Tx Rate Chosing

Anand S. Katti askatti at ece.iisc.ernet.in
Sun May 23 15:01:07 EDT 2004

Hello All,

	Kindly clear doubt of Probe Requests.

Since probe request generation is handled in firmware I do not know


a) At what rate is this Probe Request Sent by the STA ?
b) What initial rate does it choose ? in sendine probe Request ?
c) In supported rates field does it include the STD specifed BASIC RATES
only ? or does it actually calculates the SIR(if passive scanning) and
includes the supported rates based on the SIR valueof the rxd beacon ?

Any Answers will be helpful.


On Sat, 22 May 2004, Anand S. Katti wrote:

> >> When HostAP receives the Probe requests,
> >It does not.. This is handled in firmware..
> >>       0-  does it fix the supported rates in the probe response based
> >> on the SIR value ?
> >>       0-  does it fix the Tx Rate in the Association Response based on
> >> the SIR value of the received Associate Request ?
> >No.
> Then How does the Firmware handle these probe requests and association
> requests ?
>  I mean if the hostap is in sta mode, at what tx rate does the F/W send
> the probe request/asso req ? does the f/w chose the tx rate by default ?
> as highest 11Mbps or based on any other criteria ?
> As far std says Generally control/mgmt frames are sent at 1 or 2 Mbps.
> In Prism Driver Programmers manual F/w vers 2.3 its mentionde that f/w
> keeps updated withthe channel info that contains signal and noise related
> info, where else this SNR is used other than in AutoFallback Algo ?
> Kindly answer.
> Regards,
> --Anand

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