Research On APIT Localization Algorithm In Wireless Sensor Network

Research of wireless sensor network(WSN) began in late 90^th,20 century and developed quickly at the beginning of 21st century.WSN is used in military,medical treatment,environment protection,traffic,and so on.It requires that we provide the sensing data with certain location of nodes.Given to the constraint of cost,volume and power of nodes,the present matured Global Positioning System(GPS) is not appropriate for localization of nodes in WSN.So,it has world-wide application background and vital value to research the appropriate localization algorithms in WSN.This paper analyzes deeply on APIT localization algorithm.Then we introduce its improved algorithm,which we called IAPIT,to promote the coverage range of APIT. The method of IAPIT is described as follows:first,we classify the nodes into two kinds:one is suitable to APIT's localization condition;the other is not.We use APIT to get the estimation position of the unknown nodes for the former.While we mainly deal with the latter in two ways.First,if the number of anchor nodes of unknown node is more than three,we choose trilateration to locate it.Second,if the number of anchor nodes is two,at first,we calculate the two points of two circles whose corresponding centers are the locations of two anchor nodes and whose radiuses are the corresponding distance of two anchors away from the unknown node;then we may decide which point is the estimation position of the unknown node based on other conditions.We use C++ and MATLAB to emulate IAPIT and compare it to APIT differently under the different anchor ratios,different communication radius of nodes and the same anchor ratio.The result sufficiently shows that IAPIT promotes localization coverage of APIT and its localization precision is suitable for the requirement of real applications.