Abstract
In cognitive radio networks, if all the secondary user (SU) packets join the system without any restrictions, the average latency of the SU packets will be greater, especially when the traffic load of the system is higher. For this, we propose an adaptive admission control scheme with a system access probability for the SU packets in this paper. We suppose the system access probability is inversely proportional to the total number of packets in the system and introduce an Adaptive Factor to adjust the system access probability. Accordingly, we build a discrete-time preemptive queueing model with adjustable joining rate. In order to obtain the steady-state distribution of the queueing model exactly, we construct a two-dimensional Markov chain. Moreover, we derive the formulas for the blocking rate, the throughput, and the average latency of the SU packets. Afterwards, we provide numerical results to investigate the influence of the Adaptive Factor on different performance measures. We also give the individually optimal strategy and the socially optimal strategy from the standpoints of the SU packets. Finally, we provide a pricing mechanism to coordinate the two optimal strategies.
Highlights
Nowadays, radio spectrum is one of the scarcest and most invaluable resources for wireless communications [1]
The data set for the Adaptive Factor is set as α = {0.0, 0.1, . . . , 0.9, 1.0}, in which the case of α = 0 indicates the conventional system access strategy without any admission control
In order to distinctively investigate the influences of the arrivals for the Primary Users (PUs) packets and the Secondary Users (SUs) packets on the performance measures, we set the arrival rates of the PU packets and the SU packets as λ1 = {0.2, 0.3} and λ2 = {0.4, 0.6}
Summary
Radio spectrum is one of the scarcest and most invaluable resources for wireless communications [1]. In [7], Kim et al analyzed a carrier sense multiple access strategy in multichannel cognitive radio networks with a three-dimensional Markov chain They derived the throughput and the packet delay of the SUs. priority queueing systems have been widely adopted in performance studies of cognitive radio networks, since the priority queueing systems are suitable to model the nonidentical behaviors of different types of customers that join the systems [8]. In [10], Smith et al considered an M/M/N/N preemptive priority queue with two types of customers They investigated the mean number and the Mathematical Problems in Engineering blocking probabilities for both kinds of users in cognitive radio networks. Based on the working principle of the adaptive admission control scheme, by considering the digital nature of modern communication, we build a discrete-time preemptive queueing model with priority and adjustable joining rate.
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