Improved delay-minimized data harvesting with mobile elements in wireless sensor networks

Using mobile elements as mechanical carriers of data has been shown to be an effective way of prolonging sensor network lifetime and of relaying data in partitioned networks. The existing literature has mostly focused on designing delay minimizing routes for the mobile elements by leveraging variants of the Traveling Salesman Problem (TSP). We show that TSP-based routes can in fact result in data delivery delay arbitrarily worse than that of the optimal solution. The main insight is that as the data generation rates of sensors may vary, some sensors need to be visited more frequently than others. To that end, we consider a network with a single sink and develop a Path Splitter algorithm that “splits” a TSP-based route into several loops intersecting at the sink. Numerical results show that our algorithm can improve average delay by more than 40% in some instances while requiring a modest computational effort to modify the TSP-based route.