Research On RSSI-Based Localization System In Wireless Sensor Network

Wireless sensor networks consist of nodes that are deployed over an area of interest for the purpose of monitoring special information. The development and integration of MEMS (Micro-Electro-Mechanical System), wireless communication, embedded system and sensor technology, promote the emergence and development of wireless sensor network (WSN). As a new technology, WSN has been applied to many fields including military defence, OA, industry monitor, environment protection and medical treatment. Localization technology, which is one of the three key technologies of WSN, plays an important role in completely monitoring information about the surroundings.The classification and estimate standard of localization algorithms in wireless sensor networks, as well as the methodology of large-scale node localization are given in the thesis. After comprehensive consideration of cubage, power-consumption and cost of the sensor nodes, RSSI (Receive Signal Strength Indication) technology is used to measure distance between nodes. The relation of RSSI and distance is showed by mathematics modeling, as well as the influence factors towards RSSI are analyzed too. The localization algorithm proposed in the thesis contains two stages: the distance measure and the localization. Having finished the first stage of distance measure through RSSI, the nodes calculate their coordinates by running trilateration and maximum likelihood estimation. Simulation model is built by MATLAB, localization error influenced by distance measure error and network connectivity is analyzed. CC2420 RF module and LPC2138 MCU are used to build the hardware platform of nodes in the one-hop and mutil-hop location experiment. The design process of distance measure based on RSSI, localization and simulation of embedded wireless sensor networks is elaborated.Finally, the performance and precision of localization on WSN are verified by testing the nodes localization. This thesis proves that the embedded WSN has many advantages such as low power cost, simple localization and updatability. It provides not only a method for deep study on WSN localization, but also a reference to the application in many fields.