Multi-channel power-controlled directional MAC for wireless mesh networks

Wireless Mesh Networks (WMNs) have emerged recently as a technology for providing high-speed last mile connectivity in next-generation wireless networks. Several MAC protocols that exploit multiple channels and directional antennas have been proposed in the literature to increase the performance of WMNs. However, while these techniques can improve the wireless medium utilization by reducing radio interference and the impact of the exposed nodes problem, they can also exacerbate the hidden nodes problem. Therefore, efficient MAC protocols need to be carefully designed to fully exploit the features offered by multiple channels and directional antennas. In this paper we propose a novel Multi-Channel Power-Controlled Directional MAC protocol (MPCD-MAC) for nodes equipped with multiple network interfaces and directional antennas. MPCD-MAC uses the standard RTS-CTS-DATA-ACK exchange procedure. The novel difference is the transmission of the RTS and CTS packets in all directions on a separate control channel, while the DATA and ACK packets are transmitted only directionally on an available data channel at the minimum required power, taking into account the interference generated on already active connections. This solution spreads the information on wireless medium reservation (RTS/CTS) to the largest set of neighbors, while data transfers take place directionally on separate channels to increase spatial reuse. Furthermore, power control is used to limit the interference produced over active nodes. We measure the performance of MPCD-MAC by simulation of several realistic network scenarios, and we compare it with other approaches proposed in the literature. The results show that our scheme increases considerably both the total traffic accepted by the network and the fairness among competing connections.