Patent Publication Number: US-11664943-B2

Title: Terminal device, base station device, and communication method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 16/579,851, filed Sep. 24, 2019, which is a continuation of U.S. application Ser. No. 15/760,479, filed Mar. 15, 2018 (now U.S. Pat. No. 10,461,902), which is based on PCT filing PCT/JP2016/087421, filed Dec. 15, 2016, and claims priority to JP 2016-018832, filed Feb. 3, 2016, the entire contents of each are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a terminal device, a base station device, and a communication method. 
     BACKGROUND ART 
     Wireless access schemes and wireless networks of cellular mobile communication (hereinafter also referred to as LTE-Advanced (LTE-A), LTE-Advanced Pro (LTE-A Pro), or Evolved Universal Terrestrial Radio Access (EUTRA)) are under review in 3rd Generation Partnership Project (3GPP). Further, in the following description, LTE includes LTE-A, LTE-A Pro, and EUTRA. In LTE, a base station device (base station) is also referred to as an evolved Node B (eNodeB), and a terminal device (a mobile station, a mobile station device, or a terminal) is also referred to as a user equipment (UE). LTE is a cellular communication system in which a plurality of areas covered by a base station device are arranged in a cell form. A single base station device may manage a plurality of cells. 
     LTE is compatible with frequency division duplex (FDD) and time division duplex (TDD). LTE employing the FDD scheme is also referred to as FD-LTE or LTE FDD. TDD is a technology which enables full duplex communication to be performed in at least two frequency bands by performing frequency division multiplexing on an uplink signal and a downlink signal. LTE employing the TDD scheme is also referred to as TD-LTE or LTE TDD. TDD is a technology that enables full duplex communication to be performed in a single frequency band by performing time division multiplexing on an uplink signal and a downlink signal. The details of FD-LTE and TD-LTE are disclosed in Non-Patent Literature 1. 
     The base station device maps a physical channel and a physical signal to physical resources configured on the basis of a predefined frame configuration and transmits the physical channel and the physical signal. The terminal device receives the physical channel and the physical signal transmitted from the base station device. In LTE, a plurality of frame configuration types are specified, and data transmission is performed using physical resources of a frame configuration corresponding to each frame configuration type. For example, a frame configuration type 1 is applicable to FD-LTE, and a frame configuration type 2 is applicable to TD-LTE. The details of the frame structure are disclosed in Non-Patent Literature 1. 
     In LTE, a predetermined time interval is specified as a unit of time in which data transmission is performed. Such a time interval is referred to as a transmission time interval (TTI). For example, the TTI is one millisecond, and in this case, one TTI corresponds to one sub frame length. The base station device and the terminal device perform transmission and reception of the physical channel and/or the physical signal on the basis of the TTI. The details of the TTI are disclosed in Non-Patent Literature 2. 
     Further, the TTI is used as a unit specifying a data transmission procedure. For example, in the data transmission procedure, a hybrid automatic repeat request-acknowledgment (HARQ-ACK) report indicating whether or not received data has been correctly received is transmitted after a period of time specified as an integer multiple of the TTI after data is received. Therefore, a period of time (delay or latency) necessary for data transmission is decided depending on the TTI. Such a data transmission procedure is disclosed in Non-Patent Literature 3. 
     CITATION LIST 
     Non-Patent Literature 
     
         
         Non-Patent Literature 1: 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 12), 3GPP TS 36.211 V12.7.0 (2015-09). 
         Non-Patent Literature 2: 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 (Release 12), 3GPP TS 36.300 V12.7.0 (2015-09). 
         Non-Patent Literature 3: 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures (Release 12), 3GPP TS 36.213 V12.7.0 (2015-09). 
       
    
     DISCLOSURE OF INVENTION 
     Technical Problem 
     In LTE, only one millisecond is specified as the TTI, and the physical channel and the physical signal are specified on the basis of the TTI of 1 msec. Further, a period of time necessary for data transmission is an integral multiple of 1 millisecond. For this reason, in a use case in which the period of time necessary for data transmission is important, a size (length) of the TTI affects a characteristic. Further, in a case in which a plurality of physical resources are consecutively allocated to the terminal device in such a use case in order to reduce the period of time necessary for data transmission, transmission efficiency of the entire system greatly deteriorates. 
     The present disclosure was made in light of the above problem, and it is an object to provide a base station device, a terminal device, a communication system, a communication method, and an integrated circuit, which are capable of improving the transmission efficiency of the entire system in consideration of the period of time necessary for data transmission in a communication system in which a base station device and a terminal device communicate with each other. 
     Solution to Problem 
     According to the present disclosure, there is provided a terminal device that communicates with a base station device, including: a higher layer processing unit configured to set an STTI channel setting through signaling of a higher layer from the base station device; and a receiving unit configured to receive a first PDSCH in a case in which the STTI channel setting is not set and receive a second PDSCH in a case in which the STTI channel setting is set. The first PDCCH is mapped to one or more resource blocks, and the second PDCCH is mapped to one or more sub resource blocks defined in accordance with a smaller number of symbols than a number of symbols corresponding to a resource block. 
     In addition, according to the present disclosure, there is provided a base station device that communicates with a terminal device, including: a higher layer processing unit configured to set an STTI channel setting in the terminal device through signaling of a higher layer; and a transmitting unit configured to transmit a first PDSCH in a case in which the STTI channel setting is not set and transmit a second PDSCH in a case in which the STTI channel setting is set. The first PDCCH is mapped to one or more resource blocks, and the second PDCCH is mapped to one or more sub resource blocks defined in accordance with a smaller number of symbols than a number of symbols corresponding to a resource block. 
     In addition, according to the present disclosure, there is provided a communication method used in a terminal device that communicates with a base station device, including: a step of setting an STTI channel setting through signaling of a higher layer from the base station device; and a step of receiving a first PDSCH in a case in which the STTI channel setting is not set and receiving a second PDSCH in a case in which the STTI channel setting is set. The first PDCCH is mapped to one or more resource blocks, and the second PDCCH is mapped to one or more sub resource blocks defined in accordance with a smaller number of symbols than a number of symbols corresponding to a resource block. 
     In addition, according to the present disclosure, there is provided a communication method used in a base station device that communicates with a terminal device, including: a step of setting an STTI channel setting in the terminal device through signaling of a higher layer; and a step of transmitting a first PDSCH in a case in which the STTI channel setting is not set and transmitting a second PDSCH in a case in which the STTI channel setting is set. The first PDCCH is mapped to one or more resource blocks, and the second PDCCH is mapped to one or more sub resource blocks defined in accordance with a smaller number of symbols than a number of symbols corresponding to a resource block. 
     Advantageous Effects of Invention 
     As described above, according to the present disclosure, it is possible to improve the transmission efficiency in the wireless communication system in which the base station device and the terminal device communicate with each other. 
     Note that the effects described above are not necessarily limitative. With or in the place of the above effects, there may be achieved any one of the effects described in this specification or other effects that may be grasped from this specification. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a diagram illustrating an example of a downlink sub frame of the present embodiment. 
         FIG.  2    is a diagram illustrating an example of an uplink sub frame of the present embodiment. 
         FIG.  3    is a schematic block diagram illustrating a configuration of a base station device  1  of the present embodiment. 
         FIG.  4    is a schematic block diagram illustrating a configuration of a terminal device  2  of the present embodiment. 
         FIG.  5    is a diagram illustrating an example of downlink resource element mapping in the present embodiment. 
         FIG.  6    is a diagram illustrating an example of a TTI in the present embodiment. 
         FIG.  7    is a diagram illustrating an example of a TTI in the present embodiment. 
         FIG.  8    is a diagram illustrating an example of a set of SPDSCH candidates. 
         FIG.  9    is a diagram illustrating an example of SPDSCH transmission in a base station device and a HARQ-ACK report in a terminal device. 
         FIG.  10    is a diagram illustrating an example of SPDSCH transmission in a base station device and a HARQ-ACK report in a terminal device. 
         FIG.  11    is a flowchart of a terminal device in which STTI setting is performed. 
         FIG.  12    is a diagram illustrating an example of operations of a base station device and a terminal device in a case in which setting related to the same SPDSCH is performed in a plurality of terminal devices. 
         FIG.  13    is a diagram illustrating an example of resource element mapping of an SPDSCH. 
         FIG.  14    is a block diagram illustrating a first example of a schematic configuration of an eNB to which the technology according to the present disclosure may be applied. 
         FIG.  15    is a block diagram illustrating a second example of the schematic configuration of the eNB to which the technology according to the present disclosure may be applied. 
         FIG.  16    is a block diagram illustrating an example of a schematic configuration of a smartphone to which the technology according to the present disclosure may be applied. 
         FIG.  17    is a block diagram illustrating an example of a schematic configuration of a car navigation apparatus to which the technology according to the present disclosure may be applied. 
     
    
    
     MODE(S) FOR CARRYING OUT THE INVENTION 
     Hereinafter, (a) preferred embodiment(s) of the present disclosure will be described in detail with reference to the appended drawings. Note that, in this specification and the appended drawings, structural elements that have substantially the same function and structure are denoted with the same reference numerals, and repeated explanation of these structural elements is omitted. 
     Wireless Communication System in the Present Embodiment 
     In the present embodiment, a wireless communication system includes at least a base station device  1  and a terminal device  2 . The base station device  1  can accommodate multiple terminal devices. The base station device  1  can be connected with another base station device by means of an X2 interface. Further, the base station device  1  can be connected to an evolved packet core (EPC) by means of an S1 interface. Further, the base station device  1  can be connected to a mobility management entity (MME) by means of an S1-MME interface and can be connected to a serving gateway (S-GW) by means of an S1-U interface. The S1 interface supports many-to-many connection between the MME and/or the S-GW and the base station device  1 . 
     Frame Configuration in Present Embodiment 
     In the present embodiment, a radio frame configured with 10 ms (milliseconds) is specified. Each radio frame includes two half frames. A time interval of the half frame is 5 ms. Each half frame includes 5 sub frames. The time interval of the sub frame is 1 ms and is defined by two successive slots. The time interval of the slot is 0.5 ms. An i-th sub frame in the radio frame includes a (2×i)-th slot and a (2×i+1)-th slot. In other words, 10 sub frames are specified in each of the radio frames. 
     The sub frame includes a downlink sub frame (a first sub frame), an uplink sub frame (a second sub frame), a special sub frame (a third sub frame), and the like. 
     The downlink sub frame is a sub frame reserved for downlink transmission. The uplink sub frame is a sub frame reserved for uplink transmission. The special sub frame includes three fields. The three fields are a Downlink Pilot Time Slot (DwPTS), a Guard Period (GP), and an Uplink Pilot Time Slot (UpPTS). A total length of DwPTS, GP, and UpPTS is 1 ms. The DwPTS is a field reserved for downlink transmission. The UpPTS is a field reserved for uplink transmission. The GP is a field in which downlink transmission and uplink transmission are not performed. Further, the special sub frame may include only the DwPTS and the GP or may include only the GP and the UpPTS. The special sub frame is placed between the downlink sub frame and the uplink sub frame in TDD and used to perform switching from the downlink sub frame to the uplink sub frame. 
     A single radio frame includes a downlink sub frame, an uplink sub frame, and/or a special sub frame. Further, a single radio frame may include only a downlink sub frame, an uplink sub frame, or a special sub frame. 
     A plurality of radio frame configurations are supported. The radio frame configuration is specified by the frame configuration type. The frame configuration type 1 can be applied only to FDD. The frame configuration type 2 can be applied only to TDD. The frame configuration type 3 can be applied only to an operation of a licensed assisted access (LAA) secondary cell. 
     In the frame configuration type 2, a plurality of uplink-downlink configurations are specified. In the uplink-downlink configuration, each of 10 sub frames in one radio frame corresponds to one of the downlink sub frame, the uplink sub frame, and the special sub frame. The sub frame  0 , the sub frame  5  and the DwPTS are constantly reserved for downlink transmission. The UpPTS and the sub frame just after the special sub frame are constantly reserved for uplink transmission. 
     In the frame configuration type 3, 10 sub frames in one radio frame are reserved for downlink transmission. The terminal device  2  treats each sub frame as an empty sub frame. Unless a predetermined signal, channel and/or downlink transmission is detected in a certain sub frame, the terminal device  2  assumes that there is no signal and/or channel in the sub frame. The downlink transmission is exclusively occupied by one or more consecutive sub frames. The first sub frame of the downlink transmission may be started from any one in that sub frame. The last sub frame of the downlink transmission may be either completely exclusively occupied or exclusively occupied by a time interval specified in the DwPTS. 
     Further, in the frame configuration type 3, 10 sub frames in one radio frame may be reserved for uplink transmission. Further, each of 10 sub frames in one radio frame may correspond to any one of the downlink sub frame, the uplink sub frame, and the special sub frame. 
     The base station device  1  may transmit a PCFICH, a PHICH, a PDCCH, an EPDCCH, a PDSCH, a synchronization signal, and a downlink reference signal in the DwPTS of the special sub frame. The base station device  1  can restrict transmission of a PBCH in the DwPTS of the special sub frame. The terminal device  2  may transmit a PRACH and an SRS in the UpPTS of the special sub frame. In other words, the terminal device  2  can restrict transmission of a PUCCH, a PUSCH, and a DMRS in the UpPTS of the special sub frame. 
       FIG.  1    is a diagram illustrating an example of the downlink sub frame of the present embodiment. The diagram illustrated in  FIG.  1    is also referred to as a downlink resource grid. The base station device  1  can transmit a downlink physical channel and/or a downlink physical signal in the downlink sub frame from the base station device  1  to the terminal device  2 . 
     The downlink physical channel includes a physical broadcast channel (PBCH), a physical control format indicator channel (PCFICH), a physical hybrid automatic repeat request indicator channel (PHICH), a physical downlink control channel (PDCCH), an enhanced physical downlink control channel (EPDCCH), a physical downlink shared channel (PDSCH), a physical multicast channel (PMCH), and the like. The downlink physical signal includes a synchronization signal (SS), a reference signal (RS), a discovery signal (DS), and the like. In  FIG.  1   , regions of the PDSCH and the PDCCH are illustrated for simplicity. 
     The synchronization signal includes a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and the like. The reference signal in the downlink includes a cell-specific reference signal (CRS), a UE-specific reference signal associated with the PDSCH (PDSCH-DMRS:), a demodulation reference signal associated with the EPDCCH (EPDCCH-DMRS), a positioning reference signal (PRS), a channel state information (CSI) reference signal (CSI-RS), a tracking reference signal (TRS), and the like. The PDSCH-DMRS is also referred to as a URS associated with the PDSCH or referred to simply as a URS. The EPDCCH-DMRS is also referred to as a DMRS associated with the EPDCCH or referred to simply as DMRS. The PDSCH-DMRS and the EPDCCH-DMRS are also referred to simply as a DL-DMRS or a downlink demodulation reference signal. The CSI-RS includes a non-zero power CSI-RS (NZP CSI-RS). Further, the downlink resources include a zero power CSI-RS (ZP CSI-RS), a channel state information-interference measurement (CSI-IM), and the like. 
       FIG.  2    is a diagram illustrating an example of the uplink sub frame of the present embodiment. The diagram illustrated in  FIG.  2    is also referred to as an uplink resource grid. The terminal device  2  can transmit an uplink physical channel and/or an uplink physical signal in the uplink sub frame from the terminal device  2  to the base station device  1 . The uplink physical channel includes a physical uplink shared channel (PUSCH), a physical uplink control channel (PUCCH), a physical random access channel (PRACH), and the like. The uplink physical signal includes a reference signal (RS). 
     The reference signal in the uplink includes an uplink demodulation signal (UL-DMRS), a sounding reference signal (SRS), and the like. The UL-DMRS is associated with transmission of the PUSCH or the PUCCH. The SRS is not associated with transmission of the PUSCH or the PUCCH. 
     The downlink physical channel and the downlink physical signal are referred to collectively as a downlink signal. The uplink physical channel and the uplink physical signal are referred to collectively as an uplink signal. The downlink physical channel and the uplink physical channel are referred to collectively as a physical channel. The downlink physical signal and the uplink physical signal are referred to collectively as a physical signal. 
     The BCH, the MCH, the UL-SCH, and the DL-SCH are transport channels. The channel used in the medium access control (MAC) layer is referred to as a transport channel. A unit of the transport channel used in the MAC layer is also referred to as a transport block (TB) or a MAC protocol data unit (MAC PDU). In the MAC layer, control of a hybrid automatic repeat request (HARD) is performed for each transport block. The transport block is a unit of data that the MAC layer transfers (delivers) to the physical layer. In the physical layer, the transport block is mapped to a codeword, and an encoding process is performed for each codeword. 
     Physical Resources in Present Embodiment 
     In the present embodiment, one slot is defined by a plurality of symbols. The physical signal or the physical channel transmitted in each of the slots is represented by a resource grid. In the downlink, the resource grid is defined by a plurality of sub carriers in a frequency direction and a plurality of OFDM symbols in a time direction. In the uplink, the resource grid is defined by a plurality of sub carriers in the frequency direction and a plurality of SC-FDMA symbols in the time direction. The number of sub carriers or the number of resource blocks may be decided depending on a bandwidth of a cell. The number of symbols in one slot is decided by a type of cyclic prefix (CP). The type of CP is a normal CP or an extended CP. In the normal CP, the number of OFDM symbols or SC-FDMA symbols constituting one slot is 7. In the extended CP, the number of OFDM symbols or SC-FDMA symbols constituting one slot is 6. Each element in the resource grid is referred to as a resource element. The resource element is identified using an index (number) of a sub carrier and an index (number) of a symbol. Further, in the description of the present embodiment, the OFDM symbol or SC-FDMA symbol is also referred to simply as a symbol. 
     The resource blocks are used for mapping to resource elements of a certain physical channel (the PDSCH, the PUSCH, or the like). The resource blocks include virtual resource blocks and physical resource blocks. A certain physical channel is mapped to a virtual resource block. The virtual resource blocks are mapped to physical resource blocks. One physical resource block is defined by a predetermined number of consecutive symbols in the time domain. One physical resource block is defined from a predetermined number of consecutive sub carriers in the frequency domain. The number of symbols and the number of sub carriers in one physical resource block are decided on the basis of a parameter set in accordance with a type of CP, a sub carrier interval, and/or a higher layer in the cell. For example, in a case in which the type of CP is the normal CP, and the sub carrier interval is 15 kHz, the number of symbols in one physical resource block is 7, and the number of sub carriers is 12. In this case, one physical resource block includes (7×12) resource elements. The physical resource blocks are numbered from 0 in the frequency domain. Further, two resource blocks in one sub frame corresponding to the same physical resource block number are defined as a physical resource block pair (a PRB pair or an RB pair). 
