Radio Propagation Conditions Research Articles

PROPOSALS TO IMPROVE THE INFORMATION CAPABILITIES OF COASTAL-BASED RADAR STATIONS FOR SURVEILLANCE OF SURFACE AND AIR OBJECTS

Sea-based radar stations (RS) are widely used for solving the tasks of radar surveillance of surface objects (SO) and air objects (AO). The subject of the article is the mechanisms of radio wave propagation in the boundary layer of the atmosphere. The aim is to investigate the possibilities of improving the accuracy of measuring the range and radial velocity of SO and AO observed beyond the line-of-sight of coastal-based RS. Objective: to analyse the spatial and temporal parameters and properties of waveguide layers above the water surface. Methods used: maximum likelihood and frequency. The following results were obtained. The results of experimental studies of seasonal and daily changes in the parameters of the lower troposphere layer in the Black Sea coastal zone and the parameters of tropospheric radio waveguides are presented. The procedure for calculating the energy transmission losses during radio wave propagation in the boundary layer of the atmosphere is presented, and the conditions for detecting SO and AO beyond the radar line-of-sight are determined. Recommendations for increasing the range of detection of SO and AO are given, which are associated with the possibility of predicting the existence of tropospheric radio waveguides by using data on the current conditions of radio wave propagation over the sea based on the signals of the automatic ship identification system AIS. Conclusions. Proposals have been developed to improve the accuracy of measuring the range and radial velocity of SO and AO at waveguide propagation of radio waves over the sea surface. A promising area for further research may be to identify ways to optimise the measurement of angular coordinates in modern RS during waveguide propagation of radio waves over the sea surface.

Automatic Placement Algorithm of Base Stations Trunking Communication Systems

to increase the efficiency of the trunking communication systems design process, an original algorithm for the automatic placement of base stations is proposed, taking into account the real conditions of radio wave propagation. The analysis showed that the existing methods allow you to place base stations manually, with a given step or automatically, but without taking into account the propagation of radio waves, which leads to poor-quality coverage of the required area with communication. The aim of the work is to reduce the complexity of designing a trunking communication system that is guaranteed to cover a given service area. It is proposed to calculate the service areas of base stations using a statistical model, as well as taking into account additional diffraction losses on the radio signal propagation path. The solution to the problem of automatic placement of base stations is based on the use of the proposed modified Hut model, which takes into account the terrain at the locations of the base and portable stations, as well as on the international recommendation for predicting signal propagation on a specific route for ground services. With automatic placement, the optimality criterion is fulfilled, which consists in placing the minimum number of base stations necessary to cover the required territory. An element of the novelty of the presented solution is that at the first stage of the calculation, the service area of the base station is determined by the statistical method, at the second stage, an updated calculation of the service area takes place taking into account the actual conditions of radio wave propagation at the binding site, and at the third stage, the zone of guaranteed customer service is determined. The use of the proposed algorithm makes it possible to reduce the complexity of the system design process and determine the sufficient number of base stations needed to cover a given area with communication. Appropriate software has been developed to apply the algorithm in real practice. To confirm the effectiveness of the algorithm, the paper presents comparative calculations of the time spent on designing a trunking communication system using the developed software and using the widely used RadioMobile program.

Modeling of the Propagation of LF–MF–SF Bands Electromagnetic Waves on Arctic Paths

The article demonstrates that the conditions of LF–MF–SF bands electromagnetic wave propagation over the “ice-sea” structure with highly inductive impedance are more favorable than over the sea without ice because of the appearance of surface electromagnetic waves (SEW). It was determined that the conditions of radio wave propagation over ice paths depend on a frequency, ice thickness and distance from the transmitter within the 100 kHz – 5 MHz range on the paths with ice thickness from 0.6 to 2.7 meters.

Dispelling Revisionist Myths Regarding Spectrum Property Rights in the 1920s

ABSTRACT Failures to understand the constraints and incentives facing decisionmakers have resulted in the creation of the myth that property rights and spectrum markets would have been superior to the regulatory system of the Radio Act of 1927. Discussions of hypothetical spectrum property rights in the 1920s fail to take account of (1) the vast differences between the radio propagation conditions in the radio spectrum in use then and propagation in the bulk of the radio spectrum today and (2) the technical limitations of equipment at that time. The author concludes that spectrum property rights would have resulted in more radio service in urban areas, a substantial loss of rural service, and diminished consumer welfare.

