As the under 6 GHz band suitable for mobile communication is saturated, it is very difficult to secure a new frequency. Also, a method of retrieving and rearranging a low-utilization frequency band is difficult to be practiced due to a cost limit. To solve this problem, research on frequency sharing is actively in underway overseas. The frequency sharing model which has recently been drawing attention is citizens broadband radio service (CBRS) in U.S. and licensed shared access (LSA) in Europe. The ultimate goal of these frequency sharing models is to increase the spectral efficiency by using the band utilized for other uses in common with mobile communication. In this paper, we propose a four-layer next generation frequency sharing model from a conceptual point of view larger than CBRS and LSA. The proposed frequency sharing model is not limited to managing only specific bands, but covers the entire wireless communication spectrum and numerous systems as a whole. For the four-layer system, we diversify the license type to mitigate the protection from interference from other layers against the two-layer like LSA or three-layer such as CBRS and increase the coexistence probability. We discuss the architecture for four-layer frequency sharing systems and the requirement of the main function of the spectrum management system (SMS), the main server of the proposed frequency sharing model. We also discuss nonexclusive license types, system operations, and the use case suitable for the actual situation of domestic frequency usage.