Replica Arrangement Scheme for Location Dependent Information on Sensor Networks with Unpredictable Query Frequency

Storing data on sensor nodes at a specified location is a useful technique for data-centric storage and management of location dependent data on wireless sensor networks. To decrease the cost of accessing these data, arranging replicas of data so that the distance between the consumer nodes and replica holder nodes decreases is desirable. Conventional schemes, however, are costly for updating the replicas even if they are not often used or do not support functions for ensuring their consistency. We propose a novel replica arrangement scheme, which adaptively arranges replicas at positions close to nodes for frequent sending of queries. Instead of arranging many replicas on sensor nodes, our scheme consists of nodes with pointers that point to the replica holder nodes in order to save storage for replicas. The pointers, which are smaller than replicas, are arranged so that nodes are in circular arcs surrounding the location where the original data item is associated. Simulation results show that our scheme outperforms conventional replica arrangement schemes in terms of the cost required for sending queries and replies with sufficiently low replica update cost.