Research On Distance Measurement-free Positioning Technology For Wireless Sensor Networks

Wireless sensor networks(WSN)are widely used in military detection,environmental protection,industrial and agricultural applications,smart home and other fields because of their good characteristics.In every application,node location information is a most basic and vital information,thus generating a series of node localization algorithms.According to whether or not it needs ranging,it can be divided into ranging based localization algorithm and range-free localization algorithm.Compared with ranging based localization technology,range-free localization technology has low requirement for hardware configuration and low cost,so it has been widely applied.In the range-free localization algorithms,the DV-Hop algorithm is a classic localization algorithm.In addition,the resolution limit of the localization error is an important index to measure the algorithm.This paper mainly explores the resolution limit of the localization error and the DV-Hop improvement method based on the connectivity of nodes.In this thesis,the limit values of the range-free localization error calculated by the predecessors are not the true limit values of the range-free localization error resolution.In this paper,the resolution limit of the localization error of distance measurement and localization error under the ideal channel is solved,and the concept of the critical point is introduced,and all the critical points are taken out.According to the critical point,the maximum movable distance of the unknown node along a certain direction is solved,and the maximum movable distance in all directions is further solved,that is the range-free localization error resolution limit.Then,considering the shadow fading factors in the actual communication environment,we use the logarithmic distance path loss model to obtain the relationship between the node communication range and the shadow fading,and solve the resolution limit of the localization error in the shadow fading channel.Finally,the correctness of our algorithm is verified by simulation results.In order to reduce the localization error of the existing DV-Hop algorithm,this paper proposes a DV-Hop improvement method based on the node connection relationship,which is divided into two algorithms,centralized and distributed.In the centralized algorithm,the network memory is responsible for dealing with the computing task of the whole network in a central node.It improves the DV-Hop localization result continuously so that the final node connection conforms to the real connection between the nodes.In a distributed algorithm,each node processes information by itself,which makes the final node connection consistent with the real connection of the nodes in the two hop by improving the DV-Hop localization result continuously.Simulation results show that our improved algorithm can reduce the localization error on the basis of the DV-Hop algorithm.