Re: [STDS-802-11-TGM] Do STAs inherit or aggregate PHYs?
--- This message came from the IEEE 802.11 Task Group M Technical Reflector ---
Hello Mark,
> [Just one PHY per STA]
OK, so let me see what the implications of all this seem to be, putting
aside anything 11ad might or might not have done to the architecture:
- You cannot have a STA with both an 11g PHY and an 11a PHY
(because a STA can only have one PHY)
- You can, however, have a STA with an 11n PHY operating both in the
2G4 band and the 5G band (because this is one PHY, just operating
in different channels), even though this includes the functionality
of 11g and 11a PHYs, and might in theory only transmit 11g or 11a
PPDUs
- The 11g PHY has the following non-CCA-ED ED requirement (i.e. not
the 11y regulatory requirement, the mandatory requirement of all STAs),
from 19.4.7:
"a valid signal with a signal power of –76 dBm or greater at the receiver antenna connector is
present at the start of the PHY slot"
- The 11b PHY has the following different ED requirement, from
17.4.8.5:
"If a valid High Rate signal is detected during its preamble within the CCA window, the ED threshold
shall be less than or equal to –76 dBm for TX power > 100 mW; –73 dBm for 50 mW < TX power
≤ 100 mW; and –70 dBm for TX power ≤ 50 mW."
N.B.: You are only required to detect HR/DSSS signals, not
(LR/)DSSS signals, right?
- The 802.11-1997 PHY has the following different ED requirement, from
16.4.8.5:
"The ED threshold shall be ≤ –80 dBm for TX power > 100 mW, –76 dBm for 50 mW < TX power ≤
100 mW, and –70 dBm for TX power ≤ 50 mW."
While I'm at it:
- What's a "PHY slot"?
- How does the receiver know the transmitter's power?
- The ERP does not have to do CCA on non-HR DSSS PPDUs? 19.1.3 says
"The ERP has the capability to detect ERP and Clause 17 preambles whenever
a CCA is requested" -- no "and Clause 16". You can't wave your hands
around to say Clause 17 preambles includes Clause 16 preambles because
a few lines up it says "The ERP has the capability to decode all Clause 16
and Clause 17 PLCPs" -- not just "Clause 17 PLCPs".
- How does 20.3.21.5.1's "CCA sensitivity requirements for non-HT PPDUs
in the primary channel are described in 18.3.10.6 and 19.4.7" work for
the ED part of (CS/)CCA? Isn't the point of ED that you don't know
exactly what's there, just that there's something there?
Sorry if I'm just a MAC bull wrecking the PHY china shop!
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
> -----Original Message-----
> From: Hamilton, Mark [mailto:Mark.Hamilton@xxxxxxxxxxx]
> Sent: 17 November 2012 05:30
> To: m.rison@xxxxxxxxxxx
> Cc: STDS-802-11-TGM@xxxxxxxx
> Subject: RE: Do STAs inherit or aggregate PHYs?
>
> Mark,
>
> I see the wording you mean, but to me that wording does exactly what I thought. That is, when the ERP
> PHY builds on DSSS/CCK, for example, that means you could view/model this as the ERP PHY "containing"
> the DSSS/CCK PHY, or as the ERP PHY being implemented by including all the implementation of the
> DSSS/CCK PHY as an integral part of the ERP PHY. But, either way, it isn't "a STA with multiple PHYs"
> in the sense of those PHYs being side-by-side and accessible to the MAC. The MAC sees one PHY. What
> that PHY does internally is not visible or of interest to the MAC.
>
> Of course, 11ad complicates all this. Note, though, that this allows multiple MACs to share a single
> PHY. In this case, we have multiple STAs but only one PHY between them. It carefully never talks
> about allowing more than one PHY accessed by a given MAC entity.
>
> Mark
>
> -----Original Message-----
> From: Mark Rison [mailto:m.rison@xxxxxxxxxxx]
> Sent: Friday, November 16, 2012 1:51 PM
> To: Hamilton, Mark
> Cc: STDS-802-11-TGM@xxxxxxxx
> Subject: Do STAs inherit or aggregate PHYs?
>
> Hello Mark,
>
> You asked me to explain why it's not clear to me whether the ERP includes the DSSS PHYs' functionality
> or adds to them (and ditto the HT PHY and the HR/DSSS PHY w.r.t. their predecessors).
>
> I think the problem is wording like:
>
> - "The ERP builds on [DSSS/CCK]" in 19.1. "builds on" to me suggests to me that the foundations are
> owned by someone else -- think of it as freehold v. leasehold!
>
> - "[HR/DSSS] builds on [DSSS]" in 17.1 (ditto)
>
> - "In addition to [Clause 20], an HT STA shall be capable of transmitting and receiving frames that
> are compliant with [Clause 18 and/or 17 and 19]" in 20.1. Note the HT *STA* is capable, but is this
> done by the HT *PHY* or by having multiple PHYs?
>
> 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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