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Backward compatibility of 11aj with 11ad

Backward compatibility of 11aj with 11ad. Date: 2013-03-17. Authors:. This presentation tackles the requirement of backward compatibility of 11aj with 11ad devices in the 60 GHz band An 11aj PAR requirement Only way to prevent thrashing of the 60 GHz band with incompatible devices

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Backward compatibility of 11aj with 11ad

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  1. Backward compatibility of 11aj with 11ad Date: 2013-03-17 Authors: Multiple co-authors

  2. This presentation tackles the requirement of backward compatibility of 11aj with 11ad devices in the 60 GHz band • An 11aj PAR requirement • Only way to prevent thrashing of the 60 GHz band with incompatible devices • Backward compatibility has proven to be key to the success of 802.11n/g/a and it will not be different for 11aj • Here we revisit the principle of backward compatibility and bring up a proposal on how this can be accomplished by 11aj Purpose Multiple co-authors

  3. The 11aj PAR states: “The amendment shall maintain backward compatibility with 802.11ad when it operates in the 59-64 GHz frequency band.” • The principle of backward interoperability is well established in 11ac/n/a/g/b • Legacy STAs do not interfere with frame exchanges using next-gen PPDUs between next-gen STAs, and next-gen STAs do not interfere with frame exchanges using legacy PPDUs between legacy STAs. As a result, legacy and/or next-gen STAs are allowed to coexist with each other. • This same principle should apply to 11aj! The principle of backward compatibility Multiple co-authors

  4. From 9.23.1 within (9.23 Protection mechanisms): “These protection mechanisms cause a STA that is a potential interferer to defer any transmission for a known period of time. When these mechanisms are used, non-ERP STAs do not interfere with frame exchanges using ERP PPDUs between ERP STAs and non-HT STAs do not interfere with frame exchanges using HT PPDUs between HT STAs. As a result, non-ERP and/or non-HT STAs are allowed to coexist with ERP and/or HT STAs.” See also (9.7 Multirate support) References from 802.11-2012 Multiple co-authors

  5. In slide 6 of 11/13-0175r0, 3 coexistence “modes” of 802.11n are presumed, labeled: Legacy mode, Mixed mode and Greenfield mode • Then, the following proposal is made based on the authors’ understanding of the 11n Greenfield mode: • “Exclusive Mode • No backward compatibility to 802.11ad device” • This is a misunderstanding: • 11n does not have modes: 11n has PHY formats (legacy, HT-MM, HT-GF) with associated usage rules to ensure backwards compatibility • Greenfield “mode” does NOT imply that there is no backward compatibility • Greenfield allows data transmissions in a BSS to be restricted to a given mode (e.g., HT), but backward compatibility still exists • Use of HT-GF format is subject to an array of restrictions to minimize backwards compatibility issues. E.g., review the HT Protection, Nongreenfield HT STAs Present and OBSS Non-HT STAs Present fields in the HT Operation element, and associated normative text Comments on 11/13-0175r0 Multiple co-authors

  6. Mechanisms must be defined to ensure that 11aj is backward compatible with 11ad • Some proposed mechanisms: • Support of 11ad MCS0, which is used to transmit several basic frames (see 9.7) • 11aj STAs shall follow the same frame transmissions rules during the BTI, A-BFT and ATI portions of the beacon interval that are applicable to DMG STAs • During the DTI, 11aj stations may use 11aj specific modes after ensuring appropriate protection (e.g., similar to HT-GF protection rules in 802.11n) • Additional mechanisms might still be needed to meet the backward compatibility requirement of the 11aj PAR Applying the principle of backward compatibility to 11aj: a proposal Multiple co-authors

  7. There are possibly several alternatives for 11aj STAs to use 11aj specific modes during the DTI • For example, to support the smaller BW channel desired by 11aj, possible extensions can include: • Extending the Extended Schedule element to signal the channel BW • Extending the RTS/DMG CTS frames to signal the channel BW (e.g., transmitting DMG CTS-to-self) • Extending the frames used during the SLS to also signal the channel BW • Other? Under this proposal (slide 6), how could 11aj STAs use 11aj specific modes? Multiple co-authors

  8. Backward compatibility of 11aj with 11ad is critical not only because it is in the 11aj PAR, but also because it: • Ensures equitable and fair use of the 60 GHz band • Leverages all the implementation efforts made into 11ad • Increases the chances of 11aj success in the marketplace • We propose that 11aj follows the same principle of backward compatibility that is incorporated in other .11 amendments • The backward compatibility proposal made in this presentation follows this principle Summary Multiple co-authors

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