Game-Theoretic Modeling and Optimization of Contention-Prone Medium Access Phase in IEEE 802.16/WiMAX Networks

IEEE 802.16/WiMAX is an emerging standard for broadband wireless networks. It operates in both point-to-multipoint (PMP) and mesh modes. In the former, a number of subscriber stations communicate directly with a central base station. Although it supports different traffic classes characterized by distinct QoS requirements, the simplest is the best effort traffic. In this class, the subscriber stations first send bandwidth requests to the base station in a contention prone manner. Once the desired bandwidth is granted, scheduled transmissions take place. With increasing number of subscriber stations, due to media contention, collisions increase causing high loss to request packets and hence fall in data throughput. In this paper we address the issue by designing a new medium access control protocol GTMA for this random access phase, using ideas from non-cooperative game theory. We show that the resulting game converges to a unique non-trivial Nash equilibrium. NS-2 simulations confirm the reduction in packet collisions and consequent increase in system-wide data throughput and improvement in short-term fairness. To the best of our knowledge, this is one of the first applications of game-theoretic ideas in the explicit setting of contention control in IEEE 802.16/WiMAX networks.