Selecting Tracking Principals with Epoch Awareness.

This work addresses the problem of principal node selection during the tracking process in Wireless Sensor Networks (WSNs). In a typical tracking scenario, the location of a mobile unit is determined via collaborative trilateration by the nodes that have the tracked object within their sensing range. One of the participants in the trilateraion---the tracking principal---is in charge of transmitting the location and time information to a designated sink. However, as the moving object changes its location, a new principal needs to be determined and handed off the task of the subsequent sensing, trilateration and transmission to the sink. We observe that in many WSN applications in which sensing/sampling needs to be combined with multihop transmission and, possibly, in-network aggregation, the typical processing is organized in synchronized intervals, called epochs. We postulate that taking the semantics of the epoch into consideration is important when selecting tracking principals and we present efficient algorithmic solutions towards this goal. Our experiments demonstrate that the proposed approach can yield significant reduction in the number of hand-offs between consecutive tracking principals, when compared to previous works.