     A resource element group (REG) is used to define mapping of the resource element and the control channel. For example, the REG is used for mapping of the PDCCH, the PHICH, or the PCFICH. The REG is constituted by four consecutive resource elements which are in the same OFDM symbol and not used for the CRS in the same resource block. Further, the REG is constituted by first to fourth OFDM symbols in a first slot in a certain sub frame. 
     An enhanced resource element group (EREG) is used to define mapping of the resource elements and the enhanced control channel. For example, the EREG is used for mapping of the EPDCCH. One resource block pair is constituted by 16 EREGs. Each EREG is assigned a number of 0 to 15 for each resource block pair. Each EREG is constituted by 9 resource elements excluding resource elements used for the DMRS associated with the EPDCCH in one resource block pair. 
     Antenna Port in Present Embodiment 
     An antenna port is defined so that a propagation channel carrying a certain symbol can be inferred from a propagation channel carrying another symbol in the same antenna port. For example, different physical resources in the same antenna port can be assumed to be transmitted through the same propagation channel. In other words, for a symbol in a certain antenna port, it is possible to estimate and demodulate a propagation channel in accordance with the reference signal in the antenna port. Further, there is one resource grid for each antenna port. The antenna port is defined by the reference signal. Further, each reference signal can define a plurality of antenna ports. 
     In a case in which two antenna ports satisfy a predetermined condition, the two antenna ports can be regarded as being a quasi co-location (QCL). The predetermined condition is that a wide area characteristic of a propagation channel carrying a symbol in one antenna port can be inferred from a propagation channel carrying a symbol in another antenna port. The wide area characteristic includes a delay dispersion, a Doppler spread, a Doppler shift, an average gain, and/or an average delay. 
     Downlink Physical Channel in Present Embodiment 
     The PBCH is used to broadcast a master information block (MIB) which is broadcast information specific to a serving cell of the base station device  1 . The PBCH is transmitted only through the sub frame  0  in the radio frame. The MIB can be updated at intervals of 40 ms. The PBCH is repeatedly transmitted with a cycle of 10 ms. Specifically, initial transmission of the MIB is performed in the sub frame  0  in the radio frame satisfying a condition that a remainder obtained by dividing a system frame number (SFN) by 4 is 0, and retransmission (repetition) of the MIB is performed in the sub frame  0  in all the other radio frames. The SFN is a radio frame number (system frame number). The MIB is system information. For example, the MIB includes information indicating the SFN. 
     The PCFICH is used to transmit information related to the number of OFDM symbols used for transmission of the PDCCH. A region indicated by PCFICH is also referred to as a PDCCH region. The information transmitted through the PCFICH is also referred to as a control format indicator (CFI). 
     The PHICH is used to transmit an HARQ-ACK (an HARQ indicator, HARQ feedback, and response information) indicating ACKnowledgment (ACK) or negative ACKnowledgment (NACK) of uplink data (an uplink shared channel (UL-SCH)) received by the base station device  1 . For example, in a case in which the HARQ-ACK indicating ACK is received, corresponding uplink data is not retransmitted. For example, in a case in which the terminal device  2  receives the HARQ-ACK indicating NACK, the terminal device  2  retransmits corresponding uplink data through a predetermined uplink sub frame. A certain PHICH transmits the HARQ-ACK for certain uplink data. The base station device  1  transmits each HARQ-ACK to a plurality of pieces of uplink data included in the same PUSCH using a plurality of PHICHs. 
     The PDCCH and the EPDCCH are used to transmit downlink control information (DCI). Mapping of an information bit of the downlink control information is defined as a DCI format. The downlink control information includes a downlink grant and an uplink grant. The downlink grant is also referred to as a downlink assignment or a downlink allocation. 
     The PDCCH is transmitted by a set of one or more consecutive control channel elements (CCEs). The CCE includes 9 resource element groups (REGs). An REG includes 4 resource elements. In a case in which the PDCCH is constituted by n consecutive CCEs, the PDCCH starts with a CCE satisfying a condition that a remainder after dividing an index (number) i of the CCE by n is 0. 
     The EPDCCH is transmitted by a set of one or more consecutive enhanced control channel elements (ECCEs). The ECCE is constituted by a plurality of enhanced resource element groups (EREGs). 
     The downlink grant is used for scheduling of the PDSCH in a certain cell. The downlink grant is used for scheduling of the PDSCH in the same sub frame as a sub frame in which the downlink grant is transmitted. The uplink grant is used for scheduling of the PUSCH in a certain cell. The uplink grant is used for scheduling of a single PUSCH in a fourth sub frame from a sub frame in which the uplink grant is transmitted or later. 
     A cyclic redundancy check (CRC) parity bit is added to the DCI. The CRC parity bit is scrambled using a radio network temporary identifier (RNTI). The RNTI is an identifier that can be specified or set in accordance with a purpose of the DCI or the like. The RNTI is an identifier specified in a specification in advance, an identifier set as information specific to a cell, an identifier set as information specific to the terminal device  2 , or an identifier set as information specific to a group to which the terminal device  2  belongs. For example, in monitoring of the PDCCH or the EPDCCH, the terminal device  2  descrambles the CRC parity bit added to the DCI with a predetermined RNTI and identifies whether or not the CRC is correct. In a case in which the CRC is correct, the DCI is understood to be a DCI for the terminal device  2 . 
     The PDSCH is used to transmit downlink data (a downlink shared channel (DL-SCH)). Further, the PDSCH is also used to transmit control information of a higher layer. 
     The PMCH is used to transmit multicast data (a multicast channel (MCH)). 
     In the PDCCH region, a plurality of PDCCHs may be multiplexed according to frequency, time, and/or space. In the EPDCCH region, a plurality of EPDCCHs may be multiplexed according to frequency, time, and/or space. In the PDSCH region, a plurality of PDSCHs may be multiplexed according to frequency, time, and/or space. The PDCCH, the PDSCH, and/or the EPDCCH may be multiplexed according to frequency, time, and/or space. 
     Downlink Physical Signal in Present Embodiment 
     A synchronization signal is used for the terminal device  2  to obtain downlink synchronization in the frequency domain and/or the time domain. The synchronization signal includes a primary synchronization signal (PSS) and a secondary synchronization signal (SSS). The synchronization signal is placed in a predetermined sub frame in the radio frame. For example, in the TDD scheme, the synchronization signal is placed in the sub frames  0 ,  1 ,  5 , and  6  in the radio frame. In the FDD scheme, the synchronization signal is placed in the sub frames  0  and  5  in the radio frame. 
     The PSS may be used for coarse frame/timing synchronization (synchronization in the time domain) or cell group identification. The SSS may be used for more accurate frame timing synchronization or cell identification. In other words, frame timing synchronization and cell identification can be performed using the PSS and the SSS. 
     The downlink reference signal is used for the terminal device  2  to perform propagation path estimation of the downlink physical channel, propagation path correction, calculation of downlink channel state information (CSI), and/or measurement of positioning of the terminal device  2 . 
     The CRS is transmitted in the entire band of the sub frame. The CRS is used for receiving (demodulating) the PBCH, the PDCCH, the PHICH, the PCFICH, and the PDSCH. The CRS may be used for the terminal device  2  to calculate the downlink channel state information. The PBCH, the PDCCH, the PHICH, and the PCFICH are transmitted through the antenna port used for transmission of the CRS. The CRS supports the antenna port configurations of 1, 2, or 4. The CRS is transmitted through one or more of the antenna ports  0  to  3 . 
     The URS associated with the PDSCH is transmitted through a sub frame and a band used for transmission of the PDSCH with which the URS is associated. The URS is used for demodulation of the PDSCH to which the URS is associated. The URS associated with the PDSCH is transmitted through one or more of the antenna ports  5  and  7  to  14 . 
     The PDSCH is transmitted through an antenna port used for transmission of the CRS or the URS on the basis of the transmission mode and the DCI format. A DCI format 1A is used for scheduling of the PDSCH transmitted through an antenna port used for transmission of the CRS. A DCI format 2D is used for scheduling of the PDSCH transmitted through an antenna port used for transmission of the URS. 
     The DMRS associated with the EPDCCH is transmitted through a sub frame and a band used for transmission of the EPDCCH to which the DMRS is associated. The DMRS is used for demodulation of the EPDCCH with which the DMRS is associated. The EPDCCH is transmitted through an antenna port used for transmission of the DMRS. The DMRS associated with the EPDCCH is transmitted through one or more of the antenna ports  107  to  114 . 
     The CSI-RS is transmitted through a set sub frame. The resources in which the CSI-RS is transmitted are set by the base station device  1 . The CSI-RS is used for the terminal device  2  to calculate the downlink channel state information. The terminal device  2  performs signal measurement (channel measurement) using the CSI-RS. The CSI-RS supports setting of some or all of the antenna ports  1 ,  2 ,  4 ,  8 ,  12 ,  16 ,  24 , and  32 . The CSI-RS is transmitted through one or more of the antenna ports  15  to  46 . Further, an antenna port to be supported may be decided on the basis of a terminal device capability of the terminal device  2 , setting of an RRC parameter, and/or a transmission mode to be set. 
     Resources of the ZP CSI-RS are set by a higher layer. Resources of the ZP CSI-RS are transmitted with zero output power. In other words, the resources of the ZP CSI-RS are not transmitted. The ZP PDSCH and the EPDCCH are not transmitted in the resources in which the ZP CSI-RS is set. For example, the resources of the ZP CSI-RS are used for a neighbor cell to transmit the NZP CSI-RS. Further, for example, the resources of the ZP CSI-RS are used to measure the CSI-IM. 
     Resources of the CSI-IM are set by the base station device  1 . The resources of the CSI-IM are resources used for measuring interference in CSI measurement. The resources of the CSI-IM can be set to overlap some of the resources of the ZP CSI-RS. For example, in a case in which the resources of the CSI-IM are set to overlap some of the resources of the ZP CSI-RS, a signal from a cell performing the CSI measurement is not transmitted in the resources. In other words, the base station device  1  does not transmit the PDSCH, the EPDCCH, or the like in the resources set by the CSI-IM. Therefore, the terminal device  2  can perform the CSI measurement efficiently. 
     The MBSFN RS is transmitted in the entire band of the sub frame used for transmission of the PMCH. The MBSFN RS is used for demodulation of the PMCH. The PMCH is transmitted through an antenna port used for transmission of the MBSFN RS. The MBSFN RS is transmitted through the antenna port  4 . 
     The PRS is used for the terminal device  2  to measure positioning of the terminal device  2 . The PRS is transmitted through the antenna port  6 . 
     The TRS can be mapped only to predetermined sub frames. For example, the TRS is mapped to the sub frames  0  and  5 . Further, the TRS can use a configuration similar to a part or all of the CRS. For example, in each resource block, a position of a resource element to which the TRS is mapped can be caused to coincide with a position of a resource element to which the CRS of the antenna port  0  is mapped. Further, a sequence (value) used for the TRS can be decided on the basis of information set through the PBCH, the PDCCH, the EPDCCH, or the PDSCH (RRC signaling). A sequence (value) used for the TRS can be decided on the basis of a parameter such as a cell ID (for example, a physical layer cell identifier), a slot number, or the like. A sequence (value) used for the TRS can be decided by a method (formula) different from that of a sequence (value) used for the CRS of the antenna port  0 . 
     Uplink Physical Signal in Present Embodiment 
     The PUCCH is a physical channel used for transmitting uplink control information (UCI). The uplink control information includes downlink channel state information (CSI), a scheduling request (SR) indicating a request for PUSCH resources, and a HARQ-ACK to downlink data (a transport block (TB) or a downlink-shared channel (DL-SCH)). The HARQ-ACK is also referred to as ACK/NACK, HARQ feedback, or response information. Further, the HARQ-ACK to downlink data indicates ACK, NACK, or DTX. 
     The PUSCH is a physical channel used for transmitting uplink data (uplink-shared channel (UL-SCH)). Further, the PUSCH may be used to transmit the HARQ-ACK and/or the channel state information together with uplink data. Further, the PUSCH may be used to transmit only the channel state information or only the HARQ-ACK and the channel state information. 
     The PRACH is a physical channel used for transmitting a random access preamble. The PRACH can be used for the terminal device  2  to obtain synchronization in the time domain with the base station device  1 . Further, the PRACH is also used to indicate an initial connection establishment procedure (process), a handover procedure, a connection re-establishment procedure, synchronization (timing adjustment) for uplink transmission, and/or a request for PUSCH resources. 
     In the PUCCH region, a plurality of PUCCHs are frequency, time, space, and/or code multiplexed. In the PUSCH region, a plurality of PUSCHs may be frequency, time, space, and/or code multiplexed. The PUCCH and the PUSCH may be frequency, time, space, and/or code multiplexed. The PRACH may be placed over a single sub frame or two sub frames. A plurality of PRACHs may be code-multiplexed. 
     Uplink Physical Channel in Present Embodiment 
     The uplink DMRS is associated with transmission of the PUSCH or the PUCCH. The DMRS is time-multiplexed with the PUSCH or the PUCCH. The base station device  1  may use the DMRS to perform the propagation path correction of the PUSCH or the PUCCH. In the description of the present embodiment, the transmission of the PUSCH also includes multiplexing and transmitting the PUSCH and DMRS. In the description of the present embodiment, the transmission of the PUCCH also includes multiplexing and transmitting the PUCCH and the DMRS. Further, the uplink DMRS is also referred to as an UL-DMRS. The SRS is not associated with the transmission of the PUSCH or the PUCCH. The base station device  1  may use the SRS to measure the uplink channel state. 
     The SRS is transmitted using the last SC-FDMA symbol in the uplink sub frame. In other words, the SRS is placed in the last SC-FDMA symbol in the uplink sub frame. The terminal device  2  can restrict simultaneous transmission of the SRS, the PUCCH, the PUSCH, and/or the PRACH in a certain SC-FDMA symbol of a certain cell. The terminal device  2  can transmit the PUSCH and/or the PUCCH using the SC-FDMA symbol excluding the last SC-FDMA symbol in a certain uplink sub frame of a certain cell in the uplink sub frame and transmit the SRS using the last SC-FDMA symbol in the uplink sub frame. In other words, the terminal device  2  can transmit the SRS, the PUSCH, and the PUCCH in a certain uplink sub frame of a certain cell. 
     In the SRS, a trigger type 0 SRS and a trigger type 1 SRS are defined as SRSs having different trigger types. The trigger type 0 SRS is transmitted in a case in which a parameter related to the trigger type 0 SRS is set by signaling of a higher layer. The trigger type 1 SRS is transmitted in a case in which a parameter related to the trigger type 1 SRS is set by signaling of the higher layer, and transmission is requested by an SRS request included in the DCI format 0, 1A, 2B, 2C, 2D, or 4. Further, the SRS request is included in both FDD and TDD for the DCI format 0, 1A, or 4 and included only in TDD for the DCI format 2B, 2C, or 2D. In a case in which the transmission of the trigger type 0 SRS and the transmission of the trigger type 1 SRS occur in the same sub frame of the same serving cell, a priority is given to the transmission of the trigger type 1 SRS. 
     Configuration Example of Base Station Device  1  in Present Embodiment 
       FIG.  3    is a schematic block diagram illustrating a configuration of the base station device  1  of the present embodiment. As illustrated in  FIG.  3   , the base station device  1  includes a higher layer processing unit  101 , a control unit  103 , a receiving unit  105 , a transmitting unit  107 , and a transceiving antenna  109 . Further, the receiving unit  105  includes a decoding unit  1051 , a demodulating unit  1053 , a demultiplexing unit  1055 , a wireless receiving unit  1057 , and a channel measuring unit  1059 . Further, the transmitting unit  107  includes an encoding unit  1071 , a modulating unit  1073 , a multiplexing unit  1075 , a wireless transmitting unit  1077 , and a downlink reference signal generating unit  1079 . 
     The higher layer processing unit  101  performs processes of a medium access control (MAC) layer, a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a radio resource control (RRC) layer. Further, the higher layer processing unit  101  generates control information to control the receiving unit  105  and the transmitting unit  107  and outputs the control information to the control unit  103 . 
     The control unit  103  controls the receiving unit  105  and the transmitting unit  107  on the basis of the control information from the higher layer processing unit  101 . The control unit  103  generates control information to be transmitted to the higher layer processing unit  101  and outputs the control information to the higher layer processing unit  101 . The control unit  103  receives a decoded signal from the decoding unit  1051  and a channel estimation result from the channel measuring unit  1059 . The control unit  103  outputs a signal to be encoded to the encoding unit  1071 . Further, the control unit  103  may be used to control the whole or a part of the base station device  1 . 
     The higher layer processing unit  101  performs a process and management related to radio resource control, sub frame setting, scheduling control, and/or CSI report control. The process and the management in the higher layer processing unit  101  are performed for each terminal device or in common to terminal devices connected to the base station device. The process and the management in the higher layer processing unit  101  may be performed only by the higher layer processing unit  101  or may be acquired from a higher node or another base station device. 
     In the radio resource control in the higher layer processing unit  101 , generation and/or management of downlink data (transport block), system information, an RRC message (RRC parameter), and/or a MAC control element (CE) are performed. 
     In a sub frame setting in the higher layer processing unit  101 , management of a sub frame setting, a sub frame pattern setting, an uplink-downlink setting, an uplink reference UL-DL setting, and/or a downlink reference UL-DL setting is performed. Further, the sub frame setting in the higher layer processing unit  101  is also referred to as a base station sub frame setting. Further, the sub frame setting in the higher layer processing unit  101  can be decided on the basis of an uplink traffic volume and a downlink traffic volume. Further, the sub frame setting in the higher layer processing unit  101  can be decided on the basis of a scheduling result of scheduling control in the higher layer processing unit  101 . 
     In the scheduling control in the higher layer processing unit  101 , a frequency and a sub frame to which the physical channel (the PDSCH and the PUSCH) is allocated, a coding rate, a modulation scheme, and transmission power of the physical channels (the PDSCH and the PUSCH), and the like are decided on the basis of the received channel state information, an estimation value, a channel quality, or the like of a propagation path input from the channel measuring unit  1059 , and the like. For example, the control unit  103  generates the control information (DCI format) on the basis of the scheduling result of the scheduling control in the higher layer processing unit  101 . 
     In the CSI report control in the higher layer processing unit  101 , the CSI report of the terminal device  2  is controlled. For example, a settings related to the CSI reference resources assumed to calculate the CSI in the terminal device  2  is controlled. 
     Under the control from the control unit  103 , the receiving unit  105  receives a signal transmitted from the terminal device  2  via the transceiving antenna  109 , performs a reception process such as demultiplexing, demodulation, and decoding, and outputs information which has undergone the reception process to the control unit  103 . Further, the reception process in the receiving unit  105  is performed on the basis of a setting which is specified in advance or a setting notified from the base station device  1  to the terminal device  2 . 
