## 6 Conclusions  
In this study, a small-scale lighting system was developed to emulate a typical indoor environment, exploiting both the spatial distribution of light and the spectrum for VLC. A semi-spherical array of photodiodes was created using 3D printing and mounted on a surface. Signal conditioning was performed using a custom-engineered circuit board and analog data from the detectors were digitized by the TM4C1294 NCPDT microcontroller; after that, the obtained data were efficiently transmitted to a computer via Ethernet.  
Data processing was carried out using Matlab, achieving 99% efficiency for decoding the received frames. Additionally, it successfully estimated the position and orientation angle, with an average error of 3 cm and 10 deg, respectively. Although these results were obtained in a small system, the absolute error is expected to hold for larger setups. The main limitation of the system will be the power of the transmitters, since the receiver power may not be enough to reach the side photodiodes in order to perform angle detection correctly. Additionally, a distance estimation method using side photodiodes was implemented to improve positioning in challenging environments where the top photodiode could not detect at least three lights. This approach allowed for detection from multiple angles, enabling an increase in the system's reach, resulting in an average error of 6.38 cm. These results highlight the potential of the proposed approach for effective indoor positioning and orientation applications such as locating autonomous robots in a warehouse or supermarket.  
It was found that the system is very robust to reflections since the algorithm searches for the photodiode with the maximum power considering its neighboring photodiodes. However, in the presence of obstacles, the behavior of the system in its current state is seriously affected. This issue may lead to detecting a false maximum power photodiode, or, even if a lateral photodiode is obstructed, the angle calculation may be degraded to such an extent that the resulting angle cannot be utilized.  
Conceptualization, J.B.A. and J.C.T.Z.; formal analysis, J.S.B.; investigation, J.B.A.; methodology, J.C.T.Z.; software, J.S.B. and J.B.A.; supervision, M.M.C.; validation, M.M.C. and J.S.B.; visualization, M.M.C. and J.S.B.; writing--original draft, J.C.T.Z. and C.I.d.V.M.; writing--review and editing, J.B.A., M.M.C., J.S.B. and C.I.d.V.M. All authors have read and agreed to the published version of the manuscript.  
This work is supported by the following research projects funded by MICIU/AEI/10.13039/501100011033; ViDiT (TED2021-129869B-I00), also funded by NextGenerationEU/PRTR, and, for the work of [PERSON], [PERSON] RYC2022-036053-I, also funded by FSE+.  
The data generated in this study are not relevant for the replication of the experiment and, therefore, have not been made publicly available. However, any request for additional information will be considered by the corresponding author.  
The authors declare no conflicts of interest.  
\begin{table}
\begin{tabular}{c c c c} \hline
**Number of Luminaries** & **X Axis (cm)** & **Y Axis (cm)** & **Position (cm)** \\ \hline L3\({}^{\prime}\)-L2-L4 & 7.42 cm & 0.81 cm & 7.50 cm \\ \hline L4\({}^{\prime}\)-L1-L2 & 2.12 cm & 2.78 cm & 3.95 cm \\ \hline L4\({}^{\prime}\)-L1-L3 & 1.12 cm & 1.53 cm & 2.06 cm \\ \hline L4\({}^{\prime}\)-L2-L3 & 1.25 cm & 2.85 cm & 3.80 cm \\ \hline Mean & 4.61 cm & 3.17 cm & 6.38 cm \\ \hline \end{tabular}
\end{table}
Table 7: _Cont._