Archer C7 v5 Poor Wireless Performance

tdim · January 26, 2020, 11:55am

Hi Team,

I recently switched from DD-WRT to OpenWrt on my TP-Link Archer C7 v5 (AC1750). Everything is fine, except the Wi-Fi performance. On the 5 GHz network:

Using DD-WRT, I was able to download files at ~60 MB/s over the internet. SpeedTest was around 500 Mbps, which is the limit of my ISP contract.
Using OpenWrt, downloads never go above 16 MB/s and SpeedTest is around 100 Mbps over AC Wi-Fi. If I use Ethernet, I get 500 Mbps back to normal.

I tried to install iperf on the router to monitor the wireless link, here is the result:

➜ ~ iperf -c 192.168.1.1
------------------------------------------------------------
Client connecting to 192.168.1.1, TCP port 5001
TCP window size:  129 KByte (default)
------------------------------------------------------------
[  4] local 192.168.1.50 port 53735 connected with 192.168.1.1 port 5001
[ ID] Interval       Transfer     Bandwidth
[  4]  0.0-10.0 sec   370 MBytes   310 Mbits/sec

➜ ~ iperf -c 192.168.1.1 -t 20
------------------------------------------------------------
Client connecting to 192.168.1.1, TCP port 5001
TCP window size:  129 KByte (default)
------------------------------------------------------------
[  4] local 192.168.1.50 port 53771 connected with 192.168.1.1 port 5001
[ ID] Interval       Transfer     Bandwidth
[  4]  0.0-20.0 sec   736 MBytes   308 Mbits/sec

Here is my 5 GHz wireless config on the router:

config wifi-device 'radio0'
	option type 'mac80211'
	option hwmode '11a'
	option path 'pci0000:00/0000:00:00.0'
	option htmode 'VHT80'
	option legacy_rates '0'
	option channel '36'
	option txpower '23'
	option noscan '1'
	option country 'FR'

config wifi-iface 'default_radio0'
	option device 'radio0'
	option network 'lan'
	option mode 'ap'
	option key '******'
	option ssid '******'
	option encryption 'psk2+ccmp'

Here are the wireless link information on my computer:

Router: 192.168.1.1
Security: WPA2 Personal
Channel: 36, 5 GHz, 80 MHz
Country: FR
RSSI: ~ -53 dBm
Noise: ~ -94 dBm
RX/TX: Between 780 Mbps and 1300 Mbps
PHY mode: 802.11ac
MCS Index: 9
NSS: 2

I tried OpenWrt 18.06.X, 19.07.0, and the latest snapshot (Jan 26 2020), the problem is still the same.

Does anyone can help me? Do not hesitate to ask me if you need more information.
Thank you very much!

Thomas

erdoukki · January 26, 2020, 1:55pm

Have you activate the WMM mode ?

wmm-mode

tdim · January 26, 2020, 5:42pm

The WMM mode is enabled. If I disable it, iperf tests drop to ~20 Mbps.

Gingernut · January 27, 2020, 6:21am

You could try changing the ath10k-qca988x-ct wireless driver for it's htt variant as some suggest. You could also test the non ct driver but you would probably need to compile a build yourself for that.

opkg remove ath10k-qca988x-ct
opkg install ath10k-qca988x-ct-htt
reboot

tdim · January 27, 2020, 7:44am

Hi Gingernut, thank you for your feedback.

