Research Of Power Saving Mechanism In WiMAX System

WiMAX(Worldwide Interoperability for Microwave Access) is a kind of wireless metropolitan area network technology based on IEEE802.16 standard. As an emerging broadband wireless access technology, Wi MAX offers users with high-speed Internet connections, and supports the terminal moving at the speed of the car, at the same time the distance of data transmission can be up to 50 km. In order to extend the battery life of mobile terminals, IEEE802.16 system uses power-saving mechanism(PSM) to improve the energy efficiency of mobile terminals. Three power saving classes have been defined in IEEE802.16 e, corresponding to different types of services. Inheriting the feature of the power-saving mechanism of IEEE802.16 e, IEEE802.16 m proposed a unified sleep mode to deal with all kinds of services.In this paper, I studied the power-saving mechanism of IEEE802.16, on that basis, I proposed two new power-saving mechanisms, one is for non-real-time services and the other is for Vo IP services with silence suppression, respectively.As for non-real-time services, existing PSMs adopted by IEEE802.16e/m employ exponentially growing sleep window, which cause frequent state switching and high packet delay. As a solution, I proposed a novel power saving mechanism namely n PSM, which adjusts the sleep cycle according to the average packet inter-arrival time. Whenever there is a packet arrives, the base station(BS) calculate the average packet inter-arrival time, and the information of measured inter-packet time is piggybacked on downlink packet sent to MS during the next communication between the BS and the MS, as the length of the subsequent sleep cycle. Combining numerical analysis and simulation experiments, this paper verifies that, under low traffic load, n PSM can achieve better energy efficiency while reducing the latency of packets compared to other PSMs for non-real-time services.For real-time service, IEEE802.16 system provides a power saving mechanism with fixed length of sleep cycle to meet for the requirement of Qo S, and to complete the periodic data transmission. But for voice over internet protocol(Vo IP) service with silence suppression, the power saving algorithm provided by the IEEE802.16 standard does not make good use of the silent period for sleeping, which can conserve more power. As a solution, a power saving mechanism that combines power saving class I, class II, class III which is applicable to Vo IP service with silence period is introduced in this paper, called v PSM. The mechanism basically follows PSC II during talk-spurt periods of a Vo IP connection but in silence periods it combines PSC I and PSC III. According to simulation experimental results, more than 93% power reduction can be achieved in mutual silence period by using the proposed v PSM for Vo IP services during silent periods with respect to the Quality of Services.