Patent Description:
In the UMTS (Universal Mobile Telecommunications System) network, the specifications of long term evolution (LTE) have been drafted for the purpose of further increasing high speed data rates, providing lower delays and so on (see non-patent literature <NUM>). Successor system of LTE -- referred to as "LTE-advanced" (also referred to as "LTE-A") -- have been under study for the purpose of achieving further broadbandization and increased speed beyond LTE, and the specifications thereof have been drafted as LTE Rel. <NUM> to <NUM>.

The system band in LTE Rel. <NUM> to <NUM> includes at least one component carrier (CC), where the LTE system band constitutes one unit. Such bundling of a plurality of CCs into a wide band is referred to as "carrier aggregation" (CA).

In CA of Rel. <NUM> to <NUM>, uplink control information (UCI) to be transmitted from a user terminal is transmitted in an uplink control channel (PUCCH). Also, when the PUCCH and the PUSCH have to be transmitted at the same time while simultaneous transmission of an uplink control channel and an uplink shared channel (PUSCH) is not configured, the user terminal multiplexes all the uplink control information on the PUSCH (piggyback).

In<NPL>describe using dual connectivity (DC) principles for PUCCH on secondary cell (SCell) with CA, aiming to show that support for PUCCH SCell with CA is possible when assuming inter alia that PUCCH is transmitted on two serving cells, namely the PCell for SCells in a first PUCCH group and the SCell configured to carry PUCCH for SCells in a second PUCCH group. The draft describes options for UCI feedback depending on whether PUSCH is scheduled on none of the PUCCH groups, only one of the PUCCH groups or each PUCCH group: when no PUSCH is scheduled at all, the UCI is carried on the corresponding PUCCH in each group; when a PUSCH is scheduled in each PUCCH group, the UCI is carried on the corresponding PUSCH in each group; and when PUSCH is scheduled in only one PUCCH cell group, the UCI is carried in the PUSCH for the group having the PUSCH scheduled and on the PUCCH for the other group. The draft also suggest that, in case simultaneous PUCCH/PUSCH transmission between two PUCCH cell groups is not mandatorily supported by UEs supporting PUCCH on SCell for CA, the UCI may for all PUCCH groups may be piggybacked into one PUSCH if PUSCH is only scheduled for one group.

In CA of and after LTE Rel. <NUM>, which is a more advanced successor system of LTE, a method ("PUCCH on SCell") of transmitting uplink control information by using the PUCCHs not only of the primary cell, but also of SCells, in order to realize more flexible wireless communication, is under study.

However, when a user terminal transmits uplink control information by using the PUCCHs of secondary cells, if uplink data transmission (PUSCH transmission) is commanded in a certain CC, how to transmit the uplink control information and the uplink data becomes the problem.

The present invention has been made in view of the foregoing points, and it is therefore an object of the present invention to provide a terminal and a radio communication method that allow adequate UL transmission even when transmission of uplink control information using secondary cells (SCells) is made configurable.

According to the present invention, there is provided a terminal as set out in Claim <NUM>. According to the present invention, there is also provided a radio communication method as set out in Claim <NUM>.

According to the present invention, UL transmission can be made adequately even when transmission of uplink control information using secondary cells (SCells) is made configurable.

There is described herein a user terminal that communicates with a radio base station by using carrier aggregation, and has a receiving section that receives a DL signal transmitted from the radio base station, a transmission section that transmits uplink control information that is generated based on the DL signal received, and a control section that controls transmission of the uplink control information, and, in this user terminal, the control section controls the transmission of the uplink control information using an uplink control channel and controls the transmission of the uplink control information using an uplink shared channel in each of a plurality of cell groups, each cell group including at least one component carrier (CC).

<FIG> provide diagrams to show examples of uplink control information (UCI) transmission methods according to Rel. <NUM> to <NUM>. <FIG> shows a UCI multiplexing method that is for use when there is no uplink data transmission command (PUSCH transmission), and <FIG> shows a UCI multiplexing method that is for use when there is an uplink data transmission command. Also, <FIG> illustrate examples of cases where five CCs (one PCell and four SCells) are configured, and where simultaneous transmission of a PUCCH and a PUSCH is not configured.

<FIG> shows a case where, in a given subframe, PUSCH transmission is not carried out in CC #<NUM> to CC #<NUM>. In this case, a user terminal multiplexes and transmits each CC's uplink control information on the PUCCH of a predetermined CC (here, CC #<NUM>).

<FIG> shows a case where there is uplink data (PUSCH transmission) to transmit to a radio base station in CC #<NUM> (SCell) in a given subframe. In this case, a user terminal multiplexes (piggyback) and transmits uplink control information (uplink control information that should be transmitted in the PUCCH of CC #<NUM>) in the PUSCH of CC #<NUM>.

In this way, when simultaneous transmission of a PUCCH and a PUSCH is not configured, given that a user terminal does not transmit a PUCCH when there is a PUSCH to transmit, it is possible to maintain single carrier transmission. Note that a structure may be employed here in which, when PUSCH transmission takes place in multiple CCs, a PUCCH is allocated to a predetermined CC (the primary cell, the secondary cell with the minimum cell index, etc.).

Also, in CA of Rel. <NUM> to <NUM>, simultaneous transmission of a PUCCH and a PUSCH (hereinafter "simultaneous PUCCH-PUSCH transmission") is supported. <FIG> show examples of uplink control information transmission methods for use when simultaneous PUCCH-PUSCH transmission is configured.

When simultaneous PUCCH-PUSCH transmission is configured, uplink control information is transmitted by using PUCCHs alone, or by using some PUCCHs and some PUSCHs. Simultaneous PUCCH-PUSCH transmission has two patterns -- namely, simultaneous PUCCH-PUSCH transmission within a CC and simultaneous PUCCH-PUSCH transmission across CCs.

<FIG> shows a case where, when simultaneous PUCCH-PUSCH transmission within a CC is configured, a user terminal simultaneously allocates (multiplexes) a PUCCH and a PUSCH to one CC (here, the primary cell). <FIG> shows a case where, when simultaneous PUCCH-PUSCH transmission across CCs is configured, a user terminal simultaneously allocates a PUCCH and a PUSCH to different CCs. Here, a case is shown where the PUCCH is allocated to the primary cell (CC #<NUM>) and the PUSCH is allocated to a secondary cell (CC #<NUM>).

In this way, when simultaneous PUCCH-PUSCH transmission is configured, a PUCCH and a PUSCH are transmitted simultaneously within the same CC or across different CCs.

