Abstract
ABSTRACTMedium Access Control is an important component in cognitive radio that allow secondary users to identify and access spectrum opportunity without interfering with primary users. In this paper, a queueing model to analyze the performances of the secondary users in a cognitive radio network is presented. The queueing model considers the transmissions of a secondary system where a Medium Access Control algorithm is used to enable the secondary users to sense and access the channels. Also, a simple scheduler is employed to assign transmission time slots to the secondary users. Because the value of the system parameters can be perturbed and cannot be determined precisely, the analysis is extended to take uncertainty into account. In this case, a robust optimization method to study the Markov chain with uncertainty is applied to obtain the stationary probabilities of the queueing model under uncertainty. The lower and upper bounds of performance measures are obtained and compared with the nominal value. Copyright © 2012 John Wiley & Sons, Ltd.
Highlights
Non-uniform usage of radio resource over time, location, and frequency [1] results in spectrum opportunity, which can be exploited to improve the efficiency of the wireless communication system
We apply a method used for manipulating the Markov chain with uncertainty to transform the robust optimization problem into a linear optimization problem and obtain the lower bound and upper bound of the QoS measures under uncertainty
Secondary users can have more chance to utilize the channels so that the lower bound of packet dropping probability will decrease, and the upper bound of queue throughput will increase, and the lower bound of average delay will decrease
Summary
Non-uniform usage of radio resource over time, location, and frequency [1] results in spectrum opportunity, which can be exploited to improve the efficiency of the wireless communication system. An unlicensed user (i.e., secondary user) can opportunistically access an unoccupied channel allocated to a licensed user (i.e., primary user). This channel access scheme can be achieved using dynamic spectrum access (DSA) at the Medium Access Control (MAC) layer. We apply a method used for manipulating the Markov chain with uncertainty to transform the robust optimization problem into a linear optimization problem and obtain the lower bound and upper bound of the QoS measures under uncertainty These lower and upper bounds can determine the performance gap when a secondary user operates in the worst-case and best-case scenarios, respectively.
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