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Review
. 2020 Apr 28;20(9):2486.
doi: 10.3390/s20092486.

Ionospheric Narrowband and Wideband HF Soundings for Communications Purposes: A Review

Marcos Hervás  1 , Pau Bergadà  1   2 , Rosa Ma Alsina-Pagès  1
Affiliations
Review

Ionospheric Narrowband and Wideband HF Soundings for Communications Purposes: A Review

Marcos Hervás et al. Sensors (Basel). .

Abstract

High Frequency (HF) communications through ionospheric reflection is a widely used technique specifically for maritime, aeronautical, and emergency services communication with remote areas due to economic and management reasons, and also as backup system. Although long distance radio links can be established beyond line-of-sight, the availability, the usable frequencies and the capacity of the channel depends on the state of the ionosphere. The main factors that affect the ionosphere are day-night, season, sunspot number, polar aurora and earth magnetic field. These effects impair the transmitted wave, which suffers attenuation, time and frequency dispersion. In order to increase the knowledge of this channel, the ionosphere has been sounded by means of narrowband and wideband waveforms by the research community all over the world in several research initiatives. This work intends to be a review of remarkable projects for vertical sounding with a world wide network and for oblique sounding for high latitude, mid latitude, and trans-equatorial latitude.

Keywords: Doppler spread; HF; SNR; communication; delay spread; ionosphere; oblique sounding; skywave; vertical sounding.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Ionogram of 10 March 2020 at 17 UTC recorded in Roquetes Station (Spain) offered by the Ebre Observatory. Available online at http://obsebre.es/en/checked-ionograms (accessed on 14 March 2020).
Figure 2
Figure 2
Map of digisondes contributing data to the Global Ionospheric Radio Observatory (GIRO). Red stars identify online digisondes providing data to GIRO in near-real-time, orange stars denote digisondes providing data to GIRO in no real time, yellow stars denote other type of ionosondes that also contribute to GIRO archives, and blue stars correspond to digisonde installations planned for the next future.
Figure 3
Figure 3
Evolution of digisonde sounders since 1969.
Figure 4
Figure 4
Deployment of the main sites used in the DAMSON project to sound the ionosphere. We can observe auroral, sub-auroral and polar regions.
Figure 5
Figure 5
(a) Complete block diagram of the DAMSON transmitter and (b) Complete block diagram of the DAMSON receiver.
Figure 6
Figure 6
Example DAMSON output, from Reference [36].
Figure 7
Figure 7
Block Diagram of WHISPER RF Front-end Direct Sampling HF Receiver
Figure 8
Figure 8
Geographical link characteristics. The transmitter is located in the Spanish Antarctic Station on Livingston Island, and the receiver is placed in Cambrils, Spain.
Figure 9
Figure 9
(a) The single transmitter antenna in Antarctica and (b) the three antennas of the receiver in Cambrils.
Figure 10
Figure 10
(a) Complete block diagram of the Antarctica project transmitter and (b) Complete block diagram of the Antarctica project receiver.
Figure 11
Figure 11
(a) Narrowband frame definition and (b) wideband frame definition.
Figure 12
Figure 12
Wideband channel response for February 1st 2014 at 07 UTC with 13 MHz of carrier frequency: (a) normalized channel response h[n, τ], (b) normalized scattering function Rs[τ, v], (c) multipath power profile (in ms), (d) Doppler power profile (in Hz).
Figure 13
Figure 13
(a) High robustness data frame definition and (b) high throughput data frame definition.
See this image and copyright information in PMC

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