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- Fundamental Solution for Natural Powers of the Fractional Laplace and Dirac Operators in the Riemann–Liouville SensePublication . Teodoro, A. Di; Ferreira, M.; Vieira, N.In this paper, we study the fundamental solution of natural powers of the n-parameter fractional Laplace and Dirac operators defined via Riemann–Liouville fractional derivatives. To do this we use iteration through the fractional Poisson equation starting from the fundamental solutions of the fractional Laplace Δa+α and Dirac Da+α operators, admitting a summable fractional derivative. The family of fundamental solutions of the corresponding natural powers of fractional Laplace and Dirac operators are expressed in operator form using the Mittag–Leffler function.
- A Framework for the inclusion of RF transparency parameters into BIM databasesPublication . Caldeirinha, Rafael F. S.; Fernandes, Telmo R.; Cuinas, Inigo; Rodrigues, HugoWith the deployment of an ever increasing number of radio based services, such as 5G, a complete understanding of the radio propagation phenomena inside buildings is expected to be of utterly importance in the future, both for appropriate indoor radio planning and assessment of human exposure to electromagnetic radiation. Surprisingly, no regulations are currently in force which cover the RF transparency of buildings. It may well be justifiable on health and safety grounds (i.e. use of mobile phones or TETRA radio in emergency situations). For instance, there is substantial use of metal within current buildings which causes major problems for radio propagation. On the other hand, Building Information Modelling (BIM) is seen as a key technology and methodology to improve productivity and integration across various disciplines throughout the Architecture, Engineering and Construction (AEC) value chain. Although many valuable information has been added to such databases in the last years, detailed information about the radio wave propagation characteristics of buildings and building materials have been absent. This paper presents a multilayer Electromagnetic (EM) simulation tool to assess the radiofrequency transparency of building wall structures, which allows to explore different layer arrangements and determine the overall frequency response. In particular, the assessment of EM properties of different types of building walls commonly used in building construction, combined into one complete EM tool, is proposed. This is sought to be a valuable feature to be considered towards the integration with BIM-based simulation methods to provide unprecedented visualisation of the radio coverage within the building, allowing for the optimisation to meet specific facility radio requirements.
- A novel MIMO-OFDM Alamouti architecture for 5G systems at 26 GHzPublication . Gomes, Rodolfo; Duarte, Luis; Ribeiro, Carlos; Hammoudeh, Akram; Caldeirinha, Rafael F. S.This paper introduces a novel 5G Millimetre-wave (mmWave) real-time Multiple-Input Multiple-Output (MIMO) testbed architecture aimed to tackle the 5G communication requirements. In this context, a 2x2 Alamouti coder and decoder is implemented in the VC707 Field Programmable Gate Array (FPGA) development board and its logical resources usage compared to those in the literature. In order to reduce the Hardware (HW) footprint of the proposed MIMO - Orthogonal Frequency Division Multiplexing (OFDM) Alamouti system, a pipelined modular architecture is considered, in order to boost HW utilisation and performance of MIMO-OFDM systems. A single pair of Inverse Fast Fourier Transform (IFFT)/ Fast Fourier Transform (FFT) is enough to process data for each MIMO antenna path. The achieved results show the importance of FPGA resource optimisation, demonstrating how depend coding and modulation are to hardware resources. Moreover, a Radio Frequency (RF) architecture is proposed to address 2x2 MIMO communications at 26 GHz.
- Benchmark of radio propagation path loss models applied to line-of-trees at 10, 36 and 60 GHzPublication . Leonor, Nuno; Ramos, Glaucio; Orihuela, Carlos; Mello, Luiz da Silva; Caldeirinha, RafaelIn this paper, measurements conducted in outdoor line-of-trees scenarios at 10, 36 and 60 GHz are used to provide a benchmark between various modeling approaches for radiowave propagation in the presence of vegetation. The list of selected models include the ITU-R P.833-9 recommendation for attenuation in vegetation, and an hybrid approach which uses simple empirical models to characterize the propagation phenomena in the presence of vegetation, and then uses a ray-tracing algorithm to gather all the interactions between the different trees. The performance of the selected empirical model was then assessed against the outdoor measurements and a comparative analysis is provided at the end of this paper.