Problem of Wireless Fingerprint Duplication in Fingerprinting Based Indoor Localization

Fingerprinting technique is one of the most widely used localization techniques in an indoor environment. This technique maps the most likely locations of the target, also referred to as Reference Points (RPs), with fingerprints of the Access Points (APs) collected at those RPs. A wireless fingerprint is a feature (such as RSS, Path-Loss or Data Rate) that is derived from the collection of wireless signal samples of the APs. The most important aspect of the fingerprinting technique is the distinct wireless fingerprints that represent different RPs. However, different factors such as equal distance of multiple RPs from the same AP, may lead to fingerprint duplication, i.e. multiple RPs may have similar fingerprints, which can result in false localization. This paper highlights the problem of fingerprint duplication in fingerprinting based indoor localization. The paper further discusses the fingerprint duplication with three different fingerprint metrics i.e. RSS fingerprint, Path-loss fingerprint and Data Rate fingerprint, used in fingerprinting based indoor localization. To address this problem, RSS spread is proposed to be used in conjunction with different fingerprint metrics (i.e. RSS, Path-Loss or Data Rate) to differentiate among RPs. The results of the experiment verifies the occurrence of similar fingerprints of AP that operates with multiple transmission power levels at different RPs with all 3 fingerprint metrics. The results also shows that RSS spread fingerprints of AP with multiple transmission levels are all different and distinct. Additionally, it is observed that the significance of RSS spread tends to increase at low transmission power level which motivates and leverage the use of low transmission power levels in fingerprinting based indoor localization.