Improving information availability in storage-centric sensor networks

We address the issue of improving information availability in a class of delay-tolerant sensor network applications, where the sensor nodes are deployed in disconnected environments. In such environments, since there is no continuous access to a remote base station, there is a need to leverage the collaborative resources of the sensor network to support in-network storage. The stored data can then be retrieved opportunistically by mobile collectors in the proximity. We have developed a data-centric, in-network storage architecture that partitions the network into storage zones. In such a scheme, some of the storage nodes may be unavailable at the time of storage and retrieval, because they are either sleeping to conserve energy or because they have failed.We present two schemes based on random linear network coding for improving information availability within such a storage architecture. In the centralized scheme, the encoding is performed by the managers in each storage zone, whereas in the decentralized scheme, the encoding is done locally by the zone members. We have implemented the network coding schemes in TinyOS and we present results that show the impact of the zone size, duty cycle, and the degree of encoding on the decoding probability, based on our experiments on a testbed of Micaz motes.