## 4 OWC Technologies for the 5G, 6G, and IoT Solutions
### Fulfilling the Service Quality Characteristics  
_High volume of capacity:_ A much higher bandwidth is essential to realize thousand-fold capacity enhancements in 5 GB networks. This desirable higher bandwidth is available in the optical spectrum. Table 3 lists the RF and optical frequencies in the electromagnetic spectrum. The RF band consists of only 300 GHz of the huge electromagnetic spectrum. The optical band (300 GHz to 30 PHz) is considerably very high. However, only a small portion of the optical spectrum (a part of visible light, near infrared, and middle ultraviolet) is currently being used. Future research will increase the use of the optical spectrum portion as well as improve the efficient use of it. The terahertz band (0.3-3 THz) situated in infrared is expected to be used for future high-data-rate cellular communications [31]. The availability of a wide optical spectrum through different OWC technologies opens the opportunity to support a high volume of data capacity. Moreover, high-speed network connectivity is required to support massive IoT connectivity. Hence, the optical spectrum has the potential to serve the large volume of data traffic generated by high-data-rate heterogeneous multimedia applications in the 5G, 6G, and IoT networks. Figure 2: OWC networks for the 5G/6G and IoT platforms. _Ultra-high user data rate_: The transmission rate of the 5G mobile communication systems is expected to reach an average of 1 Gbps at a 10 Gbps peak rate [8]. Accordingly, 6G will later support tens of Gbps to Tbps bit rates per device. The VLC and LiFi technologies have the capability to support very high-data-rate services at the user level. Moreover, LiFi can support a complete network system (i.e., point-to-multipoint, multipoint-to-point, and bidirectional communications) such as WiFi. A data rate of 100 Gbps has already been confirmed using the VLC [18; 43]. The FSO can also support high-data-rate services indoors and outdoors. An outdoor remote high-speed connectivity is possible using the FSO network. The OWC based on the UV band can provide high-data-rate, non-line-of-sight communications [4]. In addition, extensive studies aimed at increasing the data rate in the OWC technologies are ongoing. Hence, the OWC technologies are a good complementary solution for supporting high-data-rate connectivity in 5G and 6G and more advanced communication systems. Figure 3 illustrates a scenario of high-speed connectivity using different OWC technologies. High-data rate connectivity is provided to indoor and outdoor users and in V2X communications. _Ultra-low latency_: Low latency is a crucial criterion for any kind of communication system and is a more critical factor in 5 GB communication systems. OWC systems normally follow line-of-sight (LOS) paths and, hence, the communication distance is minimum with no loss due to the obstructions. However, the RF-based communications use both LOS and non-line-of-sight (NLOS) paths. There is a significant loss due to the obstructions in NLOS paths. Moreover, the communication distance is not minimum due to the NLOS path. Hence, even though RF and optical signals both propagate at the speed of light, the communication using the optical band is faster than that using RF bands because the propagation is rapid in the optical communication systems [44]. Additionally, the processing time in an optical system is short. A fraction of millisecond end-to-end delay communication services can be provided using the OWC technologies. Hence, these OWC-based network technologies that can offer services with negligible latency in the 5 GB communication systems. _Ultra-low-energy consumption_: Among a few important criteria, energy efficiency is one of the most important requirements for all 5G, 6G, and IoT systems. Most OWC system infrastructures are based on LEDs. Currently deployed LEDs consume a very small power. Moreover, huge studies are currently ongoing around the world to reduce the power consumption by LEDs. LEDs can also be used for illumination and communication.