Wireless Sensor and Actuator Networks: Algorithms and Protocols for Scalable Coordination and Data Communication

2.1 BACKBONES

A backbone is a subset of nodes that are able to perform assigned tasks and serve nodes which are not in the backbone. Thus, the backbone construction depends on the task to be carried. This chapter deals with backbones for the communication between nodes. The next chapter will discuss backbones for sensor area coverage.

The exact definition depends on the tasks or the particular desirable properties of the backbone. In wireless sensor networks, a backbone could be the set of active sensors while the rest of the sensors are sleeping (the problem of deciding which sensors should be active is often called the activity scheduling problem). The backbone of a network is normally required to be connected, such that the backbone nodes are able to communicate to perform assigned tasks. For instance, connected backbone nodes in ad hoc networks can perform efficient routing and broadcasting. Use of a backbone in wireless sensor networks could not only prolong the network lifetime, but could also make the operation of the network efficient. For instance, typical broadcasting in sensor networks is normally flooding-based, where each node retransmits the broadcasting message that it receives. Only nodes in the connected backbone retransmit the message in backbone broadcasting. Broadcasting via backbone could avoid a lot of useless retransmissions especially for dense networks. Backbones are often used to improve the routing procedure. A source node forwards the message to a backbone ...