Packet-switching broadcast radio networks are receiving considerable attention as a feasible solution for applications involving fast network deployment requirements, inaccessible physical environments, and mobile communication devices. Such networks also offer economic alternatives to traditional multiplexing schemes for local distribution. Most of the published papers relating to packet-switching broadcast radio networks address the case in which all communication devices are within an effective transmission range of the destination receiver, thus forming a single-hop network in which no packet routing is involved. In this paper, we address multihop networks. The problems encountered in packet transportation are identified and strategies to resolve these are proposed.

In this concise paper we described the simulation approach for a general centralized computer communication system with emphasis on efficiency and versatility. The simulation program consists of three modules representing different levels in a hierarchy. The lowest level models the polled multidrop line connecting remote terminals to the concentrator. The second level models the trunk lines and the concentrator which interfaces the multidrop lines of lower speed to one or more higher speed trunk lines connected to a central computer. The highest level models the central computer which communicates with remote terminals via the trunks. A hybrid simulation approach is used to ease program development and to shorten computer running time. When feasible, empirical distributions, analytical formulas, or analytical models are used to eliminate simulation steps and simplify simulation procedures. The techniques developed are illustrated by application to the NASDAQ system.

Abstract Major design problems for centralized computer networks are link layout and capacity assignment. The objective is to select link locations and capacities so that the average time delay required to transmit a message from any node to the central node does not exceed a specified maximum. The design problem is to find the least cost system which satisfies the time delay constraints for given levels of traffic. In this paper, we describe an algorithm to select globally optimum link capacities for specified tree structures. We also give a heuristic method for finding low cost tree structures. The methods have been programmed and are capable of handling networks with thousands of nodes. In addition, they can consider any finite set of link capacities with an arbitrary cost structure and do not depend on the mathematical model used to calculate average time delay.

Abstract This paper considers networks with randomly failing links and nodes. In Part 1, nodes are assumed to be perfectly reliable. A combinatorial analysis is given when all links have equal reliabilities. Two general simulation methods are described. The first is particularly useful if a wide range of failure probabilities is to be considered. The second combines a combinatorial analysis with stratified sampling to yield major computational savings. Later parts will describe generalizations, decomposition methods for large networks and applications to computer network analysis.