Multi-Array 5G V2V Relative Positioning: Performance Bounds

We study the performance bounds of vehicle-to-vehicle (V2V) relative positioning for vehicles with multiple antenna arrays. The Cram\'{e}r-Rao bound for the estimation of the relative position and the orientation of the Tx vehicle is derived, when angle of arrival (AOA) measurements with or without time-difference of arrival (TDOA) measurements are used. In addition, geometrically intuitive expressions for the corresponding Fisher information are provided. The derived bounds are numerically evaluated for different carrier frequencies, bandwidths and array configurations under different V2V scenarios, i.e. overtaking and platooning. The significance of the AOA and TDOA measurements for position estimation is investigated. The achievable positioning accuracy is then compared with the present requirements of the 3rd Generation Partnership Project (3GPP) 5G New Radio (NR) vehicle-to-everything (V2X) standardization

Measurement Based Vehicle-to-Vehicle Multi-link Channel Modeling and Relaying Performance

There has been intense research in vehicular communication in order to provide reliable low-latency vehicular communication links for developing intelligent transportation system (ITS). As one of the important properties, vehicle-to-vehicle (V2V) communication is learned to be inherently non-stationary due to the high mobility of both transmitter (TX) and receiver (RX). Therefore, the V2V system behavior is essentially different from previous mobile communication studies and needs to be understood. For V2V wireless communication systems, it is crucial to model the vehicular channel accurately to evaluate the quality of the system level applications. Among all channel properties in a V2V system, the shadow fading (i.e. large scale fading, LSF) from other vehicles has a significant adverse impact on the system performance. One promising approach to overcome this issue is by implementing multi-hop technology on the vehicular ad hoc network (VANETs). One goal of this thesis report is to implement relaying schemes on simulated Rician channel based on measurements to evaluate the performance of multi-hop technology in V2V systems. Two relaying schemes, Amplify-and-Forward (AF) and Decode-and-Forward (DF), are employed in the bit level simulation. The results of packet error rate (PER) are evaluated together with non-relaying situation for convoy and overtaking scenarios, respectively. Furthermore, a statistic model is created to model the measured highway environment. Pathloss parameters and shadowing loss together with correlation coefficients are derived. Line-of-sight (LOS) and obstructed line-of-sight (OLOS) conditions are manually separated through on-board video. Each scenario has its own parameter set. Maximum likelihood estimation (MLE) is utilized on the pathloss model to compensate the biasing from the measurement hardware. Also the shadowing is modeled as correlated Gaussian and we derived the decorrelation distance from the auto-correlation function (ACF). The model is also validated against the measurements. For an ad hoc network, the diversity schemes would be strongly affected by the multilink correlation. Only a few joint correlation studies for mobile ad hoc network have been made, but rarely for VANETs. The last goal of this report is to study the joint correlation on VANETs based on measurements for four-dimensional position joint correlation model where shadowing is affected by the vehicle distance. To be precise, we focus on the joint correlation of large scale fading affected by the distances between the two receiver vehicles under the same car obstruction. Finally, a stochastic model based on the sum of sinusoids approach is implemented.The fifth generation wireless systems denotes the next major phase of mobile telecommunications standards and is expected to meet consumer demands by 2020. One of the major approach is the vehicular ad hoc networks, which is a spontaneous creation of a wireless network for data exchange to the domain of vehicles. As a key component of the intelligent transportation systems, it is extremely importance to model the vehicular propagation channel in order to meet the requirement of low latency and high reliability. There are many parameters that could describe the channel characteristics. Among them all, the vehicular shadowing has a significant advise impact on the system performance which describes the signal fluctuation affected by an obstruction vehicle. In order to study it, a measurement was designed and took place in Sweden, road Rv 40. Four Volvo cars were forming convoy and overtaking scenarios with equipped signal-transmit-receive devices. Three major works are done in this thesis project based on this measured highway scenario: Firstly, a simulation is designed based on the multi-hop technology. A scenario is simulated where a source car sends packets to a destination car with the help of a relay car. All the packets are randomly generated with each containing proper coding and modulation to enhance the transmission quality as well as to check the success or failure of the transmission. The power properties of the wireless channels between each car-link are captured from the the measurements. They are simulated with a vehicular-based distribution while each byte of the signal would experiences a vehicular channel more close to practice. Two relaying schemes are implemented in the simulation with a different reaction at the relay car after receiving the signal from the source. The destination then combines the two signals from the source and relay. It decodes the signal and records the decoding results. For each observation, the ratio of successfully transmission number and total transmission number is recorded as packet error rate. Eventually, the packet error rate performances of different schemes are compared and evaluated. Secondly, based on whether the link between antennas are obstructed, two scenarios are separated manually by watching the on-board videos. After that, the signal penetration based on transmission distance and the signal fluctuation affected by large obstructions are modeled based on the individual scenario. An advanced estimation method is employed during the modeling of the signal penetration to efficiently include the lost packet information. As for the modeling of the signal fluctuation, an extended distribution is used to describe the facts that, when a transmission link is obstructed by another vehicle, it normally remains obstructed for a certain amount of time. Eventually, channel power can be regenerated based on the model containing the measured channel properties. At last, a model is created to describe the joint effects on the signal fluctuation based on the vehicles' movement and the distances between two receive cars whose signals are obstructed by the same vehicle. The vehicular shadowing following a certain distribution is approximately represented by the sum of many sinusoid waves with random phases and chosen frequencies. The frequencies are generated based on the power and joint correlation properties of the measured channel based on the two effects

