How Lasers Can Light the Path to Spectrum Sharing
By: NTIA
Lidar, a sensing method that uses light waves, has been around since the 1960s when the United States developed it as a military technology for defense and aerospace uses. But the advent of publicly-available lidar data has made it a crucial tool for helping radio scientists inside and outside of government better predict where objects like trees and buildings will likely interrupt a wireless signal. These more accurate predictions can enable more opportunities for government and non-government users to share the airwaves.
By measuring the time it takes for a laser pulse to return to its sending point, a lidar system measures and records the shapes and heights of buildings, trees, and other surface features to create a very precise three-dimensional model of an environment. Spectrum sharing relies on these propagation models to predict signal strength between two points, such as a cell phone and a government system like an air traffic control radar.
With high-precision information about the environment, radio scientists can better understand the layout and orientation of obstructive objects — known as “clutter” — that can decrease an interfering signal’s strength, increasing the ability of multiple systems to share the same spectrum.