An efficient scheduling algorithm for scheduled automatic power save delivery for wireless LANs

Power saving is an important issue when integrating the wireless LAN technology into mobile devices. The IEEE 802.11e introduced an architecture named as Scheduled Automatic Power Save Delivery (S-APSD) aiming at delivering buffered traffic to PS stations while meeting QoS requirement. In S-APSD, the access point (AP) of wireless LAN schedules the service periods (SP) of stations periodically. It is clear that the overlapping of SPs should be avoided to increase the power saving performance. An algorithm named Overlapping-Aware S-APSD (OAS-APSD) was proposed to find the service start time (SST) for a new traffic stream to minimize the chance of SP overlapping. However, it takes high on-line computational complexity and thus could be infeasible for real system. Reserving the optimality of finding the suitable SST, this paper presents an efficient scheduling algorithm to utilize the periodic nature of the service schedules. Therefore, with much less complexity, the AP can respond to the joining of new traffic streams in a much feasible fashion when implementing the S-APSD.