Operating ITS-G5 DSRC over Unlicensed Bands: A City-Scale Performance Evaluation

Future Connected and Autonomous Vehicles (CAVs) will be equipped with a large set of sensors. The large amount of generated sensor data is expected to be exchanged with other CAVs and the road-side infrastructure. Both in Europe and the US, Dedicated Short Range Communications (DSRC) systems, based on the IEEE 802.11p Physical Layer, are key enabler for the communication among vehicles. Given the expected market penetration of connected vehicles, the licensed band of 75 MHz, dedicated to DSRC communications, is expected to become increasingly congested. In this paper, we investigate the performance of a vehicular communication system, operated over the unlicensed bands 2.4 GHz - 2.5 GHz and 5.725 GHz - 5.875 GHz. Our experimental evaluation was carried out in a testing track in the centre of Bristol, UK and our system is a full-stack ETSI ITS-G5 implementation. Our performance investigation compares key communication metrics (e.g., packet delivery rate, received signal strength indicator) measured by operating our system over the licensed DSRC and the considered unlicensed bands. In particular, when operated over the 2.4 GHz - 2.5 GHz band, our system achieves comparable performance to the case when the DSRC band is used. On the other hand, as soon as the system, is operated over the 5.725 GHz - 5.875 GHz band, the packet delivery rate is 30% smaller compared to the case when the DSRC band is employed. These findings prove that operating our system over unlicensed ISM bands is a viable option. During our experimental evaluation, we recorded all the generated network interactions and the complete data set has been publicly available.Comment: IEEE PIMRC 2019, to appea

A City-Scale ITS-G5 Network for Next-Generation Intelligent Transportation Systems: Design Insights and Challenges

As we move towards autonomous vehicles, a reliable Vehicle-to-Everything (V2X) communication framework becomes of paramount importance. In this paper we present the development and the performance evaluation of a real-world vehicular networking testbed. Our testbed, deployed in the heart of the City of Bristol, UK, is able to exchange sensor data in a V2X manner. We will describe the testbed architecture and its operational modes. Then, we will provide some insight pertaining the firmware operating on the network devices. The system performance has been evaluated under a series of large-scale field trials, which have proven how our solution represents a low-cost high-quality framework for V2X communications. Our system managed to achieve high packet delivery ratios under different scenarios (urban, rural, highway) and for different locations around the city. We have also identified the instability of the packet transmission rate while using single-core devices, and we present some future directions that will address that.Comment: Accepted for publication to AdHoc-Now 201

Multi-antenna 3D pattern design for millimeter-wave vehicular communications

The transformation of the automotive industry towards ubiquitous connection of vehicles with all kind of external agents (V2X) motivates the use of a wide range of frequencies for several applications. Millimeter-wave (mmWave) connectivity represents a paramount research field in which adequate geometries of antenna arrays must be provided to be integrated in modern vehicles, so 5G-V2X can be fully exploited in the Frequency Range 2 (FR2) band. This paper presents an approach to design mmWave vehicular multi-antenna systems with beamforming capabilities considering the practical limitations of their usage in real vehicular environments. The study considers both the influence of the vehicle itself at radiation pattern level and the impact of the urban traffic on physical layer parameters. Connectivity parameters such as Signal-to-Interference-plus-Noise Ratio (SINR) and outage probability are optimized based on the array topology. A shaped beam in the vertical plane based on three preset radiating elements is proven to be robust enough against self-scattering effects on the vehicle body. Regarding the horizontal geometry, four panels on the roof's edges provide good coverage and link quality. The number of horizontal antennas per panel tightly depends on the required values of the link quality metrics, potentially leading to a non-uniform geometry between sides and front or back panels.This work was partly funded by the Spanish Ministerio de Economía y Competitividad under the projects PID2019-107885GB- C31 and MDM2016-0600, the Catalan Research Group 2017 SGR 219, and “Industrial Doctorate” programme (2018-DI-084). The Spanish Ministry of Education contributes via a predoctoral grant to the first author (FPU17/05561).Peer ReviewedPostprint (published version

