Resource Management in Heterogeneous Wireless Sensor Networks

Heterogeneous wireless sensor networks such as High Performance Wireless Research and Education Network (HPWREN) have environmental sensors located in remote and hard-to-reach locations far from the main high-bandwidth data links. The sensed data needs to be routed through multiple hops before reaching the backbone. The routing is done by battery-powered nodes using license free radios such as 802.11. Minimizing energy consumption is critical to maintaining operational data links. This paper presents a solution that includes scheduling and routing algorithms and achieves up to 60% energy savings per battery operated node with 20% lower latency when compared to existing techniques. Our TDMA based scheduling algorithm limits the number of active nodes and allows a large portion of nodes to sleep thus saving energy. Since the algorithm is completely distributed and hence minimum (at join time) control packet exchange is required, nodes in sleep state can switch off the wireless network interface thus minimizing power consumption. Furthermore, results show that by limiting the number of active nodes, contention in the channel decreases and hence aggregate throughput increases up to 10%. Scheduling is combined with a dynamic creation of a backbone of nodes in charge of providing connectivity to the network and delivering data to the proper destinations. This mechanism sits on top of the unmodified MAC layer so that legacy network devices can be used, and expensive hardware/software modifications are avoided.