## 5 Conclusions  
This paper highlighted the importance of the impact of LED lamp arrangements on DL \(SNR\) and illuminance uniformities. Accordingly, a heuristic design formula for obtaining optimal coordinates for generalized room dimensions and minimizing the fluctuations in \(SNR\) is outlined in the paper. It was shown that, by purposely relocating the transmitters around corners of the room according to the proposed placement technique, the \(SNR\) fluctuations can be reduced by \(\sim\)54% and the illuminance uniformity can be improved up to 102% when compared to the traditional approach. Moreover, the effects of low transmit power on DL communication were also presented. It was revealed that, for a worst-case scenario, where illuminance was lower than 100 lux, the \(SNR\) of the proposed scheme remains above the threshold level that is required to achieve a BER of \(10^{-9}\), which is mandatory for achieving reliability in healthcare applications. Furthermore, the use of principle of reciprocity was demonstrated and validated using a single transmitter and single receiver scenario with the inference that DL uniformity analysis can be suitably used to estimate the UL \(SNR\) uniformity. Finally, the effects of UL parameters, like low transmit power, responsivity, and reflectivity, were analyzed to account for the change in wavelength of operation. It was concluded that \(SNR\) uniformity does not change with low power and responsivity, whereas it improves with increase in reflectivity. The future work includes the experimental verification of the proposed scheme in a realistic indoor environment. Moreover, the characterization of the channel impulse response for various receiver orientations in presence of human body, measurement of SNR in various environment, and demonstration of UL and DL OBAN communication will be carried out experimentally. Based on the measurements, further improvement in the simulation environment will be considered.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**CLQ**} & \multicolumn{3}{c}{**Proposed CoIQ**} \\ \cline{2-7}  & \multicolumn{6}{c}{**Deviation in SNR (dB)**} \\ \hline Room Size & \(P_{t}=90\) & \(\rho=0.9\) & \(\gamma=1.01\) & \(P_{t}=90\) & \(\rho=0.9\) & \(\gamma=1.01\) \\ (m\({}^{3}\)) & mW & \(\rho=0.9\) & A/W & mW & \(\rho=0.9\) & A/W \\ \hline
6.6 \(\times\) 6.6 \(\times\) 3 & 1.87 & 1.75 & 1.87 & 1.11 & 1.06 & 1.11 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Uplink performance of CLQ and CoIQ for given room dimensions  
Figure 10: Reciprocity Principle: SNR distributions for DL and UL connections.  
**Author Contributions:** Conceptualization, K.M. and V.J.; Methodology, K.M., V.J. and S.R.; Validation, V.J., S.R., and M.D.; Writing--Original Draft Preparation, K.M.; Writing--Review & Editing, V.J., M.D., S.C. and S.R.; Supervision, V.J., M.D., and S.C. All authors have given approval for the final version of the manuscript.  
**Funding:** This research is supported by the: (i) Yayasan Universiti Teknologi PETRONAS (YUTP-FRG) under Grant 015 LC0-106 and (ii) Centre for Graduate Studies (CGS), Universiti Teknologi PETRONAS, Malaysia.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Not applicable.  
**Acknowledgments:** The authors would like to acknowledge the financial support provided by the Yayasan Universiti Teknologi PETRONAS (YUTP-FRG) under Grant 015 LC0-106 and the Centre for Graduate Studies (CGS), Universiti Teknologi PETRONAS, Perak, Malaysia.  
**Conflicts of Interest:** The authors declare no conflict of interest.