Cellular Echoes: How Your Phone Navigates Without GPS express
A city signal bounces between walls like a ball, and your phone catches dozens of its 'reflections'—echoes. Each microsecond of delay adds 300 meters to the path.
The neural network processes this noise in two stages. First, like a keen ear, it filters out interference and isolates each echo. Then it assembles them into a coherent picture, much like delay analysis splits a radio signal into 'rays'.
City tests: distance error—3.5 m, direction error—2.5°. That's enough to tell which side of a building you're on. Signals from multiple towers are combined and smoothed for better accuracy. A regular smartphone will soon navigate indoors as if it had GPS.
Every microsecond of delay is 300 meters, so by listening to echoes, your phone acts like a radar with centimeter-level precision.
Philip K. Dick foresaw this technology: in his stories, police tracked people by signals — now this becomes reality without any satellites.