Research And Implementation Of Node Localization And Data Fusion For Wireless Sensor Networks

The primary advantages of wireless sensor networks include reduction of system wiring, high monitoring accuracy, convenience for remote supervisory controlling, easiness of system diagnosis and maintenance, good fault-tolerant ability, and etc. There is wide application prospect of wireless sensor networks in such fields as networked manufacturing, intelligent manufacturing and so on. The basic task of wireless sensor networks is to obtain valuable information of the physical world accurately. Wireless sensor networks can realize high speed and low time-delay message exchange among sensor nodes depending on the time and position information. So it ensures the high precision and real-time characteristic of the whole system. Wireless sensor networks face many-sided restrictions such as calculation, storage and network bandwidth. It is very important for wireless sensor networks to investigate the system architecture, clock synchronization, node localization, data fusion, and etc.First of all, the system architecture and related theories of wireless sensor networks were studied and discussed in detail. Then a kind of novel system hierarchical model of wireless sensor networks was proposed. The traditional network system architecture offers the network transmission support for various kinds of application program with the purpose of data transmission.The network node only has a transmission function, and it doesn't need to deal with any data exchange. On the contrary, wireless sensor networks is focus on sensing data, of which the aim is to obtain more accurate characteristic information of the perceived targets for a long time. Design of this system architecture followed the principle of energy conservation. It has simplified the non-main function in the traditional network as much as possible, and it has merged the transmission layers of OSI model into the network layer. At the same time, data fusion technology was also used in the networks protocol so as to achieve the goal of saving storage resources and reducing network bandwidth occupation.Clock synchronization mechanism of sensor nodes in wireless sensor networks was analysed, a kind of time synchronization algorithm based on time-stamp was presented. The main characteristic of the algorithm based on time-stamp was to make time-stamp transformation according to the asynchronous clock sensor nodes'time-scale. And it didn't carry out synchronization among the nodes directly. Since the time-stamp information can be taken by existing exchanged messages, this method was energy-effective. The experiment result indicated the proposed algorithm was able to obtain a synchronization precision of one millisecond in order of magnitude, which could satisfy most of the practical applications of wireless sensor networks.The basic principles of node localization scheme for wireless sensor networks were discussed thoroughly. Then a new kind of localization algorithm based on Monte Carlo method was proposed, which was suitable for wireless sensor networks with node mobility (Monte Carlo Localization, MCL). MCL algorithm can obtain much higher precision than several other traditional localization methods under condition of the sensor node's movement uncontrollable. The method didn't need any extra hardware facilities, and it could solve node's localization problem for wireless sensor networks with mobility.The data fusion technology in wireless sensor networks was studied deeply, a kind of Distributed K-mean Clustering algorithm for Wireless Sensor Networks (DKCWSN) and data fusion algorithm based on self-adapting weight were presented. DKCWSN algorithm could realize sensor nodes'fast clustering throughout the whole network. After the sensor nodes were divided into many groups reasonably, the simple data fusion algorithm based on self-adapting weight could make correct decision, and it was able to deal with the received sensing data to obtain more reasonable result according to the corresponding weight size. This method is simple, practical, and the redundant degree of data in the network could be decreased to a great extent. Samely, it could save storage resources and bandwidth occupation of the network. The algorithms had been implemented among the prototype system, and experiment result showed that the algorithms had good execution efficiency and very kind expansibility.In the end, on the basis of the methods mentioned above, a mobile robot navigation prototype system using wireless sensor networks node position information was realized. The wireless sensor networks with ZigBee protocol had been studied in detail, and an embedded granary measuring and controlling system using this kind of ZigBee wireless sensor networks was developed. The wireless sensor networks based on ZigBee protocol could be widely used in such fields as long-range measuring and controlling system, telemedicine, public traffic, public information inquiry, and etc.