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HARQ Performance Limits for Free-Space Optical Communication Systems
1Department of Electronics and Telecommunications, Politecnico di Torino, 10129 Turin, Italy.
Entropy (Basel, Switzerland)
|January 28, 2026
Summary
Hybrid automatic repeat request (HARQ) enhances free-space optical (FSO) communication reliability by combining error correction with retransmissions. This study analyzes HARQ
Area of Science:
- Optical Communications
- Wireless Networking
- Information Theory
Background:
- Free-space optical (FSO) systems offer high-speed, secure communication but suffer from atmospheric interference.
- Hybrid automatic repeat request (HARQ) protocols are crucial for mitigating FSO performance degradation.
- On-Off Keying (OOK) modulation is a common technique in FSO systems.
Purpose of the Study:
- Investigate the performance limits of HARQ in OOK-based FSO systems.
- Characterize achievable rates and finite-blocklength performance under channel dispersion.
- Analyze the interplay of HARQ, turbulence, and feedback delay for reliable optical links.
Main Methods:
- Information-theoretic analysis to determine fundamental performance limits.
- Channel dispersion modeling for rate-reliability tradeoff quantification.
- Examination of HARQ retransmission impact on FSO link performance.
Main Results:
- HARQ significantly improves the robustness of OOK-based FSO systems against impairments.
- Channel dispersion is critical for understanding rate-reliability tradeoffs in HARQ-FSO.
- The study provides insights into optimizing HARQ parameters for low-latency, high-reliability FSO links.
Conclusions:
- HARQ is an effective strategy for enhancing the reliability of FSO communication systems.
- Understanding the interaction between HARQ, fading, and feedback delay is essential for FSO network design.
- This research offers guidelines for deploying robust FSO links in future terrestrial and space networks.
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