In communication systems approved by Third Generation Partnership Project (3GPP), such as Wideband Code Division Multiple Access (WCDMA) (a registered trademark), Long Term Evolution (LTE), and LTE-Advanced (LTE-A), or in communication systems approved by the Institute of Electrical and Electronics Engineers (IEEE), such as Wireless LAN and Worldwide Interoperability for Microwave Access (WiMAX), a base station apparatus (a cell, a first communication apparatus (a communication apparatus that is different from a terminal device), or an eNodeB) and a terminal device (a mobile terminal, a mobile station apparatus, a second communication apparatus (a communication device that is different from the base station apparatus), or user equipment (UE)) each include multiple transmit and receive antennas, and spatially multiplex a data signal and realize high-speed data communication by using a Multi Input Multi Output (MIMO) technology.
In LTE, in some cases, the base station apparatus is also referred to as an evolved NodeB (eNodeB) and the terminal device is also referred to as user equipment (UE). Furthermore, LTE is a cellular communication system in which an area is divided in a cellular pattern into multiple cells, each being served by the base station apparatus. A single base station apparatus may manage multiple cells.
In the communication system, in order to realize the data communication between the base station apparatus and the terminal device, the base station apparatus needs to perform various control processes on the terminal device. Accordingly, the base station apparatus notifies the terminal device of control information using a prescribed resource, and thus performs the data communication for downlink and uplink. For example, the base station apparatus notifies the terminal device of resource allocation information, modulation information on and coding information on the data signal, information on the number of times that spatial multiplexing is performed on the data signal, transmit power control information, and the like, and thus realizes the data communication.
The communication system supports time division duplex (TDD). LTE that employs a TDD scheme is also referred to as TD-LTE or LTE TDD. TDD is a technology that makes downlink and uplink communication possible in a single frequency band (a carrier frequency or a component carrier) by spatially multiplexing an uplink signal and a downlink signal.
In 3GPP, it is considered that a traffic adaptation technology and an interference reduction technology (DL-UL interference management and traffic adaptation), in both of which according to an uplink traffic and a downlink traffic, a ratio between an uplink resource and a downlink resource is changed are applied to TD-LTE (NPL 1).
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