Interpolation and Extrapolation of Multipath Fingerprints Using Virtual Transmitter Placement

Fingerprinting-based localization approaches generally show the highest localization precision in complex indoor non-line-of-site environments. However, they require the construction of a dense fingerprint map, which can lead to high system deployment and maintenance costs. In this paper, we focus on extending a measured fingerprint map though interpolation and extrapolation. In this way, the accuracy of an indoor localization system (ILS) can be improved without increasing its deployment cost. We focus on channel state information (CSI) based fingerprinting approaches as they have shown superior localization accuracy and robustness. This paper presents a novel algorithm for interpolating and extrapolating CSI and multipath fingerprints by calculating the positions of the so called virtual transmitters (VTs). The performance of the interpolation scheme is validated through simulation. The localization error distribution of an ILS using an interpolated and extrapolated fingerprint map is evaluated and compared to the case when the original map is used. The obtained results demonstrate a 20% decrease in the average localization error through the use of the proposed fingerprint interpolation scheme. Furthermore, the presented results show that when an extrapolated map is used, the probability that a user is precisely localized is less dependent on his position in the indoor environment.