Modeling and Performance Evaluation for the Sleep Mode in the IEEE 802.16e Wireless Networks

IEEE 802.16e is the latest broadband wireless access standard designed to support mobility. In mobile networks, how to control energy consumption is one of the most important issues for the battery-powered mobile stations. The standard proposes an energy saving mechanism named "sleep mode" for conserving the power of the mobile stations. According to the operating mechanism of the sleep mode for downlink traffic in the type I power saving class, a discrete-time Geom/G/1 queueing model with a close-down time and multiple vacations is built in this paper. By employing an embedded Markov chain method, the average queue length and the average sojourn time of the system model are derived. Correspondingly, we get the performance measures of the energy saving rate and the average packet delay time for the sleep mode in the IEEE 802.16e. Finally, numerical results are given to demonstrate the dependency relationships between the system performance measures and the system parameters. Furthermore, a cost model is developed to determine the optimum length of the close-down time.