Performance Evaluation of Finite-Source Cognitive Radio Networks with Impatient Customers

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 of the performance of Cognitive Radio Networks with unreliable servers

This paper deals with a Cognitive Radio Network (CRN) which is modeled using a retrial queuing system with two finite-sources. This network includes two non-independent service units treating two types of users: Primary Users (PU) and Secondary Users (SU). The primary unit has priority queue (FIFO) and a second service unit contains an orbit both units are dedicated for the Primary Users and Secondary Users, respectively. The current work highlights the unreliability of the servers as we are assuming that both servers of this network are subject to random breakdowns and repairs. All the inter-event times in this CRN are either exponentially or non-exponentially distributed. The novelty of our investigation is to analyze the effect of several distributions (Gamma, Pareto, Log-normal, HypoExponential and Hyper-Exponential) of the failure and repair times on the main performance measure of the system. By the help of simulation we show some interesting results concerning to sensitivity problems

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

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 of the performance of Cognitive Radio Networks with unreliable servers

This paper deals with a Cognitive Radio Network (CRN) which is modeled using a retrial queuing system with two finite-sources. This network includes two non-independent service units treating two types of users: Primary Users (PU) and Secondary Users (SU). The primary unit has priority queue (FIFO) and a second service unit contains an orbit both units are dedicated for the Primary Users and Secondary Users, respectively. The current work highlights the unreliability of the servers as we are assuming that both servers of this network are subject to random breakdowns and repairs. All the inter-event times in this CRN are either exponentially or non-exponentially distributed. The novelty of our investigation is to analyze the effect of several distributions (Gamma, Pareto, Log-normal, HypoExponential and Hyper-Exponential) of the failure and repair times on the main performance measure of the system. By the help of simulation we show some interesting results concerning to sensitivity problems

Performance evaluation of info communication systems.

Information communication Systems or Technologies is a large term that involves any communication application or device: cellular phones, satellites, computers and network softwires or hardwires, etc. Infocommunicaition systems are usually called in particular context, such as communication systems in education, libraries or health care. ICTs have an important task in our world since as nowadays is the information epoch. By the help of ICT, the companies and organizations can make their business easier to establish with the clients, distributor and supplier. In the same time, ITC increases the productivity, the research works, and decrease the waste by sharing information which actually others had done in other places or what they found out so far. Thanks to ICT we are able to read the local newspaper using online newspapers, we can get in touch with our families, friends and colleagues even if we are far away. However, every communication between two or more devices can be done only through the network technologies. information communication is much more than internet and telephone connection, it's a huge field that contains so many topics and studies. We can consider, the cognitive radio networks one of the most interesting and important topic under the big title of networks, which we will examine carefully in the second chapter of this work. The opening chapter will be a detailed introduction, that explains the meaning of the topic's title "Performance evaluation of info communication systems". It gives an overview of the concept of performance evaluation, what does performance evaluation mean and how we evaluate a performance. likewise, the first chapter of this work will clarify the idea and the importance of the infocummunication systems in our life. The second chapter will treat the Cognitive Radio Networks phenomena, which is one of the latest technologies in the network field. With details we will cite the architecture, advantages and some examples of cognitive networks. Not only that, the second chapter, examines the two major types of CRN " half and full duplex", furthermore, as a last part of this chapter we will investigate the main technique use by these type of networks, which "Spectrum Sensing". In the third chapter will go further and explain one of the most complicated theme, which is queuing theory. It takes in account the main point of the queuing theory system in general and the queuing model M/M/c/K in particular which is the appropriate model in order to write the simulation needed in the fourth chapter. After writing the simulation program needed in the fourth and last chapter, we will draw and discuss some figures using this program to compare some scenarios and situations of the queuing systems.MSc/MAComputer Scienc