Determination of radio wave propagation conditions in the atmosphere of Hanoi using the radiosonde data of balloons

This article uses radiosonde data of balloons in Hanoi to determine the radio refractive index and the conditions of radio wave propagation in the atmosphere. The research results in the three years 2016–2018 show the highest average radio refractivity, the maximum radio refractivity difference between the years. Secondly, radiosonde data are used to estimate the accuracy of global ITU models, and showed that the radio refractivity’s difference between the ITU-R model and the observed value by radiosonde method is up to 60 N-units at a lower altitude of atmosphere. In conclusion, it is recommended to use radiosonde data instead of the ITU model (where available) to obtain refractive index when studying wave propagation conditions in the atmosphere.

Method of 128-position quadrature amplitude-polarization manipulation

The functioning of modern digital communication systems tends to occur in a complex interference environment. The communication system is affected by various types of jamming: both natural noises associated with the conditions of radio waves propagation, and artificial interference concerned with electromagnetic compatibility of radio equipment, characteristics of communication channels, etc. Applied issues of enhancing digital communication systems interference insusceptibility are quite relevant at the present time. Concurrently, it is advisable to achieve an increase in interference insusceptibility by rational methods that do not require a significant increase in the emitted signals energy. The techniques based on the use of algorithms for processing special types of signals are the most promising to this date. Radio specialists address the methods for digital processing of polarization-manipulated signals which, while maintaining the communication system carrying capacity, allow us to obtain an essential gain in the parameters of the communication system interference insusceptibility. At the same time, a successful combination of these methods with the already known techniques of digital signal processing is noted. This article considers the multi-position method of quadrature amplitude-polarization manipulation (M-QAPM), where the number of positions M = 27 = 128 (128-QAPM). The modulation symbol at 128-QAPM consists of a 7-bit digital code. The purpose of this article is to describe analytically the method of 128-position quadrature amplitude-polarization manipulation when transmitting 7-bit binary modulation symbols over a communication channel. During mathematical modeling, a signal constellation was formed and visualized. The structural diagram of the modulator was given. The practical significance of the given paper lies in the fact that quadrature amplitude-polarization manipulation can be considered as a universal type of digital modulation, which can be applied instead of the currently known quadrature types of manipulation.

Toward Accurate Indoor Positioning: An RSS-Based Fusion of UWB and Machine-Learning-Enhanced WiFi.

A wide variety of sensors and devices are used in indoor positioning scenarios to improve localization accuracy and overcome harsh radio propagation conditions. The availability of these individual sensors suggests the idea of sensor fusion to achieve a more accurate solution. This work aims to address, with the goal of improving localization accuracy, the fusion of two conventional candidates for indoor positioning scenarios: Ultra Wide Band (UWB) and Wireless Fidelity (WiFi). The proposed method consists of a Machine Learning (ML)-based enhancement of WiFi measurements, environment observation, and sensor fusion. In particular, the proposed algorithm takes advantage of Received Signal Strength (RSS) values to fuse range measurements utilizing a Gaussian Process (GP). The range values are calculated using the WiFi Round Trip Time (RTT) and UWB Two Way Ranging (TWR) methods. To evaluate the performance of the proposed method, trilateration is used for positioning. Furthermore, empirical range measurements are obtained to investigate and validate the proposed approach. The results prove that UWB and WiFi, working together, can compensate for each other’s limitations and, consequently, provide a more accurate position solution.

