Zhanyou Ma

Performance Evaluation of Wireless Communication Networks for Multi-Traffic with Multi-Channel

In this paper, we present a new effective mathematical analysis to numerically evaluate the performance for multitraffic in wireless communication networks with multi-channel and an admission control scheme. We apply a matrix geometric solution method to describe the stochastic behavior of the system and give the exact performance measures, such as, utilization of channel for both voice and data packets, blocking probability of voice packets, the average queue length of data packets, and the average waiting time of data packets. The numerical results show how priority can be provided and how the whole system performance can be improved based on the running mechanism of the multi-channel wireless communication networks and the various quality of service (QoS) requirements of multi-traffic.

The Pseudo-fault Geo/Geo/1 Queue with Setup Time and Multiple Working Vacation

In this paper, we consider a discrete time Geo/Geo/1 repairable queueing system with pseudo-fault, setup time, N-policy and multiple working vacations. We assume that the service interruption is caused by pseudo-fault and breakdown, and occurs only when the server is busy. Using quasi birth-and-death chain, we establish a two-dimensional Markov chain. We obtain the distribution of the steady-state queue length by using matrix-geometric solution method. Moreover, We provide several performance indices of the system in steady-state. Finally, we present numerical results to illustrate the effect of several parameters on the systems.

Performance Analysis of a Dynamic Channel Vacation Scheme in Cognitive Radio Networks

In order to resolve the issues of channel scarcity and low channel utilization rates in cognitive radio networks (CRNs), some researchers proposed to the idea of “secondary utilization” for the licensed channels. In “secondary utilization”, secondary users (SUs) opportunistically take advantage of unused licensed channels, thus guaranteeing the transmission performance and quality of service (QoS) of the system. Based on the channel vacation scheme, we analyze a preemptive priority queueing system with multiple synchronization working vacations. Under this discipline, we build a three-dimensional Markov process for this queueing model. Through the analysis of performance measures, we obtain the average queue length of two types of users, the mean busy period and the channel utility. Finally, by analyzing several numerical experiments, we demonstrate the effect of the parameters on the performance measures.

A Pure Decrement Service Geom/G/1 Queue with Multiple Adaptive Vacations

In this chapter, a Geom/G/1 queue model with a pure decrement service policy and multiple adaptive vacations is analyzed. The Probability Generation Function (P.G.F.) of the queue length is obtained by using an embedded Markov chain method. The P.G.F. of the waiting time is then derived based on the independence between the arrival process and the waiting time. The probabilities for the system being in various states of busy, vacation, or idle, respectively, are also derived. Finally, some special cases for the Geom/G/1 queue model with a pure decrement service policy and multiple adaptive vacations are given to demonstrate the general properties of the queue models.