# Resource Allocation in Downlink VLC-NOMA Systems for Factory Automation Scenario
## 5 Conclusions  
In this study, a downlink VLC-NOMA system was investigated in a factory automation scenario. A DNN-based power-allocation scheme (DBPA) and a priority-based user-pairing (PBUP) scheme were proposed to improve the reliability of the system. In terms of the minimal average BER, DBPA was compared with fixed power allocation, FTPC, and FBL-based algorithms. DBPA exhibited the lowest average BER among the power allocation algorithms. Thus, DBPA can be applied to VLC-NOMA systems to improve reliability. PBUP in the VLC-NOMA system was compared with DMS in the VLC-OMA system and NLUPA in the VLC-NOMA system. The evaluation results show that the VLC-NOMA system with the proposed DBPA and PBUP outperforms VLC-OMA with DMS and VLC-NOMA with NLUPA in the factory automation scenario. Future work will consider multiple LEDs to handle multiple nodes to improve reliability in factory automation scenarios.  
\begin{table}
\begin{tabular}{l c c c c c c c c c c} \hline \hline
**TX SNR (dB)** & **40** & **41** & **42** & **43** & **44** & **45** & **46** & **47** & **48** & **49** & **50** \\ \hline OMA with DMS (\%) & 34.99 & 35.21 & 35.26 & 35.3 & 35.3 & 35.3 & 35.3 & 35.3 & 35.3 & 35.3 \\ \hline NOMA with PBUP (\%) & 34.23 & 42.34 & 49.14 & 54.67 & 59.64 & 64.11 & 68.06 & 71.9 & 73.47 & 74.49 & 74.49 \\ \hline NOMA with NLUPA (\%) & 28.49 & 36.6 & 43.34 & 48.7 & 54.21 & 58.77 & 62.45 & 66.46 & 68.02 & 68.81 & 69.01 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Packet delivery ratio.  
\begin{table}
\begin{tabular}{l c} \hline Number of nodes & 10 \\ \hline X-axis of nodes & 4\(\sim\)6 m \\ \hline Y-axis of nodes & 4\(\sim\)6 m \\ \hline Z-axis of nodes & 1.5 m \\ \hline Released times & 10\(\sim\)100 ms \\ \hline Computing times & 10\(\sim\)50 ms \\ \hline Deadlines & 10\(\sim\)100 ms \\ \hline Periods & 10\(\sim\)200 ms \\ \hline Superframe size & 250 ms \\ \hline Simulation time & 100,000 ms \\ \hline Bits per packet & 32 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Scheduling parameters.  
\begin{table}
\begin{tabular}{l c c} \hline \hline  & **OMA with DMS** & **NOMA with PBUP** & **NOMA with NLUPA** \\ \hline Missed deadlines & 4844 & 1910 & 2320 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Missed deadline comparisons.  
**Author Contributions:** Conceptualization, W-J.R. and J.-W.K.; methodology, W-J.R.; software, W-J.R.; validation, W-J.R. and J.-W.K.; formal analysis, W-J.R.; investigation, W-J.R.; resources, W-J.R. and J.-W.K.; data curation, W-J.R.; writing--original draft preparation, W-J.R. and J.-W.K.; writing--review and editing, D.-S.K.; visualization, W-J.R.; supervision, D.-S.K.; project administration, D.-S.K. All authors have read and agreed to the published version of the manuscript.  
This work was supported in part by the Ministry of Science and ICT (MSIT), Korea, under the Grand Information Technology Research Center Support Program, supervised by the Institute for Information and Communications Technology Planning and Evaluation (IITP), under Grant IITP-2022-2020-0-01612; in part by the Priority Research Centers Program under Grant 2018R1A6A1A03024003; and in part by the Basic Science Research Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Education, Science and Technology, under Grant 2022R1 IIA1A01069334.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Data sharing is being prepared.  
**Conflicts of Interest:** The authors declare no conflict of interest.