Adjustable admission control with threshold in centralized CR networks: Analysis and optimization
Yuan Zhao, Shunfu Jin, Wuyi Yue · Journal of Industrial and Management Optimization · 2015
In order to enhance the Quality of Service (QoS) for the secondaryusers (SUs) in Cognitive Radio (CR) networks reasonably, in thispaper, we propose an adjustable admission control scheme consideringan access threshold under a centralized architecture. We assume thata buffer is set for all the SUs. On the arrival instant of an SUpacket, if the number of SU packets already in the buffer is equalto or greater than the access threshold that is set in advance, thisSU packet will be admitted to join the system with an adjustableaccess probability, which is inversely proportional to the totalnumber of packets in the system. Based on the adjustable admissioncontrol scheme proposed in this paper, considering the priority ofthe primary users (PUs) in CR networks, we build a preemptivepriority queueing model. Aiming to comply with the digital nature ofmodern networks, we establish a two-dimensional discrete-time Markovchain (DTMC) and construct the transition probability matrix of theMarkov chain. Accordingly, we provide the formulas for severalperformance measures, such as the blocking rate, the throughput andthe average latency of the SU packets. With numerical results, we show theinfluence of the access threshold on different performance measuresfor the SU packets. Finally, taking into account the trade-off betweendifferent performance measures, we build a net benefit function tofind the optimal access threshold with an optimization algorithm.