Abstract

With the advent of intelligent transportation systems and their associated more stringent requirements in terms of latency and packet delivery ratio, existing radio access technologies have exhibited a limited performance in specific scenarios that makes their sole operation in isolation unreliable for safety-related applications. In this context, hybrid V2X systems represent the state-of-the-art approach to address such challenge. Under this paradigm, the efficient operation of the system relies on a media selection algorithm, which uses different network parameters for predicting the technology that is foreseen to perform the best in a given scenario. While the network load is here regarded to affect the latency of the communication, no quantitative study has been found in the literature which supports this claim. Furthermore, the inaccessibility to this metric for commercially available off-the-shelf user equipments prevents a straightforward analysis of such parameter and its effects on C-V2X communications. In order to fill that gap, a framework has been designed and implemented over the course of this thesis that non-intrusively gathers information from live LTE networks when traversing them using an ITS-enabled vehicle. Such information has been then post-processed and used to perform a mapping of the deployed frequency bands in both rural and urban environments, as well as for evaluating principally the relationship between the latency experienced in on-road LTE communications with the instantaneous uplink load estimated for the serving eNodeBs traversed in an urban environment, without any assistance of the network. Thus, the overall uplink load has been estimated and in-depth analysis on the load per eNodeB has been carried out; during the tests, however, the uplink load has been estimated to be below 30% for the scenario under analysis and no straightforward correlation with the latency experienced when transmitting messages with different sizes has been identified, which suggests that further measurements need to be taken. On the other side, it was found that the radio resource allocation scheme used for uplink grant assignments by the eNodeBs under analysis is exploitable for reducing the cell load estimation time, which will support the migration of the set-up towards a real-time realization. The developed system therefore constitutes the groundwork for later analysis that will allow a more straightforward characterization of this relationship in different scenarios, which will ultimately serve to improve the media selection algorithm in hybrid V2X networks.

Abstract

Vehicle-to-Vehicle communication has recently passed from a research topic to the subject of Field Operational Testing (FOT) and pilot deployment. Current state-of-the art Car-to-Car and Car-to-Infrastructure (C2X) functions will however only inform the driver, not interfere in actual vehicle operation. A logical next step after initial deployment will be sensor fusion to enhance actively intervening Advanced Driver Assistance Systems (ADAS) with information received over C2X. As the penetration rate of equipped vehicles increases over time, higher-level CoDAS functions become feasible. In this paper we present a concept for a cooperative active blind spot assistant (CABSA) as an exemplary function of these novel Cooperative Driver Assistance Systems. As the CABSA function improves an existing ADAS function, no negative effects are observed in low-penetration scenarios. The function was implemented with messages adhering European Telecommunications Standards Institute (ETSI) standards. Simulations and real-life tests show that the increase in operation range significantly expands the vehicle speed envelope upon which the system can prevent accidents compared to conventional blind-spot assistance.

Abstract

Vehicular positioning technologies enable a broad range of applications and services such as navigation systems, driver assistance systems and self-driving vehicles. However, Global Navigation Satellite Systems (GNSS) do not work in enclosed areas such as parking garages. For these scenarios, a wide range of indoor positioning technologies are available inside the vehicle (internal) and based on infrastructure (external).

Abstract

The ongoing standardization of vehicle-to-x (V2X) communication via ITS-G5 as well as the high market penetration of cellular communication in vehicles provides potentials to increase safety, efficiency and comfort of road transport. First advanced driver assistance systems (ADAS) that utilize information provided via V2X are already available in production vehicles. In the first instance these systems inform or warn the driver but do not intervene in the vehicle control. On the other side, concepts for connected highly automated functions have been developed in research projects, which however demand high integrity of the information used as well as valid test and sign-off methods. As vehicle functions are increasingly connected with infrastructure elements, these interconnections need to be implemented in the development tool chain. For this reason a holistic development tool chain is being developed at RWTH Aachen University bringing together simulation, test track and field operational tests while taking communication and infrastructure components involved into account."br" At Aldenhoven Testing Center the CERM test environment that has been built up by a consortium of RWTH Aachen University institutes already provides the necessary infrastructure for testing and assessing automated and connected driving functions. The test set-up includes an urban intersection with dummy buildings, connected traffic lights, a reference sensor system and a communication environment comprising ITS-G5 and LTE communication. All components are interconnected by means of a network infrastructure and a software framework based on robot operating system (ROS) that allows to flexibly integrating new functions that use existing sensors and actuators. This integrated test environment extends the physical elements (roads, buildings etc.) by an informational layer."br" The paper gives an overview of the components of the development tool chain and provides detailed information about ongoing work and future research activities related to the controlled field test environment CERM and the test field Düsseldorf, which is co-funded by the German Federal Ministry of Transport and Digital Infrastructure in the research project KoMoD. This includes the requirements to the test environment with regards to design of track elements as well as to IT infrastructure. Also, use cases and connected and automated driving functions that interact with this test environment are presented and discussed. Finally, the paper closes with an outlook on future activities and research needs.

