Transient analysis of certain vacation queueing models for power saving in communication systems

Abstract

This thesis investigates the power saving mechanism (PSM) of certain communication systems. The PSMs of WiMAX (Worldwide Interoperability for Microwave Access), WSNs (Wireless Sensor Networks) and LTE (Long-Term Evolution systems) are analysed using vacation queueing models. Vacation policies such as differentiated vacations (DV), threshold policies and modified vacation policies are employed to model the PSMs of communication systems. Mathematical techniques such as generating function, Laplace transform, modified Bessel function of the first kind, continued fraction, confluent hypergeometric function and incomplete Gamma function are applied to derive the transient probabilities of the investigated model. newline newlineAn M/M/1/DV queueing system with a system disaster, server repair and a waiting server are analysed. The DV policy captures the PSM of WiMAX. The server switches to two types of vacations in the DV policy, namely type-I and type-II vacations. Type-I vacation is taken at the end of the busy period of duration T1. If the system is empty at the end of the type-I vacation period, the server switches to another vacation called type-II vacation of duration T2. In this model, disaster can occur at any stage of the system and subsequent repair is considered. newline newlineAn M/M/1/DV queueing system with a dual-threshold policy and vacation interruption is investigated. Both type-I and type-II vacations are interrupted if the system size reaches predefined threshold values k1 and k2, respectively. This type of vacation queuing model controls the server from frequent switching between the functional state and the power-saving modes of the system. newline newline