Performance Analysis of LEO Satellite-Assisted Deep Space Communication Systems

Relay-assisted deep space communication systems are crucial for overcoming space exploration's vast distances and harsh conditions, efficiently accommodating the increasing demand for high-speed data transmission and reliable communication links. However, due to factors such as coronal turbulences, molecular absorption, and pointing errors, fading channels can adversely affect the performance of deep-space communication systems. This paper proposes a low Earth orbit (LEO) satellite-assisted deep space communication system with the decode-and-forward relaying protocol. Specifically, the exponentiated Weibull distribution is used to characterize the free-space optical (FSO) link between the LEO satellite and a deep space probe, given the non-zero pointing error impairments, coronal turbulence, and solar noise. Meanwhile, considering the mobility of the LEO satellite and the molecular absorption effect on the radio frequency signal for the LEO satellite-to-Earth terrestrial link, the fading is modeled using the shadowed-Rician distribution. We derive the cumulative distribution and probability density functions of the signal-to-noise ratio for the considered system. Thereafter, utilizing these derived formulas, the analytical and asymptotic expressions for the performance metrics, including outage probability, average bit error rate, and ergodic capacity, are derived. Monte Carlo simulations are verified to validate the derived expressions. The results show that the performance of the LEO satellite-assisted deep space communication system outperforms that of the pure FSO system. However, it is still susceptible to key parameters, such as turbulence conditions, solar noise, and non-zero pointing errors. As a result, this research lays the foundation for developing future deep-space communication systems.