1. The document compares WiFi performance test results with and without AirTime Fairness enabled on a DrayTek access point. Without AirTime Fairness, some stations experienced stalls while others occupied most of the airtime. With AirTime Fairness enabled, station performance became more equalized. 2. Test results showed that individual station performance improved with AirTime Fairness enabled, especially for stations with slower link rates. The overall performance of stations with good link rates also increased. 3. AirTime Fairness helped distribute airtime more evenly among stations, improving performance for stations that experienced stalls without it. Stations with better hardware could still achieve better performance than others.

1. 1
AirTime Fairness
- AP900 1.1.5 -
Webinar
Henry Lo
2015.1.13

2. 2
• Test Environment Setup
• Without AirTime Fairness
• With AirTime Fairness
• Comparison in Between
• How AirTime Fairness Works
• Exception of AirTime Fairness
• Summary
• Q&A
Outline

3. 3
• The Following WiFi Performance test results are not
intended and/or necessary to be considered as the DrayTek
Access Point Performance “Benchmark” due to the
following reasons
- Station Link Rates are 130Mbps and 65Mbps only (not 300Mbps)
- Laptops are random ones without promise of good performance;
in fact, we even put in some slow laptops to demonstrate the
“exception case”, which may somewhat lower the overall
performance
- There were other APs nearby using different channels
• Mainly, we are focusing on demonstrating the Improvement
brought by AirTime Fairness in this session
Notice

4. 4
Test Environment Setup
Link Rate 130Mbps
Link Rate 65Mbps
Doors Keep Close
AP900
192.168.38.2/24
110120130140150160170
210
PC, JPerf Client
JPerf Servers
Test Direction: LAN to WLAN

5. 5
Test Environment Setup
7 Laptops with Link Rate 130Mbps

6. 6
Test Environment Setup
AP900 Running 1.1.5RC6

7. 7
Test Environment Setup
1 Laptop with Link Rate 65Mbps

8. 8
Test Environment Setup
JPerf, 5 Sessions Running 60 Seconds

9. 9
• Theory:
- Channel Can be Accessed by Only One Station at a Time (802.11)
- Each Station has Equal Priority to Access the Channel (802.11e)
8 Stations
12.5%
12.5%
12.5%
12.5% 12.5%
12.5%
12.5%
12.5%
20 Stations
Test Environment Setup
Theory About AirTime

10. 10
Without
AirTimeFairness
Test 1 Test 2 Test 3 Average
192.168.38.110 1.17 1.78 1.84 1.60
192.168.38.120 7.26 7.18 7.58 7.34
192.168.38.130 8.59 8.25 8.70 8.51
192.168.38.140 4.37 3.46 3.68 3.84
192.168.38.150 7.22 7.06 7.13 7.14
192.168.38.160 6.93 6.81 7.83 7.19
192.168.38.170 1.68 1.57 1.75 1.67
Sub Total 37.22 36.11 38.51 37.28
192.168.38.210 5.49 5.83 5.46 5.59
Total 42.71 41.94 43.97 42.87
Without AirTime Fairness

11. 11
Some Stations May Feel the
Without AirTime Fairness
“Stall”

12. 12
Without
AirTimeFairness
Test 1 Test 2 Test 3 Average
192.168.38.
110 1.17 1.78 1.84 1.60
192.168.38.
120 7.26 7.18 7.58 7.34
192.168.38.
130 8.59 8.25 8.70 8.51
192.168.38.
140 4.37 3.46 3.68 3.84
192.168.38.
150 7.22 7.06 7.13 7.14
192.168.38.
160 6.93 6.81 7.83 7.19
192.168.38.
170 1.68 1.57 1.75 1.67
Sub Total 37.22 36.11 38.51 37.28
192.168.38.
210 5.49 5.83 5.46 5.59
Total 42.71 41.94 43.97 42.87
Without AirTime Fairness
Without
AirTime Fairness
Performance / Total
192.168.38.110 1.60 3.73%
192.168.38.120 7.34 17.12%
192.168.38.130 8.51 19.85%
192.168.38.140 3.84 8.96%
192.168.38.150 7.14 16.66%
192.168.38.160 7.19 16.77%
192.168.38.170 1.67 3.90%
Sub Total 37.28 86.96%
192.168.38.210 5.59 13.04%
Total 42.87 100%
• Some Stations May Feel the
“Stall”
• Some Other Stations are the
“AirTime Occupier”

