WiFi Tx power question

[Rick Stevens]

On 09/18/2014 05:23 PM, jd1008 issued this missive:
> # lspci | grep -i wifi
> 0c:00.0 Network controller: Intel Corporation WiFi Link 5100
> dmesg | grep -i iwlwifi
> [   10.019366] iwlwifi 0000:0c:00.0: Detected Intel(R) WiFi Link 5100
> AGN, REV=0x54
>
> dmesg also  shows
> [  266.827254] wlan0: Limiting TX power to 36 (36 - 0) dBm as advertised
> by 00:0d:67:6a:5a:19
>
> iwconfig wlan0
> $ iwconfig wlan0
> wlan0     IEEE 802.11abgn  ESSID:"attwifi"
>            Mode:Managed  Frequency:2.462 GHz  Access Point:
> 00:0D:67:6A:5A:19
>            Bit Rate=72.2 Mb/s   Tx-Power=15 dBm
>            Retry short limit:7   RTS thr:off   Fragment thr:off
>            Power Management:off
>            Link Quality=35/70  Signal level=-50 dBm
>            Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
>            Tx excessive retries:0  Invalid misc:20   Missed beacon:0
>
> So, reason I am asking is that I would like to increase Tx power to 30dBm
> due to poor connectivity with the hotspot router.
>
> I tried
> # iwconfig wlan0 txpower 30dBm
> {7917-jd at localhost}# echo $?
> 0
> # iwconfig wlan0
> wlan0     IEEE 802.11abgn  ESSID:"attwifi"
>            Mode:Managed  Frequency:2.462 GHz  Access Point:
> 00:0D:67:6A:5A:19
>            Bit Rate=72.2 Mb/s   Tx-Power=15 dBm
>            Retry short limit:7   RTS thr:off   Fragment thr:off
>            Encryption key:off
>            Power Management:off
>            Link Quality=35/70  Signal level=-50 dBm
>            Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
>            Tx excessive retries:0  Invalid misc:20   Missed beacon:0
>
> So, iwconfig is not setting Tx power. Not sure if this is a limitation
> of the wifi card or a bug in the wifi driver or if a bug in iwconfig.

Uh, I don't think you can go above 15dBm. Try "iwconfig wlan0 txpower 
10" and see if it dropped it to 10dBm. I bet it does (it does to me).
If it does, then iwconfig is doing its job. Bump it back up to 15 and
start playing with antenna locations on the access point. Your poor
connectivity is more likely due to bad incoming signal strength and in
that case boosting your transmission isn't going to help.
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- Rick Stevens, Systems Engineer, AllDigital    ricks at alldigital.com -
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