The Research On Cooperative Strategy In Wireless Sensor Network

This thesis is based on the Natural Science Foundation of China(No.61071089). With thebackground of the wireless sensor network (WSN), this thesis mainly researched the cooperativeprotocol which is applied in each node of the WSN.First, we introduce the concept of fading of wireless channel, briefly introduce the core idea ofMIMO system, spatial diversity, and analyze the channel model and the capacity of the MIMOsystem. Then, we introduce the system model of cooperative communication and common usedtime-division strategy, and briefly showed the basic principle of several cooperative diversities.Meanwhile, based on orthogonal time-division strategy, Amplify-and-Forward(AF) andDecode-and-Forward(DF) are analyzed in terms of the parameters such as outage probability anddiversity.Moreover, this thesis introduces a new protocol based on minimum mean square error (MMSE)estimate. Taking the range in the constellation the processing function used into consideration, weimprove the set reduction process, and derived a more exact reduction set which have highdefinition and feasibility. Then, we get the concise formulation of the processing function based onthe new reduction set. After that, the noise of forward signal is analyzed, the variance of theestimated forward signal under4-QAM is derived, and the received SNR and outage probability ofthe proposed protocol based on MMSE criteria are also showed. At last, the outage performance andbit error rate are simulated by4-QAM in classical three-node model.The analysis and the simulation results indicate that, the proposed protocol can avoid theshortcoming in AF protocol that the relay will consume too much energy in a moment. Comparedwith DF protocol, it is more reliable. The processing function of the proposed protocol has theadvantage over both AF and DF, and it can obtain higher received SNR, so the proposed protocoloutperforms both AF and DF, and it can achieve full diversity.