Also, with CA of Rel. <NUM> and later versions, a study is in progress to transmit uplink control information by using not only the PUCCH of the PCell, but also by using the PUCCHs of SCells (referred to as "PUCCH on SCell"). In particular, in Rel. <NUM> and later versions, a study is in progress to apply CA, in which the number of CCs, which has been limited to five CCs or fewer until Rel. <NUM>, is expanded. When CA is executed with an expanded number of CCs, it is possible to prevent the concentration of uplink control information in the PCell by applying PUCCH on Scell.

To transmit uplink control information by using an SCell's PUCCH, it may be possible to configure a plurality of cell groups, which are each comprised of at least one CC, and determine the transmission timing and/or the PUCCH resource per cell group. A cell group like this may be referred to as a "PUCCH cell group," a "PUCCH CG," or a "PUCCH cell-group. " Also, an SCell in which a PUCCH is configured in a cell groups may be referred to as a "PUCCH cell," a "PUCCH CC," or a "PUCCH-SCell.

<FIG> shows a case where two cell groups are configured in CA in which five CCs are configured. <FIG> shows the case where the first cell group is comprised of CC #<NUM> to CC #<NUM> and the second cell group is comprised CC #<NUM> and CC #<NUM>, and where CC #<NUM> is the PCell and CCs #<NUM> to #<NUM> are SCells.

A user terminal can transmit uplink control information using the PUCCH configured in one CC in each cell group. <FIG> presumes the case where the first cell group transmits a PUCCH in CC #<NUM>, which serves as the primary cell, and where the second cell group transmits a PUCCH in CC #<NUM>, which serves that serves as a PUCCH-Scell.

Thus, by controlling the transmission of uplink control information by configuring the allocation of PUCCHs every predetermined cell group, it is possible to transmit uplink control information properly even when the number of CCs is expanded. Meanwhile, when simultaneous PUCCH-PUSCH transmission is configured, A PUCCH and a PUSCH are transmitted simultaneously within the same CC or across different CCs.

So, assuming the case where PUCCH transmission (PUCCH on SCell) is controlled by configuring cell groups, the present inventors have come up with the idea of controlling the transmission of uplink control information using the PUSCH (UCI on PUSCH) in each cell group or across cell groups.

Also, in Rel. <NUM> and later, it may be possible that each cell group configures HARQ timings based on a different duplex mode (FDD or TDD). Assuming this case, the present inventors have come with the idea of determining the number of HARQ bits to be transmitted from a user terminal based on predetermined conditions, and controlling the transmission of HARQ-ACKs.

Now, embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Note that, although cases will be shown in the following description in which the number of CCs is five, the embodiments of the present invention are by no means limited to this. The embodiments of the present invention are applicable to cases where the number of CCs is four or less or to cases where the number of CCs is six or more. Further, although the embodiments of the present invention are particularly suitable for use in cases where simultaneous PUCCH-PUSCH transmission is not configured in each cell group, this is by no means limiting. Although examples will be shown in the following description where two cell groups of the first cell group and the second cell group will be used as a plurality of cell groups, the number of cell groups is not limited to this.

A case will be described with the first example, not claimed, where the transmission of uplink control information (UCI on PUSCH) is controlled using an uplink shared channel, in each of a plurality of cell groups, where each group includes at least one component carrier (CC).

<FIG> shows an example of a case where the transmission of uplink control information using the PUSCH is controlled on a per cell group basis. <FIG> shows a case where a first cell group with three CCs and a second cell group with two CCs are configured in a user terminal. Information about the CCs and/or cell groups to configure in the user terminal can be reported to the user terminal through higher layer signaling (for example, RRC signaling and so on).

Further, <FIG> shows a case where a PUCCH is transmitted by using CC #<NUM>, which serves as the PCell in the first cell group, and where a PUCCH is transmitted by using CC #<NUM>, which serves as a PUCCH-Scell in the second cell group.

For example, assume the case where, in a given subframe, a PUSCH is transmitted in CC #<NUM> (SCell) of the first cell group and where no PUSCH is transmitted in the second cell group. In this case, in the first cell group, when there is no PUSCH transmission, uplink control information (for example, HARQ-ACKs) transmitted in the PUCCH of CC #<NUM> is multiplexed on the PUSCH of CC #<NUM>. On the other hand, in the second cell group, uplink control information is transmitted using the PUCCH of CC #<NUM>.

The required communication quality differs between a cell group including a PCell that secures connectivity through mobility management and communication quality measurements and a cell group not including a PCell. Cell groups not including a PCell are highly likely to be additionally used to improve throughput, and yet securing the quality of UCI is not necessarily guaranteed. However, in this way, according to the first example, the transmission of uplink control information using the PUCCH and the transmission of uplink control information using the PUSCH are controlled on a per cell group basis, so that the UCI of the PCell, which can secure the quality of connection, can be transmitted from the PCell, and the UCI of SCells, which are added for improved data rates, can be transmitted from the SCells. As a result, it is possible to achieve both quality assurance and off-loading of UCI.

Further, the user terminal may transmit periodic channel state information (P-CSI) on a per cell group basis. In existing CA, only one CC's P-CSI can be reported per subframe, and other CCs' CSIs are not allowed to be reported at the same time (that is, dropped). By contrast, with the first example, it is possible to configure P-CSI reports of varying cell groups in the same period and in the same timing. This enables highly accurate scheduling in the radio base station based on the P-CSI of each cell group.

Also, the user terminal can configure different HARQ timings in each cell group. For example, the user terminal can control HARQ transmission by applying the HARQ timing based on the FDD scheme to the first cell group (first CG), and control HARQ transmission by applying the HARQ timing based on the TDD scheme to the second cell group (second CG) (see <FIG>).

For the HARQ timing based on the FDD scheme and/or the HARQ timing based on the TDD scheme, the timings defined in and before Rel. <NUM> can be used. For example, as the HARQ timing based on the FDD scheme, it is possible to use the timing a predetermined period (for example, four subframes) after the subframe in which a DL signal is received. In addition, as the HARQ timing based on the TDD scheme, a predetermined timing based on the UL/DL configuration can be used.

The HARQ timing to apply to each cell group can be determined based on the duplex mode used in a CC where PUCCH transmission is performed (PCell, PUCCH-SCell, etc.).

In the first cell group, which uses the HARQ timing based on the FDD scheme, the user terminal feeds back uplink control information (for example, HARQ) corresponding to each DL subframe in the UL subframe that comes four subframes later. When a PUSCH is transmitted in the UL subframe, uplink control information is allocated to the PUSCH and transmitted (see <FIG>).

In the second cell group, in which the HARQ timing based on the TDD scheme is used, the user terminal feeds back uplink control information in a predetermined UL subframe according to the HARQ timing corresponding to a predetermined UL/DL configuration (here, UL/DL configuration <NUM>). When a PUSCH is transmitted in the predetermined UL subframe, uplink control information is allocated to the PUSCH and transmitted (see <FIG>).