A Measurement Based Shadow Fading Model for Vehicle-to-Vehicle Network Simulations

The vehicle-to-vehicle (V2V) propagation channel has significant implications on the design and performance of novel communication protocols for vehicular ad hoc networks (VANETs). Extensive research efforts have been made to develop V2V channel models to be implemented in advanced VANET system simulators for performance evaluation. The impact of shadowing caused by other vehicles has, however, largely been neglected in most of the models, as well as in the system simulations. In this paper we present a shadow fading model targeting system simulations based on real measurements performed in urban and highway scenarios. The measurement data is separated into three categories, line-of-sight (LOS), obstructed line-of-sight (OLOS) by vehicles, and non line-of-sight due to buildings, with the help of video information recorded during the measurements. It is observed that vehicles obstructing the LOS induce an additional average attenuation of about 10 dB in the received signal power. An approach to incorporate the LOS/OLOS model into existing VANET simulators is also provided. Finally, system level VANET simulation results are presented, showing the difference between the LOS/OLOS model and a channel model based on Nakagami-m fading.Comment: 10 pages, 12 figures, submitted to Hindawi International Journal of Antennas and Propagatio

Methodologies for Future Vehicular Digital Twins

The role of wireless communications in various domains of intelligent transportation systems is significant; it is evident that dependable message exchange between nodes (cars, bikes, pedestrians, infrastructure, etc.) has to be guaranteed to fulfill the stringent requirements for future transportation systems. A precise site-specific digital twin is seen as a key enabler for the cost-effective development and validation of future vehicular communication systems. Furthermore, achieving a realistic digital twin for dependable wireless communications requires accurate measurement, modeling, and emulation of wireless communication channels. However, contemporary approaches in these domains are not efficient enough to satisfy the foreseen needs. In this position paper, we overview the current solutions, indicate their limitations, and discuss the most prospective paths for future investigation.Comment: Submitted to IEEE Intelligent Transportation Systems Magazin

Agile Calibration Process of Full-Stack Simulation Frameworks for V2X Communications

Computer simulations and real-world car trials are essential to investigate the performance of Vehicle-to-Everything (V2X) networks. However, simulations are imperfect models of the physical reality and can be trusted only when they indicate agreement with the real-world. On the other hand, trials lack reproducibility and are subject to uncertainties and errors. In this paper, we will illustrate a case study where the interrelationship between trials, simulation, and the reality-of-interest is presented. Results are then compared in a holistic fashion. Our study will describe the procedure followed to macroscopically calibrate a full-stack network simulator to conduct high-fidelity full-stack computer simulations.Comment: To appear in IEEE VNC 2017, Torino, I

