Optimal Anchor Placement for Localization in Large-Scale Wireless Sensor Networks

Abstract

In wireless sensor networks (WSNs), location information of sensor nodes (or simply sensors) plays a vital role in both of the management of WNSs and many other applications. Due to the constraints on costs and energy, only a small portion of nodes in a WSN is deployed as anchor nodes or simply anchors with their locations a priori known or determined through certain hardware (e.g. GPS) to localize normal sensor nodes. However, the placement of such anchors has significant influence on the localization performance of sensor nodes. This paper tackles the problem of optimal anchor placement for localization in large-scale WSNs. But, differently from existing studies assuming independent and identically distributed measurement noises, this paper takes into account more practical distance dependent measurement noises. Then, provided that sensors' locations satisfy a homogeneous Poisson Point process, a theoretical analysis based on the average Cramer-Rao Lower Bound (CRLB) proves that it is optimal to place anchors in a regular fashion. In particular, given that each sensor can measure distances to nearby 3 anchors, the optimal anchor placement pattern is the equilateral triangle pattern, which is consistent with the optimal node deployment for 3-coverage and 6-connectivity. This study not only provides the knowledge for guiding the deployment of large-scale WSNs in practice, but also paves the way for building the theory of sensor localization in WSNs.