Date: Wed, 27 Sep 2006 14:26:56 -0700 From: Sam Leffler <sam@errno.com> To: Eduardo Meyer <dudu.meyer@gmail.com> Cc: stable@freebsd.org Subject: Re: 802.11 RSSI value displayed from ifconfig(8) Message-ID: <451AECA0.7000103@errno.com> In-Reply-To: <d3ea75b30609270710u19d01124n6cae749a943bde99@mail.gmail.com>
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Eduardo Meyer wrote: > Hello, I would like to convert RSSI to dBm (in fact I would love if > ifconfig cound display SNR in dBM), so I would like to know if this > formula is any right: > > /* Calculate the RSSI Value */ > V_RSSI = 3.0 * (RSSI_VAL/1024); > RSSI_dBM = (int8_t) ((-50.0 * V_RSSI) - 45.5); > > And if there are any other tools which can help me finding out signal > stenght, when I am acting as an access point. ifconfig reports rssi as whatever the driver provided. The intent is that it be a signed value relative to the current noise floor (both in dBm). If you look at the output of wlanstats (tools/tools/net80211/wlanstats) or, for ath devices, athstats (tools/tools/ath/athstats) you will see the default displays show "signal" which is rssi+noise-floor in dBm. The main issue(s) right now are that the net80211-driver api does not pass noise floor up so it can be reported to user apps and drivers reports rssi+nf in varying units. athstats doesn't have that issue since it queries the driver directly (hence it's display has a reasonable noise floor). It's on my todo list to push signal-related data up properly and fix ifconfig so it displays a proper signal strength in the normal status display. The issue of units is more difficult as converting data for some devices to dBm can be tricky. Samhome | help
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