The European GAIA-X project aims to create an innovative open, transparent and secure data infrastructure for different domains like energy, agriculture, and mobility. Data providers and consumers from one domain are supposed to form a data ecosystem on this infrastructure. Developing a new GAIA-X ecosystem for a particular domain is challenging because the participants of the ecosystems develop new business models and specifications of novel services while refining the requirements on the GAIA-X infrastructure, which is currently under construction. There is a need for approaches that help the consortium of participants in this innovation exploration task, i.e. to handle the complexity and provide communication means on a right level of abstraction. The Innovation Modeling Grid (IMoG) is an innovation modeling methodology with well-defined procedures that can help understand the GAIA-X problem space and present the model concisely. We applied IMoG as an innovation modeling approach on a GAIA-X ecosystem focused on mobility. In this paper, we present our experiences gained during this study. We found that using IMoG led to a better understanding of the roles, services, and interfaces in a specific GAIA-X ecosystem.

Rapid developments and emergence of diverse wireless systems call for radio frontends with agile and multistandard properties. Within this publication the performance of a direct RF digitizing ΣΔ-modulator based analog-to-digital converter (ADC) is evaluated based on orthogonal frequency division multiplex (OFDM) system simulation on the bitstream layer. The necessary transmit and receive building blocks are introduced as well as the previously developed reconfigurable ADC under test. The proposed approach allows flexible testing of different ADCs by analyzing the influence of the ADC's noise shaping on performance indicators like error vector magnitude (EVM) and symbol error rate (SER). The necessary steps for the combination of the OFDM signal generation and the system level simulation of the ΣΔ-modulator-ADC into a multi-domain simulation are introduced and discussed.

This paper presents the design and evaluation of a ΣΔ-modulator based analog-to-digital converter (ADC) for direct RF digitization within a multi-standard vehicular connectivity architecture. Upcoming trends and changes which will require new architecture concepts for connectivity in the automotive domain are discussed. Hardware requirements are derived. Based on these goals, a reconfigurable ADC is designed with capabilities of digitizing all relevant wireless services for vehicular use within the frequency range of 600 MHz to 6GHz. A performance assessment is done based on evaluation of the signal to noise ratio within a realistic use case where multiple services at different frequencies are successfully digitized.

In this contribution, we present the results of a measurement campaign targeting at system level evaluation of vehicular multiple-input-multiple-out (MIMO) antennas. Our measurements are performed on a test track served by a Long Term Evolution (LTE) base station operating in the 800 MHz band. We show system level evaluation results obtained by using two reference monopole antennas and two automotive qualified, integrated prototype antenna systems. The presented results are gathered in line-of-sight (LOS) as well as non-LOS conditions. As vehicular antenna systems are limited by the available integration space, we analyze the specific impact of antenna decoupling on system level performance. System level performance metrics include parameters such as ergodic capacity and condition number of the MIMO channel matrix. We achieve antenna decoupling for the reference monopoles by increasing their separation. In case of the integrated antenna system we use a decoupling branch to decrease antenna coupling and correlation at the measurement frequency. We discuss a system level evaluation process for ranking antenna systems based on channel specific parameters. The applicability of the process for MIMO system performance evaluation is shown with a comparison of an integrated antenna system with the described reference antenna system.

Future vehicles are expected to integrate multiple radio access technologies to offer traffic information services for Intelligent Transportation Systems (ITS). Dedicated short range communication (DSRC) being designed exclusively for vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication is one of the major candidates to enable such services. The focus of this paper is to shed light on the integration aspects of this technology, especially in regards to the antenna design. A methodology is presented to overcome the difficulties occurring from the integration of the antenna in the radome on the vehicle rooftop. With help of simulations and measurements it is illustrated how the conventionally unwanted dielectric lens effect of the antenna radome resulting in nulls in the radiation pattern can be used to deliberately increase the antenna performance. The performance enhancement by using the antenna radome as a dielectric lens is validated with four prototypes in a semi-anechoic chamber. It is moreover shown that simplified geometrical shapes such as cuboids can be used to describe efficiently the behavior of geometrical more complex radome designs. The greatest advantage of our proposed methodology to enhance antenna performance is that it can be employed without changes of any electronic control units. Thus it can easily be included in a running production cycle without even altering any design elements of the vehicle. To demonstrate to which degree the achieved enhancement on component level translates into system level we also present simulation results of a test scenario including a vehicle and a road-side unit. The outcome of the system level simulations shows substantial improvements in the received signal strength (RSS).

