Research And Implement Of A MAC Protocol Supporting Streaming Services In Ad Hoc Networks

As a supplement to the traditional networks with fixed infrastructures,a mobile ad-hoc network(MANET)has the characteristics of rapid deployment and strong adaptability to topology changes,so these advantages make it widely applied in disaster recovery,search and rescue,military action and so on.Due to the operations in a distributed manner,a Multiple Access Control protocol in a MANET has a significant impact on network performance.A TDMA protocol features the share of a broadcast channel without collisions.Now most TDMA protocols in a MANET are studied and designed from the perspective of link level.However,the quality of a multi-hop streaming service is influenced by the links on the path originating from source to destination.Consequently,a path level requirement is proposed to the TDMA protocol applied in a MANET.The key to solve this problem is how to maximize path bandwidth by optimizing timeslot sharing,competitiveness and spatial reusage.Aiming at needs of end-to-end time slot allocation for streaming services,this paper proposes NSRA,a path-level dynamic time slot allocation algorithm.The NSRA algorithm divides the nodes on the path into a multiple continuous node sets,sorts the nodes according to the local bandwidth of the node sets,traverses the node sets starting from the node set with the smallest local bandwidth by using greedy thoughts,and allocates time slots for the nodes in the node sets.The NSRA algorithm transforms the problem of maximizing the computational path of multiple nodes on the entire path into the problem of local optimal allocation by rounds,which reduces the implementation complexity and can obtain better suboptimal solutions.Then,based on NSRA algorithm,a distributed TDMA protocol is designed,which combines path discovery with dynamic time slot allocation.At the same time of path discovery,the available time slot information of each node on the path is attached,thus reducing the overhead of control information in the network.Besides,the TDMA protocol calculates the local path bandwidth of the current path in the path discovery process,and tries its best to find a path that can meet the bandwidth of the traffic flow according to the comparison between the local path bandwidth and the minimum bandwidth requirement of the traffic flow.The NSRA protocol is implemented on the hardware development platform,and compared with Zhu’s forward iterative algorithm through software simulation,including the average path bandwidth comparison test for the 10-hop path,the average path bandwidth comparison test for the 20-hop path,and the complexity comparison test algorithm.The test results show that the NSRA protocol can obtain higher path bandwidth than Zhu ’s forward iterative algorithm,and in most cases it is closer to the optimal solution calculated by the MIP algorithm,which verifies the feasibility and effectiveness of the NSRA algorithm.