Performance evaluation of finite-source Cognitive Radio Networks with impatient customers

Abstract

The current paper takes into consideration a cognitive radio network with impatient customers, by the help of finite-source retrial queueing system. We consider two different types of customers (Primary and Secondary) assigned to two interconnected frequency bands. A first frequency band with a priority queue and a second one with an orbit, both are respectively dedicated for the Primary Users (PUs) and Secondary Users (SUs). In case the servers are busy, both customers (Licensed and Unlicensed) join either the queue or the orbit. Before joining the orbit, secondary customers receive a random retrial time according to Exponential distribution, which is the holding time before the next retry. Unlicensed users (impatient) are obliged to leave the system once their total waiting time exceeds a given maximum waiting time.The novelty of this work is the investigation of the abandonment and its impact on several performance measures of the system such as the mean response time and waiting time of users, probability of abandonment of SU, etc. Several figures illustrate the problem in question by the help of simulation.

Simulation Analysis in Cognitive Radio Networks with Unreliability and Abandonment

“…At [22] as an example, the authors have pre-sented a retrial queueing system with a single server which is subject to random breakdowns and assuming that collisions may occur when a customer arrives at a busy server which forces both jobs to join the orbit. However, to get closer to real-life situations and involving more servers to the system, the authors of [23] examined the abandonment concept on a Cognitive Radio Network by setting a constant value for the maximum waiting time (abandonment time) of secondary users. In an extended work [24], the same authors of the above-mentioned paper assumed that the abandonment time is random, using various distributions to investigate their influence on the main performance measures of such a system.…”

“…However, to get closer to real-life situations and involving more servers to the system, the authors of [23] examined the abandonment concept on a Cognitive Radio Network by setting a constant value for the maximum waiting time (abandonment time) of secondary users. In an extended work [24], the same authors of the above-mentioned paper assumed that the abandonment time is random, using various distributions to investigate their influence on the main performance measures of such a system. Other probes analysed the abandonment in other types of networks and showed that customers can leave systems from queues, server units while receiving services and while waiting; more details are given in [7,16].…”