Ionospheric Communication Research Articles

Capacity and Reliability of Ionosphere Communication Channel Based on Multi-Carrier Modulation Technique and LUF-MUF Variation

Capacity and Reliability of Ionosphere Communication Channel Based on Multi-Carrier Modulation Technique and LUF-MUF Variation

Loop Antenna UAV for Ionospheric Communication

Loop Antenna UAV for Ionospheric Communication

Development of a Regional F‐Region Critical Frequency Model for Southern Africa

AbstractA new localized linear regression model, called the SANSA model, is presented. The model provides a forecast of the F‐region critical frequency (foF2) over Grahamstown, South Africa (33.31°S, 26.52°E). The input parameters of this model are the maximum daily solar elevation angle, the F10.7 cm radio flux index and the planetary K index. The output parameter is the forecasted foF2. The historical data‐set consists of ionosonde foF2 observations made in Grahamstown for the period 2010–2019. The historical and predicted data sets used to develop the model are obtained from databases maintained by the South African National Space Agency, the National Aeronautics and Space Administration and the National Oceanic and Atmospheric Administration. The model improves on the results of the Ionospheric Communications Enhanced Profile Analysis and Circuit Prediction Program in terms of the root mean square error skill score metric. The work presented shows that a linear regression model based on the solar elevation angle as well as the F10.7 and planetary K indices can closely approximate observed foF2 magnitudes during quiet and storm times.

Design a radio receiver for solar activity observation in VLF band

Solar activity monitoring is important in our life because of its direct or indirect influence on our life, not only on ionospheric communications. To study solar activity, researchers need measuring and monitoring instruments, these instruments are mostly expensive and are not available in all universities. In this paper, a very low frequency radio receiver had been designed and implemented with components available in most markets to support the researchers, college students, and radio astronomy amateurs with a minimum input voltage less than 100µV, an output voltage less than 135 m V with no distortion and an overall gain of 34dB. A comparison had been done between two circuit structures using a workbench software program and experimentally done in the lab. Two antennas were experimentally tested and a loop antenna was chosen. The whole system was connected and tested to receive signals in the Lab and monitored on computer using HDSDR software program. Another experiment done outside the lab (at home), and the result was not good because of many high level interference noises.

Coronal mass ejections and high-speed solar wind streams effect on HF ionospheric communication channel

This article analyzes the degree of solar coronal mass ejections and high-speed solar wind streams influence on the ionospheric communication channel in the short-wavelength range. Regularities in the coronal mass ejections influence on the parameters of the ionosphere are revealed. It is shown that there is a decrease in the values of the used differential parameter of critical frequency of the ionosphere F2 layer after the onset of coronal mass ejections of the loop type, while no significant changes are observed from other types of coronal mass ejections. The contribution of the high-speed solar wind flux to the features of the behavior of ionospheric parameters is demonstrated. Deviations of critical frequency and maximum observed frequency of the ionosphere F2 layer indicate a change in conditions in the ionosphere, leading to disruption of radio communication in the short-wavelength range. The results of ground-based measurements of the ionospheric plasma parameters were obtained by the methods of oblique and vertical sounding of the ionosphere. The use of the method of oblique sounding made it possible to obtain data on the state of the ionosphere where there are no vertical sounding stations.

SC-FDE Layer for Sensor Networks in Remote Areas Using NVIS Communications

Despite high costs and lengthy deployments, satellite communications have traditionally been used to provide coverage in remote areas. However, given the fact that there is no radio infrastructure available in these areas, Near Vertical Incidence Skywave (NVIS) technology has positioned itself as an attractive alternative to communicate with low-power nodes in remote areas. This type of communication works in the HF frequency range complying with STANAG and MIL-STD standards, which define a physical layer for scenarios that differ from NVIS and low-power communication. The purpose of this paper was to present the definition of a new communication physical layer based on single-carrier frequency-domain equalization (SC-FDE) based on these standards but adapted to the ionospheric communication channel. This physical layer was compared to an OFDM-based layer from a previous study. The experiments performed show that this new approach achieves better results than OFDM in terms of a higher signal quality with a higher specific BER probability. Finally, this layer was also used in the theoretical design of an NVIS gateway to link sensor network devices spanning large-scale remote areas in a secure manner in the context of ubiquitous sensor networks (USN).

