Measuring WiFi performance (TP-Link TL-WN823N)

Starting a new question based on this thread.

@DBMandrake. I tried iperf and I think the results are telling me I achieve about 9 Mbps. I gather this is pretty low, considering you reported 10X that at 90 Mbps?

I also ran sudo iwconfig to get more network performance characteristics. I do not see a dB signal strength, only a % value, 61/100. Not sure if this is good or bad? Link quality is 100% and noise is 0%, so it seems those parts are fine.

My media box, a Windows 7 PC, is also running WiFi. I guess it is also possible that WiFi connection is slow.

Try to to test to another machine that is connected via Ethernet, as if they are both sharing the wifi (sending wifi to wifi) it will slow the performance down by at least half, in practice a lot more than that.

Also you want to use -w 1M to use a 1MB window size, as the default 64KB window size won’t perform very well over wireless.

Keep in mind that iperf tests by sending from the client to the server, not from server to client, so if you want to test the receive performance of the Pi (which is what matter for streaming a video to the Pi) then you must run the iperf server on the Pi and the client at the other end.

Good tips - thanks. I repeated the test with the Pi as the server, and with 1M window size specified on both my PC and Pi (although the Pi limited to 320 KByte (WARNING: requested 1.00 MByte)). I did not hardwire the PC into Ethernet for now because I wanted to test my intended use case, not best possible performance.

Unfortunately, the results were worse at 5.3 Mbps :frowning:

The good news is that I seem to be able to watch movies OK (no significant buffering or lag, so far). The main problem is looking through photos is painful as it takes a few seconds to load each one.

Is there anything I can (or should) do to improve this? I just purchased the router (D-Link DIR-850L) and the WiFi adapter (TP-Link TL-WN823N) a couple of days ago, so I can still return them if something else would produce significantly better results.

Have you tried changing the channel the router is using ? Run a program like insider to see how many neighbours are on each channel and try to pick one that is least used.

Also how far is each device from the router ?

BTW I would still try to test it to an Ethernet connected device as well - otherwise you are dealing with two unknowns.

Plug each device into Ethernet in turn so that an individual wifi connection can be tested at a time.

Good ideas, as always - thanks @DBMandrake

Inssider is no longer free, so I downloaded the Android App WiFi Analyzer to investigate. My router was set to auto-channel, and was using #10. Turns out this was pretty crowded, so I moved to #1 instead (the most “open” channel available). Unfortunately, not much performance improvement (Run #3 below)

The Pi is about 35’ away from the router, with 1 wall in the path. The PC is about 40’ away, and separated by a floor (PC on 2nd floor, router on main). WiFi Analyzer measures -65 dBm at the Pi and -80 dBm at the PC.

Next, I tried turning off my VPN service (Run #4). Couldn’t see how that would change anything on intranet, but just in case. Somehow, performance was worse. Thought this must be a mistake, but it was repeatable.

Also tried connecting each side (Pi / PC) to Ethernet in turn (Run #5 / Run #6, respectively). Putting the PC on Ethernet made the most improvement (makes sense, given the weak -85 dBm signal), but still pretty poor transfer at 11 Mbps.

Finally, putting everything on Ethernet (Run #7) I obtained the “best case” results of 95 Mbps.

I expected a big improvement putting the PC on Ethernet, but was actually a little disappointed that the Pi WiFi did not perform better. Not sure if I should be looking at a MIMO router, or maybe a 5 GHz WiFi adapter (I know the OSMC drivers are not reliable yet, so may need to wait on this).

5 GHz will only help you against overcrowded channels it will not improve your signal strength. Depending of your environment (type of walls) it might even get worse than 2.4 GHz.