Abstract
This paper presents an assessment of the accuracy of cooperative localization of a wireless capsule endoscope (WCE) using radio frequency (RF) signals with particular emphasis on localization inside the small intestine. We derive the Cramer–Rao lower bound (CRLB) for cooperative location estimators using the received signal strength (RSS) or the time of arrival (TOA) of the RF signal. Our derivations are based on a three-dimension human body model, an existing model for RSS propagation from implanted organs to the body surface and a new TOA ranging error model for the effects of non-homogeneity of the human body on TOA of the RF signals. Using models for RSS and TOA errors, we first calculate the 3D CRLB bounds for cooperative localization of the WCE in three major digestive organs in the path of GI tract: the stomach, the small intestine and the large intestine. Then we analyze the performance of localization techniques on a typical path inside the small intestine. Our analysis includes the effects of the number of external sensors, the external sensor array topology, number of WCEs used in cooperation and the random variations in the transmitted power from the capsule.
Highlights
In the past decade, miniaturization and cost reduction of semiconductor devices have allowed the design of small, low cost computing and wireless communication devices used as sensors in a variety of popular wireless networking applications and this trend is expected to continue in the few decades [1]
This paper presents an assessment of the accuracy of cooperative localization of a wireless capsule endoscope (WCE) using radio frequency (RF) signals with particular emphasis on localization inside the small intestine
We investigated the potential accuracy limits for received signal strength (RSS) and time of arrival (TOA) based RF localization for the wireless WCE as it travels inside the human GI tract using the Cramer–Rao lower bound (CRLB)
Summary
Miniaturization and cost reduction of semiconductor devices have allowed the design of small, low cost computing and wireless communication devices used as sensors in a variety of popular wireless networking applications and this trend is expected to continue in the few decades [1]. This paper provides a unified framework and methodology for calculation of the CRLB for comparative performance evaluation of the RSS- and TOA- based cooperative localization with multiple capsules operating inside the GI tract. We apply this analytical framework to compare the performance of the RSS- and TOA-based cooperative localizations using multiple capsules in the three major organs of the GI tract as well as to assess the accuracy of these techniques as the WCE moves along the complex path of movements inside the small intestine. 3, using the capsule movement and body mounted sensor locations in our scenario and the ranging error models, we derive a universal CRLB for cooperative performance evaluation of cooperative RSSand TOA-based WCE localization techniques and the localization bound with randomness in the transmitted power.
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