Patent Publication Number: US-11381351-B2

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

Description:
TECHNICAL FIELD 
     The present invention relates to a terminal apparatus, a base station apparatus, and a communication method. 
     This application claims priority based on JP 2017-118525 filed on Jun. 16, 2017, the contents of which are incorporated herein by reference. 
     BACKGROUND ART 
     A radio access method and a radio network for cellular mobile communication (hereinafter, referred to as “Long Term Evolution (LTE),” or “Evolved Universal Terrestrial Radio Access (E-UTRA)”) have been studied in the 3rd Generation Partnership Project (3GPP). In LTE, a base station apparatus is also referred to as an evolved NodeB (eNodeB), and a terminal apparatus is also referred to as user equipment (UE). LTE is a cellular communication system in which multiple areas are deployed in a cellular structure, with each of the multiple areas being covered by a base station apparatus. A single base station apparatus may manage multiple cells. 
     The 3GPP has studied standards for the next generation (New Radio or NR) (NPL 1) to make a proposal for International Mobile Telecommunications (IMT)-2020 a standard for next-generation mobile communication systems, standardized by the International Telecommunications Union (ITU). NR is required to satisfy requirements for three scenarios including enhanced Mobile BroadBand (eMBB), massive Machine Type Communication (mMTC), and Ultra Reliable and Low Latency Communication (URLLC) in a single technology framework. 
     With respect to NR, code block group (CBG)-based transmission has been studied for transmission and/or reception of a large volume of data (NPL 2). CBG-based transmission may mean transmitting or receiving only some of transport blocks for initial transmission. In CBG-based transmission, a HARQ-ACK is transmitted for each CBG. Each HARQ-ACK corresponding to a CBG is generated based on the result of decoding of the CBG. 
     CITATION LIST 
     Non Patent Literature 
     
         
         NPL 1: “New SID proposal: Study on New Radio Access Technology,” RP-160671, NTT docomo, 3GPP TSG RAN Meeting #71, Goteborg, Sweden, 7 to 10 Mar. 2016. 
         NPL 2: “Consideration on CB group-based HARQ operation,” R1-1707661, Hangzhou, China, 15 to 19 May 2017. 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     However, transmission of a HARQ-ACK corresponding to a CBG has not been fully studied. 
     The present invention provides a terminal apparatus that can efficiently perform uplink and/or downlink communication, a communication method for the terminal apparatus, a base station apparatus that can efficiently perform uplink and/or downlink communication, and a communication method for the base station apparatus. 
     Solution to Problem 
     (1) According to some aspects of the present invention, the following measures are provided. That is, a first aspect of the present invention is a terminal apparatus comprising: a receiver configured to receive Radio Resource Control (RRC) information indicating a maximum number of Code Block Groups (CBGs) X for one transport block for a serving cell; and a generation unit configured to generate X Hybrid Automatic Repeat request ACKnowledgement (HARQ-ACK) bits corresponding to the one transport block, in which the transport block includes N CB  code blocks (CBs), in a case that the number of CBs N CB  is less than the maximum number of CBGs X, the number of CBGs for the one transport block is N CB , and the generation unit generates N CB  HARQ-ACK bits for the N CB  CBGs and X-N CB  negative-acknowledgements (NACKs) as the X HARQ-ACK bits. 
     (2) A second aspect of the present invention is a terminal apparatus, in which in a case that all code blocks included in a CBG of the CBGs have been successfully decoded, the generation unit generates an ACK as a HARQ-ACK bit corresponding to the CBG, and in a case that at least one code block included in a CBG of the CBGs has not been successfully decoded, the generation unit generates a NACK as a HARQ-ACK bit of the CBG. 
     (3) A third aspect of the present invention is a communication method for a terminal apparatus, the method including the steps of: receiving Radio Resource Control (RRC) information indicating a maximum number of Code Block Groups (CBGs) X for one transport block for a serving cell; and generating X Hybrid Automatic Repeat request ACKnowledgement (HARQ-ACK) bits corresponding to the one transport block, in which the one transport block includes N CB  code blocks (CBs), in a case that the number of CBs N CB  is less than the maximum number of CBGs X, the number of CBGs for the one transport block is N CB , and N CB  HARQ-ACK bits for the N CB  CBGs and X-N CB  negative-acknowledgements (NACKs) are generated as the X HARQ-ACK bits. 
     (4) A fourth aspect of the present invention is a communication method for a terminal apparatus, in which in a case that all code blocks included in a CBG of the CBGs have been successfully decoded, an ACK is generated as a HARQ-ACK bit corresponding to the CBG, and in a case that at least one code block included in a CBG of the CBGs has not been successfully decoded, a NACK is generated as a HARQ-ACK bit of the CBG. 
     (5) A fifth aspect of the present invention is a base station apparatus including: a transmitter configured to transmit Radio Resource Control (RRC) information indicating a maximum number of Code Block Groups (CBGs) X for one transport block for a serving cell; and a receiver configured to receive X Hybrid Automatic Repeat request ACKnowledgement (HARQ-ACK) bits corresponding to the one transport block, in which the one transport block includes N CB  code blocks (CBs), in a case that the number of CBs N CB  is less than the maximum number of CBGs X, the number of CBGs for the one transport block is N CB , and the receiver receives N CB  HARQ-ACK bits for the N CB  CBGs and X-N CB  negative-acknowledgements (NACKs) as the X HARQ-ACK bits. 
     (6) A sixth aspect of the present invention is a base station apparatus, in which, in a case that all code blocks included in a CBG of the CBGs have been successfully decoded, the receiver receives an ACK as a HARQ-ACK bit corresponding to the CBG, and in a case that at least one code block included in a CBG of the CBGs has not been successfully decoded, the receiver receives a NACK as a HARQ-ACK bit of the CBG. 
     (7) A seventh aspect of the present invention is a communication method for a base station apparatus, the method including the steps of: transmitting Radio Resource Control (RRC) information indicating a maximum number of Code Block Groups (CBGs) X for one transport block for a serving cell; and receiving X Hybrid Automatic Repeat request ACKnowledgement (HARQ-ACK) bits corresponding to the one transport block, in which the one transport block includes N CB  code blocks (CBs), in a case that the number of CBs N CB  is less than the maximum number of CBGs X, the number of CBGs for the one transport block is N CB , and N CB  HARQ-ACK bits for the N CB  CBGs and X-N CB  negative-acknowledgements (NACKs) are received as the X HARQ-ACK bits. 
     (8) An eighth aspect of the present invention is a communication method for a base station apparatus, in which, in a case that all code blocks included in a CBG of the CBGs have been successfully decoded, an ACK is received as a HARQ-ACK bit corresponding to the CBG, and in a case that at least one code block included in a CBG of the CBGs has not been successfully decoded, a NACK is received as a HARQ-ACK bit of the CBG. 
     Advantageous Effects of Invention 
     According to an aspect of the present invention, the terminal apparatus can efficiently perform uplink and/or downlink communication. Furthermore, the base station apparatus can efficiently perform uplink and/or downlink communication. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a conceptual diagram of a radio communication system according to the present embodiment. 
         FIG. 2  is an example illustrating a configuration of a radio frame, subframes, and slots according to an aspect of the present embodiment. 
         FIG. 3  is a diagram illustrating an example of a configuration of a transmission process  3000  of a physical layer. 
         FIG. 4  is a diagram illustrating a configuration example of a coding processing unit  3001  according to the present embodiment. 
         FIG. 5  is a diagram illustrating an example of an operation in which a first sequence b k   0  is segmented into multiple first sequence groups b k   n  (n=1 to 3 in  FIG. 5 ) according to an aspect of the present embodiment. 
         FIG. 6  is a diagram illustrating an example of an operation in which the first sequence b k   0  is segmented into multiple first sequence groups b k   n  (n=1 to 3 in  FIG. 6 ) according to an aspect of the present embodiment. 
         FIG. 7  is a diagram illustrating an example of a first procedure for calculating the number of code blocks in a code block segmentation unit  4011  according to an aspect of the present embodiment. 
         FIG. 8  is a diagram illustrating an example of downlink control information according to the present embodiment. 
         FIG. 9  is a diagram illustrating configuration examples of CBG according to an aspect of the present embodiment. 
         FIG. 10  is a diagram illustrating an example of correspondence of HARQ-ACKs (j), CBGs, and transport blocks according to the present embodiment. 
         FIG. 11  is a diagram illustrating an example of transmission of HARQ-ACKs according to the present embodiment. 
         FIG. 12  is a diagram illustrating another example of the correspondence of HARQ-ACKs (j), CBGs, and transport blocks according to the present embodiment. 
         FIG. 13  is a diagram illustrating an example of transmitting HARQ-ACKs corresponding to transport blocks according to the present embodiment. 
         FIG. 14  is a diagram illustrating an example of encoding HARQ-ACKs generated for each CBG to binary bits according to the present embodiment. 
         FIG. 15  is a diagram illustrating another example of the correspondence of HARQ-ACKs (j), CBGs, and transport blocks according to the present embodiment. 
         FIG. 16  is a schematic block diagram illustrating a configuration of a terminal apparatus  1  according to the present embodiment. 
         FIG. 17  is a schematic block diagram illustrating a configuration of a base station apparatus  3  according to the present embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will be described below. The expression “given” included in the following description may be construed as “determined” or “configured.” 
       FIG. 1  is a conceptual diagram of a radio communication system according to the present embodiment. In  FIG. 1 , a radio communication system includes terminal apparatuses  1 A to  1 C and a base station apparatus  3 . Hereinafter, the terminal apparatuses  1 A to  1 C are each also referred to as a terminal apparatus  1 . 
     Hereinafter, carrier aggregation will be described. 
     According to the present embodiment, one or multiple serving cells are configured for the terminal apparatus  1 . A technology in which the terminal apparatus  1  communicates via the multiple serving cells is referred to as cell aggregation or carrier aggregation. The multiple serving cells may include one primary cell and one or multiple secondary cells. The primary cell is a serving cell in which an initial connection establishment procedure has been performed, a serving cell in which a connection re-establishment procedure has been initiated, or a cell indicated as a primary cell in a handover procedure. Here, the primary cell may be used for transmission on a PUCCH. The secondary cell may be configured at a point of time when or after a Radio Resource Control (RRC) connection is established. 
     A carrier corresponding to a serving cell in the downlink is referred to as a downlink component carrier. A carrier corresponding to a serving cell in the uplink is referred to as an uplink component carrier. The downlink component carrier and the uplink component carrier are collectively referred to as a component carrier. 
     The terminal apparatus  1  can perform simultaneous transmission and/or reception on multiple physical channels in multiple serving cells (component carriers). A single physical channel is transmitted in a single serving cell (component carrier) out of the multiple serving cells (component carriers). 
     Here, the base station apparatus  3  may configure one or multiple serving cells through higher layer signaling (e.g., RRC signaling, and RRC information). For example, one or multiple secondary cells may be configured to form a set of multiple serving cells with a primary cell. In the present embodiment, the carrier aggregation is applied to the terminal apparatus  1 , unless specified otherwise. The terminal apparatus  1  performs channel transmission and/or reception in the multiple serving cells. 
     An example of a configuration of a radio frame according to the present embodiment will be described below. 
       FIG. 2  is an example illustrating a configuration of a radio frame, subframes, and slots according to an aspect of the present embodiment. In the example illustrated in  FIG. 2 , a length of each slot is 0.5 ms, a length of each subframe is 1 ms, and a length of the radio frame is 10 ms. The slot may be a unit of resource allocation in the time domain. The slot may be a unit to which one transport block is mapped. A transport block may be mapped to one slot. The transport block may be a unit of data transmitted in a prescribed interval (e.g., transmission time interval or TTI) defined in a higher layer (e.g., Mediam Access Control or MAC). 
     A length of the slot may be given according to the number of OFDM symbols. For example, the number of OFDM symbols may be 7 or 14. The length of the slot may be given based on at least a length of an OFDM symbol. The length of the OFDM symbol may be given at least based on a second subcarrier spacing. The length of the OFDM symbol may be given at least based on the number of points in Fast Fourier Transform (FFT) used to generate the OFDM symbol. The length of the OFDM symbol may include a length of a cyclic prefix (CP) added to the OFDM symbol. Here, the OFDM symbol may be called a symbol. In addition, in a case that a communication scheme other than OFDM is used in communication between the terminal apparatus  1  and the base station apparatus  3  (e.g., in a case that SC-FDMA or DFT-s-OFDM is used, etc.), a SC-FDMA symbol and/or a DFT-s-OFDM symbol to be generated is also referred to as an OFDM symbol. In other words, the OFDM symbol may include the DFT-s-OFDM symbol and/or the SC-FDMA symbol. The length of the slot may be, for example, 0.25 ms, 0.5 ms, 1 ms, 2 ms, or 3 ms. OFDM may include SC-FDMA or DFT-s-OFDM. 
     The OFDM includes a multi-carrier communication scheme in which waveform shaping (Pulse Shape), PAPR reduction, out-of-band radiation reduction, or filtering, and/or phase processing (e.g., phase rotation, etc.) are applied. The multi-carrier communication scheme may be a communication scheme for generating/transmitting a signal in which multiple subcarriers are multiplexed. 
     A length of a subframe may be 1 ms. The length of the subframe may be given based on a first subcarrier spacing. For example, in a case that the first subcarrier spacing is 15 kHz, the length of the subframe may be 1 ms. Each subframe may be configured to include one or multiple slots. For example, the subframe may be configured to include two slots. 
     The radio frame may be configured to include multiple subframes. The number of subframes for the radio frame may be, for example, 10. The radio frame may be configured to include multiple slots. The number of slots for the radio frame may be, for example, 10. 
     A physical channel and a physical signal according to various aspects of the present embodiment will be described below. The terminal apparatus may transmit the physical channel and/or the physical signal. The base station apparatus may transmit the physical channel and/or the physical signal. 
     Downlink physical channels and downlink physical signals are collectively referred to as downlink signals. Uplink physical channels and uplink physical signals are collectively referred to as uplink signals. Downlink physical channels and uplink physical channels are collectively referred to as physical channels. Downlink physical signals and uplink physical signals are collectively referred to as physical signals. 
     In uplink radio communication from the terminal apparatus  1  to the base station apparatus  3 , at least the following uplink physical channels may be used. The uplink physical channels may be used by a physical layer for transmission of information output from a higher layer.
         Physical Uplink Control Channel (PUCCH)   Physical Uplink Shared Channel (PUSCH)   Physical Random Access Channel (PRACH)       

     The PUCCH is used to transmit uplink control information (UCI). The uplink control information includes: Channel State Information (CSI) of a downlink channel; a Scheduling Request (SR) to be used to request a PUSCH (UpLink-Shared Channel or UL-SCH) resource for initial transmission; and a Hybrid Automatic Repeat request ACKnowledgement (HARQ-ACK) for downlink data (a transport block or TB, a Medium Access Control Protocol Data Unit or MAC PDU, a DownLink-Shared Channel or DL-SCH, a Physical Downlink Shared Channel or PDSCH, a Code Block or CB, or a Code Block Group or CBG). The HARQ-ACK indicates an acknowledgement (ACK) or a negative-acknowledgement (NACK). 
