## 2 MISO VLC System Model
This deviation causes signal fluctuations among the room, leading to a largely varying SNR and link unreliability. On the other hand, the performance of the 4 arrays and 16 arrays models is close under the given parameters. Since the performance of any communication system is limited by its SNR, the received power of the link has to be increased. According to Equations (3)-(5), the received power, \(P_{r}\), depends on many factors, including the receiver's FOV and the transmitter's (LED) half power angle, \(\varnothing_{1/2}\). It can be observed that \(P_{r}\) is inversely proportional with the receiver's FOV and the transmitter's \(\varnothing_{1/2}\). So, in order to increase \(P_{r}\), the values of these two parameters should be decreased. To analyze the effect of reducing the receiver FOV, the simulations in the previous section are repeated. Instead of using FOV = 70\({}^{\circ}\), a receiver FOV of 60\({}^{\circ}\) then 50\({}^{\circ}\) are used. Table 3 shows the maximum received power in dBm for the first reflection paths and the total received power for the three cases under the three different values of the receivers FOV. The values of the maximum first reflected path received power do not vary greatly for each case; however, the power distribution pattern changes significantly, as shown in Figure 3. \begin{table}
\begin{tabular}{c c c c} \hline \hline \(P_{r}\) (dBm) & 4 Arrays Model & 9 Arrays Model & 16 Arrays Model \\ \hline Average & 1.62 & 1.72 & 1.48 \\ Minimum & \(-\)1.51 & \(-\)2.09 & \(-\)1.30 \\ Maximum & 2.57 & 3.75 & 2.53 \\ STD & 0.91 & 1.33 & 0.82 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Power received for different LED arrangements. Figure 2: Received power for **(a)** the 4 arrays model, **(b)** the 9 arrays model, and **(c)** the 16 arrays model. In Figure 3, the FOV is fixed to 50\({}^{\circ}\), and the first reflection path and the total received power are plotted for each case. It is clear that the area in the middle of the room starts receiving almost zero power from the first reflection path, and as the FOV gets smaller, the area gets larger. Moreover, the received power pattern becomes less uniform as the FOV gets smaller, causing the case of using 9 arrays and 16 arrays to have an advantage over the case of using 4 arrays. By increasing the number of transmitters in the room, the power becomes more evenly distributed. Hence, even if a receiver of narrow FOV is used, the power pattern will still maintain its uniformity. However, most practically used PIN photodiodes (receivers) such as those in References [17; 18; 19] have FOV angles of about 65, thus this study is not extended for FOV angles less than 50\({}^{\circ}\). The transmitter half power angle (i.e., semi-angle at half luminance), \(\varnothing_{1/2}\), is the angle from the axis perpendicular to the LED by which the luminous intensity is only 50%. This angle is the viewing angle (i.e., the half-intensity beam angle). Its value is about 10-12\({}^{\circ}\) with no diffusion, such as in Reference [20], which is controlled by the reflector cup (that surrounds the LED chip) properties. However, this angle reaches up to 70\({}^{\circ}\) at maximum diffusion, as described in many scenarios [13; 14; 15]. To analyze the effect of reducing the transmitter half power angle \(\varnothing_{1/2}\), the simulations using the system parameters given in Table 1 are repeated, firstly by considering the case of a non-diffused LED with \(\varnothing_{1/2}=10^{\circ}\) instead of \(\varnothing_{1/2}=70^{\circ}\). The tremendous difference is clear in Figure 4, where the received power pattern has changed greatly when compared to Figure 3. The patterns have less uniformity and the location and number of transmitters are now visible in the surface plot. The received powers are recalculated in Table 4 for \(\varnothing_{1/2}=10^{\circ}\). Figure 3: The first reflection path received power (dBm) at field-of-view (FOV) = 50\({}^{\circ}\) for (**a**) the 4 arrays model, (**b**) the 9 arrays model, and (**c**) 16 arrays model.