# Analysis and Visualization of Deep Neural Networks in Device-Free Wi-Fi Indoor Localization

## TL;DR

This paper explores how deep neural networks learn and make decisions in device-free Wi-Fi indoor localization, using visualization techniques to interpret the model's features and improve understanding of its operation.

## Contribution

It introduces visualization methods to explain DNN learning processes and feature importance in Wi-Fi localization, enhancing interpretability of deep models in this domain.

## Key findings

- DNN features can be visualized in 2D to interpret their role.
- Feature manipulation reveals the contribution of each feature.
- The approach provides insights into DNN decision-making in localization.

## Abstract

Device-free Wi-Fi indoor localization has received significant attention as a key enabling technology for many Internet of Things (IoT) applications. Machine learning-based location estimators, such as the deep neural network (DNN), carry proven potential in achieving high-precision localization performance by automatically learning discriminative features from the noisy wireless signal measurements. However, the inner workings of DNNs are not transparent and not adequately understood especially in the indoor localization application. In this paper, we provide quantitative and visual explanations for the DNN learning process as well as the critical features that DNN has learned during the process. Toward this end, we propose to use several visualization techniques, including: 1) dimensionality reduction visualization, to project the high-dimensional feature space to the 2D space to facilitate visualization and interpretation, and 2) visual analytics and information visualization, to quantify relative contributions of each feature with the proposed feature manipulation procedures. The results provide insightful views and plausible explanations of the DNN in device-free Wi-Fi indoor localization using channel state information (CSI) fingerprints.