BLE Indoor Positioning: RSSI Trilateration & Wall Shadowing Lab

A single BLE beacon can only tell a phone roughly how far away it is; three beacons let it work out exactly where it is. This simulator places a rider inside a two-room floor plan with three fixed beacons and runs the same log-distance path-loss model used by proximity-unlock systems on all three signals at once, each independently corrupted by fading noise and, when the direct path crosses an interior wall, a fixed extra attenuation the phone has no way to detect. From the three noisy distance estimates the simulator solves a real trilateration system for the rider's 2D position, so you can watch the estimate track the true position closely in open line-of-sight and drift measurably wide the moment a wall gets in the way of one beacon. Beacon A doubles as a scooter-style debounced unlock, so the same wall that blurs the position estimate also visibly stalls the unlock counter.