     The HARQ-ACK is also referred to as an ACK/NACK, HARQ feedback, HARQ-ACK feedback, a HARQ response, a HARQ-ACK response, HARQ information, HARQ-ACK information, HARQ control information, and HARQ-ACK control information. In a case that downlink data is successfully decoded, an ACK for the downlink data is generated. In a case that the downlink data is not successfully decoded, a NACK for the downlink data is generated. Discontinuous Transmission (DTX) may mean that the downlink data has not been detected. The discontinuous Transmission (DTX) may mean that data for which a HARQ-ACK response is to be transmitted has not been detected. The HARQ-ACK may include a HARQ-ACK for a Code Block Group (CBG). The HARQ-ACK for some or all of the CBGs included in a transport block may be transmitted on a PUCCH or PUSCH. The CBG will be described below. 
     The channel state information (CSI) may include a channel quality indicator (CQI) and a rank indicator (RI). The channel quality indicator may include a precoder matrix indicator (PMI). The channel state information may include a precoder matrix indicator. The CQI is an indicator associated with channel quality (propagation strength), and the PMI is an indicator indicating a precoder. The RI is an indicator indicating a transmission rank (or the number of transmission layers). According to the present embodiment, the terminal apparatus  1  may transmit the PUCCH in the primary cell. 
     The PUSCH is used to transmit uplink data (TB, MAC PDU, UL-SCH, PUSCH, CB, and CBG). The PUSCH may be used to transmit the HARQ-ACK and/or channel state information along with the uplink data. The PUSCH may be used to transmit only the channel state information or only the HARQ-ACK and the channel state information. The PUSCH is used to transmit a random access message  3 . 
     The PRACH may be used to transmit a random access preamble (random access message  1 ). The PRACH may be used to indicate at least some of an initial connection establishment procedure, a handover procedure, a connection re-establishment procedure, synchronization (timing adjustment) for transmission of uplink data, and a request for a PUSCH (UL-SCH) resource. 
     In uplink radio communication from the terminal apparatus  1  to the base station apparatus  3 , the following uplink physical signals may be used. The uplink physical signals may not be used to transmit information output from a higher layer, but is used by a physical layer.
         Uplink Reference Signal (UL RS)       

     According to the present embodiment, at least the following two types of uplink reference signal may be at least used.
         Demodulation Reference Signal (DMRS)   Sounding reference signal (SRS)       

     The DMRS is associated with transmission of a PUSCH and/or a PUCCH. The DMRS may be multiplexed with the PUSCH or the PUCCH. The base station apparatus  3  uses the DMRS in order to perform channel compensation of the PUSCH or the PUCCH. Transmission of both of the PUSCH and the DMRS is hereinafter referred to simply as transmission of the PUSCH. The DMRS may correspond to the PUSCH. Transmission of both of the PUCCH and the DMRS is hereinafter referred to simply as transmission of the PUCCH. The DMRS may correspond to the PUCCH. 
     The SRS may not be associated with transmission of the PUSCH and/or the PUCCH. An SRS may be associated with transmission of the PUSCH and/or the PUCCH. The base station apparatus  3  may use the SRS for measuring a channel state. The SRS may be transmitted at the end of the subframe in an uplink slot or in a prescribed number of OFDM symbols from the end. 
     The following downlink physical channels may be used for downlink radio communication from the base station apparatus  3  to the terminal apparatuses  1 . The downlink physical channels may be used by the physical layer to transmit information output from the higher layer.
         Physical Broadcast Channel (PBCH)   Physical Downlink Shared Channel (PDSCH)   Physical Downlink Control Channel (PDCCH)       

     The PBCH is used for broadcasting a master information block (MIB, BCH, or Broadcast Channel) that is commonly used by the terminal apparatuses  1 . The PBCH may be transmitted at a prescribed transmission interval. For example, the PBCH may be transmitted at an interval of 80 ms. At least some of information included in the PBCH may be updated every 80 ms. The PBCH may include 288 subcarriers. The PBCH may include 2, 3, or 4 OFDM symbols. The MIB may include information on an identifier (index) of a synchronization signal. The MIB may include information indicating at least some of the number of the slot in which the PBCH is transmitted, the number of the subframe in which the PBCH is transmitted, and the number of the radio frame in which the PBCH is transmitted. First configuration information may be included in the MIB. The first configuration information may be configuration information used at least in some or all of a random access message  2 , a random access message  3 , and a random access message  4 . 
     The PDSCH is used to transmit downlink data (TB, MAC PDU, DL-SCH, PDSCH, CB, and CBG). The PDSCH is at least used to transmit the random access message  2  (random access response). The PDSCH is at least used to transmit system information including parameters used for initial access. 
     The PDCCH is used to transmit downlink control information (DCI). The downlink control information is also called a DCI format. The downlink control information may at least include any of a downlink grant or an uplink grant. The downlink grant is also referred to as a downlink assignment or a downlink allocation. The uplink grant and the downlink grant are also collectively referred to as a grant. 
     A single downlink grant is at least used for scheduling of a single PDSCH within a single serving cell. The downlink grant may be at least used for the scheduling of the PDSCH in the same slot as the slot in which the downlink grant is transmitted. 
     A single uplink grant is at least used for scheduling of a single PUSCH within a single serving cell. 
     For example, the downlink control information may include a new data indicator (NDI). The new data indicator may be used to at least indicate whether the transport block corresponding to the new data indicator is of initial transmission. The new data indicator may be information indicating whether a most recently transmitted transport block corresponding to a prescribed HARQ process number is the same as the transport block corresponding to the HARQ process number and included in the PDSCH and/or the PUSCH scheduled by the downlink control information including the new data indicator. The HARQ process number is a number used to identify the HARQ process. The HARQ process number may be included in the downlink control information. The HARQ process is a process for managing a HARQ. The new data indicator may indicate whether the transmission of the transport block corresponding to the prescribed HARQ process number and included in the PDSCH and/or the PUSCH scheduled by the downlink control information including the new data indicator is retransmission of the transport block corresponding to the prescribed HARQ process number and included in a most recently transmitted PDSCH and/or PUSCH. Whether the transmission of the transport block included in the PDSCH and/or the PUSCH scheduled by the downlink control information is retransmission of the most recently transmitted transport block may be given based on whether the new data indicator has been switched (or toggled) from a new data indicator corresponding to the most recently transmitted transport block. 
     That is, the new data indicator indicates initial transmission or retransmission. A HARQ entity of the terminal apparatuses  1  indicates to a certain HARQ process to trigger the initial transmission in a case that the new data indicator provided by the HARQ information has been toggled compared to the value of the new data indicator for a preceding transmission of the certain HARQ process. The HARQ entity indicates to the certain HARQ process to trigger retransmission in a case that the new data indicator provided by the HARQ information has not been toggled compared to the value of the new data indicator for the preceding transmission of the certain HARQ process. Note that whether the new data indicator has been toggled may be determined in the HARQ process. 
     In downlink radio communication, the following downlink physical signals may be used. The downlink physical signals may not be used for transmission of information output from the higher layer, but may be used by the physical layer.
         Synchronization signal (SS)   Downlink Reference Signal (DL RS)       

     The synchronization signal is used for the terminal apparatus  1  to establish synchronization in a frequency domain and a time domain in the downlink. The synchronization signal may at least include a primary synchronization signal (PSS) and a second synchronization signal (SSS). 
     The synchronization signal including an ID of a target cell (cell ID) may be transmitted. The synchronization signal including a sequence generated at least based on the cell ID may be transmitted. The synchronization signal including the cell ID may means that the sequence of the synchronization signal is given based on the cell ID. The synchronization signal may be transmitted with application of a beam (or precoder). 
     The beam exhibits a phenomenon in which antenna gain varies depending on directions. The beam may be given at least based on the directivity of an antenna. In addition, the beam may also be given at least based on a phase transformation of a carrier signal. In addition, the beam may also be given by the application of the precoder. 
     The downlink reference signal is at least used for the terminal apparatus  1  to perform channel compensation of the downlink physical channel. The downlink reference signal is at least used for the terminal apparatus  1  to calculate channel state information of the downlink. 
     According to the present embodiment, the following two types of downlink reference signals are used.
         Demodulation Reference Signal (DMRS)   Shared Reference Signal (Shared RS)       

     The DMRS corresponds to transmission of the PDCCH and/or the PDSCH. The DMRS is multiplexed with the PDCCH or the PDSCH. The terminal apparatuses  1  may use the DMRS corresponding to the PDCCH or the PDSCH in order to perform channel compensation of the PDCCH or the PDSCH. Hereinafter, transmission of both of the PDCCH and the DMRS corresponding to the PDCCH is simply referred to as transmission of the PDCCH. Hereinafter, transmission of both of the PDSCH and the DMRS corresponding to the PDSCH is simply referred to as transmission of the PDSCH. 
     The Shared RS may correspond to transmission of at least the PDCCH. The Shared RS may be multiplexed with the PDCCH. The terminal apparatuses  1  may use the Shared RS in order to perform channel compensation of the PDCCH. Hereinafter, transmission of both of the PDCCH and the Shared RS is also simply referred to as transmission of the PDCCH. 
     The DMRS may be an RS individually configured for the terminal apparatus  1 . The sequence of the DMRS may be given at least based on parameters individually configured for the terminal apparatus  1 . The DMRS may be individually transmitted for the PDCCH and/or the PDSCH. On the other hand, the Shared RS may be an RS commonly configured for multiple terminal apparatuses  1 . The sequence of the Shared RS may be given regardless of the parameters individually configured for the terminal apparatus  1 . For example, the sequence of the Shared RS may be given based on at least some of the number of the slot, the number of a mini slot, and a cell identity (ID). The Shared RS may be an RS to be transmitted regardless of whether the PDCCH and/or the PDSCH has been transmitted. 
     The BCH, UL-SCH, and DL-SCH described above are transport channels. A channel used in a 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 or a MAC PDU. A Hybrid Automatic Repeat reQuest (HARQ) is controlled for each transport block in the MAC layer. The transport block is a unit of data that the MAC layer delivers to the physical layer. In the physical layer, the transport block is mapped to a codeword, and a modulation process is performed for each codeword. 
     The base station apparatus  3  and the terminal apparatus  1  may exchange (transmit and/or receive) signals in the higher layer. For example, the base station apparatus  3  and the terminal apparatus  1  may transmit and/or receive Radio Resource Control (RRC) signaling (also referred to as a Radio Resource Control (RRC) message or Radio Resource Control (RRC) information) in an RRC layer. Furthermore, the base station apparatus  3  and the terminal apparatus  1  may transmit and/or receive, in the MAC layer, a MAC Control Element (CE). Here, the RRC signaling and/or the MAC CE is also referred to as higher layer signaling. 
     The PUSCH and the PDSCH are at least used to transmit the RRC signaling and the MAC CE. Here, the RRC signaling transmitted from the base station apparatus  3  on the PDSCH may be RRC signaling common to multiple terminal apparatuses  1  in a cell. The RRC signaling common to the multiple terminal apparatuses  1  in the cell is also referred to as common RRC signaling. The RRC signaling transmitted from the base station apparatus  3  on the PDSCH may be RRC signaling dedicated to a certain terminal apparatus  1  (which is also referred to as dedicated signaling or UE specific signaling). The RRC signaling dedicated to the terminal apparatus  1  is also referred to as dedicated RRC signaling. A cell specific parameter may be transmitted using the RRC signaling common to the multiple terminal apparatuses  1  in the cell or the RRC signaling dedicated to the certain terminal apparatus  1 . A UE specific parameter may be transmitted using the RRC signaling dedicated to the certain terminal apparatus  1 . 
     A Broadcast Control CHannel (BCCH), a Common Control CHannel (CCCH), and a Dedicated Control CHannel (DCCH) are logical channels. For example, the BCCH is a channel of the higher layer used to transmit the MIB. Additionally, the BCCH is the channel of the higher layer used to transmit system information. Note that the system information may include System Information Block type 1 (SIB1). Furthermore, the system information may also include a System Information (SI) message including System Information Block type 2 (SIB2). Furthermore, the Common Control Channel (CCCH) is a channel of the higher layer used to transmit information common to the multiple terminal apparatuses  1 . Here, the CCCH is used for a terminal apparatus  1  that is not in a RRC connected state, for example. Furthermore, the Dedicated Control Channel (DCCH) is a channel of the higher layer used to transmit individual control information (dedicated control information) to the terminal apparatus  1 . Here, the DCCH is used for a terminal apparatus  1  that is in the RRC connected state, for example. 
     The BCCH in the logical channel may be mapped to the BCH, the DL-SCH, or the UL-SCH in the transport channel. The CCCH in the logical channel may be mapped to the DL-SCH or the UL-SCH in the transport channel. The DCCH in the logical channel may be mapped to the DL-SCH or the UL-SCH in the transport channel. 
     The UL-SCH in the transport channel is mapped to the PUSCH in the physical channel. The DL-SCH in the transport channel is mapped to the PDSCH in the physical channel. The BCH in the transport channel is mapped to the PBCH in the physical channel. 
     A transmission process  3000  by the base station apparatus  3  and/or the terminal apparatuses  1  will be described below. 
       FIG. 3  is a diagram illustrating an example of a configuration of the transmission process  3000  of the physical layer. The transmission process  3000  is configured to include at least some or all of a coding processing unit (Coding)  3001 , a scrambling processing unit (Scrambling)  3002 , and a modulation mapping processing unit (Modulation mapper)  3003 , a layer mapping processing unit (Layer mapper)  3004 , a transmission precode processing unit (Transform precoder)  3005 , a precode processing unit (Precoder)  3006 , a resource element mapping processing unit (Resource element mapper)  3007 , and a baseband signal generation processing unit (OFDM baseband signal generation)  3008 . 
     The coding processing unit  3001  may have a function of converting a transport block (or a data block, transport data, transmission data, a transmission code, a transmission block, a payload, information, an information block, and the like.) sent (or notified, delivered, transmitted, transferred, and the like.) from a higher layer into coded bits through error correction coding processing. The error correction coding at least includes some or all of a Turbo code, a Low Density Parity Check (LDPC) code, a convolutional code (such as a Convolutional code or Tail biting convolutional code), and a repetition code. The coding processing unit  3001  has a function of transmitting the coded bits to the scrambling processing unit  3002 . Details of the operation of the coding processing unit  3001  will be described below. 
     The scrambling processing unit  3002  may have a function of converting the coded bits into scrambled bits (scramble bit) through a scrambling process. The scrambled bits may be obtained by taking the sum of the coded bits and the scrambling sequence having 2 as a divisor. In other words, the scrambling may have the sum of the coded bits and the scrambling sequence having 2 as a divisor. The scrambling sequence may be a sequence generated by a pseudo-random function based on a unique sequence (e.g., C-RNTI). 
     The modulation mapping processing unit  3003  may have a function of converting the scrambled bits into a modulated sequence (modulation symbol) through modulation mapping processing. The modulation symbol may be obtained by performing a modulation process of the scrambled bits, the modulation process including Quaderature Phase Shift Keying (QPSK), 16 Quaderature Amplitude Modulation (QAM), 64 QAM, 256 QAM, or the like. 
