Patent Description:
In the UMTS (Universal Mobile Telecommunication 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>). The specifications of LTE-advanced (also referred to as LTE "Rel. <NUM>," "Rel. <NUM>" or "Rel. <NUM>") have been drafted for the purpose of further broadbandization and speed-up from LTE (also referred to as "LTE Rel. <NUM>"), and a successor system (LTE of Rel. <NUM> and later versions) is also under study.

Carrier aggregation (CA) to integrate multiple component carriers (CC) is introduced in LTE Rel. <NUM>/<NUM> in order to achieve broadbandization. Each CC is configured with the system bandwidth of LTE Rel. <NUM> as one unit. In addition, in CA, multiple CCs under the same radio base station (eNB: eNodeB) are configured in a user terminal (UE: User Equipment).

On the other hand, in LTE Rel. <NUM>, dual connectivity (DC), in which multiple cell groups (CG) formed by different radio base stations are configured in a user terminal, is also introduced. Each cell group consists of at least one cell (CC). In DC, since multiple CCs of different radio base stations are integrated, DC is also referred to as "inter-eNB CA.

In above-mentioned LTE Rel. <NUM> to <NUM>, the transmission time intervals (TTIs) that are applied to DL transmission and UL transmission between radio base stations and user terminals are configured to one ms and controlled. Transmission time intervals are also referred to as "communication time intervals," and a TTI in LTE systems (Rel. <NUM> to <NUM>) is also referred to as a "subframe duration.

To facilitate error-correction by use of HARQ-ACK, transmission within TTIs needs to be identified. Therefore, Non-Patent Literature <NUM> discusses some remaining issues on dynamic HARQ-ACK codebook determination. More specifically, it outlines a counter DAI based solution for dynamic HARQ-ACK codebook, wherein counter DAI is incremental in frequency-first-time-second manner for TDD and is incremental in carrier index for FDD. Further, Non-Patent Literature <NUM> discusses a possible HARQ-ACK payload adaptation for LTE Rel. More specifically, it considers bundling based HARQ-ACK payload reduction by reducing the number of HARQ-ACK feedback bits by applying HARQ-ACK bundling, and scheduling based HARQ-ACK payload adaptation by reducing the number of HARQ-ACK feedback bits associated with non-scheduled cells/subframes. Also, Non-Patent Literature <NUM> discusses HARQ-ACK codebook determination for enhanced carrier aggregation (eCA). More specifically, it considers approaches where the probability of error is low, no or only a limited scheduling restriction is imposed, HARQ-ACK overhead is minimized and no negative impact on HARQ-ACK BLERR is caused.

In radio communication systems after LTE Rel. <NUM> (for example, <NUM>), it is assumed that communication in a high frequency band such as several tens of GHz, or communication with a relatively small amount of data such as IoT (Internet of Things), MTC (Machine Type Communication), M2M (Machine To Machine) or the like is performed. The demand for D2D (Device To Device) and V2V (Vehicular To Vehicular) communication, which requires low-delay communication, is also increasing.

Reduction of communication delay (latency reduction) is being studied in order to provide sufficient communication services in such future radio communication systems. For example, a study is in progress to make the transmission time intervals (TTIs), which are the minimum unit of scheduling, shorter than the one-ms TTIs of existing LTE systems (LTE Rel. <NUM> to <NUM>), and communicate by using these TTIs (may be referred to as, for example, "shortened TTIs").

Also, although, in Rel. <NUM> or earlier versions, the maximum number of CCs that can be configured in CA is <NUM>, the number of CCs that can be configured in CA is expected to be increased (to <NUM> CCs, for example) in Rel. <NUM> and later versions. In this case, it may be possible that a user terminal connects with a plurality of cells using different TTIs and performs communication (for example, CA and/or DC).

Meanwhile, when communication is made using multiple CCs with different TTI durations, how to control communication is the problem. For example, when a radio base station and/or a user terminal communicate using a plurality of cells having different TTI durations, how to control the transmission/receiving timing in each CC becomes the problem.

The present invention has been made in view of the above points, and it is therefore an object of the present invention to provide a user terminal, a radio base station, and a radio communication method that allow adequate communication to be carried out even when a plurality of CCs with varying TTI durations are used.

