Study on the Transmission Mechanism for Wearable Device Using the Human Body as a Transmission Channel

Abstract

Recently, wearable devices which use the human body as a transmission channel have been developed. However, there has been a lack of information related the transmission mechanism of such devices in the physical layer. Electromagnetic communication trials using human body as transmission media have more than a decade's history. However, most of the researches have been conducted by researchers who just want to utilize the fact and practically no physical mechanisms have been researched until recently. Hence, in previous study, the authors proposed calculation models of the wearable transmitter and the receiver attached to the arm using the FDTD method. Moreover, the authors compared the calculated received signal levels to the measured ones by using a biological tissue-equivalent phantom. However, there was little analysis on each component of the propagated signal. In this paper, the authors clarified the transmission mechanism of the wearable device using the human body as a transmission channel from the view point of the interaction between electromagnetic wave and the human body. First, the authors focused their attention on measuring the each component of the propagated signal using a shielded loop antenna. From these results, the favorable direction of electrodes of the transmitter was proposed to use the human body as a transmission channel. As a result, longitudinal direction is effective for sending the signal to the receiver, compared to the transversal direction. Next, the authors investigated the dominant signal transmission channel, because the question of whether the dominant signal channel is in or around the arm had remained unsettled. To clear this question, the authors proposed the calculation model of an arm wearing the transmitter and receiver placed into a hole of a conductor plate. The electric field distribution and received signal voltage was investigated as a function of the gap between the hole of the conductor plate and the surface of the arm. The result indicated that the dominant signal transmission channel is not inside but the surface of the arm because signal seems to be distributed as a surface wave.

Body Area Networks: Radio channel modelling and propagation characteristics

“…SPECIAL CASE: TRANSMITTER AND RECEIVER LOCATED OUTSIDE OF THE BODY In this section, we write (16) in an explicit form which can be used to study the propagation characteristics around the human body (model) by simulation.…”

“…The human body is a very complex environment and has not been studied explicitly for wireless communication. Although, a while ago the human body was under focus for the measurement of electromagnetic absorption studies, such as specific absorption rate and dosimetry [14], [15], [16], [17].…”

Electrooptic sensor module fabrication for near-field intrabody communication

“…There are various methods of near-field intrabody communication; [1][2][3][4][5][6][7][8][9][10][11][12][13][14] however, to realize communication at a high data transfer rate, the use of a communication system with a quasi-electrostatic field (an electric field) as the communication transmission carrier is promising.…”

Dual-mode antenna for on-/off-body communications (10 MHz/2.45 GHz)

“…In remote health monitoring, at least two modes of communication are required: on-body communications (collecting medical data) and off-body communications (exchanging data with outside networks). For on-body communications, relatively low frequency bands (tens of MHz) are more suitable [3,5], while for off-body communications, the 2.45 GHz ISM band (2.40-2.48 GHz) is a good candidate [6]. Thus, a dual-mode antenna is a key component for remote health monitoring.…”

“…Since the proposed antenna is designed to support on-body and off-body communications, its characteristics in the two modes will be discussed in the following two Sections. On-body mode: In on-body mode, since the communication is based on the quasi-static field, the received voltage is often adopted to evaluate the system [3]. Thus, in our measurement setup, two of the proposed antenna, as Tx and RX, were both attached to the arm phantom (e r ¼ 170.73, s ¼ 0.62 S/m) with a size of 50 × 50 × 600 mm 3 , as shown in Fig.…”