80MHz and 160MHz channel access modes Month Year doc.: IEEE 802.11-yy/xxxxr0 80MHz and 160MHz channel access modes Date: 2010-03-18 Authors: John Doe, Some Company

Multichannel non contiguous transmissions Interests of multi-channel Multi-channel is an efficient solution to increase the probability to transmit at 80MHz and ensure an increase of single-user throughput compared to 11n. In [1], we presented the gains that can be obtained with the most favored solution: synchronous non contiguous We concluded that this solution provided a clear increase of the probability to reach the desired bandwidth In this presentation, we discuss the need for contiguous or non contiguous modes for 80MHz and 160MHz transmissions Slide 2

11n 40MHz channel access - 20MHz bandwidth unit BWU - Classical contention on the primary channel (BWU1) - CCA during PIFS on the secondary channel (BWU2) BWU1 Primary Channel AIFS + backoff Ack BWU2 time Secondary Channel Ack time PIFS 30 23 17 Primary Slide 3

How does 11n work? 11n is a contiguous case and the transmitter can Transmit at 40MHz when primary and secondary are idle or at 20MHz when primary channel only is idle or defer when the primary is busy  Defer/20/40 mode Transmit at 40MHz when both channels are idle or defer  Defer/40 mode Because of implementation issues, only the second mode is used: Defer/40 mode Slide 4

11ac 80MHz channel access - 20MHz bandwidth unit BWU as in 11n - Classical contention on the primary channel (BWU1) - CCA during PIFS on the secondary, tertiary, quaternary channel (BWU2,3,4) BWU1 Primary Channel AIFS + backoff Ack BWU2 time Secondary Channel Ack BWU3 time Tertiary Channel PIFS Ack BWU4 time Quaternary Channel PIFS Ack time PIFS SIFS 30 23 17 Primary Slide 5

11ac 160MHz channel access - 40MHz bandwidth unit instead of 20MHz bandwidth unit BWU - Classical contention on the primary BWU - CCA during PIFS on the secondary, tertiary, quaternary BWU BWU1 Primary BWU AIFS + backoff Ack time Ack time BWU2 Secondary BWU Ack time Ack time BWU3 Tertiary BWU PIFS Ack time Ack time BWU4 Quaternary BWU PIFS Ack time Ack time PIFS SIFS 30 23 17 Slide 6

11ac channel access: 80MHz example non contiguous case (use of 2 segments or more) BWU1 Primary Channel AIFS + backoff Ack BWU2 time Secondary Channel Ack time PIFS Segment 2 BWU3 Tertiary Channel Ack time BWU4 Quaternary Channel PIFS Ack time PIFS SIFS 30 23 17 Primary Slide 7

11ac channel access: 160MHz example non contiguous case (use of 2 segments or more) Contiguous (1 segment) Non contiguous (2 or more segments) Non contiguous mode also incorporates in this definition the case of contiguous segments 30 23 17 Segment 1 Segment 2 30 23 17 30 23 17 Slide 8

How would 11ac work with contiguous (1 segment) or non contiguous (2 segments)? For contiguous case, we will be able to fill up the subcarriers between every channels For non contiguous case, we won't be able to use the subcarriers between the two segments 4% gain for 40MHz, ~6% for 80MHz, ~4% for 160MHz 40MHz 40MHz 80MHz 108 108 80MHz ~230 80MHz 80MHz ~230 ~230 160MHz 160MHz Bandwidth ~478 Subcarriers Slide 9

How would 11ac work with contiguous (1 segment) or non contiguous (2 segments)? For contiguous case, we will be forced to do as in 11n Transmit at 80MHz (160 with 160MHz case) when all channels are idle or defer  Defer/80 mode: static selection of channels as in 11n and with a lower probability of transmission  Defer/160 mode: static selection of channels as in 11n and with a much lower probability of transmission For non contiguous case, we will have the degree of freedom provided by the 2 segments Transmit at 80MHz (160 with 160MHz) when all channels are idle or transmit at 40MHz (80 with 160MHz) is first segment only is idle or defer  Defer/40/80 mode: dynamic selection of channels (80MHz case)  Defer/80/160 mode: dynamic selection of channels (160MHz case) Slide 10

Simulation results We use the simulation plateform as presented in [1] Equivalent bandwidth vs density curves The equivalent bandwidth is the bandwidth that you could have 100% of the time The density is the number of channels in the 5GHz band which are interfered with a fixed load (here 0,9) We compare contiguous (1 segment) and non contiguous (2 segments) for 80MHz and 160MHz For contiguous: defer/80 mode (or defer/160 mode for 160MHz) For non contiguous: defer/40/60/80 mode (or defer/80/120/160 mode for 160MHz) Slide 11

Performance results: 80 MHz, load 0.9 Non contiguous (2 segments) provides very important gain over contiguous (1 segment) Even with the throughput degradation due to unfilled subcarriers between segments of 6%, as soon as for a density of 6 Slide 12

Performance results: 160 MHz, load 0.9 Non contiguous (2 segments) provides very important gain over contiguous (1 segment) Even with the throughput degradation due to unfilled subcarriers between segments of 4%, as soon as for a density of 2 Slide 13

Performance results: As soon as for a density of 2 with 160MHz, contiguous mode will be almost inefficient This density of 2 can easily be reached because of 11a/n/ac OBSS, Radars: especially static wheather radars which are located in one of the two available contiguous 160MHz band, Channel reserved for high QoS: like bit intolerant Slide 14

Conclusions Non contiguous (2 segments) provides significantly better results than contiguous (1 segment), even with the throughput degradations due to unfilled subcarriers between segments For 160MHz, it's not worth allowing contiguous transmission. We should only use non contiguous (2 segments). For 80MHz, we should define contiguous (1 segment) and non contiguous (2 segments of 40MHz) modes Slide 15

References [1] Cariou, L. and Benko, J., Gains provided by multichannel transmissions, IEEE 802.11-10/0103r1, Jan. 2010 Slide 16