Abstract
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.
Highlights
With the development of deep space exploration, improving the communication performance of deep space links has become a challenging topic
We propose a terrestrial–deep space hybrid radio frequency (RF)/Free space optical (FSO) system using hybrid L-pulse position modulation-binary phase shift keyingsubcarrier intensity modulation (L-PPM–BPSK–SIM) scheme, where the RF link obeys Rayleigh fading, and the FSO link follows Gamma–Gamma distribution
Substituting (20) and (22) into (21), the approximate closed-form expression of the unconditional bit error rate (BER) of the hybrid RF/FSO system modulated by L-ary pulse position modulation (L-PPM)–BPSK–SIM can be obtained: PBER
Summary
With the development of deep space exploration, improving the communication performance of deep space links has become a challenging topic. Based on the Rayleigh/Gamma–Gamma model proposed by [9], the outage probability, the average BER and channel capacity of the system are comprehensively studied [11] This model is robust in the simulation of turbulence at different intensities and has been recognized by many researchers. Inspired by the above researches, this paper applies the hybrid RF/FSO system to deep space communication based on the scintillation model proposed in [7], and discusses the end-to-end communication performance. As far as we know, there have been many studies on the influence of solar scintillation on radio wave communications [18,19,20], but studies for the hybrid RF/FSO system are relatively rare On this basis, considering the pointing error, the outage probability, BER, and average channel capacity expressions of the hybrid RF/FSO system in the deep space are derived.
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