The Basic Link
Satellite internet relays data between a user terminal on the ground, a satellite in orbit, and a ground station connected to the internet backbone. The terminal transmits a request upward; the satellite relays it to a ground station (or another satellite via laser link), which connects to the internet. The response follows the reverse path.
User Terminals
Modern LEO terminals use electronically steered phased-array antennas — flat panels that rapidly switch beam direction to track fast-moving satellites. Starlink's "Dishy" is a ~50 cm flat rectangle that auto-aligns on first power-up. The antenna handles satellite handoffs seamlessly — as one satellite moves out of range, the beam switches to the next, typically every 15–90 seconds, with no perceptible interruption.
Satellite Relay
Each satellite covers a ground "cell" (typically 15–25 km diameter) and multiplexes connections from all terminals in that cell. Satellites communicate with the ground using Ka-band (26.5–40 GHz) or Ku-band (12–18 GHz) radio. Each satellite has limited beams and throughput, which is why subscriber density matters.
Inter-Satellite Laser Links
One of the most significant advances is optical inter-satellite links (ISLs) — laser connections between satellites that route data through space without touching the ground. Starlink v1.5+ satellites include laser links. ISLs enable coverage over oceans and polar regions, and for some long-distance routes, routing through vacuum (where light travels ~47% faster than in fibre) can actually beat terrestrial fibre latency.
Ground Stations (Gateways)
Ground stations are large antenna installations connecting the constellation to the terrestrial internet backbone. Each station maintains simultaneous links with several overhead satellites. Ground station density affects performance — areas far from gateways rely more heavily on ISLs, adding slight latency.
Frequency Bands
| Band | Frequency | Usage | Characteristics |
|---|---|---|---|
| Ku-band | 12–18 GHz | Terminal ↔ satellite | Good rain resilience, moderate bandwidth |
| Ka-band | 26.5–40 GHz | Satellite ↔ ground station | Higher bandwidth, more rain-sensitive |
| V-band | 40–75 GHz | Next-gen high-throughput | Very high bandwidth, limited range |
| Optical | ~1550 nm | Satellite ↔ satellite | Highest bandwidth, no spectrum licensing |
Why LEO Changes Everything
GEO satellites at 35,786 km impose ~480 ms minimum latency. LEO at 550 km reduces this to ~3.7 ms signal round-trip, yielding 25–60 ms real-world latency. The trade-off: you need thousands of satellites for global coverage, but the latency gain makes satellite internet practical for the first time for video calls, gaming, VPNs and cloud services.