High‐Frequency Communications Response to Solar Activity in September 2017 as Observed by Amateur Radio Networks

AbstractNumerous solar flares and coronal mass ejection‐induced interplanetary shocks associated with solar active region AR12673 caused disturbances to terrestrial high‐frequency (HF, 3–30 MHz) radio communications from 4–14 September 2017. Simultaneously, Hurricanes Irma and Jose caused significant damage to the Caribbean Islands and parts of Florida. The coincidental timing of both the space weather activity and hurricanes was unfortunate, as HF radio was needed for emergency communications. This paper presents the response of HF amateur radio propagation as observed by the Reverse Beacon Network and the Weak Signal Propagation Reporting Network to the space weather events of that period. Distributed data coverage from these dense sources provided a unique mix of global and regional coverage of ionospheric response and recovery that revealed several features of storm time HF propagation dynamics. X‐class flares on 6, 7, and 10 September caused acute radio blackouts during the day in the Caribbean with recovery times of tens of minutes to hours, based on the decay time of the flare. A severe geomagnetic storm with Kpmax = 8+ and SYM‐Hmin = −146 nT occurring 7–10 September wiped out ionospheric communications first on 14 MHz and then on 7 MHz starting at ∼1200 UT 8 September. This storm, combined with affects from additional flare and geomagnetic activity, contributed to a significant suppression of effective HF propagation bands both globally and in the Caribbean for a period of 12 to 15 days.

МАТЕМАТИЧЕСКОЕ МОДЕЛИРОВАНИЕ ФЛУКТУАЦИЙ ДОПЛЕРОВСКОГО СДВИГА ЧАСТОТЫ ДЕКАМЕТРОВОГО РАДИОСИГНАЛА В ИОНОСФЕРНОМ КАНАЛЕ СВЯЗИ

МАТЕМАТИЧЕСКОЕ МОДЕЛИРОВАНИЕ ФЛУКТУАЦИЙ ДОПЛЕРОВСКОГО СДВИГА ЧАСТОТЫ ДЕКАМЕТРОВОГО РАДИОСИГНАЛА В ИОНОСФЕРНОМ КАНАЛЕ СВЯЗИ

Computer filtering of images of ionograms of HF ionospheric radio communication paths and an algorithm for determining signal-to-noise ratio

Computer filtering of images of ionograms of HF ionospheric radio communication paths and an algorithm for determining signal-to-noise ratio

Ionosphere and radio communication

The Earth’s ionosphere consists of plasma produced by the photoionization of thin upper atmospheric gases by UV rays and photons of short wavelength from the sun. The upper ionosphere is used for radio communication and navigation as it re-ects long, medium, as well as short radio waves. Since solar radiation is the main cause of the existence of ionosphere, any variation in the radiations can affect the entire radio communication system. This article attempts to brie-y introduce the readers to the study of ionosphere in the context of its use as a radio re-ector, with particular reference to India.

Software-defined radio technology in the problem concerning with the successive sounding of HF ionospheric communication channels

The problem concerning new software-defined radio technology is investigated as applied to the successive sounding of HF ionospheric communication radio channels. The algorithm for quadrature processing of chirp signals subjected to elementwise compression in the frequency domain is developed. It is established that a channel scattering function and a delay power profile are related to a compressed-signal spectrum and their basic parameters. Data on the key characteristic of HF communications modems are presented. The efficiencies of different modems are estimated using the experimental data on channel parameters. It is demonstrated that the aforementioned technology can be used to estimate not only HF communication channel parameters from the pass band of a radio line but also select the optimal one and, furthermore, makes it possible to combine communications and radio sounding systems in the single device.

