Experimental study of MIMO-OFDM transmissions at 94 GHz in indoor environments

Millimeter wave (mm-wave) frequencies have been proposed to achieve high capacity in 5G communications. Although meaningful research on the channel characteristics has been performed in the 28, 38and 60 GHz bands ─in both indoor and short-range scenarios─,only a small number of trials (experiments) have been carried out in other mm-wave bands. The objective of this work is to study the viability and evaluate the performance of the 94 GHz frequency band for MIMO-OFDM transmission in an indoor environment. Starting from a measurement campaign, the performance of MIMO algorithms is studied in terms of throughput for four different antenna configurations.This work was supported in part by the Ministerio de Economía y Competitividad MINECO, Spain under Grant TEC2016-78028-C3-2-P, and in part by the European FEDER funds

Investigation of QoS Performance Evaluation over 5G Network for Indoor Environment at millimeter wave Bands

One of the key advancement in next-generation 5G wireless networks is the use of high-frequency signals specifically those are in the millimeter wave (mm-wave) bands. Using mmwave frequency will allow more bandwidth resulting higher data rates as compared to the currently available network. However, several challenges are emerging (such as fading, scattering, propagation loss etc.), when we propagate the radio signal at high frequencies. Optimizing propagation parameters of the mm-wave channels system are much essential for implementing in the realworld scenario. To keep this in mind, this paper presents the potential abilities of high frequencies signals by characterizing the indoor small cell propagation channel for 28 GHz, 38 GHz, 60 GHz and 73 GHz frequency band, which is considered as the ultimate frequency choice for many of the researchers. The most potential Close-In (CI) propagation model for mm-wave frequencies is used as a Large-scale path loss model. The results have been collected concerning the capacity of users to evaluate the average user throughput, cell-edge user throughput, average cell throughput, spectral efficiency and fairness index. The statistical results proved that these mm-wave spectrum gives a sufficiently greater overall performance and are available for use in the next generation 5G mobile communication network

RIS-Aided Wireless Communications: Prototyping, Adaptive Beamforming, and Indoor/Outdoor Field Trials

The prospects of using a Reconfigurable Intelligent Surface (RIS) to aid wireless communication systems have recently received much attention from academia and industry. Most papers make theoretical studies based on elementary models, while the prototyping of RIS-aided wireless communication and real-world field trials are scarce. In this paper, we describe a new RIS prototype consisting of 1100 controllable elements working at 5.8 GHz band. We propose an efficient algorithm for configuring the RIS over the air by exploiting the geometrical array properties and a practical receiver-RIS feedback link. In our indoor test, where the transmitter and receiver are separated by a 30 cm thick concrete wall, our RIS prototype provides a 26 dB power gain compared to the baseline case where the RIS is replaced by a copper plate. A 27 dB power gain was observed in the short-distance outdoor measurement. We also carried out long-distance measurements and successfully transmitted a 32 Mbps data stream over 500 m. A 1080p video was live-streamed and it only played smoothly when the RIS was utilized. The power consumption of the RIS is around 1 W. Our paper is vivid proof that the RIS is a very promising technology for future wireless communications.Comment: 13 pages, 18 figures, submitte

RMS delay spread vs. coherence bandwidth from 5G indoor radio channel measurements at 3.5 GHz band

Our society has become fully submersed in fourth generation (4G) technologies, setting constant connectivity as the norm. Together with self-driving cars, augmented reality, and upcoming technologies, the new generation of Internet of Things (IoT) devices is pushing the development of fifth generation (5G) communication systems. In 5G architecture, increased capacity, improved data rate, and decreased latency are the objectives. In this paper, a measurement campaign is proposed; we focused on studying the propagation properties of microwaves at a center frequency of 3.5 GHz, commonly used in 5G cellular networks. Wideband measurement data were gathered at various indoor environments with different dimensions and characteristics. A ray-tracing analysis showed that the power spectrum is dominated by the line of sight component together with reflections on two sidewalls, indicating the practical applicability of our results. Two wideband parameters, root mean square delay spread and coherence bandwidth, were estimated for the considered scenarios, and we found that they are highly dependent on the physical dimension of the environment rather than on furniture present in the room. The relationship between both parameters was also investigated to provide support to network planners when obtaining the bandwidth from the delay spread, easily computed by a ray-tracing tool