     The wireless receiving unit  1057  performs conversion into an intermediate frequency (down conversion), removal of an unnecessary frequency component, control of an amplification level such that a signal level is appropriately maintained, quadrature demodulation based on an in-phase component and a quadrature component of a received signal, conversion from an analog signal into a digital signal, removal of a guard interval (GI), and/or extraction of a signal in the frequency domain by fast Fourier transform (FFT) on the uplink signal received via the transceiving antenna  109 . 
     The demultiplexing unit  1055  separates the uplink channel such as the PUCCH or the PUSCH and/or uplink reference signal from the signal input from the wireless receiving unit  1057 . The demultiplexing unit  1055  outputs the uplink reference signal to the channel measuring unit  1059 . The demultiplexing unit  1055  compensates the propagation path for the uplink channel from the estimation value of the propagation path input from the channel measuring unit  1059 . 
     The demodulating unit  1053  demodulates the reception signal for the modulation symbol of the uplink channel using a modulation scheme such as binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), 16 quadrature amplitude modulation (QAM), 64 QAM, or 256 QAM. The demodulating unit  1053  performs separation and demodulation of a MIMO multiplexed uplink channel. 
     The decoding unit  1051  performs a decoding process on encoded bits of the demodulated uplink channel. The decoded uplink data and/or uplink control information are output to the control unit  103 . The decoding unit  1051  performs a decoding process on the PUSCH for each transport block. 
     The channel measuring unit  1059  measures the estimation value, a channel quality, and/or the like of the propagation path from the uplink reference signal input from the demultiplexing unit  1055 , and outputs the estimation value, a channel quality, and/or the like of the propagation path to the demultiplexing unit  1055  and/or the control unit  103 . For example, the estimation value of the propagation path for propagation path compensation for the PUCCH or the PUSCH is measured through the UL-DMRS, and an uplink channel quality is measured through the SRS. 
     The transmitting unit  107  carries out a transmission process such as encoding, modulation, and multiplexing on downlink control information and downlink data input from the higher layer processing unit  101  under the control of the control unit  103 . For example, the transmitting unit  107  generates and multiplexes the PHICH, the PDCCH, the EPDCCH, the PDSCH, and the downlink reference signal and generates a transmission signal. Further, the transmission process in the transmitting unit  107  is performed on the basis of a setting which is specified in advance, a setting notified from the base station device  1  to the terminal device  2 , or a setting notified through the PDCCH or the EPDCCH transmitted through the same sub frame. 
     The encoding unit  1071  encodes the HARQ indicator (HARQ-ACK), the downlink control information, and the downlink data input from the control unit  103  using a predetermined coding scheme such as block coding, convolutional coding, turbo coding, or the like. The modulating unit  1073  modulates the encoded bits input from the encoding unit  1071  using a predetermined modulation scheme such as BPSK, QPSK, 16 QAM, 64 QAM, or 256 QAM. The downlink reference signal generating unit  1079  generates the downlink reference signal on the basis of a physical cell identification (PCI), an RRC parameter set in the terminal device  2 , and the like. The multiplexing unit  1075  multiplexes a modulated symbol and the downlink reference signal of each channel and arranges resulting data in a predetermined resource element. 
     The wireless transmitting unit  1077  performs processes such as conversion into a signal in the time domain by inverse fast Fourier transform (IFFT), addition of the guard interval, generation of a baseband digital signal, conversion in an analog signal, quadrature modulation, conversion from a signal of an intermediate frequency into a signal of a high frequency (up conversion), removal of an extra frequency component, and amplification of power on the signal from the multiplexing unit  1075 , and generates a transmission signal. The transmission signal output from the wireless transmitting unit  1077  is transmitted through the transceiving antenna  109 . 
     Configuration Example of Base Station Device  1  in Present Embodiment 
       FIG.  4    is a schematic block diagram illustrating a configuration of the terminal device  2  of the present embodiment. As illustrated in  FIG.  4   , the terminal device  2  includes a higher layer processing unit  201 , a control unit  203 , a receiving unit  205 , a transmitting unit  207 , and a transceiving antenna  209 . Further, the receiving unit  205  includes a decoding unit  2051 , a demodulating unit  2053 , a demultiplexing unit  2055 , a wireless receiving unit  2057 , and a channel measuring unit  2059 . Further, the transmitting unit  207  includes an encoding unit  2071 , a modulating unit  2073 , a multiplexing unit  2075 , a wireless transmitting unit  2077 , and an uplink reference signal generating unit  2079 . 
     The higher layer processing unit  201  outputs uplink data (transport block) to the control unit  203 . The higher layer processing unit  201  performs processes of a medium access control (MAC) layer, a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a radio resource control (RRC) layer. Further, the higher layer processing unit  201  generates control information to control the receiving unit  205  and the transmitting unit  207  and outputs the control information to the control unit  203 . 
     The control unit  203  controls the receiving unit  205  and the transmitting unit  207  on the basis of the control information from the higher layer processing unit  201 . The control unit  203  generates control information to be transmitted to the higher layer processing unit  201  and outputs the control information to the higher layer processing unit  201 . The control unit  203  receives a decoded signal from the decoding unit  2051  and a channel estimation result from the channel measuring unit  2059 . The control unit  203  outputs a signal to be encoded to the encoding unit  2071 . Further, the control unit  203  may be used to control the whole or a part of the terminal device  2 . 
     The higher layer processing unit  201  performs a process and management related to radio resource control, sub frame setting, scheduling control, and/or CSI report control. The process and the management in the higher layer processing unit  201  are performed on the basis of a setting which is specified in advance and/or a setting based on control information set or notified from the base station device  1 . For example, the control information from the base station device  1  includes the RRC parameter, the MAC control element, or the DCI. 
     In the radio resource control in the higher layer processing unit  201 , the setting information in the terminal device  2  is managed. In the radio resource control in the higher layer processing unit  201 , generation and/or management of uplink data (transport block), system information, an RRC message (RRC parameter), and/or a MAC control element (CE) are performed. 
     In the sub frame setting in the higher layer processing unit  201 , the sub frame setting in the base station device  1  and/or a base station device different from the base station device  1  is managed. The sub frame setting includes an uplink or downlink setting for the sub frame, a sub frame pattern setting, an uplink-downlink setting, an uplink reference UL-DL setting, and/or a downlink reference UL-DL setting. Further, the sub frame setting in the higher layer processing unit  201  is also referred to as a terminal sub frame setting. 
     In the scheduling control in the higher layer processing unit  201 , control information for controlling scheduling on the receiving unit  205  and the transmitting unit  207  is generated on the basis of the DCI (scheduling information) from the base station device  1 . 
     In the CSI report control in the higher layer processing unit  201 , control related to the report of the CSI to the base station device  1  is performed. For example, in the CSI report control, a setting related to the CSI reference resources assumed for calculating the CSI by the channel measuring unit  2059  is controlled. In the CSI report control, resource (timing) used for reporting the CSI is controlled on the basis of the DCI and/or the RRC parameter. 
     Under the control from the control unit  203 , the receiving unit  205  receives a signal transmitted from the base station device  1  via the transceiving antenna  209 , performs a reception process such as demultiplexing, demodulation, and decoding, and outputs information which has undergone the reception process to the control unit  203 . Further, the reception process in the receiving unit  205  is performed on the basis of a setting which is specified in advance or a notification from the base station device  1  or a setting. 
     The wireless receiving unit  2057  performs conversion into an intermediate frequency (down conversion), removal of an unnecessary frequency component, control of an amplification level such that a signal level is appropriately maintained, quadrature demodulation based on an in-phase component and a quadrature component of a received signal, conversion from an analog signal into a digital signal, removal of a guard interval (GI), and/or extraction of a signal in the frequency domain by fast Fourier transform (FFT) on the uplink signal received via the transceiving antenna  209 . 
     The demultiplexing unit  2055  separates the downlink channel such as the PHICH, PDCCH, EPDCCH, or PDSCH, downlink synchronization signal and/or downlink reference signal from the signal input from the wireless receiving unit  2057 . The demultiplexing unit  2055  outputs the uplink reference signal to the channel measuring unit  2059 . The demultiplexing unit  2055  compensates the propagation path for the uplink channel from the estimation value of the propagation path input from the channel measuring unit  2059 . 
     The demodulating unit  2053  demodulates the reception signal for the modulation symbol of the downlink channel using a modulation scheme such as BPSK, QPSK, 16 QAM, 64 QAM, or 256 QAM. The demodulating unit  2053  performs separation and demodulation of a MIMO multiplexed downlink channel. 
     The decoding unit  2051  performs a decoding process on encoded bits of the demodulated downlink channel. The decoded downlink data and/or downlink control information are output to the control unit  203 . The decoding unit  2051  performs a decoding process on the PDSCH for each transport block. 
     The channel measuring unit  2059  measures the estimation value, a channel quality, and/or the like of the propagation path from the downlink reference signal input from the demultiplexing unit  2055 , and outputs the estimation value, a channel quality, and/or the like of the propagation path to the demultiplexing unit  2055  and/or the control unit  203 . The downlink reference signal used for measurement by the channel measuring unit  2059  may be decided on the basis of at least a transmission mode set by the RRC parameter and/or other RRC parameters. For example, the estimation value of the propagation path for performing the propagation path compensation on the PDSCH or the EPDCCH is measured through the DL-DMRS. The estimation value of the propagation path for performing the propagation path compensation on the PDCCH or the PDSCH and/or the downlink channel for reporting the CSI are measured through the CRS. The downlink channel for reporting the CSI is measured through the CSI-RS. The channel measuring unit  2059  calculates a reference signal received power (RSRP) and/or a reference signal received quality (RSRQ) on the basis of the CRS, the CSI-RS, or the discovery signal, and outputs the RSRP and/or the RSRQ to the higher layer processing unit  201 . 
     The transmitting unit  207  performs a transmission process such as encoding, modulation, and multiplexing on the uplink control information and the uplink data input from the higher layer processing unit  201  under the control of the control unit  203 . For example, the transmitting unit  207  generates and multiplexes the uplink channel such as the PUSCH or the PUCCH and/or the uplink reference signal, and generates a transmission signal. Further, the transmission process in the transmitting unit  207  is performed on the basis of a setting which is specified in advance or a setting set or notified from the base station device  1 . 
     The encoding unit  2071  encodes the HARQ indicator (HARQ-ACK), the uplink control information, and the uplink data input from the control unit  203  using a predetermined coding scheme such as block coding, convolutional coding, turbo coding, or the like. The modulating unit  2073  modulates the encoded bits input from the encoding unit  2071  using a predetermined modulation scheme such as BPSK, QPSK, 16 QAM, 64 QAM, or 256 QAM. The uplink reference signal generating unit  2079  generates the uplink reference signal on the basis of an RRC parameter set in the terminal device  2 , and the like. The multiplexing unit  2075  multiplexes a modulated symbol and the uplink reference signal of each channel and arranges resulting data in a predetermined resource element. 
     The wireless transmitting unit  2077  performs processes such as conversion into a signal in the time domain by inverse fast Fourier transform (IFFT), addition of the guard interval, generation of a baseband digital signal, conversion in an analog signal, quadrature modulation, conversion from a signal of an intermediate frequency into a signal of a high frequency (up conversion), removal of an extra frequency component, and amplification of power on the signal from the multiplexing unit  2075 , and generates a transmission signal. The transmission signal output from the wireless transmitting unit  2077  is transmitted through the transceiving antenna  209 . 
     Signaling of Control Information in Present Embodiment 
     The base station device  1  and the terminal device  2  can use various methods for signaling (notification, broadcasting, or setting) of the control information. The signaling of the control information can be performed in various layers (layers). The signaling of the control information includes signaling of the physical layer which is signaling performed through the physical layer, RRC signaling which is signaling performed through the RRC layer, and MAC signaling which is signaling performed through the MAC layer. The RRC signaling is dedicated RRC signaling for notifying the terminal device  2  of the control information specific or a common RRC signaling for notifying of the control information specific to the base station device  1 . The signaling used by a layer higher than the physical layer such as RRC signaling and MAC signaling is also referred to as signaling of the higher layer. 
     The RRC signaling is implemented by signaling the RRC parameter. The MAC signaling is implemented by signaling the MAC control element. The signaling of the physical layer is implemented by signaling the downlink control information (DCI) or the uplink control information (UCI). The RRC parameter and the MAC control element are transmitted using the PDSCH or the PUSCH. The DCI is transmitted using the PDCCH or the EPDCCH. The UCI is transmitted using the PUCCH or the PUSCH. The RRC signaling and the MAC signaling are used for signaling semi-static control information and are also referred to as semi-static signaling. The signaling of the physical layer is used for signaling dynamic control information and also referred to as dynamic signaling. The DCI is used for scheduling of the PDSCH or scheduling of the PUSCH. The UCI is used for the CSI report, the HARQ-ACK report, and/or the scheduling request (SR). 
     Details of Downlink Control Information in Present Embodiment 
     The DCI is notified using the DCI format having a field which is specified in advance. Predetermined information bits are mapped to the field specified in the DCI format. The DCI notifies of downlink scheduling information, uplink scheduling information, sidelink scheduling information, a request for a non-periodic CSI report, or an uplink transmission power command. 
     The DCI format monitored by the terminal device  2  is decided in accordance with the transmission mode set for each serving cell. In other words, a part of the DCI format monitored by the terminal device  2  can differ depending on the transmission mode. For example, the terminal device  2  in which a downlink transmission mode  1  is set monitors the DCI format 1A and the DCI format 1. For example, the terminal device  2  in which a downlink transmission mode  4  is set monitors the DCI format 1A and the DCI format 2. For example, the terminal device  2  in which an uplink transmission mode  1  is set monitors the DCI format 0. For example, the terminal device  2  in which an uplink transmission mode  2  is set monitors the DCI format 0 and the DCI format 4. 
     A control region in which the PDCCH for notifying the terminal device  2  of the DCI is placed is not notified of, and the terminal device  2  detects the DCI for the terminal device  2  through blind decoding (blind detection). Specifically, the terminal device  2  monitors a set of PDCCH candidates in the serving cell. The monitoring indicates that decoding is attempted in accordance with all the DCI formats to be monitored for each of the PDCCHs in the set. For example, the terminal device  2  attempts to decode all aggregation levels, PDCCH candidates, and DCI formats which are likely to be transmitted to the terminal device  2 . The terminal device  2  recognizes the DCI (PDCCH) which is successfully decoded (detected) as the DCI (PDCCH) for the terminal device  2 . 
     A cyclic redundancy check (CRC) is added to the DCI. The CRC is used for the DCI error detection and the DCI blind detection. A CRC parity bit (CRC) is scrambled using the RNTI. The terminal device  2  detects whether or not it is a DCI for the terminal device  2  on the basis of the RNTI. Specifically, the terminal device  2  performs de-scrambling on the bit corresponding to the CRC using a predetermined RNTI, extracts the CRC, and detects whether or not the corresponding DCI is correct. 
     The RNTI is specified or set in accordance with a purpose or a use of the DCI. The RNTI includes a cell-RNTI (C-RNTI), a semi persistent scheduling C-RNTI (SPS C-RNTI), a system information-RNTI (SI-RNTI), a paging-RNTI (P-RNTI), a random access-RNTI (RA-RNTI), a transmit power control-PUCCH-RNTI (TPC-PUCCH-RNTI), a transmit power control-PUSCH-RNTI (TPC-PUSCH-RNTI), a temporary C-RNTI, a multimedia broadcast multicast services (MBMS)-RNTI (M-RNTI)), and an eIMTA-RNTI. 
     The C-RNTI and the SPS C-RNTI are RNTIs which are specific to the terminal device  2  in the base station device  1  (cell), and serve as identifiers identifying the terminal device  2 . The C-RNTI is used for scheduling the PDSCH or the PUSCH in a certain sub frame. The SPS C-RNTI is used to activate or release periodic scheduling of resources for the PDSCH or the PUSCH. A control channel having a CRC scrambled using the SI-RNTI is used for scheduling a system information block (SIB). A control channel with a CRC scrambled using the P-RNTI is used for controlling paging. A control channel with a CRC scrambled using the RA-RNTI is used for scheduling a response to the RACH. A control channel having a CRC scrambled using the TPC-PUCCH-RNTI is used for power control of the PUCCH. A control channel having a CRC scrambled using the TPC-PUSCH-RNTI is used for power control of the PUSCH. A control channel with a CRC scrambled using the temporary C-RNTI is used by a mobile station device in which no C-RNTI is set or recognized. A control channel with CRC scrambled using the M-RNTI is used for scheduling the MBMS. A control channel with a CRC scrambled using the eIMTA-RNTI is used for notifying of information related to a TDD UL/DL setting of a TDD serving cell in dynamic TDD (eIMTA). Further, the DCI format may be scrambled using a new RNTI instead of the above RNTI. 
     The scheduling information (downlink scheduling information, uplink scheduling information, and sidelink scheduling information) includes information for scheduling in units of resource blocks or in units of resource block groups as scheduling in the frequency domain. The resource block group is a set of consecutive resource blocks and indicates resources allocated to the terminal device to be scheduled. The size of the resource block group is decided in accordance with a system bandwidth. 
     Details of Downlink Control Channel in Present Embodiment 
     The DCI is transmitted using the PDCCH or the EPDCCH. The terminal device  2  monitors a set of PDCCH candidates and/or a set of EPDCCH candidates of one or more activated serving cells set by RRC signaling. Here, the monitoring means that the PDCCH and/or the EPDCCH in the set corresponding to all the DCI formats to be monitored is attempted to be decoded. 
     A set of PDCCH candidates or a set of EPDCCH candidates is also referred to as a search space. In the search space, a shared search space (CSS) and a terminal specific search space (USS) are defined. The CSS may be defined only for the search space for the PDCCH. 
     A common search space (CSS) is a search space set on the basis of a parameter specific to the base station device  1  and/or a parameter which is specified in advance. For example, the CSS is a search space used in common to a plurality of terminal devices. Therefore, the base station device  1  maps a control channel common to a plurality of terminal devices to the CSS, and thus resources for transmitting the control channel are reduced. 
     A UE-specific search space (USS) is a search space set using at least a parameter specific to the terminal device  2 . Therefore, the USS is a search space specific to the terminal device  2 , and it is possible to individually transmit the control channel specific to the terminal device  2 . For this reason, the base station device  1  can efficiently map the control channels specific to a plurality of terminal devices. 
     The USS may be set to be used in common to a plurality of terminal devices. Since a common USS is set in a plurality of terminal devices, a parameter specific to the terminal device  2  is set to be the same value among a plurality of terminal devices. For example, a unit set to the same parameter among a plurality of terminal devices is a cell, a transmission point, a group of predetermined terminal devices, or the like. 
     The search space of each aggregation level is defined by a set of PDCCH candidates. Each PDCCH is transmitted using one or more CCE sets. The number of CCEs used in one PDCCH is also referred to as an aggregation level. For example, the number of CCEs used in one PDCCH is 1, 2, 4, or 8. 
