# Towards Practical Indoor Positioning Based on Massive MIMO Systems

## TL;DR

This paper demonstrates a practical indoor positioning system using neural networks and existing MIMO channel data, achieving good accuracy with minimal additional overhead and robustness over time.

## Contribution

It introduces a tailored neural network architecture with fewer parameters, enabling effective indoor positioning solely based on existing MIMO system data.

## Key findings

- Achieved accurate indoor positioning over 80m2 area with 64 antennas.
- Robustness maintained over several days despite environmental changes.
- Fine-tuning reduces training data needs for similar accuracy.

## Abstract

We showcase the practicability of an indoor positioning system (IPS) solely based on Neural Networks (NNs) and the channel state information (CSI) of a (Massive) multiple-input multiple-output (MIMO) communication system, i.e., only build on the basis of data that is already existent in today's systems. As such our IPS system promises both, a good accuracy without the need of any additional protocol/signaling overhead for the user localization task. In particular, we propose a tailored NN structure with an additional phase branch as feature extractor and (compared to previous results) a significantly reduced amount of trainable parameters, leading to a minimization of the amount of required training data. We provide actual measurements for indoor scenarios with up to 64 antennas covering a large area of 80m2. In the second part, several robustness investigations for real-measurements are conducted, i.e., once trained, we analyze the recall accuracy over a time-period of several days. Further, we analyze the impact of pedestrians walking in-between the measurements and show that finetuning and pre-training of the NN helps to mitigate effects of hardware drifts and alterations in the propagation environment over time. This reduces the amount of required training samples at equal precision and, thereby, decreases the effort of the costly training data acquisition