Re: [STDS-802-11-TGM] Oh, *that* energy detect?!
--- This message came from the IEEE 802.11 Task Group M Technical Reflector ---
Hello Mark,
> > 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)?
> [MAH] Don’t know. Presumably an oversight that they wouldn’t need it.
> Or, perhaps, provided just in case 11ac is ever extended to the 3 GHz band?
Is it possible to extend 11ac to the 3G6 band in the USA without also
extending 11n to it too? Note 11n has (AFAICT) nothing about CCA-ED,
so cannot be used in the 3G6 band in the USA.
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 434601
ROYAUME UNI WWW: http://www.samsung.com/uk
> -----Original Message-----
> From: ***** IEEE stds-802-11-tgm List ***** [mailto:STDS-802-11-TGM@xxxxxxxx] On Behalf Of Hamilton,
> Mark
> Sent: 27 November 2012 05:31
> To: STDS-802-11-TGM@xxxxxxxxxxxxxxxxx
> Subject: Re: [STDS-802-11-TGM] Oh, *that* energy detect?!
>
> --- This message came from the IEEE 802.11 Task Group M Technical Reflector ---
>
> In line, below….
>
>
>
> Mark
>
>
>
> -----Original Message-----
> From: Mark Rison [mailto:m.rison@xxxxxxxxxxx]
> Sent: Monday, November 19, 2012 11:16 AM
> To: Hamilton, Mark
> Cc: STDS-802-11-TGM@xxxxxxxx
> Subject: RE: Oh, *that* energy detect?!
>
>
>
> 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)?
>
> [MAH] Don’t know. Presumably an oversight that they wouldn’t need it. Or, perhaps, provided just in
> case 11ac is ever extended to the 3 GHz band?
>
>
>
> 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?
>
> [MAH] Sorry, poor wording on my part. I meant “by combining NAV, TX status and PHY-CCA” (without the
> “with”). Yes, PHY-CCA is the combination of CS/CCA and CCA-ED. Then, the MAC combines this with NAV
> and TX state. Sorry about the confusion.
>
>
>
> 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 <http://www.samsung.com/uk>
>
>
>
>
>
> > -----Original Message-----
>
> > From: Hamilton, Mark [mailto:Mark.Hamilton@xxxxxxxxxxx <mailto:Mark.Hamilton@xxxxxxxxxxx> ]
>
> > Sent: 17 November 2012 05:18
>
> > To: m.rison@xxxxxxxxxxx <mailto:m.rison@xxxxxxxxxxx>
>
> > Cc: STDS-802-11-TGM@xxxxxxxx <mailto: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 <mailto:m.rison@xxxxxxxxxxx> ]
>
> > Sent: Friday, November 16, 2012 1:48 PM
>
> > To: Hamilton, Mark
>
> > Cc: STDS-802-11-TGM@xxxxxxxx <mailto: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 <http://www.samsung.com/uk>
>
> >
>
> >
>
> >
>
>
>
>
>
>
>
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