Hybrid Dual-Hop RF/FSO Terrestrial-Deep Space Communication System Under Solar Scintillation during Superior Solar Conjunction

Free-space optical communication (FSO) technology has wide prospects in deep space exploration, but it will encounter coronal turbulence during superior solar conjunction, and solar scintillation will seriously affect the communication quality. In this paper, we propose a terrestrial–deep space hybrid radio frequency (RF)/FSO system with the hybrid L-pulse position modulation-binary phase shift keying-subcarrier intensity modulation (L-PPM–BPSK–SIM) scheme, where the RF channel of the satellite-terrestrial relay follows the Rayleigh distribution, and the FSO channel of the relay satellite to the deep space probe adopts Gamma–Gamma distribution. Considering the pointing error, the expression of the bit error rate (BER), the outage probability, and the average channel capacity of the hybrid system are derived. In addition, we evaluated the influence of coronal turbulence parameters on the system through amplitude fluctuations. The simulation results demonstrate that the hybrid RF/FSO system improves the BER performance by 10 to 30 times in a deep space environment, and the use of a hybrid modulation can further reduce the BER. The non-Kolmogorov spectral index, outer scale, solar wind density fluctuation factor, and optical wavelength comprehensively affect the BER through amplitude fluctuations. Our research results have potential application value for evaluating the link performance of future deep space communications.

The New Wuqing 70 m Radio Telescope and Measurements of Main Electronic Properties in X-band

The new Wuqing 70 m radio telescope is firstly used for the downlink data reception in the first Mars exploration mission of China, and will be used for the other deep space communications and radio astronomical observations in the future. The main specifications and measurement results of some properties in X-band are introduced in this paper, such as pointing calibration, gain and efficiency, system noise temperature, system equivalent flux density, and variations with elevation. The 23 parameters pointing calibration model considering the atmospheric refraction correction in real time is presented in the telescope, and the pointing accuracy is reached 5.70″ in azimuth direction and 6.07″ in elevation direction respectively for different weather condi-tions. More than 62% efficiencies are achieved at full elevation range, and more than 70% in the mid-elevation. The system equivalent flux density of X-band in the mid-elevation is reached 26 Jy.

High-Altitude Configuration of Non-Terrestrial Telecommunication Network using Optical Wireless Technologies

Non-terrestrial communication technologies will become a key component for the development of future 6th generation (6G) networks. Potentials, implementation prospects, problems and solutions for non-terrestrial telecommunications remain open areas for future research. The article discusses the use of millimeter and optical wavelengths in various configurations of multilevel space communications using LEO satellites, stratospheric platforms and unmanned repeaters. The comparison of the capacity of the Shannon channel for various multi-level scenarios of the satellite communication line is carried out. The directions of research are analyzed to ensure the continuity of communication, adaptation to weather conditions, and achieving a throughput of up to 100 Gbit/s.

An Overview of Geometrical Optics Restricted Quantum Key Distribution

Quantum key distribution (QKD) assures the theoretical information security from the physical layer by safely distributing true random numbers to the communication parties as secret keys while assuming an omnipotent eavesdropper (Eve). In recent years, with the growing applications of QKD in realistic channels such as satellite-based free-space communications, certain conditions such as the unlimited power collection ability of Eve become too strict for security analysis. Thus, in this invited paper, we give a brief overview of the quantum key distribution with a geometrical optics restricted power collection ability of Eve with its potential applications.

Methodical approach to estimation of energy characteristics of antenna arrays of space communication means of decimeter wavelengths

The article describes a sequence of mathematical and logical operations for determining the energy and mass-dimensional characteristics of an active phased array antenna operating in the decimeter wavelength range of space communications necessary to ensure continuous operation for a given time. When designing large-size antenna systems, a preliminary assessment of the mass-size, energy and thermal parameters is required to assess the feasibility of the project. In this regard, the article uses a mathematical apparatus that includes a model and methods that allow determining the tactical and technical characteristics of satellite communication systems at the design or development stage. The novelty of the developed method consists in assessing the potential capabilities of spacecraft of satellite communication and retransmission systems, taking into account the energy and weight and size characteristics of their antenna systems and in determining the degree of implementation of the main modes of operation of Earth stations at the design or development stage for the specified operating modes of satellite communication systems.