Design And Implementation Of Location System Based On Wireless Networks

Wireless location refers to the use of wireless communication resources, and is a technology which used to get the position of the target in some coordinate system by measuring or estimating some signal parameter, and using some location algorithm. There are two kinds of wireless location: satellite-based wireless location and ground-based wireless location. The ground-based wireless location is divided into location system based on public mobile communication, location system based on wireless sensor and location system based on wireless networks.According the principles of wireless location , this paper designs and implements a location system based on wireless networks , which does not rely on satellites and CDMA or GSM station and can be applied effectively to the indoor location and outdoor location of the prison and jail. In this paper, the main work is as follows:(1) Introduces the principles of wireless location and kinds of algorithms of the two phases of location.(2) Implements the system communication protocol, synchronous and the target'low-power based on the WOR of CC2500 and the LPM4, LPM3 of MSP430F2274.(3) In order to resolve the signal's collision and conflict: in the adjacent region, the system uses frequency division multiplexing, in the same region, the system uses time division multiplexing, and before sending signal, the target uses detection of carrier based on TX-if-CCA of CC2500 to determine whether the channel is idle.(4) The part of outdoor location uses RSSI-based location of radio frequency. The part of indoor location uses the ultrasonic communication to implement of the TOA-based location, and before sending the ultrasonic signal the target also sends the radio frequency signal to carry some useful information and to help the base station find the time of ultrasonic signal sends. In the small space, the system uses proximity location by radio frequency communication. The synchronization of all these locations are implemented by radio frequency.(5) Do some experiments with this system. When locate only a static target, the deviation of 8m*8m indoor is between 0.3m and 0.8m, the deviation of 20m*20m outdoor is between 0.4 and 1.1m. When locate many dynamic targets, there are some measured errors and omissions, but there are not the situation that the same target is missed in the successive location tests.