Carrier Synchronization For Wireless Sensor Networks Based-on Multi-node Collaborative Communication

As wireless sensor networks develop, the application field becomes more and more widely and refers to all aspects of our life. The requirement of data rate and quality of service is getting higher constantly. The study about WSN is getting deeper. WSN has to consider not just quality of communication system, but also the limit from sensors' feature. Multi-antenna technique is an effective means of improving performance of the system. Sensors of WSN can form virtual multi-antenna array, by way of transmit beamforming technique the destination obtains high gains, communication quality then improves.Distributed transmit beamforming is a form of cooperative communication in which two or more information sources simultaneously transmit a common message and control the phase of their transmissions so that the signals constructively combine at an intended destination. Depending on the design objectives and constraints, the power gains of distributed beamforming can be translated into dramatic increases in range, rate, or energy efficiency. Distributed beamforming may also provide benefits in terms of security and interference reduction since less transmits power is scattered in unintended directions. Key challenge of distributed beamforming is distributed carrier synchronization so that the transmissions combine constructively at the destination. This article reviews promising recent results in methods of carrier synchronization, and looks for more effective method for WSN to arise the performance of communication system.An improved distributed beamforming carrier synchronization based on master-slave synchronization is proposed in this dissertation. We present a master-slave architecture where a designated master transmitter coordinates the synchronization of other (slave) transmitters for beamforming. We observe that the transmitters can achieve distributed beamforming with minimal coordination with the Base Station using channel reciprocity. Thus, inexpensive local coordination with a master transmitter makes the expensive communication with a distant Base Station receiver more efficient. This scheme is easier to achieve than the master-slave synchronization, and can improve the performance of WSN system.