MT7612u maximum number of connections.

[murrellr]

I recently had to change the WiFi adaptor in one of our industrial products when we upgraded the Linux kernel from 4.11 to 6.2. The device uses an NXP i.MX6QP ARM processor. I found an adaptor that met our requirements, the SparkLAN WUBM-273ACN based on the Mediatek MT7612u chipset. Another requirement was snuck in after recommending this product for production, it has to support 12 simultaneous connections. My experience with other WiFi modules and bare metal systems has shown that the 8 connection limitation can be increased by limiting bandwidth and other tweaking to free up resources. Our product communicates small packets at low bandwidth, but must keep the connection open at all times.

SparkLAN support says that the number of connections can't be increased, but I was wondering if someone might have some insight if the MT7612u can be coerced into supporting more channels?

[morrownr]

Hi @murrellr

it has to support 12 simultaneous connections

Help me out. The above makes me think you are running this module in AP mode. Is that correct?

SparkLAN support says that the number of connections can't be increased...

Interesting. Did they say what they think is the limit happens to be?

I was wondering if someone might have some insight if the MT7612u can be coerced into supporting more channels?

More channels or more connections? I need some confirmation of what it is that you are doing so that I understand.

I have used an adapter based on the mt7612u chip as an AP and I would set the limit to the 16 connections. Never had any problems. What problem are you seeing?

[murrellr]

Thanks for the quick response. The SparkLAN module is assigned "wlan0" (I have unique naming turned off). This interface we use for station mode. I run an iw command to enable a second interface "wlan1". This is set up as an AP and configured by hostapd. We have external devices that join this AP and make a single TCP connection to a server running on the master. We can connect 8 devices via the AP. When we connect a ninth device, one of the others drops out. So by connections, I mean the number of stations that can join simultaneously. SparkLAN said that only 8 stations can join. They suggested that no USB WiFi dongle will support more than 8 simultaneous connection, but I find that hard to believe.

[morrownr]

@murrellr

Thanks for the explanation. Now I understand better. I have a lot of experience with hostapd myself. I am not aware of an 8 connection AP mode limit with the mt7612u chip or with the mt7612u in-kernel driver. My best guess is that what appears to be an 8 connection limit is caused by something else.

My AP mode bridged guide is located:

https://github.com/morrownr/USB-WiFi/blob/main/home/AP_Mode/Bridged_Wireless_Access_Point.md

I use systemd-networkd for my networking setup as I have found it to be extremely stable and I have not found an 8 connection limit. There was a user about 2 years ago that needed a large amount of AP mode connections and based on his needs I suggested an adapter with a rt3070 chip and he ran stable at 56 connections. The connections were low throughput but needed to be up and available all of the time. The rt3070 is not longer in production but I have seen no evidence that there is an 8 connection limit with the mt7612u chip. If you had come asking for a chip for AP mode in the AC1200 class, I would have suggested this chip. What band are you using?

I could take a look at your hostapd.conf but other than that, I am not sure what is causing your issue.

@morrownr

[murrellr]

I have done some testing and it appears that the SparkLAN module can only support 9 TCP connections, not WiFi connections. Our device has a built in webserver that serves a page that keeps a TCP connection open for streaming unsolicited events. I connected my Windows laptop to the device's AP and opened 5 browser tabs. Windows has a built in limit of only allowing 5 open TCP connections to the same device. I connected another Windows laptop to the AP and started opening browser tabs. I was able to open 4 tabs. The fifth one failed trying to open the event stream. So, in this configuration, I had two stations connected, and 9 TCP connections open. I believe the difference between 8 device connections via a different port and 9 port 80 connections was due to our testing with one browser window open. So there is a limit to how many open TCP connections the module can support. With wired Ethernet, our device can support 24 slave connections (an internal application limitation), and a large number of HTTP connections. The SparkLAN module itself consists of the MT7612U and a handful of components.