Because satellite microwave signals degrade severely inside concrete structures, indoor mobile positioning relies on Wi-Fi Received Signal Strength Indication (RSSI) and BSSID fingerprinting.

1. Wi-Fi Positioning System (WPS) Mechanics

  • Crowdsourced BSSID Mapping: Operating systems continuously cache the MAC addresses (BSSIDs) and signal strengths of visible Wi-Fi access points, referencing global cloud databases (Google Location Services, Apple Wi-Fi DB).
  • Fingerprinting vs. Model-Based Trilateration: Radio fingerprinting maps RF signal strength vectors against pre-surveyed floor plans, achieving 2-to-5 meter precision without requiring known AP physical locations.
  • Pedestrian Dead Reckoning (PDR): Smartphone accelerometers and magnetometers count steps and track heading, smoothing position drift between Wi-Fi beacon updates.