Harnessing Non-Uniform Transmit Power Levels for Improved Sequence Based Localization

Sequence-based localization (SBL) is a technique whereby a node is localized based on the ranked sequence of signal strengths obtained from a set of beacon nodes. SBL effectively partitions the area into regions corresponding to unique ranked sequences. Prior work has developed SBL under the assumption that all beacons have the same transmit power. In this work, we consider beacons with unequal transmit power for sequence-based localization and present heuristic algorithms for joint transmit power optimization and beacon placement. We show through comprehensive simulations that a novel enhancement of SBL utilizing optimized non-uniform transmit powers, coupled with careful beacon placement, which we refer to as NU-SBL, can dramatically improve the area partitioning compared to traditional SBL. However, in evaluating these schemes under stochastic fading, we find that the original SBL with optimized location performs nearly as well or slightly better than NU-SBL in many cases. We introduce another scheme, that we refer to as NU-SBL-ZOOM, which further allows the power levels to be optimized non-uniformly so as to focus in on a particular smaller region within the larger localization space. NU-SBL-ZOOM is found to perform much better in terms of both area partitioning as well as location error in the presence of fading.