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[STDS-802-11] More Coexistence SC questions for Sept 2022 (submissions and thought requested)

--- This message came from the IEEE 802.11 Working Group Reflector ---

G’day  802.11 WG,

 

Over the last few years, ETSI BRAN has been very important in promoting “good” coexistence between multiple technologies in the 5 GHz band. The various drafts and revisions of the Harmonised Standard EN 301 893 (5 GHz) have had a significant influence, not only within Europe, but also on the sharing mechanisms adopted by 3GPP for LAA and NR-U globally, mechanisms that are very much aligned with the way Wi-Fi has operated so successfully for the last 20+ years.

 

For most of the period, EN 301 893 has allowed Wi-Fi systems to use its traditional PD/ED @ -82/-62 dBm “listen” mechanism, as part of an EDCA based LBT with exponential backoff (and limited length TxOps). For many years, EN 301 893 has enabled this behaviour by referring directly to the IEEE 802.11 standard. Essentially, European requirements were satisfied by doing it the “IEEE 802.11 way”. This approach become less acceptable in recent years because it was perceived to be less “technology neutral”. The underlying issue is that LAA/NR-U systems cannot use the “IEEE 802.11 way”. Instead, they used ED-only @ -72 dBm to “listen”.

 

Some participants in ETSI BRAN were very unhappy that Wi-Fi systems were allowed to satisfy the European requirements merely by compliance with the IEEE 802.11 standard. The arguments were causing progress to define the next revision to EN 301 893 to slow significantly. Eventually, it the interests of making any progress, a compromise was struck whereby only 802.11a/n/ac/ax systems were deemed to satisfy the European rules by compliance with the IEEE 802.11 standard. All other systems, including 802.11be systems, are required in the next revision of EN 301 893 to use ED-only @ -72 dBm.

 

So now we have a problem. How should the 802.11 standards be modified (if at all) to allow 802.11be systems to operate well under the requirements defined in EN 301 893? There are several choices:

  • Do nothing, which effectively means 802.11be systems will need to use PD/ED at -82/-72 dBm in Europe
    • May result in 802.11be systems have less access than 802.11ax systems
  • Refine 802.11 so that 802.11be systems can use PD <  -72 dBm and ED @ -72 dBm in Europe (and maybe elsewhere too)
    • Probably the best approach, at least until we learn more about coex in real environments
  • Persuade ETSI BRAN to go back to allowing the “IEEE 802.11 way”
    • Unlikely to be successful in the short term at least
  • Persuade ETSI BRAN to allow ED-only @ -62dBm
    • The 3GPP community is keen on this and many in the Wi-Fi community are not … because it gives NR-U/LAA a significant advantage of Wi-Fi  (as shown by 3GPP simulations)
    • Some in the Wi-Fi community are keen on this … partially because it is a workable solution (no constraints on 802.11) if one assumes NR-U/LAA are market failures (which is not yet knowable)

 

At the Coex SC meeting in July 2022,  these options were highlighted, along with associated questions. There were few answers in July, but a consensus on the most viable option will help direct the future work of the Coex SC, and the 802.11 WG more generally. This e-mail is requesting members to be ready to discuss viable options at the next Coex SC meeting in Sept 2022. An even better outcome would be submissions from multiple members in relation to these options. At the end of the discussions, I then plan to run a series of straw polls to better understand the perspectives of the membership and so set a platform for future progress.

 

Please contact me if you plan to make a submission or if you have any thoughts on these options …

 

Andrew Myles

 

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