Research On Multi-Channel MAC Protocol In Multi-Radio Witrless Mesh Network

Wireless Mesh Network (WMN), a multi-hop wireless network connecting routers and terminals with wireless link, is a new type of broadband wireless access systems. Nowadays, researches on WMNs have been very popular around the word. Since channel allocation and management is a key factor influencing network performance optimization, MAC protocols for WMNs are gaining significant attention.Based on the analysis of conceptions, architectures, key technologies and the existing MAC protocols of WMNs, this thesis focuses on multi-channel MAC protocols of WMNs, especially on the multiple radios condition. Existing multi-channel MAC protocols are mainly based on Ad hoc network, and seldom consider the characteristics of WMNs and characteristics of traffics. This thesis will research multi-channel MAC for WMNs based on the consideration of traffic characteristics.Firstly, this thesis analyses traffic characteristic in an IEEE 802.11 based multi-radio mesh network. Most traffic flows access to Internet through gateway, and traffic flows aggregate at routers close to the gateway. The aggregation of traffics introduces gateway "hot spots" problem. And, since the nodes in networks are randomly distributed and the loads of links are different, the links need be treated differently.Considering gateway "hot spots" and link loads, this thesis proposes a multi-channel MAC protocol with link priority-aware channel assignment (PCA-MMAC). PCA-MMAC developed on the IEEE 802.11 hardware and is a multi-channel MAC scheme which support multi-radio. PCA-MMAC can be used in the node equipped with multi-radios based on IEEE 802.11 protocol. It extends single-channel MAC protocol, without any modification to the upper layers and the lower layers of the network protocol stack. It mainly assigns channel for multiple radios. Channel assignment uses a link priority-aware channel assignment algorithm. This algorithm distinguishes priority of links in the network, assigns channel according to priority. Link priority is defined according to the distance to gateway and loads of links. The less the number of hops is, the higher the priority is. If the number of hops is the same, the heavier the load is, the higher the priority is.And, we developed a process model and a multi-radio wireless node model on OPNET Modeler 10.0, and did network simulation and performance analysis. The simulation results show that the capacity of networks can be greatly increased by the employment of PCA-MMAC.