Single versus Multi-hop Wireless Reprogramming in Sensor Networks

Wireless reprogramming of the sensor network is useful for uploading new code or for changing the functionality of the existing code. In recent years, the research focus has shifted from single hop reprogramming to multi-hop reprogramming primarily because of its ease of use. Practical experience from a multi-hop sensor network for monitoring water pollution, called CSOnet, deployed in South Bend, IN, indicates that single-hop reprogramming may be preferable under certain conditions to minimize reprogramming time and energy. In this, the user gets close to a node to be reprogrammed and wirelessly reprograms a single node at a time. The choice between single hop and multihop reprogramming depends on factors like network size, node density and most importantly, link reliabilities. We present a protocol called DStream having both single and multi-hop reprogramming capabilities. We provide mathematical analysis and results from testbed experiments and simulations to give insights into the choice of the two reprogramming methods.