Wireless communication environment in recent years faces a problem of a rapid increase in data traffic. Hence, in 3GPP, installing a large number of small cells in a macro cell to increase network density, thereby distributing traffic, has been under study. Such a technology utilizing small cells is referred to as small cell enhancement. Note that small cells may conceptually include various types of cells (e.g., a femto cell, a nano cell, a pico cell, a micro cell, and the like) that are smaller than a macro cell and are arranged to overlap a macro cell.
In addition, as one way to expand radio resources, utilization of a frequency band of 6 GHz or more, which is called a millimeter-wave band, has been under study. However, since the millimeter-wave band has strong straightness and exhibits large radio propagation attenuation, utilization in a small cell smaller than a macro cell is expected. Since the millimeter-wave band is extensive, technologies for efficiently selecting an appropriate frequency for communication from such an extensive frequency band have become important. One such technology involves measuring a state (specifically, a characteristic or quality) of a channel using a reference signal. For example, a base station can select an appropriate channel for communication with a terminal apparatus by measuring an uplink reference signal transmitted from the terminal apparatus. As another technology regarding uplink, for example, Patent Literature 1 mentioned below discloses a technology for setting appropriate transmission power of an uplink signal.
USPTO Backgrounds
USPTO Backgrounds