Performance of Power Saving Modes in IEEE 802.16e System

To extend battery life, modern wireless systems implement Power Saving Mechanisms (PSMs). This work presents a performance evaluation of HTTP Web Browsing and Always-On traffic whithin joint IEEE 802.16e Sleep Mode and Idle Mode operation, on an accurate 802.16e PSM NS-2 simulation implementation. We first determine the most influencial PSM parameters in terms of power savings and performance degradation, for then determining optimal transition points between Sleep Mode and Idle Mode. Results show that although power savings can be achieved, performance degradation can be substantial for a wide range of PSM parameters, if (a) Sleep Mode Inactivity Timer are such that PSM is activated within TCP RTT, or (b) timers for PSM modes are such that there is a ``competition´´ between which PSM mechanism should be activated. Also, under established conditions, we observe a significant power saving gains followed by a surprising system performance enhancement.