Unsatisfactory WDS (...and 802.11s) performance

Installing and Using OpenWrt
1

2 APs have a backhaul via 802.11ax 5ghz. 4x4 80mhz. They are located fairly close to each other.

When I do iperf3 from either end to the other end I get impressive speeds. 900mbit - 1gbit both ways.

One of the APs, as well as having the WDS link to the other AP is an access point for client devices. On a single adapter.

So essentially it looks like this:

AP1 - phy0-ap0

AP2 - phy0-sta0 is connected to AP1 phy0-ap0 via WDS (tried 802.11s as well)
AP2 - phy0-ap0 is an access point for clients to use

AP1 to AP2, I easily hit 900+mbits.

A client connected to AP2 phy0-ap0 will reach around 250-280 mbits iperf3-ing through the AP, no higher. Naturally iperf3-ing to the AP it self it will hit impressive speeds, 800mbits.

I tried 802.11s mesh, which worked just fine, but the performance was pretty much the same.

Is this normal behavior?

PS : I just (today) upgraded one of the APs. I swapped my mini pcie based wifi adapter to an asiarf 802.11ax one. Previously I had a QCA9984 based 4x4 one. The AP to AP iperf3 performance jumped up about 250mbits... But the "client throught the AP" performance stayed pretty much the same.

2

Sounds about right. A typical wireless client only has a 1x1 or 2x2 antenna(s). (1t x 1r or 2t x 2r)

1x1 = 433Mbps max on 5ghz 802.11ac = 200Mbps typical throughput
2x2 = 866Mbps max " " = 400Mbps typical throughput.

Very few wireless clients have 4x4 unless you are buying a special wireless adapter that can do it. I think some mac books have 4x4.

At that point it may be worth considering buying another cheaper used router instead and using 802.11s and dedicating that node to a wired client. Sometimes the used routers are cheaper than a brand new 4x4 wireless NIC. But that is up to you. WDS doesn't support WPA3 but 802.11s does.

A 4x4 NIC would need a 4x4 AP and the router may not be happy juggling all that in conjunction with WDS or 802.11s. Ie. You might not get max rates unless you have a dedicated 4x4 AP (802.11ax).

Whereas the iperf3 test from 2 wired clients plugged in to the AP's will force them to use full bandwidth 4t x 4r = 1732Mbps max = 850Mbps and then 900-1000Mbps when you swapped in the 802.11ax card.

Are both cards wifi6 or wifi6e?

I don't like wifi6 since it uses 2.4Ghz which is usually crowded.

WDS is around 25% faster than 802.11s in my testing between 2 APs on version 19.07.

What routers are you using?

YRMV

1 Like
3

I have a WDS client on my desk using WPA3:

root@apprentice:~# iwinfo
wl1-sta0  ESSID: "redacted"
          Access Point: redacted
          Mode: Client  Channel: 153 (5.765 GHz)  HT Mode: HE80
          Center Channel 1: 155 2: unknown
          Tx-Power: 27 dBm  Link Quality: 46/70
          Signal: -64 dBm  Noise: -90 dBm
          Bit Rate: 612.4 MBit/s
          Encryption: WPA3 SAE (CCMP)
          Type: nl80211  HW Mode(s): 802.11ac/ax/b/g/n
          Hardware: 14C3:7915 14C3:7915 [MediaTek MT7915E]
          TX power offset: none
          Frequency offset: none
          Supports VAPs: yes  PHY name: wl1
4

I'm sorry Lord VA1DER.

5

Now that both routers are running 802.11ax you should keep an eye on the reported link speeds in LuCI during testing.

Bear in mind if the second router is serving wifi on the same radio as WDS the link speed will take a performance hit.

2x2 802.11ax wifi 6e can hit 2.4Gbps with an Intel ax210 with a throughput of roughly half.

Router to router 4t4r should reach 4.8Gbps using a 160Mhz channel I think. Throughput ~2.4Gbps

If you are using 10/100/1000 NIC in your iperf3 test computers it would max out at 950Mbps measurable.

HTH