Network Card User Manual

WLAN-IEEE802.11 Tutorial (Maximilian Riegel), 021018-wlan-tutorial.ppt Page 48 © Siemens, 2002
Power Management Approach
n Allow idle stations to go to sleep
– station’s power save mode stored in AP
n APs buffer packets for sleeping stations.
– AP announces which stations have frames buffered
– Traffic Indication Map (TIM) sent with every Beacon
n Power Saving stations wake up periodically
– listen for Beacons
n TSF assures AP and Power Save stations are synchronized
– stations will wake up to hear a Beacon
– TSF timer keeps running when stations are sleeping
– synchronization allows extreme low power operation
n Independent BSS also have Power Management
– similar in concept, distributed approach