I tried to remove qca988x-ct and to install qca988x-ct-htt, performances dropped again. SpeedTest was about 50 Mbps and iperf:

➜  ~ iperf -c 192.168.1.1
------------------------------------------------------------
Client connecting to 192.168.1.1, TCP port 5001
TCP window size:  129 KByte (default)
------------------------------------------------------------
[  4] local 192.168.1.50 port 58604 connected with 192.168.1.1 port 5001
[ ID] Interval       Transfer     Bandwidth
[  4]  0.0-10.0 sec  55.2 MBytes  46.2 Mbits/sec

Then I tried to remove qca988x-ct-htt and kmod-ath10k-ct, and to install qca988x and kmod-ath10k, performances increased, but not significantly. SpeedTest was around 120 Mbps, and iperf:

➜  ~ iperf -c 192.168.1.1
------------------------------------------------------------
Client connecting to 192.168.1.1, TCP port 5001
TCP window size:  129 KByte (default)
------------------------------------------------------------
[  4] local 192.168.1.50 port 58879 connected with 192.168.1.1 port 5001
[ ID] Interval       Transfer     Bandwidth
[  4]  0.0-10.0 sec   194 MBytes   162 Mbits/sec

Gingernut · January 27, 2020, 11:40am

A WDS 5GHz wireless link at about 6 meters apart behind a thin brick wall and running the latest qca988x-ct-htt variant (ver 10.1-ct-8x-__fH-022-b0e1b7cd).

~ iperf3.exe -c 192.168.1.2 -t 20
Connecting to host 192.168.1.2, port 5201
[  4] local 192.168.1.242 port 55490 connected to 192.168.1.2 port 5201
[  4]   0.00-20.00  sec   618 MBytes   259 Mbits/sec                  receiver

Channels from 100 to 140 seem to have higher tx power output depending on the radio country code that's set.

tdim · January 27, 2020, 6:50pm

Changing the channel and increasing the TX Power to the maximum allowed doesn't help unfortunately

Gingernut · January 27, 2020, 8:40pm

I'm not overwhelmed by the 5GHz wireless performance on my units either, I think the transfer speed should be much higher.

One thing we discovered is that it's not the wireless driver's fault.

Gingernut · January 28, 2020, 10:09am

BTW what OpenWRT build are you on?

tdim · January 28, 2020, 11:29am

OpenWrt SNAPSHOT r12126-016339ba42, from Jan 26.

Gingernut · January 29, 2020, 10:30am

Maybe test an older build from the 18.06.05 branch as there have been complaints about wireless performance linked to the latest hostapd update.

tdim · January 29, 2020, 12:18pm

Yea, that's why I'm using the Jan 26 snapshot, because hostapd got fixes on Jan 24 (https://bugs.openwrt.org/index.php?do=details&task_id=2679).

Unfortunately the problem has the same last year, with the 18.06.05 version.

tdim · February 2, 2020, 2:19pm

The issue is still the same with the latest 19.07.1 version unfortunately.

tdim · February 11, 2020, 8:04am

I manage to solve the issue by enabling SFE using this custom build : https://github.com/gwlim/openwrt-sfe-flowoffload

Does anyone have an explanation?

Is there a way to compile the SFE module myself without depending on an external build? Seems to be pretty hard to do...

Thanks!

Router · March 7, 2020, 12:01am

You don't need that anymore on the latest official 19.07 builds. I get better performance on the official build than those custom builds.

tdim · March 7, 2020, 6:55pm

You mean, the 19.07.2 version?

Edit: I upgrade to 19.07.2, nothing changes.

Tatikoma · May 9, 2020, 7:34pm

Custom build with SFE worked for me too.

WiFi speed increased from about 100Mbit to 250Mbit (provider limit).

Thanks.

Protopale · October 28, 2020, 6:45pm

Are you using the archer c7 v5?

Applepiee · December 1, 2020, 1:04am

Did you find a solution to fix the wireless speeds? Or you think I should flash back to the stock OEM.
I'm at the same version and same router as you and the wireless is around 60-80mbps for me.

Gruntruck · December 1, 2020, 7:48am

running iperf on router itself is not recommended. CPU is not up to task. To truly benchmark WiFi, connect a PC to LAN via Ethernet and run iperf3 server on it. Then run a iperf3 client on a mobile device.

My 6 years old Archer C7 v2 regularly bench >400Mbit on VHT80 using 5GHz.