Active Rfid Location System And To Achieve

RFID(Radio Frequency IDentification)technology is known for low-cost electronic tags and it can be applied in NLOS (Non Line Of Sight). RFID become the best choice of wireless sensor networks which required high-precision, low cost and large number of tags.In this dissertation, distance measurement of RSSI (Received Signal Strength Indication) is used to aid the node localization, but whose maximum measurement error up to 30%; The key point of wireless sensor networks is to solve the problem of position accuracy, computation of the nodes, load of communication and limted storage capacity, so the development direction of wireless sensor networks is to improve position accuracy and reduce energy consumption of nodes; Usually, beacon node is expensive. But low-cost wireless sensor network is required. So it is another difficulty in the wireless sensor network position algorithm to arrange beacon nodes.To solve the problems above, the main works of this dissertation are realized as follow:(1)Make use of RSSI, which is a location algorithm based on power, turns the singal attenuation to distances by changing the gain of the reader, to establish the matching table using experience value.(2) According to the basic principles of node localization, least squares localization algorithm is introduced to solve the problem of beacon nodes inadequate, by upgrating the located node to beacon node.(3) The use of loop refinement and maximum likelihood estimation algorithm for multi-point collaborative localization algorithm reduces the process of positioning error.(4) A method for constructing a small set of methods is proposed, using the idea which can be distributed throughout the wireless sensor network into several small collections, positioning within the small set, and finally into the small collection of an absolute coordinate system, relieve nodes computing, communications, and storage pressure, and this method also avoids the node localization error generated in the process of iteration, improved positioning accuracy, relieve the shortage of beacon nodes.(5) Simulation of the algorithm is given.