On effect of transmit power variance on localization accuracy in wireless capsule endoscopy

This paper presents an analysis on localization accuracy of a capsule used for wireless endoscopy application when there are random variations in transmit power of sensor nodes. We use a three-dimensional human body model and the log normal model for Received Signal Strength (RSS) radio propagation from the implant to the sensor nodes on the body surface to find accuracy bounds in three digestive organs, namely stomach, small intestine, and large intestine, which form the human Gastro-Intestinal (GI) track. The analysis is done using Bayesian Crameŕ-Rao bound assuming that the transmit power is random process with known prior distribution. We provide analysis of the factors affecting localization accuracy including various organ environment, external sensor array topology. The simulation results show that the capsule localization inside large intestine is affected the most with the transmit power randomness, while wireless capsule can be localized with best accuracy inside the small intestine. Finally, we propose an approach to improve the attainable accuracy bounds.