Graduate School of Global Information and Telecommunication Studies, Waseda University
Abstract of Doctoral Dissertation
Study on Range Free Localization Algorithm in Wireless Sensor Network
無線センサネットワークにおけるレンジフリー位置特定方式 に関する研究
Anup Kumar Paul
Global Information and Telecommunication Studies
Date: June, 2013
ABSTRACT
Wireless sensor networks (WSNs) have been considered as promising tools for many location dependent applications such as area surveillance, search and rescue, mobile tracking and navigation, etc. In addition, the geographic information of sensor nodes can be critical for improving network management, topology planning, packet routing and security. Although localization plays an important role in all those systems, itself is a challenging problem due to extremely limited resources available at each low-cost sensor node.
Previous research generally divides into two groups: range-based and range-free.
Range based methods are accurate but costly for requiring per-node ranging hardware, careful system calibration, or extensive environment profiling.
Range-free approaches feature reduced overhead at the resource constrained sensor node side, nevertheless, with less accuracy depending on anchor density, network connectivity, event distribution, etc. Range free localization algorithm continues to be an important and challenging research topic in anisotropic WSNs. Designing range free localization algorithms without considering obstacles or holes inside the network area does not reflect the real world conditions. This thesis offers novel solutions to bridge the gap between low cost and high accuracy for range-free localization. In this thesis, we have proposed two range free localization algorithms to tolerate network anisotropy.
The first one is Detour Path Angular Information (DPAI) based sensor localization algorithm to accurately estimate the distance between an anchor node and a sensor node. We utilized the Euclidean distance and transmission path distance among anchor nodes to calculate the angle of the transmission path between them one by one. Then the estimated hop distance is adjusted by the angle between the anchor pairs. Based on the angle of the detoured path
(which is the key factor for accuracy), our algorithm determines whether the path is straight or detoured by anisotropic factors.
The second one we proposed is Friendly Anchor Selection Strategy (FASS) in which we show that the selection of friendly anchor nodes,(i.e., anchor nodes which are good for position estimation) instead of using all the anchor nodes for accurate localization is a very important factor especially in anisotropic network.
We first demonstrate that using all the anchor nodes in anisotropic network does not give accurate position estimation. Then we devised the method of selecting friendly anchor nodes for each sensor node in order to get accurate localization.
Our proposed algorithm does not require any global knowledge of network topology to tolerate the network anisotropy nor high sensor node density for satisfactory localization accuracy. Extensive simulations are performed and the results are observed to be in good agreement with the theoretical analysis. DPAI achieved average sensor localization accuracy better than 0.3r in isotropic network and 0.35r in anisotropic network when the sensor density is above 8.
Also FASS can effectively select the friendly anchors from all the anchors in anisotropic network and therefore improve the localization accuracy by finally adjusting the average hop distance by utilizing the information from friendly anchors only.
By investigating into two important branches of range-free localization- dealing with detour transmission path and good anchor selection strategy in anisotropic network - the research presented in this thesis aims at promoting the use of low- cost range-free solutions in real world applications.
