SU-APSD: Static IEEE 802.11e Unscheduled Automatic Power Save Delivery

The integration of the wireless LAN technology in mobile devices as cellular phones or PDAs has become a user need due to its popularity in providing high speed wireless Internet access at a low cost. Such devices though should meet users' expectations with regard to QoS, e.g., guarantee a reasonable voice quality when VoIP is used, and power saving efficiency, e.g., standby and calling times should be similar to the ones of cellular phones. IEEE 802.11e defines QoS and power saving enhancements that should allow the wireless LAN technology address users' wishes in such specific devices. However, there are several questions that need to be answered in order to assess whether the additional complexity introduced by these mechanisms would be justified by a relevant performance improvement. With our work we contribute to answer these questions by i) identifying the likely 802.11e functionality to be implemented in mobile devices in the short-term (EDCA+U-APSD) ii) proposing a specific implementation of the U-APSD mechanism (SU-APSD) and iii) evaluating the performance improvement obtained as compared to 802.11 standard power save mode.