TDMC: Traffic Fraction-Based Dynamic Multi-Channel MAC Protocol For Long-Distance Wireless Mesh Networks

An LDmesh (Long-Distance) wireless mesh network is an IEEE 802.11-based multi-hop wireless network. It adopts high power wireless cards and high gain directional antennas to achieve long distance (as long as tens or hundreds of kilometers for one link). LDmesh networks have been deployed in rural regions or sparse-populated areas offering Internet access for their low-cost and high-bandwidth. It also can be used for large-area natural reserve surveillance.Many TDMA-based MAC protocols have been proposed for LDmesh networks, which can be classified into catergories of single-channel and multi-channel. The single-channle protocols suffer low link utilization and complex synchronization among links. The multi-channel MAC protocols are static without considering the dynamic traffic. In this dissertation, we propose a TDMC (Taffic fraction-based Dynamic Multi-Channel MAC protocol), a distributed and traffic-fraction-based dynamic multi-channel MAC protocol, for LDmesh networks. Through the analysis of the characteristics of Ldmesh networks, we present two channel allocation rules to optimize network performance. The traffic fraction in the next round is predicted from the traffic fraction in the current round. Channels are allocated dynamically using a division interval approach. A channel switching algorithm is designed on top of the variable time slot TDMA MAC protocol. We also present an chennel selection approach to avoid external WiFi interference.TDMC is implemented in Qualnet 4.5 simulation system. Extensive simulations are carried out to evaluate its performance. We consider different traffic patterns and different network scenarios. Simulation results show that TDMC outperforms the static channel allocation algorithms, especially in asymmetric traffic pattern.