1. Evaluation of the saturation of the 5GHz band
Month Year
doc.: IEEE yy/xxxxr0
Evaluation of the saturation of the 5GHz band
Date:
John Doe, Some Company

2. Content The following modes have already been accepted by 11ac
20MHz, 40MHz, 80MHz (mandatory)
160MHz (optional)
The first aim of that work is to evaluate the robustness to the saturation of the 5GHz band, assuming the current bandwidth modes
The second one is to evaluate whether it is interesting or not to define other modes like non contiguous 120MHz (80+40MHz), assuming this band saturation criteria

3. Simulation scenarios
We extended the simulation tool presented in [1] by applying the probability calculation on different OBSS, taking into account the sharing of the band between neighbouring BSSs.
The simulation tool in [1] allows to calculate the equivalent bandwidth (bandwidth that you would have 100% of the time) for all bandwidth mode based on probability calculation assuming the load of all channels in the 5GHz band.
The objective is to evaluate the impact of different bandwidth modes on the saturation of the 5GHz band. 30 23
Example: 36 40 44 48 52 56 60 64
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104
108
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140
Bandwidth mode used: 80MHz
Equivalent bandwidth: 40MHz
Busy channel

4. Simulation scenarios: Detached Houses
Simulation scenario as described in [3]
Simulation layout 1 2 3 4 5 6 7 8 9 10 11 12 12
BSS

5. Simulation process
For each simulation scenario sample, we randomly associate to each BSS a equivalent bandwidth target between 0 and B=80MHz (bandwidth that you would be able to use 100% of the time) and calculate the channel allocation that satisfies the requirement of each BSS one after another
We ran simulation scenarios samples and average the results for fixed total multi-BSS equivalent bandwidth.
We plot the percentage of usage of each bandwidth mode and the potential BSS saturation 1 2 3 4 5 6 7 8 9 10 11 12

6. Simulation process Once each BSS has its equivalent bandwidth target
We incrementaly evaluate each BSS channel allocation
Step 1: look at its channel load configuration (case of 19 channels in Europe)
Step 2: calculate the equivalent bandwidth obtained with all bandwidth modes and select the lowest bandwidth that satisfies its equivalent bandwidth target and select the best channel allocation
non overlapping 80MHz channel plan is used 30 23 56 52 48 44 40 36 64 60
120
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136 1 2 3 4 5 6 7 8 9 10 11 12
Slot 1
Slot 2
Slot 3
Slot 4

7. Simulation process
Step 3: update the channel load configuration of each BSS that can be interfered (ex: BSS 0 interfers BSS1, 5 and 6)
(Note that the load is calculated so that the equivalent bandwidth is satisfied
A load degradation of 0.05 is applied in case of overlap.)
Step 4: re-iterate for next BSS
BSS0 1 2 3 4 5 6 7 8 9 10 11 12
BSS1

8. Simulations
We compare the bandwidth mode repartition between BSSs vs total equivalent bandwidth for different configurations using BSS equivalent bandwidth targets randomly selected between 0 and 80MHz
BSSs configuration 1
20MHz
-40MHz
80MHz
BSSs configuration 2
20MHz
-40MHz
80MHz
160MHz contiguous only
BSSs configuration 3
20MHz
-40MHz
80MHz
120MHz non contiguous
BSSs configuration 2 bis
20MHz
-40MHz
80MHz
160MHz with non
contiguous capability

9. Simulation results: Better modes for > 80MHz (1/4)
Month Year
doc.: IEEE yy/xxxxr0
Simulation results: Better modes for > 80MHz (1/4)
Impact on the saturation of the band of different modes
80MHz only BSS: due to the saturation, after a total « equivalent bandwidth» of 530MHz the throughput needs from BSSs are not fulfilled
Saturation limit
Saturation
configuration 1
BSSs modes
20MHz
-40MHz
80MHz
80MHz
40MHz
20MHz
case of 19 available channels in Europe
Total equivalent bandwidth
John Doe, Some Company

10. Simulation results: Better modes for > 80MHz (2/4)
Impact on the saturation of the band of different modes
« contiguous only » 160 MHz mode: helps some BSSs to satisfy their throughput by reaching their bandwidth target but the saturation limit is kept unchanged
Saturation
configuration 2
BSSs modes
20MHz
-40MHz
80MHz
160MHz
contiguous only
160MHz
80MHz
40MHz
40MHz
20MHz
case of 19 available channels in Europe
Total equivalent bandwidth

