The Power-Saving Mechanism With Periodic Traffic Indications in the IEEE 802.16e/m

In IEEE Standards 802.16e (air interface standard for MWiMAX) and 802.16m (evolution of MWiMAX for IMT-Advanced), power saving is one of the important issues for battery-powered mobile stations (MSs) due to mobility. According to the 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 periodic traffic indications, where the MOB-SLP-REQ/RSP messages are omitted, and a traffic indication (TRF-IND) message is periodically sent at the beginning of every constant TRF-IND interval. The merits of the proposed scheme are simple implementation, reduction of energy consumption, and saving of the resource compared with the sleep mode in the IEEE 802.16e standard. The proposed scheme in this paper is well aligned with the design policy of sleep mode in discussion at IEEE 802.16m in the sense that it tries to minimize the state transition overhead between the awake and sleep modes, and hence, it can reduce the delay for state transition and enhance the power-saving efficiency. We investigate the performance of the proposed scheme in two ways: simulation and analytical methods. Using the performance evaluation, we find the optimal TRF-IND interval, which minimizes the average power consumption of the MS while satisfying the quality of service (QoS) on the mean delay. Numerical results show that the proposed scheme has 20%-50% reduction of the energy compared with the power-saving class (PSC) of type I, which is one of three operations for sleep mode in IEEE 802.16e.