We consider the problem of distributed deterministic broadcasting in radio networks of unknown topology and size. The network is synchronous. If a node u can be reached from two nodes which send messages in the same round, none of the messages is received by u. Such messages block each other and node u either hears the noise of interference of messages, enabling it to detect a collision, or does not hear anything at all, depending on the model. We assume that nodes know neither the topology nor the size of the network, nor even their immediate neighborhood. The initial knowledge of every node is limited to its own label. Such networks are called ad hoc multi-hop networks. We study the time of deterministic broadcasting under this scenario.For the model without collision detection, we develop a linear-time broadcasting algorithm for symmetric graphs, which is optimal, and an algorithm for arbitrary n-node graphs, working in time O(n 11/6 ). Next we show that broadcasting with acknowledgement is not possible in this model at all.For the model with collision detection, we develop efficient algorithms for broadcasting and for acknowledged broadcasting in strongly connected graphs.

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A communication network is called a radio network if its nodes exchange messages in the following restricted way. First, a send operation performed by a node delivers copies of the same message to all directly reachable nodes. Secondly, a node can successfully receive an incoming message only if exactly one of its neighbors sent a message in that step. It is this semantics of how ports at nodes send and receive messages that defines the networks rather than the fact that only radio waves are used as a medium of communication; but if that is the case then just a single frequency is used. We discuss algorithmic aspects of exchanging information in such networks, concentrating on distributed randomized protocols. Specific problems and solutions depend a lot on the topology of the underlying reachability graph and how much the nodes know about it. In single-hop networks each pair of nodes can communicate directly. This kind of networks is also known as the multiple access channel. Popular broadcasting protocols used on such channels are Aloha and the exponential backoff. Multi-hop networks may have arbitrary topology and packets need to be routed hopping through a sequence of adjacent nodes. Distributed protocols run by such networks are usually robust enough not to expect the nodes to know their neighbors. These ad-hoc networks and protocols model the situation when nodes are mobile and do not rely on a fixed infrastructure.The advent of new technologies in both computers and telecommunication has caused a proliferation of computer networks. The ubiquitous cellular phones and portable computers have made wireless communication and mobile computation part of our daily experience.Computer/communication networks are collections of information-processing nodes which communicate among themselves. Nodes are often independent units and the purpose of communication is to carry out distributed computation by sharing distributed resources. Such networks need communication protocols that are versatile enough to handle arbitrary patterns of communication and bursty traffic.Various taxonomies of communication networks are possible. One of them is based on scale, that is, the size and distance among nodes; most popular categories are local area networks (LANs), like all the computers on a campus, and wide area networks (WANs), like all the hosts of academic institutions in a country. Another classification may be based on the technology used for transmission; nodes may be connected by copper wire or optical fiber or a network may be wireless. Yet another distinction is by the criterion if all the nodes are stationary or rather some are mobile.Another classification is into the following two types: broadcast networks and point-to-point networks. The former are a number of nodes which share a communication channel; a packet sent by any node is received by all the nodes. A point-to-point network is a collection of nodes of which certain pairs are connected by transmission links; a packet sent from a node and destined at some specifi...

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