Cooperative relay for preemptive transmission in underlay cognitive radio networks

Abstract

Transmission in underlay cognitive radio networks under the interference power constraint to primary receiver nodes have previously been analyzed under non preemptive cooperation, with SUs having non preemptive cooperation among high and low priority SUs. However, under certain conditions high priority SUs are impatient and require less delay. The ob- jective of this study was to reduce the average waiting time of impatient high priority SUs without appreciably detoriating the service of low priority SUs. In this study, a model in which high priority SUs preempt low priority SUs in the underlay cooperative transmission is presented. The performance of the model with preemptive cooperation is compared with non preemptive cooperation using MATLAB. The numerical results show that preemptive cooperation reduces the average waiting time of high priority SUs as compared to non pre- emptive cooperation. The reduction in average waiting time due to preemptive cooperation is observed to be more pronounced at higher arrival rate values. The probability of SU nodes to transmit packets in their own queues is observed to affect the average waiting of packets in the system, with PU packets performing better at higher probabilities, while both categories of SU packets are observed to perform better at lower probabilities. The average waiting time is observed to decrease with increase in service rate for all type of packets. The difference in average waiting time between nodes with non preemptive cooperation and nodes with preemptive cooperation is more pronounced at lower service rates, however at high service rates the difference in average waiting time is less pronounced.