Abstract: Continuous search for access point may consume enormous energy,especially for battery-powered mobile devices like mobile phones.To solve this problem,second device was recommended to search for APs and evaluate their power by detecting the periodic beacons transmitted by APs.Only when WiFi signals are detected can wireless adapter be woken up.To detect periodic signals,PSFA (precision-stable folding algorithm) was proposed.Experiment results show that PSFA can achieve high accuracy under both single AP and multiple APs circumstances with low complexity.

Key words: Wireless networks,AP detection,Periodicity detection