Deep Space Communication Systems: Foundations, Networking Architectures, and a Roadmap Toward the Interplanetary Internet
Deep Space Communication (DSC) is a critical enabler for reliable data exchange between Earth-based infrastructure and spacecraft operating beyond lunar orbit. This paper presents a comprehensive and up-to-date survey of DSC systems, encompassing architectural foundations, enabling technologies, and emerging research challenges. In particular, the structure and operation of Deep Space Communication Networks (DSCNs) are examined, highlighting the functional interactions among deep space stations, communication complexes, signal processing centers, and mission control centers under severe propagation delays and intermittent connectivity. The paper provides a systematic review of traditional Radio Frequency (RF) communication and emerging Free-Space Optical (FSO) technologies, including hybrid RF/FSO architectures, and analyzes their trade-offs in terms of robustness, bandwidth efficiency, power consumption, and operational complexity. Recent mission demonstrations and international technology roadmaps are discussed to illustrate the ongoing transition toward high-capacity optical links for future lunar, Martian, and deep-space missions. Furthermore, advances at the physical and link layers are surveyed, covering modulation techniques, forward error correction schemes, and adaptive link optimization, with particular emphasis on Low-Density Parity-Check (LDPC) codes, Polar codes, hybrid forward error correction (FEC) schemes, and Adaptive Coding and Modulation (ACM) for operation under low signal-to-noise ratios and time-varying channels. At the networking layer, the paper reviews Consultative Committee for Space Data Systems (CCSDS) standards and Delay/Disruption-Tolerant Networking (DTN) protocols, identifying key open research challenges related to scalability, routing, buffering, quality-of-service support, and autonomous operation. By integrating physical-layer technologies, networking protocols, and system-level considerations, this work outlines emerging trends, including AI-native communication architectures, that are expected to shape the design of scalable, autonomous, and interoperable interplanetary communication networks.