A user terminal is provided according to independent claim <NUM>. A base station is provided according to independent claim <NUM>. A radio communication method is provided according to independent claim <NUM>. This description explains how the present invention may be carried out.

According to the present invention, communication can be performed appropriately even when a plurality of CCs having different TTI durations are used.

<FIG> is a diagram to explain an example of transmission time intervals (TTIs) in existing systems (LTE Rel. <NUM> to <NUM>). As shown in <FIG>, a TTI in LTE Rel. <NUM> to <NUM> (hereinafter referred to as a "normal TTI") has a time duration of one ms. A normal TTI is also referred to as a "subframe," and is comprised of two time slots. A TTI is one channel-coded data packet (transport block) transmission time unit, and is the processing unit in scheduling, link adaptation, etc..

As shown in <FIG>, when normal cyclic prefixes (CPs) are used in the downlink (DL), a normal TTI includes <NUM> OFDM (Orthogonal Frequency Division Multiplexing) symbols (seven OFDM symbols per slot). Each OFDM symbol has a time duration (symbol duration) of <NUM>, and a normal CP of <NUM> is appended. Since the symbol duration and the subcarrier period are in reciprocal relationship to each other, the subcarrier period is <NUM> when the symbol duration <NUM>.

Also, when normal cyclic prefixes (CPs) are used in the uplink (UL), a normal TTI is configured to include <NUM> SC-FDMA (Single Carrier Frequency Division Multiple Access) symbols (seven SC-FDMA symbols per slot). Each SC-FDMA symbol has a time duration (symbol duration) of <NUM>, and a normal CP of <NUM> is appended. Since the symbol duration and the subcarrier period are in reciprocal relationship to each other, the subcarrier period is <NUM> when the symbol duration <NUM>.

Incidentally, when extended CPs are used, a normal TTI may include <NUM> OFDM symbols (or <NUM> SC-FDMA symbols). In this case, each OFDM symbol (or each SC-FDMA symbol) has a time duration of <NUM>, and an extended CP of <NUM> is appended.

On the other hand, in future radio communication systems such as Rel. <NUM> and later LTE and <NUM>, a radio interface that is suitable for high frequency bands such as several tens of GHz or the like and a radio interface that minimizes delay for IoT (Internet of Things), MTC (Machine Type Communication), M2M (Machine To Machine), D2D (Device To Device) and V2V (Vehicular To Vehicular) services are in demand.

Therefore, in future communication systems, it may be possible that communication is performed using shortened TTIs, which are TTIs shorter than one ms (see <FIG> shows a cell (CC #<NUM>) using normal TTIs (one ms) and a cell (CC #<NUM>) using shortened TTIs. Also, when shortened TTIs are used, it may be possible to change the subcarrier period from the subcarriers of normal TTIs (for example, the subcarrier period may be expanded).

When TTIs of a shorter time length than normal TTIs (hereinafter referred to as "shortened TTIs") are used, the time margin for processing (for example, encoding and decoding) in the user terminal and the radio base station increases, so that the processing delay can be reduced. Also, when shortened TTIs are used, it is possible to increase the number of user terminals that can be accommodated per unit time (for example, one ms). Below, the configuration of shortened TTIs and so on will be explained.

A configuration example of shortened TTIs will be described with reference to <FIG>. As shown in <FIG>, shortened TTIs have a time duration (TTI duration) shorter than one ms. A shortened TTI may be one TTI duration or multiple TTI durations, whose multiples are one ms, such as <NUM>, <NUM>, <NUM> and <NUM>, for example. Alternatively, when normal CPs are used, a normal TTI contains <NUM> symbols, so that one TTI duration or multiple TTI durations, whose multiples are integral multiples of <NUM>/<NUM>, such as <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM> and <NUM>/<NUM>, may be used. Also, when extended CPs are used, a normal TTI contains <NUM> symbols, so that one TTI duration or multiple TTI durations, whose multiples are integral multiples of <NUM>/<NUM>, such as <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM> and <NUM>/<NUM>, may be used. Also in shortened TTIs, similar to conventional LTE, whether to use normal CPs or use extended CPs can be configured with higher layer signaling such as broadcast information and RRC signaling. By this means, it is possible to introduce shortened TTIs, while maintaining compatibility (synchronization) with one-ms normal TTIs.