Future safety-related vehicular applications require reliable information exchange provided by Dedicated Short Range Communication (DSRC). As the wireless vehicular environment is very challenging, it is crucial to test and evaluate the performance of DSRC communications in real conditions through experimental tests. Yet, DSRC communications have been evaluated independently from vehicles, and precise knowledge related to vehicular integration effects (i.e. cable/connector loss, antenna placement, vehicle geometry, etc) on DSRC communications still lacks. In this paper, we measure aspects of vehicular integration influencing DSRC communication in field experimental tests. Considering a global link budget, we illustrate the non-negligible impacts of cable, connectors, hardware, or roof types and antenna design on the communication range. We also measure their influence on the wireless channel and show that a reasonable distance between vehicles and radio obstacles, or metallic side-reflector improve communication range. Applying these results to a Road Hazard Warning application, we illustrate that, while vehicular integration affects its performance, wireless channel effects, in particular side reflectors, partially compensate them.

In the past few years more and more wireless applications (e.g. WLAN and Bluetooth) have migrated into the automotive domain. With the increasing number of devices, coexistence investigations in the 2.45 GHz ISM band are gaining importance to enable reliable communications with real time requirements like voice transmission and streaming applications. This paper presents initial results on angle dependent path loss measurements impacted by the influence of a car body on electro-magnetic wave propagation. To this effect, a measurement methodology was developed to gather the attenuation effects of the car according to different antenna positions and measurement angles. Various kinds of attenuation measurements were performed. Vehicle shell attenuation measurements were transformed into angular-dependent path loss metrics and related to vehicle-specific attenuation properties like window inserts, roof columns, trunk or engine hood. Focus of attention was drawn to free space attenuation and intra-vehicle attenuation measurements.

To make transportation safer, more efficient, and less harmful to the environment, traffic telematics services are currently being intensely investigated and developed. Such services require dependable wireless vehicle-to-infrastructure and vehicle-to-vehicle communications providing robust connectivity at moderate data rates. The development of such dependable vehicular communication systems and standards requires accurate models of the propagation channel in all relevant environments and scenarios. Key characteristics of vehicular channels are shadowing by other vehicles, high Doppler shifts, and inherent nonstationarity. All have major impact on the data packet transmission reliability and latency. This paper provides an overview of the existing vehicular channel measurements in a variety of important environments, and the observed channel characteristics (such as delay spreads and Doppler spreads) therein. We briefly discuss the available vehicular channel models and their respective merits and deficiencies. Finally, we discuss the implications for wireless system design with a strong focus on IEEE 802.11p. On the road towards a dependable vehicular network, room for improvements in coverage, reliability, scalability, and delay are highlighted, calling for evolutionary improvements in the IEEE 802.11p standard. Multiple antennas at the onboard units and roadside units are recommended to exploit spatial diversity for increased diversity and reliability. Evolutionary improvements in the physical (PHY) and medium access control (MAC) layers are required to yield dependable systems. Extensive references are provided.

