Rex Chen

Broadcasting safety information in vehicular networks: issues and approaches

A primary goal of intelligent transportation systems is to improve road safety. The ability of vehicles to communicate is a promising way to alleviate traffic accidents by reducing the response time associated with human reaction to nearby drivers. Vehicle mobility patterns caused by varying traffic dynamics and travel behavior lead to considerable complexity in the efficiency and reliability of vehicular communication networks. This causes two major routing issues: the broadcast storm problem and the network disconnection problem. In this article we review broadcast communication in vehicular communication networks and mechanisms to alleviate the broadcast storm problem. Moreover, we introduce vehicular safety applications, discuss network design considerations, and characterize broadcast protocols in vehicular networks.

ODAR: On-Demand Anonymous Routing in Ad Hoc Networks

Routing in wireless ad hoc networks are vulnerable to traffic analysis, spoofing and denial of service attacks due to open wireless medium communications. Anonymity mechanisms in ad hoc networks are critical security measures used to mitigate these problems by concealing identification information, such as those of nodes, links, traffic flows, paths and network topology information from harmful attackers. We propose ODAR, an On-Demand Anonymous Routing protocol for wireless ad hoc networks to enable complete anonymity of nodes, links and source-routing paths/trees using Bloom filters. We simulate ODAR using J-Sim, and compare its performance with AODV in certain ad hoc network scenarios

Multi-Hop Broadcasting in Vehicular Ad Hoc Networks with Shockwave Traffic

A primary goal of intelligent transportation systems (ITS) is to improve road safety. The ability for vehicles to communicate is a promising way to alleviate traffic accidents by reducing the response time associated with human reaction to nearby drivers. In addition the limitations of standard driving can be overcome by providing drivers with instantaneous information about complications up ahead. Shockwaves, induced by vehicle speed differentials, are a typical mobility pattern that occurs with the formation and propagation of vehicle queues. These induce sudden braking and increase the occurrence of traffic incidents. In this paper, we investigate safety applications in highways with shockwave mobility and different lane configurations in vehicular ad hoc networks (VANET). We evaluate the performance of multi-hop broadcast communication using the ns-2 simulator with vehicles following a shockwave mobility pattern in fully-connected traffic streams. We propose mechanism to improve broadcast reliability using dynamic transmission range that leverages our understanding of fundamental traffic flow relationships.

Dynamic transmission range in inter-vehicle communication with stop-and-go traffic

Inter-vehicle communication is a promising way to share and disseminate real-time and nearby safety information on the road. However, several pressing open questions require solutions in order to achieve high reliability and efficiency with these systems. Further, previous studies show that mobility model can significantly influence the communication performance in vehicular networks. In this paper, we analyze communication in stop-and-go waves and propose a method to optimize an important network parameter, the transmission range, based on traffic pattern measures. Our findings suggest a transmission range adjustment scheme that achieves high reliability by considering network coverage and packet reception rates.

Google: The World's First Information Utility?

In only ten years, Google has achieved remarkable success from online search-based advertising. Its search engine is dominant, and its IT infrastructure is the most powerful computing system in the world running on over one million computers and serving more than one billion users globally. Google makes money by using its search engine to deliver online advertising alongside responses to user searches for information, goods, maps, directions, and a host of other services. Its capabilities make it likely to become the world’s first information utility – a concept similar to electric utilities that provide services to many corporations and individuals alike. Constant innovation is the key to Google’s success and offers lessons for other companies: hire talented people, have them work in small teams, and give them freedom to excel, but use a rigorous data-based approach to evaluating results and making course adjustments.

Google: Das weltweit erste „Information Utility“?

ZusammenfassungIn nur zehn Jahren hat Google einen bemerkenswerten Erfolg durch Werbung im Rahmen der Onlinesuche erlangt. Googles Suchmaschine ist dominant und seine IT-Infrastruktur ist das mächtigste Rechnersystem der Welt. Es wird auf mehr als einer Million Computern betrieben und bedient weltweit mehr als einer Milliarde Nutzern. Google verdient, indem seine Suchmaschine Onlinewerbung neben Antworten auf Nutzeranfragen nach Informationen, Waren, Karten, Wegbeschreibungen und einer ganzen Reihe von anderen Diensten platziert. Googles Potenzial führt wahrscheinlich dazu, dass das Unternehmen zum weltweit ersten „Information Utility“ wird. Da kein deutschsprachiges Äquivalent existiert, wird im Folgenden der englischsprachige Begriff verwendet. Er ist in etwa gleichzusetzen mit „Informationsversorger“ – ein Konzept ähnlich einem Stromversorger (engl. electric utility), welcher Dienste für viele Unternehmen und Privatpersonen gleichermaßen anbietet. Ständige Innovation ist der Schlüssel zu Googles Erfolg und stellt ein Vorbild für andere Unternehmen dar: Stelle talentierte Menschen ein, lasse sie in kleinen Teams arbeiten und gib ihnen die Freiheit, andere zu übertreffen, aber nutze ein strenges datenbasiertes Konzept für die Bewertung der Ergebnisse und für Strategieanpassungen.AbstractIn only ten years, Google has achieved remarkable success from online search-based advertising. Its search engine is dominant, and its IT infrastructure is the most powerful computing system in the world running on over one million computers and serving more than one billion users globally. Google makes money by using its search engine to deliver online advertising alongside responses to user searches for information, goods, maps, directions, and a host of other services. Its capabilities make it likely to become the world’s first information utility – a concept similar to electric utilities that provide services to many corporations and individuals alike. Constant innovation is the key to Google’s success and offers lessons for other companies: hire talented people, have them work in small teams, and give them freedom to excel, but use a rigorous data-based approach to evaluating results and making course adjustments.

Broadcasting in vehicular networks

Broadcasting in vehicular networks is more prevalent than other transmission methods because of need to facilitate rapid, brief communications with nearby vehicles. However, the success of these message dissemination schemes relies on our ability to develop and implement routing protocols to specifically address the low latency requirements in a highly mobile environment. In this chapter we review broadcasting protocols that have been developed specifically for these networks. We also examine the primary factors affecting reliability of these protocols, namely transmission range, contention window size, and traffic configurations (shockwave disturbances and stop-and-go traffic).

Vehicular ad hoc networks

Abstract Researchers and policy makers have long waited to see fully connected vehicular networks that can help prevent accidents, facilitate eco-friendly driving, and provide better and more accurate real-time traffic information. Today, vehicular ad hoc networks (VANETs) are a promising application of technologies that could help to achieve many of these goals. Using advances in wireless communications, computing, and vehicular technologies, VANETs rely on real-time communication among vehicles, pedestrians, and roadside sensors located along transportation systems. While many of the technical challenges of these complex systems have been addressed, concerns about security, liability, and privacy may impede rapid progress toward large-scale implementation and deployment. This chapter examines the promise and the perils of these systems.