This paper quantifies the weight of the different physical mechanisms (reflection, diffraction, and scattering) in a typical indoor THz wireless communication environment and provides an intercomparison of raytracing tools. Two state-of-the-art raytracing tools – Wireless InSite and Sionna – are utilized to analyze the capabilities of currently available open-source and commercial raytracing engines for THz simulations. A channel sounder measurement campaign at 300 GHz was conducted in a conference room at Fraunhofer HHI, which is used to validate the raytracing simulations. Additionally, the measurements are compared to a proprietary raytracer, optimized for THz simulations. This paper presents a guideline to increase the capabilities of state-of-the-art raytracing tools, to obtain good results for high frequency simulations. The comparisons show, that currently used raytracing tools are not sufficiently accurate for THz simulations. However, these inaccuracies can be mitigated by the implementation of new features, such as the inclusion of different scattering mechanisms and the incorporation of atmospheric attenuation, while utilizing precise geometry and accurate material parameter models.

The modeling of radio links plays a crucial role in achieving mission success of unmanned aerial vehicles (UAVs). By simulating and analyzing communication performance, operators can anticipate and address potential challenges. In this paper, we propose a full-featured UAV software-in-the-loop digital twin (SITL-DT) for a heavy-lifting hexacopter that integrates a radio link module based on an experimental path loss model for ‘Open’ category Visual Line of Sight (VLOS) conditions and drone-antenna radiation diagrams obtained via electromagnetic simulation. The main purpose of integrating and simulating a radio link is to characterize when the communication link can be conflicting due to distance, the attitude of the aircraft relative to the pilot, and other phenomena. The system architecture, including the communications module, is implemented and validated based upon experimental flight data.

Abstract In order to provide interactive capabilities within the context of Internet of Thing (IoT) applications, wireless communication systems play a key role, owing to in-herent mobility, ubiquity and ease of deployment. However, to comply with Quality of Service (QoS) and Quality of Experience (QoE) metrics, coverage/capacity analysis must be performed, to account for the impact of signal blockage as well as multiple interference sources. This analysis is especially complex in the case of indoor scenarios, such as those derived from Industrial Internet of Things (IIoT). In this work, a fully volumetric approach based on hybrid deterministic 3D Ray Launching is employed providing precise wireless channel characterization and hence, system level analysis of indoor scenarios. Coverage/capacity, interference mapping and time domain characterization estimations will be derived, considering different frequencies of operation below 6 GHz. The proposed methodology will be tested against a real measurement scenario, providing full flexibility and scalability for adoption in a wide range of IIoT capable environments.

Abstract In this article, we propose a new pilot mapping method to jointly estimate the channel state information of the user while reducing the interference effects of multiuser multicell mobile scenarios. The problem of achieving the wireless performance of the minimum mean square error (MMSE) receiver with the maximum ratio (MR) combiner for massive multiple‐input multiple‐output (MIMO) systems in the frequency bands of 2.5 GHz and 28 GHz is addressed. By transmitting fewer pilots in the uplink communications and arranging those pilots to reduce interuser interference, we can achieve higher spectral efficiency (SE) with the MR and MMSE receivers. Numerical results show significantly fewer floating‐point operations for MIMO processing when the proposed pilot mapping strategy is combined with Kalman filtering estimation and MR processing, achieving an SE comparable to the MMSE receiver.

In this work, Vehicle-to-everything (V2X) wireless communications performance is analyzed, in order to account for inherent scenario complexity, in the deployment phase of wireless systems towards the implementation of a Context Aware environment. An urban environment has been simulated by means of an in-house three-dimensional (3D) Ray Launching algorithm, coupled with a microscopic vehicular movement simulator, accounting for embedded urban elements as well as variable traffic densities within the complex environment. Large-scale and small-scale results are presented, as well as statistical analysis of the impact of different traffic densities. A campaign of measurements in the same real scenario has been performed, showing good agreement with wireless channel estimations for the considered frequency. These results can aid in V2X deployment configurations in urban environments, in order to minimize power consumption, optimize interference levels and increase overall system performance.

