On Tue, 2010-03-16 at 22:52 +0100, ext Johannes Berg wrote: > On Mon, 2010-03-15 at 14:55 +0200, Juuso Oikarinen wrote: > > To implement good performance WLAN roaming, it is not sufficient to start > > scanning for other available AP's only after the currently serving association > > is lost. > > > > The entity controlling the roaming will need to get indication of a > > deteriorating WLAN connection in order to start preparing for roaming already > > before the serving association is lost. This way, it can roam to a better AP > > perhaps even before the serving association becomes too bad in quality. > > > > These patches propose an implementation facilitating this using a simple RSSI > > threshold and hysteresis approach. > > > > These patches add a nl80211 interface for simply configuring a rssi threshold > > and hysteresis value to facilitate very basic connection quality monitoring. > > > > For the triggering, these patches currently rely on HW support, host based > > triggering is not implemented, but could be added later if needed. > > I'm curious. How does the HW/firmware do this? > In my testing on some hw, the beacon RSSI fluctuated wildly, so you'd > have to set the hysteresis pretty high. The HW/firmware can be configured with parameters related to averaging, which will smoothen the worst of the fluctuation at least between single frames. Still, there is the WLAN tendency of a very steep RSSI curve, so we'll probably end up with a relatively high hysteresis. Figuring out good values for the config is still to-be-done. -Juuso > johannes > -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