     The layer mapping processing unit  3004  may have a function of mapping the modulation symbol to each layer. The layer may be an indicator of multiplicity of physical layer signals in a spatial domain. For example, in a case that the number of layers is 1, no spatial multiplexing is performed. In addition, in a case that the number of layers is 2, two types of modulation symbols are spatially multiplexed. 
     For example, the transmission precode processing unit  3005  may have a function of generating a transmission symbol by performing transmission precode processing on the modulation symbol mapped to each layer. The modulation symbol and/or the transmission symbol may be a complex-valued symbol. The transmission precode processing includes processing such as DFT spread (DFT spreading). The transmission precode processing unit  3005  may be given whether to perform the transmission precode processing based on information included in the higher layer signaling. The transmission precode processing unit  3005  may be given whether to perform the transmission precode processing at least based on information included in the first system information. The transmission precode processing unit  3005  may be given whether to perform the transmission precode processing of the random access message  3  at least based on the information included in the first system information. The transmission precode processing unit  3005  may be given whether to perform the transmission precode processing based on information included in the control channel. Furthermore, the transmission precode processing unit  3005  may be given whether to perform the transmission precode processing based on preconfigured information. 
     For example, the precode processing unit  3006  may have a function of generating a transmission symbol for each transmit antenna port by multiplying the transmission symbol by a precoder. The transmit antenna port is a logical antenna port. One transmit antenna port may include multiple physical antennas. The logical antenna port may be identified by the precoder. 
     The antenna port is defined as an antenna port that enables a channel conveyed by a certain symbol in a certain antenna port to be inferred from a channel conveyed by another symbol in the same antenna port. That is, for example, in a case that a first physical channel and a first reference signal are conveyed by symbols in the same antenna port, a channel compensation of the first physical channel may be performed by using the first reference signal. Here, the same antenna port may mean the same antenna port number (the number for identifying an antenna port). Here, the symbols may be, for example, at least a part of OFDM symbols. Furthermore, the symbols may be resource elements. 
     For example, the resource element mapping processing unit  3007  may have a function of mapping the transmission symbol mapped to the transmit antenna port to a resource element. Details of the method for mapping to the resource element in the resource element mapping processing unit  3007  will be described below. 
     The baseband signal generation processing unit  3008  may have a function of converting the transmission symbol mapped to the resource element into a baseband signal. The processing for converting the transmission symbol into the baseband signal may include, for example, Inverse Fast Fourier Transform (IFFT) processing, windowing processing, filter processing, and the like. 
     Hereinafter, an operation of the coding processing unit  3001  will be described in detail. 
       FIG. 4  is a diagram illustrating a configuration example of the coding processing unit  3001  according to the present embodiment. The coding processing unit  3001  is configured to include at least one of a CRC attachment unit  4001 , a segmentation and CRC attachment unit  401 , an encoder unit  4002 , sub-block interleaver units  4003 , a bit collection unit  4004 , a bit selection and pruning unit  4005 , and a concatenation unit  4006 . Here, the segmentation and CRC attachment unit  401  is configured to include at least one of a code block segmentation unit  4011  and one or multiple CRC attachment units  4012 . 
     A transport block a k  is input to the CRC attachment unit  4001 . The CRC attachment unit  4001  may generate a first CRC sequence as a redundancy bit for error detection based on the input transport block. The generated first CRC sequence is attached to the transport block. A first sequence b k   0  including the transport block to which the first CRC sequence has been attached is output from the CRC attachment unit  4001 . 
     The first CRC sequence may be a CRC sequence corresponding to the transport block. The first CRC sequence may be used to determine whether the transport block has been successfully decoded. The first CRC sequence may be used for error detection of the transport block. The first sequence b k   0  may be a transport block to which the first CRC sequence has been attached. 
     The first sequence b k   0  may be segmented into one or multiple first sequence groups. The first sequence group is also referred to as a Code Block Group (CBG). 
       FIG. 5  is a diagram illustrating an example of an operation in which the first sequence b k   0  is segmented into multiple first sequence groups b k   n  (n=1 to 3 in  FIG. 5 ) according to an aspect of the present embodiment. The first sequence groups b k   n  each may have an equal length or a different length. The first CRC sequence may be mapped only to one of the first sequence groups (first sequence group b k   n  in  FIG. 5 ). 
       FIG. 6  is a diagram illustrating an example of an operation in which a first sequence b k   0  is segmented into multiple first sequence groups b k   n  (n=1 to 3 in  FIG. 6 ) according to an aspect of the present embodiment. The first sequence b k   0  is rearranged (interleaved) based on a first code, which causes an interleaved first sequence b k   0 . The interleaved first sequence b k   0  may be segmented into multiple first sequence groups b k   n . In other words, the order of the first sequence b k   0  and the interleaved first sequence b k   0  may be different. 
     The first code may include a pseudo-random function (e.g., an M sequence, a gold sequence, or the like). Interleaving based on the first code may include first interleaving. The interleaving based on the first code may be bit interleaving based on the first code. 
     The interleaving based on the first code may be performed for each of the first sequence groups b k   n . 
     A second CRC sequence generated at least based on the first sequence groups b k   n  may be attached to the first sequence groups b k   n . The second CRC sequence may be different in length from the first CRC sequence. Methods for generating the second CRC sequence and the first CRC sequence may be different. The second CRC sequence may be used to determine whether an n-th first sequence group b k   n  has been successfully decoded. The second CRC sequence may be used for error detection of the n-th first sequence group b k   n . The second CRC sequence may be a second CRC sequence attached to the n-th first sequence group b k   n . In a case that the number of first sequence groups b k   n  is equal to or greater than the number of code blocks N CB , the second CRC sequence may not be attached to each of the first sequence groups b k   n . In a case that the number of first sequence groups b k   n  is smaller than the number of code blocks N CB , the second CRC sequence may be attached to each of the first sequence groups b k   n . For example, in a case that only one code block is included in the first sequence group b k   n , the second CRC sequence may not be attached to the first sequence group b k   n . In a case that two or more code blocks are included in the first sequence group b k   n , the second CRC sequence may be attached to the first sequence group b k   n . In a case that the number of first sequence groups b k   n  corresponding to the transport block is 1, the second CRC sequence may not be attached to the first sequence groups b k   n . 
     A second sequence b k  may be input to the code block segmentation unit  4011 . The second sequence b k  input into the code block segmentation unit  4011  may be input for each of the first sequence groups b k   n . In a case that the first sequence b k   0  is segmented into the first sequence groups b k   n , the second sequence b k  input into the code block segmentation unit  4011  may be an n-th (n is an integer of 1 or greater) first sequence group b k   n . In a case that the first sequence b k   0  is not segmented into the first sequence groups b k   n , the second sequence b k  input to the code block segmentation unit  4011  may be the first sequence b k   0 . 
       FIG. 7  is a diagram illustrating an example of a first procedure for calculating the number of code blocks in the code block segmentation unit  4011  according to an aspect of the present embodiment. B denotes the number of bits of the second sequence b k . N CB  denotes the number of code blocks of the second sequence b k . B′ denotes the sum of the number of bits of a third CRC sequence and the second sequence b k  attached to each code block. L denotes the number of bits of the third CRC sequence attached to one code block. 
     In a case that the number of bits B of the second sequence b k  is equal to or less than the maximum code block length Z, the number of bits L of the third CRC sequence is 0 and the number of code blocks N CB  thereof is 1, and B′ is equal to B. On the other hand, in a case that the number of bits B of the second sequence b k  is greater than the maximum code block length Z, L is 24, and the number of code blocks N CB  may be given by floor (B/(Z−L)). Here, floor (*) is a function that outputs a minimum integer no less than *. floor (*) is also referred to as a ceiling function. 
     The number of bits B of the second sequence b k  may be given by the sum of the number of bits A of a first sequence a k  and the number of bits P of a first CRC bit p k . In other words, the number of bits B of the second sequence b k  may be given by A+P. 
     The number of bits B of the second sequence b k  may include the number of bits of the second CRC sequence. 
     The maximum code block length Z may be 6144 or 8192. The maximum code block length Z may be a value other than that described above. The maximum code block length Z may be given at least based on the method of error correction coding used in the coding procedure. For example, the maximum code block length Z may be 6144 in a case that the turbo code is used in the coding procedure. For example, the maximum code block length Z may be 8192 in a case that the Low Density Parity Check (LDPC) code is used in the coding procedure. The LDPC code may be a Quasi-Cyclic LDPC (QC-LDPC) code. The LDPC code may be an LDPC-Convolutional codes (LDPC-CC) coding. 
     The code block segmentation unit  4011  segments the second sequence b k  into N CB  code blocks C rk  at least based on the calculated number of code blocks N CB . Here, r denotes an index of the code block. The index r of the code block is given by an integer value included in a range from 0 to N CB −1. 
     The code block segmentation processing by the code block segmentation unit  4011  may give at least a first code block with a first code block size and a second code block with a second code block size. 
     The second CRC attachment units  4012  may have a function of attaching the third CRC sequence to each code block. For example, in a case that the number of code blocks N CB  is 1, the third CRC sequence may not be attached to the code block. This means that L is 0 in a case that the number of code blocks N CB  is 1. On the other hand, in a case that the number of code blocks N CB  is greater than 1, the third CRC sequence of the number of bits L may be attached to each of the code blocks. The number of code blocks N CB  being greater than 1 means that the second sequence b k  is segmented into multiple code blocks. The output of the second CRC attachment unit  4012  is referred to as a code block c rk . The code block c rk  is an r-th code block. 
     Whether to transmit and/or receive a CBG in a certain serving cell is determined based on whether an RRC layer parameter (RRC parameter) cbgTransmission has been configured in the serving cell. That is, the RRC layer parameter (RRC parameter) cbgTransmission is a parameter indicating whether to transmit and/or receive the CBG in the certain serving cell. The transmission and/or reception of the CBG may mean transmitting or receiving only a portion of a transport block for the initial transmission. Note that the RRC parameter cbgTransmission may be defined (specified) for uplink (i.e., an uplink serving cell) and downlink (i.e., a downlink serving cell) in terms of certain serving cells independently of each other. Furthermore, the RRC parameter cbgTransmission may be defined (specified) in the uplink and the downlink configured for the terminal apparatus  1  independently of each other. In other words, the RRC parameter cbgTransmission may be applied to the uplink of all serving cells configured for the terminal apparatus  1 . Furthermore, the RRC parameter cbgTransmission may be applied to the downlink of all serving cells configured for the terminal apparatus  1 . 
     Furthermore, the RRC parameter cbgTransmission may be defined (specified) for each cell (serving cell). Namely, the base station apparatus  3  may transmit, to the terminal apparatus  1 , whether to configure the RRC parameter cbgTransmission for each of the one or multiple cells configured for the terminal apparatus  1 . The terminal apparatus  1  for which the RRC parameter cbgTransmission for a certain cell is not configured may not transmit and/or receive a CBG in the cell. Namely, the terminal apparatus  1  for which the RRC parameter cbgTransmission for a certain cell is not configured may not transmit or receive a portion of a transport block in the cell. The terminal apparatus  1  for which the RRC parameter cbgTransmission for a certain cell is configured may transmit and/or receive the CBG in the cell. The terminal apparatus  1  for which the RRC parameter cbgTransmission for a certain cell is not configured may not transmit or receive a portion of the transport block in the cell. The terminal apparatus  1  for which the RRC parameter cbgTransmission for a certain cell is configured may transmit or receive only a portion of the transport block for initial transmission in the cell. 
     Whether to configure the RRC parameter cbgTransmission in a certain cell is optional for a higher layer (RRC). Here, configuring the RRC parameter cbgTransmission indicates that a value of the parameter cbgTransmission transmitted in higher layer signaling is true. Configuring the value of the RRC parameter cbgTransmission to true may include transmitting and/or receiving the CBG. Configuring no RRC parameter cbgTransmission may indicate that the value of the parameter cbgTransmission transmitted in the higher layer signaling is false or that the received higher layer signaling (higher layer information) does not include the RRC parameter cbgTransmission. Configuring the value of the RRC parameter cbgTransmission to false may not include transmitting and/or receiving the CBG. 
     The base station apparatus may simultaneously transmit the RRC information indicating the number of CBGs (maximum number of CBGs) X included in one transport block to the terminal apparatus  1  in the cell and the RRC parameter cbgTransmission having a value configured to true for a certain cell. Namely, the maximum number of CBGs X may be indicated by the RRC information. The maximum number of CBGs X may be configured for the terminal apparatus  1  and a maximum number of CBGs for one transport block. Here, the number of CBGs (maximum number of CBGs) X may be configured independently for each cell. Furthermore, the number of CBGs X may be configured in a certain serving cell for uplink (i.e., an uplink serving cell) and downlink (i.e., a downlink serving cell) independently of each other. Furthermore, in a cell supporting two transport blocks, the number of CBGs X may be configured for each of the two transport blocks independently of each other. Moreover, the number of CBGs X may be common to multiple cells. For example, the base station apparatus  3  may transmit, to the terminal apparatus  1 , the higher layer signaling including the RRC information indicating the RRC parameter cbgTransmission for each of cells and the number of CBGs X common to the cells. 
     In the cell in which the RRC parameter cbgTransmission has been configured, the downlink control information may include information indicating which CBG has been actually transmitted. The information indicating which CBG has been actually transmitted is also referred to as information for indicating transmission of the CBG. The information for indicating the transmission of the CBG may indicate a CBG that has been actually included and transmitted in a PDSCH and/or a PUSCH scheduled by the downlink control information. The information for indicating the transmission of the CBG may be a bitmap given at least based on the number of CBGs N CBG  included in a transport block included in the PDSCH and/or the PUSCH scheduled by the downlink control information including the information for indicating the transmission of the CBG, and/or the number of CBGs (maximum number of CBGs) X included in the transport block. Each bit included in the bitmap may correspond to one CBG. The bit may be set to ‘1’ to indicate that the CBG is to be transmitted. The bit may be set to ‘0’ to indicate that no CBG is to be transmitted. Note that, in a case that the information for indicating the transmission of the CBG is included in a downlink grant, a CBG included in the PDSCH and actually transmitted may be indicated. Furthermore, in a case that the information for indicating the transmission of the CBG is included in an uplink grant, a CBG included in the PUSCH and retransmitted may be indicated. 
       FIG. 8  is a diagram illustrating an example of downlink control information according to the present embodiment. As one example, the information for indicating the transmission of the CBG may be mapped to, for example, a field called a CBG indication of downlink control information. Namely, the field of CBG indication may be used to indicate which CBG has been actually transmitted. The number of bits of the field of CBG indication may be a value of the number of CBGs X. In  FIG. 8 , the number of CBGs X may be 4. At this time, the downlink control information indicating the transmission of the CBG may be a 4-bit bitmap. Each bit included in the bitmap may correspond to one CBG. In  FIG. 8 , in a case that a bitmap  701  is set to ‘1111,’ it may indicate that all CBGs of the transport block are transmitted. Namely, in the case that the bitmap  701  is set to ‘1111,’ it may mean that the transport block is transmitted. Furthermore, in a case that a bitmap  702  is set to ‘1010,’ it indicates that a CBG # 1  and a CBG # 3  are transmitted. Namely, in a case that the bitmap  702  is set to ‘1010,’ it indicates that a CBG # 2  and a CBG # 4  are not transmitted. That is, the number of CBGs Y that are actually transmitted may be determined at least by the bitmap indicating the transmission of the CBG. 
