Dynamic channel allocation-based call admission control in cognitive radio networks

To alleviate the performance degradation of secondary users (SUs) due to failed handoff, channel reservation is applied as an efficient way in call admission control design in many previous studies on cognitive radio networks. However, in a cognitive radio environment, a straightforward application of this technique could actually reduce the probability of successful handoff, due to its conservative way of utilizing time-varying primary spectrum resource. In this work, a slotted call admission control scheme integrated with dynamic channel allocation is proposed to address the issue. In the proposed scheme, admitting user only occurs at the beginning of a new slot; thus, new SUs arriving between two slots must first enter a waiting queue until the next slot arrives. By imposing a mandatory yet limited waiting time on new SUs, the proposed scheme offers an opportunity to allow admitted SUs to fully utilize the available primary spectrum. An analytical framework using a three-dimensional discrete-time Markov chain is developed to analyze the impact of the proposed scheme on both the call-level and packet-level performances of SUs. Simulation results verify the accuracy of the analysis and show the effectiveness of the proposed scheme in terms of reducing blocking and dropping probabilities, lowering packet queueing delay, and improving spectrum utilization efficiency.