UHF and microwave bands have been used in mobile communication systems, but with 5G the use of millimeter wave bands has begun, and studies have begun for the use of terahertz wave bands in Beyond 5G/6G. In terms of wavelength, this means using a range from tens of centimeters to several millimeters, and in terms of frequency, from several hundred MHz to several hundred GHz, a range of about three orders of magnitude. Since the physical properties of electromagnetic waves differ greatly over such a wide range, it is natural to use them in an appropriate manner for each band so that their properties can be maximized. On the other hand, from a system point of view, it is better to use a single system for each frequency band than to develop different systems for each band and operate multiple systems. Furthermore, from an economic point of view, it is important to reduce the maintenance and operating costs of the equipment.

In the 2030s, when Beyond 5G/6G will be introduced, a Cyber Physical System (CPS) will be formed. Data in real space will be collected via communication systems, reconstructed, analyzed, and predicted in cyberspace, and driven into real space based on the results.

This cycle is called the CPS loop. The goal is to realize an inclusive, sustainable, and dependable society by spreading the CPS to every corner of social life. In order to achieve this goal, the core of the CPS loop is the next generation mobile communication system, namely Beyond 5G/6G. It is important to ensure that the various radio bands in Beyond 5G/6G are used in the right places in order to meet these objectives and goals.