Study On Range-free Based Node Self-Location Algorithms For Wireless Sensor Networks

With recent advances in sensor technology, low-power electronics, and low-power radio frequency design have enabled the development of inexpensive and low-power wireless sensors network, where each sensor node individually senses the environment but collaboratively achieves complex information gathering and dissemination tasks. Wireless sensor network can be applied to many areas such as military affairs, commerce, medical care, environmental monitoring, and becomes a new research focus in computer and communication fields. Many applications of wireless sensor networks are based on sensor self-positioning. Because of constraints in size, power, and cost of construction of sensor nodes, the investigation of efficient location algorithms which satisfy the basic accuracy requirement for WSN meet new challenge.In the recent investigation the location technology for WSN can be divided into two categories: Range-based approaches and Range-free approaches. Range-based methods have better accuracy, but require additional hardware at the sensor nodes, which are not available on regular application fort of sensor networks. Acknowledging that the cost of hardware required by range-based solutions may be inappropriate in relation to the required location precision, researchers have sought alternate range-free solutions to the localization problem in sensor networks. Because of the hardware limitations of WSN devices, solutions in range-free localization are being pursued as a cost-effective alternative to more expensive range-based approaches. The range-free algorithm makes no assumption about the availability or validity of range information. In allusion to the special self-organizing network WSN, Range- free has been abroad attented by the scientific researcher. Because of the advantages on power and cost on sensor node, the thesis focuses on investigation of range-free algorithm for WSN. First of all, the research status of wireless location techniques and position-ning systems for WSN are summarized based on the study of a lot of related literatures; followly, the system structure and solf-hardware of network node for WSN are summarized; also referring the inherent and bright characteristic knowing from the other wireless network and introducing the wide application value. Secondly, Localizationing mode of the network node are analyzed; And mainly introduce representative several arithmetic, which have been compered .Then, analyse the novel localization algorithm APIT which is based on lapped area and its disadvantage, and put forward a new algorithm ROCRSSI, which is presented and simulated, the results show that it has the better positioning accuracy and coverage, but less communication overhead and compute time than APIT. According to the issue of ROCRSSI in the practical application in WSN which can not orient mass nodes in the network once, utilizeing the iterative approach to improve the density of anchor nodes gradually and enhance the location coverage, a novel distributed, simple positioning algorithm, referred to as ROCRSSI~+, is presented and simulated; the results show that it has better practical application value.In the end, Conclusion for the thesis and prospect for the future research work.