Re: [STDS-802-11-TGM] Oh, *that* energy detect?!
--- This message came from the IEEE 802.11 Task Group M Technical Reflector ---
Hello Mark,
OK, thanks, so bonus question, arguably not in scope of this group, but anyway...
If CCA-ED is only for the 3 GHz band in the USA (a.k.a. 11y), why does
11ac/D4.0 have something about it (22.3.19.5.2 CCA sensitivity for operating
classes requiring CCA-ED)?
Actually one extra point of clarification:
> [CS/CCA and CCA-ED discussion] all this just
> feeds into the overall CS mechanism, by combining with NAV, TX status and PHY-CCA
I thought PHY-CCA (7.3.5.11) was the output of the thing which combines
CS/CCA and (where appropriate) CCA-ED? Are you saying there is a different
PHY-CCA which is completely separate from CS/CCA and CCA-ED?
Mark
P.S.:
> I'd say yes to all the above, except I think you meant the _fifth_ being
> "the behavio(u)r ..."
Yup, sorry!
--
Mark RISON, Systems Architect, Wi-Fi English/Esperanto/Français
Samsung Cambridge Solution Centre Tel: +44 1223 434600
Innovation Park, Cambridge CB4 0ZT Fax: +44 1223 TBCTBC
ROYAUME UNI WWW: http://www.samsung.com/uk
> -----Original Message-----
> From: Hamilton, Mark [mailto:Mark.Hamilton@xxxxxxxxxxx]
> Sent: 17 November 2012 05:18
> To: m.rison@xxxxxxxxxxx
> Cc: STDS-802-11-TGM@xxxxxxxx
> Subject: RE: Oh, *that* energy detect?!
>
> Mark,
>
> That all sounds correct, yes. Note that the term "CS/CCA" is new as of OFDM (it was just called "CCA"
> before that, but was clearly a CS and/or ED mechanism then, per the "CCA Mode x" tables I showed you
> this week). And, yes, CCA-ED is a separate thing, optional and required per regulatory domain rules.
> If you think you can simplify it, I'll look forward to your proposal. Don’t forget that all this just
> feeds into the overall CS mechanism, by combining with NAV, TX status and PHY-CCA, so there is more
> mess within the MAC, too.
>
> CCA-ED is discussed explicitly in DSSS, HR/DSSS and OFDM PHYs. PHYs after that do, in my opinion,
> talk about still requiring the earlier clause PHYs' CCA pretty clearly. So, yes, I think by
> implication, CCA-ED is expected for all PHYs.
>
> I would have said that CCA-ED threshold is in a MIB variable for 'future/unforeseen' flexibility.
> Like, a new reg domain comes along that needs a different (lower power?) level, so an external entity
> can force this, while the Standard catches up. Since the hard-coded level is in Annex D, it seems
> clear that this is "subject to change" if the regulations change, also. (In fact, there was
> discussion a few months ago about moving all the operating class parameters into ANA, so they could
> change rapidly/frequently without needing to amend the Standard. I'm not sure what happened to that
> idea.) I have no idea about the other ones, except maybe someone decided all the above should apply
> to all the thresholds, but too late to really fix everything up cleanly. This all does sound ripe for
> a D1.0 comment (including the ANA part).
>
> > - What's the difference between "CCA-ED", "CCA-EnergyDetect", "CCA-Energy Detect", "CCA energy
> detect" and "CCA-EDBehavior"?
> > Are the second and fourth just typos for the third, and the first just an abbreviation of the third;
> the fourth being the behavio(u)r associated
> > with regdoms which require CCA-ED?
> I'd say yes to all the above, except I think you meant the _fifth_ being "the behavio(u)r ..." I
> would also clarify that the fifth is the keyword for use in the Annex D table, only, also - so it
> isn't the behavior generically (that is CCA-Energy Detect), it is the keyword that tells you which
> domains require that behavior.
>
> Mark
>
> -----Original Message-----
> From: Mark Rison [mailto:m.rison@xxxxxxxxxxx]
> Sent: Friday, November 16, 2012 1:48 PM
> To: Hamilton, Mark
> Cc: STDS-802-11-TGM@xxxxxxxx
> Subject: Oh, *that* energy detect?!
>
> Hello Mark,
>
> So let me see if I've now grokked this:
>
> - CS/CCA includes both a "sniff the PHY header" mode and a "do energy detect" mode. The latter
> asserts CCA if the power is at least -62 dBm (assuming 20 MHz). These modes are both mandatory
>
> - There's a *separate* "do energy detect" mode called CCA-ED which is the same as the "do energy
> detect" mode of CS/CCA except the threshold is -72 dBm. This mode is only used in some regdoms,
> namely the 3 GHz band in the USA (a.k.a. 11y)
>
> If so, this is a very confusing way to describe it for a simple MAC person like me and I will raise a
> comment on D1.0!
>
> Bonus questions:
>
> - Is CCA-ED only required of the OFDM (11a) PHY? Or is it also required for PHYs which incorporate
> the OFDM PHY by reference (using the San Antonio wording)? What about 11n in GF mode, should this
> ever be done in a regdom where CCA-ED is mandatory?
>
> - Why is the CCA-ED threshold in a MIB variable (dot11OFDMEDThreshold)? The other energy detect
> mode's threshold is not in any variable (or is this dot11EDThreshold (but this is only for the DSSS
> PHY) or even dot11TIThreshold (deprecated and in the dot11PhyOFDMTable though its description seems
> generic enough)?)
>
> - What's the difference between "CCA-ED", "CCA-EnergyDetect", "CCA-Energy Detect", "CCA energy detect"
> and "CCA-EDBehavior"?
> Are the second and fourth just typos for the third, and the first just an abbreviation of the third;
> the fourth being the behavio(u)r associated with regdoms which require CCA-ED?
>
> Mark
>
> --
> Mark RISON, Systems Architect, Wi-Fi English/Esperanto/Français
> Samsung Cambridge Solution Centre Tel: +44 1223 434600
> Innovation Park, Cambridge CB4 0ZT Fax: +44 1223 TBCTBC
> ROYAUME UNI WWW: http://www.samsung.com/uk
>
>
>
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