On-Body NLoS Radio Channel at Millimeter-Wave Frequencies

This article presents an analysis of on-body radio channels at millimeter-wave frequencies and possible solutions to reduce the path loss, particularly, at non-line of sight (NLoS) locations. We have chosen two specific channels around the wrist and waist, and a comprehensive study has been conducted at the frequency of 94 GHz. It is observed that in the presence of textile, a slow wave mode can be excited tangentially near the surface of human body. Clothing and the thin air between the clothing and the human body surface may attribute to the reduction of path loss at NLoS. Our findings show that the presence of different garment materials is linked to the variation of path loss in on-body radio channels. Moreover, we demonstrate numerically that by attaching thin metallic sheet underneath clothing may further reduce the path loss. In our parametric study, a maximum of 15 dB drop occurs in path loss at only 30 cm distance. A robust theoretical model based on the knife edge diffraction (KED) method has been applied to give physical insights of such a unique radio propagation mechanism, that can lead to abundant applications in 5G communications and beyond.