CLASSIFICATION OF FACTORS DETERMINING THE SW RADIOWAVES PROPAGATING VIA IONOSPHERIC PATHS

The paper deals with classification of factors determining propagation SW band radio waves via ionospheric paths. Regular characteristics of the ionospheric communication channel have been identified in SW band. The necessity was demonstrated for recording passive noise interferences associated with the exposure of spatially inhomogeneous, magnetically active, dispersing, absorbing, changing in time ionosphere on structure of the emitted useful signal.

Comparison of observed and predicted MUF(3000)F2 in the polar cap region

The maximum usable frequency for a 3000 km range circuit (MUF(3000)F2), computed from ionosonde measurements at Resolute (74.75∘N, 265.00∘E) and Pond Inlet (72.69∘N, 282.04∘E), has been compared with values obtained from the Ionospheric Communications Enhanced Profile Analysis and Circuit Prediction Program (ICEPAC), Voice of America Coverage Analysis Program (VOACAP), and International Telecommunication Union Recommendation 533 (REC533) models over a 4 year period. Predictions and observations show diurnal and seasonal variations; however, the VOACAP and ICEPAC models fail to reproduce the diurnal variation trend observed in the measurements during the summer period. The performance of these models has been statistically analysed: REC533 gives a better performance in winter and equinox months, while VOACAP has a better performance for both equinox and summer months. ICEPAC shows poor performance during low solar activity.

Spread spectrum high performance techniques for a long haul high frequency link

Skywave ionospheric communication systems offer a good choice to satellite communications when transmitting from the poles. For the last 10 years the authors have been sounding and testing modulations through a 12 700 km high frequency link from the Spanish Antarctic Station to Spain. Previous tests comparing direct sequence spread spectrum (DS-SS) and orthogonal frequency division multiplexing (OFDM) showed that spread spectrum bit rate error (BER) results outperformed OFDM at the expense of lower bit rates. In this study the authors present three spread spectrum techniques for this long haul link that increase the bit rate and the spectral efficiency of the direct sequence while keeping the good BER performance obtained. Tests have been performed with several symbol periods as well as different bandwidth for each technique, hence the authors can conclude which combination best suits this channel.

Single‐carrier frequency domain equalisation proposal for very long haul HF radio links

A single carrier frequency domain equalisation (SC-FDE) modulation scheme which represents a step forward in the investigation since it obtains higher bit rates than previous proposals with spread spectrum techniques is presented. The focus of this reported work is the data transmission from remote sensors using very low-power HF ionospheric communications. In particular, the authors' research group has been studying the ionospheric channel parameters and data transmission techniques from Antarctica since 2003. Both, the spread spectrum and multicarrier modulations have been tested previously in order to obtain a good trade-off between bit error rate and bit rate. A proof of principle of the single carrier technique with promising results is presented.

STATISTICAL CHARACTERISTICS OF THE MULTI-PATH TIME DELAY AND DOPPLER SHIFT OF A RADAR WAVE PROPAGATING THROUGH THE IONOSPHERE

Multi-path time delay spread is a very important factor in the bit error rate of high-frequency ionospheric communication channels and in the target detection performance of over-the-horizon radars. In this study, the probability density distribution of multi-path time delay and Doppler shift of ionospheric radio signal are derived using Rayleigh fading. Moreover, the probability density distribution of time delay, average power of the received signal, and received signal variance are discussed in detail. Using a designed experimental circuit, the measured value of the multi-path time delay spread is obtained from three given radio paths by the sweep-frequency pulse sounding technique. The average value of the multi-path time delay spread that changes with the ratio K, which is the operating frequency of the basic maximum usable frequency, is also analyzed and fltted using the least-squares fltting method. Theoretical and statistical research shows that for a given radio path and speciflc frequency, the multi-path time delay spread approximately follows a normal distribution. The average time delay spread decreases with the increase in the ratio K; however, it eventually approaches a steady value. The results of this research provide an empirical reference for further prediction and estimation of the time delay spread of a radar wave propagating through the ionosphere.

