We are trying to benchmark Pi 3B WiFi speeds with iperf, iperf3 and nuttcp. Transferring TCP mode with unlimited rate.
Running Raspbian Stretch release. 2.4 GHz, channel 6 on-board WiFi in ad-hoc mode (no Access point or router) - on-board chip antenna
One Pi 3B is server the other is a client. Test is in a RF screen room (Faraday cage) to block external interference. Units are < 2 meters apart.
At startup of test, we achieve around 40 Mbps which matches a benchmark I found on this site (38.8 Mbps)
This data rate can be maintained for 30 minutes to 8 hours, but then the data rate abruptly drops to 6 Mbps and stays there.
If the iperf test on client side is stopped and restarted (server side stays running) -- sometimes speed returns to 40 Mbps but in some cases is stuck at 6 Mbps rate.
We also notice that the client side WiFi module (CYW43438) is hot to touch. Could it be overheating and reducing data rate?
I would think once cooled down, the fallback algorthim would attempt higher data speeds.
Any ideas would be helpful. Perhaps there is a configuration parameter in WiFi driver that we can modify?