Note that, although <FIG> illustrate example cases of using normal CPs, the present invention is not limited to these. A shortened TTI needs only be a shorter time duration than a normal TTI, and the number of symbols in the shortened TTI, the duration of symbols, the duration of CPs and suchlike configurations can be determined freely. Also, although examples will be described below in which OFDM symbols are used in the DL and SC-FDMA symbols are used in the UL, the present invention is not limited thereto.

<FIG> is a diagram to show a first configuration example of shortened TTIs. As shown in <FIG>, in the first configuration example, a shortened TTI is comprised of <NUM> OFDM symbols (or SC-FDMA symbols), which is equal in number to a normal TTI, and each OFDM symbol (each SC-FDMA symbol) has a symbol duration shorter than the symbol duration (= <NUM>) of the normal TTI.

As shown in <FIG>, when maintaining the number of symbols in a normal TTI and shortening the symbol duration, the physical layer signal configuration (arrangement of REs, etc.) of normal TTIs can be reused. In addition, when maintaining the number of symbols in a normal TTI, it is possible to include, in a shortened TTI, the same amount of information (the same amount of bits) as in a normal TTI. On the other hand, since the symbol time duration differs from that of normal TTI symbols, it is difficult, as shown in FIG. 2A, to frequency-multiplex a signal with shortened TTIs and a signal with normal TTIs in the same system band (or the cell, the CC, etc.).

Also, since the symbol duration and the subcarrier period are each the reciprocal of the other, as shown in <FIG>, when shortening the symbol duration, the subcarrier period is wider than the <NUM>-kHz subcarrier period of normal TTIs. When the subcarrier period becomes wider, it is possible to effectively suppress the inter-channel interference caused by the Doppler shift when the user terminal moves and the communication quality degradation due to phase noise in the receiver of the user terminal. In particular, in high frequency bands such as several tens of GHz, the deterioration of communication quality can be effectively suppressed by expanding the subcarrier period.

<FIG> is a diagram to show a second configuration example of a shortened TTI. As shown in <FIG>, according to the second configuration example, a shortened TTI is comprised of a smaller number of OFDM symbols (or SC-FDMA symbols) than a normal TTI, and each OFDM symbol (each SC-FDMA symbol) has the same symbol duration (= <NUM>) as a normal TTI. In this case, the shortened TTI can be configured using symbol units in a normal TTI. For example, a shortened TTI can be formed by using some of the <NUM> symbols included in one subframe. In <FIG>, a shortened TTI is comprised of seven OFDM symbols (SC-FDMA symbols), which is half of a normal TTI.

As shown in <FIG>, when reducing the symbol duration and reducing number of symbols, the amount of information (the amount of bits) included in a shortened TTI can be reduced lower than in a normal TTI. Therefore, the user terminal can perform the receiving process (for example, demodulation, decoding, etc.) of the information included in a shortened TTI in a shorter time than a normal TTI, and therefore the processing delay can be shortened. Also, since the shortened-TTI signal shown in <FIG> and a normal-TTI signal can be frequency-multiplexed within the same system band (or the cell, the CC, etc.), compatibility with normal TTIs can be maintained.

An example of the configuration of shortened TTIs will be described. When shortened TTIs are used, it is also possible to configure both normal TTIs and shortened TTIs in a user terminal in order to have compatibility with existing systems (LTE Rel. <NUM> to <NUM>). <FIG> show an example of the configuration of normal TTIs and shortened TTIs. Note that <FIG> are merely examples, and these are by no means limiting.

<FIG> is a diagram to show an example of the first configuration of shortened TTIs. As shown in <FIG>, normal TTIs and shortened TTIs may coexist in time in the same component carrier (CC) (frequency domain). To be more specific, shortened TTIs may be configured in specific subframes (or specific radio frames) of the same CC. For example, in <FIG>, shortened TTIs are configured in five consecutive subframes in the same CC, and normal TTIs are configured in the other subframes. For example, as specific subframes, subframes that can be configured as MBSFN subframes, or subframes that include (or do not include) specific signals such as the MIB or synchronization channels may be used. The number and positions of subframes where shortened TTIs are configured are not limited to those shown in <FIG>.

