# A Novel 4 \(\times\) 1 MISO-VLC System with FBMC-OQAM Downlink Signals
## 3 Results and Discussion
The minimum receiving optical power is 0.6518 dBm, and the maximum receiving optical power is 4.2941 dBm. Figure 8 shows the comparison of BER for OFDM and FBMC-OQAM signals in \(1\times 1\) SISO and \(4\times 1\) MISO channels. When the SNR is 24 dB, the \(4\times 1\) MISO FBMC-OQAM (32 QAM) achieves the lowest BER (6.74 \(\times\) 10\({}^{-6}\)), while the \(4\times 1\) MISO OFDM (32 QAM)  
Figure 6: (**a**) Light-intensity distribution map with four LED arrays. (**b**) Received power map with four LED arrays. Figure 7: (**a**) Light-intensity distribution map with four LED arrays near the center point, (**b**) Received power map with four LED arrays near the center point, (**c**) Light-intensity distribution map with four LED arrays near the edge point, and (**d**) Received power map with four LED arrays near the edge point. has a slightly higher BER of 1.28 \(\times\) 10\({}^{-5}\). Similarly, at the SNR of 24 dB with a modulation order of 64, the BER of 4 \(\times\) 1 MISO FBMC-OQAM is 8.55 \(\times\) 10\({}^{-4}\), and the BER of 4 \(\times\) 1 MISO OFDM is 1.24 \(\times\) 10\({}^{-3}\). FBMC-OQAM signals demonstrate superior performance in visible-light signal reception compared to OFDM signals. As the SNR is 23 dB and the modulation order is 32, the BER of 4\(\times\)1 MISO FBMC-OQAM is 5.12 \(\times\) 10\({}^{-5}\), and the BER of 1 \(\times\) 1 SISO FBMC-OQAM is 3.28 \(\times\) 10\({}^{-4}\). Meanwhile, at the SNR of 23 dB, the BER of 4 \(\times\) 1 MISO OFDM and 1\(\times\)1 SISO OFDM is 8.31 \(\times\) 10\({}^{-5}\) and 5.7 \(\times\) 10\({}^{-4}\), respectively. It can be seen that the 4 \(\times\) 1 MISO system used has a lower BER and a larger access bandwidth compared to the 1 \(\times\) 1 SISO system. When the BER is 10\({}^{-3}\), the corresponding SNRs for 4 \(\times\) 1 MISO FBMC-OQAM (32 QAM), 4 \(\times\) 1 MISO OFDM (32 QAM), 1 \(\times\) 1 SISO FBMC-OQAM (32 QAM), 1 \(\times\) 1 SISO OFDM (32 QAM), 4 \(\times\) 1 MISO FBMC-OQAM (64 QAM), 4 \(\times\) 1 MISO OFDM (64 QAM), 1 \(\times\) 1 SISO FBMC-OQAM (64 QAM), and 1 \(\times\) 1 SISO OFDM (64 QAM) are 20.86 dB, 21.19 dB, 22.21 dB, 22.50 dB, 23.85 dB, 24.18 dB, 24.72 dB, and 25.31 dB, respectively. We introduced a frequency offset and compared the signal-reception performance under various frequency offsets. As shown in Figure 9, the BER of the received OFDM signal increases rapidly with the increase in frequency offset. The BER of FBMC increases significantly and gradually. The rapid increase in the BER of OFDM rises rapidly with frequency offset within a specific range and is attributed to the modulation of the system based on FFT transform. The overall anti-frequency offset performance of FBMC is higher than that of OFDM. This is due to the fact that the prototype filter of FBMC is designed to be flat in the band, resulting in low inter-carrier interference. The frequency offset in the subcarrier interval will not cause a significant BER, but it is fundamentally dependent on the modulation method of time-frequency transformation. When the frequency offset exceeds a certain range, the signal-reception performance will deteriorate. In this scheme, the filter bank is used to achieve the modulation and demodulation of subcarriers. This process enables fast attenuation of out-of-band amplitudes, reduces inter-subcarrier interference and inter-symbol interference, and decreases sensitivity to frequency offset. In addition, FBMC/OQAM can maintain good anti-interference performance in the presence of frequency offset. In OFDM, frequency offset disrupts the orthogonality between subcarriers, introducing interference. MISO can leverage the spatial diversity provided by multiple LEDs to offer diversity gain. This helps mitigate the effects of fading, improving the overall system reliability and performance. Based on the data comparison above, it can be concluded that FBMC-OQAM, combined with MISO technology, offers superior transmission performance.