Scott’s Weblog

measured noise in madwifi

September 13th, 2006

Initial results from playing with the new noise functions in the HAL are pleasing. I initially added a call to ath_hal_process_noisefloors to the scan_end callback, however that wasn’t being called often enough (i thought it was supposed to be doing background scanning? oh well), so the noise wasn’t updating very often. I’ve decided for now to call it at the end (or maybe it should be the start) of a receive interrupt. The noise is then retreived from the HAL and stored in the ath_softc struct. Here is a graph showing a trace of about 5 mins worth of monitoring. You can see that the noise values are changing, and that they look sensible. This is from initial testing, so the new noise code isn’t hooked into any of the kernel wireless extensions - the only way to get measured noise out is via a radiotap trace
Next is to figure out what is happening with the data points whose signal values are below the noise floor. Once that’s done I’ll start integrating all of this into the driver proper, which is going to be easier said than done. Hopefully though it should lead to a very useful contribution to madwifi.

Entry Filed under: madwifi