Impact of Information on the Complexity of Asynchronous Radio Broadcasting

We consider asynchronous deterministic broadcasting in radio networks. An execution of a broadcasting protocol is a series of events, each of which consists of simultaneous transmitting or delivering of messages. The aim is to transmit the source message to all nodes of the network. If two messages are delivered simultaneously to a node, a collision occurs and this node does not hear anything. An asynchronous adversary may delay message deliveries, so as to create unwanted collisions and interfere with message dissemination. The total number of message transmissions executed by a protocol in the worst case is called the work of the protocol, and is used as the measure of its complexity. The aim of this paper is to study how various types of information available to nodes influence the optimal work of an asynchronous broadcasting protocol. This information may concern past events possibly affecting the behavior of nodes (adaptive vs. oblivious protocols), or may concern the topology of the network or some of its parameters. We show that decreasing the knowledge available to nodes may cause exponential increase of work of an asynchronous broadcasting protocol, and in some cases may even make broadcasting impossible. keywords: algorithm, asynchronous adversary, deterministic broadcasting, unit disc graph, radio network.