MAC Protocol And Routing Algorithm For Cooperative Transmission In Wireless Networks

As wireless network applications grow in popularity,the users place more demands on network service quality.The ability of a single network node is so limited that it's difficult to ensure the users' high standard requirements in terms of signal transmission quality and network throughput.On one hand,wireless channel fading will have a huge impact on signal quality.Transmission reliability can not be guaranteed if the direct transmission channel from source node to destination node goes through severe signal fading or interference.On the other hand,it is difficult to meet the users' demands while the network traffic increases dramatically as well as single node only can provide limited download speeds.Using cooperative transmission is an effective means to solve the problem of limited ability of single node.Increasing more transmission paths through cooperative transmission of other network nodes can effectively combat the channel fading and improve network throughput.This paper focuses on the research of cooperative transmission in wireless networks.At first,we study the channel accessing in cooperative communication that is a cooperative transmission means in the physical layer.Then,we mainly research the source and routing selection and channel allocation problems in multi-source cooperative transmission that is the cooperative transmission means in the application layer.The main work and innovation are stated as follows:For the complex channel accessing issue in cooperative communication,this paper designs a MAC scheme that concurrently combines the RTS/CTS scheme and busy tone.In the scheme,three busy tones are proposed to announce the state of channel occupation and solve the hidden terminal and exposed terminal problems in cooperative communication.Based on the busy tone,this paper also designs a bandwidth efficient relay selection algorithm,in which the source can select the best relay in a distributed way by sensing the busy tone.The simulation results demonstrate that the proposed scheme can efficiently improve the channel utilization and solve the hidden terminal and exposed terminal problems in cooperative communication.For the problems of source,routing and channel selection in multi-source cooperative transmission,we propose an interference-aware joint source,routing and channel selection algorithm to maximize network aggregate throughput.The algorithm consists of three sub-algorithms.The first sub-algorithm is the maximum throughput path search algorithm,in order to find a maximum throughput path in the current network topology.The second sub-algorithm is the channel selection algorithm,which can select the channel for each link of the path during the process of maximum throughput path search.The third sub-algorithm names local routing adjustment algorithm,which aims at making the new path being part of the path solution set through adjusting the bottleneck link.The simulation results make clear that the proposed algorithm can effectively maximize the network throughput.