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Evaluation of the saturation of the 5GHz band

Evaluation of the saturation of the 5GHz band. Date: 2010-07-13. Content. The following modes have already been accepted by 11ac 20MHz, 40MHz, 80MHz (mandatory) 160MHz (optional)

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Evaluation of the saturation of the 5GHz band

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  1. Evaluation of the saturation of the 5GHz band Date: 2010-07-13

  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: 100 104 108 112 116 120 124 128 132 140 136 56 64 52 60 36 40 44 48 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 0 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 required equivalent bandwidth 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 10000 simulation scenarios samples and average the results for fixed total multi-BSS equivalent bandwidth. • We plot the percentage of usage of each bandwidth and the potential BSS saturation 1 2 3 4 0 5 6 7 8 9 10 11 12

  6. 30 23 100 104 108 112 116 120 124 128 132 140 136 56 64 52 60 36 40 44 48 Simulation process • Once each BSS has its equivalent bandwidth requirements • 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 requirements and select the best channel allocation • non overlapping 80MHz channel plan is used 0 1 2 3 4 5 6 7 8 9 10 11 12 Slot 3 Slot 1 Slot 4 Slot 2

  7. 0 1 2 3 4 5 6 7 8 9 10 11 12 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 BSS1

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

  9. 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 load » 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

  10. Simulation results: Better modes for > 80MHz (2/4) • Impact on the saturation of the band of different modes • « contiguousonly » 160 MHz mode: helpssomeBSSs to satisfytheirthroughputrequirements but the saturation limitiskeptunchanged 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 actuallyhelps push forward the saturation of eachBSSsfrom a total eqbandwidth of 730 instead of 550MHz 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. 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 3.1.2 120 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 3.1.2 120 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 802.11-10/0385r1, Mar. 2010 [2] Cariou, L. and Benko, J., Gains provided by multichannel transmissions, IEEE 802.11-10/0103r1, Jan. 2010 [3] TGaa OBSS background, Graham Smith, IEEE 802.11-09/0762r0, 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

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