In this way, when uplink control information feedback using the PUCCH and/or the PUSCH is controlled on a per cell group basis, cases occur where the number of DL subframes to which HARQ can be transmitted in a given UL subframe is different in each cell group. For example, in the second cell group using the HARQ timing based on the TDD scheme, HARQ-ACKs to correspond to a plurality of DL subframes temporally are transmitted in the PUSCH. On the other hand, in the first cell group using the HARQ timing based on the FDD scheme, basically, an HARQ-ACK to correspond to one DL subframe is transmitted in the PUSCH.

Therefore, in the first example, different transmission/reception operations (for example, different HARQ operations) are applied to each cell group, on the assumption that the HARQ which the user terminal transmits per cell group corresponds to varying numbers of DL subframes. To be more specific, in the cell group using the HARQ timing based on the TDD scheme, the user terminal receives/detects DL signals using DAIs (Downlink Assignment Indices), and controls HARQ transmission.

For example, DAIs can be used as a DL subframe counter in TDD in which A/N bundling is employed, and DAIs can be included in PDSCH-scheduling downlink control information (DCI) and PUSCH-scheduling DCI, and reported to the user terminal.

For example, when DL signals are transmitted to the user terminal in four consecutive subframes (SF #<NUM> to SF #<NUM>) the radio base station transmits DAIs = <NUM> to <NUM> in each of the DCIs that schedule the PDSCH in SFs #<NUM> to #<NUM> and transmits the same. If the user terminal fails to detect the DL assignment (PDCCH) in SF #<NUM>, the user terminal cannot acquire DAI = <NUM>, so the user terminal can judge that the DL assignment in SF #<NUM> is a detection error (see <FIG>). As a result, the user terminal can recognize that the A/N for second SF #<NUM> is wrong.

Also, when DL signals are transmitted to the user terminal in three subframes (SFs #<NUM>, #<NUM> and #<NUM>), DAIs = <NUM> to <NUM> are included in the DCIs for scheduling the PDSCH in SFs #<NUM>, #<NUM> and #<NUM>. If the user terminal fails to detect the DL assignment (PDCCH) of SF #<NUM>, the user terminal cannot acquire DAI = <NUM>, so the user terminal can judge that the DL assignment of SF #<NUM> or #<NUM> is a detection error (see <FIG>). As a result, the user terminal can recognize that the first A/N (SF #<NUM> or SF #<NUM>) is wrong.

Meanwhile, a DAI can be included in DCI (UL grant) that schedules the PUSCH in an uplink subframe (SF #<NUM>) for the user terminal. Unlike PDSCH-scheduling DCIs, only one UL grant is generated in one uplink subframe. Therefore, a DAI included in PUSCH-scheduling DCI does not report PDSCH that is scheduled as a counter, but reports the total number of PDSCHs corresponding to the PUSCH specified by this UL grant. Accordingly, the user terminal, when detecting a UL grant, determines the number of bits of A/N acknowledgment signals to multiplex on the PUSCH (piggyback) according to the value indicated by the DAI included in the UL grant.

As described above, the user terminal can learn information (the number of DL subframes) about the DL subframes to which DL signals are allocated, based on DAIs transmitted from the radio base station.

UL-DAIs are included in DCI (UL grant) for scheduling the second cell group and transmitted to the user terminal, so that the user terminal can properly transmit HARQ in the second cell group using the HARQ timing based on the TDD scheme (see <FIG>).

On the other hand, in the first cell group, in which the HARQ-ACK timing based on the FDD scheme is used, DAI-based control can be made unnecessary. Therefore, DCI (UL grant) for scheduling the first cell group can be transmitted to the user terminal without including UL-DAIs. In this case, it is possible to suppress an increase in the overhead of the DCI transmitted from the radio base station.

The user terminal judges whether or not a UL-DAI is included in DCI (UL grant), for each cell group, and controls the transmission/reception operations (for example, HARQ feedback). For example, the user terminal calculates the payload size of DCI on the assumption that DAIs are not include in the DCI for the cell group that utilizes the HARQ timing based on the FDD scheme and that DAIs are included in the DCI for the cell group that uses the HARQ timing based on the TDD scheme. Then, based on this payload size, the user terminal can perform the receiving operation, such as blind decoding of DCI, in the PDCCH or the EPDCCH of the CC included in each cell group.

Although <FIG> and <FIG> show cases where one CC is configured in each cell group, even when a plurality of CCs are configured in each cell group, HARQ feedback (whether or not DAI is present) can be controlled based on the duplex mode used to configure the HARQ timing.

The HARQ timing of each cell group can be determined according to the duplex mode (FDD or TDD) applied to a predetermined CC in each cell group. The predetermined CC in each cell group can be the cell to transmit the PUCCH (PUCCH cell).

When the PUCCH cell of each cell group (for example, CC #<NUM> in <FIG>) is a TDD cell using TDD, the user terminal performs the transmission/reception processes on the assumption that a UL-DAI is included in the UL grant to allocate the PUSCH in this cell group. The transmission/reception processes include the decoding process, the HARQ-ACK transmission process (for example, determining the number of bits, etc.), and the like.

Further, when the PUCCH cell of each cell group (for example, CC #<NUM> in <FIG>) is an FDD cell using FDD, the user terminal performs the transmission/reception processes on the assumption that a UL-DAI is included in the UL grant to allocate the PUSCH in this cell group.

In this manner, by using DAIs according to the HARQ timing applied to each cell group, the number of HARQ-ACK bits to be multiplexed on the PUCCH or the PUSCH can be appropriately determined. Note that, in the first embodiment, it is also possible to use the UL transmission control in dual connectivity (DC) stipulated in Rel.

A case will be described with the second example where, when a plurality of cell groups each including at least one component carrier (CC) are configured, uplink control information transmission to use an uplink shared channel (UCI on PUSCH) is controlled across a plurality of cell groups.

<FIG> shows an example of the case of controlling uplink control information transmission using the PUSCH (UCI on PUSCH) regardless of cell groups. <FIG> shows a case where a first cell group with three CCs and a second cell group with two CCs are configured in a user terminal.

Also, <FIG> shows a case where a PUCCH is transmitted by using CC #<NUM>, which serves as the PCell in the first cell group, and where a PUCCH is transmitted by using CC #<NUM>, which serves as a PUCCH-Scell in the second cell group.

