Patent Document ID: 9288632
Application ID: 13995563
Patent Status: 1

Claim One:
1. A device comprising: a WLAN similarity component that implements an algorithm to obtain a first level coarse indicator on a revisit point based from similarities of received radio signal that includes at least a received signal strength indicator (RSSI), signal time-of-flight, or channel fading profiles of the radio signal at different time steps; an inertial navigation system (INS) dead reckoning estimator component that estimates motion trajectory of the device at different time steps; a spatial coherence component that implements a spatial coherence algorithm to obtain a spatial confidence level on the revisit point by analyzing trajectory structure similarity that is based from the estimated motion trajectory; a temporal coherence component that utilizes a fuzzy matching algorithm to detect similarity at multiple time steps on the analyzed trajectory structure similarity and the first level coarse indicator; and a loop closing detector that performs a threshold measurement on the detected similarity to determine occurrence of the revisit point.