Policy Study And Performance Analysis For The Sleep Mode Of Power Saving Class I In IEEE802.16e

IEEE802.16e is one of the latest standards for the next generation wireless broadband metropolitan network, in which user nodes can move at vehicle speed. In order to improve the energy efficiency for the mobile station, IEEE802.16e offers three kinds of sleep mode. Power saving class I is used for the best effect and the no real time variable rate services. We study the policy and performance analysis for power saving class I in this paper.Firstly, based on the operation mechanism of the elementary power saving class I, take into account the memoryless traffic and the self-similar traffic respectively, a Geom/G/1 and a Geomξ/G/1 multiple queueing models with exponential vacation are built. The expressions of the power saving ratio, the power consuming ratio, the system handover ratio and the average response time are presented. With the numerical results and simulation experiments, the influence of the sleep window length on the system performance measures is demonstrated.Secondly, considering both the power saving ratio and the average response time, a cost model is developed to determine the optimum length of the sleep window. Based on the handover process between the sleep state and the awake state, an optimal threshold for starting the sleep mode is given.Thirdly, a strategy called sleep-delay is provided on the elementary power saving class I. A Geom/G/1 and a Geomξ/G/1 multiple queueing models with exponential vacation and sleep-delay are built to describe the working principle of the power saving class I with sleep-delay. Correspondingly, the expressions of the system performance measures are presented. The dependency relationships of system performance measures on the sleep-delay timer length are discussed by numerical results and simulation experiments, and the validity of sleep-delay strategy is verified.Finally, considering the tradeoff between the energy saving ratio and the average response time for the power saving class I with sleep-delay, a cost model is developed to give the optimal sleep-delay timer length.