Abstract

High-precision and lane selective position estimation is of fundamental importance for prospective advanced driver assistance systems (ADAS) and automated driving functions, as well as for traffic information and management processes in intelligent transportation systems (ITS). User and vehicle positioning is usually based on Global Navigation Satellite System (GNSS), which, as stand-alone positioning, does not meet the necessary requirements in terms of accuracy. Furthermore, the rise of connected driving offers various possibilities to enhance GNSS positioning by applying cooperative positioning (CP) methods. Utilizing only low-cost sensors, especially in urban environments, GNSS CP faces several demanding challenges. Therefore, this contribution presents an empirical study on how Vehicle-to-Everything (V2X) technologies can aid GNSS position estimation in urban environments, with the focus being solely on positioning performance instead of multi-sensor data fusion. The performance of CP utilizing common positioning approaches as well as CP integration in state-of-the-art Vehicular Ad-hoc Networks (VANET) is displayed and discussed. Additionally, a measurement campaign, providing a representational foundation for validating multiple CP methods using only consumer level and low-cost GNSS receivers, as well as commercially available IEEE 802.11p V2X communication modules in a typical urban environment is presented. Evaluating the algorithm&rsquo s performance, it is shown that CP approaches are less accurate compared to single positioning in the given environment. In order to investigate error influences, a skyview modelling seeking to identify non-line-of-sight (NLoS) effects using a 3D building model was performed. We found the position estimates to be less accurate in areas which are affected by NLoS effects such as multipath reception. Due to covariance propagation, the accuracy of CP approaches is decreased, calling for strategies for multipath detection and mitigation. In summary, this contribution will provide insights on integration, implementation strategies and accuracy performances, as well as drawbacks for local area, low-cost GNSS CP in urban environments. Document type: Article

Abstract

Wireless vehicular ad-hoc networks comprised solely of city taxis are investigated for their ability to deliver data across an urban environment. Openly available taxi trace datasets for Rome (Italy) and San Francisco (USA) are combined with respective building footprint and road network topology data from OpenStreetMap, to generate a realistic systems level model of a taxi V2V network. Analysis of LOS and NOLOS constraints on wireless transmission range suggests a minimum threshold of 50m is applicable to ensure LOS in over 90% of cases. Variations in taxi location sampling frequency and filtering techniques for the taxi trace datasets are also investigated. Overall vehicular network performance is computed for an all-to-one transmission scenario for both cities with varying taxi fleet size. Results suggest a non-linear relationship between increases in taxi fleet sizes and the reduction of end-to-end delay; doubling taxi fleet size (using a randomised data folding technique) reduces end-to-end delay by a factor of 0.6–0.7. However, doubling the fleet does not increase the fraction of delivered source messages, which saturates at 0.67–0.71 in most simulations. Finally it appears that taxi networks for delivering messages across urban environments are limited more by their routing than by the number of possible V2V exchanges. In a simulated one-to-all continuous V2V broadcast scenario, over 90% of the taxis within the fleet receive the source message within one hour of the original taxi passing the source node.

Abstract

This article discusses the results of supporting transition towards fully automated driving with remote operator support via the novel V2X channels. Automated passenger cars are equipped with multiple sensors (radars, cameras, LiDARs, inertia, GNSS, etc.), the operation of which is limited by weather, detection range, processing power and resolution. The study explores the use of a dedicated network for supporting automated driving needs. The MEC server latencies and bandwidths are compared between the Tampere, Finland test network and studies conducted in China to support remote passenger car operation. In China the main aim is to evaluate the network latencies in different communication planes, whereas the European focus is more on associated driving applications, thus making the two studies mutually complementary.5G revolutionizes connected driving, providing new avenues due to having lower and less latency variation and higher bandwidths. However, due to higher operating frequencies, network coverage is a challenge and one base station is limited to a few hundred meters and thus they deployed mainly to cities with a high population density. Therefore, the transport solutions are lacking so-called C-V2X (one form of 5G RAT) to enable data exchanges between vehicles (V2V) and also between vehicles and the digital infrastructure (V2I). The results of this study indicate that new edge-computing services do not cause a significant increase in latencies $(\\lt 100$ ms), but that latency variation (11 - 192 ms) remains a problem in the first new network configurations.

Abstract

Traffic control management at intersections, a challenging and complex field of study, aims to strike a balance between safety and efficient traffic control. Nowadays, traffic control at intersections is typically done by traffic light systems which are not optimal and exhibit several drawbacks, such as poor efficiency and real-time adaptability. With the advent of Intelligent Transportation Systems (ITS), vehicles are being equipped with state-of-the-art technology, enabling cooperative decision-making which will certainly overwhelm the available traffic control systems. This solution strongly penalizes users without such capabilities, namely pedestrians, cyclists, and other legacy vehicles. Therefore, in this work, a prototype based on an alternative technology to the standard vehicular communications, Bluetooth Low Energy (BLE), is presented. The proposed framework aims to integrate legacy and modern vehicular communication systems into a cohesive management system. In this framework, the movements of users at intersections are managed by a centralized controller which, through the use of networked retransmitters deployed at intersections, broadcasts alerts and virtual light signalization orders. Users receive the aforementioned information on their own smart devices, discarding the need for dedicated light signalization infrastructures. Field tests, carried out with a real-world implementation, validate the correct operation of the proposed framework. Document type: Article