802.11 RSSI value displayed from ifconfig(8)

[Sam Leffler]

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 at 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
>>
> 
>