13. 13
Without AirTime Fairness
• Theory: Each Station has
Equal Probability to Use AirTime
- But Some Stations may be Good at
Occupying the AirTime
Theory
12.50%
12.50%
12.50%
12.50% 12.50%
12.50%
12.50%
12.50%
• Test Result without AirTime
Fairness
Without Airtime Fairness
210
13.35%
170
3.88%
160
16.70%
150
16.60%
140
8.93%
130
19.77%
120
17.05%
110
3.72%

14. 14
With
AirTimeFairness
Test 1 Test 2 Test 3 Average
192.168.38.110 4.75 4.70 4.57 4.67
192.168.38.120 5.71 5.59 5.68 5.66
192.168.38.130 9.09 9.21 8.21 8.84
192.168.38.140 5.21 5.14 5.37 5.24
192.168.38.150 8.34 8.53 8.45 8.44
192.168.38.160 9.52 9.23 9.41 9.39
192.168.38.170 3.30 3.29 3.42 3.34
Sub Total 45.92 45.69 45.11 45.57
192.168.38.210 4.64 4.80 4.54 4.66
Total 50.56 50.49 49.65 50.23
With AirTime Fairness

15. 15
With AirTime Fairness
“Stall”

16. 16
• No More “Stall”! With
AirTimeFairness
Test 1 Test 2 Test 3 Average
192.168.38.
110 4.75 4.70 4.57 4.67
192.168.38.
120 5.71 5.59 5.68 5.66
192.168.38.
130 9.09 9.21 8.21 8.84
192.168.38.
140 5.21 5.14 5.37 5.24
192.168.38.
150 8.34 8.53 8.45 8.44
192.168.38.
160 9.52 9.23 9.41 9.39
192.168.38.
170 3.30 3.29 3.42 3.34
Sub Total 45.92 45.69 45.11 45.57
192.168.38.
210 4.64 4.80 4.54 4.66
Total 50.56 50.49 49.65 50.23
With AirTime Fairness
With
AirTime Fairness
Performance / Total
192.168.38.110 4.67 9.30%
192.168.38.120 5.66 11.27%
192.168.38.130 8.84 17.60%
192.168.38.140 5.24 10.43%
192.168.38.150 8.44 16.80%
192.168.38.160 9.39 18.69%
192.168.38.170 3.34 6.65%
Sub Total 45.57 90.72%
192.168.38.210 4.66 9.28%
Total 50.23 100.00%

17. 17
With AirTime Fairness
210
9.26%170
6.64%
160
18.65%
150
16.76%
140
10.41%
130
17.76%
120
11.25%
110
9.28%
With AirTime Fairness
Theory
12.50%
12.50%
12.50%
12.50% 12.50%
12.50%
12.50%
12.50%

18. 18
Without
AirTime Fairness
Performance / Total
With
AirTime Fairness
Performance / Total
192.168.38.110 1.60 3.73% 4.67 9.30%
192.168.38.120 7.34 17.12% 5.66 11.27%
192.168.38.130 8.51 19.85% 8.84 17.60%
192.168.38.140 3.84 8.96% 5.24 10.43%
192.168.38.150 7.14 16.66% 8.44 16.80%
192.168.38.160 7.19 16.77% 9.39 18.69%
192.168.38.170 1.67 3.90% 3.34 6.65%
Sub Total 37.28 86.96% 45.57 90.72%
192.168.38.210 5.59 13.04% 4.66 9.28%
Total 42.87 50.23
Comparison in Between
Individual Performance

19. 19
Without
AirTime Fairness
With
AirTime Fairness
Difference
Individual
Improvement
192.168.38.110 1.60 4.67 3.07 191.88%
192.168.38.120 7.34 5.66 -1.68 -22.89%
192.168.38.130 8.51 8.84 0.33 3.88%
192.168.38.140 3.84 5.24 1.4 36.46%
192.168.38.150 7.14 8.44 1.3 18.21%
192.168.38.160 7.19 9.39 2.2 30.60%
192.168.38.170 1.67 3.34 1.67 100.00%
Sub Total 37.28 45.57 8.29 22.24%
192.168.38.210 5.59 4.66 -0.93 -16.64%
Total 42.87 50.23 7.36 17.17%
Comparison in Between
Individual Performance