For example, assume the case where, in a given subframe, a PUSCH is transmitted in CC #<NUM> (SCell) of the first cell group and where no PUSCH is transmitted in the second cell group. In this case, in the first cell group, the control information (for example, HARQ-ACK) to be transmitted in the PUCCH of CC #<NUM> if there is no PUSCH transmission is multiplexed and transmitted on the PUSCH of CC #<NUM>. Also, in the second cell group, the control information to be transmitted in the PUCCH of CC #<NUM> if there is no PUSCH transmission is multiplexed and transmitted in the PUSCH of CC #<NUM> of the first cell group.

As described above, in the second example, which is configured to control PUCCH transmission (PUCCH on SCell) on a per PUCCH cell group basis, when there is PUSCH transmission, each cell group's uplink control information is allocated to a predetermined cell where the PUSCH is transmitted. That is, when there is PUSCH transmission in a given CC, uplink control information is multiplexed on the PUSCH, irrespective of which PUCCH cell group the uplink control information belongs to.

This allows single carrier transmission to be implemented when uplink control information is transmitted in the PUSCH. As a result of this, compared to cases where multi-carrier transmission is required (see, for example, above <FIG>), it is possible to prevent the situation where the PUSCH transmission power exceeds the maximum transmission power and is limited (power limited).

Further, the user terminal may transmit periodic channel state information (P-CSI) on a per cell group basis. For example, if periodic CSI (P-CSI) is produced in the same subframe in different cell groups, the user terminal can multiplex and transmit the periodic CSI of each cell group on the same CC's PUSCH. Alternatively, the user terminal may select the periodic CSI of one CC based on a predetermined condition (and drops the periodic CSIs of the other CCs), and multiplex and transmit the selected periodic CSI on the PUSCH.

In this case, in the timing (predetermined UL subframe) at which HARQ is transmitted in the second cell group using the HARQ timing based on the TDD scheme, the user terminal multiplexes the uplink control information of the two cell groups onto the PUSCH of a predetermined CC. In the case shown in <FIG>, the user terminal transmits an HARQ corresponding to one DL subframe of the first cell group and HARQs corresponding to four DL subframes of the second cell group in the PDSCH of a predetermined CC (here, a CC of the first cell group).

In this case, how to determine the number of HARQ bits to feed back from the user terminal is the problem. For example, in CA of existing systems (Rel. <NUM> or earlier versions), when an FDD-based HARQ timing is applied, the user terminal determines the number of HARQ-ACK bits to transmit in the PUSCH (UCI on PUSCH) based on higher layer signaling.

To be more specific, the maximum value obtained from the number of CCs configured in the user terminal and the transmission mode (TM) of each CC is used as the number of HARQ-ACK bits. For example, when the number of CCs is <NUM> and the number of codewords (CWs) is <NUM>, the number of HARQ-ACK bits is <NUM> (maximum). Also, for a CC where no DL signal is scheduled, a NACK is fed back. In this way, when applying existing FDD-based HARQ timing and multiplexing uplink control information on the PUSCH, HARQ-ACKs are limited to maximum <NUM> bits.

However, in <FIG>, the uplink control information of the second cell group that uses the HARQ of the TDD scheme is multiplexed on the PUSCH of the cell using the HARQ of the FDD scheme. In this case, the number of HARQ-ACK bits included in the PUSCH transmitted in the cell using the FDD-scheme-based HARQ timing is not determined based only on "the number of CCs × the number of CWs," but is also influenced by the number of DL subframes in the time direction.

For example, when a first cell group is formed with one CC using FDD and a second cell group is formed with one CC using TDD (see, for example, <FIG>), the HARQ-ACK bits to be allocated to the PUSCH of the cell of the first cell group are maximum <NUM> bits (= <NUM> × <NUM> + <NUM> × <NUM>). Also, if four TDD cells (<NUM> CCs) are included in the second cell group, the HARQ-ACK bits to be allocated to the PUSCH of the cell of the first cell group are maximum <NUM> bits (= <NUM> × <NUM> + <NUM> × <NUM> × <NUM>).

Therefore, when UCI on PUSCH is applied between the cell groups using the HARQ timing based on the FDD scheme and the cell group using the HARQ timing based on the TDD scheme, how to control the transmission of HARQ-ACKs is the problem.

In order to solve such a problem, in the present embodiment, HARQ transmission is controlled based on predetermined conditions. Hereinafter, HARQ transmission methods according to a second example will be described. Although cases will be shown in the following description where HARQ-ACKs of the CC of the second cell group using the HARQ timing based on the TDD scheme are transmitted by using the uplink shared channel of the CC of the first cell group using the HARQ timing based on the FDD scheme, the present embodiment is not limited to this.

In the first method, not claimed, when the uplink control information of each cell group is allocated to the PUSCH of the CC of the first cell group, the transmission of HARQ-ACKs is controlled according to the maximum number of bits that can be multiplexed on the PUSCH. The user terminal can determine the maximum number of bits that can be multiplexed on the PUSCH based on information reported in higher layer signaling. The information that is reported in higher layer signaling includes the number of CCs to be configured, the number of CWs configured per CC and the maximum number of DL subframes that can be fed back in one UL (for example, UL/DL configuration, and the like).

For example, assume that one CC that uses FDD is included in the first cell group and four CCs that use TDD are included in the second cell group. In this case, the user terminal controls the transmission of HARQ-ACKs on the assumption that <NUM> bits of HARQ-ACKs are transmitted. For example, assuming that there are <NUM> HARQ-ACK bits, the user terminal generates and encodes HARQ-ACK bits, and multiplexes these on the PUSCH.

The user terminal can control the encoding process based on the number of HARQ-ACK bits determined based on the information reported by higher layer signaling. For example, the user terminal can apply spatial bundling to the encoding of HARQ-ACKs if the number of HARQ-ACK bits is equal to or greater than a predetermined value. In this case, the user terminal can spatially bundle the HARQ-ACK bits of all the DL subframes in each CC and perform predetermined encoding on the HARQ-ACK bits after space bundling. When performing the encoding process, the user terminal can use different encoding according to the number of HARQ-ACK bits.

For example, if there are <NUM> HARQ-ACK bits, the user terminal can spatially bundle the HARQ-ACK bits of all the DL subframes of each CC (<NUM> bits), and apply predetermined encoding to the <NUM> bits after spatial bundling. As for the predetermined encoding, when there are more than <NUM> bits, channel coding of existing systems can be used for HARQ-ACKs.

Also, in the first method, DCI (UL grant) to allocate the PUSCH to the CCs of the second cell group includes a UL-DAI and is transmitted to the user terminal. On the other hand, a UL grant that allocates the PUSCH to the CC of the first cell group can be configured not to include a UL-DAI (see <FIG>).

