Am Montag, 15. September 2008 15:59:20 schrieb Dan Williams: > On Mon, 2008-09-15 at 14:16 +0200, Helmut Schaa wrote: > > Hi, > > > > As a result of the thread "Pondering: how to improve mac80211 roaming > > ..." I thought a bit more about that topic. Here is a quick suggestion > > for a first version: > > > > * Enhance mac80211 software scan to interrupt the current scan and switch > > back to the operating channel every once in a while (only if at least > > one STA interface is associated) => background scan. > > > > * Enhance mac80211 to check the signal quality frequently (or any other > > indicator like beacon misses) and decide when the signal quality is too > > low. Indicate that to the user space. > > > > * wpa_supplicant (or any other user space application) gets notified > > about the low signal quality and triggers a scan in order to find a > > better AP. wpa_supplicant already chooses the AP with the best signal > > strength. > > I'm pretty sure it doesn't. The code in wpa_supplicant_select_bss() > doesn't have any logic to detect signal strength, nor does any driver > report signal strength to the supplicant. Drivers set the level (well, > only wext/nl80211, ndis, iphone/osx, and bsd) but I'm pretty sure > nothing in the supplicant uses it. Once the supplicant receives the actual scan results it orders them by security, rate, signal level and finally quality (see src/drivers/scan_helpers.c, wpa_scan_sort_results). Hence if multiple APs have the same SSID the one with the best signal level (or quality) will be the first in the scan results and wpa_supplicant just selects the first matching AP. Works fine here ;) > Maybe now is the time to switch that on. That needs to be coupled with > some additions to cfg80211 to turn firmware/driver roaming on and off, > along with a capability bit somewhere to indicate that the > driver/firmware support turning roaming on/off. True. Which cards that can do roaming in driver/firmware? 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
