Interference Reduction Modulation Based on Chirp Spread Spectrum for Capsule Endoscopy

In this paper, chirp spread spectrum (CSS) based modulation schemes for capsule endoscopy applications are proposed. The On-Off-Keying (OOK) technique has been conventionally used for the capsule endoscopy applications, but it is known to be susceptible to narrow-band interference such as TV signals. In order to enhance robustness to interferences, we propose two CSS based modulation schemes which are chirp spread spectrum differential binary phase shift keying (CSSDBPSK) and chirp spread spectrum on-off keying (CSS-OOK). The CSS-DBPSK scheme performs better than the CSS-OOK scheme in terms of BER, but it has high implementation complexity due to the strict synchronization requirement. On the other hand, the CSS-OOK scheme has both low receiver complexity and comparable BER performance. A key contribution of this paper is to use a low complexity chirp spread spectrum technique for interference mitigation in capsule endoscopy. A human body channel model is used in the simulations. Simulation results show that the BER performance of the CSS-OOK modulation is in between the CSS-DBPSK and the OOK schemes. We will show that the CSS-OOK modulation is a practical solution that achieves good compromise between the interference robustness and the receiver complexity.