Tx Rate Chosing

Eduard Garcia eduardg at mat.upc.es
Tue May 25 14:02:12 EDT 2004

As far as I'm concerned, the IEEE 802.11 standards left open the mechanisms
to select PHY rate. There are many algorithms proposed, e.g. # packet
retransmissions -> decrease rate; # successful transmissions -> increase
rate. What I don't know is where the decission is taken (firmware? driver?)
or if you are able to change the rate selection policy.

I'm really interested on how it is done when we have Prism and hostap...


----- Original Message ----- 
From: "Anand S. Katti"
To: hostap
Sent: Tuesday, May 25, 2004 6:06 PM
Subject: Re: Tx Rate Chosing

> Hi,
> >> Is information exchanged about supported rates during Association is
> >>being
> >> used in eventually settling to an initial TX rate for the connection ?
> >>
> >> If yes, then what initial rate they settle on ?
> >Yes, the maximum rate supported by both ends is tried first.
> Thanks a LOT LOT for the reply.
> Suppose the STA is far away from the client such that it can only support
> 2Mbps, so it sends the Asso Req with supported rates as {1,2}.
> Then does the AP set the initial rate (tx_rate) to 2Mbps:
> a) just by seeing the supported_rates of the Asso.Req alone ?
> b) or it also sees the SIR of the received Asso.Req signal ?
> >Yes, the maximum rate supported by both ends is tried first.
> Its too much to ask, but still could you please point me to the
> Line No. of the Source file where this decesion is made ?
> Thanks Again,
> Anand

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