Heuristic for Page-Based Incremental Reprogramming of Wireless Sensor Nodes

Wireless sensor nodes may need code updates for a variety of reasons. These updates are costly in terms of energy and can lead to early battery failure. Incremental reprogramming can save energy by reusing the existing code image on the node and transmitting only a delta file. It can not be assumed that the flash memory is randomly erasable and programmable. When updating the flash page by page, usable data could be unintentionally overwritten, which increases the size of the delta. This paper proposes heuristics for page-based incremental reprogramming of wireless sensor nodes, to find a good sequence for pages in the flash memory to be updated that lead to an overall smaller delta file. A graph model for page dependencies is presented, graph-based algorithms are proposed and page dependency weights are estimated. Results show that the page update sequence can have a significant impact on the size of the delta file.