Research Of Relaying Strategies Based On Cooperative Communications In WSNs

Wireless Sensor Networks(WSNs) are self-organizing networks that there are not fixed infrastructure. In the networks, some sensor nodes with computing and communications functions are deployed over the detective area. WSNs have disadvantages such as large deployed scale, limited node energy, low bandwidth available, unstable topology structure, unreliable data information transmission, etc.. Affected on many adverse factors, such as multipath fading, path loss, bit error rate, shadow affect, etc., the channel condition of WSNs is always unstable. If communications channel condition is not stable, there are susceptible communication, network delay, load disequilibrium, the higher interruption probability and other aspects, it will lead to unreliability of channel between sensor nodes. Therefore, the key issue in WSNs is how to overcome the multipath fading of wireless channel and improve the transmission efficiency of sensor nodes and increasing network reliability.Cooperative communication shows significant advantages in reducing multipath fading. Cooperative communication is to take advantage of cooperative relay nodes own resources and improve real-time performance and reliability of the source node data transmission. In recent years, many results are reported about application of cooperative communication against multipath fading, improving signal to noise ratio(SNR), increasing the spectrum utilization and network capacity.After theoretically analyzing on the feasibility of the opportunity cooperation, the opportunity cooperation in WSNs is investigated in optimizing network SNR and improving the network performance as the goal in this paper. Then, under combining the transmission SNR characteristics of cluster head nodes by using existing WSNs node control technology, optimize the node data transmission SNR, and on this basis, theoretically analyze the best status of node by using knowledge about cooperative communication. To improve the reliability of communication and network nodes spectrum utilization ratio on premise of transmitted power of node communication. The main research results are as follows:Firstly, this paper presents a clustering routing algorithm based on cooperative communication, it can be applied to hierarchical WSNs. The algorithm integrates the advantages of cooperative communication and clustering. In the algorithm, optimum sensor network topology structure and clustering are analyzed to optimize cooperative path selection. The simulation results show that using the proposed scheme, spectrum efficiency and SNR can be improved effectively in WSNs.Secondly, a information relay cooperative transmission scheme(RCTS) based on Nakagami channel state is proposed. There are many advantages about proposed scheme. Such as, it can select the best node from candidate nodes, it can select the best relay nodes to meet network data transmission reliability through known network topology information and instantaneous channel conditions and SNR. And can implement cooperative communication between source node and destination node. The simulation results show that, in Nakagami channel wireless sensor network, using the presented cooperative transmission scheme in this paper could effectively optimize the SNR, improve spectrum efficiency, enhance the reliability of data and information transmission under link variable.