When the backhaul is a satellite

01Map story

Site, satellite, gateway.

A remote site’s terminal links to a satellite in low orbit, which relays to a gateway hundreds or thousands of kilometres away, and from there to the core network. The arcs here run from a northern site to a gateway in the south; the orbit passes over both.

Figure as text: A remote site, a gateway and a low-orbit relay

A wireframe globe over North America with a remote site, a gateway station, an arc between them and a low orbit with its ground track.

• Remote site (68.4° N, 133.7° W)
• Gateway (49.3° N, 123.1° W)
• Core network (43.7° N, 79.4° W)

02Data story

The delay budget.

A bent-pipe relay adds two slant ranges of propagation. In low orbit that is milliseconds; in geostationary orbit it approaches a quarter of a second each way, which the standard’s timing advance and retransmission procedures have to absorb².

Figure as text: Propagation delay by orbit, user to gateway

A bar chart of computed one-way user-to-gateway delays for five orbits.

03Simulator

Footprint and altitude.

Each satellite serves the ground it can see above the elevation mask. A higher mask means shorter, cleaner paths and a smaller footprint; set both and read the slant range and delay³.

Figure as text: Footprint and delay of a backhaul satellite

A section through the Earth with a satellite above it and its footprint arc in red.

04Systems diagram

Two paths out.

A site with both a low-orbit and a geostationary terminal keeps a path when one fails, at the cost of delay. The waveform family used across satellite services makes the second terminal an ordinary one⁴.

Figure as text: A remote site with two satellite paths

A four-tier diagram: site equipment, the site router, two satellite paths, and the gateway and core.

• Site: Local cell, Sensors
• Router: Site router
• Space: LEO, GEO
• Ground: Gateway, Core

7 links. Scenarios: Low orbit in use; Low-orbit path lost.