Edinburgh Napier University

  The hotspot issue in wireless sensor networks, with nodes nearest the sink node losing energy fastest and degrading network lifetime, is a well referenced problem. Mobile sink nodes have been proposed as a solution to this. This does not completely remove the hotspot problem though, with nodes the sink passes most closely still expending more energy than others. This study proposes a lightweight algorithm, located in the MAC layer of static nodes and utilising knowledge of predictable sink node mobility. This in order to create a dynamic communication threshold between static nodes and the sink, within which static nodes awaken. Lessening competition for sink communication between nodes. In utilising predictable mobility and factors already known to the static node, such as location and interference range, there is no need for energy consuming messaging. Analysis and simulation results, tested on a lightweight implementation of a carrier-sense multiple access based MAC protocol, shows a significant improvement in energy consumption in both controlled and random environments. With frame delivery improved to the point where sink speed is negated. This when compared to the existing duty cycling approach.