人力資源與數位學習科技研究所

Abstract

    This talk investigates the power saving mechanism of universal mobile telecommunications system (UMTS). The UMTS utilizes the discontinuous reception (DRX) mechanism to reduce the power consumption of mobile stations (MSs). DRX permits an idle MS to power off the radio receiver for a predefined sleep period, and then wake up to receive the next paging message. The sleep/wake-up scheduling of each MS is determined by two DRX parameters: the inactivity timer threshold tI and the DRX cycle tD. We proposed a variant M/G/1 queueing model with vacations to study the effects of tI and tD on output measures including the expected queue length, the expected packet waiting time, and the power saving factor. Based on the queueing model, analytic analysis and simulation model were proposed to study the optimal tI and tD selections that maximize the MS power saving under the given mean packet waiting time constraint. We also devised an adaptive algorithm called dynamic DRX (DDRX). This algorithm dynamically adjusts the tI and tD values to enhance the performance of UMTS DRX. In recent years, a number of studies have demonstrated that for packet environments, the traffic pattern is self-similar rather than Poisson. Therefore, we further proposed a novel semi-Markov process to model the UMTS DRX with bursty packet data traffic. Our analytic results were validated against simulation experiments to justify the correctness. Numerical examples were provided to show the appropriate inactivity timer and DRX cycle value settings for various traffic patterns.