Cooperative wireless multicast: Cooperation strategy and incentive mechanism

Multicast is a bandwidth efficient mechanism to provide wireless services for a group of nodes. Providing reliable wireless multicast is challenging due to channel fading. This thesis investigates cooperation among receiving nodes to enhance the reliability of wireless multicast. A time division based cooperative multicast strategy is proposed, and the optimal scheduling scheme is found to maximize the system throughput. It is shown that the optimal relay number is bounded by a threshold, and the optimal time allocation can be found using an efficient algorithm. Numerical results show that the proposed strategy can enhance network performance when the average channel condition between receiving nodes is better than that of the direct link. To provide incentive for cooperation, this thesis further studies the interactions among selfish nodes using game theoretic approaches. The cooperative multicast process is modeled as a repeated game and the desired cooperation state which satisfies the absolute fairness and the Pareto optimality criteria is found. A Worst Behavior Tit-for-Tat incentive strategy is designed to enforce cooperation and its effectiveness is studied under both the perfect and the imperfect monitoring scenarios. To address the issue of imperfect monitoring, an interval based estimation method is proposed. Simulation results show that the proposed strategy can enforce cooperation efficiently even the monitoring is imperfect.