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> References: <d3ea75b30609270710u19d01124n6cae749a943bde99@mail.gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
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. Sam
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?451AECA0.7000103>