20. 20
• Stations with Good Link Rate have Better Chance to have Better
WiFi Performance
0
1
2
3
4
5
6
7
8
9
10
110 120 130 140 150 160 170 210
Without With
Comparison in Between
Individual Performance

21. 21
0
2
4
6
8
10
12
14
16
18
20
110 120 130 160 150 140 170
Without With
• Stations with Good Link Rate have Better Chance to have Better
WiFi Performance
Comparison in Between
Individual Performance

22. 22
Without
AirTime Fairness
Performance / Total
With
AirTime Fairness
Performance / Total
192.168.38.110 1.60 3.73% 4.67 9.30%
192.168.38.120 7.34 17.12% 5.66 11.27%
192.168.38.130 8.51 19.85% 8.84 17.60%
192.168.38.140 3.84 8.96% 5.24 10.43%
192.168.38.150 7.14 16.66% 8.44 16.80%
192.168.38.160 7.19 16.77% 9.39 18.69%
192.168.38.170 1.67 3.90% 3.34 6.65%
Sub Total 37.28 86.96% 45.57 90.72%
192.168.38.210 5.59 13.04% 4.66 9.28%
Total 42.87 50.23
Comparison in Between
Individual Ratio

23. • Stations have More Equalized Performance
- Assuming they have the same hardware speed, more equalized
performance can be related to more equalized AirTime
23
With AirTime Fairness
210
9.26%170
6.64%
160
18.65%
150
16.76%
140
10.41%
130
17.76%
120
11.25%
110
9.28%
Without AirTime Fairness
210
13.35%
170
3.88%
160
16.70%
150
16.60%
140
8.93%
130
19.77%
120
17.05%
110
3.72%
Comparison in Between
Individual Ratio

24. 24
• Stations with Good Link Rate have Better Chance to have more
equalized AirTime
0
2
4
6
8
10
12
14
16
18
20
110 120 130 140 150 160 170 210
Without With
Comparison in Between
Individual Ratio

25. 25
0
2
4
6
8
10
12
14
16
18
20
110 120 130 160 150 140 170
Without With
Comparison in Between
Individual Ratio
• Stations with Good Link Rate have Better Chance to have more
equalized AirTime

26. 26
With 9.286.6518.6916.810.4317.811.279.3
110 120 130 140 150 160 170 210
Without 13.403.9016.7716.668.9619.8517.123.73
110 120 130 140 150 160 170 210
Comparison in Between
Individual Ratio
• Stations with Good Link Rate have Better Chance to have more
equalized AirTime

27. 27
Disable
AirTime
Fairness
Performance /
Total
Enable
AirTime
Fairness
Performance /
Total
192.168.38.110 1.60 3.73% 4.67 9.30%
192.168.38.120 7.34 17.12% 5.66 11.27%
192.168.38.130 8.51 19.85% 8.84 17.60%
192.168.38.140 3.84 8.96% 5.24 10.43%
192.168.38.150 7.14 16.66% 8.44 16.80%
192.168.38.160 7.19 16.77% 9.39 18.69%
192.168.38.170 1.67 3.90% 3.34 6.65%
Sub Total 37.28 86.96% 45.57 90.72%
192.168.38.210 5.59 13.04% 4.66 9.28%
Total 42.87 50.23
20
40
60
80
100
Without With
90.72
86.96
• Stations with Good Link Rate
Comprise More Parts in the
Total Performance
Comparison in Between
Group Ratio

28. 28
• 22.24% Improvement
Clients with 130Mbps Link Rate
Without
AirTime
Fairness
With
AirTime
Fairness
Difference
Improvem
ent
192.168.38.
110 1.60 4.67 3.07 191.88%
192.168.38.
120 7.34 5.66 -1.68 -22.89%
192.168.38.
130 8.51 8.84 0.33 3.88%
192.168.38.
140 3.84 5.24 1.4 36.46%
192.168.38.
150 7.14 8.44 1.3 18.21%
192.168.38.
160 7.19 9.39 2.2 30.60%
192.168.38.
170 1.67 3.34 1.67 100.00%
Sub Total 37.28 45.57 8.29 22.24%
192.168.38.
210 5.59 4.66 -0.93 -16.64%
Total 42.87 50.23 7.36 17.17%
20
25.2
30.4
35.6
40.8
46
Without With
45.57
37.28

