Taulant Berisha

In this paper, we investigate the systematic change in the signal quality of mobile telecommunication systems inside a high-speed train. Using commercial mobile phones, we perform measurements inside a carriage of a high-speed train with an installed repeater and inside a carriage of a different high-speed train equipped with low radio frequency attenuation windows. We carry out additional reference measurements inside regular carriages of a high speed train. We use the adjusted Harrell–Davis method and the nonparametric bootstrap to test multiple quantiles of samples from the key performance indicators produced by the commercial mobile phones. In addition, we propose a common framework to standardize future comparisons on such studies. The results confirm considerable improvements in signal quality resulting from both the repeater and low RF attenuation windows.

Antennas with a massive amount of elements at one end are among 5G mobile communication key technologies for which spectral efficiency is enhanced by serving many users in parallel over tailored minimally interfering beams. This requires channel models that characterize the propagation environment in both azimuth and elevation. Additionally, the channel model has to capture spatial correlation effects among closely located positions, knowing that the propagation characteristics change gradually over the network area. In order to simulate mobile users or advanced beamforming strategies based on user location or angular information, it is crucial that spatial consistency is included in the applied channel models. This paper introduces a novel model for spatial consistency that is applicable to all prevalent geometry-based stochastic channel models. We provide a detailed explanation of the model and analyze its statistical properties and show its behavior when applied to the 3GPP 3D channel model as an example. To validate our model, we perform extensive ray-tracing simulations and show that our model is in a very good agreement with the statistical channel properties from ray-tracing. Following hypothesis testing over obtained ray-tracing statistics, we are able to parametrize our model for various 3GPP scenarios under LOS and NLOS propagation conditions. Finally, complementary aspects such as simulation complexity are discussed and a guideline on model implementation is provided.

Providing seamless connectivity to mobile users on-board railway vehicles is quickly gaining ground as part of the society in motion. Today, the main challenge for academia and industry coping with service quality improvements for smartphone users stems from a few tens of decibels vehicle penetration loss impacting mobile communication frequencies. To deal with this, we demonstrate two designs such as frequency selective surface-and amplify-and-forward repeater-aided railway vehicles. In this study, we use rank-based nonparametric inferential approach to assess the service quality improvements of various smartphone placements on-board railway vehicles. As part of the presented framework, we demonstrate the problem of characterizing vehicle penetration loss along particular railway tracks. All in all, the proposed framework is evaluated on inter-city and regional trains as well as over two heavy-traffic railway environments in Austria. The smartphone users placed next to frequency selective surface structures as well as in proximity of an amplify-and-forward repeater are shown to gain in coverage the most.