openwrt / openwrt/mt76

mt76x2u:Speed of AP mode at 5GHz seems to be too low

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Dominant language
C
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Forks
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Description

When I configure the usb wireless card from MediaTek Inc. AP mode at 5GHz and connect to it with my phone,it show the connect speed is 866Mbps on my phone.But from the luci interface,the connection speed is not stable,the RX/TX speed usually shows like

6.0 Mbit/s, 20MHz
216.0 Mbit/s, 40MHz, VHT-MCS 5, VHT-NSS 2

but sometimes it flash to something like

 -44 / 0 dBm	650.0 Mbit/s, 80MHz, VHT-MCS 7, VHT-NSS 2, Short GI
86.7 Mbit/s, 20MHz, VHT-MCS 8, VHT-NSS 1, Short GI

Here is the actual test result of iperf3

iperf3 -c 192.168.50.100
Connecting to host 192.168.50.100, port 5201
[  4] local 192.168.50.11 port 4393 connected to 192.168.50.100 port 5201
iperf3: getsockopt - Protocol not available
[ ID] Interval           Transfer     Bandwidth       Retr  Cwnd
[  4]   0.00-1.00   sec  9.00 MBytes  75.4 Mbits/sec  1296506936   0.00 Bytes
iperf3: getsockopt - Protocol not available
[  4]   1.00-2.00   sec  8.00 MBytes  67.1 Mbits/sec    0   0.00 Bytes
iperf3: getsockopt - Protocol not available
[  4]   2.00-3.00   sec  8.38 MBytes  70.2 Mbits/sec    0   0.00 Bytes
iperf3: getsockopt - Protocol not available
[  4]   3.00-4.00   sec  7.00 MBytes  58.7 Mbits/sec    0   0.00 Bytes
iperf3: getsockopt - Protocol not available
[  4]   4.00-5.00   sec  7.88 MBytes  66.1 Mbits/sec    0   0.00 Bytes
iperf3: getsockopt - Protocol not available
[  4]   5.00-6.00   sec  8.12 MBytes  68.2 Mbits/sec    0   0.00 Bytes
iperf3: getsockopt - Protocol not available
[  4]   6.00-7.00   sec  8.75 MBytes  73.4 Mbits/sec    0   0.00 Bytes
iperf3: getsockopt - Protocol not available
[  4]   7.00-8.00   sec  8.75 MBytes  73.4 Mbits/sec    0   0.00 Bytes
iperf3: getsockopt - Protocol not available
[  4]   8.00-9.00   sec  8.25 MBytes  69.2 Mbits/sec    0   0.00 Bytes
iperf3: getsockopt - Protocol not available
[  4]   9.00-10.00  sec  7.88 MBytes  66.0 Mbits/sec  2998460360   0.00 Bytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Retr
[  4]   0.00-10.00  sec  82.0 MBytes  68.8 Mbits/sec    0             sender
[  4]   0.00-10.00  sec  82.0 MBytes  68.8 Mbits/sec                  receiver

iperf Done.
iperf3 -c 192.168.50.100 --reverse
Connecting to host 192.168.50.100, port 5201
Reverse mode, remote host 192.168.50.100 is sending
[  4] local 192.168.50.11 port 5088 connected to 192.168.50.100 port 5201
iperf3: getsockopt - Protocol not available
[ ID] Interval           Transfer     Bandwidth
[  4]   0.00-1.00   sec  7.52 MBytes  63.0 Mbits/sec
iperf3: getsockopt - Protocol not available
[  4]   1.00-2.00   sec  4.29 MBytes  36.0 Mbits/sec
iperf3: getsockopt - Protocol not available
[  4]   2.00-3.00   sec  3.31 MBytes  27.8 Mbits/sec
iperf3: getsockopt - Protocol not available
[  4]   3.00-4.00   sec  3.60 MBytes  30.2 Mbits/sec
iperf3: getsockopt - Protocol not available
[  4]   4.00-5.00   sec  6.28 MBytes  52.7 Mbits/sec
iperf3: getsockopt - Protocol not available
[  4]   5.00-6.00   sec  6.98 MBytes  58.6 Mbits/sec
iperf3: getsockopt - Protocol not available
[  4]   6.00-7.00   sec  8.22 MBytes  68.9 Mbits/sec
iperf3: getsockopt - Protocol not available
[  4]   7.00-8.00   sec  7.35 MBytes  61.7 Mbits/sec
iperf3: getsockopt - Protocol not available
[  4]   8.00-9.00   sec  7.03 MBytes  58.9 Mbits/sec
iperf3: getsockopt - Protocol not available
[  4]   9.00-10.00  sec  8.10 MBytes  68.0 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Retr
[  4]   0.00-10.00  sec  64.2 MBytes  53.9 Mbits/sec   46             sender
[  4]   0.00-10.00  sec  63.1 MBytes  52.9 Mbits/sec                  receiver

iperf Done.

some info about the AP configuration

root@OpenWrt:~# wifi status
{
        "radio0": {
                "up": true,
                "pending": false,
                "autostart": true,
                "disabled": false,
                "retry_setup_failed": false,
                "config": {
                        "channel": "36",
                        "hwmode": "11a",
                        "path": "pci0000:00/0000:00:04.0/usb3/3-2/3-2:1.0",
                        "htmode": "VHT80",
                        "country": "US"
                },
                "interfaces": [
                        {
                                "section": "default_radio0",
                                "ifname": "wlan0",
                                "config": {
                                        "mode": "ap",
                                        "ssid": "OpenWrt",
                                        "encryption": "none",
                                        "network": [
                                                "lan"
                                        ],
                                        "mode": "ap"
                                },
                                "vlans": [

                                ],
                                "stations": [

                                ]
                        }
                ]
        }
}

some info about the openwrt software and the packages installed

 OpenWrt SNAPSHOT, r3050-b95ffef87
 -----------------------------------------------------
root@OpenWrt:~# uname -a
Linux OpenWrt 5.4.92 #0 SMP Wed Jan 27 09:12:30 2021 x86_64 GNU/Linux
root@OpenWrt:~# opkg list-installed |grep mt76
kmod-mt76-core - 5.4.92+2020-12-18-4a90fdf6-3
kmod-mt76-usb - 5.4.92+2020-12-18-4a90fdf6-3
kmod-mt76x02-common - 5.4.92+2020-12-18-4a90fdf6-3
kmod-mt76x02-usb - 5.4.92+2020-12-18-4a90fdf6-3
kmod-mt76x2 - 5.4.92+2020-12-18-4a90fdf6-3
kmod-mt76x2-common - 5.4.92+2020-12-18-4a90fdf6-3
kmod-mt76x2u - 5.4.92+2020-12-18-4a90fdf6-3

Using the same wireless card to establish a soft AP with the same band&channel on my windows laptop,and testing at the same distance,test device,the test result is about 780Mbps both RX and TX,so maybe that's an issue of the mt76 driver.

Anyway,thanks for your work in advance.

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reproducing the 5 GHz AP-mode behavior with the mt76x2u configuration shown, using the reported wifi status output and both iperf3 directions. Compare the unstable link rates and throughput with the Windows soft-AP result, then inspect the mt76 driver behavior associated with this hardware and configuration. Done means identifying and correcting the cause of the low AP throughput, with stable measurements demonstrating the improvement.

Written by the indexing model from the issue text.

Assessment

Tech stack
c, linux
Domain
networking, operating-systems
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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