A major obstacle for using lasers rather than radio communication in space has been successfully targeted by Japanese researchers. Unlike radio waves, optical wireless communication eliminates the need for frequency allocation and wireless licenses, while offering high-speed connectivity. However, optical signals are vulnerable to atmospheric turbulence. In the Japanese project, advanced error correction codes were applied, mitigating the problem.
Atmospheric turbulence is known to cause fading of optical signals, resulting in so-called burst data errors. Researchers from the National Institute of Information and Communications Technology (NICT), and the Nagoya Institute of Technology, collaborated with the Japan Aerospace Exploration Agency (JAXA).
The collaboration has achieved the world’s first successful demonstration of next-generation error correction codes, mitigating the impact of atmospheric turbulence.
Atmospheric disturbance was revealed
The project involved an optical data relay satellite at approximately 36,000 km altitude. At this altitude, it is possible for a satellite to follow the Earth’s rotation thereby staying at the same position relative to the ground. This is known as a geostationary orbit.
Onboard the satellite is JAXA’s Laser Utilizing Communication System (LUCAS). In the experiments, laser experiments from the ground to LUCAS were carried out.
The investigation revealed that atmospheric turbulence causes fading lasting from several milliseconds to several tens of milliseconds, which generates burst data errors. These errors lead to degraded and unstable communication quality.
Further, the researchers conducted data transmission with next-generation error correction codes (5G NR LDPC and DVB-S2) using a 60 Mbps downlink. The experiment demonstrated the correction of burst data errors caused by atmospheric turbulence-induced fading, marking the world’s first confirmation that the two codes can significantly improve communication quality compared to conventional codes.
Potential application in disaster management
In recent years, optical wireless communications have attracted attention as a next-generation high-speed communication technology. The possible applications of optical wireless space-space and ground-space communications are manyfold. For instance, the technology is expected to contribute to the immediate relay of Earth observation data, connectivity in underserved areas, rapid restoration of communications in disaster situations, and low-latency intercontinental backbones, thereby enabling fast, largescale and flexible network deployments.
The successful mitigation of data burst errors caused by atmospheric turbulence has the potential for accelerating the practical implementation of ground to satellite laser links.
Source: “Successful Ground-to-Satellite Laser Communications Applying Next-Generation Error Correction Codes, Mitigating Atmospheric Turbulence”, Press Release, National Institute of Information and Communications Technology (NICT), and the Nagoya Institute of Technology.
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