29. 29
• -16.64% Deduction
Client with 65Mbps Link Rate
0
1.4
2.8
4.2
5.6
Without With
4.66
5.59
Without
AirTime
Fairness
With
AirTime
Fairness
Difference
Improvem
ent
192.168.38.
110 1.60 4.67 3.07 191.88%
192.168.38.
120 7.34 5.66 -1.68 -22.89%
192.168.38.
130 8.51 8.84 0.33 3.88%
192.168.38.
140 3.84 5.24 1.4 36.46%
192.168.38.
150 7.14 8.44 1.3 18.21%
192.168.38.
160 7.19 9.39 2.2 30.60%
192.168.38.
170 1.67 3.34 1.67 100.00%
Sub Total 37.28 45.57 8.29 22.24%
192.168.38.
210 5.59 4.66 -0.93 -16.64%
Total 42.87 50.23 7.36 17.17%

30. 30
• 17.17% Improvement
Overall
30
35.5
41
46.5
52
Without With
50.23
42.87
Without
AirTime
Fairness
With
AirTime
Fairness
Difference
Improvem
ent
192.168.38.
110 1.60 4.67 3.07 191.88%
192.168.38.
120 7.34 5.66 -1.68 -22.89%
192.168.38.
130 8.51 8.84 0.33 3.88%
192.168.38.
140 3.84 5.24 1.4 36.46%
192.168.38.
150 7.14 8.44 1.3 18.21%
192.168.38.
160 7.19 9.39 2.2 30.60%
192.168.38.
170 1.67 3.34 1.67 100.00%
Sub Total 37.28 45.57 8.29 22.24%
192.168.38.
210 5.59 4.66 -0.93 -16.64%
Total 42.87 50.23 7.36 17.17%

31. 31
• By Dropping the Packets (Shows as Tx Controlled Packets)
• Tx Controlled Packets Increased and Tx Airtime Decreased
How AirTime Fairness Works
34% 96
17% 44
14% 0
10% 47

32. • 210 Occupied Airtime (Convex)
32
JPerf Visualized the AirTime Fairness
• AP Controlled Airtime (Concave)

33. 33
Exception of AirTime Fairness

34. 34
• Client with Good Link Rate could Also Become Slower
Exception of AirTime Fairness
Without
AirTime Fairness
With
AirTime Fairness
Difference Individual
Improvement
192.168.38.110 1.60 4.67 3.07 191.88%
192.168.38.120 7.34 5.66 -1.68 -22.89%
192.168.38.130 8.51 8.84 0.33 3.88%
192.168.38.140 3.84 5.24 1.4 36.46%
192.168.38.150 7.14 8.44 1.3 18.21%
192.168.38.160 7.19 9.39 2.2 30.60%
192.168.38.170 1.67 3.34 1.67 100.00%
Sub Total 37.28 45.57 8.29 22.24%
192.168.38.210 5.59 4.66 -0.93 -16.64%
Total 42.87 50.23 7.36 17.17%

35. 35
• 36 Mbps only when
testing alone with
Full AirTime
- 130 can reach more
than 90Mbps
• 120 is the Slower PC
(e.g., Slower
Processor)
• Bottlenecks are not
only WiFi
Why 120 Become Slower

36. 36
• 120 is good at occupying AirTime (convex), but
it’s also slow
• AP Controlled the AirTime (concave)
• 120 Become Even Slower with Less AirTime
Why 120 Become Slower

37. 37
• Each Station has Better Chance to Acquire Airtime
Summary of AirTime Fairness
Theory
Without With

38. Summary of AirTime Fairness
38
• Improve Overall WiFi Performance, in Most Cases
- Stations with Good Link Rate get Increased
- Stations with Poor Link Rate get Decreased
• Hint: In Central AP Management >> Load Balance, set Force
Overload Disassociation as by single Strength

39. 39
• Not All Stations will Get Packets Dropped Dramatically
- Rob the Rich and Help the Poor (in Airtime, not in Performance)
Summary of AirTime Fairness
• 140 was Faster than 120, and it wasn’t Really Got “Controlled”

40. 40
Q&A