Auroral Ionosphere Model with PC Index as an Input

Auroral Ionosphere Model (AIM-E) is designed to calculate chemical content in the high-latitude E region ionosphere and takes into account both the solar EUV radiation and the electron precipitation of magnetospheric origin. The latter is extremely important for auroral ionosphere chemistry especially in disturbed conditions. In order to maximize the AIM-E timing accuracy when simulating highly variable periods in the course of geomagnetic storms and substorms, we suggest to parameterize the OVATION-Prime empirical precipitation model with the ground-based Polar Cap (PC) index. This gives an advantage to: (1) perform ionospheric simulation with actual input, since PC index reflects the geoeffective solar wind conditions; (2) promptly assess the current geomagnetic situation, since PC index is available in real-time with 1 min resolution. The simulation results of AIM-E with OVATION-Prime (PC) demonstrate a good agreement with the ground-based incoherent scatter radar data (EISCAT UHF, Tromso) and with the vertical sounding data in the Arctic zone during events of intense particle precipitation. The model reproduces well the electron content calculated in vertical column (90–140 km) and critical frequency of sporadic E layer (fOEs) formed by precipitating electrons. The AIM-E (PC) model can be applied to monitor the sporadic E layer in real-time and in the entire high-latitude ionosphere, including the auroral and subauroral zones, which is important for predicting the conditions of radio wave propagation.

Open Source Software Radio Platform for Research on Cellular Networked UAVs: It Works!

Cellular network-connected unmanned aerial vehicles (UAVs) experience different radio propagation conditions than radio nodes on the ground. Therefore, it has become critical to investigate the performance of aerial radios, both theoretically and through field trials. In this article, we consider low-altitude aerial nodes that are served by an experimental cellular network. We provide a detailed description of the hardware and software components needed to establish a broadband wireless testbed for UAV communications research using software radios. Results show that a testbed for innovation in UAV communications and networking is feasible with commercial off-the-shelf hardware, open source software, and low-power signaling.

Determination of radio wave propagation conditions in the atmosphere of Hanoi using the meteorological data

This article uses the data of radio occultation and the radiosonde data to determine radio refractive index and wave propagation conditions in the atmosphere of the Hanoi area. The content of this article uses the data of radio occultation in 2014-2016 and the radiosonde data in 2016-2018, showing that the radio refractive index tends to decrease with altitude, the maximum average value of radio refractivity is 370 N-units, the largest radio refractivity difference between years is not more than 11 N-units, at high altitudes the radio refractivity value is close to the value at standard model of the ITU-R while at a small altitude the difference between the model value and the observed value is up to 60 N-units, the vertical gradient of refractivity and the effective earth radius coefficient is independent with altitude. Based on radio refractivity, it is possible to determine tropospheric delay, which is input data for problems such as satellite positioning, altimetry satellite and under-the-horizon radar.

Intelligent Omni-Surfaces: Ubiquitous Wireless Transmission by Reflective-Refractive Metasurfaces

Intelligent reflecting surfaces (IRSs), which are capable of adjusting radio propagation conditions by controlling the phase shifts of the waves that impinge on the surface, have been widely analyzed for enhancing the performance of wireless systems. However, the reflective properties of widely studied IRSs restrict the service coverage to only one side of the surface. In this paper, to extend the wireless coverage of communication systems, we introduce the concept of intelligent omni-surface (IOS)-assisted communication. More precisely, an IOS is an important instance of a reconfigurable intelligent surface (RIS) that can provide service coverage to mobile users (MUs) in a reflective and a refractive manner. We consider a downlink IOS-assisted communication system, where a multi-antenna small base station (SBS) and an IOS jointly perform beamforming, for improving the received power of multiple MUs on both sides of the IOS, through different reflective/refractive channels. To maximize the sum-rate, we formulate a joint IOS phase shift design and SBS beamforming optimization problem, and propose an iterative algorithm to efficiently solve the resulting non-convex program. Both theoretical analysis and simulation results show that an IOS significantly extends the service coverage of the SBS when compared to an IRS.

Characteristics of the electromagnetic environment created by radiations of user equipment of ...4G/5G/6G cellular (mobile) communications in buildings

The goal of the work is to substantiate the technique for assessing the intensity of electromagnetic background generated by the set of radiating user devices of mobile communications in multi-storey buildings. For known empirical models of radio wave propagation in buildings, expressions are obtained for the probability distribution density and expectation of the power flux density of electromagnetic fields generated inside building by these sources from various parts of the building's interior space: from the near zone with radio wave propagation conditions similar to free space; and from the far zone, for which, along with intense attenuation of radio waves due to internal obstacles, a «quasi-waveguide» propagation of radio waves along corridors and industrial premises is also possible in certain directions. Relationships are obtained for the average levels of individual components of the electromagnetic background, determined as scalar sums of power flux density values of the fields generated by the sets of radiating devices of both the near zone and the far zone as a whole or its individual parts, characterized by different conditions of radio wave propagation. A method is proposed for assessing the electromagnetic background inside buildings based on approximation of sections of the inner surface of the premises in which the observation point is located, and the outer surface of the building, in the inner space of which radiation sources are randomly distributed, by the corresponding sections of the inner and outer spherical surfaces that are the subtend areas of the corresponding solid angles, in space elements of which a different spatial densities and radiation powers of sources and different conditions of radio wave propagation are possible. The results can be used to analyze the electromagnetic ecology of habitat and the electromagnetic safety of population at the full-scale implementation of 4G/5G/6G mobile communications, as well as to analyze the electromagnetic compatibility of systems using frequency bands for mobile communications on a primary and secondary basis.

