Interference Reduction Modulation Based on Chirp Spread Spectrum for Capsule Endoscopy

Abstract

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 (CSS-DBPSK) 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.

Class of novel broadband chaos‐based coherent communication systems

“…The ASK–OOK communication systems find use in radio frequency identification (RFID) devices as well as in medical applications such as endoscopy [31] among others. However, the conventional narrowband sine‐based ASK–OOK systems [28] are highly sensitive to interference [6, 31]. In contrast to narrowband signals, broadband signals offer better resistance to interferences.…”

“…In contrast to narrowband signals, broadband signals offer better resistance to interferences. For instance, it was shown in [31] that broadband chirp signals enhanced the interference resistance of OOK systems in a human body channel. Therefore, the proposed chaos‐based ASK–OOK system holds promise in applications where inherent interference resistance is of primary importance.…”

“…Finally, another important contribution of this paper is that it shows that although the novel broadband chaos‐based systems have lower spectral efficiency than their conventional narrowband counterparts, they also have lower relative transmitted peak power per Hz and may thus find use in low probability of intercept/low probability of detection (LPI/LPD) [28] applications. In contrast to narrowband signals, broadband signals are also inherently more resistant to interferences [6, 31]. Therefore, the broadband nature of the chaos‐based signals makes the proposed communication systems of interest in applications where interference mitigation is of importance.…”