Emerging applications rely on wireless broadcast to disseminate time-critical information. For example, vehicular networks may exchange vehicle position and velocity information to enable safety applications. The number of nodes in one-hop communication range in such networks can be very large, leading to congestion and undesirable levels of packet collisions. Earlier work has examined such broadcasting protocols primarily from a MAC perspective and focused on selective aspects such as packet error rate. In this work, we propose a more comprehensive metric, the average system information age, which captures the requirement of such applications to maintain current state information from all other nearby nodes. We show that information age is minimized at an optimal operating point that lies between the extremes of maximum throughput and minimum delay. Further, while age can be minimized by saturating the MAC and setting the CW size to its throughput-optimal value, the same cannot be achieved without changes in existing hardware. Also, via simulations we show that simple contention window size adaptations like increasing or decreasing the window size are unsuitable for reducing age. This motivates our design of an application-layer broadcast rate adaptation algorithm. It uses local decisions at nodes in the network to adapt their messaging rate to keep the system age to a minimum. Our simulations and experiments with 300 ORBIT nodes show that the algorithm effectively adapts the messaging rates and minimizes the system age.

/pdf/minimizing-age-of-information-in-vehicular-networks-2jlm45t2fh.pdf

Minimizing age of information in vehicular networks

VANET security surveys

Safety-critical applications in cooperative vehicular networks require authentication of nodes and messages. Yet, privacy of individual vehicles and drivers must be maintained. Pseudonymity can satisfy both security and privacy requirements. Thus, a large body of work emerged in recent years, proposing pseudonym solutions tailored to vehicular networks. In this survey, we detail the challenges and requirements for such pseudonym mechanisms, propose an abstract pseudonym lifecycle, and give an extensive overview and categorization of the state of the art in this research area. Specifically, this survey covers pseudonym schemes based on public key and identity-based cryptography, group signatures and symmetric authentication. We compare the different approaches, give an overview of the current state of standardization, and identify open research challenges.

Pseudonym Schemes in Vehicular Networks: A Survey

http://bbcr.uwaterloo.ca/~wzhuang/papers/MSSP_vanet_survey_2010.pdf

Infotainment and road safety service support in vehicular networking: From a communication perspective

Vehicle Safety Communications (VSC) is advancing rapidly towards product development and field testing. While a number of possible solutions have been proposed, the question remains open as how such a system will address the issue of scalability in its actual deployment. This paper presents a design methodology for congestion control in VSC as well as the description and evaluation of a resulting rate adaption oriented protocol named PULSAR. We start with a list of design principles reflecting the state of the art that define why and how vehicles should behave while responding to channel congestion in order to ensure fairness and support the needs of safety applications. From these principles, we derive protocol building blocks required to fulfill the defined objectives. Then, the actual protocol is described and assessed in detail, including a discussion on the intricate features of channel load assessment, rate adaptation and information sharing. A comparison with other state-of-the-art protocols shows that “details matter” with respect to the temporal and spatial dimensions of the protocol outcome.

/pdf/design-methodology-and-evaluation-of-rate-adaptation-based-1djeeaeirr.pdf

Design methodology and evaluation of rate adaptation based congestion control for Vehicle Safety Communications

In the future intervehicle communication will make driving safer, easier, and more comfortable. As a cornerstone of the system, vehicles need to be aware of other vehicles in the vicinity. This cooperative awareness is achieved by beaconing, the exchange of periodic single-hop broadcast messages that include data on the status of a vehicle. While the concept of beaconing has been developed in the first phase of research on VANETs, recent studies have revealed limitations with respect to network performance. Obviously, the frequency of beacon messages directly translates into accuracy of cooperative awareness and thus traffic safety. There is an indisputable trade-off between required bandwidth and achieved accuracy. In this work we analyze this trade-off from different perspectives considering the consequences for safety applications. As a solution to the problem of overloading the channel, we propose to control the offered load by adjusting the beacon frequency dynamically to the current traffic situation while maintaining appropriate accuracy. To find an optimal adaptation, we elaborate on several options that arise when determining the beacon frequency. As a result, we propose situation-adaptive beaconing. It depends on the vehicle's own movement and the movement of surrounding vehicles, macroscopic aspects like the current vehicle density, or microscopic aspects.

/pdf/exploration-of-adaptive-beaconing-for-efficient-intervehicle-41dg3hlxc9.pdf

Exploration of adaptive beaconing for efficient intervehicle safety communication

Communication using VANETs is commonly seen as the next milestone for improving traffic safety. Vehicles will be enabled to exchange any kind of information that helps to detect and mitigate dangerous situations. Security research in the past years has shown that VANETs are endangered by a plethora of severe security risk. Subject of this work is the modeling of attackers that target active safety applications in VANETs. Through a risk analysis, this work identifies assets, threats and potential attacks in inter-vehicle communication. The risk analysis shows that the most serious threat arises from a quasi-stationary (road-side) attacker that distributed forged warning messages. This attacker is discussed more deeply. We show the degrees of freedom that are available for position forging and find thereby two attacks that demand attention: single position forging having low effort compared to sophisticated movement path forging having a potentially high influence on road traffic safety.

Modeling Roadside Attacker Behavior in VANETs

Die Erfindung betrifft ein Verfahren zur Portierung von Alt-Steuerungssoftware (100), die fur ein Steuergerat (102) mit einem Einzel-Rechenkern (C0) entwickelt ist, auf ein Fahrzeugsteuergerat (103) mit mindestens zwei Rechenkernen (C1, C2, C3). In der Alt-Steuerungssoftware (100) sind Tasks (T-1, T-8, T-Cr) mit jeweils einem oder mehreren Ablaufteile (R_i) sowie eine Ausfuhrungs-Rangfolge (106) fur die Tasks enthalten. Es werden Vorrang-Beschrankungen (PC1, PC2, PC3) fur schreibende und lesende Zugriffe auf gemeinsame persistente Speichervariablen (Va, Vb) ermittelt und schwache Vorrang-Beschrankungen (PC2, PCx, PCy) nach vorbestimmten Klassifizierungsregeln (109) identifiziert. Ein Ausfuhrungsplans (105) fur die Ausfuhrung der Alt-Steuerungssoftware auf den zwei oder mehr Rechenkernen (C1, C2, C3) wird erzeugt, und zwar unter Parallelisierung von Ablaufteilen (R_11, R_81) mit schwachen Vorrang-Beschrankungen (PC2). Fur jede schwache Vorrang-Beschrankung (PC2) wird die zugehorige persistente Speichervariable (Va) in einer getrennt verwalteten Datenbasis (108) gespeichert, die einen wartezeitfreien lesenden und schreibenden Zugriff zulasst.

G. Schafer

Papers

Exploration of adaptive beaconing for efficient intervehicle safety communication

Modeling Roadside Attacker Behavior in VANETs

Parallelisierte Ausführung von Single-Core Steuerungssoftware auf Multi-Core Fahrzeugsteuergeräten