## 5 Conclusions  
In this paper, a novel wide-range and precise solution for an indoor positioning system was proposed, which utilized LED lights as a transmitter and a mobile image sensor as a receiver to identify lighting information. Utilizing the rolling shutter mechanism of a smartphone-embedded CMOS image sensor enhanced the data rate, thereby improving the decoding accuracy for minimizing the positioning error. The existing LED lighting infrastructure was effectively used in the proposed positioning system for the transmission of coordinate information with a high data rate by the FSOOK modulation scheme. Therefore, it results in a system that is cost-effective and easy to implement. To cover a large positioning area, the multilateration positioning method was proposed, which can locate a static mobile camera image sensor with centimeter-level positioning accuracy by receiving multiple LED light signals simultaneously. The accuracy of the proposed system is sufficient for localization applications for future large-scale indoor environments. Additionally, the proposed system achieved a 100% decoding rate with respect to the vertical up to a distance of 1.5 m and it remained at 80% until the distance was 1.78 m. The decoding accuracy of the horizontal distance from directly below to the LED was 100%, and it was gradually reduced when the image sensor moved far away from the direct incident place of the LED to the edge of the LED light. The performance of the proposed system was compared with those of other emerging indoor positioning technologies.  
Conceptualization, W.-Y.C.; system methodology, M.H.R. and M.A.S.S.; software, M.H.R.; validation, W.-Y.C. and M.H.R.; formal analysis, M.H.R. and M.A.S.S.; investigation, W.-Y.C., M.H.R. and M.A.S.S.; data curation, M.H.R.; writing--original draft preparation, M.H.R.; writing--review and editing, W.-Y.C., M.H.R. and M.A.S.S.; supervision, W.-Y.C. All authors have read and agreed to the published version of the manuscript.  
The study was supported by a National Research Foundation of Korea (NRF) grant funded by the Korea Government (No. 2020R1A4A1019463).  
Not applicable.  
The data presented in this study are available on request from the corresponding author.  
The authors declare no conflict of interest.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Ref.** & \
\begin{tabular}{c} **Positioning** \\ **System** \\ \end{tabular} & **Experiment/Simulation** &
\begin{tabular}{c} **Experiment Testbed** \\ **Size** \\ \end{tabular} & **Accuracy** & **Number of LEDs** \\ \hline
[31] & Image & Experiment & 1.4 \(\times\) 1.4 \(\times\) 1.6 m & X:3 cm Y: 7 cm & 3 LEDs \\ \hline
[11] &
\begin{tabular}{c} AoA 1 + \\ Triangulation \\ \end{tabular} & Experiment & 0.71\(\times\) 0.74 \(\times\) 2.26 m & 10 cm & 5 LEDs \\ \hline
[32] &
\begin{tabular}{c} AoA + \\ Trilateration \\ \end{tabular} & Experiment & 1.0 \(\times\) 1.0 \(\times\) 2.4 m & \textless{}10 cm & 1 LED \\ \hline
[22] & RSS 1 + AoA & Simulation & 1.8 \(\times\) 1.8 \(\times\) 3.5 m & 15.6 cm & 4 LEDs \\ \hline
[33] & AoA + Image & Experiment & 1.8 \(\times\) 1.8 \(\times\) 3.5 m & \textless{}40 cm & 9 LEDs \\ \hline Proposed &
\begin{tabular}{c} Image + \\ Multilateration \\ \end{tabular} & Experiment & 2.5 \(\times\) 4.5 \(\times\) 2 m & 2.41 cm & 6 LEDs \\ \hline \hline \end{tabular}  
* Angle-of-arrival (AoA), received-signal-strength (RSS).  
\end{table}
Table 3: Comparison of the proposed system with other VLC- and image sensor-based positioning systems.