# Optimization Scheme for Modulation of Data Transmission Module in Endoscopic Capsule
## 1 Introduction
Differential chaos shift keying (DCSK) is a promising modulation technique known for its low cross-correlation, low power consumption, exceptional autocorrelation, and broadband spectral characteristics. Therefore, it can have strong robustness against non-stationary environments such as multipath interference without the need for filtering and equalization [14]. However, these advantages come at the cost of reduced system spectral efficiency (SE). To enhance the transmission rate, the implementation of the M-ary DCSK (M-DCSK) method becomes necessary. Several M-DCSK systems have been developed to achieve high data rates by combining index modulation (IM) with traditional binary DCSK [15; 16; 17; 18; 19]. Numerous methods are using the coded-shift DCSK (CS-DCSK) based on Walsh codes, introduced in [20]. Subsequent developments have led to the generalized CS-DCSK, high-data-rate CS-DCSK, and CS-DCSK with code index modulation, targeting high-speed systems, as presented in [21; 22; 23], respectively. These schemes offer a notable improvement in spectral efficiency by enabling the transmission of multiple bits per symbol period. Additionally, a MIMO M-ary DCSK scheme was proposed in [24]. Despite these advantages, the complexity of these schemes remains relatively high. Additionally, several schemes based on M-ary phase shift keying (MPSK) and M-ary quadrature amplitude modulation (MQAM) for DCSK have been proposed [25], with a focus on optimal constellation design. These schemes make use of a reference chaotic signal in the information-carrying part [26], which is modulated by MPSK and MQAM using M-ary symbols. Furthermore, an M-DCSK system employing an MPSK constellation [27], based on orthogonal chaotic frequency shift keying (QCSK) [28], has been proposed, demonstrating improved bit error rate (BER) performance. In recent years, WBANs have become a crucial part of modern healthcare systems, particularly for applications such as health monitoring, wearable sensors, and medical implants. These systems typically need effective communication methods to transmit critical biomedical data. Among various modulation techniques, DCSK has emerged as a promising approach due to its robustness against noise, interference, and fading, which are common in the in-body communication channels. [PERSON]. [29] demonstrated that chaotic secure communication systems, such as those using DCCK, offer robust security and low power consumption, making them ideal for WBAN applications. Furthermore, [PERSON] and [PERSON] provided an in-depth performance analysis of DCCK in WBANs, showing its potential in achieving high reliability while maintaining low energy consumption, even in complex wireless environments [30]. In addition to performance improvements, the security of transmitted data in WBANs is crucial due to the sensitive nature of health-related information. [PERSON]. [31] proposed a secure communication framework based on DCCK modulation, emphasizing its ability to safeguard data transmission from potential eavesdropping. Their work highlights the key advantage of chaotic modulation in WBANs, offering both privacy and communication efficiency. Furthermore, [PERSON]. [32] explored the design and performance of DCCK in WBANs, showing that it effectively reduces bit error rates and enhances the stability of data transmission in noisy environments. Interbody (In-body) communication, where signals travel through or around the human body, presents several unique challenges such as high attenuation, multipath fading, and interference from the body itself. DCSK, which utilizes the chaotic dynamics of a signal for modulation, has demonstrated its potential to handle these challenges effectively. The chaotic nature of the signal offers high resilience to interference and provides enhanced security features, which are vital for medical and health-related applications where data integrity and privacy are crucial.