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Channel Selection and Management for 11ac

This article discusses the background, motivation, and channel access for 11n and 11ac. It explores the channel allocation and management for 80MHz and 40MHz operations, emphasizing non-overlapping and overlapping channel allocations. The primary channel allocation and efficient 80MHz channel allocation methods are presented, with examples and comparisons between non-overlapping and overlapping channel allocations.

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Channel Selection and Management for 11ac

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  1. Channel Selection and Management for 11ac Date: 2010-05-20 Authors:

  2. Outlines • Background and Motivation • 40MHz channel access for 11n • 80MHz channel access for 11ac • Channel Selection and Management for 80MHz channel bandwidth for 11ac • Channel allocation for 80MHz operation • The Primary channel allocation

  3. Background 1 • Up to 40MHz channel bandwidth which is composed of primary channel and secondary channel for 11n • Primary channel is located on the boundary over 40MHz channel bandwidth • Secondary channel is selected and indicated with the offset value relative to the primary channel • Above/Below the primary channel • No secondary channel

  4. Background 2 • 40MHz channel operation for 11n • CSMA/CA approach for the primary channel • The secondary channel has been idle for at least a PIFS interval prior to the expiry of backoff counter

  5. Motivation • Two OBSS scenarios in framework document • In-home entertainment application • Enterprise network • Support up to at least 80MHz channel bandwidth • The well-designated 80MHz channel allocation will be useful for efficient channel management of 11ac

  6. Channel Allocation for 80MHz operation • Non-overlapping channel allocation • Overlapping channel allocation

  7. Channel Allocation for 11ac 40MHz • 40MHz operation based on two adjacent 20MHz channels in the same way of 11n • The position of the primary/secondary channels has patterns • The permissible 40MHz channel allocation options are defined in terms of the designated primary/secondary channel • Non-overlapping channel allocation for each 40MHz channel

  8. Channel Allocation for 80MHz 1 • 80MHz operation with four 20MHz channels in a row based on the framework document • Option 1: non-overlapping channel allocation • Simple extension from 40MHz channel allocation • There may be limited numbers of 80MHz channel to support 80MHz operation • Two 80MHz channel allocations through 5.4GHz band

  9. Channel Allocation for 80MHz 2 • Option 2: overlapping channel allocation • Overlapping channel allocation by 40MHz shift • Four 80MHz channel allocations through 5.4GHz band • Overlapping channel allocation by 20MHz shift • Eight 80MHz channel allocations through 5.4GHz band • Increase the number of 80MHz allocation channels to be used

  10. Favorable circumstance with overlapping channel allocation 1 • OBSS circumstance • AP with 80MHz capability is surrounded by 40MHz capable APs in home entertainment system like the HD video streaming. • Non-overlapping channel allocation • According to OBSS scanning rule, 11ac 80MHz channels are recommended to share the same 2x20MHz channels • Time division multiplexing to support 80MHz channel operation • Overlapping channel allocation • It will be good to leave enough chances to allocate 80MHz channels • Throughput enhancement possibly with efficient channel utilities

  11. Favorable circumstance with overlapping channel allocation 2 • Unexpected interference circumstance • It will be useful in case of AP detecting some unexpected interference like a radar

  12. Concerns on overlapping channel allocation • It is assumed that CH3 and CH4 are shared 40MHz channels of both AP1 and AP2 according to the OBSS scanning rule of 11n • AP3 starts scanning idle channels to establish a 80MHz BSS newly • In case AP2 is hidden node in AP3 point of view • CH5 and CH6 are scanned as idle states • Unexpected interference on CH5 and CH6 between AP2 and AP3

  13. Comparison between non-overlapping and overlapping channel allocations 1 • 20/40MHz channel pairing for 80MHz operation in 5 GHz band • Available number of 80MHz channel depending on the channel allocation option

  14. Comparison between non-overlapping and overlapping channel allocations 2 • If weak points of overlapping channel allocation is significant, only non-overlapping channel allocation can be supported • Concern on the limited number of 80MHz channel • Need to increase the efficiency of non-overlapping 80MHz channel

  15. The Primary channel allocation

  16. 80MHz operation for 11ac • Support up to 80MHz channel bandwidth • The primary channel can be allowed to be set to any 20MHz subchannel over 80MHz channel bandwidth for some 11ac configurations • CSMA/CA approach for the primary channel • The rest of subchannels have been idle for at least a PIFS interval prior to the expiry of backoff counter

  17. Efficient 80MHz Channel Allocation • Non-overlapping channel allocation • It is assumed that 11ac AP/STA follow the OBSS scanning rule of 11n

  18. Example of 80MHz Channel Allocation • Overlapping channel allocation • Overlapping channel allocation by 40MHz shift

  19. Example of 80MHz Channel Allocation Overlapping channel allocation by 20MHz shift

  20. Summary • Follow the 40MHz channel allocation rule of 11n for 80MHz channel allocation • Non-overlapping channel allocation for 11ac • To increase the number of possible 80MHz channel allocation • Option 1 • Overlapping channel allocation can be one of good candidates • Option 2 • Non-overlapping channel allocation with any location of the primary channel over 80MHz channel • Open the possibility to select the primary channel which is allocated in the middle of entire channel bandwidth

  21. Straw Poll Do you support “the location of the Primary channel concept” described on page 16 by inclusion of the following section and text in the Tgac spec framework document 5 Coexistence R5.C:The Primary Channel may be designated to any 20MHz subchannel over 80MHz channel bandwidth, where Primary Channel designation is subject to co-existence(OBSS) rules yet to be defined. Yes No Abstain

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