# calculating transfer rate

Eduard GV eduardgv
Mon May 21 09:59:56 PDT 2007

```Hi,

Maybe this old thread will help:
http://lists.shmoo.com/pipermail/hostap/2005-July/011005.html

Regards,

Edu

2007/5/21, Varga D?vid <varga.david at duvinet.hu>:
> Hi!
>
> Although, I was aware of the things you mentioned (: I know how the tx rate
> depends on SNR and BER theoretically.
> The thing I want to find is that in practice where is it calculated or how
> is it set in the hostap driver (in managed mode).
>
> Thanks,
> David
>
>
> -----Original Message-----
> From: hostap-bounces+varga.david=duvinet.hu at shmoo.com
> [mailto:hostap-bounces+varga.david=duvinet.hu at shmoo.com] On Behalf Of
> ahuguet at cttc.es
> Sent: Monday, May 21, 2007 1:32 PM
> To: hostap at shmoo.com
> Subject: Re: calculating transfer rate
>
> Hi David,
>
> the transmission rate depends, indeed, on the signal to noise ratio, and
> the desired BER (bit error rate) that has to be achieved.
> The less SNR, the less transmission rate to keep a given BER.
>
> As to where you can find the speed rate, I'll try giving you an answer,
> although I've not tested that myself.
>
> In the first place, the physical layer header contains information
> regarding the transmission rate the payload is being sent at.
> I'd say that you can get that information in the hostap driver code.
> At the reception part, under void hostap_80211_rx()
> there's an argument that is passed, rx_stats.
> rx_stats->rate should contain the speed you're seeking.
>
> Keep in mind that the number won't be 1 for 1Mbps, but 10. That's how the
> standard 802.11b sets that field. So, expect to find 10,20,55,110.
>
> Hope that's of help.
>
> > Hello!
> >
> > Could anyone please tell me about the mechanism the driver uses to
> > calculate
> > the transfer rate for each packet?
> >
> > Does it depend on the recent received packet's signal and noise ratio?
> >
> > Is it even controlled by the driver or the firmware? If by the driver,
> > where
> > can I find it? (:
> >
> > Does the AP control the clients which speed they should use? If so, how
> > does
> > it work in ad-hoc mode?
> >
> >
> >
> > Thanks for the help!
> >
> > David
> >
> >
> >
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>
>
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