Research And Realization Of The RSSI-based Positioning Technology For WSN

Wireless sensor network is regarded as one of the most important technologies in 21st century. It is broadly applied in the fields of military, circumstance and industry. Positioning technique is of great importance because of its direct relative to practical application. Aimed at the low-cost and high-flexibility characters of WSN nodes, this thesis studies the positioning technology with RSSI (Received Signal Strength Indicator); it also develops a mine-laneway positioning system grounded on the existing software and hardware platform.Firstly, positioning technology based on signal attenuation model is investigated, which is one part of the technology with RSSI. After deep research on the status quo at home and abroad, this thesis gives out the probability characters of RSSI by mounts of field measure test, and proposes a method based on weighted least-squares approach. Two positioning methods are brought forward aimed at the unknown or incorrect of signal attenuation parameters. For obstruct is one of key problems affecting RSSI based position accuracy, the situations that there are barriers on the transmitting path are tested repetitiously. From the statistical analysis, ML estimation algorithm based on a model of weighted probability is achieved, and experiments testifies this algorithm can improve position accuracy in case of obstruct environment.Secondly, the other part of RSSI based position, namely empirical model positioning method, is discussed. The problem that algorithms cannot adapt to circumstance variety properly is exiting in all empirical models positioning method including neural network. So, this article proposes positioning algorithm on the basis of dynamic database and location beaconing as well as using two rules to control the dynamic adjustment of database. The introduction of different rules can help to gain different position effect. To get further improvement upon position accuracy, the spatial correlation of multi-position results and bayes filter are introduced.Thirdly, CRLB of position estimation is deduced, and a factor that measure the effect of reference nodes'location on position errors called the lower bound of minimum area average position variance is also introduced. By the measuring factor, mathematical model of calculating optimum reference nodes'topology is built, and the result is gained at the lower bound of minimum area average position variance. The conclusion it is of directive significance for nodes'placement.Finally, associated with RSSI-based positioning technology, position subsystem in miner monitoring and management system is designed and implemented. The modules such as information extraction, wire transportation and position calculation are finished using NesC and Microsoft Visual C++ based on embedded operation system TinyOS and windows system. Long-term tests show that the system runs stable and can provide high position accuracy.