# A Novel 4 \(\times\) 1 MISO-VLC System with FBMC-OQAM Downlink Signals
## 3 Results and Discussion  
In typical visible-light communication systems, there are two propagation paths between the LED transmitter and the receiver: line of sight (LOS) and non-line of sight (NLOS) [27, 28, 29]. We focus on studying LOS communication in indoor unobstructed spaces. We propose a four-transmitter-one-receiver VLC system, as shown in Figure 5. The optical transmitter comprises four LEDs, and the modulated signals are transmitted through four line-of-sight paths to a receiver on the desk positioned 1 m above the ground. Figure 4: (a) QAM time-frequency characteristics and (b) OQAM time-frequency characteristics. The received optical power \(p_{r}\) at the receiver end can be represented by the following equation:  
\[p_{r}=h_{(0)}p_{t} \tag{2}\]  
In the above equation, \(p_{t}\) represents the optical power emitted by the LED light source, and \(h_{(0)}\) represents the DC gain of the channel. According to the Lambertian radiation model [30], the DC gain of the LOS link is expressed as:  
\[h(0)= \begin{cases}\frac{(m+1)A}{21D^{2}}cos^{m}(\alpha)T_{s}(\beta)g(\beta) \cos(\beta),0<\beta<FOV\\ 0\hskip 28.452756 pt,\hskip 28.452756 ptelse\end{cases}  \tag{3}\]  
where \(m\) represents the Lambertian radiation coefficient, \(D\) represents the distance from the white LED light source to the photodetector (PD), \(A\) is the detection area of the receiver, \(\alpha\) is the angle between the line connecting the transmitter and the receiver and the vertical direction, \(\beta\) is the incident angle of the PD, \(T_{s}(\beta)\) is the optical filter gain of the receiver, and \(g(\beta)\) is the optical system gain. The simulation parameters are set as shown in Table 2.  
According to Equation (2), the light-intensity distribution of the four LED transmitters is analyzed in the room and the power is received at different locations, as shown in Figure 6. It can be observed that the light intensity and received power are highest near the four groups of LED light sources, and they gradually decrease as the distance from the sources increases. However, from Figure 6a, it can be seen that the minimum value of room \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Parameter** & **Value** \\ \hline Room & Size & \(4.5\) m \(\times\) \(4.5\) m \(\times\) \(3\) m \\  & & (\(-1.125\), \(-1.125\), \(3\)) \\  & Space Position & (\(-1.125\), \(1.125\), \(3\)) \\  & & (\(1.125\), \(1.125\), \(3\)) \\  & & (\(1.125\), \(-1.125\), \(3\)) \\ \hline  & Semi-angle at half power & \(70^{\circ}\) \\ Optical Transmitter & Transmit Power & \(30\) mW \\  & LED Array & \(60\)\(\times\)\(60\) \\  & Center Emission Intensity & \(300\)–\(900\) lx \\ \hline  & Effective Area & \(1\) cm\({}^{2}\) \\ Optical Receiver & FOV & \(70^{\circ}\) \\  & Elevation & \(90^{\circ}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Simulation parameters. Figure 5: Indoor MISO-VLC system. illuminance is 373 lx, while the range for general lighting is between 300 lx and 1540 lx [31]. Therefore, using a combination of four groups of white LED arrays is sufficient to meet the daily lighting requirements. Additionally, the distribution of received power, as shown in Figure 6b, indicates that the maximum power is 4.7503 dBm, while the minimum power is 0.2579 dBm. Except for the edges of the room, the SNR in the main activity area is adequate to fulfill the communication requirements. Similarly, we tested at other locations in the room, as shown in Figure 7. When the LED light is positioned close to the center points (\(-0.75\), \(-0.75\), \(3\)), (\(-0.75\), \(0.75\), \(3\)), (\(0.75\), \(3\)), and (\(0.75\), \(-0.75\), \(3\)), the minimum light intensity is 324 lx. Simultaneously, the minimum received optical power is \(-0.7011\) dBm, and the maximum received optical power is 6.6168 dBm. When the LED lamp is positioned near the edge points (\(-1.25\), \(-1.25\), \(3\)), (\(-1.25\), \(1.25\), \(3\)), (\(1.25\), \(1.25\), \(3\)), and (\(1.25\), \(-1.25\), \(3\)), the minimum light intensity is 397 lx.