| In heterogeneous wireless sensor networks (HWSNs) such as HPWREN, the sensed data needs to be routed through multiple hops before reaching the main high-bandwidth data links. The routing is done by battery-powered nodes using license free radios such as 802.11. In this context, minimizing energy consumption is critical to maintaining operational data links.;This thesis presents a novel routing mechanism for HWSNs that achieves large energy savings while delivering data efficiently. 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. Thus, our approach is inexpensive and easily deployable. Our solution includes scheduling and routing algorithms.;The TDMA-based distributed scheduling algorithm limits the number of active nodes and allows a large portion of nodes to sleep thus saving energy. Simulations and measurements on a testbed network show that scheduling can achieve as much as 85% power savings and up to 10% increase in throughput.;Scheduling is combined with the creation of a backbone of nodes that provides connectivity and delivers data to the proper destinations. The nodes of the backbone stay awake continuously for a predefined amount of time. Since it is an energy expensive task, they are dynamically selected so that those nodes that have more energy are more likely to become part of the backbone.;Simulation results show that the combined scheduling and forwarding backbone approach achieves up to 60% energy savings per battery operated node and also have better performance when compared to existing techniques. |