     In  FIG. 8 , the field of Resource Allocation is used to indicate information of allocation of resources at a frequency and time for the PDSCH and/or the PUSCH. The field of Modulation and Coding (MCS) is used to indicate an MCS index (I MCS ) for the PDSCH or the PUSCH. By referencing the indicated MCS index (I MCS ), a corresponding modulation order (Qm), a corresponding transport block size index (I TBS ), and a corresponding redundancy version (rv idx ) are determined. Namely, the terminal apparatus  1  may determine a transport block size (TBS) at least based on the field of Resource Allocation and the field of Modulation and Coding (MCS). The field of HARQ process number is used to indicate a HARQ process number associated with the transport block to be transmitted and/or received. The HARQ process number may be an identifier for the HARQ process. 
     In addition, the downlink control information may include information indicating either whether to generate a HARQ-ACK for each CBG or whether to generate a HARQ-ACK for each transport block in the cell in which the RRC parameter cbgTransmission is configured. That is, the downlink control information may include information indicating a method for generating the HARQ-ACK. The field of HARQ indication may be used to indicate the information. The field of HARQ indication may be configured to, for example, 1 bit. The bit may be set to ‘1’ to indicate that the HARQ-ACK is generated for each CBG. The bit may be set to ‘0’ to indicate that the HARQ-ACK is generated for each transport block. 
     The HARQ-ACK may be generated for each transport block in the cell in which the RRC parameter cbgTransmission is not configured. The HARQ-ACK is not generated for each CBG in the cell in which the RRC parameter cbgTransmission is not configured. 
     In a case that the generation of the HARQ-ACK for each transport block is indicated, the terminal apparatus  1  generates the HARQ-ACK for each transport block. In a case that the transport block has been successfully decoded, an ACK for the transport block is generated. In a case that the transport block has not been successfully decoded, a NACK for the transport block is generated. 
     The downlink control information may not include information indicating the transmission of the CBG and/or information indicating the method for generating the HARQ-ACK in the cell in which the RRC parameter cbgTransmission is not configured. Furthermore, the downlink control information used for scheduling the PDSCH and/or the PUSCH for initial transmission of the transport block may not include information indicating the transmission of the CBG and/or information indicating the method for generating the HARQ-ACK. The downlink control information used for the scheduling the PDSCH and/or the PUSCH for the initial transmission of the transport block may include information indicating the transmission of the CBG and/or information indicating the method for generating the HARQ-ACK. The information indicating the transmission of the CBG and/or the information indicating the method for generating the HARQ-ACK included in the downlink control information used for scheduling the PDSCH and/or the PUSCH for the initial transmission of the transport block may be set to a predefined bit sequence (e.g., a sequence of all zeros or a sequence of all ones). In the downlink control information used for scheduling the PDSCH and/or the PUSCH for the initial transmission of the transport block, areas (bit field, information bits, bit areas, and the number of bits) to be used for the information indicating the transmission of the CBG and/or the information indicating the method for generating the HARQ-ACK may be reserved in advance. The areas (the bit field, the information bits, the bit areas, and the number of bits) for the information indicating transmission of the CBG and/or the information indicating the method for generating the HARQ-ACK included in the downlink control information used for scheduling the PDSCH and/or the PUSCH for the initial transmission of the transport block may be used at least to configure the MCS and/or the TBS. 
     Whether the PDSCH and/or PUSCH for the transport block is the initial transmission may be given at least based on the new data indicator included in the downlink control information for scheduling the PDSCH and/or PUSCH for the transport block. For example, whether the PDSCH and/or PUSCH for the transport block corresponding to a prescribed HARQ process number is of the initial transmission may be given based on whether the new data indicator included in the downlink control information for scheduling the PDSCH and/or PUSCH for the transport block has been switched from the new data indicator corresponding to the prescribed HARQ process number and the most recently transmitted transport block. 
     The downlink control information used for scheduling retransmission of the PDSCH and/or PUSCH for the transport block may include the information indicating the transmission of the CBG and/or the information indicating the method for generating the HARQ-ACK. 
     Further, in the present embodiment, the terminal apparatus  1  may determine whether to generate a HARQ-ACK for each CBG or generate a HARQ-ACK for each transport block at least based on the new data indicator and the information indicating transmission of the CBG. For example, in a case that the new data indicator corresponding to a certain HARQ process is toggled (switched) for a most recent transmission and a field of CBG indication included in a PDCCH is set to a first prescribed value (e.g., all set to one), the terminal apparatus  1  may generate the HARQ-ACK for each CBG. Furthermore, for example, in a case that the new data indicator corresponding to the certain HARQ process is toggled (switched) for the most recent transmission and the field of CBG indication included in the PDCCH is set to a second prescribed value (e.g., all set to zero), the terminal apparatus  1  may generate the HARQ-ACK for each transport block in the HARQ process. As a result, the field indicating the method for generating the HARQ-ACK can be eliminated, and the payload size of the downlink control information included in the PDCCH can be reduced. 
     A configuration of the CBG will be described below. 
     The code block group (CBG) may include one or multiple code blocks. In a case that transmission of a transport block is an initial transmission, the number of code blocks N CB  included in the transport block may be given at least based on the transport block size (TBS). Each of the N CB  code blocks may be included (segmented) in any one of X CBGs. The value of X may be given based on the RRC information and/or description in specifications, etc. The number of code blocks N CBperCBG  in each of the X CBGs may be given at least based on the transport block size. The number of code blocks in each of the CBGs may be based on the transport block size. The number of code blocks in each of the CBGs may be the same or different. Here, the difference between the number of code blocks in the CBG including the most code blocks and the number of code blocks in the CBG including the least code blocks among multiple CBGs corresponding to the same transport block is less than two. That is, the difference between the numbers of code blocks of a CBG and another CBG in the multiple CBGs corresponding to the same transport block may be merely one. 
       FIG. 9  is a diagram illustrating configuration examples of CBG according to an aspect of the present embodiment. Here, in  FIG. 9 , the number of CBGs X is indicated by the RRC information and may be 4.  FIG. 9( a )  is a diagram illustrating an example of a case that the number of code blocks N CB  included in a transport block is smaller than the number of CBGs X.  FIG. 9( b )  is a diagram illustrating an example of a case that the number of code blocks N CB  included in the transport block is equal to or greater than the number of CBGs X. In  FIG. 9( a ) , the number of code blocks N CB  included in a certain transport block # 1  is given to be 3 at least based on the TBS. In  FIG. 9( a ) , each of a CBG # 1 , a CBG # 2 , and a CBG # 3  includes one code block. In  FIG. 9( a ) , a CBG # 4  includes no code block. In  FIG. 9( a ) , the CBG # 1 , CBG # 2 , and CBG # 3  each include one more code block than the CBG # 4 . 
     In  FIG. 9( b ) , the number of code blocks N CB  included in the transport block # 1  is given to be 11 at least based on the TBS. In  FIG. 9( b ) , each of the CBG # 1 , CBG # 2 , and CBG # 3  includes three code blocks. In  FIG. 9( b ) , the CBG # 4  includes two code blocks. In  FIG. 9( b ) , the CBG # 1 , CBG # 2 , and CBG # 3  each include one more code block than the CBG # 4 . In both  FIGS. 9( a ) and 9( b ) , the maximum value of the number of code blocks per CBG may be a value that is one greater than the minimum number of code blocks per CBG. 
     Hereinafter, a HARQ procedure in the MAC layer by the terminal apparatus  1  will be described. As an example of the HARQ procedure in the MAC layer, a case of downlink transmission will be described as an example; however, a part of or the entire HARQ procedure in the MAC layer may be applied to the downlink transmission. 
     A MAC entity may be defined by at least one HARQ entity. The MAC entity may be a main agent (entity) that manages one or multiple HARQ entities. The MAC entity may be a main agent that manages processing of the MAC layer. The HARQ entity may be a main agent (entity) that manages one or multiple HARQ processes. Each of the multiple HARQ processes may be associated with a HARQ process number. The HARQ process number may be an identifier for the HARQ process. The HARQ entity can output HARQ information to the HARQ process. For example, the HARQ entity can output the HARQ information corresponding to a prescribed HARQ process number to a HARQ process associated with the prescribed HARQ process number. The HARQ information includes at least some or all of the new data indicator (NDI), the TBS, the HARQ process number, and the RV. 
     In a case that the spatial multiplexing scheme is configured as a downlink transmission method, input of one or two transport blocks may be expected at each Transmission Time Interval (TTI). In a case that the spatial multiplexing scheme is not configured as the downlink transmission method, input of one transport block may be expected at each TTI. 
     The TTI may be a unit to which the transport block is mapped. The TTI may be given based on the number of OFDM symbols included in at least a slot and/or a subframe. The TTI may be given at least based on a subcarrier spacing applied to a downlink slot. The HARQ process may be configured at each TTI. 
     In a case that downlink allocation is indicated at at least a prescribed TTI, the MAC entity allocates a transport block transferred from the physical layer and HARQ information associated with the transport block to the HARQ process associated with the transport block based on the HARQ information. 
     One or two transport blocks and HARQ information associated with the transport blocks are transferred by the HARQ entity at each TTI at which transmission associated with a prescribed HARQ process occurs. 
     For each of the transport blocks transferred by the HARQ entity and each piece of the HARQ information associated with the transport block, the transmission of the transport block is assumed to be an initial transmission (new transmission) in a case that Condition 1 is at least satisfied in the HARQ process. 
     Condition 1 is a condition in which the new data indicator is toggled (switched) for the most recent transmission. The new data indicator may be included in the HARQ information. The most recent transmission may be a transmission corresponding to the transport block and/or a transmission of a second transport block. The second transport block may be a transport block most recently transmitted. The second transport block may be a transport block corresponding to soft bits stored in a soft buffer of the HARQ process associated with the transport block. The HARQ process number associated with the transport block and the HARQ process number associated with the second transport block may be related to each other. The HARQ process number associated with the transport block and the HARQ process number associated with the second transport block may be the same. 
     In a case that at least Condition 1 is not satisfied and/or a prescribed condition is satisfied, transmission of the transport block is assumed to be a retransmission. 
     In a case that the transmission of the transport block is an initial transmission, the MAC entity may attempt to decode received data. The received data may be received data including the transport block. In a case that the transmission of the transport block is a retransmission and the second transport block has not been successfully decoded, the MAC entity may combine the received data with the soft bits corresponding to the second transport block to generate a third transport block and attempt to decode the third transport block. 
     In a case that Condition 2 is satisfied, the MAC entity may generate an ACK for the transport block. Condition 2 may be a condition in which at least one of Condition 2A and Condition 2B is satisfied. Condition 2A may be a condition in which decoding of the transport block attempted by the MAC entity has been successfully performed. Condition 2B may be a condition in which decoding of the transport block has been previously and successfully completed. 
     In a case that Condition 2 is not satisfied, the MAC entity may replace the data stored in the soft buffer with data that the MAC entity has attempted to decode. In the case that Condition 2 is not satisfied, the MAC entity may replace the soft bits stored in the soft buffer with soft bits generated based on the decoding of the transport block. In the case that Condition 2 is not satisfied, a NACK may be generated for the transport block. 
     Replacing the data stored in the soft buffer with the data that the MAC entity attempted to decode corresponds to flushing (flowing) the data stored in the soft buffer. Replacing the soft bits stored in the soft buffer with soft bits generated based on the decoding of the transport block corresponds to flushing data stored in the soft buffer. 
     For the MAC entity, flushing the soft buffer may correspond flushing soft bits for all bits of a transport block included in the soft buffer. 
     A correspondence relationship between the HARQ-ACK generated for each CBG, the CBG, and the transport block will be described below. The terminal apparatus  1  that has been indicated to feedback a HARQ-ACK for each CBG may generate and feedback a HARQ-ACK corresponding to each of the CBGs included in the transport block. That is, in a case that the HARQ-ACK is fed back for each CBG, the HARQ-ACK for each CBG is generated. In a case that a CBG has been successfully decoded, the HARQ-ACK corresponding to the CBG is generated as an ACK. Successful decoding of the CBG may mean that all code blocks included in the CBG have been successfully decoded. In a case that the CBG has not been successfully decoded, the HARQ-ACK corresponding to the CBG is generated as a NACK. The CBG that has not been successfully decoded may mean that at least one code block included in the CBG has not been successfully decoded. In addition, the present embodiment assumes a case that space bundling is not performed on the HARQ-ACK for the CBG or the HARQ-ACK for the transport block. 
       FIG. 10  is a diagram illustrating an example of the correspondence of HARQ-ACKs (j), CBGs, and transport blocks according to the present embodiment.  FIG. 10( a )  is a diagram illustrating one example of a case that a certain serving cell supports one transport block. Here,  FIG. 10( a )  illustrates a case that the number of CBGs X is configured to 4 by the RRC information. In other words,  FIG. 10( a )  illustrates an example of a case that one transport block includes up to four CBGs. In other words,  FIG. 10( a )  illustrates an example of a case that the number (maximum number) of CBGs X is 4. In  FIG. 10( a ) , a HARQ-ACK ( 0 ) corresponds to a CBG # 1  of a transport block # 0 , a HARQ-ACK ( 1 ) corresponds to a CBG # 2  of the transport block # 0 , a HARQ-ACK ( 2 ) corresponds to a CBG # 3  of the transport block # 0 , and a HARQ-ACK ( 3 ) corresponds to a CBG # 4  of the transport block # 0 . 
       FIG. 10( b )  is a diagram illustrating one example of a case that a certain serving cell supports up to two transport blocks. Here,  FIG. 10( b )  illustrates a case that the number of CBGs X is configured to 4 by the RRC information. In other words,  FIG. 10( b )  illustrates an example of a case that one transport block (each of the transport block # 0  and the transport block # 1 ) includes up to four CBGs. In  FIG. 10( b ) , a HARQ-ACK ( 0 ) corresponds to a CBG # 1  of a transport block # 0 , a HARQ-ACK ( 1 ) corresponds to a CBG # 2  of the transport block # 0 , a HARQ-ACK ( 2 ) corresponds to a CBG # 3  of the transport block # 0 , and a HARQ-ACK ( 3 ) corresponds to a CBG # 4  of the transport block # 0 . A HARQ-ACK ( 4 ) corresponds to a CBG # 1  of a transport block # 1 , a HARQ-ACK ( 5 ) corresponds to a CBG # 1  of a transport block # 2 , a HARQ-ACK ( 6 ) corresponds to a CBG # 3  of the transport block # 1 , and a HARQ-ACK ( 7 ) corresponds to a CBG # 4  of the transport block # 1 . 