In this paper we analyze the Ricean K-factor for vehicle-to-vehicle (V2V) communications in a typical open sub-urban street crossing. The channel conditions vary from non line-of sight (NLOS) to line-of-sight (LOS). The antenna arrays used for recording the radio channels consist of 4 elements with directional radiation patterns. We measured 16 individual single-input single-output channels, with a bandwidth of 240MHz for a duration of 20 s. We performed two kind of evaluations. For the first analysis we partitioned the 240MHz bandwidth into 24 sub-bands with 10MHz each, according to 802.11p. The small-scale fading of the first delay bin is Ricean distributed with a time-varying K-factor. The later delay bins are mostly Rayleigh distributed. We observe that the large/small K-factor values are not necessarily correlated with the received power. We show that the K-factor can not be assumed to be constant in time, frequency, and space. The antenna radiation patterns, and the illuminated objects by them at different time instances are the cause of these variations. The second evaluation considers the 240MHz bandwidth, and the narrow-band K-factor is calculated for each frequency bin, with Δf = 312 kHz. We corroborate the need to consider the frequency variation of the K-factor. We conclude that a multi-dimensional varying K-factor models the large-scale statistical behaviour more accurately than a constant K-factor.

This paper presents the results of an empirical study of wireless propagation channels for vehicle-to-vehicle communications in street intersections, a scenario especially important for collision avoidance applications. The results are derived from a channel measurement campaign performed at 5.6 GHz in four different types of urban intersections. We present results on typical power delay profiles, pathloss and delay spreads and discuss important propagation mechanisms. By comparing the results of the different intersections, we find that absence of line-of-sight is problematic for system coverage, especially when there are few other significant scattering objects in and around the intersection. Roadside buildings can create important propagation paths that account for a considerable part of the total received power.

In this paper we present an overview of a vehicle-to-vehicle radio channel measurement campaign at 5.6 GHz. The selected measurement scenarios are based on important safety-related applications. We explain why these scenarios are interesting from the aspect of radio propagation. Further we describe the power-delay profile and the Doppler spectral density of two situations especially suitable for collision avoidance applications: A traffic congestion situation where one car is overtaking another one, and a general line-of-sight obstruction between the transmitter and the receiver car. The evaluations show that in these situations the radio channel is highly influenced by the rich scattering environment. Most important scatterers are traffic signs, trucks, and bridges, whereas other cars do not significantly contribute to the multipath propagation.

Wideband antenna configurations that exhibit efficient fading mitigation in typical configurations of portable radios are intensively researched due to the aim of integrating them into next generation wireless multi-radio communication systems. Especially in indoor scenarios with severe polarization fading, polarization diversity reception is a well known technique to enhance link reliability. By adding additional branches for signal reception to the diversity dimension of the receive configuration, quality of service can be enhanced furthermore. This investigation is related to the combined use of spatial- and polarization diversity reception for a wideband coverage of communication services in the frequency band from 1.0 GHz to 6.0 GHz. For that reason self complementary, logarithmically-periodic antenna modules with dual polarized transmission behavior and an optimized trapezoidal shape are considered in an array configuration of small size. Measurement results for antenna radiation- and impedance behavior are presented and the respective diversity performance is computed in a simplified stochastic model for the communication channel.

Antenna systems for broadband polarization diversity reception rank among the emerging key technologies in next generation wireless communication systems. In order to suppress multipath conditioned polarization fading in typical applications of portable radios, antenna modules with dual-polarized transmission behavior are to be used. Self-complementary, logarithmically-periodic antennas serve as suitable representatives for the realization of broadband antenna structures and can be favorably used in polarization diverse transmission systems. Applying usual diversity combination techniques at the receiver, high diversity gains could be achieved over a wide frequency band incorporating planar, dual-polarized log.-per. four-arm antennas

For wideband data transmission, logarithmically periodic antenna modules may be used, featuring polarization invariant transmission characteristics for the suppression of multipath conditioned polarization fading. To obtain compact antenna sizes, adequate miniaturization procedures can be taken into account, so that a reduction of the lower operating critical frequencies can be achieved under adherence to the corresponding polarization purity. Thus broadband polarization diversity antennas of compact design can be realized, which are very well suited for the employment in the field of mobile data communications.