## 5 Conclusions  
This study aimed to explore the implementation and performance evaluation of a pioneering Quadrature Chaos Shift Keying (QCSK) chaotic communication system tailored for Internet of Things (IoT) applications. This innovative system leverages chaotic synchronization and quadrature modulation. The core component is the Colpitts chaotic oscillator operating within a drive-response configuration, enhancing the communication system's security at the physical layer. The Colpitts oscillator offers engaging characteristics such as a wide spectrum, noise-like waveform, narrow cross-correlation function, synchronization capability, and sensitivity to initial conditions, all while maintaining system determinism. Comprehensive simulation and experimental studies were conducted to analyze the behavior of the Colpitts chaotic oscillator with a fundamental frequency of 96.86 kHz. The simulation was accomplished in the LTspice environment, while prototype measurements were performed using Analog Discovery Pro. Chaotic signals were processed in MATLAB for both studies. In the simulation, chaotic behavior was achieved using the same system parameters as in the original study, except reducing the values of \(C_{1}\), \(C_{2}\), and \(L_{1}\) by 10 times to achieve a higher fundamental frequency. The design of the [PERSON] chaos oscillator prototype was modified by adding two variable resistors for tuning. Both simulation and prototype results confirmed the characteristic chaotic dynamics of the [PERSON] chaos oscillator, and synchronization in the drive-response system was successfully established. The comparison of signal spectra and construction of cross-correlation functions further validated the generation of chaotic signals, as confirmed by the Z1 TEST. Figure 12: BER curves of QCSK communication system, where blue curve represents system’s noise immunity, when \(V_{\text{C1}}\) is employed as synchronization signal and red curve represents system’s noise immunity when \(V_{\text{C2}}\) is employed as synchronization signal. The evaluation of noise immunity in the QCSK data transmission system within the AWGN channel revealed the influence of synchronization signal properties from the chaos oscillator on error probabilities. This study demonstrated superior performance for the QCSK communication system when VC1 was employed as the synchronization signal. Compared to previously explored TR-DCSK, FM-CSK, and QCPSK digital communication systems, the QCSK system, built on the Colpitts chaos oscillator, exhibited enhanced noise immunity during data transmission. Its simple design and improved security capabilities position this system as a promising solution for strengthening IoT communication security. In the future, the investigation of the QCSK chaotic communication system can be expanded to practical applications in real-world IoT sensors. Deploying the system in real-world scenarios will offer vital information about its performance, resilience, and robustness. Experiments using real IoT devices will provide a more in-depth knowledge of the system's behavior in dynamic and diverse settings. Furthermore, additional optimizations and enhancements might be explored to improve the system's efficiency and handle any issues that arise during real-world deployments. Conceptualization, A.L. ; Methodology, F.C. and D.K. ; Software, R.B. and F.C. ; Validation, D.C. and R.B. ; Investigation, D.C.; Resources, R.B. ; Writing--original draft, D.C.; Writing--review & editing, D.K. and A.L. ; Supervision, D.K. ; Funding acquisition, A.L. All authors have read and agreed to the published version of the manuscript. This work has been supported by the European Social Fund within Project No.