# Optical Camera Communication as an Enabling Technology for Microalgae Cultivation +
## 5 Results  
### Plant Distribution Study  
Table 4 shows the metrics calculated for each case. For illustrative purposes, Figure 7 plots every case in the space defined by the proposed multidimensional metric \(F\). The first configuration, Case I, has a relatively low SUR. Approximately only four percent of the available space is utilised for harvesting. Therefore, this proposal should be discarded, even though the conditions for establishing a communication link are practically ideal. This SUR could be increased if a greater \(AoV_{V}\) were selected. Increasing \(AoV_{V}\) causes the \(FoV_{H}\) to expand, and therefore, the camera can get closer to the shelf, reducing the distance considerably and minimising the required space. However, increasing \(AoV_{V}\) without limits would intensify the distortion effects introduced by the lens, pending the vertical lines in the image (barrel distortion), especially for fish-eye lenses. This distortion would not modify the shape of the symbol bands. The symbol bands will always be horizontal (or vertical) straight lines because they result from the RS acquisition method regardless of the lenses' optics properties. However, it does affect the containers' shape, reducing its vertical size. Furthermore, this non-linear distortion cannot be mitigated using image processing techniques; doing so would reflect the distortion on the signal bands. In Case III, however, just the opposite happens. The SUR is almost four times higher than in Case I. However, the optical received power from the most distant containers is so low that it reduces the effective data rate and increases the complexity at reception. This reveals the importance of the camera viewing view. Those acute view angles will significantly affect the total received optical power. They will make it difficult not only to establish the link, but also to estimate the microalgae culture's biomass precisely. In conclusion, Case II becomes the optimal choice for this application. It is the solution that achieves a balance in all parameters and has greater replicability. This replicability allows easily creating new plant distributions, such as the one shown in Figure 7. In that example, it is shown how just by adding a second camera on the original shelf and \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Case** & \(V_{\text{room}}\) (**m2**) & \(V_{\text{cont}}\) (**m2**) & \(h_{\text{min}}\) & \(L(\theta,\varphi)\) \\ \hline I & 23.31 & 0.81 & 0.5 & 0.95 \\ II & 9.81 & 0.81 & 0.5 & 0.65 \\ III & 11.68 & 1.62 & 0.5 & 0.12 \\ \hline
**N** & & **SUR** & & **Q** \\ \hline
12 & 0.035 & & 0.47 & \\
12 & 0.083 & & 0.32 & \\
24 & 0.139 & & 0.05 & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Metric values obtained for the three arrangements. Figure 7: Illustration of the results of the plant distribution study. (**a**) Space generated by the multidimensional metric F; (**b**) example of Case II’s replication process. installing a new identical rack that holds the first camera, a corridor similar to Case III can be created. Hence, this configuration makes better use of space at the expense of adding a single low-cost camera. In that case, both the SUR and \(N\) double their original values, maintaining the communication performance. However, despite this being the chosen solution, there is still a discussion to be made. The fact that the camera scans only a fraction of the first containers and performs the full scan of those that are further away (due to the image's viewing perspective) gives rise to new challenges. For example, the signal-to-interference-plus-noise ratio (SINR) is different for each container, especially under the presence of tiny air bubbles in motion within the reactor, which are utilised generally to aerate the organisms and induce a continuous movement. The projection of these small air bubbles increases in size for the nearest containers, generating more noticeable interference phenomena.