Topology control and routing in ad hoc networks

An ad hoc wireless network, or simply an ad hoc network, consists of a collection of geographically distributed nodes that communicate with one other over a wireless medium. An ad hoc network differs from cellular networks in that there is no wired infrastructure and the communication capabilities of the network are limited by the battery power of the network nodes. One of the original motivations for ad hoc networks is found in military applications. A classic example of ad hoc networking is network of war fighters and their mobile platforms in battlefields. Indeed, a wealth of early research in the area involved the development of packet-radio networks (PRNs) and survivable radio networks 16. While military applications still dominate the research needs in ad hoc networking, the recent rapid advent of mobile telephony and plethora of personal digital assistants has brought to the fore a number of potential commercial applications of ad hoc networks. Examples are disaster relief, conferencing, home networking, sensor networks, personal area networks, and embedded computing applications 37.The lack of a fixed infrastructure in ad hoc networks implies that any computation on the network needs to be carried out in a decentralized manner. Thus, many of the important problems in ad hoc networking can be formulated as problems in distributed computing. However, there are certain characteristics of ad hoc networks that makes this study somewhat different than traditional work in distributed computing. In this article, we review some of the characteristic features of ad hoc networks, formulate problems and survey research work done in the area. We focus on two basic problem domains: topology control, the problem of computing and maintaining a connected topology among the network nodes, and routing. This article is not intended to be a comprehensive survey on ad hoc networking. The choice of the problems discussed in this article are somewhat biased by the research interests of the author.The remainder of this article is organized as follows. In Section 2, we describe various aspects relevant to modeling ad hoc networks. In Section 3, we discuss topology control. Since the nodes of an ad hoc network are often associated with points in 2-dimensional space, topology control is closely tied to computational geometry; we will briefly review this relationship and extant work in the area. In Section 4, we discuss routing protocols for ad hoc networks. After a brief overview of the many protocols that have been proposed, we discuss alternative approaches based on the adversarial network model.