The power saving mechanism with binary exponential traffic indications in the IEEE 802.16e/m

In IEEE 802.16e (air interface standard for MWiMAX) and IEEE 802.16m (evolution of MWiMAX for IMT-Advanced), power saving is one of the important issues for the battery-powered mobile stations (MSs). According to IEEE 802.16e standard, when an MS switches from awake mode to sleep mode, the MS is required to send a sleep request (MOB-SLP-REQ) message and to receive a sleep response (MOB-SLP-RSP) message. In this paper we propose a new sleep mode scheme, called the power saving mechanism with binary exponential traffic indications . This sleep mode scheme omits MOB-SLP-REQ/RSP messages and has a traffic indication (TRF-IND) interval as a main system parameter, applying the truncated binary exponential increasing method for its length. The proposed scheme in this paper is quite well aligned with the design policy of sleep mode in discussion at IEEE 802.16m in the sense that it tries to minimize the overhead for the state transition between awake mode and sleep mode, and hence it can reduce the delay due to the state transition and enhance the power saving efficiency. We present a mathematical analysis for the proposed scheme and investigate its performance. As performance measures, we provide the sleep interval ratio, the average power consumption, and the mean delay. Using the analytical results, the system parameters such as the initial TRF-IND interval and the maximum binary exponent for TRF-IND intervals can be optimized while satisfying the QoS constraint on the mean delay. The numerical results show that the proposed scheme consumes less energy than the power saving class of type I in the IEEE 802.16e standard.