I. Introduction
As the high-speed wireless network spreads, the enjoyment of diverse ICT services has been enabled leading to the situations in which numbers of people are routinely using digital devices. With this trend, the environment for internet access has been improved with an increase of Wi-Fi usage provided by shared spaces such as offices, coworking spaces, and homes, thus enhancing user convenience. Concurrently, the diversification of digital content such as streaming services, high-resolution videos, and online gaming requires unprecedented wide bandwidth. As a result, the amount of data consumption by individual devices has increased dramatically, necessitating a corresponding increase in the communication bandwidth required.