In this work, a comparative analysis is performed to study the bit error rate and error vector magnitude achieved with the least‐squares (LS), the minimum mean squared error (MSE), and the Kalman filter (KF) channel estimators when these are applied to the maximum‐ratio combining (MRC) and the regularised zero‐forcing (RZF) receivers. The MSE achieved with the different channel estimators was also compared by varying the noise and interference power at the receiver. The proposed methodology relies on the characterisation of a massive multiple‐input multiple‐output (MIMO) channel with a quasi‐deterministic radio channel generator and a cyclic prefix orthogonal frequency division multiplexing link‐level radio simulation. The fifth‐generation (5G) new radio (NR) frame structure was used to perform channel estimation and equalisation for operation frequencies below 6 GHz. Numerical results show that the MRC receiver achieves its maximum performance with the KF estimator, especially at low signal‐to‐noise ratio scenarios, while the RZF receiver achieves its maximum performance with the LS estimation even in high interference scenarios.

In this paper, intra-wagon wireless communication performance is analyzed, in order to account for inherent scenario complexity in the deployment phase of wireless systems toward the implementation of a context-aware environment. A real commercial passenger wagon has been simulated by means of an in-house-developed 3-D ray launching code, accounting for embedded wagon elements as well as variable user densities within the passenger wagon. Onboard measurements of a designed and deployed wireless sensor network are obtained, showing good agreement with wireless channel estimations for two different frequencies of operation. Energy consumption behavior and user density impact have also been analyzed and estimated as a function of network topology and the operational mode. These results can aid in wireless transceivers deployment configurations, in order to minimize power consumption, optimize interference levels, and increase overall service performance.

This paper presents an Advanced Driver Assistance System called SesToCross, which helps those vehicle drivers who want to cross an intersection nonsignalized. SesToCross is based on a semantic expert system devoted to the intelligent management of crossroads without requiring any centralized reasoning process. SesToCross gives intelligence to each vehicle involved in the crossroad applying an ontology (CrossRoad) implemented at every single vehicle, providing a common semantic over a global and distributed architecture. SesToCross recommends, in real time, to the drivers the best choice to cross safely the intersection in an intuitive, simple, and informative, but not distractive, way. SesToCross is described, developed, and validated on real circumstances and scenarios.

Ultra‐wideband (UWB) is a very attractive technology for innovative in‐car wireless communications requiring high data rates. A designated antenna, which presents a reflection coefficient (S11) matched band comparable to the band‐pass filter (BPF) normally required at the transducers, plays a positive contribution in this in‐car application and was validated for the scenario. The inherited BPF‐like response of the antenna relaxes the specification of the front‐end BPF components of the transceivers. The in‐car propagation channel was modelled and used to validate the BPF‐like antenna. For the modelling, a comprehensive set of well‐defined measurements (using a standard antenna) were used to set‐up the in‐car channel simulator and simulated results were used to validate the BPF‐like antenna. In addition, the performance of the UWB radio system is studied and the probability of errors over the communication channel compared using the standard and the BPF‐like antenna by predictions.

Wireless communications systems have been rapidly growing during the last two decades, and they are gaining a significant role for multiple communication tasks within public transportation buses. In this paper, the impact of topology and morphology of different types of urban buses is analyzed with the aid of an in-house developed 3D ray launching code and compared with onboard measurements of a deployed wireless sensor network (WSN). The presence of human beings has been taken into account, showing a significant influence in the signal attenuation in the case of considering persons. In addition, the statistical analysis of simulation results considering both large- and small-scale fading has been performed, providing good agreement with statistics for typical indoor environments. In addition, a WSN has been programmed and deployed within the buses in order to analyze topological impact with overall system performance, with the aim of minimizing the energy consumption as well as nondesired interference levels. The use of deterministic techniques destined to consider the inherent complexity of the buses can aid in wireless system planning in order to minimize power consumption and increase overall system capacity.

In this work, the characteristics radiopropagation of wireless systems within complex indoor scenarios is presented. An analysis of the physical radio channel propagation inside different complex indoor scenarios is presented based on three-dimensional ray launching in house code. The influence of topology as well as morphology of complex indoor scenarios in the deployment of wireless sensor networks and wireless systems is analyzed. The use of adequate radioplanning strategies lead to optimal wireless network deployments in terms of capacity, quality of service, and reduced power consumption.