Received signal strength

sankpal_manisha sankpal_manisha at indiatimes.com
Fri May 14 07:48:38 EDT 2004


Hi,
may be this is a simple question ....i want to know from where we can get the received signal strength?
is it part of received packet or it is the strength of the receiver with which it accepts packet?

by this what i mean whether the signal strength will flow in air with pacekt or not..
please clarify me if i am wrong..
Thanks in advance
manisha

"Eduard Garcia"<eduardg at mat.upc.es> wrote:
(please, I need help with this)

..so all power statistics returned by iwconfig/iwpriv or stored in
/proc/net/wlan0, etc. are in RSSI format which can be transformed to dBm
using dBmAdjust (multiplying?, dividing?...?). Am I wrong?

Now...how can I read the value of dBmAdjust and in general, any RID word?
More: the value of CommsQuality is referred to the quality of the signal
received with the AP I'm associated to?

And last: what do you suggest me to do to set the txpower? iwconfig ...
txpower...? iwpriv...writemif? With hostap 0.0.3 version and firmware 1.3.6
should I upgrade to
1.5.6 and install patch from http://www.jikos.cz/~jbohac/hostap/?



Please, I need a reference to RID words and mifs
(http://www.intersil.com/data/FN/FN4/FN4856/FN4856.pdf is broken)!! Or
somebody explain-me.



Sorry, but maybe this is a very-newbie question :((




Edu


----- Original Message ----- 
From: "Pavel Roskin"
To: "Christopher Dobbs"
Cc: "Anand S. Katti"
Sent: Monday, May 10, 2004 11:02 PM
Subject: Re: Received signal strength


> On Mon, 10 May 2004, Christopher Dobbs wrote:
>
> > I dont know about rssi but mabey this
> > http://www.geocities.com/vk3rtv/rfpower.html will help.
>
> No, we are talking about conversion between two logarithmic scales, dBm
> and the scale used in the card, known as RSSI (received signal strength
> information).  The table you posted the link to converts between dBm and
> Watts, a linear scale.
>
> Firmware 1.3.1 and newer has RID 0xfd51 (dBmCommsQuality), which is
> supposed to give the information in dBm.  HostAP uses RID 0xfd43
> (CommsQuality), which uses its own scale.  That scale was also changed in
> 1.3.1 firmware.
>
> Also, RID 0xfc46 (dBmAdjust) contains a constant that should be used for
> conversion between RSSI and dBm.
>
> If dBm values are needed, I suggest using dBmCommsQuality instead of
> CommsQuality.  Even then, I don't expect the data to be very accurate, but
> it's probably the best data the card can provide.
>
> I'm working on a patch for Orinoco driver that would use dBmCommsQuality
> if possible and provide reliable data in its absence.  Once I'm satisfied
> with it I plan to submit similar patch to HostAP.
>
> > > I have a Harris Semiconductor Prism 2.5 Wavelan Chipset.I want to
convert the
> > > parameter rxdesc->signal into dBm.
> > >Is  (rxdesc->signal-100) the right way to do it?.
>
> I don't think so.  You can print dBmCommsQuality and CommsQuality to the
> kernel log and try to find the dependency.  I think it should be linear.
>
> > > Will this conversion hold good even if I am using this card in managed
> > >mode and use an alternate driver like orinoco?
>
> I suggest that you don't trust drivers too much at this point.  There is
> some work that need to be done before you can trust the drivers, both
> Orinoco and HostAP.  Sorry for inconvenience.
>
> -- 
> Regards,
> Pavel Roskin
> _______________________________________________
> HostAP mailing list
> HostAP at shmoo.com
> http://lists.shmoo.com/mailman/listinfo/hostap

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