Research On Adaptive Relay Selection Of Wireless Cooperative Networks

The rapid development of wireless communications in recent years incurs the higher demand of wireless system from the human beings.The next-generation wireless communication systems are required to adopt more advanced algorithms and technologies,in order to not only provide higher transmission rate,but also to ensure more application functions and better quality of service which are requested by people.Cooperative communication is considered to be capable of effectively competing the fading, and is thought as one method of enhancing the capacity, which could effectively increase the spectrum efficiency and robustness of wireless systems.For the past few years,this new technique draws widely attention of the researchers.At the same time, the concept of cooperation is introduced into the field of wireless communication, in other words, cooperative communication network. Comparing with the conventional communication system with Point to Point, it brings a brightly new research area. In this paper,aiming at the current popular cooperative communication areas, some relevant researches on relay selection have been done, theoretical analysis and simulations have been demonstrated as well. The main research contents are as follows:Chapter III of this article bases on the Two-hop Multi-Relays cooperative transmission system, and proposes a new adaptive relay selection scheme (ARSS). In this scheme, firstly, the destination node determines whether there is a need for cooperative transmission with relay nodes, which is used for the data transmission forward based on the channel status of the direct link. Secondly, the relay node determines the forwarding protocols, such as Decode and Forward and Amplify and Forward adaptively based on the channel status of the first hop. Finally, the destination node selects the relay nodes for cooperative transmission, based on the channel status of the second hop, in order to minimize the number of selected relay nodes while guaranteeing the decoding successfully at destination node. Simulation results show that the outage probability decreases efficiently by the proposed scheme, and the number of selected relay nodes is minimized compared with other relay selection schemes, while improving the system throughput.In order to further study the application of relay node selection in cooperativecommunication network, Chapter IV of this article introduces the relevant theories of the betweenness of nodes in the complex network which is applied in the information transmission efficiency in the area of information physics. Then we combine the mentioned characteristics with the relay node selection in Wireless Multi-hop Network, hence formulate the problem of relay node selection in large scale wireless sensor network. The the adaptive relay node selection scheme is proposed, which is based on the Multi-hop cooperative wireless sensor network. Through the adequate data test, including the real data and simulated data experiments, simulation results show that our proposed scheme in this article, which is based on the combination of the node betweenness/ centrality and the threshold of SNR, could utilize the community distribution property of the spatial diversity better, and the information transmission characteristics of the node is also used, so as to effectively select the relay nodes. Our scheme could improve the data transmission efficiency in wireless sensor network, and shorten the conduction time. The transmission delay of network is also decreased.