M-Class Solar Flares in Solar Cycles 23 and 24: Properties and Space Weather Relevance

A comprehensive statistical analysis on the properties and accompanied phenomena of all M-class solar flares (as measured in soft X-rays) in the last two solar cycles (1996–2019) is presented here with a focus on their space weather potential. The information about the parent active region and the underlying sunspot (Hale) type is collected for each case, where possible, in order to identify photospheric precondition as precursors for the solar flare eruption or confinement. Associations with coronal mass ejections, solar energetic particles, and interplanetary radio emissions are also evaluated and discussed as possible proxies for flare eruption and subsequent space weather relevance. The results show that the majority (∼80%) of the analyzed M-class flares are of β, β-γ, and β-γ-δ magnetic field configuration. The M-class population of flares is accompanied by CMEs in 41% of the cases and about half of the flare sample has been associated with radio emission from electron beams. A much lower association (≲10%) is obtained with shock wave radio signatures and energetic particles. Furthermore, a parametric scheme is proposed in terms of occurrence rates between M-class flares and a variety of accompanied solar phenomena as a function of flare sub-classes or magnetic type. This study confirms the well-known reduced but inevitable space weather importance of M-class flares.

A Monte Carlo Analysis of Actual Maximum Exposure From a 5G Millimeter-Wave Base Station Antenna for EMF Compliance Assessments

International radio frequency (RF) electromagnetic field (EMF) exposure assessment standards and regulatory bodies have developed methods and specified requirements to assess the actual maximum RF EMF exposure from radio base stations enabling massive multiple-input multiple-output (MIMO) and beamforming. Such techniques are based on the applications of power reduction factors (PRFs), which lead to more realistic, albeit conservative, exposure assessments. In this study, the actual maximum EMF exposure and the corresponding PRFs are computed for a millimeter-wave radio base station array antenna. The computed incident power densities based on near-field and far-field approaches are derived using a Monte Carlo analysis. The results show that the actual maximum exposure is well below the theoretical maximum, and the PRFs similar to those applicable for massive MIMO radio base stations operating below 6 GHz are also applicable for millimeter-wave frequencies. Despite the very low power levels that currently characterize millimeter-wave radio base stations, using the far-field approach can also guarantee the conservativeness of the PRFs used to assess the actual maximum exposure close to the antenna.

Матричное радиовидение на основе гетеродинного приема с применением радиолокации непрерывным излучением

A new approach to the creation of millimeter-wave radio imaging systems is proposed. This approach is based on the use of an array receiver consisting of a densely packed (pixel size - 4 mm) array of planar mixers located in the focal plane of a quasi-optical objective, with application of the frequency-modulated continuous-wave radar technique. It has been demonstrated that the implementation of the heterodyne type of reception makes it possible to increase the distance range of the array radio imaging system up to ~ 100 m while maintaining the angular resolution at the previous level.

Resource Management in Converged Optical and Millimeter Wave Radio Networks: A Review

Three convergent processes are likely to shape the future of the internet beyond-5G: The convergence of optical and millimeter wave radio networks to boost mobile internet capacity, the convergence of machine learning solutions and communication technologies, and the convergence of virtualized and programmable network management mechanisms towards fully integrated autonomic network resource management. The integration of network virtualization technologies creates the incentive to customize and dynamically manage the resources of a network, making network functions, and storage capabilities at the edge key resources similar to the available bandwidth in network communication channels. Aiming to understand the relationship between resource management, virtualization, and the dense 5G access and fronthaul with an emphasis on converged radio and optical communications, this article presents a review of how resource management solutions have dealt with optimizing millimeter wave radio and optical resources from an autonomic network management perspective. A research agenda is also proposed by identifying current state-of-the-art solutions and the need to shift all the convergent issues towards building an advanced resource management mechanism for beyond-5G.

MACHINE LEARNING IN THE PROBLEM OF FORECASTING THE TIME SERIES OF MUF OF SHORT-WAVE RADIO CHANNELS

The article is devoted to the creation of an algorithm for long-term prediction of the values of the MPR. The paper analyzes the influence of various methods of processing raw values of the maximum applicable frequency on the results of machine learning algorithms, such as linear regression and XGBoost. As processing techniques, the Savitsky -Goley filtration method and the isolated forest algorithm were used to determine emissions for the daily course of the MPR.

