Providing data integrity in intermittently connected Wireless Sensor Networks

Intermittently connected wireless sensor networks (WSN) for scientific environmental monitoring raise the issue for reliable data gathering which is a key factor for having a consistent data stream as a result. First, measurements must be taken and securely saved on a node. Per node local repository for measurements is a basic mechanism for making possible to retransmit any block of data towards a data sink if it has been lost or damaged. Second, high reliable data communication channels are established between nodes, including MAC-layer and application-layer ldquoend-to-endrdquo acknowledgments. The last, and the most important aspect is using a multi-level data buffering mechanism based on an ldquoagingrdquo-factor for reducing power consumption taken by radio transmissions. We describe our solution, combining all these techniques, which is intended for use in a permafrost monitoring project. In our case where half-/hourly measurements are collected over a whole year and nodes can become disconnected for several months, we still manage to provide loss-free and power efficient data delivery.