Recovery Mechanism for Diff-based Reprogramming in WSNs

Abstract

Reprogramming remote sensor nodes on wireless sensor networks (WSNs) allows the software on them to be dynamically updated or enhanced for adapting to changed environmental conditions or application requirements. Many researches use diff-based approaches to transmit only the code difference to sensor nodes for updating, but failure of diff-based reprogramming may cause extra problems. Because sensor node's storage is limited, the older version of patch files may be overwritten by the next one. Then after many times of update, reprogramming recovery mechanism will lack the intermediate version of patch files for incremental recovery. To recover from this situation, extra data retransmission is needed and the host machine should issue recovery commands, but both of them will also affect all other normal nodes in WSN. The data retransmission is especially unacceptable in a resource-limited WSN environment. To solve these problems, we have proposed two new diff-based recovery mechanisms named N and N-1 Incremental Recovery to recover sensor nodes from reprogramming failures. We implement the proposed mechanism in TinyOS and choose Two-Stage Diff as our diff-based dynamic update mechanism for updating the software on sensor nodes. Experiments with the modified TinyOS show that our N and N-1 Incremental Recovery compared with the Deluge default recovery mechanism can greatly reduce the amount of retransmitted data and the processing time can be significantly reduced as well.