Automotive applications of high precision GNSS

This thesis aims to show that Global Navigation Satellite Systems (GNSS) positioning can play a significant role in the positioning systems of future automotive applications. This is through the adoption of state-of-the-art GNSS positioning technology and techniques, and the exploitation of the rapidly developing vehicle-to-vehicle concept. The merging together of these two developments creates greater performance than can be achieved separately. The original contribution of this thesis comes from this combination: Through the introduction of the Pseudo-VRS concept. Pseudo-VRS uses the princples of Network Real Time Kinematic (N-RTK) positioning to share GNSS information between vehicles, which enables absolute vehicle positioning. Pseudo-VRS is shown to improve the performance of high precision GNSS positioning for road vehicles, through the increased availability of GNSS correction messages and the rapid resolution of the N-RTK fixed solution. Positioning systems in the automotive sector are dominated by satellite-based solutions provided by GNSS. This has been the case since May 2001, when the United States Department of Defense switched off Selective Availability, enabling significantly improved positioning performance for civilian users. The average person most frequently encounters GNSS when using electronic personal navigation devices. The Sat Nav or GPS Navigator is ubiquitous in modern societies, where versions can be found on nomadic devices such as smartphones and dedicated personal navigation devices, or built in to the dashboards of vehicles. Such devices have been hugely successful due to their intrinsic ability to provide position information anywhere in the world with an accuracy of approximately 10 metres, which has proved ideal for general navigation applications. There are a few well known limitations of GNSS positioning, including anecdotal evidence of incorrect navigation advice for personal navigation devices, but these are minor compared to the overall positioning performance. Through steady development of GNSS positioning devices, including the integration of other low cost sensors (for instance, wheel speed or odometer sensors in vehicles), and the development of robust map matching algorithms, the performance of these devices for navigation applications is truly incredible. However, when tested for advanced automotive applications, the performance of GNSS positioning devices is found to be inadequate. In particular, in the most advanced fields of research such as autonomous vehicle technology, GNSS positioning devices are relegated to a secondary role, or often not used at all. They are replaced by terrestrial sensors that provide greater situational awareness, such as radar and lidar. This is due to the high performance demand of such applications, including high positioning accuracy (sub-decimetre), high availability and continuity of solutions (100%), and high integrity of the position information. Low-cost GNSS receivers generally do not meet such requirements. This could be considered an enormous oversight, as modern GNSS positioning technology and techniques have significantly improved satellite-based positioning performance. Other non-GNSS techniques also have their limitations that GNSS devices can minimise or eliminate. For instance, systems that rely on situational awareness require accurate digital maps of their surroundings as a reference. GNSS positioning can help to gather this data, provide an input, and act as a fail-safe in the event of digital map errors. It is apparent that in order to deliver advanced automotive applications - such as semi- or fully-autonomous vehicles - there must be an element of absolute positioning capability. Positioning systems will work alongside situational awareness systems to enable the autonomous vehicles to navigate through the real world. A strong candidate for the positioning system is GNSS positioning. This thesis builds on work already started by researchers at the University of Nottingham, to show that N-RTK positioning is one such technique. N-RTK can provide sub-decimetre accuracy absolute positioning solutions, with high availability, continuity, and integrity. A key component of N-RTK is the availability of real-time GNSS correction data. This is typically delivered to the GNSS receiver via mobile internet (for a roving receiver). This can be a significant limitation, as it relies on the performance of the mobile communications network, which can suffer from performance degradation during dynamic operation. Mobile communications systems are expected to improve significantly over the next few years, as consumers demand faster download speeds and wider availability. Mobile communications coverage already covers a high percentage of the population, but this does not translate into a high percentage of a country's geography. Pockets of poor coverage, often referred to as notspots, are widespread. Many of these notspots include the transportation infrastructure. The vehicle-to-vehicle concept has made significant forward steps in the last few years. Traditionally promoted as a key component of future automotive safety applications, it is now driven primarily by increased demand for in-vehicle infotainment. The concept, which shares similarities with the Internet of Things and Mobile Ad-hoc Networks, relies on communication between road vehicles and other road agents (such as pedestrians and road infrastructure). N-RTK positioning can take advantage of this communication link to minimise its own communications-related limitations. Sharing GNSS information between local GNSS receivers enables better performance of GNSS positioning, based on the principles of differential GNSS and N-RTK positioning techniques. This advanced concept is introduced and tested in this thesis. The Pseudo VRS concept follows the protocols and format of sharing GNSS data used in N-RTK positioning. The technique utilises the latest GNSS receiver design, including multiple frequency measurements and high quality antennas

