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FS#3983 - TX Power 2.4GHZ Stuck #8977

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openwrt-bot opened this issue Aug 20, 2021 · 1 comment
Open

FS#3983 - TX Power 2.4GHZ Stuck #8977

openwrt-bot opened this issue Aug 20, 2021 · 1 comment
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@openwrt-bot openwrt-bot commented Aug 20, 2021

AidanPR16:

I'm having a problem with TXPower with my MediaTek 2.4GHz radio on my R6220 Netgear unit flashed with the latest version of OpenWRT, changing the TX power down to 1 dBm all the way down from 20 has no effect on range or RX power seen by devices. The 5GHz radio does not have this problem, and changing the Tx power has a significant effect on both real world range and signal in dBm. I have tried downgrading software with no luck. Any ideas?

  • On both 18.06 and 19.07, tried rolling back.
  • Tried reflashing to new OS with no luck
  • Netgear R6220
  • 2.4GHz Radio with TX Power Issues: MediaTek MT7603E 802.11bgn
  • 5GHz Radio That Works Fine: MediaTek MT76x2E 802.11acn

Let me know if I can provide more info.

  • Aidan
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@openwrt-bot openwrt-bot commented Sep 18, 2021

dsouza:

I can confirm this issue also with the 5Ghz radio on a TP-Link Archer C6 3.2 (MT7621 + MT7603EN 2.4Ghz + MT7613BEN 5Ghz) running a snapshot build (r17525-a46fa5c3a7):

Linux ap2 5.4.145 #0 SMP Thu Sep 16 05:59:50 2021 mips GNU/Linux

The issue seems to be with the M76 driver which is completely ignoring the "TX Power" set via LuCI and UCI. I am saying the issue seems to be the Wi-Fi driver because UCI and iwinfo everything seems to be OK.

See the example below. I've set the TX Power to 0dbm for testing purposes, and UCI and iwinfo correctly show the value I've configured:

root@ap2:~# uci show wireless.radio1
wireless.radio1=wifi-device
wireless.radio1.type='mac80211'
wireless.radio1.path='1e140000.pcie/pci0000:00/0000:00:01.0/0000:02:00.0'
wireless.radio1.band='5g'
wireless.radio1.htmode='VHT80'
wireless.radio1.country='PA'
wireless.radio1.channel='100'
wireless.radio1.cell_density='0'
wireless.radio1.txpower='0'

root@ap2:# iwinfo wlan1 info
wlan1 ESSID: "dshome5ghz-tst"
Access Point: xx:xx:xx:xx:C8:40
Mode: Master Channel: 100 (5.500 GHz)
Center Channel 1: 106 2: unknown
Tx-Power: 0 dBm Link Quality: 24/70
Signal: -86 dBm Noise: -92 dBm
Bit Rate: 234.0 MBit/s
Encryption: WPA2 PSK (CCMP)
Type: nl80211 HW Mode(s): 802.11nac
Hardware: 14C3:7663 14C3:7663 [MediaTek MT7613BE]
TX power offset: none
Frequency offset: none
Supports VAPs: yes PHY name: phy1
root@ap2:
#

However the 0dBm configuration above has no effect on TX Power at all.

With TX Power configured at 0 dBm for the 5Ghz radio in the example above, Wi-Fi signal should be very weak and should work only on the same room and close to the access point.

However as seen below the signal strength measured with a laptop located about 10 meters away from the access point with a brick wall between the laptop and the access point and the wi-if signal strength is still strong. This is the same level as if TX Power is at 22dBm (driver default level), so in fact the TX Power configuration is not working:

ubuntu@ubuntu:~$ iwconfig wlp2s0
wlp2s0 IEEE 802.11 ESSID:"dshome5ghz-tst"
Mode:Managed Frequency:5.5 GHz Access Point: xx:xx:xx:xx:C8:40
Bit Rate=26 Mb/s Tx-Power=22 dBm
Retry short limit:7 RTS thr:off Fragment thr:off
Power Management:on
Link Quality=42/70 Signal level=-68 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:30 Missed beacon:0

I've experimented other TX Power levels, and none configuration has any effect on OpenWRT TX Power. I am not sure if this is an OpenWRT bug or if it is in fact a MT76 driver issue to be reported upstream by OpenWRT devs.

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