A comprehensive sounding of the ionospheric HF radio link from Antarctica to Spain

Since 2003, our group has been investigating the performance of different transmission techniques for low‐power low‐interference High Frequency (HF) ionospheric communication systems. Specifically, we have focused on the link between the Spanish Antarctic Station (SAS) Juan Carlos I in Livingston Island and Ebro Observatory (OE) in Spain, in order to transmit the data gathered from some geomagnetic sensors. These transmission techniques require a valuable knowledge of the channel behavior, thus a comprehensive narrowband and wideband sounding of the ionospheric channel is needed. Some significant improvements both in the system and in the signal processing have been done to achieve this goal. The analysis time and the frequency band have been extended to 24 hours per day and to the whole HF band (2‐30 MHz). Moreover, new measurements of the absolute propagation time and the Doppler frequency shift are introduced. In this paper, the sounding results obtained using the new system are presented.

Modification of the Watterson model of the ionospheric HF radio communication channel for adaptive spaced reception

We propose a model for the formation of signals from spaced antennas to be used as simulated ionospheric high-frequency radio channels for testing of algorithms and devices with spatiotemporal signal processing. Adequacy of the proposed model is demonstrated by its comparison with the experimental results. The model is used to determine potential capabilities of the spatial compensators of interference in a channel with scattering.

A New Theoretical Approach of Wavelet-Based Multifractal Characterization of HF Channel Scattering Function: Theoretical and Physical Interpretations

In high-frequency (HF) ionospheric communications, the dynamic nature of the high-latitude ionosphere creates small-scale ionospheric irregularities capable of scattering HF radio waves. In addition, there are large-scale irregularities which may be identified using some specific methods. However, small-scale irregularities cannot be easily identified and characterized. The aim of this paper is to introduce a new wavelet-based multifractal dimension mapping approach for the identification and the quantification of the small-scale irregularities. Numerical results show the improvement of the proposed methods compared to those obtained by the classical Legendre multifractal analysis. In our analysis, we have used the scattering function as a tool for the HF channel characterization. Our analysis deals with experimental scattering functions measured during the solar eclipse on August 11, 1999.

An attempt to validate HF propagation prediction conditions over Sub‐Saharan Africa

Ionospheric behavior plays an important role in high‐frequency (HF) radio propagation, which subsequently provides an opportunity for studying ionospheric variability and space weather effects. The continuous change in ionospheric conditions caused by space weather strongly affects HF propagation. The use of HF communication is still very relevant over the African continent, as seen by the requirements for services provided by the Regional Warning Center for Space Weather in Africa, and this has necessitated an investigation into the prediction capabilities of the existing HF propagation models currently used over this region. This paper presents the validation of HF propagation conditions through the ionosphere by using the Ionospheric Communication Enhanced Profile Analysis and Circuit (ICEPAC) model with real‐time data from international beacons located in Africa. The HF propagation results presented are for the circuits Ruaraka (5Z4B), Kenya (1.24°S, 36.88°E), and Pretoria (ZS6DN), South Africa (25.45°S, 28.10°E) to Hermanus (ZS1HMO), South Africa (34.27°S, 19.12°E). The potential of this model as compared to real‐time data in terms of propagation condition predictions is illustrated. An attempt to draw conclusions for the future improvement of HF propagation models is also presented. Results show that ICEPAC performs better for the 5Z4B‐ZS1HMO than for the ZS6DN‐ZS1HMO circuit, although it does, in general, provide a low‐accuracy prediction compared to the real‐time data. Thus certain parameters need to be investigated further for future improvement in the performance of the ICEPAC model over Africa.