     The search space of each aggregation level is defined by a set of EPDCCH candidates. Each EPDCCH is transmitted using one or more enhanced control channel element (ECCE) sets. The number of ECCEs used in one EPDCCH is also referred to as an aggregation level. For example, the number of ECCEs used in one EPDCCH is 1, 2, 4, 8, 16, or 32. 
     The number of PDCCH candidates or the number of EPDCCH candidates is decided on the basis of at least the search space and the aggregation level. For example, in the CSS, the number of PDCCH candidates in the aggregation levels  4  and  8  are 4 and 2, respectively. For example, in the USS, the number of PDCCH candidates in the aggregation  1 ,  2 ,  4 , and  8  are 6, 6, 2, and 2, respectively. 
     Each ECCE includes a plurality of EREGs. The EREG is used to define mapping to the resource element of the EPDCCH. 16 EREGs which are assigned numbers of 0 to 15 are defined in each RB pair. In other words, an EREG  0  to an EREG  15  are defined in each RB pair. For each RB pair, the EREG  0  to the EREG  15  are preferentially defined at regular intervals in the frequency direction for resource elements other than resource elements to which a predetermined signal and/or channel is mapped. For example, the EREG is not defined for a resource element to which a demodulation reference signal associated with an EPDCCH transmitted through antenna ports  107  to  110  is mapped. 
     The number of ECCEs used in one EPDCCH depends on an EPDCCH format and is decided on the basis of other parameters. The number of ECCEs used in one EPDCCH is also referred to as an aggregation level. For example, the number of ECCEs used in one EPDCCH is decided on the basis of the number of resource elements which can be used for transmission of the EPDCCH in one RB pair, a transmission method of the EPDCCH, and the like. For example, the number of ECCEs used in one EPDCCH is 1, 2, 4, 8, 16, or 32. Further, the number of EREGs used in one ECCE is decided on the basis of a type of sub frame and a type of cyclic prefix and is 4 or 8. Distributed transmission and localized transmission are supported as the transmission method of the EPDCCH. 
     The distributed transmission or the localized transmission can be used for the EPDCCH. The distributed transmission and the localized transmission differ in mapping of the ECCE to the EREG and the RB pair. For example, in the distributed transmission, one ECCE is configured using EREGs of a plurality of RB pairs. In the localized transmission, one ECCE is configured using an EREG of one RB pair. 
     The base station device  1  performs a setting related to the EPDCCH in the terminal device  2 . The terminal device  2  monitors a plurality of EPDCCHs on the basis of the setting from the base station device  1 . A set of RB pairs that the terminal device  2  monitors the EPDCCH can be set. The set of RB pairs is also referred to as an EPDCCH set or an EPDCCH-PRB set. One or more EPDCCH sets can be set in one terminal device  2 . Each EPDCCH set includes one or more RB pairs. Further, the setting related to the EPDCCH can be individually performed for each EPDCCH set. 
     The base station device  1  can set a predetermined number of EPDCCH sets in the terminal device  2 . For example, up to two EPDCCH sets can be set as an EPDCCH set  0  and/or an EPDCCH set  1 . Each of the EPDCCH sets can be constituted by a predetermined number of RB pairs. Each EPDCCH set constitutes one set of ECCEs. The number of ECCEs configured in one EPDCCH set is decided on the basis of the number of RB pairs set as the EPDCCH set and the number of EREGs used in one ECCE. In a case in which the number of ECCEs configured in one EPDCCH set is N, each EPDCCH set constitutes ECCEs  0  to N−1. For example, in a case in which the number of EREGs used in one ECCE is 4, the EPDCCH set constituted by 4 RB pairs constitutes 16 ECCEs. 
     Details of Channel State Information in Present Embodiment 
     The terminal device  2  reports the CSI to the base station device  1 . The time and frequency resources used to report the CSI are controlled by the base station device  1 . In the terminal device  2 , a setting related to the CSI is performed through the RRC signaling from the base station device  1 . In the terminal device  2 , one or more CSI processes are set in a predetermined transmission mode. The CSI reported by the terminal device  2  corresponds to the CSI process. For example, the CSI process is a unit of control or setting related to the CSI. For each of the CSI processes, a setting related to the CSI-RS resources, the CSI-IM resources, the periodic CSI report (for example, a period and an offset of a report), and/or the non-periodic CSI report can be independently set. 
     The CSI includes a channel quality indicator (CQI), a precoding matrix indicator (PMI), a precoding type indicator (PTI), a rank indicator (RI), and/or a CSI-RS resource indicator (CRI). The RI indicates the number of transmission layers (the number of ranks). The PMI is information indicating a precoding matrix which is specified in advance. The PMI indicates one precoding matrix by one piece of information or two pieces of information. In a case in which two pieces of information are used, the PMI is also referred to as a first PMI and a second PMI. The CQI is information indicating a combination of a modulation scheme and a coding rate which are specified in advance. The CRI is information (single instance) indicating one CSI-RS resource selected from two or more CSI-RS resources in a case in which the two or more CSI-RS resources are set in one CSI process. The terminal device  2  reports the CSI to recommend to the base station device  1 . The terminal device  2  reports the CQI satisfying a predetermined reception quality for each transport block (codeword). 
     In the CRI report, one CSI-RS resource is selected from the CSI-RS resources to be set. In a case in which the CRI is reported, the PMI, the CQI, and the RI to be reported are calculated (selected) on the basis of the reported CRI. For example, in a case in which the CSI-RS resources to be set are precoded, the terminal device  2  reports the CRI, so that precoding (beam) suitable for the terminal device  2  is reported. 
     A sub frame (reporting instances) in which periodic CSI reporting can be performed are decided by a report period and a sub frame offset set by a parameter of a higher layer (a CQIPMI index, an RI index, and a CRI index). Further, the parameter of the higher layer can be independently set in a sub frame set to measure the CSI. In a case in which only one piece of information is set in a plurality of sub frame sets, that information can be set in common to the sub frame sets. In each serving cell, one or more periodic CSI reports are set by the signaling of the higher layer. 
     A CSI report type supports a PUCCH CSI report mode. The CSI report type is also referred to as a PUCCH report type. A type 1 report supports feedback of the CQI for a terminal selection sub band. A type 1a report supports feedbank of a sub band CQI and a second PMI. Type 2, type 2b, type 2c reports support feedback of a wideband CQI and a PMI. A type 2a report supports feedback of a wideband PMI. A type 3 report supports feedback of the RI. A type 4 report supports feedback of the wideband CQI. A type 5 report supports feedback of the RI and the wideband PMI. A type 6 report supports feedback of the RI and the PTI. A type 7 report supports feedback of the CRI and the RI. A type 8 report supports feedback of the CRI, the RI, and the wideband PMI. A type 9 report supports feedback of the CRI, the RI, and the PTI. A type 10 report supports feedback of the CRI. 
     In the terminal device  2 , information related to the CSI measurement and the CSI report is set from the base station device  1 . The CSI measurement is performed on the basis of the reference signal and/or the reference resources (for example, the CRS, the CSI-RS, the CSI-IM resources, and/or the DRS). The reference signal used for the CSI measurement is decided on the basis of the setting of the transmission mode or the like. The CSI measurement is performed on the basis of channel measurement and interference measurement. For example, power of a desired cell is measured through the channel measurement. Power and noise power of a cell other than a desired cell are measured through the interference measurement. 
     For example, in the CSI measurement, the terminal device  2  performs the channel measurement and the interference measurement on the basis of the CRS. For example, in the CSI measurement, the terminal device  2  performs the channel measurement on the basis of the CSI-RS and performs the interference measurement on the basis of the CRS. For example, in the CSI measurement, the terminal device  2  performs the channel measurement on the basis of the CSI-RS and performs the interference measurement on the basis of the CSI-IM resources. 
     The CSI process is set as information specific to the terminal device  2  through signaling of the higher layer. In the terminal device  2 , one or more CSI processes are set, and the CSI measurement and the CSI report are performed on the basis of the setting of the CSI process. For example, in a case in which a plurality of CSI processes are set, the terminal device  2  independently reports a plurality of CSIs based on the CSI processes. Each CSI process includes a setting for the cell state information, an identifier of the CSI process, setting information related to the CSI-RS, setting information related to the CSI-IM, a sub frame pattern set for the CSI report, setting information related to the periodic CSI report, setting information related to the non-periodic CSI report. Further, the setting for the cell state information may be common to a plurality of CSI processes. 
     The terminal device  2  uses the CSI reference resources to perform the CSI measurement. For example, the terminal device  2  measures the CSI in a case in which the PDSCH is transmitted using a group of downlink physical resource blocks indicated by the CSI reference resources. In a case in which the CSI sub frame set is set through the signaling of the higher layer, each CSI reference resource belongs to one of the CSI sub frame sets and does not belong to both of the CSI sub frame sets. 
     In the frequency direction, the CSI reference resource is defined by the group of downlink physical resource blocks corresponding to the bands associated with the value of the measured CQI. 
     In the layer direction (spatial direction), the CSI reference resources are defined by the RI and the PMI whose conditions are set by the measured CQI. In other words, in the layer direction (spatial direction), the CSI reference resources are defined by the RI and the PMI which are assumed or generated when the CQI is measured. 
     In the time direction, the CSI reference resources are defined by one or more predetermined downlink sub frames. Specifically, the CSI reference resources are defined by a valid sub frame which is a predetermined number before a sub frame for reporting the CSI. The predetermined number of sub frames for defining the CSI reference resources is decided on the basis of the transmission mode, the frame configuration type, the number of CSI processes to be set, and/or the CSI report mode. For example, in a case in which one CSI process and the periodic CSI report mode are set in the terminal device  2 , the predetermined number of sub frames for defining the CSI reference resource is a minimum value of 4 or more among valid downlink sub frames. 
     A valid sub frame is a sub frame satisfying a predetermined condition. A downlink sub frame in a serving cell is considered to be valid in a case in which some or all of the following conditions are satisfied: 
     (1) A valid downlink sub frame is a sub frame in an ON state in the terminal device  2  in which the RRC parameters related to the ON state and the OFF state are set; 
     (2) A valid downlink sub frame is set as the downlink sub frame in the terminal device  2 ; 
     (3) A valid downlink sub frame is not a multimedia broadcast multicast service single frequency network (MBSFN) sub frame in a predetermined transmission mode; 
     (4) A valid downlink sub frame is not included in a range of a measurement interval (measurement gap) set in the terminal device  2 ; 
     (5) A valid downlink sub frame is an element or part of a CSI sub frame set linked to a periodic CSI report when the CSI sub frame set is set in the terminal device  2  in the periodic CSI report; and 
     (6) A valid downlink sub frame is an element or part of a CSI sub frame set linked to a downlink sub frame associated with a corresponding CSI request in an uplink DCI format in a non-periodic CSI report for the CSI process. Under these conditions, a predetermined transmission mode, a plurality of CSI processes, and a CSI sub frame set for the CSI process are set in the terminal device  2 . 
     Details of Multicarrier Transmission in Present Embodiment 
     A plurality of cells are set for the terminal device  2 , and the terminal device  2  can perform multicarrier transmission. Communication in which the terminal device  2  uses a plurality of cells is referred to as carrier aggregation (CA) or dual connectivity (DC). Contents described in the present embodiment can be applied to each or some of a plurality of cells set in the terminal device  2 . The cell set in the terminal device  2  is also referred to as a serving cell. 
     In the CA, a plurality of serving cells to be set includes one primary cell (PCell) and one or more secondary cells (SCell). One primary cell and one or more secondary cells can be set in the terminal device  2  that supports the CA. 
     The primary cell is a serving cell in which the initial connection establishment procedure is performed, a serving cell that the initial connection re-establishment procedure is started, or a cell indicated as the primary cell in a handover procedure. The primary cell operates with a primary frequency. The secondary cell can be set after a connection is constructed or reconstructed. The secondary cell operates with a secondary frequency. Further, the connection is also referred to as an RRC connection. 
     The DC is an operation in which a predetermined terminal device  2  consumes radio resources provided from at least two different network points. The network point is a master base station device (a master eNB (MeNB)) and a secondary base station device (a secondary eNB (SeNB)). In the dual connectivity, the terminal device  2  establishes an RRC connection through at least two network points. In the dual connectivity, the two network points may be connected through a non-ideal backhaul. 
     In the DC, the base station device  1  which is connected to at least an S1-MME and plays a role of a mobility anchor of a core network is referred to as a master base station device. Further, the base station device  1  which is not the master base station device providing additional radio resources to the terminal device  2  is referred to as a secondary base station device. A group of serving cells associated with the master base station device is also referred to as a master cell group (MCG). A group of serving cells associated with the secondary base station device is also referred to as a secondary cell group (SCG). 
     In the DC, the primary cell belongs to the MCG. Further, in the SCG, the secondary cell corresponding to the primary cell is referred to as a primary secondary cell (PSCell). A function (capability and performance) equivalent to the PCell (the base station device constituting the PCell) may be supported by the PSCell (the base station device constituting the PSCell). Further, the PSCell may only support some functions of the PCell. For example, the PSCell may support a function of performing the PDCCH transmission using the search space different from the CSS or the USS. Further, the PSCell may constantly be in an activation state. Further, the PSCell is a cell that can receive the PUCCH. 
     In the DC, a radio bearer (a date radio bearer (DRB)) and/or a signaling radio bearer (SRB) may be individually allocated through the MeNB and the SeNB. A duplex mode may be set individually in each of the MCG (PCell) and the SCG (PSCell). The MCG (PCell) and the SCG (PSCell) may not be synchronized with each other. A parameter (a timing advance group (TAG)) for adjusting a plurality of timings may be independently set in the MCG (PCell) and the SCG (PSCell). In the dual connectivity, the terminal device  2  transmits the UCI corresponding to the cell in the MCG only through MeNB (PCell) and transmits the UCI corresponding to the cell in the SCG only through SeNB (pSCell). In the transmission of each UCI, the transmission method using the PUCCH and/or the PUSCH is applied in each cell group. 
     The PUCCH and the PBCH (MIB) are transmitted only through the PCell or the PSCell. Further, the PRACH is transmitted only through the PCell or the PSCell as long as a plurality of TAGs are not set between cells in the CG. 
     In the PCell or the PSCell, semi-persistent scheduling (SPS) or discontinuous transmission (DRX) may be performed. In the secondary cell, the same DRX as the PCell or the PSCell in the same cell group may be performed. 
     In the secondary cell, information/parameter related to a setting of MAC is basically shared with the PCell or the PSCell in the same cell group. Some parameters may be set for each secondary cell. Some timers or counters may be applied only to the PCell or the PSCell. 
     In the CA, a cell to which the TDD scheme is applied and a cell to which the FDD scheme is applied may be aggregated. In a case in which the cell to which the TDD is applied and the cell to which the FDD is applied are aggregated, the present disclosure can be applied to either the cell to which the TDD is applied or the cell to which the FDD is applied. 
     The terminal device  2  transmits information indicating a combination of bands in which the CA is supported by the terminal device  2  to the base station device  1 . The terminal device  2  transmits information indicating whether or not simultaneous transmission and reception are supported in a plurality of serving cells in a plurality of different bands for each of band combinations to the base station device  1 . 
     Details of Resource Allocation in Present Embodiment 
     The base station device  1  can use a plurality of methods as a method of allocating resources of the PDSCH and/or the PUSCH to the terminal device  2 . The resource allocation method includes dynamic scheduling, semi persistent scheduling, multi sub frame scheduling, and cross sub frame scheduling. 
     In the dynamic scheduling, one DCI performs resource allocation in one sub frame. Specifically, the PDCCH or the EPDCCH in a certain sub frame performs scheduling for the PDSCH in the sub frame. The PDCCH or the EPDCCH in a certain sub frame performs scheduling for the PUSCH in a predetermined sub frame after the certain sub frame. 
     In the multi sub frame scheduling, one DCI allocates resources in one or more sub frames. Specifically, the PDCCH or the EPDCCH in a certain sub frame performs scheduling for the PDSCH in one or more sub frames which are a predetermined number after the certain sub frame. The PDCCH or the EPDCCH in a certain sub frame performs scheduling for the PUSCH in one or more sub frames which are a predetermined number after the sub frame. The predetermined number can be set to an integer of zero or more. The predetermined number may be specified in advance and may be decided on the basis of the signaling of the physical layer and/or the RRC signaling. In the multi sub frame scheduling, consecutive sub frames may be scheduled, or sub frames with a predetermined period may be scheduled. The number of sub frames to be scheduled may be specified in advance or may be decided on the basis of the signaling of the physical layer and/or the RRC signaling. 
     In the cross sub frame scheduling, one DCI allocates resources in one sub frame. Specifically, the PDCCH or the EPDCCH in a certain sub frame performs scheduling for the PDSCH in one sub frame which is a predetermined number after the certain sub frame. The PDCCH or the EPDCCH in a certain sub frame performs scheduling for the PUSCH in one sub frame which is a predetermined number after the sub frame. The predetermined number can be set to an integer of zero or more. The predetermined number may be specified in advance and may be decided on the basis of the signaling of the physical layer and/or the RRC signaling. In the cross sub frame scheduling, consecutive sub frames may be scheduled, or sub frames with a predetermined period may be scheduled. 
     In the semi-persistent scheduling (SPS), one DCI allocates resources in one or more sub frames. In a case in which information related to the SPS is set through the RRC signaling, and the PDCCH or the EPDCCH for activating the SPS is detected, the terminal device  2  activates a process related to the SPS and receives a predetermined PDSCH and/or PUSCH on the basis of a setting related to the SPS. In a case in which the PDCCH or the EPDCCH for releasing the SPS is detected when the SPS is activated, the terminal device  2  releases (inactivates) the SPS and stops reception of a predetermined PDSCH and/or PUSCH. The release of the SPS may be performed on the basis of a case in which a predetermined condition is satisfied. For example, in a case in which a predetermined number of empty transmission data is received, the SPS is released. The data empty transmission for releasing the SPS corresponds to a MAC protocol data unit (PDU) including a zero MAC service data unit (SDU). 
     Information related to the SPS by the RRC signaling includes an SPS C-RNTI which is an SPN RNTI, information related to a period (interval) in which the PDSCH is scheduled, information related to a period (interval) in which the PUSCH is scheduled, information related to a setting for releasing the SPS, and/or a number of the HARQ process in the SPS. The SPS is supported only in the primary cell and/or the primary secondary cell. 
     Details of Downlink Resource Element Mapping in Present Embodiment 
       FIG.  5    is a diagram illustrating an example of downlink resource element mapping in the present embodiment. In this example, a set of resource elements in one resource block pair in a case in which one resource block and the number of OFDM symbols in one slot are 7 will be described. Further, seven OFDM symbols in a first half in the time direction in the resource block pair are also referred to as a slot  0  (a first slot). Seven OFDM symbols in a second half in the time direction in the resource block pair are also referred to as a slot  1  (a second slot). Further, the OFDM symbols in each slot (resource block) are indicated by OFDM symbol number 0 to 6. Further, the sub carriers in the frequency direction in the resource block pair are indicated by sub carrier numbers 0 to 11. Further, in a case in which a system bandwidth is constituted by a plurality of resource blocks, a different sub carrier number is allocated over the system bandwidth. For example, in a case in which the system bandwidth is constituted by six resource blocks, the sub carriers to which the sub carrier numbers 0 to 71 are allocated are used. Further, in the description of the present embodiment, a resource element (k, l) is a resource element indicated by a sub carrier number k and an OFDM symbol number 1. 
