HAPIT: An Improvement On Range-Free Localization Algorithm In Wireless Sensor Network And Its Experiment Research

Wireless sensor network is a new network after the internet. It becomes theresearch hotspot among the recent scientific researchers, because wireless sensornetwork includes many special features and can solve many application questions.Wireless sensor network is an entire new technology, which integrates many othersubjects’ knowledge, such as MEMS technology, radio communications and sensortechnology. Likewise, it can be applied to many other fields, such as war, health,forest fire prevention and space exploration and has huge applied value. Itsdevelopment perspective is very wide. Wireless sensor network is constituted bysensor nodes, so localization technology is one of most important supportingtechniques. In order to acquire reliable and valid messages, nodes must locatethemselves accurately.Nowadays localization technologies of wireless sensor network mainly containtwo types. They are range-free and range-based localization technology. The formercosts little energy and could be achieved easily because it needs small minimumhardware configurations. In contrast, the latter’s location accuracy is very high inmany specific conditions. But it needs high requirement of hard configurations andwill cost much energy. For these two reasons, range-free localization technology haswide range of applications in wireless sensor network. This article referring manyscientific literatures firstly introduces wireless sensor network’s architecture andimportant supporting technologies. And localization technologies about wireless sensornetwork are explained in detail. Range-free localization technologies are studiedthoroughly. The recent four range-free localization technologies are analyzed carefully.They are centroid, DV-Hop, Amorphous and APIT localization algorithm. Then thisarticle introduces basic evaluation criterion about localization algorithm. After that, weanalyze APIT localization algorithm’s drawbacks and find that this algorithm’slocalization error comes from In-To-Out error and Out-To-In error. In addition, in thedense node’s circumstance, APIT localization algorithm will cost much more energy and this algorithm has low coverage rate of positioning in the sparse node’scircumstance. For the above weaknesses, this article proposes an improvementalgorithm of APIT named HAPIT localization algorithm. HAPIT algorithm usingtriangle optimal theory decreases the energy consumption effectively in the densenode’s environment. Meanwhile, this algorithm using counter judging and priorityjudging outside decreases the ratio of In-To-Out error in the dense node’s environmentand Out-To-In error in the sparse node’s environment. Additionally, circular overlapregion decision method in HAPIT algorithm increases coverage rate of positioningavailably in the sparse node’s circumstance. The drawback of HAPIT algorithm is thattriangle optimal theory will decrease its positionaI accuracy. This drawback should besolved in the future research.Finally, the author simulates HAPIT and APIT localization algorithm in theMatlab7.0software. Based on three evaluation standards of nodes’ location error,coverage rate of positioning and traffic, we analyze and compare HAPIT and APITlocalization algorithm. With the information from the experiments, in the dense node’scircumstance, location accuracy of HAPIT is6.4%better than APIT and its nodes’coverage rate of positioning is7.9%better than APIT. Also, HAPIT decreases11.3%traffic than APIT.