The user terminal can judge the presence or absence of DAIs based on the duplex mode (FDD/TDD) applied to each cell group, and perform the receiving process (for example, blind decoding) of the PDCCH. In addition, the user terminal can control HARQ feedback assuming the maximum number of bits that can be used when HARQ-ACKs are transmitted in the PUSCH. In this case, the user terminal can perform control so that NACK is transmitted to the CCs and/or CWs where DL signals are not received.

In this way, the user terminal determines the HARQ-ACK bits taking into consideration the number of DL subframes in the second cell group, so that, even when these HARQ-ACKs are multiplexed on the PUSCH of the CC of the first cell group, the user terminal can transmit the HARQ-ACKs appropriately.

The second method, which falls within the scope of at least one of the independent claims, is configured such that, when the uplink control information of each cell group is allocated to the PUSCH of the CC of the first cell group, the number of HARQ-ACK bits is determined based on predetermined information notified by physical signaling.

As a background example, predetermined information reported in higher layer signaling includes at least one of information about the number of CCs to be configured and information about the number of CWs configured in each CC. The information reported in physical signaling includes information about the number of scheduled DL subframes, which is acquired by usingDAIs. Using DAIs, the user terminal determines the number of DL subframes to be scheduled based on the value specified by the UL-DAI (the number of DL subframes actually allocated).

For example, assume that one CC that uses FDD is included in the first cell group and four CCs that use TDD are included in the second cell group. In this case, the radio base station includes DAIs in downlink control information based on the DL subframes actually allocated to each cell, and transmits the downlink control information to the user terminal.

The user terminal can know the number of scheduled DL subframes based on the DAIs included in the downlink control information. Furthermore, the user terminal determines the number of HARQ-ACK bits to feed back based on the number of CCs and the number of CWs reported in higher layer signaling, and performs the transmission process (for example, the encoding process). Accordingly, when one CC that uses FDD is included in the first cell group and four CCs that use TDD is included in the second cell group, the radio base station and the user terminal can report/determine the number of HARQ-ACK bits in the range of <NUM> to <NUM> bits.

Also, the user terminal can control encoding according to the number of HARQ-ACK bits. For example, when the number of HARQ bits is <NUM>, <NUM>, <NUM> to <NUM> and <NUM> to <NUM>, different encoding processes can be applied. Also, if the number of HARQ bits exceeds <NUM> bits, the user terminal may apply space bundling.

Also, the second method can be configured so that a UL-DAI can be included in DCIs (UL grants) that allocate the PUSCH to the CCs of the second cell group, and in a UL grant that allocates the PUSCH to the CC of the first cell group (see <FIG>). Note that the user terminal can operate assuming that, when UL grants are present in a plurality of CCs, at least the UL-DAIs of each cell group have the same value.

The user terminal performs the receiving process (for example, blind decoding) of the PDCCH on the assumption that DAIs are included in the DCIs transmitted from each cell group. Also, the user terminal may determine the number of bits when HARQ-ACKs are transmitted in the PUSCH, based on DAI (the number of scheduled DL subframes), in addition to the number of CCs and the number of CWs.

In this way, the user terminal determines the HARQ-ACK bits taking into consideration the number of DL subframes scheduled, so that, even when these HARQ-ACKs are multiplexed on the PUSCH of the CC of the first cell group, the user terminal can transmit the HARQ-ACKs appropriately. Particularly, whereas, in the first method, the maximum number of bits calculated based on higher layer signaling is the payload, according to the second method, the payload can be specified dynamically using UL-DAIs, so that, when the number of assignments is small, it is possible to reduce the payload to lower the coding rate, and improve the quality of UCI higher.

When uplink control information is transmitted using the PUSCH of the CC of the first cell group, the DAI to include in the UL grant for scheduling the CC of the first cell group can be included in UL grants that are transmitted in all DL subframes. In this case, the DAIs can have the same value (for example, DAI = <NUM>). By including a DAI in the UL grants of all DL subframes, the user terminal can perform PDCCH decoding assuming that the payload size is the same irrespective of the subframe index, so that the burden of the reception process can be reduced.

Alternatively, a DAI can be included only in the UL grant for a specific DL subframe. The specific DL subframe may be, for example, a subframe that can transmit HARQ of the second cell group. In this case, the DAI payload can be reduced in subframes other than the specific subframe, so that an increase in the overhead of downlink control information can be suppressed.

The third method, not claimed, it is configured so that, when there is a cell (for example, the second cell group), in which an HARQ timing based on the TDD scheme is used, the user terminal does not transmit uplink control information using the PUSCH in a cell (for example, the first cell group), in which an HARQ timing based on the FDD scheme is used (see <FIG>).

When uplink data (UL-SCH) transmission is assigned to the first cell group, the user terminal drops the uplink data, and transmits uplink control information by using the PUCCH and/or the PUSCH of a CC in the second cell group.

For example, if there is a UL grant allocating a PUSCH to a CC in the second cell group, the user terminal multiplexes and transmits the uplink control information of the CC of the first cell group on this PUSCH. On the other hand, when there is no UL grant allocating a PUSCH to the CCs of the second cell group, the user terminal multiplexes and transmits the uplink control information of the CC of the first cell group on the PUCCH of a CC (PUCCH-SCell) of the second cell group.

Capability information regarding whether or not HARQ-ACKs for the second cell group can be multiplexed on the PUSCH of the CC of the first cell group may be reported from the user terminal to the base station in advance. For example, the user terminal reports this capability information to the radio base station in the form of UE capability signaling.

To a user terminal that can multiplex and transmit HARQ-ACKs for the second cell group on the PUSCH of the CC of the first cell group (a user terminal whose UE capability is" TRUE"), the first method or the second method is applied. On the other hand, to a user terminal that can multiplex and transmit HARQ-ACKs for the second cell group on the PUSCH of the CC of the first cell group (a user terminal whose UE capability is "FALSE"), the above third method is applied.

Now, the structure of the radio communication system according to a background example useful for understanding the present invention will be described below. In this radio communication system, the radio communication methods according to the embodiment of the present invention are employed. Note that the radio communication methods of the above-described embodiment may be applied individually or may be applied in combination.

<FIG> is a diagram to show an example of a schematic structure of a radio communication system according to the background example. Note that the radio communication system shown in <FIG> is a system to incorporate, for example, an LTE system, super <NUM>, an LTE-A system and so on. In this radio communication system, carrier aggregation (CA) and/or dual connectivity (DC) to bundle multiple component carriers (CCs) into one can be used. Note that this radio communication system may be referred to as "IMT-Advanced," or may be referred to as "<NUM>," "<NUM>," "FRA" (Future Radio Access) and so on.

