Robust routing and energy management in wireless sensor networks

Wireless sensor networks are deployed in a wide range of applications such as habitat, environmental, and structural health monitoring. These networks have several sources of dynamics across the wireless protocol stack, which make it challenging to build robust systems. Sensor network systems must adapt to these dynamics while remaining efficient. There is an emerging class of dynamically-taskable sensor networks that can support multiple and concurrent applications. In such networks, of which Tenet is an example, the protocols must adapt to the changing application workload. The dynamics at the physical, link, and network layers directly affect routing and forwarding protocol performance. The quality of wireless channel or the network topology can change rapidly even in a stationary network. The routing protocols must quickly detect these dynamics and take steps to maintain robust and efficient routing paths. We use Application-informed Energy Management (AEM) and Collection Tree Protocol (CTP) as case studies in our study of the type of dynamics present in sensor networks and present techniques that make these protocols robust and energy-efficient. AEM can adapt to the application dynamics at the time scale of application injection and link layer dynamics at the time scale of link quality changes to provide robust and efficient duty-cycles in sensor networks. CTP can adapt to the changes in physical and link layers at the time-scale of link coherence and packet transmissions, and changes in network topology at the time-scale of network events such as node introduction, deletion, and topology changes. Our findings suggest that agility at the time scale of the dynamics is critical to the design of robust and energy-efficient protocols.