Wireless Channel Characterization for UWB Communication in Capsule Endoscopy

Since its invention in the early 1990s the technology behind capsule endoscopy has been making rapid progress. The emergence of high-resolution miniature video cameras along with other microsensor technology have increased the data rate and power consumption requirements for the next generation of these capsules. These requirements along with other advantages have made the Ultra-Wideband (UWB) technology an attractive candidate for wireless communication with the capsule endoscope. Our objective in this paper is to obtain a statistical pathloss model that effectively captures the impact of the transmitter antenna orientation and various body tissues as the capsule moves along its natural path inside the small intestine. To obtain this model, we have developed a 3D immersive platform including a detailed computational human body and gastrointestinal tract models that allow for an in-depth study of the wireless propagation channel between the capsule and the on-body receivers. Using the immersive platform, we have also developed an innovative methodology that enables judicious placement of the capsule along its natural trajectory inside the small intestine. Using this methodology, we obtain sufficient number of sample measurement points with a balanced transmitter-receiver distance distribution while covering the entire small intestine. The results show the significant impact of the orientation of the capsule antenna on the fading component of the statistical pathloss model. This knowledge is essential to better understand the feasible communication range of the capsule as it traverses the small intestine. Our research also provides further information on the time domain characteristics and multipath propagation for the UWB communication channel with a capsule endoscope. We show that the time domain channel responses typically consist of very few noticeable delayed paths. We also conjecture that the more feasible frequency range within the unlicensed UWB spectrum for communication with a capsule endoscope is 3.1 GHz to 4.1 GHz.