Quasi-birth-and-death model for queuing based cooperative cognitive networks

Abstract

Queuing Theory was ultimately applied to improve the radio resource sharing in cooperative cognitive radio networks. It indeed gives a better model of storing and transmitting packets of both Primary User (PU) and Secondary User (SU). It especially helps emulate the cooperative radio resource sharing between these two users. With such cooperation protocols, the PU allows the SU to share his spectrum; in exchange the SU relays the PUs' lost packets. However, if the SU applies a preemptive priority to the PU's packets, his achieved throughput will severely be affected. In this paper, we give a practical study which increases the SU's throughput while meeting PU's quality of service. More precisely, the SU relays the PU packets according to a certain radio link quality threshold between the SU's source and destination. We first determine the steady states probability matrix of such a protocol. Then, we resolve the steady states transition probabilities according to the obtained Quasi-Birth- and Death (QBD) model. To do so, we apply Latouche and Ramaswami method which ensures the stability of our system. The obtained results for different PU arrival rates showed the effectiveness of our PU and SU cooperation protocol as well as the stability of our QBD model for the considered cognitive radio network.