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摘要
In cognitive radio networks, the packet transmissions of the secondary users (SUs) can be interrupted randomly by the primary users (PUs). That is to say, the PU packets have preemptive priority over the SU packets. In order to enhance the quality of service (QoS) for the SUs, we propose a spectrum access strategy with an alpha-Retry policy. A buffer is deployed for the SU packets. An interrupted SU packet will return to the buffer with probability alpha for later retrial, or leave the system with probability (1 - alpha). For mathematical analysis, we build a preemptive priority queue and model the spectrum access strategy with an alpha-Retry policy as a two-dimensional discrete-timeMarkov chain (DTMC). We give the transition probability matrix of the Markov chain and obtain the steady-state distribution. Accordingly, we derive the formulas for the blocked rate, the forced dropping rate, the throughput and the average delay of the SU packets. With numerical results, we show the influence of the retrial probability for the strategy proposed in this paper on different performancemeasures. Finally, based on the trade-off between different performance measures, we construct a cost function and optimize the retrial probabilities with respect to different system parameters by employing an iterative algorithm.
- 出版日期2014-4
- 单位燕山大学