DESIGNING A MIMO ANTENNA ARRAY FOR 5G NETWORKS

Рассматривается антенная система для сетей пятого поколения частот 37 ГГц (миллиметровый диапазон радиоволн). Предлагается установка антенны на задней стенке устройства, а излучение радиоволн происходит через стеклянную заднюю панель устройства. Для функционирования в сетях пятого поколения была разработана MIMO антенная решетка, которая состоит из четырех элементов и способна функционировать в «умном» режиме. Благодаря этому возможно формирование луча в антенной системе (beamforming). Для анализа характеристик антенной системы были получены коэффициенты корреляции огибающей, диаграммы направленности, картины электрических полей, получены зависимости эффективной изотропно излучаемой мощности (EIRP), построены графики кумулятивных функций распределения EIRP в линейном и логарифмическом масштабе. Для определения влияния излучения на человека были построены картины удельного коэффициента поглощения (SAR) в соответствии с европейскими нормами на 10 грамм тканей. Все полученные результаты показывают высокую эффективность разработанной конструкции антенной решетки для сетей пятого поколения. Антенные элементы обладают малой взаимной корреляцией, позволяют обеспечить формирование луча, кумулятивные функции распределения показывают высокий уровень покрытия сферы эффективной изотропно излучаемой мощности радиоволнами. Также было показано, что разработанная антенная система обладает малым уровнем удельного коэффициента поглощения, что доказывает безопасность сетей пятого поколения миллиметрового диапазона радиоволн. Развитие современных систем связи позволяет достичь высокой безопасности и эффективности при получении информации The article discusses an antenna system for networks of the fifth generation of 37 GHz frequencies (millimeter-wave radio waves). We propose to install the antenna on the rear wall of the device, radio waves are emitted through the glass rear panel of the device. For functioning in networks of the fifth generation, a MIMO antenna array was developed, which consists of four elements and is capable of functioning in a "smart" mode. This makes it possible to form a beam in the antenna system (beamforming). To analyze the characteristics of the antenna system, we obtained the correlation coefficients of the envelope, directional patterns, patterns of electric fields, the dependences of the effective isotropically radiated power (EIRP), and we plotted the graphs of the cumulative distribution functions of EIRP on a linear and logarithmic scale. To determine the effect of radiation on a person, we built pictures of the specific absorption rate (SAR) in accordance with European standards for 10 grams of tissue. All the results obtained show the high efficiency of the developed design of the antenna array for fifth generation networks. Antenna elements have low cross-correlation, allow for beam formation, cumulative distribution functions show a high level of coverage of the sphere of effective isotropically radiated power by radio waves. We also show that the developed antenna system has a low level of specific absorption coefficient, which proves the safety of fifth-generation networks of millimeter-wave radio waves. The development of modern communication systems makes it possible to achieve high security and efficiency in obtaining information

Performance optimization of RSOA based mm-wave radio-over-fibre access network

In this paper, a Reflective Semiconductor Optical Amplifier based, Radio-over-Fibre access network configuration has been proposed to feed future millimeter-wave radio systems. The system architecture combines several approaches to overcome the challenges of millimeter-wave signal transmission. Reflective semiconductor optical amplifier modulator realizes a colorless and relatively cost-effective Remote Antenna Unit. The same optical carrier is used for both downlink and uplink. Optical single-sideband modulation is used at the downlink, which is robust against chromatic dispersion, but the complex realization of this modulation format is not possible at the Remote Antenna Unit. Optical intermediate frequency transmission is applied at the uplink direction, and the required local oscillator signal originates from the central station. The critical element is the reflective optical amplifier, as it compensates for the optical loss and works as an external intensity modulator. The operation of the reflective optical amplifier is modeled by multisection rate and wave equation-based description. The amplification and modulation behaviors of an available reflective optical amplifier are also measured. The experimental work validated the colorless operation and the quality of the modulation versus bias current and input optical power. Finally, system simulation was realized. The uplink and downlink power budgets were balanced, and optimal values for the optical coupling rate and RSOA bias current have been selected.