An ultra wideband communication channel model for capsule endoscopy

Capsule endoscopy is an increasingly popular alternative to a tube-based endoscope used in diagnosing gastrointestinal diseases. It enables the inspection of areas that are not easily accessible using traditional endoscopy and reduces patient discomfort. In addition to transferring high-capacity demanding image data, the capsule´s wireless interface must provide a wireless link that enables real-time positioning and tracking of the capsule. Ultra wideband (UWB) interfaces have great potential for the communication links of this application due to their inherent low power consumption, high transmission rates, accurate localization properties and simple electronics. However, accurate knowledge of the propagation channel is essential for efficient design of such UWB wireless communication systems. This paper presents a channel model for the propagation of a UWB pulse in the digestive tract in the 3.4-4.8 GHz frequency band. For the development of this model, numerical electromagnetic (EM) simulations were conducted using a voxel anatomical model that includes the dielectric properties of human tissues; using this EM simulator the channel responses of many in-body probes were computed. Based on the analysis of the obtained data we provide the mathematical expressions to calculate the average path loss and its distribution at several receiver locations surrounding the abdomen. Our proposed model gives designers an important tool that approximates well the digestive tract´s in-body channel properties, thereby eliminating the need for time consuming and complex numerical simulations.