Dispelling Revisionist Myths Regarding Spectrum Property Rights in the 1920s

When assessing legislation and policies of the past, one must analyze the context in which they were developed. Failure to understand the past and the path to the present may lead to misunderstanding a regulatory agency’s structure and values. Such failures to understand the past have resulted in assertions that property rights and spectrum markets would have been superior to the regulatory system of the Radio Act of 1927. The author explores the relative efficiency implications of Federal Radio Commission regulation under the Radio Act of 1927 and a system of spectrum property rights. He observes that discussions of hypothetical spectrum property rights in the 1920s fail to take into account (1) the vast differences between the radio propagation conditions in the radio spectrum in use then and propagation in the bulk of the radio spectrum today and (2) the technical limitations of equipment at that time. Propagation conditions in the AM band make interference a diffuse problem. A single radio transmitter could impair the reception of dozens to hundreds of other stations; consequently, market transactions would have had to involve many parties. Hypothetical property rights systems also fail to consider directly the utility of the listening audience—the group responsible for more than 90% of the investment in the AM radio broadcasting system. The author concludes that spectrum property rights would have resulted in more radio service in urban areas, substantial loss of rural service, and diminished consumer welfare.

Моделювання робочої зони локальної RTLS-системи району надзвичайної ситуації

A mathematical model of a differential-rangefinder local positioning system has been developed, which in real time makes it possible to predict the working area of the system, taking into account the construction barriers of the emergency zone. The conditions of propagation of high-frequency signals, which determine the quality of positioning and the accuracy characteristics of the system, are taken into account. To simplify the simulation, a number of assumptions were made regarding the parameters of the obstacles and the conditions of radio wave propagation, which make it possible to simplify the prediction process. On the basis of the geometric criterion and the criterion of maximum removal, a modified geometry coefficient (zone coefficient) was obtained, which is proposed to be used as the basis for a mathematical forecasting model. Using this criterion, a computational algorithm and a program for operational forecasting of the working area of local positioning have been developed, which make it possible to take into account the influence of the number of beacons, the geometry of the system and the location of building barriers to the propagation of radio signals on the shape of the working area. In the process of modeling, both geometric and general physical laws of the formation of the field of radio navigation support were taken into account. A study of the operation of the modeling system was carried out in the presence of several radio beacons, in the absence and in the presence of several construction barriers within the emergency zone. The developed mathematical model makes it possible to calculate the size of the positioning zones with the determination of the boundary conditions for the reliability and accuracy of the navigation support of rescuers. Taking into account the process of predicting the impact of obstacles in the emergency zone on the type and size of the working area of the positioning system allows the head of emergency response to make the right management decision, ensure safe working conditions for rescuers and optimize emergency response.

Uplink Energy Efficiency Distribution With Aerial Users in Cellular Networks

The power consumption of future user equipments (UEs) will be affected by the projected growth in their computing capacity, while data throughput may be affected by emerging aerial UEs with specific radio propagation conditions compared to terrestrial UEs. In such a context, this letter evaluates a key metric of interest, namely the probability that the uplink energy efficiency (EE) at a typical ground base station will be higher than a predefined threshold. We first characterize the priority bias of each UE layer as a function of long-term shadowing and system-level parameters to assess its penetration rate, i.e., the amount of active UEs from each tier among the total population of active UEs. Next, tractable approximations of the desired signal and the interference distribution are performed, enabling to derive the uplink EE. Our results demonstrate that an aggregation of the system-level parameters through the aerial priority bias needs to meet a given constraint to mitigate interference from aerial UEs and enhance the uplink EE of ground UEs. Monte-Carlo simulations validate the accuracy of our analytical results.

