High-dimensional radio frequency fingerprint synthesis for indoor positioning

Abstract

Fingerprint-based indoor positioning systems (IPSs) are being explored to aid in location-based services due to their robustness in nonline-of-sight (NLOS) conditions. Current systems use high-dimensional radio frequency (HDRF) fingerprints, such as Wi-Fi channel state information (CSI), to achieve higher positioning precision. Since data acquisition is labor-intensive, researchers proposed to enrich the dataset with generative models. It, however, faced challenges arising from capturing the intricate HDRF distribution using simplistic models and the lack of a framework that simultaneously addresses the generative model training, sample evaluation, and selection. In order to synthesize high-quality HDRF fingerprints, this article proposes an HDRF fingerprint generation framework using a conditional diffusion model (CDM) that learns the packet-level feature distribution by decomposing HDRF fingerprints using grid points, anchors, and frequency channel information while preserving the feature spatial correlation within a fingerprint. A sample selection process using the Mahalanobis distance and the principal component analysis (PCA) Q-statistic is used to ensure the sample fidelity. An adaptive learning strategy is further developed to integrate the generated synthetic HDRF fingerprints into downstream positioning tasks. Experimental results on two HDRF datasets quantitatively and qualitatively showcase the diversity and fidelity of the synthetic samples. Compared to solely using the original dataset, integrating the synthetic HDRF fingerprints from the developed framework to train downstream positioning models can, furthermore, decrease the positioning error by up to 16%.