     Resource elements indicated by R  0  to R  3  indicate cell-specific reference signals of the antenna ports  0  to  3 , respectively. Hereinafter, the cell-specific reference signals of the antenna ports  0  to  3  are also referred to as cell-specific RSs (CRSs). In this example, the case of the antenna ports in which the number of CRSs is 4 is described, but the number thereof can be changed. For example, the CRS can use one antenna port or two antenna ports. Further, the CRS can shift in the frequency direction on the basis of the cell ID. For example, the CRS can shift in the frequency direction on the basis of a remainder obtained by dividing the cell ID by 6. 
     Resource element indicated by C 1  to C 4  indicates reference signals (CSI-RS) for measuring transmission path states of the antenna ports  15  to  22 . The resource elements denoted by C 1  to C 4  indicate CSI-RSs of a code division multiplexing (CDM) group  1  to a CDM group  4 , respectively. The CSI-RS is constituted by an orthogonal sequence (orthogonal code) using a Walsh code and a scramble code using a pseudo random sequence. Further, the CSI-RS is code division multiplexed using an orthogonal code such as a Walsh code in the CDM group. Further, the CSI-RS is frequency-division multiplexed (FDM) mutually between the CDM groups. 
     The CSI-RSs of the antenna ports  15  and  16  are mapped to C 1 . The CSI-RSs of the antenna ports  17  and  18  is mapped to C 2 . The CSI-RSs of the antenna port  19  and  20  are mapped to C 3 . The CSI-RSs of the antenna port  21  and  22  are mapped to C 4 . 
     A plurality of antenna ports of the CSI-RSs are specified. The CSI-RS can be set as a reference signal corresponding to eight antenna ports of the antenna ports  15  to  22 . Further, the CSI-RS can be set as a reference signal corresponding to four antenna ports of the antenna ports  15  to  18 . Further, the CSI-RS can be set as a reference signal corresponding to two antenna ports of the antenna ports  15  to  16 . Further, the CSI-RS can be set as a reference signal corresponding to one antenna port of the antenna port  15 . The CSI-RS can be mapped to some sub frames, and, for example, the CSI-RS can be mapped for every two or more sub frames. A plurality of mapping patterns are specified for the resource element of the CSI-RS. Further, the base station device  1  can set a plurality of CSI-RSs in the terminal device  2 . 
     The CSI-RS can set transmission power to zero. The CSI-RS with zero transmission power is also referred to as a zero power CSI-RS. The zero power CSI-RS is set independently of the CSI-RS of the antenna ports  15  to  22 . Further, the CSI-RS of the antenna ports  15  to  22  is also referred to as a non-zero power CSI-RS. 
     The base station device  1  sets CSI-RS as control information specific to the terminal device  2  through the RRC signaling. In the terminal device  2 , the CSI-RS is set through the RRC signaling by the base station device  1 . Further, in the terminal device  2 , the CSI-IM resources which are resources for measuring interference power can be set. The terminal device  2  generates feedback information using the CRS, the CSI-RS, and/or the CSI-IM resources on the basis of a setting from the base station device  1 . 
     Resource elements indicated by D 1  to D 2  indicate the DL-DMRSs of the CDM group  1  and the CDM group  2 , respectively. The DL-DMRS is constituted using an orthogonal sequence (orthogonal code) using a Walsh code and a scramble sequence according to a pseudo random sequence. Further, the DL-DMRS is independent for each antenna port and can be multiplexed within each resource block pair. The DL-DMRSs are in an orthogonal relation with each other between the antenna ports in accordance with the CDM and/or the FDM. Each of DL-DMRSs undergoes the CDM in the CDM group in accordance with the orthogonal codes. The DL-DMRSs undergo the FDM with each other between the CDM groups. The DL-DMRSs in the same CDM group are mapped to the same resource element. For the DL-DMRSs in the same CDM group, different orthogonal sequences are used between the antenna ports, and the orthogonal sequences are in the orthogonal relation with each other. The DL-DMRS for the PDSCH can use some or all of the eight antenna ports (the antenna ports  7  to  14 ). In other words, the PDSCH associated with the DL-DMRS can perform MIMO transmission of up to 8 ranks. The DL-DMRS for the EPDCCH can use some or all of the four antenna ports (the antenna ports  107  to  110 ). Further, the DL-DMRS can change a spreading code length of the CDM or the number of resource elements to be mapped in accordance with the number of ranks of an associated channel. 
     The DL-DMRS for the PDSCH to be transmitted through the antenna ports  7 ,  8 ,  11 , and  13  are mapped to the resource element indicated by D 1 . The DL-DMRS for the PDSCH to be transmitted through the antenna ports  9 ,  10 ,  12 , and  14  are mapped to the resource element indicated by D 2 . Further, the DL-DMRS for the EPDCCH to be transmitted through the antenna ports  107  and  108  are mapped to the resource element indicated by D 1 . The DL-DMRS for the EPDCCH to be transmitted through the antenna ports  109  and  110  are mapped to the resource element denoted by D 2 . 
     HARQ in Present Embodiment 
     In the present embodiment, the HARQ has various features. The HARQ transmits and retransmits the transport block. In the HARQ, a predetermined number of processes (HARQ processes) are used (set), and each process independently operates in accordance with a stop-and-wait scheme. 
     In the downlink, the HARQ is asynchronous and operates adaptively. In other words, in the downlink, retransmission is constantly scheduled through the PDCCH. The uplink HARQ-ACK (response information) corresponding to the downlink transmission is transmitted through the PUCCH or the PUSCH. In the downlink, the PDCCH notifies of a HARQ process number indicating the HARQ process and information indicating whether or not transmission is initial transmission or retransmission. 
     In the uplink, the HARQ operates in a synchronous or asynchronous manner. The downlink HARQ-ACK (response information) corresponding to the uplink transmission is transmitted through the PHICH. In the uplink HARQ, an operation of the terminal device is decided on the basis of the HARQ feedback received by the terminal device and/or the PDCCH received by the terminal device. For example, in a case in which the PDCCH is not received, and the HARQ feedback is ACK, the terminal device does not perform transmission (retransmission) but holds data in a HARQ buffer. In this case, the PDCCH may be transmitted in order to resume the retransmission. Further, for example, in a case in which the PDCCH is not received, and the HARQ feedback is NACK, the terminal device performs retransmission non-adaptively through a predetermined uplink sub frame. Further, for example, in a case in which the PDCCH is received, the terminal device performs transmission or retransmission on the basis of contents notified through the PDCCH regardless of content of the HARQ feedback. 
     Further, in the uplink, in a case in which a predetermined condition (setting) is satisfied, the HARQ may be operated only in an asynchronous manner. In other words, the downlink HARQ-ACK is not transmitted, and the uplink retransmission may constantly be scheduled through the PDCCH. 
     In the HARQ-ACK report, the HARQ-ACK indicates ACK, NACK, or DTX. In a case in which the HARQ-ACK is ACK, it indicates that the transport block (codeword and channel) corresponding to the HARQ-ACK is correctly received (decoded). In a case in which the HARQ-ACK is NACK, it indicates that the transport block (codeword and channel) corresponding to the HARQ-ACK is not correctly received (decoded). In a case in which the HARQ-ACK is DTX, it indicates that the transport block (codeword and channel) corresponding to the HARQ-ACK is not present (not transmitted). 
     A predetermined number of HARQ processes are set (specified) in each of downlink and uplink. For example, in FDD, up to eight HARQ processes are used for each serving cell. Further, for example, in TDD, a maximum number of HARQ processes is decided by an uplink/downlink setting. A maximum number of HARQ processes may be decided on the basis of a round trip time (RTT). For example, in a case in which the RTT is 8 TTIs, the maximum number of the HARQ processes can be 8. 
     In the present embodiment, the HARQ information is constituted by at least a new data indicator (NDI) and a transport block size (TBS). The NDI is information indicating whether or not the transport block corresponding to the HARQ information is initial transmission or retransmission. The TBS is the size of the transport block. The transport block is a block of data in a transport channel (transport layer) and can be a unit for performing the HARQ. In the DL-SCH transmission, the HARQ information further includes a HARQ process ID (a HARQ process number). In the UL-SCH transmission, the HARQ information further includes an information bit in which the transport block is encoded and a redundancy version (RV) which is information specifying a parity bit. In the case of spatial multiplexing in the DL-SCH, the HARQ information thereof includes a set of NDI and TBS for each transport block. 
     TTI in Present Embodiment 
       FIG.  6    is a diagram illustrating an example of the TTI in the present embodiment. In the example of  FIG.  6   , the TTI is a 1 sub frame. In other words, a unit of data transmission in the time domain such as the PDSCH, the PUSCH, or the HARQ-ACK is a 1 sub frame. Arrows between downlink and uplink indicate a HARQ timing and/or a scheduling timing. The HARQ timing and the scheduling timing are specified or set in units of sub frames which are TTIs. For example, in a case in which a certain PDSCH is transmitted through a downlink sub frame n, the HARQ-ACK for the PDSCH is transmitted through an uplink sub frame n+4 after 4 sub frames. For example, in a case in which the PDCCH for notifying of the uplink grant is transmitted through a downlink sub frame n, the PUSCH corresponding to the uplink grant is transmitted through an uplink sub frame n+4 after 4 sub frames, and the HARQ-ACK for the PUSCH is notified through a downlink sub frame n+8 after 4 sub frames. Further, in  FIG.  6   , an example in which the TTI is a 1 sub frame is described, but the TTI may be a plurality of sub frames. In other words, the TTI may be an integer multiple of a sub frame length. 
       FIG.  7    is a diagram illustrating an example of the TTI in the present embodiment. In the example of  FIG.  7   , the TTI is a 1 symbol. In other words, a unit of data transmission in the time domain such as the PDSCH, the PUSCH, or the HARQ-ACK is a 1 symbol. Arrows between downlink and uplink indicate a HARQ timing and/or a scheduling timing. The HARQ timing and the scheduling timing are specified or set in units of symbols which are TTIs. For example, in a case in which a certain PDSCH is transmitted through a downlink symbol n, the HARQ-ACK for the PDSCH is transmitted through an uplink symbol n+4 after 4 symbols. For example, in a case in which the PDCCH for notifying of the uplink grant is transmitted through a downlink symbol n, the PUSCH corresponding to the uplink grant is transmitted through an uplink symbol n+4 after 4 symbols, and the HARQ-ACK for the PUSCH is notified through a downlink symbol n+8 after 4 symbols. Further, in  FIG.  6   , an example in which the TTI is a 1 symbol is described, but the TTI may be a plurality of symbols. In other words, the TTI may be an integer multiple of a symbol length. 
     A difference between  FIG.  6    and  FIG.  7    lies in that the TTIs have different sizes (lengths). Further, as described above, in a case in which the HARQ timing and the scheduling timing are specified or set on the basis of the TTI, the HARQ timing and the scheduling timing can be adjusted to earlier timings by reducing the TTI. Since the HARQ timing and the scheduling timing are factors for deciding the latency of the system, reducing the TTI reduces the latency. For example, the reduction in the latency is important for data (packet) intended for safety purpose such as intelligent transportation system. On the other hand, in a case in which the TTI is reduced, the maximum value of the TBS transmitted at one TTI is reduced, and an overhead of control information is likely to increase. Therefore, it is preferable that the TTI be specified or set in accordance with the purpose or the use of data. For example, the base station device can specify or set the size (length) and/or the mode of the TTI in a cell-specific manner or a terminal device specific manner. Further, in a case in which the HARQ timing and the scheduling timing are specified or set on the basis of the TTI, the maximum value of the TB S transmitted in the latency and/or one TTI can be adaptively set by changing the size (length) of the TTI. Accordingly, efficient data transmission in which the latency is considered can be performed. Further, in the description of the present embodiment, the sub frame, the symbol, the OFDM symbol, and the SC-FDMA symbol can be interpreted as the TTI. 
     Setting Related to TTI in Present Embodiment 
     In the present embodiment, sizes of a plurality of TTIs are specified. For example, a plurality of modes (TTI modes) related to the size of the TTI are specified, and the base station device sets the mode in the terminal device through the signaling of the higher layer. The base station device performs data transmission on the basis of the TTI mode set in the terminal device. The terminal device performs data transmission on the basis of the TTI mode set by the base station device. The setting of the TTI mode can be performed individually for each cell (serving cell). 
     A first TTI mode is a mode in which the TTI is based on the sub frame, and a second TTI mode is a mode in which the TTI is based on the symbol. For example, the TTI illustrated in  FIG.  6    is used in the first TTI mode, and the TTI illustrated in  FIG.  7    is used in the second TTI mode. Further, for example, in the first TTI mode, the TTI is an integer multiple of the sub frame length, and in the second TTI mode, the TTI is an integer multiple of the symbol length. Further, for example, in the first TTI mode, the TTI is specified through a 1 sub frame used in a system of a related art, and in the second TTI mode, the TTI is specified as an integer multiple of the symbol length which is not used in the system of the related art. Further, the TTI specified or set in the first TTI mode is also referred to as a first TTI, and the TTI specified or set in the second TTI mode is also referred to as a second TTI. 
     Various methods can be used for setting the TTI mode. In one example of the setting of the TTI mode, the first TTI mode or the second TTI mode is set in the terminal device through the signaling of the higher layer. In a case in which the first TTI mode is set, data transmission is performed on the basis of the first TTI. In a case in which the second TTI mode is set, data transmission is performed on the basis of the second TTI. In another example of the setting of the TTI mode, the second TTI mode (an extended TTI mode or a short TTI (STTI) mode) is set in the terminal device through the signaling of the higher layer. In a case in which the second TTI mode is not set, data transmission is performed on the basis of the first TTI. In a case in which the second TTI mode is set, data transmission is performed on the basis of the second TTI. Further, the second TTI is also referred to as an extended TTI or an STTI. 
     The setting related to the STTI (STTI setting) is performed through the RRC signaling and/or the signaling of the physical layer. The STTI setting includes information (parameter) related to the TTI size, a setting related to the STTI in the downlink (downlink STTI setting), a setting related to the STTI in the uplink (uplink STTI setting), and/or information for monitoring the control channel for notifying of the control information related to the STTI. The STTI setting can be individually set for each cell (serving cell). 
     The setting related to the STTI in the downlink is a setting for transmission (transmission and reception) of the downlink channel (the PDSCH, the PDCCH, and/or the EPDCCH) in the STTI mode, and includes a setting related to the downlink channel in the STTI mode. For example, the setting related to the STTI in the downlink includes a setting related to the PDSCH in the STTI mode, a setting related to the PDCCH in the STTI mode, and/or a setting related to the EPDCCH in the STTI mode. 
     The setting related to the STTI in the uplink is a setting for transmission (transmission and reception) of the uplink channel (the PUSCH and/or the PUCCH) in the STTI mode, and includes a setting related to the uplink channel in the STTI mode. For example, the setting related to the STTI in the uplink includes a setting related to the PUSCH in the STTI mode, and/or a setting related to the PUCCH in the STTI mode. 
     The information for monitoring the control channel for notifying of the control information related to the STTI is an RNTI used for scrambling the CRC added to the control information (DCI) related to the STTI. The RNTI is also referred to as an STTI-RNTI. Further, the STTI-RNTI may be set in common to the STTI in the downlink and the STTI in the uplink or may be set independently. Further, in a case in which a plurality of STTI settings are set, the STTI-RNTI may be set in common to all the STTI settings or may be independently set. 
     The information related to the TTI size is information indicating the size of the TTI in the STTI mode (that is, the size of the STTI). For example, the information related to the TTI size includes the number of OFDM symbols for setting the TTI in units of OFDM symbols. Further, in a case in which the information related to the TTI size is not included in the STTI setting, the TTI size can be se to a value which is specified in advance. For example, in a case in which the information related to the TTI size is not included in the STTI setting, the TTI size is a l symbol length or a l sub frame length. Further, the information related to the TTI size may be set in common to the STTI in the downlink and the STTI in the uplink or may be set independently. Further, in a case in which a plurality of STTI settings are set, the information related to the TTI size may be set in common to all the STTI settings or may be set independently. 
     In the description of the present embodiment, a channel (STTI channel) in the STTI mode includes a downlink channel in the STTI mode and/or an uplink channel in the STTI mode. A setting related to the channel in the STTI mode (STTI channel setting) includes a setting related to the downlink channel in the STTI mode and/or a setting related to the uplink channel in the STTI mode. The PDSCH in the STTI mode is also referred to as a short PDSCH (SPDSCH), an enhanced PDSCH (EPDSCH), or a reduced PDSCH (RPDSCH). The PUSCH in the STTI mode is also referred to as a short PUSCH (SPUSCH), an enhanced PUSCH (EPUSCH), or a reduced PUSCH (RPUSCH). The PUCCH in the STTI mode is also referred to as a short PUCCH (SPUCCH), an enhanced PUCCH (EPUCCH), or a reduced PUCCH (RPUCCH). The STTI channel includes the SPDSCH, the SPUSCH, or the SPUCCH. The STTI channel setting includes an SPDSCH setting, an SPUSCH setting, or an SPUCCH setting. 
     In the present embodiment, data transmission and scheduling methods for the channels in the STTI mode can use various methods or schemes. For example, the channel in the STTI mode is mapped to some or all of one or more periodic resources that are set or notified through the signaling of the higher layer and/or the signaling of the physical layer. 
     In the present embodiment, the physical downlink shared channel in the first TTI mode is also referred to as a PDSCH or a first PDSCH, and the physical downlink shared channel in the second TTI mode is also referred to as an SPDSCH or a second PDSCH. 
     The channel in the STTI mode is mapped on the basis of the sub resource block. The sub resource block is used to indicate mapping of a predetermined channel in the STTI mode to the resource element. One sub resource block is defined by successive sub carriers corresponding to one TTI in the time domain and consecutive sub carriers corresponding to one resource block in the frequency domain. A certain sub resource block may be configured to be included in only one resource block or may be configured over two resource blocks. Further, a certain sub resource block may be configured over two resource blocks in one resource block pair or may not be configured over a plurality of resource block pairs. 
     Each of the transport blocks (codeword) of the channel in the STTI mode is transmitted using one or more sub resource blocks in the same TTI. 
