The Research Of Virtual Space-time Block Code Transmit Power Allocation In Wireless Sensor Networks

In order to survey, perceive and collect information from monitoring objects or environment, various types of integrative micro-sensors are used in wireless sensor networks (WSN) which transmit data to monitor terminal in self-organizing mode. The cooperation diversity technology enables single-antenna communication system to form a virtual MIMO (Multiple Input Multiple Output) system by sharing antenna, so the problem that multiple antennas are hardly set in a terminal due to the size or complexity of hardware limitation can be solved. Applied the cooperative diversity to the WSN, numbers of single-antenna nodes can share the others antenna to achieve space diversity, which had excellent anti-fading performance, effectively improve data transmission reliability, reduced the whole energy consumption of WSN. In cooperative communication system, for making full use of power to transmit the data of each other, the power allocation is particularly important. In this paper, in order to solve this problem, an improved power allocation methods is proposed,associate Alamouti space-time code and cooperative diversity, an optimal power allocation methods is proposed when total power is constrained.Thesis firstly describes the basic principles of space-time diversity, and then especially analyze the two-nodes Alamouti transmit diversity scheme and encoding method. MATLAB simulation results show that the space-time diversity can achieve diversity gain.Subsequently, based on Amplify-Forward and Decode-Forward cooperative protocol, associate Alamouti Space-Time Block Code, an optimal power allocation between two users is proposed when total power is constrained. Simulation results show that optimal power allocation method can reduce the system bit error rate if the source node and cooperation node can correctly decode each other's data in first time slot under the constrained total power. That is saying, in the same BER requirement, the node consume less energy after using power allocation.Finally, the application of WSN based on cooperative diversity in mine safety monitor and personnel targeted are discussed.