ABSTRACT
This chapter considers self-localization without any help from an external transmitter. In anchor-based localization, the precise position of a few sensors is known beforehand, possibly using a global positioning system (GPS) receiver. In cooperative localization, the authors use such measured relative distances to determine the shape of the array. The shape can be established but for a few ambiguities, namely, translation, rotation, and mirror image, which may be overcome provided there are three or more anchor sensors. The subspace algorithm used in direction of arrival (DoA) has been shown to be applicable in sensor node localization. Multidimensional Scaling (MDS) is an algorithm that constructs a map of objects by using distances as dissimilarity between sensor nodes. A significant limitation in time of arrival (ToA) estimation arises from imprecise clock synchronization. The ToA still has a large error that can be eliminated only by retransmitting the same message after the same delay. The term for this is double reply.
