低軌道(LEO)衛星向け回生型5G gNodeBペイロードのシステム工学

Technical analysis and engineering reference.

1. The Architectural Shift from Transponders to Base Stations

For sixty years, communications satellites functioned as analog mirrors: receiving a radio frequency, shifting it, amplifying it, and bouncing it back to Earth ('bent-pipe'). As mobile networks moved to 5G New Radio with tight millisecond frame structures and high-speed modulation, transparent transponders introduced intolerable round-trip latency penalties.

2. Onboard Regenerative Baseband Architecture

NTNSpace integrates full baseband stacks directly on the satellite bus: - Multi-channel digital receivers convert RF signals directly into digital I/Q samples. - Radiation-hardened FPGA clusters execute Physical Layer (PHY) processing, demodulating symbols and correcting errors via high-speed LDPC decoders. - MAC and RLC protocols manage packet scheduling, while a containerized User Plane Function (UPF) routes packets directly to peer satellites via optical laser crosslinks.

3. Resilience Against Gateway Blackouts

If a typhoon or earthquake destroys the ground teleport station, a regenerative satellite continues operating autonomously: users within the satellite's 1,000 km footprint can call each other, and intercontinental traffic continues across the space laser mesh without requiring any local terrestrial infrastructure.

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