Jeremy J. Blum

Challenges of intervehicle ad hoc networks

Intervehicle communication (IVC) networks, a subclass of mobile ad hoc networks (MANETs), have no fixed infrastructure and instead rely on the nodes themselves to provide network functionality. However, due to mobility constraints, driver behavior, and high mobility, IVC networks exhibit characteristics that are dramatically different from many generic MANETs. This paper elicits these differences through simulations and mathematical models and then explores the impact of the differences on the IVC communication architecture, including important security implications.

Connected Dominating Set in Sensor Networks and MANETs

3 Centralized CDS Construction 335 3.1 Guha and Khuller’s Algorithm . . . . . . . . . . . . . . . . . . . . . 336 3.2 Ruan’s Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 3.3 Cheng’s Greedy Algorithm . . . . . . . . . . . . . . . . . . . . . . . . 340 3.4 Min’s Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 3.5 Butenko’s Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . 341

Mobility management in IVC networks

Inter-vehicle communication, a central component of future in-vehicle Intelligent Transportation Systems (ITS), will require the development of distributed coordination functions that operate without a fixed communications infrastructure. These functions will be critical for coordination of access to the media, message routing, and security. The stable clustering of nearby nodes is the key for the creation of a scalable network architecture. However, existing clustering algorithms for generic networks do not perform well in a vehicular, environment due to the high speeds and the constraints on vehicle mobility. This paper presents a clustering algorithm that greatly improves cluster stability.

Trust beyond security: an expanded trust model

Developing an improved trust model and related metrics for distributed computer-based systems that will be useful immediately and resilient to changing technology.

Enhancing intelligent agent collaboration for flow optimization of railroad traffic

Intelligent agents have successfully solved the train pathing problem on a small portion of railroad network [Tsen, 1995, Ph.D. Thesis, Carnegie Mellon University, USA]. As the railroad network grows, it is imperative that the agents collaborate to operate as efficiently as possible. In this paper, the authors demonstrate a collaboration protocol based on a conditional measure of agent effectiveness. Because agent effectiveness is not directly measurable, a suitable metric for agent effectiveness is introduced. Where typically agents run with uniform frequency, the collaboration protocol schedules the agents with a frequency proportional to their expected effectiveness. This protocol introduced a 10-fold improvement in the agent efficiency when tested with a simulation program on a portion of the Burlington Northern railroad.

Performance characteristics of inter-vehicle ad hoc networks

Inter-vehicle communication (IVC) networks are a sub-class of mobile ad hoc networks (MANETs). They have no fixed infrastructure and instead rely on the mobile nodes themselves to provide network functionality. However, due to mobility constraints, driver behavior, and high mobility, IVC networks exhibit characteristics that are dramatically different than those of many generic MANETs studied so far. This paper elicits these differences through simulations and mathematical models, and then investigates the impact of the differences on the IVC communication architecture, including important security implications.

Intelligent Agent Optimization of Urban Bus Transit System Design

The transit route network design (TRND) problem seeks a set of bus routes and schedules that is optimal in the sense that it maximizes the utility of an urban bus system for passengers while minimizing operator cost. Because of the computational intractability of the problem, finding an optimal solution for most systems is not possible. Instead, a wide variety of heuristic and meta-heuristic approaches have been applied to the problem to attempt to find near-optimal solutions. This paper presents an optimization system that synthesizes aspects of previous approaches into a scalable, flexible, intelligent agent architecture. This architecture has successfully been applied to other transportation and logistics problems in both research studies and commercial applications. This study shows that this intelligent agent system outperforms previous solutions for both a benchmark Swiss bus network system and the very large bus system in Delhi, India. Moreover, the system produces in a single run a set of Pareto equivalent solutions that allow a transit operator to evaluate the trade-offs between operator costs and passenger costs.

Avoiding Timeslot Boundary Synchronization for Multihop Message Broadcast in Vehicular Networks

The Timeslot Boundary Synchronization Problem occurs when timeslot boundaries become aligned leading to an increase in the probability of message collisions. This alignment, which can occur in Vehicular Ad Hoc Networks using the 802.11p protocols, adversely affects the performance of multi-hop message broadcasts. This paper describes the causes of this phenomenon and describes link and network layer design guidelines to address the problem. An integrated simulation system, which combines widely used wireless network and microscopic vehicle simulators, was used to simulate multi-hop emergency message broadcast in dense traffic situations. The simulation results show that addressing the Timeslot Boundary Synchronization Problem can reduce the total latency of multi-hop messages by 20.3% to 26.6%.

Denial of Service Attacks on Inter-Vehicle Communication Networks

Future safety systems will rely on the transmission of vehicle positions and kinematics through direct vehicle-to-vehicle wireless communication. The wireless access in vehicular environments (WAVE) standards, however, are vulnerable to denial of service (DoS) attacks which could significantly reduce the message delivery rate for these heartbeat messages. The WAVE standards were implemented in a simulation system in order to evaluate three different types of DoS attacks on these messages in a highway environment. These simulations show that the characteristics of the vehicular environments and heart-beat messages amplify the effect of these attacks, reducing the performance in the network in areas far from the attacking node. The amplification was due to the aggregate strength of the attackers and legitimate nodes signals. These combined signals reduced both the ability of nodes to receive messages clearly and the ability of nodes to detect that media is idle.

Efficient Certificate Distribution for Vehicle Heartbeat Messages

Vehicle heartbeat messages will enable a wide range of safety and efficiency applications. These messages, containing the position, kinematics, and state of a vehicle, will be sent over a wireless network to nearby vehicles at a high frequency. These messages will include a digital signature and a public key certificate to allow message recipients to validate the contents of a message. To minimize on the overhead, standards governing this network allow for the transmission of short certificate IDs instead of the full certificate. This paper proposes two distributed Certificate ID Scheduling algorithms, one in which a certificate is sent every nth message and another in which vehicles send full certificates only when a new neighbor is detected. Privacy considerations for certificate ID scheduling are analyzed, and the effectiveness of the protocols is evaluated through simulation of these heart-beat messages in a highway environment. These simulations show the first algorithm is most appropriate for high density, two-way traffic while the second algorithm can produce bandwidth savings that are close to the maximum for one-way or low density traffic.