Research On Cross-layer Multicast Routing Protocol In MANET

With the development of mobile communication techniques, fixed cellular network can not meet the communicational needs any more. Mobile ad hoc networks, as a decentralized type of non-infrastructure, multi-hop, self-organized wireless network, establishing networks quickly between nodes, is one of the major researches in communication technology and enjoys a wide field of application with good prospects in various industries such as military affairs, disaster assistance, personal communications and sensor networks. However, because of its mobile multi-hop, link bandwidth and power restraint, multicast is an important way to forward data and promote bandwidth efficiency. But instability of multicast routing resulting from dynamic changes of network topology in a wireless ad hoc network demands general multicast routing protocols'frequent operations such as pruning and restructuring, which brings much control overhead and decreases multicast protocol's properties.Classic multicast routing protocols have been introduced in this thesis, and advantages and disadvantages of various protocols also have been analyzed and compared. Multicast routing protocols in mobile ad hoc networks can mainly be classified into tree-based and mesh-based approaches. According to researches, tree-based approaches have high efficiency and low delay in data delivery, but much control overhead as the dynamic network topology makes the protocol repair and reconstruct links; and mesh-based approaches are robust, providing guarantee for data delivery through large redundant routes which on the contrary, brings about higher delay.In this paper, a study of cross layer techniques in Ad Hoc networks has been researched, author analyzed cross layer designation and discussed its necessity in Ad Hoc networks. By analyzing the stack of layered structure system, this thesis researches the information for interaction between different layers and methods for information delivery. In accordance with multicast ad hoc protocols, a means for optimizing multicast resources with mutual restraint and utilization between various layer parameters has been proposed, by applying the thought of cross layer.The core of this thesis is to study the cross layer ad hoc routing multicast protocols, and to make improvement a mesh-based approach by cross layer designation. Through information sharing between network, data link and physical layers, multicast routing with high delivery ratio and very low delay can be realized in mobile ad hoc networks. In the improved protocols, the network layers, with the received information from physical layers, transmit information to neighbor nodes and divide information into several levels, adjust information transmitting ratio in the MAC layer according to channel state and by the neighbor information of nodes computes backoff time for the nodes entering into the channel. The data link layers transmit information according to the parameters of network layers, and judge the information delivery and the information repetition in networks by accounting packet receiving times. Simulation results prove that improved cross layer routing protocols have higher delivery ratio, lower delay and less control overhead than present protocols do.