Changing 5Ghz transmit power option does not change actual transmit power on TP-Link Archer C6U?

Installing and Using OpenWrt
1

Hello, I am using OpenWrt 21.02.0 r16279-5cc0535800 and it seems that changing transmit 5Ghz transmit power in LuCI does not have any effect on signal strength or quality. For example, Tx-power 5 dBm (3mW) shows pretty much the same signal strength as 20 dBm (100 mW). I check signal strength with WifiInfoView and in LuCI. When I change tx-power, iwinfo does show correct info.

2.4Ghz seems to work fine and signal strength does change with tx-power change. Changing 2.4Ghz tx-power does not affect 5Ghz tx-power. I also tried changing channels, changing tx-power to other options, like 10dBm, and even other regions. Wondering whether other people experience the same problem.

2

Hello,

if I understand correctly(any experienced fellows pls correct me), the "signal" field in iwinfo is the router's RX quality, therefore, changing router TX power should not affect this value when all other parameters stay unchanged.

To see the effect of increasing router's TX power, one should check the client side. On my laptop, when I increase router's TX power, there is visible increase in signal quality. There are many tools available, such as
WifiInfoView by nirsoft, NetSpot, or just eye balling the signal bar if it is significant enough.

If you want to increase the router's RX signal quality shown by iwinfo(again, if I'm wrong pls correct me), you will need to increase the client's TX power, and/or installing a higher gain antenna on your router, given all other variables unchanged(channel interference, distance, antenna polarization(angle), etc....)

Hope it helps.

With Metta

3

Thanks for reply! When I change transmit power, the change is only cosmetic. It does not affect actual signal strength. This is signal strength with transmit power set to 20dBm: https://imgur.com/MSS3KwD, iwinfo: https://imgur.com/6agixuj.
This one set to 10dBm: https://imgur.com/yh2btdX, iwinfo: https://imgur.com/P7oEVZn. No difference at all, I can even set it to 0dBm. The signal strength will stay the same.

Here is 2.4Ghz for example. 20dBm: https://imgur.com/1HWLqtJ, 10dBm: https://imgur.com/mJyASAA. This one looks like it's supposed to be.

4

I can can confirm this on Archer C6 v3.2 as well.

See more details about this issue at MediaTek MT76 Ignoring Wi-Fi TX Power Configuration

It seems to be a driver bug.

5

Thanks for confirming it. Now I'm wondering whether we can do anything to get this problem fixed?

6

A fix is required. There are already two bugs filed, but no developer is working them.

I’m not sure but they issue may be in the mt76 driver which is upstream (developed outside OpenWRT).

But I understand that OpenWRT devs usually contribute to upstream. So the fix depends either from some OpenWRT dev to investigate and fix the issue, or wait for the fix to come from upstream devs.