The radio communication system <NUM> shown in <FIG> includes a radio base station <NUM> that forms a macro cell C1, and radio base stations 12a to 12c that form small cells C2, which are placed within the macro cell C1 and which are narrower than the macro cell C1. Also, user terminals <NUM> are placed in the macro cell C1 and in each small cell C2.

The user terminals <NUM> can connect with both the radio base station <NUM> and the radio base stations <NUM>. The user terminals <NUM> may use the macro cell C1 and the small cells C2, which use different frequencies, at the same time, by means of CA or DC. Also, the user terminals <NUM> can execute CA by using at least two CCs (cells), or use six or more CCs.

Between the radio base station <NUM> and the radio base stations <NUM> (or between two radio base stations <NUM>), wire connection (optical fiber, the X2 interface, etc.) or wireless connection may be established.

The radio base station <NUM> and the radio base stations <NUM> are each connected with a higher station apparatus <NUM>, and are connected with a core network <NUM> via the higher station apparatus <NUM>. Note that the higher station apparatus <NUM> may be, for example, an access gateway apparatus, a radio network controller (RNC), a mobility management entity (MME) and so on, but is by no means limited to these. Also, each radio base station <NUM> may be connected with higher station apparatus <NUM> via the radio base station <NUM>.

Note that the radio base station <NUM> is a radio base station having a relatively wide coverage, and may be referred to as a "macro base station," a "central node," an "eNB" (eNodeB), a "transmitting/receiving point" and so on. Also, the radio base stations <NUM> are radio base stations having local coverages, and may be referred to as "small base stations," "micro base stations," "pico base stations," "femto base stations," "HeNBs" (Home eNodeBs), "RRHs" (Remote Radio Heads), "transmitting/receiving points" and so on. The user terminals <NUM> are terminals to support various communication schemes such as LTE, LTE-A and so on, and may be either mobile communication terminals or stationary communication terminals.

In the radio communication system, as radio access schemes, OFDMA (Orthogonal Frequency Division Multiple Access) is applied to the downlink, and SC-FDMA (Single-Carrier Frequency Division Multiple Access) is applied to the uplink. OFDMA is a multi-carrier communication scheme to perform communication by dividing a frequency bandwidth into a plurality of narrow frequency bandwidths (subcarriers) and mapping data to each subcarrier. SC-FDMA is a single-carrier communication scheme to mitigate interference between terminals by dividing the system bandwidth into bands formed with one or continuous resource blocks per terminal, and allowing a plurality of terminals to use mutually different bands. Note that the uplink and downlink radio access schemes are by no means limited to the combination of these.

In the radio communication system <NUM>, a downlink shared channel (PDSCH: Physical Downlink Shared CHannel), which is used by each user terminal <NUM> on a shared basis, a broadcast channel (PBCH: Physical Broadcast CHannel), downlink L1/L2 control channels and so on are used as downlink channels. User data, higher layer control information and predetermined SIBs (System Information Blocks) are communicated in the PDSCH. Also, the MIB (Master Information Block) and so on are communicated by the PBCH.

The downlink L1/L2 control channels include a PDCCH (Physical Downlink Control CHannel), an EPDCCH (Enhanced Physical Downlink Control CHannel), a PCFICH (Physical Control Format Indicator CHannel), a PHICH (Physical Hybrid-ARQ Indicator CHannel) and so on. Downlink control information (DCI) including PDSCH and PUSCH scheduling information is communicated by the PDCCH. The number of OFDM symbols to use for the PDCCH is communicated by the PCFICH. HARQ delivery acknowledgement signals (ACKs/NACKs) in response to the PUSCH are communicated by the PHICH. The EPDCCH may be frequency-division-multiplexed with the PDSCH (downlink shared data channel) and used to communicate DCI and so on, like the PDCCH.

Also, as downlink reference signals, cell-specific reference signals (CRSs), channel state measurement reference signals (CSI-RSs: Channel State Information-Reference Signals), user-specific reference signals (DM-RSs: Demodulation Reference Signals) for use for demodulation, and other signals are included.

In the radio communication system <NUM>, an uplink shared channel (PUSCH: Physical Uplink Shared CHannel), which is used by each user terminal <NUM> on a shared basis, an uplink control channel (PUCCH: Physical Uplink Control CHannel), a random access channel (PRACH: Physical Random Access CHannel) and so on are used as uplink channels. User data and higher layer control information are communicated by the PUSCH. Also, downlink radio quality information (CQI: Channel Quality Indicator), delivery acknowledgment signals (HARQ-ACKs) and so on are communicated by the PUCCH. By means of the PRACH, random access preambles (RA preambles) for establishing connections with cells are communicated.

<FIG> is a diagram to show an example of an overall structure of a radio base station, not claimed. radio base station <NUM> has a plurality of transmitting/receiving antennas <NUM>, amplifying sections <NUM>, transmitting/receiving sections <NUM>, a baseband signal processing section <NUM>, a call processing section <NUM> and a communication path interface <NUM>. Note that the transmitting/receiving sections <NUM> are comprised of transmitting sections and receiving sections.

In the baseband signal processing section <NUM>, the user data is subjected to a PDCP (Packet Data Convergence Protocol) layer process, user data division and coupling, RLC (Radio Link Control) layer transmission processes such as RLC retransmission control, MAC (Medium Access Control) retransmission control (for example, an HARQ (Hybrid Automatic Repeat reQuest) transmission process), scheduling, transport format selection, channel coding, an inverse fast Fourier transform (IFFT) process and a precoding process, and the result is forwarded to each transmitting/receiving section <NUM>. Furthermore, downlink control signals are also subjected to transmission processes such as channel coding and an inverse fast Fourier transform, and forwarded to each transmitting/receiving section <NUM>.

Each transmitting/receiving section <NUM> converts baseband signals that are pre-coded and output from the baseband signal processing section <NUM> on a per antenna basis, into a radio frequency band. The radio frequency signals having been subjected to frequency conversion in the transmitting/receiving sections <NUM> are amplified in the amplifying sections <NUM>, and transmitted from the transmitting/receiving antennas <NUM>.

For example, the transmitting/receiving sections <NUM> transmit information about the CCs that use CA (for example, the number of CCs to be configured), information about the number of CWs in each CC, information about the UL/DL configurations to apply to TDD cells, etc. Further, the transmitting/receiving sections <NUM> can include DAIs in DCI for scheduling TDD cells and/or DCI for scheduling FDD cells and report these to the user terminals. Note that, for the transmitting/receiving sections <NUM>, transmitters/receivers, transmitting/receiving circuits or transmitting/receiving devices that can be described based on common understanding of the technical field to which the present invention pertains can be used.

Each transmitting/receiving section <NUM> receives uplink signals amplified in the amplifying sections <NUM>.

