# A Python-Based Indoor Channel Model with Multi-Wavelength Propagation for Color Shift Keying
## 7 Conclusions  
The primary contribution of this work is the development and validation of a novel open-source Python-based indoor channel model for CSK in visible light communication systems. The model successfully calculates the received power at each color photodetector, along with the inter-channel interference and lighting parameters within an empty rectangular room, assuming Lambertian reflective walls. Validation against a reference model demonstrated a relative error of less than 3% across four indoor configurations, with enhanced performance in handling high-order reflections (up to ten orders). Notably, for environments with high-reflectance walls, the model revealed that higher-order reflections substantially impact the received power, contributing to an increase in detected power of up to 22% in certain configurations, which emphasizes the need to account for these components in highly reflective environments.  
The model also enables a detailed cross-talk analysis across different photodetector positions, showing significant variations in inter-channel interference, particularly in configurations where the photodetector was positioned near walls. These findings are essential for optimizing CSK constellations to minimize symbol error rates while maintaining acceptable illumination quality. Moreover, the model simulated the spectral responses of commercial LEDs and photodetectors, capturing key illumination challenges such as non-uniform illuminance, low color rendering index (CRI), and saturated perceived color when using the IEEE 802.15.7 standard constellation. Addressing these issues requires optimizing the CSK constellation design, particularly to improve color quality and communication performance.  
In terms of communication performance, the model simulated an AWGN channel to estimate the symbol error rate (SER) under realistic noise conditions. The results showed that for a target SER of approximately \(10^{-5}\), the required luminous flux increased significantly as the receiver was moved away from the light source, demonstrating the spatial sensitivity of the system. The findings also suggested that optimizing the receiver's design through techniques such as optical concentration can reduce the required luminous flux while maintaining adequate communication quality. Additionally, the model's flexibility allows for the simulation of custom constellation designs, offering a powerful tool for optimizing CSK systems to meet both communication and lighting performance goals in various indoor environments.  
Conceptualization, J.F.G. and J.M.Q.; methodology, J.F.G., D.S. and J.M.Q.; software, J.F.G. and D.S.; validation, J.F.G., D.S. and J.M.Q.; formal analysis, J.F.G.; investigation, J.F.G.; resources, J.M.Q.; data curation, J.F.G.; writing--original draft preparation, J.F.G.; writing--review and editing, J.F.G., D.S. and J.M.Q.; visualization, J.F.G.; supervision, D.S. and J.M.Q.; project administration, J.M.Q.; funding acquisition, J.M.Q. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Colombian Ministry of Science, Technology, and Innovation (_Ministerio de Ciencia, Tecnologia e Innovacion--MINCIENCIAS_) and the Universidad Nacional de Colombia, under the framework of the Bicentennial Doctoral Scholarship for Excellence, as defined in Article 45 of Law 1942 of 2018, Bogota, Colombia.