Howto Check Wireless link quality in Ubuntu Linux

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Iwspy is used to set a list of addresses to monitor in a wireless network interface and to read back quality of link information for each of those. This information is the same as the one available in /proc/net/wireless : quality of the link, signal strength and noise level.This information is updated each time a new packet is received, so each address of the list adds some overhead in the driver.

Note that this functionality works only for nodes part of the current wireless cell, you can not monitor Access Points you are not associated with (you can use Scanning for that) and nodes in other cells. In Managed mode, in most case packets are relayed by the Access Point, in this case you will get the signal strength of the Access Point. For those reasons this functionality is mostly useful in Ad-Hoc and Master mode.

The iwspy command provides statistics on the quality of the link between your NIC and another wireless device on the network. It doesn't run all the time; you have to activate iwspy on your interface first. When not activated, iwspy gives a "no statistics to collect" error message.You can try the following commands

sudo iwspy wlan0

wlan0: No statistics to collect

Activation requires you to specify the target IP address and the wireless NIC interface through which it can be found.

sudo iwspy wlan0

If you use the iwspy command without the IP address it provides WLAN statistics with a typical/reference value against which it can be compared. In the example that follows the signal is considered fairly strong, with a 64/92 quality value versus a typical 36/92 value, but it could be weak by the historical values on your network. It's good to check this from time to time for fluctuations.

sudo iwspy wlan0

eth0 Statistics collected:
00:09:5B:C9:19:22 : Quality:0 Signal level:0 Noise level:0
Link/Cell/AP : Quality:64/92 Signal level:-51 dBm Noise level:-149 dBm (updated)
Typical/Reference : Quality:36/92 Signal level:-62 dBm Noise level:-98 dBm

To switch off iwspy monitoring, use the following command

sudo iwspy wlan0 off

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4 Responses

  1. dileep says:

    hi, when i use iwspy what i get is this
    wlan0 Interface doesn’t support wireless statistic collection
    any insight how i can correct this

    this is iwconfig status
    wlan0 IEEE 802.11g ESSID:off/any
    Mode:Managed Frequency:2.412 GHz Access Point: Not-Associated
    Bit Rate:54 Mb/s
    RTS thr=1600 B Fragment thr=2346 B
    Power Management:off
    Link Quality:0 Signal level:0 Noise level:0
    Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
    Tx excessive retries:0 Invalid misc:0 Missed beacon:0

  2. David says:

    Hello, I’m totaly frech with Linux, so I guess I do something worng, becous when I press Alt+F2 and get the “run command” and write it, press enter, nothing more happens, what am I downing wrong? :S

  3. gvsa123 says:

    i just saw this How to and gave it a try but got this:

    wlan0 Interface doesn’t support wireless statistic collection
    what does that mean?

  4. mike says:

    David: you need ctl-alt-f2

    alt-f2 is like the windows start->run option

    gvsa123: this means (i think) your nic doesn’t support permiscuous(?) mode…i think

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