On the Placement of On-Body Antennas for Ultra Wideband Capsule Endoscopy

Ultra wideband communication is proposed as an alternative to increase the data rate for in-body to on-body communication compared with existing narrowband standards. However, up to now, it is unknown, which maximum data rates can be achieved in this environment. The channel capacity is a theoretic tool that allows quantifying this limit. In a frequency-dependent environment like the human body, it is necessary to know the frequency dependence of the communication channel to calculate the channel capacity. As there are no reproducible models available in literature that enable the calculation of the channel capacity, we propose a new channel modeling technique based on a plane wave propagating through a multi-layered dielectric. From this simplified model, the frequency-dependent path loss for various in- and on-body locations can be calculated analytically. Thus, the channel capacity can be determined. In addition, this approach offers the possibility to determine the optimum position of multiple receive antennas on the abdominal surface. Results show that a single receive antenna gives nearly no improvement compared to existing standards. However, if the number of antennas is increased to 5, the 10%-outage capacity can be improved by several orders of magnitude.