eap Mailing List: Re: EAP WG Last Call on Network Discovery and SelectionProblem Document

[Jouni Malinen (j]

On Tue, Mar 27, 2007 at 09:52:22AM -0700, Bernard Aboba wrote:
> BTW, I did some traces, and 170 octet Beacons are actually quite common 
> (Apple Airport Extreme has Beacons of this size, for example).
> 
> If you add up 1360 bits at 1 Mbps (1360us), 144 us for preamble, 48 us for 
> PLCP, 10 us for
> SIFS, 50 ms for DIFS, and 1200 usec for CWmin/2 slot times, and multiple by 
> 98 Beacons/sec, you get 27.6 percent.
> 
> 200 octet beacons would give 30 percent.  So I don't think that the Velayos 
> paper is that far off.

Sure, it is possible that beacons are longer. Though, I would assume
that this would be more likely with 802.11g/a APs while the paper was
talking about 802.11b which is unlikely to include many of the new IEs
in beacon frames. Anyway, if the question is on how many "modern APs"
one can have on a single channel, this kind of channel time usage may
indeed be getting more likely since I would expect most 802.11g APs to
continue beaconing at 1 Mbps rate.

-- 
Jouni Malinen                                            PGP id EFC895FA