Power-saving mechanism with delay bound for Mobile WiMAX systems

In Mobile WiMAX, the power saving mechanism (PSM), which operates alternately in sleep and awake modes, works to extend the lifetime of mobile stations (MSs), though it concurrently induces a medium access control (MAC) service data unit (SDU) response delay. In this paper, we derive the analytical models for two of the most important performance metrics: the average power consumption and the average MAC SDU response delay of an MS in sleep mode. These metrics are given as a function of the sleep mode system parameters: initial sleep window Tmin and final sleep window Tmax. Based on these models, we show that a tradeoff relationship exists between them. We then propose an optimized power-saving mechanism (OPSM) that jointly determines the optimal Tmin and Tmax in order to minimize the power consumption under a given MAC SDU response delay constraint. Through both numerical analyses and subsequent simulations, we show that the OPSM effectively minimizes power consumption of an MS in its sleep mode while guaranteeing the MAC SDU response delay constraint. Index Terms Mobile WiMAX, sleep-mode operation, power consumption, MAC SDU response delay. D. T. T. Nga is with the Bell Labs Seoul, Seoul 121-270, Republic of Korea (Email: [email protected]). H. Lim is with the Department of Information & Communications, and the WCU Department of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology (GIST), Gwangju 500-712, Republic of Korea (email: [email protected]).