Device-free localization using redundant 2.4 GHz radio signal strength readings

Radio-based device-free localization (DFL) for indoor environments are based on signal anomalies due to obstacles on the line-of-sight (LOS) between previously applied reference nodes. They take use of radio signal strength (RSS) attenuation (radio tomographic imaging, RTI) or variations caused by shadowing and small-scale fading effects. An advanced methodology using redundant RSS information for each pair of reference nodes is proposed. The method uses a moving RSS variance estimator and antenna diversity with four uncorrelated 2.4 GHz radio channels to predict the user's position. With the redundant RSS values the accuracy of user detection is increased by more than 50 % while the number of false positives is reduced to zero. Tracking results in a hallway test bed illustrate the behavior and improvements of the applied redundant sensor technique.