A Review on the Effects of Radio Refractivity and Atmospheric Parameters on Signal Quality at Ultra High Frequency (UHF)

Refractivity is an important factor in predicting the performance of radio link. The structures of the refractive index of the troposphere are responsible for many complicated mechanisms such as, multipath effects, absorption, scattering of radio signals, etc. and these mechanisms can cause a lot of propagation impairment such as, loss of signal for mobile communication, the accuracy of tracking radio source (such as stars) with radio telescopes, radar system etc. Understanding the effects of the weather on radio wave propagation will help to improve the quality of radio signals, as the Weather variables are useful ingredients in the predictions of refractivity distributions and the anomalous radio wave propagation conditions of the atmosphere. This study contends that refractivity variations significantly affects received signal strength at Ultra High Frequency (UHF) and gave a brief theoretical background on Electromagnetic wave, Atmospheric effects on radio propagation anomalous propagation condition and the mathematical expression for refractive index and refractivity of the troposphere. Also, the paper review related articles in the following area; refractive index and refractivity of the troposphere, effects of weather variables and refractivity of troposphere. The analysis of the review articles summits that, refractivity reveals seasonal variations with high value in rainy season and low values in dry season. Also observed from the review articles, is that the diurnal variations are influenced by three atmospheric parameters; water vapour has the greatest effect on refractivity variations followed by temperature and pressure. Furthermore, the Refractivity is function of local meteorological parameters. Eventually, the study suggests that, the effect of Atmospheric parameters and consequently the Radio Refractivity should be compensated for when designing wireless communication links in an environment.

Performance Analysis of 5G Fixed Wireless Access Networks with Antenna Diversity Techniques

An increase in the network interconnection has been observed across the world because of multimedia applications and services transmission over the Internet. Nonetheless, a huge number of homes are still experiencing irregular or no broadband connections. Fixed wireless access (FWA) offers an attractive wireless solution for offering multimedia services to various homes compared with fixed-line broadband solutions. However, matching the performance levels of the fixed-line broadband is comparatively demanding for the current access networks. Compared with the fourth-generation (4G) networks, the fifth-generation (5G) technological implementation in FWA is envisioned to give significant enhancements regarding the system capacity, coverage, and connectivity at low-latency. To fulfill the network requirements, 5G systems are anticipated to exploit higher frequency bands. However, radio propagation conditions at higher frequency bands are relatively demanding, owing to the path-loss (PL). In this paper, we discuss different network requirements of the 5G FWA system. Also, a comprehensive overview of the broadband schemes’ technical challenges is presented and we proffer viable solutions for achieving cost-effective and scalable 5G FWA solutions. Moreover, we exploit diversity scheme and present a closed-form expression for the multiple-input, multiple-output scheme in which the PL and beamforming schemes are considered. The accuracy of the proposed closed-form expression is validated by Monte-Carlo simulation over different antenna configurations and signal-to-noise ratios. Based on the presented models, we evaluate and simulate the PL and average transmission rates for different use cases. Simulation results show significant performance improvement compared with a single-input single-output configuration. Apart from being capable of enhancing system performance, the proposed model can be employed for an arbitrary number of transmit and receive antennas. The model is anticipated to pave the way for more robust performance evaluation of multi-antenna-based 5G use cases.

Maximum usable frequency and skip distance maps over Italy

Since 1988 the Upper Atmosphere Physics unit of the Istituto Nazionale di Geofisica e Vulcanologia (INGV) has provided maps of Maximum Usable Frequency (MUF) and skip distance over a European area extending in latitude from 34°N to 60°N and in longitude from 5°W to 40°E. Anyhow, these maps suffer the following restrictions: (1) they are provided with two months in advance and so they are not suitable for space weather purposes; (2) they are represented with few isolines; (3) they are centred only on Rome (41.8°N, 12.5°E) and generated in black and white; (4) MUF are calculated with a really simple algorithm. In order to overcome these restrictions, a new software tool was developed to get climatological maps (up to three months in advance) and quasi real-time maps, (nowcasting) limited to the sector extending in latitude from 34°N to 48°N and in longitude from 5°E to 20°E, which includes the whole Italian territory. In order to achieve a greater accuracy, MUF and skip distance maps are generated combining the Simplified Ionospheric Regional Model (SIRM) and its UPdated version (SIRMUP) with the Lockwood algorithm. Climatological maps are generated every hour on the basis of the predicted 12-months smoothed sunspots number. Nowcasting maps are generated every 15 min exploiting foF2 and M(3000)F2 data autoscaled at the ionospheric stations of Rome and Gibilmanna (37.6°N, 14.0°E). Nowcasting maps constitute the most important novelty because they let High Frequency (HF) users know in quasi real-time the radio propagation conditions over Italy. This turns out to be very valuable in terms of reliable radio links, especially in case of adverse space weather events.

