Illustrative case
Redundant link for a remote site without fiber
- Requirement
- Continuous supervision of a site 40 km from the operations center, with no fiber on the route and none planned.
- What constrains the answer
- The operation tolerates no outage longer than the failover time, and the region has heavy concentrated rainfall — which rules out any redundancy that depends on the same physical medium.
Architecture
- 01Primary path over licensed point-to-point radio, sized against the region’s rainfall percentile rather than its average.
- 02Satellite contingency, with automatic failover triggered by route loss — not by interface loss, which takes longer to notice.
- 03Independent monitoring of both paths: a link that went down without telling anyone is worse than a link that does not exist.
What was rejected, and what it cost (3)
- Two radios of the same type on different frequencies
- It is cheaper and looks like redundancy, but both degrade together in the same storm. Redundancy that shares a failure mode is cost without coverage.
- Unlicensed-band radio
- It removes licensing cost and lead time. In exchange, there is no recourse when interference shows up — and on a continuous supervision link, it shows up.
- 4G/5G as the contingency
- It would be the fastest to deploy. It was ruled out here because of coverage at the site: a contingency that depends on signal nobody measured on site is an assumption, not a design.