Channel Variability in Human Body Communication with External Objects in Body Resonance Region

The channel variability of human body communication (HBC) in Electro-Quasistatic (EQS) region and the influence of the parasitic paths by external objects and inter-body coupling have been widely explored. However, channel variability of HBC in the body resonance (BR) region is hardly studied. In the BR region, the wavelength is comparable to the dimension of the human body which starts to resonate and act as an antenna. Electromagnetic (EM) wave patterns are generated from the transmitter dipole and formed on the human body. The external objects causing some parasitic paths influence the patterns and the channel gain. This paper explores the influence of external objects on the HBC channel gain in the BR region for the first time. Firstly, the relevant EM theories and corresponding simulation setup and results are introduced. Following that, the experiment setup and results are described and analyzed. The results show that putting the arms on the table can lead to a notch frequency shift by 77∼100 MHz and channel gain change by -17∼20 dB depending on different angles and frequencies. The channel gain variation before the notch is small, enabling stable high-speed communication.