     In the present embodiment, in a serving cell in which the HARQ-ACK feedback for each CBG is configured (implemented), the HARQ-ACK corresponding to a PDSCH in a certain slot may be determined at least based on the number of CBGs X indicated by the RRC information and/or the number of transport blocks supported by the serving cell. For example, the number of HARQ-ACKs corresponding to a PDSCH in a certain slot may be the number of CBGs X in a serving cell supporting one transport block. Furthermore, the number of HARQ-ACKs corresponding to a PDSCH in a certain slot may be twice the number of CBGs X in a serving cell supporting two transport blocks. 
     According to the present embodiment, in a serving cell in which the HARQ-ACK feedback for each CBG is configured (implemented), the HARQ-ACK corresponding to a PUSCH in a certain slot may be determined at least based on the number of CBGs X indicated by the RRC information and/or the number of transport blocks supported by the serving cell. For example, the number of HARQ-ACKs corresponding to a PUSCH in a certain slot may be the number of CBGs X in a serving cell supporting one transport block. Furthermore, the number of HARQ-ACKs corresponding to a PUSCH in a certain slot may be twice the number of CBGs X in a serving cell supporting two transport blocks. 
     The number of CBGs X included in the transport block may be individually configured for each of the PUSCH and the PDSCH. 
       FIG. 11  is a diagram illustrating examples of downlink transmission of HARQ-ACKs according to the present embodiment.  FIG. 11( a )  illustrates a case that two serving cells are configured for the terminal apparatus  1 .  FIG. 11( b )  illustrates a case that one serving cell is configured for the terminal apparatus  1 . The indexes (numbers) of transport blocks in the same slot may be # 0  and # 1 . 
       FIG. 11( a )  is a diagram illustrating an example in which the HARQ-ACK corresponding to each of the CBGs included in each of the transport blocks received in a slot  1101  in multiple serving cells configured for the terminal apparatus  1  is transmitted to the base station apparatus  3  on a physical channel (a PUCCH or a PUSCH) in a slot  1104 . In  FIG. 11( a ) , the HARQ-ACK feedback for each CBG is configured in the two serving cells. The base station apparatus  3  transmits a PDSCH  1110  in the primary cell in the slot  1101 . The base station apparatus  3  transmits a PDSCH  1120  in the secondary cell in the slot  1101 . The PDSCH  1110  includes two transport blocks  1111  and  1112 . The PDSCH  1120  includes two transport blocks  1121  and  1122 . In other words, the terminal apparatus  1  receives four transport blocks in the slot  1101 . The terminal apparatus  1  transmits HARQ-ACKs corresponding to the transport blocks  1111 ,  1112 ,  1121 , and  1122  using a PUCCH resource  1180  or a PUSCH resource  1190  in a slot  1104 . 
     Here, the number of CBGs X is indicated to be 4 by the RRC information. The correspondence relationship between the HARQ-ACKs generated, the CBGs and the transport blocks may be illustrated as in  FIG. 12( a ) .  FIG. 12  is a diagram illustrating another example of the correspondence of HARQ-ACKs (j), CBGs, and transport blocks according to the present embodiment. The number of HARQ-ACKs to be generated may be determined at least based on (i) the number of serving cells configured for the terminal apparatus  1 , (ii) the number of transport blocks supported by each of the serving cells, and (iii) the number of CBGs X indicated by the RRC information. 
     For example, in  FIG. 11( a ) , 16 HARQ-ACKs may be generated at least based on 2 which is the number of serving cells configured for the terminal apparatus  1 ,  2  which is the number of transport blocks supported by each of the serving cells, and 4 which is the number of CBGs X indicated by the RRC information. 
     Furthermore, for example, in each of the serving cells, four HARQ-ACKs for the transport block number # 0  and four HARQ-ACKs for the transport block number # 1  may be sequentially linked. Eight HARQ-ACKs for a primary cell (serving cell with a cell index # 0 ) and eight HARQ-ACKs for a secondary cell (serving cell with a cell index # 1 ) may be sequentially linked between the serving cells. Here, according to the present embodiment, a primary cell number (cell index) may be configured to a minimum value. The cell index of the primary cell may be given to be, for example, a cell index # 0 . The cell index of the secondary cell may be, for example, greater than 0. 
     Furthermore, in  FIG. 11( a ) , the two serving cells configured for the terminal apparatus  1  may support up to two transport blocks as described above. The base station apparatus  3  may transmit one transport block in a serving cell in a certain slot. For example, the base station apparatus  3  transmits a PDSCH  1110  in the primary cell in the slot  1101 . The base station apparatus  3  transmits a PDSCH  1120  in the secondary cell in the slot  1101 . The PDSCH  1110  includes one transport block  1111 . The PDSCH  1110  does not include a transport block  1112 . The PDSCH  1120  includes two transport blocks  1121  and  1122 . In other words, the terminal apparatus  1  receives three transport blocks in the slot  1101 . The terminal apparatus  1  transmits the HARQ-ACKs corresponding to the transport blocks  1111 ,  1112 ,  1121 , and  1122  using the PUCCH resource  1180  or the PUSCH resource  1190  in the slot  1104 . At this time, the terminal apparatus  1  generates an ACK or a NACK for each corresponding HARQ-ACK based on whether each of the CBGs included in the received transport blocks  1111 ,  1121 , and  1122  has been successfully decoded. At this time, the terminal apparatus  1  generates the NACK for each of a HARQ-ACK ( 4 ) to a HARQ-ACK ( 7 ) corresponding to the transport block  1112  that has not been received. Here, the base station apparatus  3  may not detect the HARQ-ACK ( 4 ) to the HARQ-ACK ( 7 ) since the base station apparatus  3  already recognizes that the terminal apparatus  1  has generated the NACK to the HARQ-ACK corresponding to each of the CBGs for the transport block  1112  that has not been transmitted to the terminal apparatus  1 . 
     In a case that the terminal apparatus  1  is indicated to transmit, on one PUCCH or one PUSCH, the HARQ-ACK corresponding to the PDSCH received in the slot in multiple serving cells configured, and to feedback the HARQ-ACK for each CBG, the terminal apparatus  1  may generate the ACK or the NACK for the HARQ-ACK corresponding to each of the CBGs included in the received transport block, and may generate the NACK for the HARQ-ACK corresponding to each of the CBGs for the transport block that has not been received. 
       FIG. 11( b )  is a diagram illustrating an example in which the HARQ-ACK corresponding to each of the CBGs included in each of the transport blocks received in multiple slots  1131  and  1132  in one serving cell configured for the terminal apparatus  1  is transmitted to the base station apparatus  3  on the physical channel (the PUCCH or the PUSCH) in a slot  1134 . In  FIG. 11( b ) , the HARQ-ACK feedback for each CBG is configured in one serving cell. The base station apparatus  3  transmits a PDSCH  1140  in the primary cell in a slot  1131 . The base station apparatus  3  transmits a PDSCH  1150  in the primary cell in a slot  1132 . The PDSCH  1140  includes two transport blocks  1141  and  1142 . The PDSCH  1150  includes two transport blocks  1151  and  1152 . The terminal apparatus  1  receives four transport blocks in the slot  1131  and the slot  1132 . The terminal apparatus  1  transmits HARQ-ACKs corresponding to the transport blocks  1141 ,  1142 ,  1151 , and  1152  using a PUCCH resource  1160  or a PUSCH resource  1170  in a slot  1134 . Here, the number of CBGs X may be indicated to be 4 by the RRC information. Furthermore, the correspondence relationships between the HARQ-ACKs generated, the CBGs, and the transport blocks may be illustrated as in  FIG. 12( b ) . The number of generated HARQ-ACKs may be determined at least based on (ii) the number of transport blocks supported by each of the serving cells, (iii) the number of CBGs X indicated by the RRC information, and (iv) the number of slots corresponding to the HARQ-ACK transmitted on the physical channel (the PUCCH or the PUSCH) in the slot  1134 . As for (iv), in  FIG. 11( b ) , for example, the HARQ-ACK for the PDSCH received in the slot  1131  and the slot  1132  is transmitted using the PUCCH resource  1160  or the PUSCH resource  1170  in the slot  1134 . In other words, in  FIG. 11( b ) , the number of slots in which the HARQ-ACK can be transmitted on the physical channel (PUCCH  1160  or PUSCH  1170 ) in the slot  1134  is two. Accordingly, 16 HARQ-ACKs may be generated in  FIG. 11( b ) . Four HARQ-ACKs for a transport block number # 0  and four HARQ-ACKs for transport block number  1  may be sequentially linked. Eight HARQ-ACKs for the slot  1131  and eight HARQ-ACKs for the slot  1132  may be sequentially linked. 
     Furthermore, in  FIG. 11( b ) , the serving cells configured for the terminal apparatus  1  support up to two transport blocks as described above. The base station apparatus  3  may transmit one transport block in a certain slot. For example, the base station apparatus  3  transmits the PDSCH  1140  in the primary cell in the slot  1131 . The base station apparatus  3  transmits the PDSCH  1150  in the slot  1132 . The PDSCH  1140  includes one transport block  1141 . The PDSCH  1140  does not include a transport block  1142 . The PDSCH  1150  includes two transport blocks  1151  and  1152 . In other words, the terminal apparatus  1  receives one transport block in the slot  1131  and receives two transport blocks in the slot  1132 . As in  FIG. 11( a ) , the terminal apparatus  1  generates an ACK or a NACK for each corresponding HARQ-ACK based on whether each of the CBGs included in the received transport block has been successfully decoded. Furthermore, the terminal apparatus  1  generates the NACK for each of a HARQ-ACK ( 4 ) to a HARQ-ACK ( 7 ) for the transport block  1142  that has not been received. Here, the base station apparatus  3  may not detect the HARQ-ACK ( 4 ) to the HARQ-ACK ( 7 ) since the base station apparatus  3  already recognizes that the terminal apparatus  1  has generated the NACK to the HARQ-ACK corresponding to each of the CBGs for the transport block  1142  that has not been transmitted to the terminal apparatus  1 . 
     That is, in a case that the terminal apparatus  1  is indicated to transmit, on the same PUCCH or PUSCH in the same slot, the HARQ-ACK corresponding to each PDSCH received in multiple slots in one cell, and to feedback the HARQ-ACK for each CBG, the terminal apparatus  1  may generate an ACK or a NACK for the HARQ-ACK corresponding to each of the CBGs included in the transport block received in the PDSCH and may generate the NACK for the HARQ-ACK corresponding to each of the CBGs for the transport block that has not been received. 
       FIG. 11( c )  is a diagram illustrating an example in which the HARQ-ACK corresponding to each of the CBGs included in each of the transport blocks received in multiple slots in multiple serving cells configured for the terminal apparatus  1  is transmitted to the base station apparatus  3  on the same physical channel (PUCCH or PUSCH) in the same slot. In  FIG. 11( c ) , the HARQ-ACK feedback for each CBG is configured in two serving cells. Subcarrier spacings between servings are different. A subcarrier spacing for the primary cell is twice a subcarrier spacing for the secondary cell. That is, a slot length of the primary cell is half a slot length of the secondary cell. In  FIG. 11( c ) , the terminal apparatus  1  receives a PDSCH  1180  in a slot  1171  and a PDSCH  1183  in a slot  1172  in the primary cell. The PDSCH  1110  includes two transport blocks  1111  and  1112 . The PDSCH  1180  includes two transport blocks  1181  and  1182 . The terminal apparatus  1  receives a PDSCH  1195  in a slot  1191  in the secondary cell. The PDSCH  1195  includes two transport blocks  1196  and  1197 . Next, the terminal apparatus  1  transmits HARQ-ACKs corresponding to the six received transport blocks using a PUCCH  1186  or PUSCH  1187  in a slot  1174 . In this case, the correspondence relationship between the HARQ-ACKs generated, the CBGs, and the transport blocks may be illustrated as in  FIG. 12( c ) . 
     Further, according to the present embodiment,  FIGS. 11( a ), 11( b ), and 11( c )  may be configured for the terminal apparatus  1  at the same time. In other words, the terminal apparatus  1  may transmit the HACK-ACK corresponding to each of the PDSCHs received in one or multiple slots in one or multiple serving cells on the same PUCCH or PUSCH in the same slot. Here, in a case that the terminal apparatus  1  is indicated to feedback the HARQ-ACK for each CBG, the terminal apparatus  1  may generate an ACK or a NACK for the HARQ-ACK corresponding to each of the CBGs included in the received transport block on the PDSCH, and generate the NACK for the HARQ-ACK corresponding to each of the CBGs for the transport block that has not been received. The number of generated HARQ-ACKs may be determined at least based on (i) the number of serving cells configured for the terminal apparatus  1 , (ii) the number of transport blocks supported by each of the serving cells, (iii) the number of CBGs X indicated by the RRC information, and (iv) the number of slots corresponding to the HARQ-ACKs that can be transmitted on the same physical channel PUCCH or PUSCH in the same slot. 
       FIG. 13  is a diagram illustrating an example in which HARQ-ACKs corresponding to a transport block are transmitted according to the present embodiment. Here, the transport block may correspond to any one of the transport blocks in  FIG. 11 . In  FIG. 13 , the number of CBGs X is given to be 4 by the RRC information. 
     (S 1310 ) The base station apparatus  3  performs initial transmission of a certain transport block  1301  to the terminal apparatus  1 . The terminal apparatus  1  performs demodulation processing, decoding processing, and the like of the transport block  1301  received. In a case that the transmission of the transport block  1301  is an initial transmission, the terminal apparatus  1  may determine the number of code blocks N CB  included in the transport block based on the transport block size. Here, the transport block size may be given by downlink control information. Here, N CB  is 3. That is, the transport block  1301  initially transmitted includes three code blocks. In  FIG. 13 , the number of code blocks included in the initial transmission of the transport block is smaller than the number of CBGs X. In  FIG. 13 , each of a CBG # 1 , a CBG # 2 , and a CBG # 3  includes one code block. In  FIG. 13 , a CBG # 4  includes no code block. 
     Next, the terminal apparatus  1  may attempt to decode the transport block  1301  received. Then, the terminal apparatus  1  may generate a HARQ-ACK  1303  for the initial transmission of the transport block  1301 . Since the HARQ-ACK  1303  includes a HARQ-ACK generated for each of the CBGs, the terminal apparatus  1  performs the demodulation processing, the decoding processing, and the like on each of the CBGs. The terminal apparatus  1  may perform the demodulation processing, the decoding processing, and the like on the code block included in each of the CBGs. Since the terminal apparatus  1  recognizes that the CBG # 4  includes no code block based on the size of the transport block  1301 , none of the demodulation processing, the decoding processing, and the like may be performed on the CBG # 4 . 
     For the HARQ-ACK for the CBG including the code block, an ACK or a NACK may be generated based on whether the CBG has been successfully decoded. For each of the HARQ-ACKs for the CBG # 1 , CBG # 2 , and CBG # 3 , the ACK or the NACK is generated based on whether each of the CBGs has been successfully decoded. The terminal apparatus  1  may generate the HARQ-ACK for the CBG based on whether the CBG has been successfully decoded. In a case that the CBG has been successfully decoded, the terminal apparatus  1  may generate the ACK for the CBG. In a case that the CBG has not been successfully decoded, the terminal apparatus  1  may generate the NACK for the CBG. Furthermore, the terminal apparatus  1  may generate the NACK as a HARQ-ACK for the CBG # 4  including no code block. Furthermore, the terminal apparatus  1  may generate the ACK as a HARQ-ACK for the CBG # 4  including no code block. 
