Channel Aggregation in Cognitive Radio Networks with Practical Considerations

In cognitive radio (CR) networks, spectrum resource that can be shared by secondary users (SUs) is always restricted by primary users (PUs). Although channel aggregation (CA) enables each SU to access multiple channels at a time, whether it is beneficial is subject to the PU activity and radio capability. In this paper, we study the feasibility and efficiency of CA in consideration of various such practical constraints and costs. First, we propose a novel channel usage model to analyze the impact of both PU and SU behaviors on the availability of white spaces. This model is very general and can capture a wide range of user behaviors. Next, we model the costs in time for performing CA. User demands in both frequency and time domains are considered to evaluate the costs for making negotiation and renewing transmission. Further, an optimal CA strategy is defined to minimize the cumulative delay for transmitting a certain amount of data. Numerical and simulation results based on real data of PU activity show that user demands on both bandwidth and duration should be carefully chosen to achieve the optimal delay performance in practice.