Fig. 4.

The plot of antenna profiles of the up and downlink nodes, where (a) the antenna gain, (b) the uplink directivity, (c) the downlink directivity, (d) the WiFi band with the uplink and downlink center frequencies of 191.48 THz and 199.41 THz, respectively, (e) the Li-Fi band with the uplink and downlink center wavelengths of 1.56 µm and 1.50 µm, respectively. The multiplexed signals can be applied by the space-time modulation in both frequency and wavelength domains, from which the information capacity can be increased to accommodate the big data transmission