Study On Nodes Ranging And Positioning Techniques Based On Gcrt In Wireless Sensor And Actuator Networks

Wireless sensor and actuator network(WSAN) is a kind of new wireless network which was proposed in recent years and originated from wireless sensor network(WSN). WSAN is composed of a group of sensors and actors linked by wireless medium to perform distributed sensing and acting tasks. In WSANs, Actors are resource rich nodes with better processing capabilities, higher transmission powers and longer battery life. Actors analyze the information gathered from sensors and then take decisions and perform appropriate actions upon the environment. Thus, wireless sensor and actor network is much powerful compared with WSN.Similar to in WSN, node localization is also a key issue in WSAN. The node location message is indispensable to many applications of WSAN. In WSANs, sensors have to know their location to tell actors "what happened in where". And only with nodes location message, can actors perform appropriate actions in the place where event is occured. Therefore, nodes positioning technology is one of the key support technologies in WSANs.In2009, Chinese Remainder Theorem(CRT) was firstly used in distance estimation in radio interferometer positioning system(RIPS). As CRT can be effectively used to solve the phase ambiguity problem, the distance estimation algorithm based on CRT usually has higher estimation accuracy. In recent years, CRT has been applied in the distance estimation between sensors and actors to positioning sensors in WSAN and the research in this area is still limited. Therefore, in this thesis, the ranging and location technology based on CRT in WSANs was studied in detal, main work in this thesis included:Firstly, the carrier phase measurement technology was studied. A high-accuracy frequency and phase estimation method of signal-tone based on DFT phase was mainly researched and the foundation for the future research was laid.Secondly, four kinds of solution methods of Chinese Remainder Theorem(CRT) which are known as Traditional CRT, Efficient CRT, Closed-Form CRT and Dual-Frequency CRT were studied and their performance was analyzed and compared in detail.Thirdly, the four kinds of CRT were used in distance estimation in wireless sensor and actor networks, four distance estimation methods were designed based on the four kinds of CRT and the characteristic of the four methods were analyzed. The difference at estimation precision, complexity and robustness for these methods were compared based on simulation and the scenarios where each method is applicable to were point out.Besides, based on the improvement to the GCRT(General Chinese Remainder Theorem) used in the distance estimation in RIPS, a new distance estimation algorithm was proposed. Making use of the property of GCRT, this algorithm estimated the unknown distance between nodes by searching the statistical intermediate value of remainder errors and using the intermediate value as the reference item. The theoretical analysis and simulation results show that the estimation accuracy was enhanced and the effectiveness of the method was verified.Finally, the research work was summarized and the potential research topics in future were discussed.