Mobile 5G millimeter-wave multi-antenna systems

In reference to IEEE copyrighted material which is used with permission in this thesis, the IEEE does not endorse any of Universitat Politècnica de Catalunya's products or services. Internal or personal use of this material is permitted. If interested in reprinting/republishing IEEE copyrighted material for advertising or promotional purposes or for creating new collective works for resale or redistribution, please go to http://www.ieee.org/publications_standards/publications/rights/rights_link.html to learn how to obtain a License from RightsLink.Tesi en modalitat de compendi de publicacionsMassive antenna architectures and millimeter-wave bands appear on the horizon as the enabling technologies of future broadband wireless links, promising unprecedented spectral efficiency and data rates. In the recently launched fifth generation of mobile communications, millimetric bands are already introduced but their widespread deployment still presents several feasibility issues. In particular, high-mobility environments represent the most challenging scenario when dealing with directive patterns, which are essential for the adequate reception of signals at those bands. Vehicular communications are expected to exploit the full potential of future generations due to the massive number of connected users and stringent requirements in terms of reliability, latency, and throughput while moving at high speeds. This thesis proposes two solutions to completely take advantage of multi-antenna systems in those cases: beamwidth adaptation of cellular stations when tracking vehicular users based on positioning and Doppler information and a tailored radiation diagram from a panel-based system of antennas mounted on the vehicle. Apart from cellular base stations and vehicles, a third entity that cannot be forgotten in future mobile communications are pedestrians. Past generations were developed around the figure of human users and, now, they must still be able to seamlessly connect with any other user of the network and exploit the new capabilities promised by 5G. The use of millimeter-waves is already been considered by handset manufacturers but the impact of the user (and the interaction with the phone) is drastically changed. The last part of this thesis is devoted to the study of human user dynamics and how they influence the achievable coverage with different distributed antenna systems on the phone.Les arquitectures massives d'antenes i les bandes mil·limètriques apareixen a l'horitzó com les tecnologies que impulsaran els futurs enllaços sense fils amb gran ample de banda i prometen una eficiència espectral i velocitat de transmissió sense precedents. A la recent cinquena generació de comunicacions mòbils, les bandes mil·limètriques ja en són una part constitutiva però el seu desplegament encara presenta certes dificultats. En concret, els entorns d'alta mobilitat representen el major repte quan es fan servir diagrames de radiació directius, els quals són essencials per una correcta recepció del senyal en aquestes bandes. S'espera que les comunicacions vehiculars delimitin les capacitats de les xarxes en futures generacions degut al gran nombre d'usuaris simultanis i els requeriments estrictes en termes de fiabilitat, retard i flux de dades mentre es mouen a grans velocitats. Aquesta tesi proposa dues solucions per tal d'explotar al màxim els sistemes de múltiples antenes en tals casos: un ample de feix adaptatiu de les estacions bases quan estiguin fent el seguiment d'un vehicle usuari basat en informació de la posició i el Doppler i el disseny d'un diagrama de radiació adequat al costat del vehicle basat en una estructura de múltiples panells muntats a l'estructura del mateix. A més de les estacions base i els vehicles, un tercer element que no pot ser obviat en aquests escenaris són els vianants. Les generacions anteriors van ser desenvolupades al voltant de la figura d'usuaris humans i ara han de seguir tenint la capacitat de connexió ininterrumpuda amb la resta d'usuaris i explotar les capacitats de 5G. L'ús de frequències mil·limètriques també es té en compte en la fabricació de telèfons mòbils però l'impacte de l'usuari és completament diferent. La última part de la tesis tracta l'estudi de les dinàmiques de l'usuari humà i com influeixen en la cobertura amb diferent sistemes distribuïts d'antenes.Postprint (published version

Fifth-Generation Technologies for the Connected Car:Capable Systems for Vehicle-to-Anything Communications

Two strong technology trends, one in the mobile communications industry and the other in the automotive industry, are becoming interwoven and will jointly provide new capabilities and functionality for upcoming intelligent transport systems (ITSs) and future driving. The automotive industry is on a path where vehicles are continuously becoming more aware of their environment due to the addition of various types of integrated sensors. At the same time, the amount of automation in vehicles increases, which, with some intermediate steps, will eventually culminate in fully automated driving without human intervention. Along this path, the amount of interactions rises, both in-between vehicles and between vehicles and other road users, and with an increasingly intelligent road infrastructure. As a consequence, the significance and reliance on capable communication systems for vehicleto-anything (V2X) communication is becoming a key asset that will enhance the performance of automated driving and increase further road traffic safety with combination of sensor-based technologies [1]

A Hansel and Gretel approach to cooperative vehicle positioning

There is little doubt in the benefit gained from cooperative modes of road transport, as agents working together generally perform better. In simple terms, this is the holistic idea that the whole is greater than the sum of its parts, commonly known as synergy. On top of this clear advantage, the complex systems theory of emergence suggests that novel strategies will develop from the as-yet-undefined patterns and structures. It is clear, however, that to facilitate this development certain technological advances need to be achieved. In this case, individual road agents need to accurately identify their location, and communicate easily and safely with other agents. This is a shift away from protective and passive systems toward preventative and active transport safety

A Hansel and Gretel approach to cooperative vehicle positioning

There is little doubt in the benefit gained from cooperative modes of road transport, as agents working together generally perform better. In simple terms, this is the holistic idea that the whole is greater than the sum of its parts, commonly known as synergy. On top of this clear advantage, the complex systems theory of emergence suggests that novel strategies will develop from the as-yet-undefined patterns and structures. It is clear, however, that to facilitate this development certain technological advances need to be achieved. In this case, individual road agents need to accurately identify their location, and communicate easily and safely with other agents. This is a shift away from protective and passive systems toward preventative and active transport safety