On Thursday 20 November 2008 20:21:44 Stefan Steuerwald wrote: > The iPod alternates Null Functions with the PWR MGT bit on and > off - whatever that means. Is it ignoring the AP and snoring > away? This is because the Ipod WLAN card all the time takes a nap of sleep. Whenever it goes to sleep, it sets the PWR_MGT bit. When it wakes up, it sends again a null packet with the bit off. So the AP should always know if the station sleeps or not. If the Ipod has data for the Ipod while it sleeps, it simply wakes up and sends the data, with the PWR_MGT bit off. Maybe it also sends a NULL packet iwth the PWR_MGT bit off in advance. If the AP has data for the Ipod while the Ipod sleeps, it sets the bit that corresponds to the AID of the Ipod in its TIM map. This is sent in the beacons of the AP. Even when a WLAN station sleeps, it knows when a beacon get's broadcasted and wakes up just in order to receive this beacon and check for it's AID bit. If it is set, it wakes up fully, notifies the AP about this and the AP sends the data packet to the now fully awoke WLAN station. -- 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
