Joint localization and transmit-ambiguity resolution for ultra-low energy wireless sensors

Abstract

Technological advances in the miniaturization of millimeter-sized sensor motes facilitate new application cases where the motes' inherent energy constraints enforce radical changes with respect to the sensors' communication procedures. An upcoming application scenario is the surveying and exploration of hardly permeable and hardly accessible underground environments such as those of oil-sand mining areas. This scenario requires ten-thousands of millimeter-sized sensor motes (outer diameter less than 5mm) to examine the resource wealth. Within this scope, a correspondingly large amount of extremely resource constrained sensors motes need to have the possibility to sense their environment and interact with each other. In order to enable such application cases, significant energy savings are necessary. An interesting and promising approach is to shorten the sensors' DS-CDMA code sequences and, thereby, reduce the communication related energy costs. In this work, we investigate the resulting downsides of this approach on the range-based localization. As the code shortening leads to the problem of nonunique transmitter identification and consequently non-relatable pairwise distance measurements, the localization of the sensors by typical means is prevented in the first place. This is because multiple sensor motes will concurrently use the same transmit-codes. In this regard, we propose an approach which enables the joint localization and ambiguity resolution and reduces the complexity compared to sequential approaches where at fist the transmit-ambiguities are resolved and a localization with typical methods is performed subsequently.