Empirical multi-band characterization of propagation with modelling aspects for communictions

Diese Arbeit präsentiert eine empirische Untersuchung der Wellenausbreitung für drahtlose Kommunikation im Millimeterwellen- und sub-THz-Band, wobei als Referenz das bereits bekannte und untersuchte sub-6-GHz-Band verwendet wird. Die großen verfügbaren Bandbreiten in diesen hohen Frequenzbändern erlauben die Verwendung hoher instantaner Bandbreiten zur Erfüllung der wesentlichen Anforderungen zukünftiger Mobilfunktechnologien (5G, “5G and beyond” und 6G). Aufgrund zunehmender Pfad- und Eindringverluste bei zunehmender Trägerfrequenz ist die resultierende Abdeckung dabei jedoch stark reduziert. Die entstehenden Pfadverluste können durch die Verwendung hochdirektiver Funkschnittstellen kompensiert werden, wodurch die resultierende Auflösung im Winkelbereich erhöht wird und die Notwendigkeit einer räumlichen Kenntnis der Systeme mit sich bringt: Woher kommt das Signal? Darüber hinaus erhöhen größere Anwendungsbandbreiten die Auflösung im Zeitbereich, reduzieren das small-scale Fading und ermöglichen die Untersuchung innerhalb von Clustern von Mehrwegekomponenten. Daraus ergibt sich für Kommunikationssysteme ein vorhersagbareres Bild im Winkel-, Zeit- und Polarisationsbereich, welches Eigenschaften sind, die in Kanalmodellen für diese Frequenzen widergespiegelt werden müssen. Aus diesem Grund wurde in der vorliegenden Arbeit eine umfassende Charakterisierung der Wellenausbreitung durch simultane Multibandmessungen in den sub-6 GHz-, Millimeterwellen- und sub-THz-Bändern vorgestellt. Zu Beginn wurde die Eignung des simultanen Multiband-Messverfahrens zur Charakterisierung der Ausbreitung von Grenzwert-Leistungsprofilen und large-scale Parametern bewertet. Anschließend wurden wichtige Wellenausbreitungsaspekte für die Ein- und Multibandkanalmodellierung innerhalb mehrerer Säulen der 5G-Technologie identifiziert und Erweiterungen zu verbreiteten räumlichen Kanalmodellen eingeführt und bewertet, welche die oben genannten Systemaspekte abdecken.This thesis presents an empirical characterization of propagation for wireless communications at mm-waves and sub-THz, taking as a reference the already well known and studied sub-6 GHz band. The large blocks of free spectrum available at these high frequency bands makes them particularly suitable to provide the necessary instantaneous bandwidths to meet the requirements of future wireless technologies (5G, 5G and beyond, and 6G). However, isotropic path-loss and penetration-loss are larger with increasing carrier frequency, hence, coverage is severely reduced. Path-loss can be compensated with the utilization of highly directive radio-interfaces, which increases the resolution in the angular domain. Nonetheless, this emphasizes the need of spatial awareness of systems, making more relevant the question “where does the signal come from?” In addition, larger application bandwidths increase the resolution in the time domain, reducing small-scale fading and allowing to observe inside of clusters of multi-path components (MPCs). Consequently, communication systems have a more deterministic picture of the environment in the angular, time, and polarization domain, characteristics that need to be reflected in channel models for these frequencies. Therefore, in the present work we introduce an extensive characterization of propagation by intensive simultaneous multi-band measurements in the sub-6 GHz, mm-waves, and sub-THz bands. Firstly, the suitability of the simultaneous multi-band measurement procedure to characterize propagation from marginal power profiles and large-scale parameters (LSPs) has been evaluated. Then, key propagation aspects for single and multi-band channel modelling in several verticals of 5G have been identified, and extensions to popular spatial channel models (SCMs) covering the aforementioned system aspects have been introduced and evaluated