Ad-hoc networks

Centralized networks, such as GSM, cannot be used in all situations. Significant examples of such scenarios include establishing survivable, efficient, dynamic communication for rescue operations, disaster relief efforts and military networks. Such network scenarios cannot rely on centralized and organized connectivity, they can be conceived as applications of MANETs. The set of applications for MANETs is diverse, ranging from small, static networks that are constrained by power sources, to large-scale, mobile, highly dynamic networks.

To enable multi-hop communication in a distributed manner, all nodes should be able to act as routers for each other(see Figure 2.1). Routes are set up and maintained by a routing protocol. MANET routing protocol design is a complex issue considering the possible rapidly changing topology of such networks.

For route maintenance one has two main approaches in MANETs, reactive and proactive. Reactive routing protocols set up traffic routes on-demand, whilst proactive protocols attempts to dynamically maintain a full understanding of the topology.

Figure: A traditional base station scheme compared to an ah-hoc multi-hop network.