Guest editorial wireless ad hoc networks

B ECAUSE the subject of this issue is wireless ad hoc networks, it would be beneficial to provide a definition of the phrase ad hoc as it is used in the context of mobile wireless networks. We have as a starting point the common definitions of this phrase, such as " for a specific purpose or occasion " or " for this case alone, " and many of us have served on at least one ad hoc committee. But there seems to be a gap between this use of ad hoc and the use of ad hoc in the phrase " wireless ad hoc networks, " which suggests that a more descriptive name should be sought. We have not discovered a universally accepted definition of wireless ad hoc networks, but there are a few features that are shared by most descriptions of such networks that have appeared in the literature. In a wireless ad hoc network, there is no predetermined topology and no central control. Ad hoc networks do not rely on a preexisting fixed infrastructure, such as a wireline backbone network or a base station. The nodes in an ad hoc network communicate without wired connections among themselves by creating a network " on the fly. " The responsibilities for organizing and controlling the network are distributed among the terminals themselves. The entire network is mobile, and the individual terminals are allowed to move at will relative to each other. In an ad hoc network, some pairs of terminals may not be able to communicate directly with each other and relaying of some messages is required, so that they are delivered to their destinations. Such networks are often referred to as multihop or store-and-forward networks. Based on these features, standard cellular networks and wireless fully connected networks do not qualify as ad hoc networks. Probably the chief difference between ad hoc networks and conventional cellular technology is the apparent lack of a centralized entity within an ad hoc network. There are no base stations or mobile switching centers in an ad hoc network. Consequently, all network protocols must operate in a distributed manner. The interest in wireless ad hoc networks stems from some of their well-known advantages for certain types of applications. Since there is no fixed infrastructure, a wireless ad hoc network can be deployed quickly. Thus, such networks can be used in situations where either there is …