<FIG> is a diagram to show an example of a second configuration of shortened TTIs. Carrier aggregation (CA) or dual connectivity (DC) may be performed by integrating CCs with normal TTIs and CCs with shortened TTIs, as shown in <FIG>. To be more specific, shortened TTIs may be configured in specific CCs (more specifically in the DL and/or the UL of particular CCs). For example, in <FIG>, shortened TTIs are configured in the DL of a particular CC and normal TTIs are configured in the DL and UL of another CC. Note that the number and locations of CCs where shortened TTIs are configured are not limited to those shown in <FIG>.

In the case of CA, shortened TTIs may also be configured in specific CCs (the primary (P) cell and/or secondary (S) cells) of the same radio base station. On the other hand, in the case of DC, shortened TTIs may be configured in specific CCs (P cell and/or S cells) in the master cell group (MCG) formed by the first radio base station, or shortened TTIs may be configured in specific CCs (primary secondary (PS) cells and/or S cells) in a secondary cell group (SCG) formed by a second radio base station.

<FIG> is a diagram to show an example of a third configuration of shortened TTIs. As shown in <FIG>, shortened TTIs may be configured in either the DL or the UL. For example, in <FIG>, a case is shown in which, in a TDD system, normal TTIs are configured in the UL and shortened TTIs are configured in the DL.

Also, specific DL or UL channels or signals may be assigned to (configured in) shortened TTIs. For example, an uplink control channel (PUCCH: Physical Uplink Control Channel) may be allocated to normal TTIs, and an uplink shared channel (PUSCH: Physical Uplink Shared Channel) may be allocated to shortened TTIs. In this case, for example, the user terminal transmits the PUCCH in normal TTIs and transmits the PUSCH in shortened TTIs.

Also, a multiple-access scheme that is different from OFDM (or SC-FDMA), which is the multiple-access scheme of LTE Rel. <NUM> to <NUM>, may be assigned to (configured in) shortened TTIs.

As mentioned above, when cells using shortened TTIs are configured in a user terminal, the user terminal can configure (and/or detect) the shortened TTIs based on implicit or explicit reporting from the radio base station. Hereinafter, as examples of shortened TTI reporting applicable to this embodiment, a case of (<NUM>) implicit reporting, or cases of using at least one of (<NUM>) broadcast information or RRC (Radio Resource Control) signaling, (<NUM>) MAC (Medium Access Control) signaling and (<NUM>) PHY (Physical) signaling will be described.

For example, it is assumed that control information (DCI) for assigning transmission or reception in normal TTIs and shortened TTIs includes different information elements, and, (<NUM>-<NUM>) when the user terminal detects control information (DCI) including an information element that assigns transmission and reception in shortened TTIs, the user terminal identifies a predetermined time period including the timing where the PDCCH/EPDCCH is detected as a shortened TTI. The user terminal can blind-decode control information (DCI) for assigning transmission or reception in both normal TTIs and shortened TTIs in the PDCCH/EPDCCH. Alternatively, (<NUM>-<NUM>) when the user terminal detects control information (DCI) including an information element that assigns transmission/reception in shortened TTIs, the user terminal may identify a predetermined time period, in which the timing the PDSCH or the PUSCH scheduled by the PDCCH/EPDCCH (downlink control information (DCI) communicated in the PDCCH/EPDCCH) is transmitted/received is included, as a shortened TTI. Alternatively, (<NUM>-<NUM>) when a user terminal detects DCI including an information element that assigns transmission/reception in shortened TTIs, the user terminal may identify a predetermined time period, in which the timing to transmit or receive retransmission control information for the PDSCH or the PUSCH scheduled by the PDCCH/EPDCCH (DCI communicated in the PDCCH/EPDCCH) is included, as a shortened TTI.

