TABLE OF CONTENTS Ad hoc networks [1] offer a radical alternative to existing cellular and fixed networks for providing communications. These networks form on the fly from the communications devices themselves without needing any infrastructure or centralised control. Devices communicate directly with each other and by forming chains of transceivers they relay information through other devices in order to reach the final destination (see Fig 6.1). The devices also learn about their peers and then use this intelligence to route information via the optimum path taking into account such things as processing power, battery capacity and alternative network connections such as broadband or GPRS. The network therefore works as a symbiosis.
An ad hoc approach to creating such networks is not new. Packet radio and multi-hop networks have been the subject of research for nearly 30 years and have been deployed by the military for some time. However, technology has now advanced to a point where these networks can be deployed in large numbers at low cost.
Wireless connectivity has become an integral feature of many portable devices such as laptops and PDAs, and in the coming years this trend is certain to extend across a vast array of everyday devices ranging from pens to cars and into fixed structures such as buildings and streetlights. In a future with devices everywhere, wireless capability will be present in sensors, clothes, food packaging and a host of other everyday objects.
