Cooperative Overlay Cognitive Radio with Opportunistic Link Selection

This papers studies opportunistic scheduling for causal overlay cognitive radios where the secondary source cooperates with the primary source. The secondary source is equipped with a buffer and can store the data it receives from the primary source. The target is to maximize the long term secondary rate under constraints on the long term primary rate and to ensure buffer stability. An optimal opportunistic scheduling policy is derived by solving the constrained optimization problem which fully exploits the available diversity gains due to cooperation and buffering. Numerical results show that the optimal scheme enlarges the achievable rate region compared to a benchmark scheme which does not utilize cooperation between the primary and secondary sources.