Enhanced sleep mode operations for energy saving in IEEE 802.16e

Abstract

The broadband wireless access (BWA) network, such as IEEE 802.16e, becomes more and more popular in recent years. According to the IEEE 802.16e specifications, mobile subscriber stations (MSSs) with energy constraints are allowed to switch to the sleep mode to reduce their power consumption. Considering a number of service connections on the MSS with different traffic characteristics and requesting different power saving classes, the MSS may not be able to sleep and save energy due to improper schedules of sleep operations for service connections. In this paper, an enhanced longer common sleep time (E-LCST) scheme is proposed and it first schedules real-time packets together in less number of frames without violating their delay constraints. After the listen and sleep frames are determined for transmitting real-time packets, the proposed scheme then considers non-real-time packets and schedules them into the existing listen frames if the resources are available. Therefore, MSSs can have more sleep frames and save the energy. Simulation results have shown that the proposed E-LCST performs 33% to 68% better than the conventional IEEE 802.16e Standard in terms of percentage of sleep periods, which reflects power consumption. Although, the proposed E-LCST introduces a little bit more delay, the QoS requirements of real-time connections are still met.