The evolution to denser radio-access networks with small cells in cluttered urban environments has introduced new challenges for microwave backhaul. A direct line of sight does not always exist between nodes, and this creates a need for near- and non-line-of-sight (NLOS) microwave backhaul.

However, deploying high-performance microwave backhaul in places where there is no direct line of sight (LOS) brings new challenges for microwave-backhaul network architects. The traditional belief in the telecom industry is that sub-6GHz frequencies are required to ensure performance in locations where non line of sight (NLOS) conditions exist.

This article puts that belief to the test, providing general principles, key system parameters and simple engineering guidelines for deploying microwave backhaul using frequency bands above 20GHz. Trials demonstrate that such high-frequency systems can outperform those using sub-6GHz bands – even in locations with no direct line of sight.

Non-line-of-sight microwave backhaul for small cells