Further, the user terminal may detect shortened TTIs based on the state of the user terminal (for example, the idle state or the connected state). For example, if the user terminal is in the idle state, the user terminal may identify all the TTIs as normal TTIs and blind decode only the PDCCHs included in the first to fourth symbols of the normal TTIs of one ms. Also, if the user terminal is in the connected state, the user terminal may configure (and/or detect) shortened TTIs based on the reporting of at least one of (<NUM>) to (<NUM>) described above as examples.

As described above, in future radio communication, it is assumed that communication is performed by applying shortened TTIs, which are transmission time intervals reduced to be shorter than normal TTIs, to UL transmission and/or DL transmission. Further, in the future radio communication, as shown in <FIG>, it may be possible that communication (for example, CA or DC) is performed using a plurality of cells having different TTI durations. However, in such a case, how to control the communication method (for example, transmission timing, receiving timing, etc.) in UL communication and/or DL communication is the problem.

Therefore, as one aspect of the present invention, assuming the case where the user terminal communicates using a plurality of cells (or CCs, carriers, etc.) having different TTI durations, the inventors of the present invention have come up with the idea of configuring CC groups according to the TTI durations of CCs and controlling UL transmission and/or DL transmission on a per CC group basis. By doing so, the data communication rate in the user terminal can be improved and the latency can be reduced.

A CC group can be the transmission timing control unit in UL transmission and/or DL transmission. For example, when CA is applied, based on the assumption that a PUCCH group is a CC group, PUCCH groups can be formed with CCs with the same TTI duration. Also, when DC is applied, based on the assumption that a cell group is a CC group, cell groups can be formed with CCs with the same TTI duration.

When CA is applied, a user terminal can apply a transmission method used in CA in existing systems for each PUCCH group comprised of CCs of the same TTI duration. Also, when DC is applied, it is possible to apply a communication control method used in DC by forming cell groups respectively configured by different radio base stations with CC having the same TTI duration.

Note that a PUCCH group is a group including one or more CCs (cells), and refers to a group formed with CCs that transmit uplink control information (UCI) using the PUCCH of a predetermined CC. Examples of uplink control information include HARQ-ACKs, channel state information (CSI), and the like. The CC where the PUCCH is configured among the CCs included in a PUCCH group is also referred to as the "PUCCH cell," the "PUCCH CC," or the "PUCCH Cell. " For example, when the PUCCH cell is a secondary cell (SCell), the user terminal transmits the PUCCH in the CC that serves as the PUCCH SCell (for example, the SCell with the smallest cell index in the PUCCH group). In this manner, by feeding back uplink control information (HARQ-ACK, etc.) in response to DL data transmitted in a plurality of CCs forming a cell group in a predetermined CC, the effect of single carrier nature can be obtained.

In addition, as another aspect of the present invention, the inventors of the present invention have found that, when a user terminal communicates using a plurality of cells having different TTI durations, UL transmission and/or DL transmission can be controlled by forming the same CC group with a plurality of CCs having different TTI durations.

For example, if a CC group is formed with multiple CCs with different TTI durations, it is possible to perform control so that uplink control information corresponding to each CC is transmitted at different timings, using a predetermined CC, according to the TTI durations of CCs. As a result, the data communication rate in the user terminal can be improved and the latency can be reduced, and, furthermore, it is possible to transmit uplink control information and so on in one UL (CC), even if the user terminal connects with multiple CCs with different TTI durations.

Now, the present embodiment will be described below in detail. In the following description, a first TTI duration (<NUM>) and a second TTI duration (<NUM>) will be explained as TTI durations of examples, but the applicable TTI durations and TTI duration types are not limited to these. TTI having the first TTI duration may be referred to as "regular TTIs," "normal TTIs," "long TTIs," "regular subframes," "normal subframes," or "long subframes. " TTIs having the second TTI duration may be referred to as "shortened TTIs," "short TTIs," "shortened subframes," or "short subframes. " In the following description, an LTE system will be shown as an example, but the present embodiment is not limited to this, and any system can be applied as long as it uses a plurality of CCs of varying TTI durations. Further, a plurality of examples described below can be implemented in appropriate combination.