МАТЕМАТИЧНА МОДЕЛЬ ФОРМУВАННЯ СИГНАЛІВ З АДАПТАЦІЄЮ ПО ШВИДКОСТІ ПЕРЕДАВАННЯ ІНФОРМАЦІЇ НА ОСНОВІ ДОСКОНАЛИХ ДВІЙКОВИХ МАТРИЦЬ

Предметом дослідження є методи та моделі формування сигналів адаптивних видів модуляції. Мета: забезпечення високої пропускної здатності та спектральної ефективності, для даних умов розповсюдження радіохвиль, шляхом використання запропонованої моделі формування сигналів з адаптацією по швидкості передавання інформації на основі досконалих двійкових матриць. Результати досліджень. В роботі представлено результати аналізу напрямів розвитку та основних властивостей безпроводових мереж передачі даних. Встановлено, що лише у разі забезпечення комплексу розглянутих властивостей, безпроводова мережа може виконувати своє функціональне призначення – забезпечувати доставляння повідомлень у необхідному обсязі й із заданою якістю. Розглянуто принципи реалізації методів адаптивної модуляції в перспективних засобах бездротового зв’язку. Використання адаптивної модуляції дозволяє забезпечити найкращу пропускну здатність для даних умов розповсюдження радіохвиль, розглянута в роботі схема адаптивної модуляції дозволить звести ймовірність виникнення помилки в передачі до мінімуму. Запропоновано математичну модель формування сигналів з адаптацією по швидкості передавання інформації на основі досконалих двійкових матриць. Розглянуто основні принципи функціонування пристрою управління моделі формування сигналів з адаптацією по швидкості передавання інформації на основі досконалих двійкових матриць. Висновки та область застосування результатів досліджень. Запропонована математична модель формування сигналів з адаптацією по швидкості передавання інформації на основі досконалих двійкових матриць. Використання запропонованих сигналів з адаптацією по швидкості передавання інформації на основі досконалих двійкових матриць дозволить забезпечити високу пропускну здатність та спектральну ефективність, для даних умов розповсюдження радіохвиль, перспективних радіоінтерфейсів

Implementation of an Interactive Environment With Multilevel Wireless Links for Distributed Botanical Garden in University Campus

In this contribution, an end to end system to enable user interaction with a distributed botanical university campus garden is designed, implemented and tested. The proposed system employs different wireless links to collect data related to different bio physiological parameters of both the vegetation mass and the surrounding environment. Detailed analysis of these multilevel communication links is performed by using deterministic volumetric wireless channel estimation and considering underground, near ground and over ground radio propagation conditions. An in-house developed technique enables accurate wireless channel characterization for complete campus scenario considering the multiple link types and all its composing elements. Node definition and network topology is thus obtained by wireless channel analysis of over ground, near ground and underground communication for both 868 MHz and 2.4 GHz Wireless Sensor Networks in an inhomogeneous vegetation environment. Connectivity to enable user interaction as well as for telemetry and tele-control purposes within the campus is achieved by combining ZigBee and LoRaWAN transceivers with the corresponding sensor/actuator platforms. Coverage studies have been performed in order to assess communication capabilities in the set of multiple underground/near ground/over ground links, by means of deterministic channel analysis for the complete university campus location. Measurement results in lab environment as well as full system deployment are presented, showing good agreement with deterministic simulations. Moreover, system level tests have been performed over a physical campus cloud, providing adequate quality of experience metrics. The proposed solution is a scalable system that provides real time trees status monitoring by a cloud-based platform, enabling user interaction within a distributed botanical garden environment in the university campus.