Performance Evaluations and a Power Management Mechanism for Mobile WiMAX Systems

Abstract:
The Mobile WiMAX (or IEEE 802.16e) standard defines a power saving mechanism (PSM), which operates using sleep- and awake-modes, to conserve power of a Mobile Station (MS) but at the expense of an increased service delay. This delay includes an access delay for the MS to transition from sleep- to wake- modes and a queuing delay that a queued packet in base station (BS) buffer has to wait. In addition to service delay, a PSM results in a packet loss if the number of packets in the queue is more than BS buffer size. Unfortunately, previous studies on Mobile WiMAX did not sufficiently consider queuing delay and packet loss. In addition, design of sleep- mode has to guarantee network quality- of- service (QoS) in terms of service delay and packet loss besides reducing power consumption. This paper derives analytical models for power consumption, service delay, and packet dropping probability, given as a function of sleep-mode parameters such as the initial sleep window Tmin and final sleep window Tmax' Furthermore, the paper proposes a power efficiency under QoS constraints (PEQC) mechanism to minimize consumed power of an MS under service delay and packet dropping probability constraints by findings jointlyoptimal parameters Tmill and Tmax' Extensive simulations validate that the proposed numerical models are correct and that the PEQC mechanism sufficiently reduces MS's power consumption. In some cases, the PEQC mechanism can save up to 70% of consumed power compared to the original power saving mechanism in Mobile WiMAX. Keywords - Mobile WiMAX; sleep-mode; power consumption; delay; packet dropping probability