Abstract
Abstract A multiple-input multiple-output (MIMO) system for trans-horizon radio communications within the high-frequency (HF) band (3 to 30 MHz) is presented. The diversity of transmitted polarizations is proposed as an alternative to spatial diversity in order to limit the aperture of antenna arrays at both ends of the radio link. In a theoretical step providing the estimation of capacity gain for different MIMO architectures, a 2 × 2 MIMO solution transmitting two complementary circular polarizations is identified as a balanced trade-off between performance increase and complexity. The design of the corresponding system is described with a focus on antenna arrays and the kind of signal processing that should be implemented. This novel communication system has been tested on a 280-km-long radio link. The first results underline a data transfer rate reaching a value of 24.09 kbps (in a 4.2-kHz bandwidth) that significantly exceeds the current standards for HF modems.
Highlights
High-frequency (HF) radiowaves, when propagated through the ionosphere, can achieve long haul transmissions with a minimal infrastructure when compared to satellite links
This paper proposes an alternative based on the diversity of the transmitted polarizations. This original idea relies on the existence of two propagation modes through the ionosphere resulting from the medium anisotropy; these two solutions for the propagation equations are characterized by two different sets of parameters such as attenuation or group delay: the corresponding channel impulse responses present a low level of correlation which is suitable for efficient multiple-input multiple-output (MIMO) transmission
The work in [17] is based on the transmission of non-modulated carriers separated by an interval of 10 Hz to ensure their identification at the receiver; the MIMO channel is characterized inside a narrow bandwith equal to 30 Hz
Summary
High-frequency (HF) radiowaves (carrier frequency in the 3-to-30-MHz interval), when propagated through the ionosphere, can achieve long haul transmissions with a minimal infrastructure when compared to satellite links This specific channel presents a reduced coherence bandwidth estimated in most cases to several kilohertz. No transposition in the HF band is yet to be worked out this paper proposes an alternative based on the diversity of the transmitted polarizations This original idea relies on the existence of two propagation modes through the ionosphere resulting from the medium anisotropy; these two solutions for the propagation equations are characterized by two different sets of parameters such as attenuation or group delay: the corresponding channel impulse responses present a low level of correlation which is suitable for efficient MIMO transmission
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