Throughput-Oriented MAC for Opportunistic Cognitive Radio Networks with Statistical Performance Guarantees

Cognitive radio (CR) technology has a great potential to maximize spectrum utilization. It exploits an underutilized licensed spectrum by enabling opportunistic communications for unlicensed users. In this work, we propose a distributed cognitive radio MAC protocol (COMAC) that enables unlicensed users to dynamically utilize the spectrum while limiting the interference imposed on primary (licensed) users (PR users). COMAC selects the minimum number of channels to use. It does not assume a predefined CR-to-PR power mask, and requires no coordination with PR users. The proposed protocol provides a statistical performance guarantee for PR users, in terms of limiting the fraction of the time in which the PR users’ reception is negatively affected by CR transmissions. To provide such a guarantee, we develop probabilistic models for the PR-to-PR and the PR-to-CR interference, and derive closed-form expressions for the mean and variance of this interference. Empirical results show that the distribution of the interference is approximately lognormal. Based on the developed interference models, we derive a closed-form expression for the maximum allowable power for a CR transmission. Our simulation results indicate that COMAC satisfies the performance guarantees under different traffic loads and arbitrary user deployment scenarios.