Research And Improvement On Node Location Algorithms In Wireless Sensor Networks

Wireless sensor network is composed of a large number of sensor nodes with information collection,data storage and communication functions in the form of selforganization.It has a wide range of applications in Environmental Science,military,medical and other fields.In the application of wireless sensor networks,it is very important to obtain the coordinate information of sensor nodes when the collected data is related to the location.Therefore,the node location technology is very important in the application of wireless sensor networks.The node location algorithm with low localization error and high energy efficiency is the research hotspot of wireless sensor networks.Aiming at the disadvantages of wireless sensor network node localization algorithm,this paper studies the location problem of sensor nodes from the aspects of location performance,number of network nodes and density of anchor nodes,so as to improve the accuracy of node location and enhance the adaptability of the algorithm to the changeable environment.It focuses on the improvement of RSSI algorithm and DV hop algorithm Optimization.The work and main contents of this article are as follows:(1)Firstly,author discusses the basic theory,algorithm cla ssification and performance evaluation standard of localization algorithm.In addition,the reasons for the localization errors of RSSI algorithm and DV hop algorithm which are widely used in range-based and range-free algorithms are analyzed.The localization accuracy of RSSI algorithm is easily disturbed by uncertain factors such as multi-path propagation and obstacles.When the measurement distance is too large,the error of ra nging will increase;In DV-Hop algorithm,the unreasonable hop number and hop distance between nodes will lead to cumulative error.(2)In order to reduce the ranging error of RSSI algorithm in dynamic environment,an improved RSSI algorithm combining dynamic correction of RSSI model parameters and collaborative localization is proposed to enhance the localization accuracy of unknown nodes.Firstly,the improved algorithm dynamically modify the RSSI model parameters according to the distance and the RSSI values between anchor nodes.Then,the collinearity valid threshold is used to select good anchor node groups,and the coordinates of unknown nodes are estimated by using weighted trilateral positioning.Finally,introducing the idea of cooperative positioning,in which unknown nodes adaptively promote positioned node with high localization accuracy to anchor nodes to participate in cooperative localization.The experimental results show that,the improved algorithm can effectively reduce the error of the estimation distance for unknown nodes,and improve the localization accuracy of unknown nodes under the same environment.(3)In order to improve the location accuracy of DV-Hop algorithm in the uneven networks,an improved DV-Hop algorithm based on RSSI hop quantification and hop distance correction is proposed.Firstly,the improved algorithm quantify the hop counts by the ratio of RSSI value of the nodes to the reference RSSI value,which converts the integer hops into continuous hops,and recalculated the average single-hop distance of anchor nodes based on the quantized hops.Then the average single-hop distance of anchor nodes are weighted to revise the average single-hop distance of unknown nodes.Finally,the distance relationships to the nearest anchor node are utilized to correct the error of the estimation coordinates for unknown nodes to further reduce the localization errors of unknown nodes The experimental results show that the improved algorithm can availably decrease the effect of cumulative error on distance estimation and enhance the localization accuracy of nodes.