Skin-MIMO: Vibration-based MIMO Communication over Human Skin

TL;DR

This paper demonstrates the feasibility of MIMO communication over human skin using vibrations, and introduces a deep learning-based method to predict channel state information from inertial sensors, significantly enhancing capacity.

Contribution

The paper presents Skin-MIMO, a novel deep learning approach for CSI prediction in vibration-based skin communication, eliminating the need for channel sounding.

Findings

Skin-MIMO improves MIMO capacity by 2.3 times over SISO.

Gyroscope data outperforms accelerometer in predicting skin vibrations.

Feasibility of vibration-based MIMO communication over human skin is confirmed.

Abstract

We explore the feasibility of Multiple-Input-Multiple-Output (MIMO) communication through vibrations over human skin. Using off-the-shelf motors and piezo transducers as vibration transmitters and receivers, respectively, we build a 2x2 MIMO testbed to collect and analyze vibration signals from real subjects. Our analysis reveals that there exist multiple independent vibration channels between a pair of transmitter and receiver, confirming the feasibility of MIMO. Unfortunately, the slow ramping of mechanical motors and rapidly changing skin channels make it impractical for conventional channel sounding based channel state information (CSI) acquisition, which is critical for achieving MIMO capacity gains. To solve this problem, we propose Skin-MIMO, a deep learning based CSI acquisition technique to accurately predict CSI entirely based on inertial sensor (accelerometer and gyroscope) measurements at the transmitter, thus obviating the need for channel sounding. Based on experimental vibration data, we show that Skin-MIMO can improve MIMO capacity by a factor of 2.3 compared to Single-Input-Single-Output (SISO) or open-loop MIMO, which do not have access to CSI. A surprising finding is that gyroscope, which measures the angular velocity, is found to be superior in predicting skin vibrations than accelerometer, which measures linear acceleration and used widely in previous research for vibration communications over solid objects.