Research And Implementation Of Localization Technology In Wireless Sensor Network

With the rapid development of Wireless Sensor Network (WSN)and its technology, theapplication of WSN is becoming more and more widespread. As localization technology ofWSN is becoming especially valued, scholars at home and abroad have put forward variouslocalization methods. However, these methods are affected by some factors such as physicalenvironment, network connection, communication overhead and computation overhead,which cause kinds of their own limitations. Therefore, to research on localization methods ofWSN suited for practical environment is of great challenge.With comprehensive and in-depth investigation and research, I have certainunderstanding of research status of WSN and its localization technology, and know about andstudy typical localization technology. Referring to WSN products of Crossbow companyand starting with network layer and application layer, I research and implement nodelocalization methods based on WSN. Then I analyze, fuse and improve relevant localizationalgorithm, and implement and verify them on IRIS nodes. At last, I summarize all the workrelated to this paper and discuss the development tendency of future localization technology.The main content of this paper is as follows.Firstly, this paper analyzes the advantages and disadvantages of some typical localizationmethods. For example, for the ranging localization technology, Receive signal StrengthIndicator (RSSI) is more applicable to wireless sensor network application with lower requestfor hardwares, but it is usually influenced by the environment (such as the obstruction andreflection) and its localization accuracy is not high. But for non-ranging localizationtechnology, for example, DV-hop algorithm is easily implemented and is suitable for thelocalization of a wider network range, but there are some consequent problems such as theinstability of hops and a big error of one-hop distance localization. In order to build practicalsystem, this paper studies the characteristics of IRIS which is the current existing hardwareplatform, the software platform of TinyOS and its development process, the programmingmethod of NesC language, and the technical line of developing localization program under theopen-source TinyOS.Secondly, this paper researches and finishes the implementation of RSSI ranging underTinyOS, including the choice of mathematical model of RSSI ranging, experimentalmeasurement and confirmatory analysis of parameters in signal propagation model, and theimplementation process of ranging. We can further understand the way of RSSI ranging which is easily affected by physical environment in experiments, and summarize the rule andcharacteristics that the result is not stable enough and it is just suitable for ranging of shortdistance.Finally, this paper realizes DV-hop localization method based on Collection TreeProtocol (CTP) provided by TinyOS. This method can reduce the interactive communicationtraffic among nods. But it will create the bigger communication traffic of nods besides theroot node, which may cause imbalance of the whole network energy, and the problem ofbigger errores among nods within a distance of one-hop still exists. However, RSSI methodcompensates for bigger localization errores among one-hop nods of DV-hop method byimproving DV-hop algorithm with RSSI method, and also can make mobile nodes location.Experiments prove that to mix two localization methods can reduce localization errores tosome extent, but more significant effect should be further studied owing to the limitedexperimental conditions.