Microwave LOS Qualification
As operators move towards deploying higher frequency bands, the propagation characteristics will become worse at the same time sites will need to support large bandwidths and high peak rates. This places additional backhaul requirements on these small sites.
Sites have traditionally been connected using Fiber, but when we talk about site densities of 10x compared to current generation trenching fiber to all sites will no longer be practical.
There is a growing interest from operators to use mmWave backhaul technologies to connect these sites to their nearest Fiber PoP. Using microwave operators can avoid lengthy permitting & expensive trenching processes. Using microwave operators can achieve speed of deployment at a much lower cost, but microwave brings in its own challenges.
Traditionally Microwave planning is done by sending two teams to the top of candidate sites. These teams using visual aids try to estimate line of sight between buildings. This methodology works fine when there are few sites, but it’s no longer scalable when tens of sites are involved.
One of our customers, a Tier-1 operator had a requirement to plan a microwave backhaul network between tens of buildings in a city. They needed to test out all possible combinations between a list of buildings before their Network planning teams could start defining the layout.
For this project, we used 6” high resolution DSM (Digital Surface Maps) to detect the presence of any obstruction in Fresnel zone of a 70GHz point-to-point link in all site combinations.
The plots below show 3 lamp post based site locations while the remaining 4 are on top of high rise buildings. The fresnel zone with green color has no obstruction while red represents an obstruction.
All combination of LOS
Zoomed in view 0 <-> 2 link
Further zoomed in view of 0<->2 link demonstrating a ~50cm obstruction due to a tree branch in fresnel zone
The plot above demonstrates that it is possible to detect obstructions of ~20cm from hundreds of meters away using high resolution DSM (Digital Surface Maps).
3D Visualization of Qualified Microwave links.
This process of calculating LOS combinations between a large number of candidate locations is scalable to city level as demonstrated by the plot below which tested LOS between all combinations of 1000 lampposts. This scenario tested 28K links and qualified ~3K links.
Special thanks to Nearmap for providing the 6 inch resolution DSM & True Ortho imagery used for this analysis.