We consider a carrier sense multiple access(CSMA) in an unslotted cognitive radio network under a mixed spectrum environment of licensed channels and unlicensed channels. In this system, primary users use only licensed channels, while secondary users use unlicensed channels and opportunistically can use licensed channels unused by primary users temporally. If an arriving secondary user(SU) does...

⎯We consider a single server retrial queue with batch arrivals, two phases of heterogeneous service and multiple vacations with Npolicy. The primary arrivals find the server busy or doing secondary job (vacation) will join orbit (group of repeated calls). If the number of repeated calls in orbit is less than N, the server does the secondary job repeatedly until the retrial group size reaches N....

We consider a discrete-time Geo/G/1 retrial queue in which the retrial time has a general distribution and the server, after each service completion, begins a process of search in order to find the following customer to be served. We study the Markov chain underlying the considered queueing system and its ergodicity condition. We find the generating function of the number of customers in the or...

The main aim of the present paper is to draw the attention of the readers of this special issue to the modeling issues of sensor networks. The novelty of this investigation is the introduction of servers vacation combined with priority customers for finite-source retrial queues and its application to wireless sensor networks. In this paper we analyze a priority finite-source retrial queue with ...

Queueing Systems with Customer Abandonments and Retrials by Song Deng Doctor of Philosophy in Engineering Industrial Engineering & Operations Research University of California, Berkeley Assistant Professor Ying-Ju Chen , Co-chair Professor Zuo-Jun “Max” Shen , Co-chair In queueing theory, the phenomenon that customers get impatient and renege from the system when the waiting time exceeds their ...

This paper analyses the steady state behaviour of an M/G/1 retrial queue with impatient subscribers, two phases of essential service, general retrial time and general vacation time. If the primary call, on arrival finds the server busy, becomes impatient and leaves the system with probability (1 ) and with probability , it enters into an orbit. The server provides preliminary first essential se...

A multi-class c-server retrial queueing system in which customers arrive according to a class-dependent Markovian arrival process (MAP) is considered. Service and retrial times follow class-dependent phase-type (PH) distributions with the further assumption that PH distributions of retrial times are acyclic. A necessary and sufficient condition for ergodicity is obtained from criteria based on ...

The retrial phenomenon occurs inherently in a wide range of queueing systems. majority models do not account for vacation. However, practice, systems undergo vacations maintenance or other reasons. In this study, we provide an in-depth analysis the many possible when Bernoulli are effect. Moreover, study outlines key principles and reviews relevant literature. framework queue with vacation has ...

We consider a single server retrial queue with the server subject to interruptions and classical retrial policy for the access from the orbit to the server. We analyze the equilibrium distribution of the system and obtain the generating functions of the limiting distribution.