A New MAC Protocol with Collision Resolution for OFDMA Wireless Mesh Networks

Wireless Mesh Networks (WMNs) are envisaged to be a key enabling technology for next generation wireless networks. The mesh nodes form the backbone connectivity, performing the dual tasks of packet forwarding as well as providing network access to the mesh clients. In this paper we present a new MAC protocol based on a star-mesh topology, which is compatible with the IEEE 802.16e-2005 Orthogonal Frequency Division Multiple Access (OFDMA) air interface. In this protocol, the same radio resource can be shared by neighboring cells in the WMN and collisions can be reduced in the overlapping areas. In addition, a Markov chain model is developed for analyzing this protocol operating in two overlapping cells. With this model, we analyze the performance of the uplink operating in the OFDMA mode. This new scheme resolves collisions using subcarrier allocation, thereby eliminating the need for random backoff intervals that increase latency and delay variability. As such, the scheme may be more suited for real-time traffic such as voice and video. The analytical results match very well with the simulation results. We then extend our model to a star-mesh topology with multiple overlapped regions. Simulation results show that the capacity can be improved due to the superior ability of our proposed protocol to deal with collisions in the overlapped regions.