New Radio Small Cell Propagation Environment

The characterization of the wireless medium in indoor small cell networks is essential to obtain appropriate modelling of the propagation environment. This dissertation on ”MeasurementBased Characterization of the 5G New Radio Small Cell Propagation Environment” has been developed in an experimental environment. The underlying tasks are divided into three phases. The first phase took place in the laboratory of the Instituto de Telecomunicações – Covilhã, located in the Departamento de Engenharia Electromecânica of Universidade da Beira Interior. During this part of the research, spectrum measurements and the characterization of the S11 parameter (response in the first port for the signal incident in the first port) have been made experimentally through the printed circuit board antennas in the 2.6 GHz and 3.5 GHz frequency bands operating in the 2.625 GHz and 3.590 GHz center frequency, manufactured by us. The fabrication of the antennas was preceded by the simulation in the student version CST STUDIO software. In this phase, the spectrum measurements and the characterization of Smith Chart have been made to measure gain and impedance using the Rohde & Schwarz Vector Network Analyzer (VNA) from IT laboratory. Based on mathematical calculations and considerations on the conductivity and permeability of the environment, the antennas were built for use in indoor and outdoor environments. The developed antennas are characterized by their bandwidth and their radiation characteristics. The second phase took place in the three rooms adjacent to the laboratory, in which the srsLTE emulation software was applied to the 4G indoor scenario. The experimental setup includes three elements, namely a base station (BS or 4G eNodeB), which transmits the communication signal and which served as a signal source, a user equipment (UE), and an interfering eNodeB. The size of each room is 7.32 × 7.32 square meters. While room 1 is the room of interest, where theoretical and practical measurements took place, BSs that act as wireless interfering nodes are also separately considered either in room 2 or room 3. By varying the UE positions within room 1, it was possible to verify that the highest values of the received power occur close to the central BS. However, the received power does not decrease suddenly because of the reduced gain in the radiation pattern in the back part of the antenna. In addition, it was demonstrated that there is an effect of “wall loss”proven by the path loss increase between room 1 and room 2 (or between room 2 and 3). If we consider an attenuation for each wall of circa 7-9 dB the trend of the WINNER II at 2.625 GHz model for the interference coming across different walls is verified. Future work includes to investigate the 3.5 GHz frequency band. The third phase is being carried out at the facilities of the old aerodrome of Covilhã which, using a temporary license assigned to us by Instituto de Comunicações Português (ICP-ANACOM) as the two first phases. The aim of this phase is to investigate the two-slope behaviour in the UMi scenario. Very initial LTE-Advanced tests have been performed to verify the propagation of the two ray (with a reflection in the asphalt) from BS implemented with USRP B210 and srsLTE system by considering an urban cell with a length of 80 m and an interfering base station at 320 m, at 2500 - 2510 MHz (DL - Downlink) by now, mainly due to the current availability of a directional antenna in this specific band.A investigação de sinais rádio em comunicações sem fios continua a gerar considerável interesse em todo mundo, devido ao seu amplo leque de aplicações, que inclui a troca de dados entre dois ou mais dispositivos, comunicações móveis e via Wi-Fi, infravermelho, transmissão de canais de televisão, monitorização de campos, proteção e vigilância costeira e observação ambiental para exploração. A tecnologia de ondas de rádio é o um dos vários recursos que viabilizam as comunicações de alta velocidade e encurta distâncias entre dois pontos em comunicação. Na realidade, caracterização da comunicação em redes com pequenas células é essencial para obter uma modelização apropriada de ambiente de propagação. Esta dissertação sob o tema ”Measurement-Based Characterization of the 5G New Radio Small Cells Propagation Envioronment” foi desenvolvida num ambiente experimental, cujas tarefas foram divididas em fases. A primeira fase teve lugar no laboratório do Instituto de Telecomunicações da Covilhã (IT), afeto ao Departamento de Engenharia Eletromecânica. Nela foram feitas as simulações das antenas no software CST STUDIO, versão do estudante que foram utilizadas nos equipamentos durante as medições. Seguiu-se a padronização das mesmas nas faixas dos 2.6 GHz e 3.5 GHz, nas frequências centrais de 2.625 GHz e 3.590 GHZ, usando placas de circuitos impressos. Em seguida, foram feitas as medições do espectro e a caraterização do S11 e da carta de Smith para medir a impedância de entrada e o ganho. As medições foram feitas com recurso ao Vector Network Analyzer (VNA). Com base em cálculos matemáticos e considerações sobre a condutividade e permeabilidade do ambiente, as antenas foram construídas para uso em ambientes internos e externos e com ou sem interferentes. As antenas desenvolvidas são caracterizadas por sua largura de banda e suas características de radiação. A segunda fase decorreu nas três salas adjacentes ao laboratório de Telecomunicações, na qual foi montada a