Introduction

Multihop structures in wireless networks provide enhanced capacity and fault tolerance. This capacity allows the use of wireless nodes as repeaters, and thus not only enhances the range of communication at low power levels but at the same time short-hop communication causes less spatial interference and allows reuse of the bandwidth available on the frequency channels. The ability for nodes to act as intermediate routers builds into the communication system a natural resilience to node and link failures because alternative paths become available for routing of communications. An important requirement of these networks is that they be self-organizing; i.e., data paths or routes are dynamically restructured with changing topology.

One of the critical issues in the implementation of wireless networks is the design of routing structures and routing protocols. Of considerable importance in this context is the design of distributed efficient algorithms that dynamically update the routing structures. Because the geometric location information regarding the nodes is more readily available, routing algorithms that incorporate this information for effective routing form an increasingly important subject of study.

In this chapter and Chapter 14, we study a number of energy-efficient routing protocols for wireless ad hoc networks. Routing protocols can be categorized as proactive protocols or reactive protocols, depending on when the routing structure is constructed when a routing request is issued from a source node. Routing protocols can also be categorized as flat routing protocols and hierarchical routing protocols.