In the baseband signal processing section <NUM>, user data that is included in the uplink signals that are input is subjected to a fast Fourier transform (FFT) process, an inverse discrete Fourier transform (IDFT) process, error correction decoding, a MAC retransmission control receiving process, and RLC layer and PDCP layer receiving processes, and forwarded to the higher station apparatus <NUM> via the communication path interface <NUM>. The call processing section <NUM> performs call processing such as setting up and releasing communication channels, manages the state of the radio base station <NUM> and manages the radio resources.

The communication path interface section <NUM> transmits and receives signals to and from the higher station apparatus <NUM> via a predetermined interface. The communication path interface <NUM> transmits and receive s signals to and from neighboring radio base stations <NUM> (backhaul signaling) via an inter-base station interface (for example, optical fiber, the X2 interface, etc.).

<FIG> is a diagram to show an example of a functional structure of a radio base station according to the background example. Note that, although <FIG> primarily shows functional blocks that pertain to characteristic parts of the background example, the radio base station <NUM> has other functional blocks that are necessary for radio communication as well. As shown in <FIG>, the baseband signal processing section <NUM> has a control section (scheduler) <NUM>, a transmission signal generating section (generating section) <NUM>, a mapping section <NUM> and a received signal processing section <NUM>.

The control section (scheduler) <NUM> controls the scheduling (for example, resource allocation) of downlink data signals that are transmitted in the PDSCH and downlink control signals that are communicated in the PDCCH and/or the EPDCCH. Furthermore, the control section (scheduler) <NUM> also controls the scheduling of system information, synchronization signals, paging information, CRSs, CSI-RSs and so on.

The control section <NUM> can control the CCs and cell groups to be configured in the user terminals. Also, the control section <NUM> controls the scheduling of uplink reference signals, uplink data signals that are transmitted in the PUSCH, uplink control signals that are transmitted in the PUCCH and/or the PUSCH, random access preambles that are transmitted in the PRACH, and so on. Note that, for the control section <NUM>, a controller, a control circuit or a control device that can be described based on common understanding of the technical field to which the present invention pertains can be used.

The transmission signal generating section <NUM> generates DL signals based on commands from the control section <NUM> and outputs these signals to the mapping section <NUM>. For example, the transmission signal generating section <NUM> generates DL assignments, which report downlink signal allocation information, and UL grants, which report uplink signal allocation information, based on commands from the control section <NUM>. Further, the transmission signal generation unit <NUM> can generate downlink control information so that DAIs are included (or not included) in the DCI for scheduling the CC of each cell group. Note that, for the transmission signal generating section <NUM>, a signal generator, a signal generating circuit or a signal generating device that can be described based on common understanding of the technical field to which the present invention pertains can be used.

The mapping section <NUM> maps the downlink signals generated in the transmission signal generating section <NUM> to predetermined radio resources based on commands from the control section <NUM>, and outputs these to the transmitting/receiving sections <NUM>. Note that, for the mapping section <NUM>, mapper, a mapping circuit or a mapping device that can be described based on common understanding of the technical field to which the present invention pertains can be used.

The receiving process section <NUM> performs the receiving process (for example, demapping, demodulation, decoding and so on) of UL signals (for example, delivery acknowledgement signals (HARQ-ACKs), data signals that are transmitted in the PUSCH, and so on) transmitted from the user terminals. The processing results are output to the control section <NUM>.

Also, by using the received signals, the received signal processing section <NUM> may measure the received power (for example, the RSRP (Reference Signal Received Power)), the received quality (for example, the RSRQ (Reference Signal Received Quality)), channel states and so on. Note that the measurement results in the received signal processing section <NUM> may be output to the control section <NUM>. Note that a measurement section to perform the measurement operations may be provided apart from the received signal processing section <NUM>.

The receiving process section <NUM> can be constituted by a signal processor, a signal processing circuit or a signal processing device, and a measurer, a measurement circuit or a measurement device that can be described based on common understanding of the technical field to which the present invention pertains.

<FIG> is a diagram to show an example of an overall structure of a user terminal. A user terminal <NUM> has a plurality of transmitting/receiving antennas <NUM> for MIMO communication, amplifying sections <NUM>, transmitting/receiving sections <NUM>, a baseband signal processing section <NUM> and an application section <NUM>. Note that the transmitting/receiving sections <NUM> may be comprised of transmitting sections and receiving sections.

Radio frequency signals that are received in a plurality of transmitting/receiving antennas <NUM> are each amplified in the amplifying sections <NUM>. Each transmitting/receiving section <NUM> receives the downlink signals amplified in the amplifying sections <NUM>. The received signal is subjected to frequency conversion and converted into the baseband signal in the transmitting/receiving sections <NUM>, and output to the baseband signal processing section <NUM>.

The transmitting/receiving sections <NUM> transmit uplink control information (for example, HARQ-ACKs) that is generated based on DL signals transmitted from the radio base station. Also, the transmitting/receiving sections <NUM> can report the user terminal's capability information (capability) to the radio base station. Further, the transmitting/receiving sections <NUM> can receive information about the number of CCs to be configured, information about the CWs of each CC, the UL/DL configuration and so on. Note that, for the transmitting/receiving sections <NUM>, transmitters/receivers, transmitting/receiving circuits or transmitting/receiving devices that can be described based on common understanding of the technical field to which the present invention pertains can be used.

In the baseband signal processing section <NUM>, the baseband signal that is input is subjected to an FFT process, error correction decoding, a retransmission control receiving process, and so on. Downlink user data is forwarded to the application section <NUM>. The application section <NUM> performs processes related to higher layers above the physical layer and the MAC layer, and so on. Furthermore, in the downlink data, broadcast information is also forwarded to the application section <NUM>.

Meanwhile, uplink user data is input from the application section <NUM> to the baseband signal processing section <NUM>. The baseband signal processing section <NUM> performs a retransmission control transmission process (for example, an HARQ transmission process) , channel coding, precoding, a discrete Fourier transform (DFT) process, an IFFT process and so on, and the result is forwarded to each transmitting/receiving section <NUM>. The baseband signal that is output from the baseband signal processing section <NUM> is converted into a radio frequency bandwidth in the transmitting/receiving sections <NUM>. The radio frequency signals that are subjected to frequency conversion in the transmitting/receiving sections <NUM> are amplified in the amplifying sections <NUM>, and transmitted from the transmitting/receiving antennas <NUM>.

<FIG> is a diagram to show an example of a functional structure of a user terminal. Note that, although <FIG> primarily shows functional blocks that pertain to characteristic parts of the present embodiment, the user terminal <NUM> has other functional blocks that are necessary for radio communication as well. As shown in <FIG>, the baseband signal processing section <NUM> provided in the user terminal <NUM> has a control section <NUM>, a transmission signal generating section <NUM>, a mapping section <NUM>, a received signal processing section <NUM> and a decision section <NUM>.

