Radio Channel Characterization for Future Wireless Networks and Applications

The new frontier of Above-6GHz bands is revolutionizing the field of wireless telecommunications, requiring new radio channel models to support the development of future Giga-bit-per-second systems. Recently, deterministic ray-based models as Ray Tracing are catching on worldwide thanks to their frequency-agility and reliable predictions. A modern 3D Ray Tracing developed at University of Bologna has been indeed calibrated and used to investigate the Above-6GHz radio channel properties. As starting point, an item-level electromagnetic characterization of common items and materials has been achieved successfully to obtain information about the complex permittivity, scattering diagrams and even de-polarization effects, both utilizing Vector Spectrum Analyzer (at 7-15GHz) and custom Channel Sounder (at 70GHz). Thus, a complete tuning of the Ray Tracing has been completed for Above-6GHz frequencies. Then, 70GHz indoor doubledirectional channel measurements have been performed in collaboration with TU Ilmenau, in order to attain a multidimensional analysis of propagation mechanisms in time and space, outlining the differences between Below- and Above-6GHz propagation. Furthermore, multi-antenna systems, as Multiple-Input-Multiple- Output (MIMO) and Beamforming have been taken into considerations, as strategic technologies for Above-6GHz systems, focusing on their implementation, limits and differences. Finally, complex system simulations of Space-Division-Multiple- Access (SDMA) networks in indoor scenarios have been tested, to assess the capabilities of Beamforming. In particular, efficient Beam Search and Tracking algorithms have been proposed to assess the impact of interference on Multi-User Beamforming at 70GHz and, also, novel Multi-Beam Beamforming schemes have been tested at 60GHz to investigate diversity strategies to cope with NLOS link and Human Blockage events. Moreover, the novel concept of Ray-Tracing-assisted Beamforming has been outlined, showing that ray-based models represent today the promising key tools to evaluate, design and enhance the future Above-6GHz multi-antenna systems

A Wideband OFDM MIMO Measurement System for Antenna Evaluation

An OFDM-MIMO testbed based on a SDR platform with very flexible antenna positioning system has been designed and presented for WLAN applications. Antenna positioning allows the proper spatial characterization of radio channel links in real scenarios where future wireless networks will be deployed. Some measurements in real indoor scenarios proving reconfigurable antennas are been carried out leading to some interesting results that will be presented in the conferenc

Mathematical modeling of ultra wideband in vivo radio channel

This paper proposes a novel mathematical model for an in vivo radio channel at ultra-wideband frequencies (3.1–10.6 GHz), which can be used as a reference model for in vivo channel response without performing intensive experiments or simulations. The statistics of error prediction between experimental and proposed model is RMSE = 5.29, which show the high accuracy of the proposed model. Also, the proposed model was applied to the blind data, and the statistics of error prediction is RMSE = 7.76, which also shows a reasonable accuracy of the model. This model will save the time and cost on simulations and experiments, and will help in designing an accurate link budget calculation for a future enhanced system for ultra-wideband body-centric wireless systems