An empirical comparison of limb joint effects on capacitive and galvanic coupled intra-body communications

Intra-body communication (IBC) is a recent wireless communication technology which uses the human body as the signal propagation medium. While recent studies have shown a degradation of transmission signals for IBC transmissions between limb segments, these degradations have yet to be quantified with respect to relative limb positions. In this paper we report in vivo experiments towards understanding signal attenuation in both capacitive and galvanic coupled IBC methods due to limb joint effects. We examine the impact of elbow joint flexion and extension on signal transmission. Results show that in both IBC methods, the signal attenuation is larger when the angle between forearm and upper arm increases. The maximum attenuation difference was 4.2 dB and 4.7 dB in the capacitive coupling and galvanic coupling methods respectively when the joint angle changed from 45 to 180 degrees and the linear distance between transmitter and receiver electrodes was 15 cm. Capacitive coupling was more sensitive to limb joint position, but galvanic coupling was more dependent on body composition (intra subject variability).