Power management is an important part of the emerging standard of IEEE 802.16e (mobile WiMAX). The sleep-mode operation in power management helps to increase the life of a station by saving energy consumed, but at the same time it increases the response delay of awakening medium access control (MAC) service data units (SDUs). Its performance metrics, energy consumption and the average response delay of awakening MAC SDUs, are affected by correlations among the initial sleep window (T(min)), the final sleep window (T(max)), and the average interarrival time of awakening MAC SDUs (T(I)) during sleep-mode operation. There is a trade-off relationship between the performance metrics, so it is imperative to determine the most effective size for the two windows, T(min) and T(max), in order to reduce energy consumption and still maintain a reasonable response delay time. To reach a fuller understanding of this problem, this paper first models sleep-mode operation in an IEEE 802.16e system and analyzes the effects of the size of the windows on the performance. Based on this analysis, the authors then present a decision making process for leveraging the two performance metrics by manipulating the size of the windows. The decision making process aims to provide some guidelines for determining the most advantageous size of each window to achieve the targeting performance goals. (C) 2008 Elsevier B.V. All rights reserved.