In this chapter, various classes of networks are considered, with particular emphasis on networks in which the energy of the nodes making up the network is constrained. Networking is classically treated as an abstraction that sits on top of the MAC layer, being concerned with issues such as the quality of service experienced by a message as it traverses some route or set of routes through a network. Quality of service issues include delay and the error rate. Packets that go through the network and fail to meet delay constraints due to congestion of particular links or that fail to meet error rate requirements due to noise, interference, or fading are dropped. Quality of service requirements come from higher levels, such as the application, with end to end (sender to recipient) guarantees of message integrity also provided by these upper layers in the form of ARQ protocols. Here the focus will be on the formation of the network, the establishment of routes between sender–recipient pairs, how delay arises in networks and how it can be mitigated, network layer interactions for sensor networks, and information theoretic limits on network performance.

Network topology

Various network topologies are illustrated in Figure 8.1. In a star network, all information flows to and from a single hub which usually acts as the master for determination of synchronization and channel access, with the remaining nodes denoted as slaves.