## 1 Introduction  
With the rapid development of 5G mobile communication, the power system pays more and more attention to communication technology. The application of cutting-edge technologies such as big data, cloud computing, Internet of Things (IoT), mobile Internet and physical information fusion system in power systems has also attracted widespread attention. With the development of power supply networks, the coverage area of power lines has progressed considerably. The optimization of existing power supply network resources and the transmission of reliable information on power lines have gradually attracted the attention of researchers [1]. The power line serves not only as a medium for transmitting power but also for transmitting data for communication. Power line communications (PLC) can reach anywhere power lines exist, especially where the wireless signal is weak, such as underground, under water and metal-walled rooms. In communication architectures, PLC [2] uses the existing power line infrastructure to transmit information with power and provides cost-effective and extensive coverage of smart grid solutions [3]. However, the power line was originally designed for power transmission rather than specifically for communication. Therefore, problems such as insufficient reliability and inaccessibility of the mobile terminal exist in the PLC. First, the attenuation of long-distance and high-frequency signals significantly result in limited bandwidth. Second, the complicated noise, which is composed of background and impulse noises, in the power line is different from those of other communication channels. Third, the transmission power of the PLC is limited by electromagnetic compatibility rules. Finally, the PLC channel varies with location, network topology, and connection load. Therefore, this study considers the collaboration between PLC and other communication networks (such as wireless networks). When the mobile terminal encounters obstacles that lead to poor link quality, it can transmit via the power line channel to ensure the reliability of communication. In the absence of the power line or with a poor quality of PLC, wireless transmission can be performed to ensure the normal operation of communication [4]. The joint PLC/wireless dual-media cooperative communication technology has the practical advantages of integrating resources, complementary advantages, saving construction cost and improving overall system performance. In fact, the concept of hybrid systems has been discussed since 2005. The latest research results include multipath transmission [3; 5], relay forwarding [6; 7; 8; 9; 10; 11; 12; 13], multimedia collaboration [14; 15; 16; 17; 18], parallel communication [15; 17] and other PLC collaboration technologies. For the cooperation technology of wireless and PLC, extensive research, such as [6; 7], uses the relay cooperation scheme of PLC and wireless communication because the direct link cannot meet the requirements of communication in many cases, and the relay collaborative technology can resist fading and improve the communication links. Research on relay is mainly divided into dual-hop [8; 9] and multihop [10; 11] relays, with both focusing on decode-and-forward (DF) and amplify-and-forward (AF) relay protocols. In terms of power communication, literature [11] analyzes the performance of multihop PLC systems by using the DF relay under Log-normal (LogN) fading and impulse noise conditions. In a recent work [12], multihop transmission is used for the low-frequency narrowband PLC network to resist the distance attenuation characteristics of power line channels. In these line channels, cooperative communication can reasonably select the relay nodes and use maximum ratio combining (MRC) or selective merging at the destination nodes to improve system reliability and ensure that normal communication can improve system performance even without a direct link.