The control section <NUM> can control the transmission signal generating section <NUM>, the mapping section <NUM> and the received signal processing section <NUM>. For example, the control section <NUM> acquires the downlink control signals (signals transmitted in the PDCCH/EPDCCH) and downlink data signals (signals transmitted in the PDSCH) transmitted from the radio base station <NUM>, from the received signal processing section <NUM>. The control section <NUM> controls the generation/transmission of uplink control signals (for example, HARQ-ACKs and so on) and uplink data based on downlink control information (UL grants), the result of deciding whether or not retransmission control is necessary for downlink data, and so on.

Further, the control section <NUM> can control uplink control information transmission to use an uplink control channel of a SCell (PUCCH on SCell) and uplink control information to use an uplink shared channel (UCI on PUSCH) in each of a plurality of cell groups, each including at least one CC (see <FIG>). Further, the control section <NUM> can control HARQ transmission by applying an HARQ timing based on the FDD scheme to the first cell group, and control HARQ transmission by applying an HARQ timing based on the TDD scheme to the second cell group.

Furthermore, the control section <NUM> can control uplink control information transmission to use an uplink control channel (PUCCH on SCell) in each of a plurality of cell groups, each including at least one CC, and control uplink control information to use an uplink shared channel (UCI on PUSCH) across a plurality of cell groups (see <FIG>).

Further, the control section <NUM> can perform control so that HARQ for the second cell group is transmitted using an uplink shared channel of a CC in the first cell group. In this case, the control section <NUM> can control the number of HARQ bits based on the number of DL subframes corresponding to the uplink shared channel. Alternatively, the control section <NUM> may control the number of HARQ bits based on the number of DL subframes to be scheduled (for example, the DAI value included in downlink control information). Alternatively, the control section <NUM> may perform control so that the uplink control information transmission using the uplink shared channel is not performed in the CCs of the first cell group.

For the control section <NUM>, a controller, a control circuit or a control device that can be described based on common understanding of the technical field to which the present invention pertains can be used.

The transmission signal generating section <NUM> generates UL signals based on commands from the control section <NUM>, and outputs these signals to the mapping section <NUM>. For example, the transmission signal generating section <NUM> generates uplink control signals such as delivery acknowledgement signals (HARQ-ACKs), channel state information (CSI) and so on, based on commands from the control section <NUM>.

Also, the transmission signal generating section <NUM> generates uplink data signals based on commands from the control section <NUM>. For example, when a UL grant is included in a downlink control signal that is reported from the radio base station <NUM>, the control section <NUM> commands the transmission signal generating section <NUM> to generate an uplink data signal. Also, the transmission signal generating section <NUM> generates UL signals from the decisions (ACKs/NACKs) made in the decision section <NUM>. For the transmission signal generating section <NUM>, a signal generator, a signal generating circuit or a signal generating device that can be described based on common understanding of the technical field to which the present invention pertains can be used.

The mapping section <NUM> maps the uplink signals (uplink control signals and/or uplink data) generated in the transmission signal generating section <NUM> to radio resources based on commands from the control section <NUM>, and output the result to the transmitting/receiving sections <NUM>. For the mapping section <NUM>, mapper, a mapping circuit or a mapping device that can be described based on common understanding of the technical field to which the present invention pertains can be used.

The received signal processing section <NUM> performs the receiving process (for example, demapping, demodulation, decoding and so on) of the DL signals (for example, downlink control signals that are transmitted from the radio base station in the PDCCH/EPDCCH, downlink data signals transmitted in the PDSCH, and so on). The received signal processing section <NUM> outputs the information received from the radio base station <NUM>, to the control section <NUM> and the decision section <NUM>. Note that, for the received signal processing section <NUM>, a signal processor/measurer, a signal processing/measurement circuit or a signal processing/measurement device that can be described based on common understanding of the technical field to which the present invention pertains can be used. Also, the received signal processing section <NUM> can constitute the receiving section.

The decision section <NUM> makes retransmission control decisions (ACKs/NACKs) based on the decoding results in the receiving process section <NUM>, and, furthermore, outputs the results to the control section <NUM>. For the decision section <NUM>, a decision maker, a decision making circuit or a decision making device that can be described based on common understanding of the technical field to which the present invention pertains can be used.

Note that the block diagrams that have been used to describe the above embodiments show blocks in functional units. These functional blocks (components) may be implemented in arbitrary combinations of hardware and software. Also, the means for implementing each functional block is not particularly limited. That is, each functional block may be implemented with one physically-integrated device, or may be implemented by connecting two physically-separate devices via radio or wire and using these multiple devices.

For example, part or all of the functions of radio base stations <NUM> and user terminals <NUM> may be implemented using hardware such as an ASIC (Application-Specific Integrated Circuit), a PLD (Programmable Logic Device), an FPGA (Field Programmable Gate Array), and so on. Also, the radio base stations <NUM> and user terminals <NUM> may be implemented with a computer device that includes a processor (CPU), a communication interface for connecting with networks, a memory and a computer-readable storage medium that holds programs.

Here, the processor and the memory are connected with a bus for communicating information. Also, the computer-readable recording medium is a storage medium such as, for example, a flexible disk, an opto-magnetic disk, a ROM, an EPROM, a CD-ROM, a RAM, a hard disk and so on. Also, the programs may be transmitted from the network through, for example, electric communication channels. Also, the radio base stations <NUM> and user terminals <NUM> may include input devices such as input keys and output devices such as displays.

Claim 1:
A terminal (<NUM>) configured to communicate with a radio base station by using carrier aggregation, the terminal comprising:
a receiving section (<NUM>) configured to receive a downlink, DL, signal transmitted from the radio base station and including downlink control information, DCI, the DCI including an uplink Downlink Assignment Index, DAI, and being for scheduling a physical uplink shared channel, PUSCH, in a component carrier, CC, of one of a plurality of cell groups;
a control section (<NUM>) configured to:
control transmission of uplink control information, UCI, using an uplink control channel and the transmission of the UCI using an uplink shared channel in each of the plurality of cell groups, each cell group including at least one CC,
determine a number of bits for HARQ-ACK to be transmitted in a PUSCH, based on the DAI, and
allocate HARQ-ACK bits to a PUSCH of a CC in one cell group; and
a transmission section (<NUM>) configured to transmit the HARQ-ACK,
wherein the terminal is configured to perform a receiving process of a physical downlink control channel on the assumption that an uplink DAI is included in DCI transmitted from each cell group, and
the uplink DAI indicates information about a number of DL subframes to be scheduled.