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

5. Simulation Setup: Frame length and padding
November 2015
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

6. Simulation Setup: Parameters
November 2015
Simulation Setup: Parameters
Simulator Type
PHY/MAC Integrated simulator
Tx Power (AP/STA)
20/15 dBm (Topology 3)
Antenna Gain (AP/STA)
0/-2 dBi
Traffic Model
DL and UL mixed (CBR)
BSS Bandwidth
80MHz
Noise Figure
Noise Floor
-101dBm per 20MHz
Rate Control Algorithm
Open Loop Link Adaption [3]
MSDU size (bytes)
1472
Feedback
GENIE
Max Retx 10
Symbol length
4 usec (legacy), 16usec (OFDMA)
Metrics
Throughput, *Latency [4]
Queue Size
AP: 2000 * # of associated STA, STA:2000
* The transmission latency is measured from the time that MAC receives a packet till the time that PHY starts transmitting.
Suhwook Kim, LG Electronics

7. Topology Topology description Simulation setting
November 2015
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

8. Simulation cases Case 1: 4 STAs, DL/UL 10 Mbps
November 2015
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

9. Simulation Result – Case 1
Month Year
doc.: IEEE yy/xxxxr0
November 2015
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 ↓
Legacy
OFDMA
Tput [Mbps]
PER DL
7.95
38.2 %
36.86 (135% ↑)
13.7 % UL
27.30
46.6 %
39.85 (31% ↑)
4.1 %
SUM
35.25
44.9 %
76.71 (76% ↑)
8.9 %
Suhwook Kim, LG Electronics
John Doe, Some Company

10. Simulation Result – Case 2
November 2015
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 → meet the maximum
Legacy
OFDMA
Tput [Mbps]
PER DL
4.00
0.9 %
4.00 (-)
7.0 % UL
3.4 %
1.0 %
SUM
8.00
2.2 %
8.00 (-)
4.1 %
Suhwook Kim, LG Electronics

11. Simulation Result – Case 3
Month Year
doc.: IEEE yy/xxxxr0
November 2015
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 STA case)
No STA’s contending → AP can get TXOP easily → DL Tput ↑
No STA’s contending → No UL Collision → UL Tput ↑ & UL PER ↓
Legacy
OFDMA
Tput [Mbps]
PER DL
15.67
30.4 %
38.65 (147% ↑)
17.6 % UL
30.43
37.3 %
39.83 (31% ↑)
5.0 %
SUM
46.10
35.1 %
78.48 (70% ↑)
11.7 %
Suhwook Kim, LG Electronics
John Doe, Some Company

12. Simulation Result – Case 4
Month Year
doc.: IEEE yy/xxxxr0
November 2015
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 STA case)
Very low rate traffic → meet the maximum
Legacy
OFDMA
Tput [Mbps]
PER DL
10.00
4.96 %
10.00 (-)
10.7 % UL
12.9 %
2.6 %
SUM
20.00
9.1 %
20.00 (-)
6.8 %
Suhwook Kim, LG Electronics
John Doe, Some Company

13. Simulation Result – Case 5
Month Year
doc.: IEEE yy/xxxxr0
November 2015
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
Ttrg of 20msec is enough for offered UL traffic.
DL has more opportunity when Ttrg increases
Ttrg = 10 msec
Ttrg = 15 msec
Ttrg= 20 msec
Tput [Mbps]
PER DL
36.86
13.7 %
39.75
7.0 %
39.99
5.9 % UL
39.85
4.1 %
39.91
1.5 %
39.89
1.0 %
SUM
76.71
8.9 %
79.66
4.3 %
79.88
3.5 %
Suhwook Kim, LG Electronics
John Doe, Some Company

14. Simulation Result – Case 6
Month Year
doc.: IEEE yy/xxxxr0
November 2015
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
Ttrg of 20msec is enough for offered UL traffic.
DL has more opportunity when Ttrg increases
UL TXOP = 5 msec
UL TXOP = 4 msec
UL TXOP = 3 msec
Tput [Mbps]
PER DL
36.86
13.7 %
39.21
9.7 %
39.94
6.3 % UL
39.85
4.1 %
39.90
2.5 %
39.93
1.1 %
SUM
76.71
8.9 %
79.11
6.2 %
79.87
3.8 %
Suhwook Kim, LG Electronics
John Doe, Some Company

15. Simulation Result – Case 7
Month Year
doc.: IEEE yy/xxxxr0
November 2015
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 ↓
Ttrg = 10 msec
Ttrg = 15 msec
Ttrg = 20 msec
Ttrg = 25 msec
Tput
PER DL
74.73
13.2 %
105.52
13.4 %
118.70
14.1 %
131.38
13.5 % UL
125.92
4.9 %
88.50
4.6 %
67.80
4.3 %
54.31
3.9 %
SUM
200.65
8.1 %
194.02
9.6 %
186.50
10.8 %
185.69
10.9 %
Suhwook Kim, LG Electronics
John Doe, Some Company

