6 g underwater channel modeling were summarized based on optical communication

【Abstract】The research progress of underwater optical communication channel modeling is reviewed, and the key channel characteristics that affect the performance of underwater optical communication system are classified.First, the modeling work on the intrinsic optical properties of static seawater, namely absorption and scattering, is summarized.Secondly, the modeling work of the refractive index fluctuation of dynamic seawater, that is, ocean turbulence, is analyzed. From the bottom to the top, it is summarized from three aspects: undulating seawater → undulating light field → undulating light signal.Finally, the key problems that need to be solved are put forward to provide reference for further research.

【Key words】6G; underwater optical communication; channel modeling

0 Introduction

China has been commercializing 5G for three years, but more than 80% of the land area and more than 95% of the ocean area still have no mobile network signal.Moreover, the communication object is limited to the space 10,000 meters above the surface, and it is still impossible to realize the network swimming between the sky, the earth and the sea.According to statistics from the United Nations International Telecommunication Union (ITU), there are still 3 billion people in the world without basic network access facilities, and the digital divide in economic and social development still exists.Compared with 5G wireless communication network, 6G expects to introduce new performance indicators and application scenarios, and realize the four paradigm shifts of "full coverage, full spectrum, full application, and strong security".Among them, "full coverage" means that the ground mobile network should be extended to natural spaces such as space, sky and ocean, and provide information support for various activities of various users such as space-based, space-based, land-based and sea-based [1].It can be seen that achieving sea surface and underwater communication coverage is one of the key factors in achieving the vision of 6G full coverage.Surface coverage can be achieved with satellite networks, but underwater coverage faces huge challenges.The traditional underwater acoustic communication technology is highly mature, with low speed and large delay, which cannot meet the requirements of 6G ultra-high speed (Tbps) and ultra-low delay (ms); therefore, it includes Sub-6 GHz frequency band, millimeter wave, terahertz,The "full spectrum" resources including the optical frequency band will be fully exploited.However, the first three radio frequency methods are difficult to penetrate seawater; in comparison, spectral resources can be used to provide faster, safer, more robust and efficient communication, and are expected to become the key driving force of the global Internet.Among them, the blue-green light band is located in the seawater optical window ࿰