Characterization of vehicle penetration loss at wireless communication frequencies

Automotive window films are widely used for heat rejection, protection from ultraviolet radiations and glare control purposes. For an increased performance, these films are usually metallized since metals effectively reflect the impinging electromagnetic radiations. The expend of metallization in these films may affect the communication of radio signals into vehicles. In this perspective, the provision of reliable in-vehicle coverage is a major goal of both wireless network providers and automotive industry. In order to quantify the effects of automotive window films on communication signals inside a vehicle, this research study was undertaken with industrial cooperation. The thesis presents the characterization of Vehicle Penetration Loss (VPL) at major wireless communication frequencies based on empirical and numerical evaluation and by exploiting different window coatings including a commercially available automotive window film and Aluminium metal foil. The research involves ultra-wideband (UWB) car measurement campaign for the frequency range of 0.6-6.0 GHz in an indoor industrial environment at an isolated storage facility in Helsinki utilizing a regular sized hatchback car. Several realistic measurement scenarios were considered to obtain large measurement sets. The measurement data was post-processed using fine algorithms to exploit various channel characteristics to gain sufficient understanding of associated propagation phenomenon. Window films were also exclusively measured in a specialized environment to accurately assess the associated penetration loss. Apart from measurements, numerical analysis based on Finite-difference time-domain (FDTD) method for the assessment of VPL was carried out at discrete frequencies, 900 MHz and 1.2 GHz. The numerical approach can serve as a future alternate to measurements provided that adequate computational resources are available. The results infer that the use of metallized automotive films can severely affect the communication of radio signals into vehicles

Indoor wireless communications and applications

Chapter 3 addresses challenges in radio link and system design in indoor scenarios. Given the fact that most human activities take place in indoor environments, the need for supporting ubiquitous indoor data connectivity and location/tracking service becomes even more important than in the previous decades. Specific technical challenges addressed in this section are(i), modelling complex indoor radio channels for effective antenna deployment, (ii), potential of millimeter-wave (mm-wave) radios for supporting higher data rates, and (iii), feasible indoor localisation and tracking techniques, which are summarised in three dedicated sections of this chapter

Characterizing Multipath Radio Environments for 5G Wireless Systems and Beyond

The envelope of performance in Fifth generation (5G) technology will be much greater than what we see in legacy technologies, featuring low latency, ultra-high data rates, massive connectivity, and increased security. 5G wireless systems operating in centimeter (cm) and millimeter (mm) wave parts of the frequency spectrum must deal with all sorts of radio wave propagation conditions imposed by a radio channel. This entails thoroughly characterizing radio channels across the desired frequency range for efficient system design and performance. The primary focus of this thesis is (1) to model the interaction of radio waves with material objects in radio environments, and (2) to characterize multipath radio channels at cmWave and mmWave frequencies. The key contributions of the thesis are summarized as follows. First, a comprehensive evaluation of transmission and reflection losses for material objects in built environments is carried out at the 70 GHz frequency band. The results demonstrate that energy-efficient building windows, laminated plywood, and plasterboard are good reflectors of mmWave signals, while humans and some energy-efficient windows attenuate mmWave signals as high as 40 dB. Second, a novel method is proposed for the on-site estimation of the permittivity of built-in materials using the point cloud geometrical database and limited channel measurements of a given radio environment. The estimated material permittivities of a large indoor office are visualized through a colored three-dimensional (3D) point cloud map of the environment. Third, human blockage losses are measured through anechoic chamber measurements for 15 human subjects with different weights and sizes at 15, 28, and 60 GHz frequency bands. Moreover, a novel double-truncated multiple knife-edge (DTKME) model is proposed that reasonably predicts the measured human blockage loss for different body orientations and illuminating antenna heights. Fourth, the feasibility of applying full-wave numerical techniques for coverage predictions is determined by finite-difference time-domain (FDTD) simulations for the coverage analysis inside a small indoor office. It is transpired that the full-wave methods are computationally expensive, and a trade-off exists between the accuracy and complexity of these simulations. Finally, multipath characterization of cmWave and mmWave radio channels is performed for indoor and outdoor radio environments in terms of their power, delay, and angular domain behavior. The fluctuations in the signal envelope of mmWave channels are more significant than their cmWave counterparts. The mmWave channels exhibit less delay dispersion compared to cmWave radio channels. The spatial spread of multipath is similar in line-of-sight (LOS) conditions across cmWave and mmWave radio channels, while in non-LOS (NLOS) propagation conditions, the cmWave radio channels offer more spatial spread of multipath than mmWave radio channels

Measurements based specular reflection formulation for point cloud modelling

Describing the environment using a point cloud is a promising method for both propagation predictions and channel simulations. Recently, a specular reflection model has been proposed and verified through measurements to account for reflections from large reflecting surfaces. Here, the formulation for the specular reflections for point cloud (SRPC) is improved based on a few canonical measurements in an anechoic chamber. The specular reflection image theory for large surfaces, the Radar Cross Section equation for small surfaces, the Fresnel-Kirchhoff integral formula, and measurements are investigated. Unexpectedly to the authors, the results show that, when neglecting the diffraction effects, the contributions to the specular reflected field occur mainly from the illumination of about a third of the first Fresnel zone. A prediction of the SRPC formula is the appearance of “radio flares” due to electrically small reflecting surfaces

System Performance Assessment in Dual-Band Device-to-Device MIMO Channels

Device-to-Device (D2D) communications has been embraced as a novel approach for extending coverage in fifth-generation (5G and beyond) wireless networks. Throughput and reliability assessment of such wireless networks are therefore of utmost importance for D2D communication systems design. In this paper, we consider the capacity results of wireless propagation channels in two 5G modes namely the sub-6 GHz centimeter-wave (cm-wave) and 60 GHz millimeter-wave (mm-wave) bands for a multiple-input-multiple-output (MIMO) D2D fading channel. Results presented in this paper were obtained from propagation channel measurements jointly conducted in both cm-wave (2-6 GHz) and mm-wave (59-63 GHz) bands using an 8 × 8 MIMO virtual array setup in an outdoor environment. These measurements were conducted at the exact same locations (with constituents unchanged) in both cm-wave and mm-wave bands for comparability of results. Capacity values were computed using two power policies (with and without channel state information (CSI)). We also investigated the eigenmode spectral structure to understand the spatial correlatedness of the channel and the Rician K-factor to analyze small-scale fading in the channel. The results presented in this paper can be used by wireless systems designer for assessing the performance of D2D systems operating in the cm-wave and/or mm-wave bands for this type of environment.Peer reviewe

Validating FR2 MIMO OTA channel models in 3D MPAC

Abstract Fifth Generation (5G) technology is about to set its global footprint. Its success relies heavily on the standardization process, which is rapidly progressing to specify verification metrics and test methodologies for 5G New Radio (NR) device certifications. For this purpose, three-dimensional (3D) multiprobe anechoic chamber (MPAC) has been selected as a reliable reference solution for creating an accurate test environment. This paper reports first ever FR2 MIMO over-the-air (OTA) channel models validation measurements according to 3GPP specified verification procedure. The evaluated validation metrics include power-delay profile (PDP) and power-angular spectrum (PAS) similarity percentage (PSP). The measurement results closely follow the simulated and theoretical references, thereby demonstrating the feasibility of FR2 MIMO OTA channel models validation procedure adopted by 3rd Generation Partnership Project (3GPP)