16. Simulation Result – Case 8
November 2015
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 ↓
UL TXOP = 5 msec
UL TXOP = 4 msec
UL TXOP = 3 msec
Tput [Mbps]
PER DL
74.73
13.2 %
99.00
13.3 %
129.42
12.2 UL
125.92
4.9 %
101.66
5.0 %
78.46
4.7
SUM
200.65
8.1 %
200.66
9.3 %
207.88
9.5
Suhwook Kim, LG Electronics

17. Next Step Following items will be added to OFDMA simulation
September 2015
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
Other schedulers
Contending by STAs and CCA after trigger frame
MU-RTS/CTS
Different scenarios/traffic model
Suhwook Kim, LG Electronics

18. November 2015
Conclusion
We addressed OFDMA performance on DL and UL mixed traffic case
OFDMA generally show throughput/latency gain
We initially addressed trend of OFDMA performance on variable trigger frame generation period and UL TXOP length
T rigger frame generation period and UL TXOP length have an effect on DL/UL performance
Suhwook Kim, LG Electronics

19. Reference [1] 11-15/0132r7 Spec Framework
November 2015
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

20. Backup Slide - Latency analysis
November 2015
Backup Slide - Latency analysis
Suhwook Kim, LG Electronics

21. Simulation Result – Case 1 & 2
November 2015
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 ↑
Legacy
OFDMA
10 Mbps
1 Mbps DL
1.56 sec
182 usec
277 msec
19.6 msec UL
766 msec
167 usec
8.05 msec
6.42 msec
Suhwook Kim, LG Electronics

22. Simulation Result – Case 1
November 2015
Simulation Result – Case 1
Legacy
OFDMA DL
1.56 sec
277 msec UL
766 msec
8.05 msec
Suhwook Kim, LG Electronics

23. Simulation Result – Case 2
November 2015
Simulation Result – Case 2
Legacy
OFDMA DL
182 usec
19.6 msec UL
167 usec
6.42 msec
Suhwook Kim, LG Electronics

24. Simulation Result – Case 3 & 4
November 2015
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 ↑
Legacy
OFDMA
4 Mbps
1 Mbps DL
2.34 sec
508 usec
244 msec
45.8 msec UL
858 msec
454 usec
26.6 msec
24.3 msec
Suhwook Kim, LG Electronics

25. Simulation Result – Case 3
November 2015
Simulation Result – Case 3
Legacy
OFDMA DL
2.34 sec
244 msec UL
858 msec
26.6 msec
Suhwook Kim, LG Electronics

26. Simulation Result – Case 4
November 2015
Simulation Result – Case 4
Legacy
OFDMA DL
508 usec
45.8 msec UL
454 usec
24.3 msec
Suhwook Kim, LG Electronics

27. Simulation Result – Case 5
November 2015
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 ↑
Ttrg = 10 msec
Ttrg = 15 msec
Ttrg= 20 msec DL
277 msec
9.56 msec
2.81 msec UL
8.05 msec
8.95 msec
13.7 msec
Suhwook Kim, LG Electronics

28. Simulation Result – Case 5
November 2015
Simulation Result – Case 5
Ttrg = 10 msec
Ttrg = 15 msec
Ttrg= 20 msec DL
277 msec
9.56 msec
2.81 msec UL
8.05 msec
8.95 msec
13.7 msec
Suhwook Kim, LG Electronics

29. Simulation Result – Case 6
November 2015
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 ↓
UL TXOP = 5 msec
UL TXOP = 4 msec
UL TXOP = 3 msec DL
277 msec
78.2 msec
8.60 msec UL
8.05 msec
7.02 msec
6.78 msec
Suhwook Kim, LG Electronics

30. Simulation Result – Case 6
November 2015
Simulation Result – Case 6
UL TXOP = 5 msec
UL TXOP = 4 msec
UL TXOP = 3 msec DL
277 msec
78.2 msec
8.60 msec UL
8.05 msec
7.02 msec
6.78 msec
Suhwook Kim, LG Electronics

31. Simulation Result – Case 7
November 2015
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 ↑
Ttrg = 10 msec
Ttrg = 15 msec
Ttrg= 20 msec
Ttrg= 25 msec DL
727 msec
673 msec
539 msec
475 msec UL
532 msec
990 msec
1.32 sec
1.54 sec
Suhwook Kim, LG Electronics

32. Simulation Result – Case 7
November 2015
Simulation Result – Case 7
Ttrg = 10 msec
Ttrg = 15 msec
Ttrg= 20 msec
Ttrg= 25 msec DL
727 msec
673 msec
539 msec
475 msec UL
532 msec
990 msec
1.32 sec
1.54 sec
Suhwook Kim, LG Electronics

33. Simulation Result – Case 8
November 2015
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 ↑
UL TXOP = 5 msec
UL TXOP = 4 msec
UL TXOP = 3 msec DL
727 msec
648 msec
486 msec UL
532 msec
895 msec
1.13 sec
Suhwook Kim, LG Electronics

34. Simulation Result – Case 8
November 2015
Simulation Result – Case 8
UL TXOP = 5 msec
UL TXOP = 4 msec
UL TXOP = 3 msec DL
727 msec
648 msec
486 msec UL
532 msec
895 msec
1.13 sec
Suhwook Kim, LG Electronics