Am Dienstag, 24. März 2009 schrieb Holger Schurig: > > Hmm, quick example: AP1 - STA - AP2 > > > > We cannot consider the signal strength as constant as it > > varies over time even when neither the STA nor the AP are > > moving. Assume a threshold value of t=40. Furthermore, the > > signal strength of AP1 and AP2 might alter between 35-50 which > > means we have an average signal strength of 42,5 > t. > > Nevertheless that would result in ping-pongs between AP1 and > > AP2 because the signal might drop below t on both APs, while > > it would be better to stick to one AP as the signal is already > > quite bad (but still good enough to do some communication). > > Yeah, but if the client is moving, you have to live with that, > more or less. > > And if the client is not moving (and roaming is a loadable kernel > module), then simply don't load it :-) Ah, ok. I was more referring to an ordinary laptop user who sits at his desk and once in a while starts moving (for example to a conference room). While he sits at his desk the optimal solution shouldn't trigger a scan as the chance that a better AP pops up is relatively low. Once he starts moving scanning is desired. > My ad-hoc approach that I already implemented (for non-mac80211) > shows a quite number of scannings. But that is ok for my > use-case (e.g. telnet connection via WLAN). "Connection lost" is > way worse than one scanning/reassociation too much, especially > if the scanning/association is done intelligently. > > So for now I wouldn't optimize here, but make non-sucking roaming > possible in the first place. We can build upon this anyway. Fine with me. But too aggressive scanning might lead to unstable or intermittent connections, especially when WPA-EAP without PMKSA-caching is used where roaming from one AP to another can take up to several seconds ;) And additionally if the connection is idle, repeated scanning will increase the power consumption which is not desired on battery driven devices. Helmut -- 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
