Effects of human limb gestures on galvanic coupling intra-body communication for advanced healthcare system

Abstract

Background: Intra-Body Communication (IBC), which utilizes the human body as the transmission medium to transmit signal, is a potential communication technique for the physiological data transfer among the sensors of remote healthcare monitoring system, in which the doctors are permitted to remotely access the healthcare data without interrupt to the patients' daily activities.

Methods: This work investigates the effects of human limb gestures including various joint angles, hand gripping force and loading on galvanic coupling IBC channel. The experiment results show that channel gain is significantly influenced by the joint angle (i.e. gain variation 1.09-11.70 dB, p < 0.014). The extension, as well as the appearance of joint in IBC channel increases the channel attenuation. While the other gestures and muscle fatigue have negligible effect (gain variation <0.77 dB, p > 0.793) on IBC channel. Moreover, the change of joint angle on human limb IBC channel causes significant variation in bit error rate (BER) performance.

Conclusions: The results reveal the dynamic behavior of galvanic coupling IBC channel, and provide suggestions for practical IBC system design.

Keywords: Bit error rate; Galvanic coupling intra-body communication; Human limb gestures; Joint angle; Muscle fatigue.

Fig. 1

Experiment setup to investigate the effects of limb gestures on galvanic coupling IBC channel. For upper extremity channels (A1A2 and A1A3), the frequency response at each joint angle is measured with empty-handed, gripping force and loading. For lower extremity channels (B1B2 and B1B3), it is measured with the change of knee joint angles

Fig. 2

Experiment setup to investigate the effects of muscle fatigue on galvanic coupling IBC channel. With hand loading 2.5 kg dumbbell and elbow joint flexing to 45°, the EMG of biceps and frequency response of A1A2 are measured

Fig. 3

Experiment setup to avoid the movement of upper arm or thigh. For channels A1A2 and A1A3, the setup is adapted to avoid the movement of upper arm, while for B1B2 and B1B3, the movement of thigh is avoided

Fig. 4

Gain and phase on upper extremity channels (A1A2 and A1A3) with various elbow joint angles. The solid curves with symbols refer to the y-axis on the left, depict the gain (a for A1A2, b for A1A3) and phase (c for A1A2, d for A1A3). The dotted curves with symbols refer to the y-axis on the right, represent the average of standard deviation from the measurements over 3 days

Fig. 5

Gain and phase on lower extremity channels (B1B2 and B1B3) with various knee joint angles. The solid curves with symbols refer to the y-axis on the left, depict the gain (a for B1B2, b for B1B3) and phase (c for B1B2, d for B1B3). The dotted curves with symbols refer to the y-axis on the right, represent the average of standard deviation from the measurements over 3 days

Fig. 6

Gain and phase at two joint angles for the four subjects. The values at 90° are depicted by lines with symbols. Lines with error bars (variance over 3 days measurement) and symbols represent the values at 180°. The values from channel A1A2, A1A3, B1B2 and B1B3 are displayed in sub-figure a, b, c and d, respectively. Lines with symbol rectangular, star, triangle and circle is for S1, S2, S3 and S4, respectively

Fig. 7

Muscle fatigue effect on IBC channel. In the subfigure with double y-axis, the gain is depicted by solid curves with symbols, while phase is depicted by dotted curves