Date: Thu, 28 Sep 2006 08:52:12 -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: <451BEFAC.4040502@errno.com> In-Reply-To: <d3ea75b30609280808w60db7af1i1719a5787d48bf20@mail.gmail.com> References: <d3ea75b30609270710u19d01124n6cae749a943bde99@mail.gmail.com> <451AECA0.7000103@errno.com> <d3ea75b30609280808w60db7af1i1719a5787d48bf20@mail.gmail.com>
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Eduardo Meyer wrote: > Thank you Mr Leffler for this explanation. Honestly I did not know > about those tools. Very interesting, useful and some curious (say, > number of associations denied by wlan acl) information, which I > believe I will be able to produce some logs of it with audit support. > > But I did not find any "signal" information nor any value which looks > like dBm > > # athstats -i ath0 > 4 watchdog timeouts > 549821 tx management frames > 7 tx frames discarded prior to association > 1744404 tx stopped 'cuz no xmit buffer > 15 tx linearized to cluster > 97625 tx failed 'cuz too many retries > 9069518 long on-chip tx retries > 422577 tx frames with no ack marked > 62850632 tx frames with short preamble > 1700110 tx frames with an alternate rate > 24280171 rx failed 'cuz of bad CRC > 1 rx failed 'cuz frame too large > 62560031 rx failed 'cuz of PHY err > 4211566 OFDM timing > 101667 OFDM restart > 58199442 CCK timing > 47356 CCK restart > 31931664 beacons transmitted > 109058 periodic calibrations > rssi of last ack: 24 > 417831 switched default/rx antenna > Antenna profile: > [1] tx 31753038 rx 33886147 > [2] tx 31594701 rx 33711543 > > # wlanstats -i ath0 > 1509703 rx discard 'cuz dup > 335650 rx frame ssid mismatch > 2314 rx deauthentication > 377 rx disassociation > 4959 rx discard 'cuz acl policy > 1068 tx failed for no node > 3 active scans started > 142 nodes timed out inactivity > > Note that I am acting in hostap mode. Looks like you're not running HEAD or RELENG_6 or your system is not update recently. Sam > > On 9/27/06, Sam Leffler <sam@errno.com> wrote: >> 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 >> > >
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