Body-Worn Distributed MIMO System

Abstract

In this paper, we analyze the performance of novel wearable multiple-input-multiple-output (MIMO) systems, which consist of multiple electrotextile wearable antennas distributed at different locations on human clothing. For wearable applications, a semidirectional radiation pattern of the wearable patch antenna is preferred over an omnidirectional radiation of conventional dipole antennas to avoid unnecessary radiation exposure to the human body and radiation losses. Additionally, the spatial distribution of the antennas is not constrained as a typical handheld unit. Through theoretical modeling and simulation, the wearable MIMO system is shown to demonstrate a significantly higher channel capacity than a conventional system on a handheld platform (e.g., a compact dipole array or a single dipole), due to enhanced spatial diversity and antenna pattern diversity. The unique effects of antenna directivity and location on the MIMO system capacity are investigated in terms of antenna correlation and effective gain under different wireless channel models. The advantage of a wearable system over a conventional system was further confirmed by detailed physical modeling through the combination of full-wave electromagnetic and ray-tracing simulations. Finally, complex channel response matrices were measured to characterize the performance of a body-worn MIMO system in comparison with a reference full-size dipole antenna. The 319% improvement in 10% outage capacity for the body-worn system over the reference system made of a full-size dipole antenna is consistent with the 288% improvement projected by theoretical modeling and the average 300% improvement found in the physical simulation of two typical indoor scenarios.