     That is, in a case that the number of code blocks N CB  is less than the number of CBGs X, each of the N CB  code blocks is included in N CB  different CBGs, and N CB  HARQ-ACKs corresponding to the N CB  CBGs and (X-N CB ) NACKs are generated as HARQ-ACKs for the initial transmission of the transport block. That is, in a case that the number of code blocks N CB  is less than the number of CBGs X, the HARQ-ACKs for the initial transmission of the transport block include the (X-N CB ) NACKs and N CB  HARQ-ACKs for the N CB  CBGs. For each of the N CB  HARQ-ACKs corresponding to the N CB  CBGs, an ACK or a NACK may be generated based on whether the CBG has been successfully decoded. Furthermore, here, N CB  HARQ-ACKs corresponding to the N CB  CBGs and (X-N CB ) ACKs may be generated for the HARQ-ACKs for the initial transmission of the transport block. 
     The HARQ-ACKs for the transport block may include X-N CB  NACKs and N CB  HARQ-ACKs corresponding to the N CB  CBGs in a case that the number of code blocks N CB  included in the transport block is less than the maximum number of CBGs X. The number of code blocks N CB  may be given at least based on the transport block size. Each of the N CB  code blocks may be included in N CB  different CBGs. Transmission of the transport block may be an initial transmission. The X-N CB  NACKs may be X-N CB  ACKs. Here, for each of the N CB  HARQ-ACKs corresponding to the N CB  CBGs, an ACK or a NACK may be generated based on whether the CBG has been successfully decoded. 
     The HARQ-ACKs for the transport block may include X HARQ-ACKs for the X CBGs in a case that the number of code blocks N CB  included in the transport block is equal to or greater than the maximum number of CBGs X. Here, for each of the X HARQ-ACKs corresponding to the X CBGs, an ACK or a NACK may be generated based on whether the CBG has been successfully decoded. 
     (S 1320 ) The terminal apparatus  1  transmits the HARQ-ACK  1303  for the initial transmission of the transport block  1301  to the base station apparatus  3 . The base station apparatus  3  determines, based on the HARQ-ACK  1303  received from the terminal apparatus  1 , for which CBG retransmission is to be performed. Here, the base station apparatus  3  may not detect the HARQ-ACK ( 3 ) since it recognizes that the NACK has been generated for the CBG # 4  that includes no code block. 
     (S 1330 ) The base station apparatus  3  retransmits a CBG for a certain transport block  1301  to the terminal apparatus  1 . The base station apparatus  3  notifies the terminal apparatus  1  of which CBG among the CBG # 1 , the CGB # 2 , and the CBG # 3  is to be actually retransmitted based on information indicating transmission of the CBG (e.g., the field of CBG indication). The retransmission of the CBG may mean that the code block included in the CBG is to be retransmitted. The terminal apparatus  1  can determine the CBG to be actually retransmitted based on the information indicating the transmission of the CBG. The field of CBG indication indicating the transmission of the CBG may be a 4-bit bitmap. For example, the base station apparatus  3  sets the field of CBG indication to ‘0110’ and notifies the terminal apparatus  1  of retransmission of the CBG # 2  and the CBG # 3 . In other words, the number of CBGs to be retransmitted Y in S 1330  is 2. Here, the CBG # 2  and the CBG # 3  to be retransmitted constitutes a part of the transport block initially transmitted (the CBG # 1 , the CBG # 2 , and the CBG # 3 ). That is, the code blocks included in the retransmitted CBGs constitutes a part of the transport block  1301  for initial transmission. The number of CBGs to be retransmitted Y may be given by the information indicating the transmission of the CBG included in a PDCCH. 
     Next, the terminal apparatus  1  may attempt to decode the retransmission of the CBG of the received transport block  1301 . Then, the terminal apparatus  1  may generate a HARQ-ACK  1305  for the retransmission of the CBG of the transport block  1301 . In the retransmission of the transport block, the HARQ-ACK  1305  is a HARQ-ACK for the transport block. The HARQ-ACK  1305  is a HARQ-ACK generated for each CBG. The terminal apparatus  1  may perform the demodulation processing, the decoding processing, or the like on the code block included in each of the retransmitted CBG # 2  and CBG # 3  based on the information indicating the transmission of the CBG. 
     In S 1340 , for each of the HARQ-ACKs for the CBG # 2  and the CBG # 3  including the code block, an ACK or a NACK may be generated based on whether the CBG has been successfully decoded. In a case that the CBG has been successfully decoded, the terminal apparatus  1  may generate the ACK for the CBG. In a case that the CBG has not been successfully decoded, the terminal apparatus  1  may generate the NACK for the CBG. In S 1340 , the terminal apparatus  1  generates the NACK as a HARQ-ACK for the CBG # 1  that includes the code block but has not been retransmitted. Furthermore, in S 1340 , the terminal apparatus  1  generates the NACK as a HARQ-ACK for the CBG # 4  including no code block. In other words, in S 1340 , the terminal apparatus  1  may generate ACKs as HARQ-ACKs for the CBG # 1  and the CBG # 4 . 
     In other words, in a case that the number of CBGs to be retransmitted Y is less than the number (maximum number) of CBGs X, for the HARQ-ACKs for retransmission of the transport block, (X-Y) NACKs and Y HARQ-ACKs corresponding to the Y CBGs are generated. That is, the HARQ-ACKs for retransmission of the transport block includes (X-Y) NACKs and Y HARQ-ACKs corresponding to the Y CBGs. An ACK or a NACK may be generated for each of the Y HARQ-ACKs corresponding to the Y CBGs based on whether the CBG has been successfully decoded. Further, here, in a case that the number of CBGs to be retransmitted Y is less than the number of CBGs X, for the HARQ-ACKs for retransmission of the transport block, Y HARQ-ACKs corresponding to the Y CBGs and (X-Y) ACKs may be generated. Here, the number of CBGs to be retransmitted Y is determined based on the information indicating the transmission of the CBG included in the PDCCH, and the number (maximum number) of CBGs X is indicated by the RRC information. 
     The HARQ-ACKs for the transport block may include (X-Y) NACKs and Y HARQ-ACKs for the Y CBGs in a case that the number of CBGs to be retransmitted Y is less than the number of CBGs X. The number of CBGs to be retransmitted Y may be determined based on the information indicating the transmission of the CBG included in the PDCCH. The maximum number of CBGs X may be indicated by the RRC information. 
     The HARQ-ACKs for the transport block may also include X HARQ-ACKs for X CBGs in a case that the number of CBGs to be retransmitted Y is equal to the number of CBGs X. 
     In the initial transmission of the transport block in S 1310 , the HARQ-ACKs for the transport block may include X HARQ-ACKs for the X CBGs in a case that the number of code blocks N CB  included in the transport block is equal to or greater than the maximum number of CBGs X. Further, in the retransmission of the transport block in S 1330 , in a case that the number of CBGs to be retransmitted Y is less than the number of CBGs X, the HARQ-ACKs for the transport block may include (X-Y) NACKs and Y HARQ-ACKs for the Y CBGs. Furthermore, in the retransmission of the transport block, the HARQ-ACKs for the transport block may include X HARQ-ACKs in a case that the number of CBGs to be retransmitted Y is equal to the number of CBGs X. 
     In addition, in S 1340 , the terminal apparatus  1  may generate a HARQ-ACK  1306  instead of generating the HARQ-ACK  1305 . The HARQ-ACK  1306  is a HARQ-ACK for the retransmission of the CBG of the transport block  1301 . The HARQ-ACK  1306  is a HARQ-ACK for the transport block in the retransmission of the transport block. The HARQ-ACK  1306  is a HARQ-ACK generated for each CBG. 
     In the HARQ-ACK  1305  of S 1340 , the number of HARQ-ACKs Y based on the decoding of the CBGs is given by the information indicating the transmission of the CBG. Namely, in the HARQ-ACK  1305 , HARQ-ACKs corresponding to the actually retransmitted CBGs are given based on the result of decoding the CBGs (an ACK or a NACK). Furthermore, in the HARQ-ACK  1305  of S 1340 , the terminal apparatus  1  generates NACKs for all CBGs of which retransmissions are not indicated. In other words, in the HARQ-ACK  1305  of S 1340 , for a HARQ-ACK ( 0 ) corresponding to the CBG # 1 , the NACK is generated regardless of the result of decoding the CBG # 1  (the ACK or the NACK) transmitted immediately before in S 1310  and a NACK is generated. 
     In the HARQ-ACK  1306  of S 1340 , the HARQ-ACK for the CBG including a code block is given based on the result of the decoding CBG data most recently received (the ACK or the NACK). In the HARQ-ACK  1306  of S 1340 , the NACK may be generated as a HARQ-ACK for the CBG including no code block. Here, the number of HARQ-ACKs based on the result of decoding the received CBG data may be the number of CBGs that include the code block at the time of the initial transmission. 
     That is, in the retransmission of the transport block, the HARQ-ACK for the CBG of which transmission is not indicated by the information indicating the transmission of the CBG may be given based on whether the decoding of the CBG has already been successfully completed. 
     That is, in S 1340 , the HARQ-ACK for the CBG # 1  of which transmission is not indicated by the information indicating the transmission of the CBG may be given based on whether the decoding of the CBG # 1  has already been successfully completed. Also, in S 1340 , the NACK may be generated as a HARQ-ACK for the CBG # 4  regardless of whether the CBG # 4  including no code block has successfully been successfully decoded. 
     In a case that no code block is included in the CBG of which transmission is not indicated by the information indicating the transmission of the CBG, the decoding of the CBG may be considered not to have been completed. 
     In the CBG retransmission  1304  of the transport block  1301 , even in a case that the CBG # 1  is not retransmitted, the HARQ-ACK for the CBG # 1  may be given based on the result of decoding the data of the CBG # 1  most recently received (the ACK or the NACK). Here, the data of the CBG # 1  most recently received is transmitted in the initial transmission  1302  of the transport block  1301 . Namely, the HARQ-ACK ( 0 ) in  1303  and the HARQ-ACK ( 0 ) in  1306  may be the same. For example, in a case that the HARQ-ACK ( 0 ) for the CBG # 1  is an ACK in  1303 , an ACK may be generated for the HARQ-ACK ( 0 ) in  1306 . Also, for example, in a case that the HARQ-ACK ( 0 ) for the CBG # 1  is a NACK in  1303 , a NACK may be generated for the HARQ-ACK ( 0 ) in  1306 . 
     Furthermore, in the CBG retransmission  1304  of the transport block  1301 , the HARQ-ACK for the CBG # 2  of which retransmission is indicated may be given based on the result of decoding the CBG # 2  (the ACK or the NACK). Here, the result of decoding the CBG # 2  is determined at least based on the CBG # 2  transmitted in the initial transmission  1302  of the transport block  1301  and the CBG # 2  transmitted in the CBG retransmission  1304  of the transport block  1301 . 
     Furthermore, in the CBG retransmission  1304  of the transport block  1301 , the HARQ-ACK for the CBG # 3  of which retransmission is indicated may be given based on the result of decoding the CBG # 3  (the ACK or the NACK). Here, the result of decoding the CBG # 3  is determined at least based on the CBG # 3  transmitted in the initial transmission  1302  of the transport block  1301  and the CBG # 3  transmitted in the CBG retransmission  1304  of the transport block  1301 . 
     Furthermore, in the CBG retransmission  1304  of the transport block  1301 , the terminal apparatus  1  generates the NACK as a HARQ-ACK for the CBG # 4  including no code block. 
     In other words, in the CBG retransmission (adaptive retransmission) of the transport block, the number of code blocks N CB  included in the transport block for initial transmission is given by the transport block size for the initial transmission, and the number (maximum number) of CBGs X is indicated by the RRC information. In a case that the number of code blocks N CB  is less than the number of CBGs X, (X-N CB ) NACKs and N CB  HARQ-ACKs corresponding to N CB  CBGs are generated as HARQ-ACKs for retransmission of the transport block. Namely, the HARQ-ACKs for retransmission of the transport block include (X-N CB ) NACKs and N CB  HARQ-ACKs corresponding to N CB  CBGs. For each of the N CB  HARQ-ACKs corresponding to the N CB  CBGs, an ACK or a NACK may be generated based on whether data of the CBG most recently received has been successfully decoded. The data of the CBG most recently received includes CBG data of the initial transmission and/or CBG data of the CBG retransmission. Furthermore, here, in the CBG retransmission (adaptive retransmission) of the transport block, the number of code blocks N CB  included in the transport block for initial transmission is given by the transport block size for the initial transmission, and the number (maximum number) of CBGs X is indicated by the RRC information. In a case that, the number of code blocks N CB  is less than the number of CBGs X, N CB  HARQ-ACKs corresponding to N CB  CBGs and (X-N CB ) NACKs may be generated for the HARQ-ACKs for the retransmission of the transport block. 
     The HARQ-ACKs for the transport block may include X-N CB  NACKs and N CB  HARQ-ACKs corresponding to the N CB  CBGs in a case that the number of code blocks N CB  included in the transport block is less than the maximum number of CBGs X. The number of code blocks N CB  may be given at least based on the transport block size. Each of the N CB  code blocks may be included in N CB  different CBGs. Transmission of the transport block may be an initial transmission. The X-N CB  NACKs may be ACKs. 
     Furthermore, the HARQ-ACKs for the transport block may include X HARQ-ACKs regardless of the number of CBGs to be retransmitted Y in a case that the number of code blocks N CB  included in the transport block is equal to or greater than the maximum number of CBGs X. 
     In addition, according to the present embodiment, the above-described two HARQ-ACK generation schemes for the CBG retransmission of the transport block may be applied even in a case that the number of code blocks N CB  given based on the TBS of the initial transmission of the transport block is greater than the number of CBGs X. 
     In S 1330 , in the retransmission of the transport block, the number of code blocks N CB  may be given based on the transport block size of the initial transmission. 
     In addition, in the retransmission of the transport block in S 1330 , in a case that the number of code blocks N CB  included in the transport block is equal to or greater than the maximum number of CBGs X, the HARQ-ACK for the transport block may include X HARQ-ACKs corresponding to X CBGs. 
     (S 1340 ) The terminal apparatus  1  transmits, to the base station apparatus  3 , either the HARQ-ACK  1305  or the HARQ-ACK  1306  for the CBG retransmission of the transport block  1301 . The transmission of either the HARQ-ACK  1305  or the HARQ-ACK  1306  may be determined based on higher layer signaling and/or description of a specification, or the like. The base station apparatus  3  determines whether to perform retransmission for any CBG based on the HARQ-ACK  1305  or the HARQ-ACK  1306  transmitted from the terminal apparatus  1 . 
       FIG. 14  is a diagram illustrating an example of encoding a HARQ-ACK generated for each CBG to binary bits according to the present embodiment. In  FIG. 14 , the number (maximum number) of CBGs X is indicated by the RRC information and may be  4 . Namely, indexes # 1 , # 2 , # 3 , and # 4  are given to four CBGs respectively. 
