Abstract

Wireless vehicular networks are to be deployed in both Europe and the USA within upcoming years. Such networks introduce a new promising source of information about vehicular environments to be used by cooperative advanced driver assistance systems (ADAS). However, development and evaluation of such cooperative ADAS is still challenging. Hence, we introduce a novel methodology for their development and evaluation processes. It is applied to evaluate the fulfillment of requirements on position accuracy information within exchanged messages. Such requirements are only roughly defined and not sufficiently evaluated in field tests. This holds especially for Global Navigation Satellite Systems (GNSS) optimized for maximum integrity of obtained positions. Such configuration is required to increase robustness and reliability of safety critical ADAS. We find that pure GNSS-based positioning cannot fulfill position accuracy requirements of studied ADAS in most test cases.

Abstract

Nowadays, driver assistance systems involve an ever increasing degree of automatization. Costly effort is put into testing the individual components to ensure proper functioning by the vehicle manufacturers. However, problems can also arise on a macroscopic scale, as vehicles and infrastructure are recently equipped with short range radio communication (“Car2X”). These problems caused by interaction are of even greater concern than “normal” bugs, as the final product might already have been deployed when the issues first become apparent. Multi-Agent System (MAS) research refers to such issues as “emergent misbehavior”. The said field also brought up an approach to automatically discover the worst consequences of the malfunctions. Hence, a given system under test can already be revised during development, saving a tremendous amount of resources. The approach from MAS is adapted to the domain of testing driver assistance systems in traffic simulations. A green-light optimal-speed advisory (GLOSA) algorithm is used as an example in which conceptual problems are discovered by the testing system after simpler issues are eliminated.

Abstract

Vehicular ad hoc networks (VANETs), often called Car2X communication systems, are about to enter the mass market in upcoming years. They are intended to increase traffic safety by enabling new safety critical driver assistance systems. This also means that strong security mechanisms are required to safeguard communication within VANETs. However, standardized security mechanisms lead to significant overhead in terms of data rate requirement and delay. Prior work has focused on reducing the overhead by advanced strategies for pseudonym and authorization authority certificate exchange. However, we find that this is not enough to enable reliable message exchange in VANETs. Various other sources of overhead caused by security mechanisms in VANETs are identified in the provided analysis. Thereby, we find cross layer and cross message dependencies. In combination with the non-fragmentation property of VANET messages, such dependencies are discovered to lead to massive dropping of packets due to maximum size violations at low protocol layers. Thus, we develop a method for cross layer on demand content assembling for VANET messages, which can avoid the size limit violations without preventing individual layers from disseminating their variable length data sets.

Abstract

Wireless intelligent transport systems based on Car-to-X communication technology are about to enter the mass market in upcoming years. Thereby, efficient and reliable security systems are a core point of concern in system design. Currently regarded digital signature schemes using pseudonym certificates can introduce significant overhead into the highly bandwidth restricted system. Thus, mechanisms to optimize the efficiency of the security mechanisms in regard to authentication delay and channel load are required. Prior work has focused on scenarios with high node mobility, e.g., Freeways. However, bandwidth conserving mechanisms are also required for urban low and medium mobility scenarios to enable foreseen extension of the wireless network for the many other volatile road users like pedestrians. Hence, an approach for efficient pseudonym certificate distribution in urban scenarios is provided in this work. The given simulation based environment shows that it can enhance cooperative awareness while limiting used bandwidth. Thus, it can be regarded as well suitable for future urban intelligent transport systems.

Abstract

Wireless vehicular networks are in the wake of mass deployment both in Europe and the USA. These networks introduce a new promising source of information about vehicular environments usable by cooperative advanced driver assistance systems (ADAS). However, development and evaluation of such ADAS is still challenging. Thus, we propose a methodology for their development and evaluation process. It is applied to evaluate the fulfillment of requirements on position accuracy information within the communicated data sets. Accuracy requirements are only roughly defined and not sufficiently evaluated in real world environments. This holds especially for GNSS (Global Navigation Satellite Systems) optimized for maximum integrity of obtained positions, which is required for safety critical ADAS to increase robustness and reliability. Our main goal is to determine whether position accuracy provided by GNSS is sufficient for cooperative ADAS. Thereby, we find that pure GNSS input cannot fulfill position accuracy requirements in most test cases.

Abstract

Car-to-X communication systems, often called vehicular ad-hoc networks (VANETs), are in the process of entering the mass market in upcoming years. Thereby, security is a core point of concern due to the intended use for safety critical driver assistance systems. However, currently suggested security mechanisms introduce significant overhead into Car-to-X systems in terms of channel load and delay. Especially, the usage of on the fly distributed pseudonym certificates leads to a trade off between channel load and authentication delay, which may lead to significant packet loss. Thus, this work studies a novel concept for pseudonym certificate distribution in VANETs using rate-adaptive certificate distribution based on monitoring a vehicle's environment. Thereby, the cyclic certificate emission frequency is adapted on the fly based on cooperative awareness metrics for discrete parts of the vehicle's surrounding. The obtained mechanism is evaluated in a highway as well as an urban simulation scenario to show its suitability for a broad range of traffic conditions. Thereby, we find that it is able to significantly outperform the currently standardized approach for pseudonym certificate distribution in VANETs based on ETSI ITS standards. Thus, it should be regarded for further development of future VANETs.