     Resources (sub resource block) to which the channel (the STTI channel) in the STTI mode can be mapped through signaling of the higher layer and/or signaling of the physical layer are set in the terminal device. The resources to which the channel in the STTI mode can be mapped is also referred to as an STTI channel candidate. Further, a series of STTI channel candidates set by one STTI channel setting is also referred to as a set of STTI channel candidates. 
     A set of the STTI channel candidates is designated by a TTI of a predetermined period in the time domain and a predetermined sub resource block in the frequency domain. In the same the STTI channel, a plurality of STTI channel settings can be performed. In other words, in each set of the STTI channel candidates, the period in the time domain and/or the resources in the frequency domain can be set independently. In a case in which a plurality of STTI channel settings are performed, the terminal device can monitor the set of a plurality of STTI channel candidates which is set. 
     The STTI channel setting includes STTI channel setting information in the time domain, STTI channel setting information in the frequency domain, and/or information related to the HARQ-ACK for the STTI channel. Further, the STTI channel setting may further include information for monitoring the control channel for notifying of the information related to the TTI size and/or the control information related to the STTI channel. The STTI channel setting information in the time domain is information for deciding the resources of the STTI channel candidate in the time domain. The STTI channel setting information in the frequency domain is information for deciding the resources of the STTI channel candidate in the frequency domain. 
     The information for deciding the resources of the STTI channel candidate can use various formats. The resources of the STTI channel in the frequency domain are decided (set, specified, or designated) in units of resource blocks or in units of sub resource blocks. 
     An example of the STTI channel setting information in the time domain includes a predetermined number of TTI periods and a predetermined number of TTI offsets. The offset of the TTI is an offset (shift) from a TTI serving as a reference and is set in units of TTIs. For example, in a case in which the offset of the TTI is 3, the set of the STTI channel candidates is set by including a TTI obtained by offsetting 3 TTIs from the TTI serving as the reference. For example, in a case in which the period of the TTI is 3, the set of the STTI channel candidate is set at intervals of every two TTIs. In a case in which the period of the TTI is 1, all consecutive TTIs are set. 
     In another example of the STTI channel setting information in the time domain, bitmap information indicating the TTI of the STTI channel candidate is used. For example, one bit in the bitmap information corresponds to a predetermined number of sub frames or each of TTIs in a predetermined number of radio frames. In a case in which a certain bit in the bitmap information is 1, it indicates that the TTI corresponding to the bit is a TTI including the STTI channel candidate. In a case in which a certain bit in the bitmap information is 0, it indicates that the TTI corresponding to the bit is not a TTI including the STTI channel candidate. Specifically, in a case in which the TTI size is one sub frame, the number of TTIs in five sub frames is 70. In this case, the bitmap information is 70-bit information. The bitmap information is applied from the TTI serving as the reference and repeatedly applied for each TTI corresponding to the bitmap information. 
     An example of the STTI channel setting information in the frequency domain uses bitmap information indicating sub resource blocks of the STTI channel candidate or a set of sub resource blocks. For example, one bit in the bitmap information corresponds to each of a predetermined number of sets of sub resource blocks. In a case in which a certain bit in the bitmap information is 1, it indicates that the sub resource block included in the set of sub resource blocks corresponding to the bit is a sub resource block including the STTI channel candidate. In a case in which a certain bit in the bitmap information is 0, it indicates that the sub resource block included in the set of sub resource blocks corresponding to the bit is not a sub resource block including the STTI channel candidate. 
     Another example of the STTI channel setting information in the frequency domain uses a sub resource block serving as a start and the number of consecutively allocated sub resource blocks. 
     The set of sub resource blocks is constituted by a predetermined number of consecutive sub resource blocks in the frequency domain. The predetermined number of sub resource blocks constituting the set of sub resource blocks may be decided on the basis of other parameters such as the system bandwidth or may be set through the RRC signaling. In the description of the present embodiment, the set of sub resource blocks simply includes the sub resource block as well. 
     The sub resource block set by the STTI channel setting information in the frequency domain may be identical in all the TTIs or may be switched (hopped) at intervals of every predetermined number of TTIs. For example, the sub resource block of the STTI channel candidate in a certain TTI is decided further using a number (an index or information) indicating the TTI, and the sub resource block of the STTI channel candidate is set differently for each TTI. Accordingly, the frequency diversity effect can be expected. 
     The information related to the HARQ-ACK for the STTI channel includes information related to resources for reporting the HARQ-ACK for the STTI channel. For example, in a case in which the STTI channel is the SPDSCH, information related to the HARQ-ACK for the STTI channel explicitly or implicitly indicates resources in the uplink channel for reporting the HARQ-ACK for the SPDSCH. 
     In a case in which a plurality of STTI channel settings are set for the same the STTI channel, all parameters in the STTI channel setting may be independently set, or some parameters may be set in common. For example, in a plurality of STTI channel settings, the STTI channel setting information in the time domain and the STTI channel setting information in the frequency domain are set independently. For example, in a plurality of STTI channel settings, the STTI channel setting information in the time domain is set in common, and the STTI channel setting information in the frequency domain is set independently. For example, in a plurality of STTI channel settings, the STTI channel setting information in the time domain is set independently, and the STTI channel setting information in the frequency domain is set in common. Further, only some pieces of information may be set in common, and the period of the TTI included in the STTI channel setting information in the time domain may be set in common. 
     Some pieces of information or some parameters set by the STTI setting in the present embodiment may be notified through signaling of the physical layer. For example, the STTI channel setting information in the frequency domain is notified through signaling of the physical layer. 
     In one example of an operation of the terminal device in the STTI mode, the terminal device operates only through signaling of the higher layer (the RRC signaling) only. In a case in which the STTI channel setting is set through signaling of the higher layer, the terminal device starts monitoring or receiving of the corresponding STTI channel. The terminal device stops monitoring or receiving of the corresponding STTI channel in a case in which the STTI channel setting being set is released through signaling of the higher layer. 
     In another example of the operation of the terminal device in the STTI mode, the terminal device operates through signaling of the higher layer (the RRC signaling) and signaling of the physical layer. In a case in which the STTI channel setting is set through signaling of the higher layer, and the information (DCI) for activating scheduling of the corresponding STTI channel is notified through signaling of the physical layer, the terminal device starts monitoring or receiving of the corresponding STTI channel. In a case in which the STTI channel setting is set through signaling of the higher layer, and information (DCI) for releasing scheduling of the corresponding STTI channel is notified through signaling of the physical layer, the terminal device stops monitoring or receiving of the corresponding STTI channel. 
     In a case in which a plurality of STTI channel settings are set, the information for enabling the scheduling of the STTI channel or the information for releasing the scheduling of the STTI channel may be notified in common to the STTI channels or independently. 
     In a case in which a plurality of STTI channel settings are set, and the STTI channel candidates which are set differently collide at the same TTI (that is, in a case in which a plurality of STTI channel candidates are set within the same TTI), the terminal device may monitor all of the STTI channel candidate or may monitor some of the STTI channel candidates. In a case in which some of the STTI channel candidates are monitored, the terminal device may decide the STTI channel candidate to be monitored on the basis of a predetermined priority. For example, the predetermined priority is decided on the basis of a type of STTI channel, an index (number) indicating the STTI channel setting, and/or an element (parameter) including a capability of the terminal device. 
     Details of SPDSCH in Present Embodiment 
       FIG.  8    is a diagram illustrating an example of a set of SPDSCH candidates. In the example of  FIG.  8   , a first set of SPDSCH candidates and a second set of SPDSCH candidates are set by the base station device of the terminal device. The TTI size is a 1 symbol. In the first set of SPDSCH candidates, the period of the TTI is 2, and the offset of the TTI is 0. Here, the TTI serving as the reference in the offset of the TTI is a first symbol  0  in  FIG.  8   . In the second set of SPDSCH candidates, the period of the TTI is 3, and the offset of the TTI is 1. The SPDSCH candidate is also referred to as a second PDSCH candidate. 
     The base station device maps the SPDSCH for the terminal device to one of the SPDSCH candidates set in the terminal device and transmits resulting data. The terminal device monitors the SPDSCH candidate set in the base station device and detects the SPDSCH for the terminal device. 
     An example of a method of deciding whether or not the SPDSCH detected in a certain terminal device is addressed to the terminal device, and reception is performed correctly is a method of using an RNTI specific to the terminal device (for example, the STTI-RNTI). For example, each codeword (transport block) to which a predetermined CRC is added is scrambled using the RNTI specific to the terminal device and transmitted. Therefore, in a case in which the terminal device receives the SPDSCH, since each codeword is descrambled correctly, the terminal device can determine that the SPDSCH is addressed to the terminal device on the basis of the added CRC. On the other hand, in a case in which a terminal device different from the terminal device receives the SPDSCH, since each codeword is not descrambled correctly, another the terminal device can determine that the SPDSCH is not addressed to itself on the basis of the added CRC. 
     Another example of a method of deciding whether or not the SPDSCH detected in a certain terminal device is addressed to the terminal device, and reception is performed correctly is a method of including information indicating that the SPDSCH for the certain terminal device is addressed to the terminal device. For example, the SPDSCH for a certain terminal device contains an RNTI specific to the terminal device. For example, the CRC in the SPDSCH for a certain terminal device is scrambled using an RNTI specific to the terminal device. 
     The terminal device performs an operates related to the report of the HARQ-ACK for the SPDSCH or the SPDSCH candidate on the basis of whether or not the SPDSCH addressed to the terminal device is correctly received (decode). 
     Here, in a case in which the SPDSCH candidate is not received (decoded) correctly in a certain terminal device, the SPDSCH candidate may be one of the following situations: 
     (1) the SPDSCH is an SPDSCH addressed to the terminal device but not received correctly; 
     (2) the SPDSCH is an SPDSCH addressed to a terminal device different from the terminal device; and 
     (3) none of SPDSCHs is transmitted to the PDSCH candidate. However, in a case in which the SPDSCH candidate is not received correctly, the terminal device may not be able to determine whether or not the SPDSCH corresponds to one of the above situations. Therefore, in a case in which the SPDSCH is not correctly received by the terminal device, it may be preferable that the same operation be performed regardless of the SPDSCH corresponds to one of the above situations. 
     Examples of an operation related to the HARQ-ACK report for the SPDSCH or the SPDSCH candidate in the terminal device are as follows: 
     (1) in a case in which the terminal device can correctly receive (decode) the SPDSCH addressed to the terminal device, the terminal device reports ACK as the HARQ-ACK report for the SPDSCH through predetermined resources. (2) in a case in which the terminal device fails to correctly receive (decode) the SPDSCH addressed to the terminal device, the terminal device reports NACK and/or DTX as the HARQ-ACK report for the SPDSCH through predetermined resources. 
       FIG.  9    is a diagram illustrating an example of SPDSCH transmission in the base station device and the HARQ-ACK report in the terminal device. The base station device sets a set of SPDSCH candidates by performing the STTI setting in the terminal device through the RRC signaling. The base station device notifies the terminal device of the information for activating the scheduling of the SPDSCH through the PDCCH. The base station device is likely to transmit the SPDSCH for the terminal device on the basis of the set of set SPDSCH candidates. On the other hand, the terminal device monitors the set of set SPDSCH candidates and detects the SPDSCH for the terminal device. 
     The base station device transmits the SPDSCH for the terminal device in SPDSCH candidates #1, #2, #3, and #5. Since the SPDSCHs in the SPDSCH candidates #1, #2, and #5 are correctly decoded, the terminal device reports the HARQ-ACK indicating ACK in the HARQ-ACK reports #1, #2, and #5. Since the SPDSCH in the SPDSCH candidate #3 is not correctly decoded, the terminal device reports the HARQ-ACK indicating NACK and/or DTX in the HARQ-ACK report #3. 
     The base station device transmits the SPDSCH for another the terminal device in SPDSCH candidates #4 and #6. Further, the base station device may not transmit anything in the SPDSCH candidates #4 and #6. Since the SPDSCHs in the SPDSCH candidates #4 and #6 are correctly decoded, the terminal device reports the HARQ-ACK indicating NACK and/or DTX in the HARQ-ACK reports #4 and #6. 
     The base station device notifies the terminal device of the information for releasing the scheduling of the SPDSCH through the PDCCH. The terminal device stops monitoring of the set of set SPDSCH candidates. 
     By using the above method, the control information for scheduling the SPDSCH need not be notified individually, and thus the overhead for the control information is reduced, and the latency is reduced. Further, the terminal device performs the HARQ-ACK for all the SPDSCH candidates, and thus even in a case in which the base station device does not transmit the SPDSCH for that the terminal device, it is possible to recognize that the terminal device is monitoring the SPDSCH candidates. 
     In the above-described method, in a case in which the same set of SPDSCH candidates is set in a plurality of terminal devices, the resources for performing the HARQ-ACK report are set differently between the terminal devices. Accordingly, the transmission efficiency for the SPDSCH can be improved, and the decrease in the transmission efficiency caused by collision of the HARQ-ACK report can be reduced. 
     Other examples of the operation related to the HARQ-ACK report for the SPDSCH or the SPDSCH candidate in the terminal device are as follows. (1) In a case in which the terminal device can correctly receive (decode) the SPDSCH addressed to the terminal device, the terminal device reports ACK as the HARQ-ACK report for the SPDSCH through predetermined resources. Information indicating that it is a report of the terminal device may be explicitly or implicitly included in the HARQ-ACK report indicating ACK. (2) In a case in which the terminal device does not correctly receive (decode) the SPDSCH addressed to the terminal device, the terminal device does not perform the HARQ-ACK report for the SPDSCH. In other words, the terminal device does not transmit anything through predetermined resources used for the HARQ-ACK report for the SPDSCH. 
       FIG.  10    is a diagram illustrating an example of SPDSCH transmission in the base station device and the HARQ-ACK report in the terminal device. The base station device sets a set of SPDSCH candidates by performing the STTI setting in the terminal device through the RRC signaling. The base station device notifies the terminal device of the information for activating the scheduling of the SPDSCH through the PDCCH. The base station device is likely to transmit the SPDSCH for the terminal device on the basis of the set of set SPDSCH candidates. On the other hand, the terminal device monitors the set of set SPDSCH candidates and detects the SPDSCH for the terminal device. 
     The base station device transmits the SPDSCH for the terminal device in SPDSCH candidates #1, #2, #3, and #5. Since the SPDSCHs in the SPDSCH candidates #1, #2, and #5 are correctly decoded, the terminal device reports the HARQ-ACK indicating ACK in the HARQ-ACK reports #1, #2, and #5. Since the SPDSCH in the SPDSCH candidate #3 is not correctly decoded, the terminal device does not report the HARQ-ACK in the HARQ-ACK report #3, and transmits nothing. 
     The base station device transmits the SPDSCH for another the terminal device in SPDSCH candidates #4 and #6. Further, the base station device may not transmit anything in the SPDSCH candidates #4 and #6. Since the SPDSCHs in the SPDSCH candidates #4 and #6 are correctly decoded, the terminal device does not report the HARQ-ACK in the HARQ-ACK reports #4 and #6, and transmits nothing. 
     The base station device notifies the terminal device of the information for releasing the scheduling of the SPDSCH through the PDCCH. The terminal device stops monitoring of the set of set SPDSCH candidate. 
       FIG.  11    is a diagram illustrating a flowchart of the terminal device in which the STTI setting is set. The flowchart of  FIG.  11    illustrates an operation of the terminal device in a case in which the method described in  FIG.  10    is used. In step S1, the terminal device monitors the PDCCH including the information for activating the scheduling of the SPDSCH. In a case in which the PDCCH for the activation is detected, the process proceeds to step S2. In a case in which the PDCCH for the activation is not detected, the process returns to step S1. In step S2, the terminal device monitors the PDCCH including the information for releasing the scheduling of the SPDSCH. In a case in which the PDCCH for the release is detected, the flow ends. In a case in which the PDCCH for the release is not detected, the process proceeds to step S3. In step S3, the terminal device monitors the SPDSCH candidate on the basis of the STTI setting in the higher layer. In step S4, the terminal device detects the SPDSCH addressed to the terminal device from the SPDSCH candidate. In a case in which the SPDSCH addressed to the terminal device is correctly decoded, the process proceeds to step S5. In a case in which the SPDSCH addressed to that the terminal device is not decoded correctly, the process returns to step S2. In step S5, the terminal device reports the HARQ-ACK indicating ACK for the correctly decoded SPDSCH. 
       FIG.  12    is a diagram illustrating an example of operations of the base station device and the terminal device in a case in which a setting related to the same SPDSCH is performed in a plurality of terminal devices. In the example of  FIG.  12   , the base station device and the terminal device use the method described in  FIG.  10   . In other words, the terminal device performs the operation of the flowchart described in  FIG.  11   . 
     At a timing #1 of the SPDSCH candidate, the base station device transmits the SPDSCH addressed to a terminal device A. Since the SPDSCH addressed to the terminal device A is correctly decoded, the terminal device A reports the HARQ-ACK indicating ACK for the SPDSCH. Since the terminal device B and the terminal device C do not decode the SPDSCH candidate correctly, the terminal device B and the terminal device C do not report the HARQ-ACK for the SPDSCH candidate. The base station device can recognize that the SPDSCH is correctly decoded on the basis of the HARQ-ACK report from the terminal device A. 
     At a timing #2 of the SPDSCH candidate, the base station device transmits the SPDSCH addressed to a terminal device C. Since the SPDSCH addressed to the terminal device C is correctly decoded, the terminal device C reports the HARQ-ACK indicating ACK for the SPDSCH. Since the terminal device A and the terminal device B do not decode the SPDSCH candidate correctly, the terminal device A and the terminal device B do not report the HARQ-ACK for the SPDSCH candidate. The base station device can recognize that the SPDSCH is correctly decoded on the basis of the HARQ-ACK report from the terminal device C. 
     At a timing #3 of the SPDSCH candidate, the base station device does not transmit anything. Since the terminal device A, the terminal device B, and the terminal device C do not decode the SPDSCH candidate correctly, the terminal device A, the terminal device B, and the terminal device C do not report the HARQ-ACK for the SPDSCH candidate. 
     At a timing #4 of the SPDSCH candidate, the base station device transmits the SPDSCH addressed to the terminal device B. Since the terminal device A, the terminal device B, and the terminal device C do not correctly decode the SPDSCH candidate, the terminal device A, the terminal device B, and the terminal device C do not report the HARQ-ACK for the SPDSCH candidate. Since the HARQ-ACK for the SPDSCH candidate is not reported, the base station device can recognize that the terminal device B does not correctly decode the SPDSCH. 
     By using the above method, the control information for scheduling the SPDSCH need not be notified individually, and thus the overhead for the control information is reduced, and the latency is reduced. Further, the terminal device performs the HARQ-ACK only in a case in which the SPDSCH candidate is correctly decoded, and thus a process and power consumption of the terminal device can be reduced. 
     In the above-described method, in a case in which the same set of SPDSCH candidates is set in a plurality of terminal devices, the resources for performing the HARQ-ACK report are set differently between the terminal devices. Accordingly, the transmission efficiency for the SPDSCH can be improved, the resources used for the HARQ-ACK report can be reduced, and the uplink transmission efficiency can be improved. 
