Primary-Prioritized Markov Approach for Dynamic Spectrum Access

In order to fully utilize the scarce spectrum resources, with the development of cognitive radio technologies, dynamic spectrum access becomes a promising approach to increase the efficiency of spectrum usage. The spectrum access can be designed in an opportunistic way to efficiently and fairly share the spectrum resources among multiple unlicensed users, while not disturbing primary users' spectrum usage. In this paper, we propose a primary-prioritized Markov approach for dynamic spectrum access through modeling the interactions between the primary users and the unlicensed users as continuous- time Markov chains (CTMC). By designing appropriate access probabilities for the unlicensed users, the spectrum dynamics can be captured using CTMC models to optimally coordinate the spectrum access of the unlicensed users so that a good tradeoff can be achieved between the spectrum efficiency and fairness. The simulation results show that the proposed primary-prioritized dynamic spectrum access approach under proportional fairness criterion not only provides fair spectrum sharing among unlicensed users with only small performance degradation compared to the approach maximizing the overall average throughput, but also achieves much higher throughput than CSMA-based random access approaches and the approach achieving max-min fairness.