11. Simulation results: Better modes for > 80MHz (2/4)
Impact on the saturation of the band of different modes
« Non contiguous capable » 160 MHz mode: this mode actually helps push forward the saturation of each BSSs from a total equivalent bandwidth of 730 instead of 530MHz with 80MHz only
Saturation
20MHz
configuration 2 bis
BSSs modes
20MHz
-40MHz
80MHz
160MHz
non contiguous
capable
160MHz
contiguous 160MHz
Saturation
80MHz
80MHz
160MHz
40MHz
40MHz
20MHz
case of 19 available channels in Europe
20MHz
Total equivalent bandwidth

12. Simulation results: Better modes for > 80MHz (3/4)
Impact on the saturation of the band of different modes
120MHz mode (80+40 MHz): this mode is the best as it allows to completly fulfill the throughput requirements from all BSSs by enabling them to reach their bandwidth target.
Saturation
120MHz
configuration 3
BSSs modes
20MHz
-40MHz
80MHz
120MHz
contiguous 160MHz
Saturation
80MHz
80MHz
160MHz
40MHz
40MHz
40MHz
20MHz
case of 19 available channels in Europe
20MHz
Total equivalent bandwidth

13. Simulation results: Better modes for > 80MHz (4/4)
160MHz (80+80MHz) mode with non contiguous capability is not only interesting to reach very high throughput, it is actually very useful to ensure that a BSS will get 80MHz in case of saturation.
However, this mode suffers from its low probability to access the channel in dense environment
An intermediate frequency mode at 120MHz (80+40) is actually the best compromise as it enables to reach 80MHz in even denser environments by benefiting from a better probability to access the channel

14. Conclusion
Bandwidth modes higher than 80MHz are actually interesting to ensure that you will get 80MHz (equivalent bandwidth) even in dense environment
For that purpose, 120MHz mode is the most efficient (better than 160MHz)
Of course, further investigations should be made to evaluate the impact of the overlapping of non-primary channels on the respect of the QoS. Some protection mechanisms in case of QoS may be needed.
TGac should define an additional 120MHz (80+40MHz) non contiguous mode
For 160MHz, “non contiguous 160MHz” present significant gains compared to “contiguous only 160MHz”
For 80MHz, non contiguous 80MHz (40+40MHz) is under investigation

15. Strawpoll #1
Do you support adding the following section and item into the specification framework document, 11-09/0992?
Section MHz PHY Transmission
R3.1.2.A: The draft specification shall include support for 120 MHz PHY transmission.
Yes:
No:
Abstain:

16. Strawpoll #1
Do you support adding the following section and item into the specification framework document, 11-09/0992?
Section MHz PHY Transmission
R3.1.2.B: The draft specification shall include support for non-contiguous 120 MHz PHY transmission, whose frequency spectrum consists of two segments, transmitted using one 11ac 80 MHz channel including the primary channel and one 11ac 40 MHz channel, possibly non-adjacent in frequency.
Yes:
No:
Abstain:
Slide 16

17. References
[1] Cariou, L. and Christin, P., 80MHz and 160MHz channel access modes, IEEE /0385r1, Mar. 2010
[2] Cariou, L. and Benko, J., Gains provided by multichannel transmissions, IEEE /0103r1, Jan. 2010
[3] TGaa OBSS background, Graham Smith, IEEE /0762r0, May 09

18. Back up

19. Calculation of the equivalent bandwidth
Assume we have 4 aggregated channels, each with a specific probability Pi of being idle.
We can calculate the probability to transmit at 20, 40, 60 or 80MHz
And calculate the equivalent bandwidth (bandwidth that you would be able to use 100% of the time)
P1, P2, P3, P4
Primary

20. Calculation of the equivalent bandwidth for defer/80 and defer/40/80
P40
P80
Non contiguous capable
Defer/40/80
P80 = P1*P2*P3*P4
P40 = P1*P2*(1-(P3*P4)) …
Contiguous only
Defer/80
P80 = P1*P2*P3*P4
Equivalent bandwidth
Equivalent bandwidth