# Advanced Progress of Optical Wireless Technologies for Power Industry: An Overview
## 2 Classification and Progress of Power Industry Optical Wireless Communications
### Integrated Transmission Schemes of Power Line and Indoor Wireless Optical Communications
Specifically, the research team from the University of Southampton proposed a NOMA joint power allocation strategy for PLC and IWOC networks [13]. The results show that NOMA technology has a higher throughput performance than OMA in terms of multiple minimum rate requirements and user density. The main defect of IWOC technology is the performance degradation under LOS path missing. RF communication, with its higher penetration capability, can overcome the above deficiencies. In fact, the fusion of PLC technology and wireless network has been proposed in many application scenarios. This includes integrating PLC technology into the wireless relay system in smart grid applications, so as to realize long-distance data transmission [66]. Based on the above considerations, researchers from Texas A&M University in Qatar proposed a hybrid PLC, IWOC, and RF communications system [66, 71], as shown in Figure 19[12]. To satisfy the required quality of service (QoS), researchers constructed and analyzed the overall transmission power minimization problem. To coordinate the collaboration between RF networks and hybrid PLC and IWOC networks, the team discusses resource allocation between two parallel links, namely RF links and hybrid PLC and IWOC links. The proposed system explores multiple wireless interfaces to accumulate the parallel data streams received. The results show that the above optimization problems can be constructed as convex optimization problems and can be solved by means of computational efficient behavior. The quantization results show that the actual system parameters such as PLC channel model and RF signal availability have a significant influence on network performance. Therefore, as a promising architecture, the parallel system of RF, PLC, and IWOC could enhance the rate and reliability of indoor wireless network. In [72], a new hybrid outdoor WOC/RF-IWOC system is proposed, which chooses to combine the selection between outdoor WOC and RF modules to obtain a single noise with a higher SNR. At the relay terminal, the DF protocol is adopted for the signals with high SNR, and then the signals  
Figure 19: Hybrid PLC/IWOC/RF communication system model [12]. are forwarded to the multi-user through the IWOC link. In [59], a hybrid PLC/IWOC/RF future for the wired backhaul system based on optical fibers has been proposed to improve the realized SRC. Meanwhile, PLC-IWOC system also provides a lot of advantages, such as good security, economical and easy to deploy, good transmission efficiency, high capacity, and high data rate [20; 73]. Thus, these systems could be a potential candidate to provide ubiquitous connectivity for Internet of Things (IoT) devices. In these three subsections, we consider the channel characteristics of PLC and IWOC system, the modulation of integrated PLC-IWOC system, and different transmission schemes. Table 2 compares the different researches between PLC and IWOC system in these years.