Artificial intelligence research is ushering in a new era of sophisticated, mass-market transportation technology. While computers can already fly a passenger jet better than a trained human pilot, people are still faced with the dangerous yet tedious task of driving automobiles. Intelligent Transportation Systems (ITS) is the field that focuses on integrating information technology with vehicles and transportation infrastructure to make transportation safer, cheaper, and more efficient. Recent advances in ITS point to a future in which vehicles themselves handle the vast majority of the driving task. Once autonomous vehicles become popular, autonomous interactions amongst multiple vehicles will be possible. Current methods of vehicle coordination, which are all designed to work with human drivers, will be outdated. The bottleneck for roadway efficiency will no longer be the drivers, but rather the mechanism by which those drivers' actions are coordinated. While open-road driving is a well-studied and more-or-less-solved problem, urban traffic scenarios, especially intersections, are much more challenging. We believe current methods for controlling traffic, specifically at intersections, will not be able to take advantage of the increased sensitivity and precision of autonomous vehicles as compared to human drivers. In this article, we suggest an alternative mechanism for coordinating the movement of autonomous vehicles through intersections. Drivers and intersections in this mechanism are treated as autonomous agents in a multiagent system. In this multiagent system, intersections use a new reservation-based approach built around a detailed communication protocol, which we also present. We demonstrate in simulation that our new mechanism has the potential to significantly outperform current intersection control technology -- traffic lights and stop signs. Because our mechanism can emulate a traffic light or stop sign, it subsumes the most popular current methods of intersection control. This article also presents two extensions to the mechanism. The first extension allows the system to control human-driven vehicles in addition to autonomous vehicles. The second gives priority to emergency vehicles without significant cost to civilian vehicles. The mechanism, including both extensions, is implemented and tested in simulation, and we present experimental results that strongly attest to the efficacy of this approach.

This paper investigates the problem of finding optimal multicast virtual topologies, with respect to minimizing the maximum hop distance, in wavelength-division multiplexing multicast trees. Although the problem of finding optimal multicast trees is itself known to be NP-complete under many optimization metrics, high-quality approximation algorithms are known for this problem. We investigate the case that a multicast tree has been selected and seek to embed an optimal virtual topology in this multicast tree. We show that the problem can be solved in polynomial time when tap-and-continue switches are employed, which allow a lightpath to be tapped by some number of intermediate nodes. However, the problem becomes NP-complete when fully multicast-capable switches are employed. Our results suggest that tap-and-continue switches can be used to obtain high-quality multicast virtual topologies, while heuristics will be required to find good solutions in fully multicast-capable networks.

In this paper we examine the problem of constructing optimal virtual topologies for one-to-many communication in optical networks employing wavelength-division multiplexing. A virtual topology is a collection of optical lightpaths embedded in a physical topology. A packet sent from the source node travels over one or more lightpaths en route to its destination. Within a lightpath, transmission is entirely optical. At the terminus of a lightpath the data is converted into the electronic domain where it may be retransmitted on another lightpath toward its destination. Since the conversion of the packet from the optical to the electronic domain introduces delays and uses limited physical resources, one important objective is to find virtual topologies which minimize either the maximum or average number of lightpaths used from the source to all destination nodes. Although this problem is NP-complete in general, we show that minimizing the maximum or average number of lightpaths in path and ring topologies can be solved optimally by efficient algorithms.

This paper addresses the problem of constructing optimal virtual topologies for multicast communication in optical networks employing wavelength-division multiplexing (WDM). For concreteness, we use the average hop distance as the metric of optimality. WDM networks supporting multicast communication typically employ multicast-capable switches which permit a path entering a switch on an incoming wavelength to be replicated or "split" optically to one or more output links. This splitting incurs a power loss which is frequently neglected in existing heuristics and algorithms. In this paper we show that the problem of finding optimal virtual topologies with splitting loss constraints can be solved in polynomial time in directed paths and rings, although the problem is NP-complete for general topologies.