The Study Of Distributed Space-Time Codes In Wireless Sensor Networks

In recent years, wireless sensor networks (WSN) are extensively concerned. However, finite energy of sensor nodes and the fading of wireless communication restrict the application of WSN. Multiple-input-multiple-output (MIMO) can combat fading in wireless communication. Required the same reliability, spatial diversity gain provided by MIMO can save transmit energy. Nevertheless, it is difficult to equip multiple antennas at the sensor nodes for their limited energy, process capacity and size. In the cooperative communication, the cooperation of the adjacent communication terminals with single antenna will create a virtual antenna array, which can achieve spatial diversity gain. Therefore, WSN can save energy and overcome the impact of fading by applying cooperative communication technology.The major efforts of this thesis are focused on the distributed space-time code (DSTC) in cooperative communication. Firstly, the basic concept and principle are introduced. Analyze the merits and defects of cooperative communication protocols and cooperative ways, and indicate the cooperative protocol and way adapted to WSN. Secondly, briefly introduce the system model, design criteria, means of decode and some kinds of code of space-time code in MIMO. After that, DSTC is proposed in WSN. Based on the hypothesis that all rows of encode matrices applied by relay nodes are orthogonal respectively and all variances of channel gains between sensor nodes are different, this thesis formulates pair-wise error probability (PEP) and derives the design criteria for DSTC; then, according to design criteria, analyze the existing DSTC, construct a novel DSTC and simulate their average bit error rate (BER). Finally, two power allocation schemes are proposed, and the simulation results show that they can ameliorate the average BER performance of DSTC in the cooperative communication.