topologia com o sistema srsLTE associado aos USRP B210 ligados aos computadores com o sistema operativo Linux com três componentes, nomeadamente uma estação base (BS), que serviu de fonte do sinal de comunicação com um equipamento de utilizador (UE) que o recebe, e dois interferentes. Importa realçar que esta segunda fase foi dividida em duas etapas, das quais uma sem interferente para medir a potência recebida da própria estação base e outra com os interferentes mais próximo e mais afastado da sala do sinal da própria célula. O objetivo desta fase foi o de verificar o modelo de propagação do sinal de comunicação da tecnologia LTE e medir a potência recebida pelo utilizador com recurso ao Analisador de Espectro portátil FSH8 da Rohde & Schwarz capaz de medir de 10 kHz a 8 GHz, feita na frequência central de 2.625 GHz. Nas medições feitas em ambiente interior, o tamanho de cada uma das três salas é 7.32 × 7.32 metros quadrados. Embora a sala 1 seja a sala de interesse, onde ocorreram as medições teóricas e práticas, as BSs que atuam como nós interferentes também são consideradas separadamente na sala 2 ou na sala 3. Ao variar as posições de UE dentro da sala 1, foi possível verificar que os valores superiores da potência recebida ocorrem próximos à BS central. No entanto, a potência recebida não diminui repentinamente por causa do efeito do ganho reduzido no diagrama de radiação na parte traseira da antena. Além disso, foi demonstrado que existe um efeito de “atenuação da parede” comprovado pelo aumento da atenuação de trajeto entre a sala 1 e a sala 2 (ou entre a sala 2 e 3). Se considerarmos uma atenuação para cada parede de cerca de 7-9 dB, verifica-se a tendência do modelo WINNER II a 2.625 GHz para a interferência que atravessa as diversas paredes. Trabalhos futuros incluem a investigação da banda de frequência de 3.5 GHz. Já a terceira fase foi realizada nas instalações do antigo aeródromo da Covilhã, e em todas as fases servimo-nos de uma licença concedida pela Entidade Reguladora do Espectro (ICPANACOM), que permitiu realizar testes de verificação da propagação do sinal no ambiente livre na faixa de frequência dos 2.6 GHz com 2500 – 2510 MHz (UL - Uplink) e 2620 – 2630 MHz (DL - Downlink). A terceira fase ainda está a decorrer nas instalações do antigo aeródromo da Covilhã, mediante a mesma licença temporária que nos foi atribuída pelo Instituto de Comunicações de Portugal ou Autoridade Nacional de Comunicações (ICP-ANACOM) sendo esta reguladora do espectro. O objetivo é continuar a investigar o comportamento de duas inclinações no cenário UMi. Testes muito iniciais LTE-Advanced foram realizados para verificar a propagação dos dois raios (direto e refletido, com uma reflexão no asfalto) do BS implementado com o sistema USRP B210 e srsLTE, considerando uma célula urbana com um comprimento de 80 metros uma estação base interferente em 320 metros, a operar, provisoriamente, a 2500 - 2510 MHz (na ligação descendente, DL - Downlink, devido à disponibilidade de uma antena direcional específica para esta banda). Finalmente este trabalho de investigação pode ser resumidamente dividido em três categorias, nomeadamente investigação de análises teóricas e matemáticas relevantes da propagação de ondas de rádio em meios com e sem interferência significativa. Medições para verificar o comportamento do sinal de propagação da tecnologia LTE-Advanced com recursos ao analisador de espectro, simulação das antenas, fabricação e medição das características de radiação das mesmas. Assim, as antenas concebidas com bons resultados foram fabricadas nas instalações da Faculdade de Ciências no Departamento de Física da Universidade da Beira Interior, sendo de seguidas testadas e caracterizadas com o auxílio do Vector Nettwork Analyzer disponível no Laboratório de Telecomunicações do Departamento de Engenharia Eletromecânica da Universidade da Beira Interior. E, finalmente, os cálculos estatísticos que incluem o teste de normalidade de Kolmogorov-Smirnov com recurso ao software estatístico SPSS para validar os resultados obtidos seguida da construção dos gráficos no Matlab em 3D, conforme a superfície da sala

Terahertz Wireless Channels: A Holistic Survey on Measurement, Modeling, and Analysis

Terahertz (0.1-10 THz) communications are envisioned as a key technology for sixth generation (6G) wireless systems. The study of underlying THz wireless propagation channels provides the foundations for the development of reliable THz communication systems and their applications. This article provides a comprehensive overview of the study of THz wireless channels. First, the three most popular THz channel measurement methodologies, namely, frequency-domain channel measurement based on a vector network analyzer (VNA), time-domain channel measurement based on sliding correlation, and time-domain channel measurement based on THz pulses from time-domain spectroscopy (THz-TDS), are introduced and compared. Current channel measurement systems and measurement campaigns are reviewed. Then, existing channel modeling methodologies are categorized into deterministic, stochastic, and hybrid approaches. State-of-the-art THz channel models are analyzed, and the channel simulators that are based on them are introduced. Next, an in-depth review of channel characteristics in the THz band is presented. Finally, open problems and future research directions for research studies on THz wireless channels for 6G are elaborated.Comment: to appear in IEEE Communications Surveys and Tutorial