Ad Hoc and Sensor Networks

Abstract

Although the Internet has penetrated virtually every aspect of our lives, many scenarios exist where an existing network infrastructure is not available. For example, a hurricane may destroy buildings where the critical networking equipment is housed or may cut the power supply to the equipment. In such scenarios, it is extremely important for people living in the disaster area, as well as relief workers, to communicate with each other using whatever networking devices they have, without relying on any existing infrastructure. Such an infrastructureless network is called an ad hoc network , more specifically, “a network that is setup, literally, for a specific purpose, to meet a quickly appearing communication need” (1). In addition to supporting human communication, an ad hoc network may be used for other purposes, such as monitoring the physical environment and detecting events (as we will explain later). An ad hoc network can be wired or wireless, but more research effort has been focused on wireless ad hoc networks as they are easier to establish and do not restrict the mobility of users. Major research issues in wireless ad hoc networks include, but are not limited to, how to ensure connectivity among nodes in the face of unplanned deployment, controlled or uncontrolled mobility, and nodes leaving/joining the network (potentially as a result of failures/repairs); how to access efficiently the shared wireless medium in a distributed fashion; how to route packets to their destinations in the presence of topology dynamics (because of mobility and failures) and sometimes intermittent connectivity; and how to meet the quality of service (QoS) requirements with distributed resource management. These issues are made even more challenging by the limited resource availability that is typical of a wireless ad hoc network.