     In the present embodiment, the HARQ-ACK is set to an ACK or a NACK. The terminal apparatus  1  encodes HARQ-ACK bits into binary bits. The terminal apparatus  1  encodes the ACK as a binary “1” and encodes the NACK as a binary “0”. The terminal apparatus  1  encodes the HARQ-ACK bits generated for each CBG into binary bits. 
     The terminal apparatus  1  may determine the number of code blocks N CB  included in the transport block based on the transport block size for initial transmission. In a case that the number of code blocks N CB  determined by the transport block size is less than the number of CBGs X indicated by the RRC information, a binary bit of the HARQ-ACK corresponding to a CBG with an index greater than N CB  may be set to a prescribed value. For example, the prescribed value may be 0 or 1. 
     For example, N CB  is given to be 3 based on the transport block size. The binary bit of the HARQ-ACK corresponding to the index CBG # 4  greater than 3 that is the number of code blocks may be set to a prescribed value. Namely, a binary bit b( 3 ) of a HARQ-ACK ( 3 ) corresponding to the CBG # 4  may be set to the prescribed value. Furthermore, for example, N CB  is given to be 2 based on the transport block size. The binary bit of the HARQ-ACK corresponding to each of the indexes CBG # 3  and CBG # 4  greater than 2 that is the number of code blocks may be set to a prescribed value. Namely, each of b( 2 ) and b( 3 ) may be set to the prescribed value. In this way, the base station apparatus  3  can enhance tolerance of the overall HARQ-ACK binary bits to burst errors since the terminal apparatus  1  recognizes in advance that the binary bit of the HARQ-ACK corresponding to the CBG with an index greater than N CB  is to be set to a prescribed value. 
     In  FIG. 11 , since the RRC parameter cbgTransmission is configured for each of the primary cell and the secondary cell, the terminal apparatus  1  generates a HARQ-ACK for each CBG in the primary cell and the secondary cell (i.e., each of the serving cells). As described above, in the serving cell in which the RRC parameter cbgTransmission is configured, the downlink control information may indicate generation of the HARQ-ACK for each transport block. For example, in the slot  1101 , the base station apparatus  3  transmits the PDSCH  1120  in the secondary cell and causes the PDSCH  1120  to indicate the HARQ-ACK for each transport block. In this case, the correspondence relationships between the HARQ-ACKs generated, the CBGs, and the transport blocks may be illustrated as in  FIG. 15( a ) .  FIG. 15  is a diagram illustrating another example of the correspondence relationships of the HARQ-ACKs (j), the CBGs, and transport blocks according to the present embodiment. At this time, in the secondary cell, a HARQ-ACK ( 8 ) corresponds to a transport block  1121  included in the PDSCH  1120 , and a HARQ-ACK ( 12 ) corresponds to a transport block  1122  included in the PDSCH  1120 . In other words, for the HARQ-ACK ( 8 ), an ACK or a NACK may be generated based on whether the transport block  1121  has been successfully decoded. For the HARQ-ACK ( 12 ), an ACK or a NACK may be generated based on whether the transport block  1122  has been successfully decoded. The terminal apparatus  1  generates a NACK for a HARQ-ACK ( 9 ), a HARQ-ACK ( 10 ), a HARQ-ACK ( 11 ), a HARQ-ACK ( 13 ), a HARQ-ACK ( 14 ), and a HARQ-ACK ( 15 ). 
     Namely, in the serving cell in which the RRC parameter cbgTransmission is configured, in a case that the serving cell supports one transport block and indicates generation of a HARQ-ACK for each transport block using the PDCCH, the terminal apparatus  1  may generate a prescribed number of NACKs. Here, the prescribed number may be X−1. For one HARQ-ACK, an ACK or a NACK may be generated based on whether the received transport block has been successfully decoded. In other words, the HARQ-ACKs for the transport block may include X−1 NACKs and one HARQ-ACK corresponding to one transport block. The terminal apparatus  1  encodes an ACK as a binary “1” and encodes a NACK as a binary “0”. Namely, in the serving cell in which the RRC parameter cbgTransmission is configured, in a case that the number of CBGs X for the serving cell is indicated by the RRC information, and the serving cell supports one transport block and indicates generation of a HARQ-ACK for each transport block using the PDCCH, the terminal apparatus  1  may generate a prescribed number of binary “0s”. Here, the prescribed number may be X−1. 
     Furthermore, in the serving cell in which the RRC parameter cbgTransmission is configured, in a case that the serving cell supports two transport blocks, two transport blocks on the PDSCH of a certain slot is received, and generation of a HARQ-ACK for each transport block is indicated using the PDCCH, the terminal apparatus  1  may generate a prescribed number of NACKs. Here, the prescribed number may be 2(X−1). For each of the two HARQ-ACKs, an ACK or a NACK may be generated based on whether each of the transport blocks received has been successfully decoded. Namely, HARQ-ACKs corresponding to the PDSCH may include 2(X−1) NACKs and two HARQ-ACKs corresponding to the two transport blocks. The terminal apparatus  1  encodes an ACK as a binary “1” and encodes a NACK as a binary “0”. Namely, in the serving cell in which the RRC parameter cbgTransmission is configured, in a case that the serving cell supports the two transport blocks, the two transport blocks are received on the PDSCH of a certain slot, and generation of a HARQ-ACK for each of the transport blocks is indicated using the PDCCH, the terminal apparatus  1  may generate a prescribed number of binary “0s”. Here, the prescribed number may be 2(X−1). 
     Furthermore, in the serving cell in which the RRC parameter cbgTransmission is configured, in a case that the serving cell supports the two transport blocks, only one transport block is received on the PDSCH of a certain slot, and generation of a HARQ-ACK for each transport block is indicated using the PDCCH, the terminal apparatus  1  may generate a prescribed number of NACKs. Here, the prescribed number may be 2X−1. For one HARQ-ACK, an ACK or a NACK may be generated based on whether the received transport block has been successfully decoded. Namely, the HARQ-ACKs corresponding to the PDSCH may include 2X−1 NACKs and one HARQ-ACK corresponding to the one transport block received. The terminal apparatus  1  encodes an ACK as a binary “1” and encodes a NACK as a binary “0”. Namely, in the serving cell in which the RRC parameter cbgTransmission is configured, in a case that the serving cell supports the two transport blocks, only one transport block is received on the PDSCH of a certain slot, and generation of a HARQ-ACK for each of the transport blocks is indicated using the PDCCH, the terminal apparatus  1  may generate a prescribed number of binary “0”. Here, the prescribed number may be 2X−1. 
     Furthermore, for example, the secondary cell configured for the terminal apparatus  1  is not configured in the RRC parameter cbgTransmission in  FIG. 11 . Namely, a HARQ-ACK corresponding to the PDSCH in the secondary cell is generated for each transport block. In this case, the correspondence relationships between the HARQ-ACKs generated, the CBGs, and the transport blocks may be illustrated as in  FIG. 15( b ) . In the primary cell, the HARQ-ACK is generated for each of CBGs. In the secondary cell, the HARQ-ACK ( 8 ) corresponds to the transport block  1121  included in the PDSCH  1120 , and the HARQ-ACK ( 9 ) corresponds to the transport block  1122  included in the PDSCH  1120 . In other words, for the HARQ-ACK ( 8 ), an ACK or a NACK may be generated based on whether the transport block  1121  has been successfully decoded. For the HARQ-ACK ( 9 ), an ACK or a NACK may be generated based on whether the transport block  1122  has been successfully decoded. 
     A configuration of the terminal apparatus  1  of the present invention will be described below. 
       FIG. 16  is a schematic block diagram illustrating a configuration of the terminal apparatus  1  according to the present embodiment. As illustrated, the terminal apparatus  1  is configured to include at least one of a higher layer processing unit  101 , a controller  103 , a receiver  105 , a transmitter  107 , and a transmit and receive antenna  109 . The higher layer processing unit  101  is configured to include at least one of a radio resource control unit  1011  and a scheduling unit  1013 . The receiver  105  is configured to include at least one of a decoding unit  1051 , a demodulation unit  1053 , a demultiplexing unit  1055 , a radio receiving unit  1057 , and a channel measurement unit  1059 . The transmitter  107  is configured to include at least one of a coding unit  1071 , a shared channel generation unit  1073 , a control channel generation unit  1075 , a multiplexing unit  1077 , a radio transmitting unit  1079 , and an uplink reference signal generation unit  10711 . 
     The higher layer processing unit  101  outputs uplink data generated through a user operation or the like to the transmitter  107 . The higher layer processing unit  101  performs processing of the Medium Access Control (MAC) layer, the Packet Data Convergence Protocol (PDCP) layer, the Radio Link Control (RLC) layer, and the Radio Resource Control (RRC) layer. Furthermore, the higher layer processing unit  101  generates control information for control of the receiver  105  and the transmitter  107  based on downlink control information or the like received on a control channel and outputs the generated control information to the controller  103 . 
     The radio resource control unit  1011  included in the higher layer processing unit  101  manages various kinds of configuration information of the terminal apparatus  1 . For example, the radio resource control unit  1011  manages a configured serving cell. Furthermore, the radio resource control unit  1011  generates information to be mapped to each uplink channel, and outputs the generated information to the transmitter  107 . In a case that the received downlink data is successfully decoded, the radio resource control unit  1011  generates an ACK and outputs the ACK to the transmitter  107 , and in a case that decoding of the received downlink data is failed, the radio resource control unit  1011  generates a NACK and outputs the NACK to the transmitter  107 . 
     The scheduling unit  1013  included in the higher layer processing unit  101  stores downlink control information received via the receiver  105 . The scheduling unit  1013  controls the transmitter  107  via the controller  103  so as to transmit a PUSCH according to a received uplink grant in the fourth subsequent subframe from the subframe in which the uplink grant has been received. The scheduling unit  1013  controls the receiver  105  via the controller  103  so as to receive a shared channel according to a received downlink grant in the subframe in which the downlink grant has been received. 
     The controller  103  generates a control signal for control of the receiver  105  and the transmitter  107  based on the control information from the higher layer processing unit  101 . The controller  103  outputs the generated control signal to the receiver  105  and the transmitter  107  to control the receiver  105  and the transmitter  107 . 
     In accordance with the control signal input from the controller  103 , the receiver  105  demultiplexes, demodulates, and decodes a reception signal received from the base station apparatus  3  through the transmit and receive antenna  109 , and outputs information resulting from the decoding to the higher layer processing unit  101 . 
     The radio receiving unit  1057  orthogonally demodulates a downlink signal received via the transmit and receive antenna  109 , and converts the orthogonally-demodulated analog signal to a digital signal. The radio receiving unit  1057 , for example, may perform Fast Fourier Transform (FFT) on the digital signal and extract a signal of the frequency domain. 
     The demultiplexing unit  1055  demultiplexes the extracted signals into a control channel, a shared channel, and a reference signal channel, respectively. The demultiplexing unit  1055  outputs the separated reference signal channel to the channel measurement unit  1059 . 
     The demodulation unit  1053  demodulates the control channel and the shared channel by using a modulation scheme such as QPSK, 16 Quadrature Amplitude Modulation (QAM), 64 QAM, and the like, and outputs the result of the demodulation to the decoding unit  1051 . 
     The decoding unit  1051  decodes the downlink data and outputs, to the higher layer processing unit  101 , the decoded downlink data. The channel measurement unit  1059  calculates a downlink channel estimate from the reference signal channel and outputs the calculation result to the demultiplexing unit  1055 . The channel measurement unit  1059  calculates channel state information and outputs the channel state information to the higher layer processing unit  101 . 
     The transmitter  107  generates an uplink reference signal channel in accordance with the control signal input from the controller  103 , encodes and modulates the uplink data and uplink control information input from the higher layer processing unit  101 , multiplexes the shared channel, the control channel, and the reference signal channel, and transmits a signal resulting from the multiplexing to the base station apparatus  3  through the transmit and receive antenna  109 . 
     The coding unit  1071  encodes the uplink control information and uplink data input from the higher layer processing unit  101  and outputs the coded bits to the shared channel generation unit  1073  and/or the control channel generation unit  1075 . 
     The shared channel generation unit  1073  may modulate the coded bits input from the coding unit  1071  to generate a modulation symbol, generate the shared channel by performing DFT on the modulation symbol and output the shared channel to the multiplexing unit  1077 . The shared channel generation unit  1073  may modulate the coded bits input from the coding unit  1071  to generate a shared channel and output the shared channel to the multiplexing unit  1077 . 
     The control channel generation unit  1075  generates a control channel based on the coded bits input from the coding unit  1071  and/or SR and outputs the generated control channel to the multiplexing unit  1077 . 
     The uplink reference signal generation unit  10711  generates an uplink reference signal and outputs the generated uplink reference signal to the multiplexing unit  1077 . 
     The multiplexing unit  1077  multiplexes a signal input from the shared channel generation unit  1073  and/or a signal input from the control channel generation unit  1075  and/or the uplink reference signal input from the uplink reference signal generation unit  10711  into an uplink resource element for each transmit antenna port according to the control signal input from the controller  103 . 
     The radio transmitting unit  1079  performs inverse fast Fourier transform (IFFT) on the multiplexed signal, generates a baseband digital signal, converts the baseband digital signal into an analog signal, generates an in-phase component and an orthogonal component of an intermediate frequency from the analog signal, removes frequency components unnecessary for the intermediate frequency band, converts (up-converts) the signal of the intermediate frequency into a signal of a high frequency, removes unnecessary frequency components, performs power amplification, and outputs a final result to the transmit and receive antenna  109  for transmission. 
     A configuration of the base station apparatus  3  of the present invention will be described below. 
       FIG. 17  is a schematic block diagram illustrating a configuration of the base station apparatus  3  according to the present embodiment. As is illustrated, the base station apparatus  3  is configured to include a higher layer processing unit  301 , a controller  303 , a receiver  305 , a transmitter  307 , and a transmit and receive antenna  309 . Furthermore, the higher layer processing unit  301  is configured to include a radio resource control unit  3011  and a scheduling unit  3013 . Furthermore, the receiver  305  is configured to include a data demodulation/decoding unit  3051 , a control information demodulation/decoding unit  3053 , a demultiplexing unit  3055 , a radio receiving unit  3057 , and a channel measurement unit  3059 . The transmitter  307  is configured to include a coding unit  3071 , a modulation unit  3073 , a multiplexing unit  3075 , a radio transmitting unit  3077 , and a downlink reference signal generation unit  3079 . 
     The higher layer processing unit  301  performs processing of the Medium Access Control (MAC) layer, the Packet Data Convergence Protocol (PDCP) layer, the Radio Link Control (RLC) layer, and the Radio Resource Control (RRC) layer. Furthermore, the higher layer processing unit  301  generates control information for control of the receiver  305  and the transmitter  307 , and outputs the generated control information to the controller  303 . 
     The radio resource control unit  3011  included in the higher layer processing unit  301  generates or acquires from a higher node, downlink data mapped to a shared channel of downlink, RRC signaling, and a MAC control element (CE), and outputs the downlink data, the RRC signaling, and the MAC CE to the a HARQ controller  3013 . Furthermore, the radio resource control unit  3011  manages various configuration information for each of the terminal apparatuses  1 . For example, the radio resource control unit  3011  manages a serving cell configured for the terminal apparatus  1 , and the like. 
