Ad hoc networks 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 con nections such as broadband or GPRS.