High usage of various mobile application services consumes a great deal of battery power in mobile devices. In order to satisfy a user’s convenience and keep the portability of mobile devices, a power saving mechanism is essential for the success of mobile communication technologies. This dissertation evaluates performances of the power saving mechanism of IEEE 802.16m, one of the solutions for the fourth mobile communication technology. When a mobile device does not need to communicate with a base station, it temporarily shuts down communication-related modules and circuits in order to save the battery power. During that period, the device cannot listen to incoming traffic from the base station, which causes an inevitable delay at the expense of reducing the power consumption. Arriving packets are transmitted only after the device enters either the awake mode or the listening window in the sleep mode. Four power saving mechanisms are examined in the simulation:1) moving average with queue-size listening window, 2) moving average with fixed listening window, 3) moving average with listening window in inverse proportion to sleep cycle size, and 4) exponential increase policy. To evaluate the delay in the sleep mode, an analytic model is developed based on M/D/1 queuing system with vacations. Various traffic models are examined to find out optimal power saving mechanisms for specific services: Poisson, WEB, FTP, GAME, VIDEO, VoIP, WEB+FTP, WEB+VOIP, and GAME+VOIP all of which except Poisson reflects real service environment.