     Resource Element Mapping of SPDSCH in Present Embodiment 
     As described above, the channel in the STTI mode is mapped on the basis of the sub resource block. In other words, the SPDSCH is mapped on the basis of the sub resource block. The resource element mapping of the SPDSCH described in the present embodiment is also applied to the candidate of the SPDSCH to be monitored. 
     In the present embodiment, in a case in which a predetermined channel or signal is not mapped to a predetermined resource element, a predetermined method can be used for the mapping. An example of the predetermined method is rate matching. In the rate matching, a predetermined channel or signal is mapped while skipping a predetermined resource element. It is necessary for the terminal device to recognize or assume that the rate matching is used for mapping to a predetermined resource element in reception (demodulation and decoding) of a predetermined channel or signal. Another example of the predetermined method is puncturing. In the puncturing, a predetermined channel or signal is assumed to be mapped without skipping a predetermined resource element, but another channel or signal is mapped to (overwritten in) the predetermined resource element. It is preferable that the terminal device recognize or assume that the puncturing is used for the mapping to a predetermined resource element in the reception (demodulation, decoding) of a predetermined channel or signal, but the terminal device may not perform the recognizing or the assuming. In this case, the reception accuracy deteriorates, but the terminal device can perform the reception by adjusting the coding rate or the like. In the description of the present embodiment, both the rate matching and the puncturing can be applied as the resource element mapping. 
     The SPDSCH is mapped to the resource element on the basis of various conditions, criteria, or scales. In other words, in each of the antenna ports used for the transmission of the SPDSCH, a block of a complex value symbol is mapped to a resource element satisfying a predetermined condition, criterion, or scale in the (current) TTI serving as the target. The predetermined condition, criteria, or scale is at least part of the following conditions, criteria, or scales. The conditions, criteria, or scales used for mapping the SPDSCH (second PDSCH) to the resource element are also referred to as a second condition, a second criterion, or a second criterion, respectively. The conditions, criteria, or scales used for mapping the PDSCH (first PDSCH) to the resource element are also referred to as a first condition, a first criterion, or a first measure, respectively. 
     (1) The resource element to which the SPDSCH is mapped is within the sub resource block allocated for transmission. Further, the resource element to which the PDSCH is mapped is within the resource block allocated for transmission. 
     (2) The resource element to which the SPDSCH is mapped is not used for transmission of the PBCH and the synchronization signal. Further, the resource element to which the PDSCH is mapped is not used for transmission of the PBCH and the synchronization signal. 
     (3) The resource element to which the SPDSCH is mapped is assumed not to be used for the CRS by the terminal device. Further, the resource element to which the PDSCH is mapped is assumed not to be used for the CRS by the terminal device. The CRS assumed by the terminal device may be different in the SPDSCH and the PDSCH. For example, the CRS assumed in the mapping of the SPDSCH is set independently of the CRS assumed in the mapping of the SPDSCH. 
     (4) In the sub resource block in which the DMRS associated with the SPDSCH is not transmitted, the SPDSCH is transmitted through an antenna port through which the CRS is transmitted or an antenna port through which the DMRS associated with the SPDSCH is transmitted. The DMRS associated with the SPDSCH can be a DMRS mapped in the resource block including the sub resource block to which the SPDSCH is mapped. Further, in the sub resource block in which the DMRS associated with the PDSCH is not transmitted, the PDSCH is transmitted through the antenna port to which the antenna port through which the CRS is transmitted is transmitted. The antenna port through which the SPDSCH is transmitted may be identical to as or different from the antenna port through which the PDSCH is transmitted. 
     (5) In the sub resource block to which the DMRS associated with the SPDSCH is transmitted, the SPDSCH is transmitted through the antenna port through which the CRS is transmitted or the antenna port through the DMRS associated with the SPDSCH is transmitted. The DMRS associated with the SPDSCH can be a DMRS mapped in the resource block including the sub resource block to which the DMRS and/or the SPDSCH are mapped. Further, in the sub resource block through which the DMRS associated with the PDSCH is transmitted, the PDSCH is transmitted through the antenna port through which the DMRS associated with the PDSCH is transmitted. The antenna port through which the SPDSCH is transmitted may be identical to or different from the antenna port through which the PDSCH is transmitted. In other words, the antenna port through which the DMRS associated with the SPDSCH is transmitted may be identical to or different from the antenna port through which the DMRS associated with the PDSCH is transmitted. 
     (6) In a case in which the SPDSCH is transmitted through an MBSFN sub frame, the SPDSCH is transmitted through the antenna port through which the DMRS associated with the SPDSCH is transmitted. The DMRS associated with the SPDSCH can be a DMRS mapped in the resource block including the sub resource block to which the SPDSCH is mapped. The MBSFN sub frame is set in a cell-specific manner or a terminal device-specific manner through the RRC signaling. Further, in a case in which the PDSCH is transmitted through the MBSFN sub frame, the PDSCH is transmitted through the antenna port through which the DMRS associated with the PDSCH is transmitted. The antenna port through which the SPDSCH is transmitted may be identical to or different from the antenna port through which the PDSCH is transmitted. In other words, the antenna port through which the DMRS associated with the SPDSCH is transmitted may be identical to or different from the antenna port through which the DMRS associated with the PDSCH is transmitted. 
     (7) The SPDSCH is not mapped to the resource elements used for the DMRS associated with the SPDSCH. Further, the PDSCH is not mapped to the resource element used for the DMRS associated with the PDSCH. The DMRS associated with the SPDSCH may be identical to or different from the DMRS associated with the PDSCH. Further, the SPDSCH may not be mapped to the resource element used for the DMRS further associated with the PDSCH. 
     (8) The SPDSCH is not mapped to resource elements used for the ZP CSI-RS and/or the NZP CSI-RS set in a cell-specific manner or a terminal device-specific manner. Further, the PDSCH is not mapped to the resource elements used for the ZP CSI-RS and/or the NZP CSI-RS set in a cell-specific manner or a terminal device-specific manner. The ZP CSI-RS and/or the NZP CSI-RS in the mapping of the SPDSCH may have the same setting as the ZP CSI-RS and/or the NZP CSI-RS in the mapping of the PDSCH. 
     (9) The SPDSCH is not mapped to the resource block pair, the sub resource block, the enhanced resource element group, or the resource element for transmitting the EPDCCH associated with the SPDSCH. For example, the SPDSCH is not mapped to the sub resource block including the resource element to which the EPDCCH associated with the SPDSCH is mapped. Further, the PDSCH is not mapped to the resource block pair for transmitting the EPDCCH associated with the PDSCH. 
     (10) The SPDSCH is mapped to a symbol after a symbol indicated by a predetermined index in a first slot in a certain sub frame in the sub frame (the start symbol of the SPDSCH). In other words, in a case in which the sub resource block to which the SPDSCH is to be mapped includes a symbol before the start symbol of the SPDSCH within a certain sub frame, the SPDSCH is not mapped to the symbol. The predetermined index indicating the start symbol of the SPDSCH is set in a cell-specific manner or a terminal device-specific manner. For example, the predetermined index indicating the start symbol of the SPDSCH is included in the downlink STTI setting and set. A minimum value of the predetermined index indicating the start symbol of the SPDSCH can be set to 0. Further, the start symbols of the SPDSCH may be specified in advance without being set and can be set to, for example, 0. In other words, the SPDSCH can be mapped to all symbols in a certain sub frame. 
     Further, the PDSCH is mapped to a symbol after a symbol indicated by a predetermined index in a first slot in a certain sub frame in the sub frame (the start symbol of the PDSCH). The predetermined index indicating the start symbol of the SPDSCH may be identical to or different from the predetermined index indicating the start symbol of the PDSCH. A minimum value of the predetermined index indicating the start symbol of the PDSCH is 1. 
     (11) The SPDSCH is not mapped to the resource elements of the resource element group allocated to the PCFICH or the PHICH. Further, the PDSCH is not mapped to a symbol including the resource element group allocated to the PCFICH or the PHICH (that is, a first symbol in a certain sub frame). In other words, the SPDSCH can be mapped to resource elements other than the resource element group in the symbol including the resource element group allocated to the PCFICH or the PHICH. For the resource element mapping of the SPDSCH, preferably, the rate matching is performed in the resource element used for the transmission of the PCFICH or the PHICH. 
     (12) The SPDSCH is not mapped to the resource block pair, the sub resource block, the symbol, the TTI, the resource element group, or the resource element for transmitting the PDCCH associated with the SPDSCH. In other words, the SPDSCH is not mapped to the resource block pair including the resource element or the resource element group, the sub resource block, the symbol, the TTI, or the resource element group for transmitting the PDCCH associated with the SPDSCH. 
     Further, the PDSCH is mapped regardless of the transmission of all the PDCCHs including the PDCCH associated with the PDSCH. For example, the PDCCH is transmitted through a symbol indicated by a CFI set or notified from the base station device, and the PDSCH is not mapped to the symbol used for transmitting the PDCCH. Therefore, in the mapping of the PDSCH, the terminal device may not necessarily recognize or assume the resource element used for transmitting the PDCCH. 
     On the other hand, in a case in which the SPDSCH is also mapped to the symbol including the resource element used for transmitting the PDCCH, it is preferable that the terminal device recognize or assume the resource element used for transmitting the PDCCH in the mapping of the PDSCH. In the resource element mapping of the SPDSCH, preferably, puncturing is performed on the resource element used for transmitting the PDCCH. Further, in the resource element mapping of the SPDSCH, the PDCCH includes not only the PDCCH associated with the SPDSCH but also some or all PDCCHs that the terminal device can recognize or receive. 
     (13-1) The SPDSCH is not mapped to the resource block, the resource block pair, or the resource block group used for the transmission of the PDSCH scheduled to (recognized or received by) the terminal device. For example, in a case in which a certain PDSCH is scheduled to a certain terminal device, the terminal device assumes that the SPDSCH is not mapped to the resource block used for transmission of the PDSCH or the sub resource block in the resource block group. Further, in this case, the SPDSCH may be mapped to the symbol (PDCCH region) before the start symbol of the PDSCH in the resource block or the resource block group. 
     In a case in which the SPDSCH is not mapped to the resource block, the resource block pair, or the resource block group used for transmission of the PDSCH scheduled to the terminal device, the PDSCH can be mapped regardless of the mapping of the SPDSCH. In other words, in a case in which the PDSCH is scheduled to resources including a certain resource block, the SPDSCH including the sub resource block in the resource block is not mapped. In other words, the terminal device assumes that the SPDSCH using the sub resource block in the resource block used for transmission of the PDSCH scheduled to the terminal device is not mapped (transmitted). The terminal device may not monitor the candidates of the SPDSCH. 
     In other words, in a case in which the candidate of the SPDSCH and the PDSCH to be scheduled collide in the same resource element, the resource block, or the sub resource block, the PDSCH is preferentially mapped, and the SPDSCH is not mapped. 
     (13-2) The SPDSCH is mapped regardless of transmission of the PDSCH scheduled to (recognized or received by) the terminal device. For example, even in a case in which a certain PDSCH is scheduled to a certain terminal device, the terminal device assumes that the SPDSCH can be mapped to the resource block used for transmission of the PDSCH or the sub resource block in the resource block group. In other words, the terminal device monitors the candidate of the SPDSCH to be set regardless of the scheduling of the PDSCH. 
     In a case in which the SPDSCH is mapped regardless of the transmission of the PDSCH scheduled to the terminal device, the mapping of the PDSCH depends on the SPDSCH. For example, the PDSCH is not mapped to the resource elements corresponding to the candidates of all the SPDSCHs. For example, the PDSCH is not mapped to the resource element corresponding to the SPDSCH which is detected among the candidates of the SPDSCH. In other words, the PDSCH is also mapped to the resource elements corresponding to the SPDSCHs which is not detected among the candidates of the SPDSCH. 
     Further, the PDSCH may not be scheduled in the resource blocks or the sub frames including the sub resource blocks used for transmission of the SPDSCH. For example, the terminal device assumes that the PDSCH is not scheduled in the resource block or the sub frame including the sub resource block corresponding to the candidate of the SPDSCH. 
     In other words, in a case in which the candidate of the SPDSCH and the PDSCH to be scheduled collide in the same resource element, the resource block, or the sub resource block, the SPDSCH is preferentially mapped, and the PDSCH is mapped to the resource element other than the resource element to which the SPDSCH is mapped. 
     (13-3) The resource element mappings described in (13-1) and (13-2) are switched on the basis of a predetermined condition and used. For example, in a case in which the PDSCH is scheduled through the EPDCCH, the resource element mapping described in (13-1) is used, and in a case in which the PDSCH is scheduled through the PDCCH, the resource element mapping described in (13-2) is used. For example, in a case in which the PDSCH is scheduled through the EPDCCH, the resource element mapping described in (13-2) is used, and in a case in which the PDSCH is scheduled through the PDCCH, the resource element mapping described in (13-1) is used. 
       FIG.  13    is a diagram illustrating an example of the resource element mapping of the SPDSCH.  FIG.  13    illustrates resource elements of two resource block pairs in the downlink. Resource elements R 0  to R 3  are resource elements to which the CRS is mapped respectively. Resource elements C 1  to C 4  are resource elements to which the CSI-RS is mapped. A resource element CFI is a resource element to which the PCFICH is mapped. A resource element HI is a resource element to which the PHICH is mapped. 
     In the example of  FIG.  13   , the TTI is a 1 symbol. In other words, one sub resource block is constituted by one symbol and 12 resource elements indicated by 12 sub carriers. The terminal device receives or monitors the SPDSCH mapped to a set of sub resource blocks (resource blocks  0  and  1 ) in a symbol  0  of a slot  0 , a symbol  5  of the slot  0 , and a symbol  3  of a slot  1  on the basis of a predetermined setting. The SPDSCH in the symbol  0  of the slot  0  is mapped to the resource elements other than the resource elements used for transmission of the CRS, the PCFICH, and the PHICH. The SPDSCH in the symbol  5  of the slot  0  is mapped to all the resource elements. The SPDSCH in the symbol  3  of the slot  1  is mapped to a resource element other than the resource element used for transmission of the CSI-RS. 
     The SPDSCH may be further mapped after the start symbol of the SPDSCH in a certain sub frame. For example, in a case in which the start symbol of the SPDSCH is 3, the SPDSCH can be mapped from the symbol  3  of the slot  0  to the symbol  6  of the slot  1 . In the example of  FIG.  13   , the terminal device does not assume transmission or mapping of the SPDSCH in the symbol  0  of the slot  0 . Therefore, the terminal device may not receive or monitor the SPDSCH in the symbol  0  of the slot  0 . 
     Details of PDSCH and SPDSCH in Present Embodiment 
     For example, in a case in which the SPDSCH setting is performed in a certain serving cell, the terminal device performs a process for the SPDSCH in the serving cell. Further, in a case in which the SPDSCH setting is not performed in a certain serving cell, the terminal device performs a process for the PDSCH in the serving cell. Hereinafter, an example of a difference between the PDSCH and the SPDSCH will be described. 
     An example of the difference between the PDSCH and the SPDSCH is the TTI size. 
     The PDSCH is the downlink shared channel in the first TTI mode and transmitted on the basis of the TTI specified by one sub frame used in the system of the related art. 
     The SPDSCH is the downlink shared channel in the second TTI mode (STTI mode) and transmitted on the basis of a TTI specified or set by an integer multiple of the symbol length which is not used in the system of the related art. 
     An example of the difference between PDSCH and SPDSCH is the scheduling method. 
     The PDSCH can be scheduled through the DCI notified through the PDCCH detected in the same TTI. Specifically, the TTI to which the PDSCH is mapped is a TTI in which the corresponding PDCCH is detected. The resource block in the frequency domain to which the PDSCH is mapped is scheduled through the DCI. In other words, the PDCCH for scheduling a certain PDSCH schedules only the PDSCH. 
     The SPDSCH may not be scheduled through the DCI notified through the control channel or the PDCCH detected in the same TTI. The TTI to which the SPDSCH can be mapped is a predetermined TTI set through the RRC signaling. The sub resource block in the frequency domain to which the SPDSCH can be mapped may be set and/or notified through the DCI for activating the scheduling of the RRC signaling and/or the SPDSCH. In other words, the SPDSCH is scheduled using one or more SPDSCH candidates set through the DCI for activating the RRC signaling and the scheduling of the SPDSCH. 
     An example of the difference between PDSCH and SPDSCH is the reception process of the terminal device. 
     In the first TTI mode, the PDSCH received by a certain terminal device is the PDSCH for the terminal device. Therefore, the terminal device performs the HARQ-ACK report for the PDSCH scheduled for the terminal device regardless of a result of decoding the PDSCH. 
     In the second TTI mode, the SPDSCH (SPDSCH candidate) received by a certain terminal device is unlikely to be the PDSCH for the terminal device. Therefore, the terminal device performs the HARQ-ACK report for the PDSCH scheduled for the terminal device on the basis of a result of decoding the PDSCH. For example, in a case in which the result of decoding the PDSCH is ACK, the terminal device reports the HARQ-ACK report for the PDSCH scheduled for the terminal device. In a case in which the result of decoding the PDSCH is NACK, the terminal device does not report the HARQ-ACK report for the PDSCH scheduled for the terminal device. 
     According to the details of the above embodiment, it is possible to improve the transmission efficiency in the wireless communication system in which the base station device  1  and the terminal device  2  communicate with each other. 
     APPLICATION EXAMPLES 
     Application Examples for Base Station 
     First Application Example 
       FIG.  14    is a block diagram illustrating a first example of a schematic configuration of an eNB to which the technology according to the present disclosure may be applied. An eNB  800  includes one or more antennas  810  and a base station apparatus  820 . Each antenna  810  and the base station apparatus  820  may be connected to each other via an RF cable. 
     Each of the antennas  810  includes a single or a plurality of antenna elements (e.g., a plurality of antenna elements constituting a MIMO antenna) and is used for the base station apparatus  820  to transmit and receive a wireless signal. The eNB  800  may include the plurality of the antennas  810  as illustrated in  FIG.  14   , and the plurality of antennas  810  may, for example, correspond to a plurality of frequency bands used by the eNB  800 . It should be noted that while  FIG.  14    illustrates an example in which the eNB  800  includes the plurality of antennas  810 , the eNB  800  may include the single antenna  810 . 
     The base station apparatus  820  includes a controller  821 , a memory  822 , a network interface  823 , and a wireless communication interface  825 . 
