KEYWORDS: Receivers, Mathematical modeling, Transmitters, Signal processing, Detection and tracking algorithms, Radio propagation, Non-line-of-sight propagation, Algorithm development, Received signal strength, Transceivers
In this paper we consider the problem of tracking the real-time positions of a diagnostic capsule in the gastrointestinal
(GI) tract. Our solution is a fully developed estimation algorithm that utilizes radio frequency signals converted to
voltage on the received signal strength indicator (RSSI) output of an array of transceivers. We employed a modified
form of the traditional radio-map based deterministic model that requires an estimate of initial position vector. Data
capture was implemented with commercial off-the-shelf transceivers featuring RSSI outputs. At the intermediate
processing stages, trilateration was employed as a mathematical tool to determine the approximate 2-D coordinates of
unknown capsule locations by linearizing the resulting equations. This approach facilitates a PC-based implementation
of fully automated real-time position measurements by eliminating the need to measure angles. In the final algorithm
based on non linear least squares approximations, the Newton's iteration of the resulting Jacobian matrices were used to
generate a more accurate position coordinates. Test Results from laboratory experiments demonstrate the accuracy of the
solution in the centimeter range. This results in a position tracking measurements with an average value error of less than
25%. This kind of results guarantees that our solution can be adapted into telemetry capsules for use in diagnosing
intestinal malfunctions.
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