# 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  
PLC and RF integration into wireless relay systems has been proposed for many applications, including indoor, outdoor, and smart grids [29; 58; 59; 60; 61; 62]. In [63], a cascaded IWOC and outdoor WOC communications system is studied and DF relay is established. The capacity of the system is studied, and the results show that the hybrid system has high data transmission efficiency. Some different integrated scheme of power line and IWOC is shown in Figure 15. DF relay hybrid IWOC-PLC scheme, hybrid IWOC-PLC scheme, multichannel hybrid IWOC-PLC system and full duplex DF IWOC-PLC scheme are proposed [15; 16; 17; 19]. Where the PLC represents for the IWOC. Indoor multi-user downlink of hybrid circuit and IWOC must face the limited transmission bandwidth of power line and visible integrated channel. In order to improve the transmission spectrum efficiency of the above hybrid system, more and more researchers have propo  
Figure 15: The different schemes of IWOC-PLC systems: (**a**) DF relay hybrid IWOC-PLC scheme [15], (**b**) hybrid IWOC-PLC scheme [15; 16; 19]; (**c**) multichannel hybrid IWOC-PLC system [15]; (**d**) full duplex DF IWOC-PLC scheme [17]. scheme to better cope with the frequency selectivity of the channel [27; 28; 35; 41; 64; 65], as shown in Figure 16. In this paper, the IWOC in the module in Figure 16 is represented by IWOC. On the basis of the above work, researchers developed a PLC-oriented visible light positioning system and presented a laboratory prototype demonstration [15], as shown in Figure 17. The above prototype leverages an Android application to achieve a few KBPS level of low speed links. This work will help speed up the commercialization of such systems and prototypes. Such a power wireless optical positioning system can make full use of the orientation of LED beam and PLC return network to provide users with customized services based on user location, including indoor navigation, device tracking, and equipment management [15; 19]. In addition, existing indoor monitoring or sensing device can also realize the power supply and communications function of the above system at the same time, so as to timely transmit the monitoring or sensing data to the indoor wireless terminal. In [1; 12; 15; 17; 33; 36; 64; 50; 66], these studies have shown that the cooperative relay aided PLC-IWOC system has not been thoroughly analyzed according to various statistical parameters. In [12], the transmission power optimization problem of hybrid IWOC/PLC/RF communication system is discussed. It must be pointed out that the research and implementation of power wireless optical positioning technology is still in its infancy. Some of the more complex and potentially high-precision visible location technologies have not been fully explored in this field. These algorithms usually need to measure the reception intensity information, arrival angle information, arrival time information, or arrival time difference information of light signals from different LED light sources. Based on such information and the location information of the light source, the spatial location of the mobile terminal can be reversely estimated [6]. The existing research work often stops at the positioning algorithm itself, without fully considering the actual factors such as interconnection relationship, physical characteristics, and synchronous performance of the power line network connected with the LED light source to the potential influence on the performance of power wireless optical positioning technology. Therefore, it is necessary to carry out targeted performance improvement work on the basis of comprehensive consideration of the above factors, so as to make the high-precision power wireless optical positioning technology from theoretical analysis to practical application. Figure 16: Block diagram of the integrated PLC and IWOC multicarrier system [15].