Exploring Landmark Placement Strategies for Self-Localization in Wireless Sensor Networks

In this paper, we explore the impact of reference node, or "landmark", placement on the accuracy of the coordinate systems built using topology-based localization techniques. Such techniques employ landmarks to which each node computes its hop-count distance. A node's coordinates is given by the hop-count distance to all landmarks. To our knowledge, our paper is the first to study the impact of landmark placement on the accuracy of the resulting coordinate system. We show that placing landmarks on the periphery of the topology yields more accurate coordinate systems when compared to placing landmarks in the interior of the topology. Nevertheless, our simulation results also show that, in general, if enough landmarks are used, random landmark placement yields comparative performance to placing landmarks on the boundary randomly or equally spaced. This is an important result since boundary placement (especially at equal distances) may turn out to be infeasible and/or prohibitively expensive (in terms of power consumption as well as processing and communication overhead). This is also the first study to consider not only uniform, synthetic topologies, but also, non-uniform topologies resembling more concrete deployments.