Advanced Power Saving Mechanism in IEEE 802.16m Wireless Metropolitan Area Networks

The mobile wireless metropolitan area networks (WMAN) architecture adopts power saving mechanism to prolong the battery lifetime of mobile devices. Due to the burst characteristic of non-real-time service, the exponentially growing sleep window, which is employed in the IEEE 802.16e and IEEE 802.16m, seems not the best approach in term of packet response time. To let the sleep window match the traffic pattern, base station (BS) should collect traffic information and then notify mobile station (MS) the appropriate sleep window size. As a solution, we propose an advanced power saving mechanism, namely A-PSM, which simply adjusts the sleep window according to the average packet inter-arrival time in order to improve the power saving capability. To reduce the negotiation overhead and accomplish the synchronization of sleep pattern between BS and MS, the information of measured inter-packet arrival time is piggybacked on every downlink packet sent from BS. Moreover, a parameter of tolerable delay is proposed to control the packet delay when the inter-packet arrival time suddenly becomes longer. As confirmed by the performance evaluation, the proposed A-PSM can easily achieve better power saving capability, as compared to the IEEE 802.16e and IEEE 802.16m under all kinds of traffic arrival rates.