5

I want to be able to get the received signal strength indication from my computer's wifi interface, ideally as expressed in dBm.

This article explains what I am after.

  • That table doesn't tell anything from the receiver's side. – ott-- Jun 6 '15 at 20:56
  • What OS are you using? I'm guessing Arch based on the avatar you chose, but please be explicit. Also, which wifi card is in the machine? Or just as good, which wifi driver are you using? – Warren Young Jun 6 '15 at 20:57
  • Regarding the edit I just made, I want to explain why I removed all the information about audio: decibels are just a way of expressing a ratio of two measurements; decibels are not in any way specific to audio. In this case, it is a measure of radio power in milliwatts. – Warren Young Jun 6 '15 at 20:58
  • @ott--: While RSSI is properly measured at the WAP, 802.11 provides ways for that measurement to be communicated back to the wifi device. That information may propagate up to a layer that you can see from user space. It's a good question. – Warren Young Jun 6 '15 at 21:03
  • @WarrenYoung You guessed right, I'm using Arch Linux. I see you ask for the wifi card in my machine, but is it also possible to get this information with software (like iw)? – linuscl Jun 7 '15 at 6:03
5

There are 2 commands you can use that can give you the RSSI value.

You can first cat /proc/net/wireless file and get the results there. This uses the least amount of resources of the 2 methods

$ /bin/cat /proc/net/wireless

Inter-| sta-|   Quality        |   Discarded packets               | Missed | WE
 face | tus | link level noise |  nwid  crypt   frag  retry   misc | beacon | 22

wlo1: 0000   70.  -31.  -256        0      0      0      0     25        0

The other alternative is to use iwconfig/iwlist (my wireless interface is wlo1, so replace with the appropriate interface name)

$ /sbin/iwconfig wlo1
wlo1      IEEE 802.11  ESSID:"COD PUBLIC WIRELESS"
          Mode:Managed  Frequency:5.745 GHz  Access Point: 40:E3:D6:63:BC:B0
          Bit Rate=866.7 Mb/s   Tx-Power=22 dBm
          Retry short limit:7   RTS thr:off   Fragment thr:off<br>
          Power Management:on
          Link Quality=67/70  Signal level=-43 dBm
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:27   Missed beacon:0



$ iwlist wlo1 scanning

wlo1      Scan completed :
          Cell 01 - Address: 40:E3:D6:63:BC:B0
                    Channel:149
                    Frequency:5.745 GHz
                    Quality=70/70  Signal level=-38 dBm
                    Encryption key:off
                    ESSID:"COD PUBLIC WIRELESS"
                    Bit Rates:12 Mb/s; 24 Mb/s; 36 Mb/s; 48 Mb/s; 54 Mb/s
                    Mode:Master
                    Extra:tsf=00000075dccaa121
                    Extra: Last beacon: 81624ms ago
                    IE: Unknown: 0013434F44205055424C494320574952454C455353
                    IE: Unknown: 010598B048606C
                    IE: Unknown: 030195
                    IE: Unknown: 2D1AEF091BFFFFFFFF00000000000000000000000000000000000000
                    IE: Unknown: 3D1695050400000000000000000000000000000000000000
                    IE: Unknown: 4A0E14000A002C01C800140005001900
                    IE: Unknown: 7F080100080000000040
                    IE: Unknown: BF0CB1798B33AAFF0000AAFF0000
                    IE: Unknown: C005019B000000
                    IE: Unknown: DD180050F2020101800003A4000027A4000042435E0062322F00
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2

The iwlist and iwconfig are part of wireless tools which is now deprecated.

You can list your devices with iw dev

You can get the rssi value of your current link when using WiFi station as follows (wlan0 is the usual default wi-fi device, but depends on the driver and configuration):

$ iw dev wlan0 link
Connected to 9c:4e:20:c8:ee:9e (on wlan0)
    SSID: CORP1
    freq: 5240
    RX: 7306266 bytes (6124 packets)
    TX: 776491 bytes (4117 packets)
    signal: -75 dBm
    tx bitrate: 39.0 MBit/s MCS 4

To list available WiFi signals:

$ ip link set wlan0 up
$ iw dev wlan0 scan
...
BSS 9c:4e:20:c8:ee:9d(on wlan0)
TSF: 0 usec (0d, 00:00:00)
freq: 5240
beacon interval: 102 TUs
capability: ESS Privacy RadioMeasure (0x1011)
signal: -75.00 dBm
last seen: 765 ms ago
SSID: CORP1
...
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