     The scheduling unit  3013  included in the higher layer processing unit  301  manages radio resources of shared channels and control channels allocated to the terminal apparatus  1 . In a case that a radio resource of the shared channel is allocated to the terminal apparatus  1 , the scheduling unit  3013  generates an uplink grant indicating the allocation of the radio resource of the shared channel and outputs the generated uplink grant to the transmitter  307 . 
     The controller  303  generates a control signal for controlling the receiver  305  and the transmitter  307  based on the control information from the higher layer processing unit  301 . The controller  303  outputs the generated control signal to the receiver  305  and the transmitter  307  to control the receiver  305  and the transmitter  307 . 
     In accordance with the control signal input from the controller  303 , the receiver  305  demultiplexes, demodulates, and decodes a reception signal received from the terminal apparatus  1  through the transmit and receive antenna  309 , and outputs information resulting from the decoding to the higher layer processing unit  301 . 
     The radio receiving unit  3057  orthogonally demodulates the uplink signal received via the transmit and receive antenna  309  and converts the orthogonally-demodulated analog signal into a digital signal. The radio receiving unit  3057  performs Fast Fourier Transform (FFT) on the digital signal, extracts a signal of the frequency domain, and outputs the resulting signal to the demultiplexing unit  3055 . 
     The demultiplexing unit  1055  demultiplexes the signal input from the radio receiving unit  3057  into signals of the control channel, the shared channel, the reference signal channel, and the like. The demultiplexing is performed based on radio resource allocation information that is determined in advance by the base station apparatus  3  using the radio resource control unit  3011  and that is included in the uplink grant notified to each of the terminal apparatuses  1 . The demultiplexing unit  3055  performs channel compensation for the control channel and the shared channel from the channel estimate input from the channel measurement unit  3059 . Furthermore, the demultiplexing unit  3055  outputs the demultiplexed reference signal channel to the channel measurement unit  3059 . 
     The demultiplexing unit  3055  acquires a modulation symbol of the uplink data and a modulation symbol of the uplink control information (HARQ-ACK) from the control channel and the shared channel that are demultiplexed. The demultiplexing unit  3055  outputs the modulation symbol of the uplink data acquired from the shared channel signal to the data demodulation/decoding unit  3051 . The demultiplexing unit  3055  outputs the modulation symbol of the uplink control information (HARQ-ACK) acquired from the control channel or the shared channel to the control information demodulation/decoding unit  3053 . 
     The channel measurement unit  3059  measures the channel estimate, the channel quality, and the like, based on the uplink reference signal input from the demultiplexing unit  3055  and outputs the measurement result to the demultiplexing unit  3055  and the higher layer processing unit  301 . 
     The data demodulation/decoding unit  3051  decodes the uplink data from the modulation symbol of the uplink data input from the demultiplexing unit  3055 . The data demodulation/decoding unit  3051  outputs the decoded uplink data to the higher layer processing unit  301 . 
     The control information demodulation/decoding unit  3053  decodes the HARQ-ACK from the modulation symbol of the HARQ-ACK input from the demultiplexing unit  3055 . The control information demodulation/decoding unit  3053  outputs the decoded HARQ-ACK to the higher layer processing unit  301 . 
     The transmitter  307  generates the downlink reference signal according to the control signal input from the controller  303 , encodes and modulates the downlink control information and the downlink data that are input from the higher layer processing unit  301 , multiplexes the control channel, the shared channel, and the reference signal channel, and transmits a signal resulting from the multiplexing to the terminal apparatus  1  through the transmit and receive antenna  309 . 
     The coding unit  3071  encodes the downlink control information and the downlink data input from the higher layer processing unit  301 . The modulation unit  3073  modulates the coded bits input from the coding unit  3071 , in compliance with the modulation scheme such as BPSK, QPSK, 16 QAM, or 64 QAM. The modulation unit  3073  may apply precoding to the modulation symbol. The precoding may include a transmission precode. Note that precoding may be a multiplication (application) of a precoder. 
     The downlink reference signal generation unit  3079  generates a downlink reference signal. The multiplexing unit  3075  multiplexes the modulation symbol of each channel and the downlink reference signal and generates the transmission symbol. 
     The multiplexing unit  3075  may apply precoding to the transmission symbol. The precoding that the multiplexing unit  3075  applies to the transmission symbol may be applied to the downlink reference signal and/or the modulation symbol. The precoding applied to the downlink reference signal and the precoding applied to the modulation symbol may be the same or different. 
     The radio transmitting unit  3077  performs Inverse Fast Fourier Transform (IFFT) on the multiplexed transmission symbol and the like to generate a time symbol. The radio transmitting unit  3077  modulates the time symbol in compliance with an OFDM scheme, generates a baseband digital signal, converts the baseband digital signal into an analog signal, generates an in-phase component and an orthogonal component of an intermediate frequency from the analog signal, removes frequency components unnecessary for the intermediate frequency band, converts (up-converts) the signal of the intermediate frequency into a signal of a high frequency, removes unnecessary frequency components, and generates a carrier signal (carrier, RF signal, or the like). The radio transmitting unit  3077  performs power amplification on the carrier signal and outputs the amplified signal to the transmit and receive antenna  309  for transmission. 
     Hereinafter, various aspects of the terminal apparatus and the base station apparatus in the present embodiment will be described. 
     (1) To accomplish the object described above, aspects of the present invention are contrived to provide the following measures. That is, a first aspect of the present invention is a terminal apparatus including: a receiver configured to receive a transport block in a PDCCH and a PDSCH scheduled by the PDCCH and receive RRC information indicating the number of CBGs X; a transmitter configured to transmit HARQ-ACKs corresponding to the transport block, in which the transport block is segmented into multiple CBs; the number of multiple CBs N CB  is determined by a size of the transport block; in a case that the number of CBs N CB  is less than X, the N CB  CBs are included in different N CB  CBGs respectively; in a case that the number of CBs N CB  is less than X, the transmitter generates N CB  HARQ-ACKs corresponding to the N CB  CBGs and X-N CB  NACKs; and the HARQ-ACKs corresponding to the transport block includes the N CB  HARQ-ACKs and X-N CB  NACKs. 
     (2) In addition, a second aspect of the present invention is a base station apparatus including: a transmitter configured to transmit a transport block in a PDCCH and a PDSCH scheduled by the PDCCH and transmit RRC information indicating the number of CBGs X; a receiver configured to receive HARQ-ACKs corresponding to the transport block, in which the transport block is segmented into multiple CBs; the number of multiple CBs N CB  is determined by a size of the transport block; in a case that the number of CBs N CB  is less than X, the N CB  CBs are included in different N CB  CBGs respectively; in a case that the number of CBs N CB  is less than X, the receiver receives N CB  HARQ-ACKs corresponding to the N CB  CBGs and X-N CB  NACKs; and the HARQ-ACKs corresponding to the transport block includes the N CB  HARQ-ACKs and X-N CB  NACKs. 
     (3) In addition, a third aspect of the present invention is a terminal apparatus including: a receiver configured to receive multiple CBs in a PDCCH and a PDSCH scheduled by the PDCCH and receive RRC information indicating the number of CBGs X; and a transmitter configured to transmit HARQ-ACKs corresponding to a transport block, in which the multiple CBs constitutes a part of the transport block; the number of multiple CBGs Y is determined by information indicating transmission of CBGs included in the PDCCH; each of the multiple CBs is included in any one of the Y CBGs; and, in a case that the number of CBGs Y is less than X, the transmitter generates Y HARQ-ACKs corresponding to the Y CBGs and X-Y NACKs. 
     (4) In addition, a fourth aspect of the present invention is a base station apparatus including: a transmitter configured to transmit multiple CBs in a PDCCH and a PDSCH scheduled by the PDCCH and transmit RRC information indicating the number of CBGs X; and a receiver configured to receive HARQ-ACKs corresponding to a transport block, in which the multiple CBs constitutes a part of the transport block; the number of multiple CBGs Y is determined by information indicating transmission of CBGs included in the PDCCH; each of the multiple CBs is included in any one of the Y CBGs; and, in a case that the number of CBGs Y is less than X, the receiver receives Y HARQ-ACKs corresponding to the Y CBGs and X-Y NACKs. 
     A program running on the terminal apparatus  1  and the base station apparatus  3  according to an aspect of the present invention may be a program that controls a central processing unit (CPU) and the like (a program causing a computer to function) in such a manner as to realize the functions of the above-described embodiment according to an aspect of the present invention. The information handled in these devices is temporarily stored in a Random Access Memory (RAM) while being processed. Thereafter, the information is stored in various types of Read Only Memory (ROM) such as a Flash ROM and a Hard Disk Drive (HDD), and when necessary, is read by the CPU to be modified or rewritten. 
     Note that the terminal apparatus  1  and the base station apparatus  3  according to the above-described embodiment may be partially achieved by a computer. In that case, this configuration may be realized by recording a program for realizing such control functions on a computer-readable recording medium and causing a computer system to read the program recorded on the recording medium for execution. 
     Note that it is assumed that a “computer system” mentioned here refers to a computer system built into the terminal apparatus  1  or the base station apparatus  3 , and the computer system includes an OS and hardware components such as a peripheral apparatus. Furthermore, a “computer-readable recording medium” refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, and the like, and a storage apparatus such as a hard disk built into the computer system. 
     Moreover, the “computer-readable recording medium” may include a medium that dynamically retains a program for a short period of time, such as a communication line that is used for transmission of the program over a network such as the Internet or over a communication line such as a telephone line, and may also include a medium that retains a program for a fixed period of time, such as a volatile memory within the computer system for functioning as a server or a client in such a case. Furthermore, the program may be configured to realize some of the functions described above, and also may be configured to be capable of realizing the functions described above in combination with a program already recorded in the computer system. 
     Furthermore, the terminal apparatus  1  and the base station apparatus  3  according to the above-described embodiment may be achieved as an aggregation (apparatus group) including multiple apparatuses. Each of the apparatuses constituting such an apparatus group may include at least one of respective functions or functional blocks of the terminal apparatus  1  and the base station apparatus  3  according to the above-described embodiment. The apparatus group may have respective general functions or functional blocks of the terminal apparatus  1  and the base station apparatus  3 . Furthermore, the terminal apparatus  1  and the base station apparatus  3  according to the above-described embodiment can also communicate with a base station apparatus as an aggregation. 
     Furthermore, the base station apparatus  3  according to the above-described embodiment may serve as an Evolved Universal Terrestrial Radio Access Network (EUTRAN). Furthermore, the base station apparatus  3  according to the above-described embodiment may have at least one of the functions of a node higher than an eNodeB. 
     Furthermore, some or all portions of each of the terminal apparatus  1  and the base station apparatus  3  according to the above-described embodiment may be typically achieved as an LSI which is an integrated circuit or may be achieved as a chip set. The functional blocks of each of the terminal apparatus  1  and the base station apparatus  3  may be individually achieved as a chip, or some or all of the functional blocks may be integrated into a chip. Furthermore, a circuit integration technique is not limited to the LSI, and may be realized with a dedicated circuit or a general-purpose processor. Furthermore, in a case where with advances in semiconductor technology, a circuit integration technology with which an LSI is replaced appears, it is also possible to use an integrated circuit based on the technology. 
     Furthermore, each functional block or various characteristics of the apparatuses used in the above-described embodiment may be implemented or performed on an electric circuit, for example, an integrated circuit or multiple integrated circuits. An electric circuit designed to perform the functions described in the present specification may include a general-purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), or other programmable logic devices, discrete gates or transistor logic, discrete hardware components, or a combination thereof. The general-purpose processor may be a microprocessor or may be a processor of known type, a controller, a micro-controller, or a state machine instead. The above-mentioned electric circuit may include a digital circuit, or may include an analog circuit. Furthermore, in a case that with advances in semiconductor technology, a circuit integration technology appears that replaces the present integrated circuits, it is also possible to use a new integrated circuit based on the technology according to one or more aspects of the present invention. 
     Furthermore, according to the above-described embodiment, the terminal apparatus has been described as an example of a communication apparatus, but the present invention is not limited to such a terminal apparatus, and is applicable to a terminal apparatus or a communication apparatus of a fixed-type or a stationary-type electronic apparatus installed indoors or outdoors, for example, such as an Audio-Video (AV) apparatus, a kitchen apparatus, a cleaning or washing machine, an air-conditioning apparatus, office equipment, a vending machine, and other household apparatuses. 
     The embodiments of the present invention have been described in detail above referring to the drawings, but the specific configuration is not limited to the embodiments and includes, for example, an amendment to a design that falls within the scope that does not depart from the gist of the present invention. Furthermore, various modifications are possible within the scope of one aspect of the present invention defined by claims, and embodiments that are made by suitably combining technical means disclosed according to the different embodiments are also included in the technical scope of the present invention. Furthermore, a configuration in which constituent elements, described in the respective embodiments and having mutually the same effects, are substituted for one another is also included in the technical scope of the present invention. 
     INDUSTRIAL APPLICABILITY 
     An aspect of the present invention can be utilized, for example, in a communication system, communication equipment (for example, a cellular phone apparatus, a base station apparatus, a wireless LAN apparatus, or a sensor device), an integrated circuit (for example, a communication chip), or a program. 
     REFERENCE SIGNS LIST 
     
         
           1  ( 1 A,  1 B,  1 C) Terminal apparatus 
           3  Base station apparatus 
           101  Higher layer processing unit 
           103  Controller 
           105  Receiver 
           107  Transmitter 
           109  Transmit and receive antenna 
           1011  Radio resource control unit 
           1013  Scheduling unit 
           1051  Decoding unit 
           1053  Demodulation unit 
           1055  Demultiplexing unit 
           1057  Radio receiving unit 
           1059  Channel measurement unit 
           1071  Coding unit 
           1073  Shared channel generation unit 
           1075  Control channel generation unit 
           1077  Multiplexing unit 
           1079  Radio transmitting unit 
           10711  Uplink reference signal generation unit 
           301  Higher layer processing unit 
           303  Controller 
           305  Receiver 
           307  Transmitter 
           309  Transmit and receive antenna 
           3000  Transmission process 
           3001  Coding processing unit 
           3002  Scrambling processing unit 
           3003  Modulation mapping processing unit 
           3004  Layer mapping processing unit 
           3005  Transmission precode processing unit 
           3006  Precode processing unit 
           3007  Resource element mapping processing unit 
           3008  Baseband signal generation processing unit 
           3011  Radio resource control unit 
           3013  Scheduling unit 
           3051  Data demodulation/decoding unit 
           3053  Control information demodulation/decoding unit 
           3055  Demultiplexing unit 
           3057  Radio receiving unit 
           3059  Channel measurement unit 
           3071  Coding unit 
           3073  Modulation unit 
           3075  Multiplexing unit 
           3077  Radio transmitting unit 
           3079  Downlink reference signal generation unit 
           401  Segmentation and CRC attachment unit 
           4001  CRC attachment unit 
           4002  Encoder unit 
           4003  Sub-block interleaver unit 
           4004  Bit collection unit 
           4005  Bit selection and pruning unit 
           4006  Concatenation unit 
           4011  Code block segmentation unit 
           4012  CRC attachment unit