::: Routing in Vehicular Ad Hoc Networks (VANET)
Analyses of traditional routing protocols for mobile ad hoc networks demonstrate that their performance is poor in VANETs, especially in city environments. We propose RBVT, a class of city-based VANET routing protocols which leverage real-time vehicular traffic information to create road-based paths consisting of successions of road intersections that have, with high probability, network connectivity among them. Geographical forwarding is used to transfer packets between intersections on the path, reducing the path's sensitivity to node mobility. For dense networks with high contention specific to cities, RBVT optimizes the forwarding using a distributed receiver-based election of next hops based on a multi-criteria prioritization function taking into account the non-uniform radio propagation. We designed and implemented two RBVT protocols, one reactive and one proactive. The former performs best for end-to-end delivery rates, while the latter performs best for end-to-end latency. On-going work focuses on adaptive queuing mechanisms for VANETs.

::: Vehicular Traffic Generator
Testing vehicular protocols at scale requires suitable mobility models and tools to generate mobility traces to be used in simulators. We developed a microscopic vehicular traffic generator based on the car-following and lane-changing models proposed by Gipps, which belong to the class of collision avoidance vehicular mobility models. The main goal of these models is to enable a vehicle to move at the maximum safest speed that ensures that there will be no collision with the preceding vehicle. The Gipps car-following model provides the ability for smooth transitions between acceleration and deceleration. Since we target city scenarios, our generator supports traffic lights at road intersections as well as bidirectional and multi-lane traffic. We used this generator in conjunction with the ns-2 network simulator and digital road maps from the TIGER/Line database. The code for the generator along with basic documentation can be downloaded from here.

::: Programming Models and Middleware
VANETs can be leveraged to provide ubiquitous services capable of acquiring, processing, and sharing real-time information from the physical world. Programming such mobile sensing services is challenging due to frequent context changes, which often lead to situations where a service cannot produce semantically acceptable results on its current node. We proposed a novel service programming model based on the concept of context-aware migratory services. Unlike a regular service that executes always on the same node, a migratory service can migrate to different nodes in the network to accomplish its task. The migration is triggered by changes of the operating context and occurs transparently to the clients. We designed and implemented a middleware for developing migratory services. We also built TJam, a proof-of-concept migratory service that predicts traffic jams on the highways. The software distribution can be downloaded from here. This code uses the portable smart messages software, wich can be downloaded from here.

::: Trusted VANETs
To ensure fair and secure communication in VANETs, the applications running in these networks must be regulated by proper communication policies. However, enforcing policies in ad hoc networks is challenging because they lack the infrastructure and trusted entities encountered in traditional distributed systems. To solve this issue, we designed and implemented policy enforcing mechanisms based on a kernel-level trusted execution monitor built on top of the Trusted Platform Module. Under these mechanisms, two instances of an application running on different nodes may engage in communication only if these nodes enforce the same application policies. In this way, nodes can form trusted application-centric networks. Before allowing a node to join a trusted application-centric network, the trusted execution monitor verifies its trustworthiness of enforcing the application policy. The monitor also protects the policies and the software enforcing these policies from being tampered with. If any of them is compromised, it disconnects the node from the network and potential attacks are stopped at the originator.

::: VANET - Wireless Sensor Networks Symbiosis
Improving driving safety is a top objective for VANETs. However, the lack of sensing in the absence of cars ahead on the road and frequent network disconnections could lead to driving hazards: these networks cannot detect dangerous road conditions with good accuracy and cannot guarantee timely propagation of alert messages. To address these problems, this on-going research proposes to merge inexpensive wireless sensor networks (WSNs) with VANETs to create a VANET-WSN symbiotic architecture. In this architecture, sensor nodes are deployed along road sides to detect dangerous road conditions and facilitate timely information sharing among vehicles; in return, VANETs provide richer computation, communication, storage, and power resources to help WSNs overcome their resource constraints. On top of this symbiosis, we plan to build more effective on-road information systems for traffic safety.

Faculty:

• Cristian Borcea

Students:

• Josiane Nzouonta, Neeraj Rajgure

Collaborators:

• Liviu Iftode, Oriana Riva, Gang Xu, Tamer Nadeem, Grace Wang, Wensheng Zhang.

Visitors:

• Cristian Zamfir, Daniel Purdila.

» Exploring the Design and Implementation of Vehicular Networked Systems. NSF, 2005-2008. Collaborative research with Rutgers University.

» Real-time Information Systems for Driving Safety atop VANET-WSN symbiosis. NSF, 2008-2010. Collaborative research with Iowa State University.

» A Policy Enforcing Mechanism for Trusted Ad Hoc Networks
Gang Xu, Cristian Borcea, and Liviu Iftode
Under Submission.

» VANET Routing on City Roads using Real-Time Vehicular Traffic Information
Josiane Nzouonta, Neeraj Rajgure, Guiling Wang, and Cristian Borcea
IEEE Transactions on Vehicular Technology, To appear 2009.

» Context-Aware Fault Tolerance in Migratory Services
Oriana Riva, Josiane Nzouonta, and Cristian Borcea
Proceedings of the 5th International Conference on Mobile and Ubiquitous Systems: Computing, Networking and Services (MobiQuitous 2008), July 2008.

» Context-aware Migratory Services in Ad Hoc Networks
Oriana Riva, Tamer Nadeem, Cristian Borcea, and Liviu Iftode
IEEE Transactions on Mobile Computing, December 2007.

» Trusted Application-Centric Ad-Hoc Networks
Gang Xu, Cristian Borcea, and Liviu Iftode
Proceedings of the 4th IEEE International Conference on Mobile Ad-hoc and Sensor Systems (MASS 2007), October 2007.

» The Urbanet Revolution: Sensor Power to the People!
Oriana Riva and Cristian Borcea
IEEE Pervasive Computing, Special Issue on Building a Sensor-Rich World. Apr-Jun 2007.

» Satem: Trusted Service Code Execution across Transactions
Gang Xu, Cristian Borcea, and Liviu Iftode
Proceedings of the 25th IEEE Symposium on Reliable Distributed Systems (SRDS 2006) , October 2006.

» EZCab: A Cab Booking Application using Short-range Wireless Communication
Peng Zhou, Tamer Nadeem, Porlin Kang, Cristian Borcea, and Liviu Iftode
Proceedings of the 3rd IEEE International Conference on Pervasive Computing and Communications (PerCom 2005), March 2005.