     The controller  821  may be, for example, a CPU or a DSP, and operates various functions of an upper layer of the base station apparatus  820 . For example, the controller  821  generates a data packet from data in a signal processed by the wireless communication interface  825 , and transfers the generated packet via the network interface  823 . The controller  821  may generate a bundled packet by bundling data from a plurality of base band processors to transfer the generated bundled packet. Further, the controller  821  may also have a logical function of performing control such as radio resource control, radio bearer control, mobility management, admission control, and scheduling. Further, the control may be performed in cooperation with a surrounding eNB or a core network node. The memory  822  includes a RAM and a ROM, and stores a program executed by the controller  821  and a variety of control data (such as, for example, terminal list, transmission power data, and scheduling data). 
     The network interface  823  is a communication interface for connecting the base station apparatus  820  to the core network  824 . The controller  821  may communicate with a core network node or another eNB via the network interface  823 . In this case, the eNB  800  may be connected to a core network node or another eNB through a logical interface (e.g., S1 interface or X2 interface). The network interface  823  may be a wired communication interface or a wireless communication interface for wireless backhaul. In the case where the network interface  823  is a wireless communication interface, the network interface  823  may use a higher frequency band for wireless communication than a frequency band used by the wireless communication interface  825 . 
     The wireless communication interface  825  supports a cellular communication system such as long term evolution (LTE) or LTE-Advanced, and provides wireless connection to a terminal located within the cell of the eNB  800  via the antenna  810 . The wireless communication interface  825  may typically include a base band (BB) processor  826 , an RF circuit  827 , and the like. The BB processor  826  may, for example, perform encoding/decoding, modulation/demodulation, multiplexing/demultiplexing, and the like, and performs a variety of signal processing on each layer (e.g., L1, medium access control (MAC), radio link control (RLC), and packet data convergence protocol (PDCP)). The BB processor  826  may have part or all of the logical functions as described above instead of the controller  821 . The BB processor  826  may be a module including a memory having a communication control program stored therein, a processor to execute the program, and a related circuit, and the function of the BB processor  826  may be changeable by updating the program. Further, the module may be a card or blade to be inserted into a slot of the base station apparatus  820 , or a chip mounted on the card or the blade. Meanwhile, the RF circuit  827  may include a mixer, a filter, an amplifier, and the like, and transmits and receives a wireless signal via the antenna  810 . 
     The wireless communication interface  825  may include a plurality of the BB processors  826  as illustrated in  FIG.  14   , and the plurality of BB processors  826  may, for example, correspond to a plurality of frequency bands used by the eNB  800 . Further, the wireless communication interface  825  may also include a plurality of the RF circuits  827 , as illustrated in  FIG.  14   , and the plurality of RF circuits  827  may, for example, correspond to a plurality of antenna elements. Note that  FIG.  14    illustrates an example in which the wireless communication interface  825  includes the plurality of BB processors  826  and the plurality of RF circuits  827 , but the wireless communication interface  825  may include the single BB processor  826  or the single RF circuit  827 . 
     Second Application Example 
       FIG.  15    is a block diagram illustrating a second example of a schematic configuration of an eNB to which the technology according to the present disclosure may be applied. An eNB  830  includes one or more antennas  840 , a base station apparatus  850 , and an RRH  860 . Each of the antennas  840  and the RRH  860  may be connected to each other via an RF cable. Further, the base station apparatus  850  and the RRH  860  may be connected to each other by a high speed line such as optical fiber cables. 
     Each of the antennas  840  includes a single or a plurality of antenna elements (e.g., antenna elements constituting a MIMO antenna), and is used for the RRH  860  to transmit and receive a wireless signal. The eNB  830  may include a plurality of the antennas  840  as illustrated in  FIG.  15   , and the plurality of antennas  840  may, for example, correspond to a plurality of frequency bands used by the eNB  830 . Note that  FIG.  15    illustrates an example in which the eNB  830  includes the plurality of antennas  840 , but the eNB  830  may include the single antenna  840 . 
     The base station apparatus  850  includes a controller  851 , a memory  852 , a network interface  853 , a wireless communication interface  855 , and a connection interface  857 . The controller  851 , the memory  852 , and the network interface  853  are similar to the controller  821 , the memory  822 , and the network interface  823  described with reference to  FIG.  14   . 
     The wireless communication interface  855  supports a cellular communication system such as LTE and LTE-Advanced, and provides wireless connection to a terminal located in a sector corresponding to the RRH  860  via the RRH  860  and the antenna  840 . The wireless communication interface  855  may typically include a BB processor  856  or the like. The BB processor  856  is similar to the BB processor  826  described with reference to  FIG.  14    except that the BB processor  856  is connected to an RF circuit  864  of the RRH  860  via the connection interface  857 . The wireless communication interface  855  may include a plurality of the BB processors  856 , as illustrated in  FIG.  15   , and the plurality of BB processors  856  may, for example, correspond to a plurality of frequency bands used by the eNB  830 . Note that  FIG.  15    illustrates an example in which the wireless communication interface  855  includes the plurality of BB processors  856 , but the wireless communication interface  855  may include the single BB processor  856 . 
     The connection interface  857  is an interface for connecting the base station apparatus  850  (wireless communication interface  855 ) to the RRH  860 . The connection interface  857  may be a communication module for communication on the high speed line which connects the base station apparatus  850  (wireless communication interface  855 ) to the RRH  860 . 
     Further, the RRH  860  includes a connection interface  861  and a wireless communication interface  863 . 
     The connection interface  861  is an interface for connecting the RRH  860  (wireless communication interface  863 ) to the base station apparatus  850 . The connection interface  861  may be a communication module for communication on the high speed line. 
     The wireless communication interface  863  transmits and receives a wireless signal via the antenna  840 . The wireless communication interface  863  may typically include the RF circuit  864  or the like. The RF circuit  864  may include a mixer, a filter, an amplifier and the like, and transmits and receives a wireless signal via the antenna  840 . The wireless communication interface  863  may include a plurality of the RF circuits  864  as illustrated in  FIG.  15   , and the plurality of RF circuits  864  may, for example, correspond to a plurality of antenna elements. Note that  FIG.  15    illustrates an example in which the wireless communication interface  863  includes the plurality of RF circuits  864 , but the wireless communication interface  863  may include the single RF circuit  864 . 
     The eNB  800 , the eNB  830 , the base station device  820 , or the base station device  850  illustrated in  FIGS.  14  and  15    may correspond to the base station device  1  described above with reference to  FIG.  3    and the like. 
     Application Examples for Terminal Apparatus 
     First Application Example 
       FIG.  16    is a block diagram illustrating an example of a schematic configuration of a smartphone  900  as the terminal apparatus  2  to which the technology according to the present disclosure may be applied. The smartphone  900  includes a processor  901 , a memory  902 , a storage  903 , an external connection interface  904 , a camera  906 , a sensor  907 , a microphone  908 , an input device  909 , a display device  910 , a speaker  911 , a wireless communication interface  912 , one or more antenna switches  915 , one or more antennas  916 , a bus  917 , a battery  918 , and an auxiliary controller  919 . 
     The processor  901  may be, for example, a CPU or a system on chip (SoC), and controls the functions of an application layer and other layers of the smartphone  900 . The memory  902  includes a RAM and a ROM, and stores a program executed by the processor  901  and data. The storage  903  may include a storage medium such as semiconductor memories and hard disks. The external connection interface  904  is an interface for connecting the smartphone  900  to an externally attached device such as memory cards and universal serial bus (USB) devices. 
     The camera  906  includes, for example, an image sensor such as charge coupled devices (CCDs) and complementary metal oxide semiconductor (CMOS), and generates a captured image. The sensor  907  may include a sensor group including, for example, a positioning sensor, a gyro sensor, a geomagnetic sensor, an acceleration sensor and the like. The microphone  908  converts a sound that is input into the smartphone  900  to an audio signal. The input device  909  includes, for example, a touch sensor which detects that a screen of the display device  910  is touched, a key pad, a keyboard, a button, a switch or the like, and accepts an operation or an information input from a user. The display device  910  includes a screen such as liquid crystal displays (LCDs) and organic light emitting diode (OLED) displays, and displays an output image of the smartphone  900 . The speaker  911  converts the audio signal that is output from the smartphone  900  to a sound. 
     The wireless communication interface  912  supports a cellular communication system such as LTE or LTE-Advanced, and performs wireless communication. The wireless communication interface  912  may typically include the BB processor  913 , the RF circuit  914 , and the like. The BB processor  913  may, for example, perform encoding/decoding, modulation/demodulation, multiplexing/demultiplexing, and the like, and performs a variety of types of signal processing for wireless communication. On the other hand, the RF circuit  914  may include a mixer, a filter, an amplifier, and the like, and transmits and receives a wireless signal via the antenna  916 . The wireless communication interface  912  may be a one-chip module in which the BB processor  913  and the RF circuit  914  are integrated. The wireless communication interface  912  may include a plurality of BB processors  913  and a plurality of RF circuits  914  as illustrated in  FIG.  16   . Note that  FIG.  16    illustrates an example in which the wireless communication interface  912  includes a plurality of BB processors  913  and a plurality of RF circuits  914 , but the wireless communication interface  912  may include a single BB processor  913  or a single RF circuit  914 . 
     Further, the wireless communication interface  912  may support other types of wireless communication system such as a short range wireless communication system, a near field communication system, and a wireless local area network (LAN) system in addition to the cellular communication system, and in this case, the wireless communication interface  912  may include the BB processor  913  and the RF circuit  914  for each wireless communication system. 
     Each antenna switch  915  switches a connection destination of the antenna  916  among a plurality of circuits (for example, circuits for different wireless communication systems) included in the wireless communication interface  912 . 
     Each of the antennas  916  includes one or more antenna elements (for example, a plurality of antenna elements constituting a MIMO antenna) and is used for transmission and reception of the wireless signal by the wireless communication interface  912 . The smartphone  900  may include a plurality of antennas  916  as illustrated in  FIG.  16   . Note that  FIG.  16    illustrates an example in which the smartphone  900  includes a plurality of antennas  916 , but the smartphone  900  may include a single antenna  916 . 
     Further, the smartphone  900  may include the antenna  916  for each wireless communication system. In this case, the antenna switch  915  may be omitted from a configuration of the smartphone  900 . 
     The bus  917  connects the processor  901 , the memory  902 , the storage  903 , the external connection interface  904 , the camera  906 , the sensor  907 , the microphone  908 , the input device  909 , the display device  910 , the speaker  911 , the wireless communication interface  912 , and the auxiliary controller  919  to each other. The battery  918  supplies electric power to each block of the smartphone  900  illustrated in  FIG.  16    via a feeder line that is partially illustrated in the figure as a dashed line. The auxiliary controller  919 , for example, operates a minimally necessary function of the smartphone  900  in a sleep mode. 
     Second Application Example 
       FIG.  17    is a block diagram illustrating an example of a schematic configuration of a car navigation apparatus  920  to which the technology according to the present disclosure may be applied. The car navigation apparatus  920  includes a processor  921 , a memory  922 , a global positioning system (GPS) module  924 , a sensor  925 , a data interface  926 , a content player  927 , a storage medium interface  928 , an input device  929 , a display device  930 , a speaker  931 , a wireless communication interface  933 , one or more antenna switches  936 , one or more antennas  937 , and a battery  938 . 
     The processor  921  may be, for example, a CPU or an SoC, and controls the navigation function and the other functions of the car navigation apparatus  920 . The memory  922  includes a RAM and a ROM, and stores a program executed by the processor  921  and data. 
     The GPS module  924  uses a GPS signal received from a GPS satellite to measure the position (e.g., latitude, longitude, and altitude) of the car navigation apparatus  920 . The sensor  925  may include a sensor group including, for example, a gyro sensor, a geomagnetic sensor, a barometric sensor and the like. The data interface  926  is, for example, connected to an in-vehicle network  941  via a terminal that is not illustrated, and acquires data such as vehicle speed data generated on the vehicle side. 
     The content player  927  reproduces content stored in a storage medium (e.g., CD or DVD) inserted into the storage medium interface  928 . The input device  929  includes, for example, a touch sensor which detects that a screen of the display device  930  is touched, a button, a switch or the like, and accepts operation or information input from a user. The display device  930  includes a screen such as LCDs and OLED displays, and displays an image of the navigation function or the reproduced content. The speaker  931  outputs a sound of the navigation function or the reproduced content. 
     The wireless communication interface  933  supports a cellular communication system such as LTE or LTE-Advanced, and performs wireless communication. The wireless communication interface  933  may typically include the BB processor  934 , the RF circuit  935 , and the like. The BB processor  934  may, for example, perform encoding/decoding, modulation/demodulation, multiplexing/demultiplexing, and the like, and performs a variety of types of signal processing for wireless communication. On the other hand, the RF circuit  935  may include a mixer, a filter, an amplifier, and the like, and transmits and receives a wireless signal via the antenna  937 . The wireless communication interface  933  may be a one-chip module in which the BB processor  934  and the RF circuit  935  are integrated. The wireless communication interface  933  may include a plurality of BB processors  934  and a plurality of RF circuits  935  as illustrated in  FIG.  17   . Note that  FIG.  17    illustrates an example in which the wireless communication interface  933  includes a plurality of BB processors  934  and a plurality of RF circuits  935 , but the wireless communication interface  933  may include a single BB processor  934  or a single RF circuit  935 . 
     Further, the wireless communication interface  933  may support other types of wireless communication system such as a short range wireless communication system, a near field communication system, and a wireless LAN system in addition to the cellular communication system, and in this case, the wireless communication interface  933  may include the BB processor  934  and the RF circuit  935  for each wireless communication system. 
     Each antenna switch  936  switches a connection destination of the antenna  937  among a plurality of circuits (for example, circuits for different wireless communication systems) included in the wireless communication interface  933 . 
     Each of the antennas  937  includes one or more antenna elements (for example, a plurality of antenna elements constituting a MIMO antenna) and is used for transmission and reception of the wireless signal by the wireless communication interface  933 . The car navigation apparatus  920  may include a plurality of antennas  937  as illustrated in  FIG.  17   . Note that  FIG.  17    illustrates an example in which the car navigation apparatus  920  includes a plurality of antennas  937 , but the car navigation apparatus  920  may include a single antenna  937 . 
     Further, the car navigation apparatus  920  may include the antenna  937  for each wireless communication system. In this case, the antenna switch  936  may be omitted from a configuration of the car navigation apparatus  920 . 
     The battery  938  supplies electric power to each block of the car navigation apparatus  920  illustrated in  FIG.  17    via a feeder line that is partially illustrated in the figure as a dashed line. Further, the battery  938  accumulates the electric power supplied from the vehicle. 
     The technology of the present disclosure may also be realized as an in-vehicle system (or a vehicle)  940  including one or more blocks of the car navigation apparatus  920 , the in-vehicle network  941 , and a vehicle module  942 . The vehicle module  942  generates vehicle data such as vehicle speed, engine speed, and trouble information, and outputs the generated data to the in-vehicle network  941 . 
     Further, the effects described in this specification are merely illustrative or exemplified effects, and are not limitative. That is, with or in the place of the above effects, the technology according to the present disclosure may achieve other effects that are clear to those skilled in the art from the description of this specification. 
     Additionally, the present technology may also be configured as below. 
     (1) 
     A terminal device that communicates with a base station device, including: 
     a higher layer processing unit configured to set an STTI channel setting through signaling of a higher layer from the base station device; and 
     a receiving unit configured to receive a first PDSCH in a case in which the STTI channel setting is not set and receive a second PDSCH in a case in which the STTI channel setting is set, 
     in which the first PDCCH is mapped to one or more resource blocks, and 
     the second PDCCH is mapped to one or more sub resource blocks defined in accordance with a smaller number of symbols than a number of symbols corresponding to a resource block. 
     (2) 
     The terminal device according to (1), 
     in which the first PDSCH is mapped to a resource element other than resources designated by a PCFICH, and 
     the second PDSCH is mapped to a resource element including the resources designated by the PCFICH. 
     (3) 
     The terminal device according to (1) or (2), in which the second PDSCH is not mapped to a resource element used for transmission of the PCFICH. 
     (4) 
     The terminal device according to (1), in which, in a case in which the first PDSCH is allocated to a predetermined resource block, the second PDSCH is not mapped to a sub resource block included in the predetermined resource block. 
     (5) 
     The terminal device according to (1) or (4), in which, in a case in which the first PDSCH is allocated to a predetermined resource block and the second PDSCH is mapped to a sub resource block included in the predetermined resource block, the first PDSCH is not mapped to the sub resource block to which the second PDSCH is mapped. 
     (6) 
     The terminal device according to (1), in which the second PDSCH is mapped to any one of one or more second PDSCH candidates set on a basis of the STTI channel setting. 
     (7) 
     The terminal device according to (5), in which the receiving unit performs a reception process on all the second PDSCH candidates. 
     (8) 
     A base station device that communicates with a terminal device, including: 
     a higher layer processing unit configured to set an STTI channel setting in the terminal device through signaling of a higher layer; and 
     a transmitting unit configured to transmit a first PDSCH in a case in which the STTI channel setting is not set and transmit a second PDSCH in a case in which the STTI channel setting is set, 
     in which the first PDCCH is mapped to one or more resource blocks, and 
     the second PDCCH is mapped to one or more sub resource blocks defined in accordance with a smaller number of symbols than a number of symbols corresponding to a resource block. 
     (9) 
     A communication method used in a terminal device that communicates with a base station device, including: 
     a step of setting an STTI channel setting through signaling of a higher layer from the base station device; and 
     a step of receiving a first PDSCH in a case in which the STTI channel setting is not set and receiving a second PDSCH in a case in which the STTI channel setting is set, 
     in which the first PDCCH is mapped to one or more resource blocks, and 
     the second PDCCH is mapped to one or more sub resource blocks defined in accordance with a smaller number of symbols than a number of symbols corresponding to a resource block. 
     (10) 
     A communication method used in a base station device that communicates with a terminal device, including: 
     a step of setting an STTI channel setting in the terminal device through signaling of a higher layer; and 
     a step of transmitting a first PDSCH in a case in which the STTI channel setting is not set and transmitting a second PDSCH in a case in which the STTI channel setting is set, 
     in which the first PDCCH is mapped to one or more resource blocks, and 
     the second PDCCH is mapped to one or more sub resource blocks defined in accordance with a smaller number of symbols than a number of symbols corresponding to a resource block. 
     REFERENCE SIGNS LIST 
     
         
           1  base station device 
           2  terminal device 
           101 ,  201  higher layer processing unit 
           103 ,  203  control unit 
           105 ,  205  receiving unit 
           107 ,  207  transmitting unit 
           109 ,  209  transceiving antenna 
           1051 ,  2051  decoding unit 
           1053 ,  2053  demodulating unit 
           1055 ,  2055  demultiplexing unit 
           1057 ,  2057  wireless receiving unit 
           1059 ,  2059  channel measuring unit 
           1071 ,  2071  encoding unit 
           1073 ,  2073  modulating unit 
           1075 ,  2075  multiplexing unit 
           1077 ,  2077  wireless transmitting unit 
           1079  downlink reference signal generating unit 
           2079  uplink reference signal generating unit