In the first embodiment, which is useful for understanding the claims, a case where CC groups are configured according to the TTI durations of CCs will be explained. In the following description, it is shown that two CC groups are configured, but the number of CC groups and the number of CCs forming each CC group are not particularly limited. In addition, each CC can use FDD or TDD as appropriate.

<FIG> shows an example in which two CC groups (first CC group and second CC group) are configured according to the TTI durations of CCs. The first CC group (CC group #<NUM>) is comprised of CC #<NUM> to CC #<NUM> to which the first TTI duration is applied, and the second CC group (CC group #<NUM>) is comprised of CC #<NUM> to CC #<NUM> to which the second TTI duration is applied. Here, it is shown that the first TTI duration is <NUM> and the second TTI duration is <NUM>, but the TTI durations to apply to each CC group (CC) are not limited to these.

For example, when CA is employed, it is possible to control UL transmission and/or DL transmission per PUCCH group, with the first CC group as the primary PUCCH group and the second CC group as a secondary PUCCH group. The TTI duration of each PUCCH group can be included in higher layer signaling, such as RRC signaling, which reports configuration and reconfiguration of CC groups.

Also, when DC is applied, it is possible to control UL transmission and/or DL transmission per cell group, with the first CC group as the primary cell group (master cell group (MCG)) and the second CC group as a secondary cell group (SCG). The TTI duration of each cell group can be included in higher layer signaling, such as RRC signaling, which reports configuration and reconfiguration DC and/or cell groups. This higher layer signaling may be transmitted and received only from the CCs belonging to the MCG.

When DC is applied, the user terminal may communicate with different radio base stations between the MCG and SCGs. To realize this, backhaul signaling may be introduced, in which the MeNB controlling the MCG and the SeNB controlling the SCG report the TTI duration of each cell group to each other. For example, signaling may be introduced in which the MeNB specifies to the SeNB the TTI duration which the user terminal uses when communicating with the SCG. This allows the SeNB to recognize the TTI duration used by the user terminal when communicating with the SCG, which is configured in the user terminal by the MeNB via higher layer signaling, so that the SeNB can properly communicate with the user terminal.

Signaling may also be introduced in which one or more TTI durations which the user terminal can use when communicating with the SCG are reported from the SeNB to the MeNB. As a result, the MeNB can recognize the TTI duration that the SeNB can use for communication with the user terminal, and the MeNB can select an appropriate TTI duration out of the TTI durations that the SeNB can use for communication and configure it in the user terminal. If TTI durations that can be used when the user terminal communicates with the SCG are not reported from SeNB to MeNB, the MeNB may recognize that the <NUM>-ms normal TTI, specified in conventional LTE, is the only TTI duration that can be configured in the SeNB.

In this way, it is possible to simplify the control of transmission/receiving timings by forming one CC group with only CCs of the same TTI duration and controlling, individually, scheduling and/or HARQ feedback on a per CC group basis. <FIG> shows an example of controlling HARQ-ACK feedback timing per CC group.

<FIG> shows a case where the transmission timing of uplink control information corresponding to each CC is controlled in TTI units in each CC group. To be more specific, in the case shown in <FIG>, when DL data (for example, PDSCH) is received in each CC, the user terminal transmits HARQ-ACKs (A/Ns) in response to the DL data a predetermined number of TTIs later. In this case, the A/Ns corresponding to each CC can be multiplexed and transmitted on the uplink control channel of a specific CC (for example, PCell, PSCell, PUCCH SCell, etc.).

In the case shown in <FIG>, in the first CC group and the second CC group, the user terminal feeds back uplink control information four TTIs after DL data is received. In this case, even when the first CC group and the second CC group are scheduled at the same timing, the feedback timing in the second CC group where the TTI duration is shorter arrives earlier. Note that the feedback timing is not limited to four TTIs later. Also, different TTIs may be configured as the feedback timings of the first CC group and the second CC group.

Alternatively, when receiving downlink control information (for example, UL grant) in each CC group, the user terminal can transmit uplink data (for example, PUSCH) in response to the UL grant a predetermined number of TTIs later (for example, four TTIs later). Of course, different TTIs may be configured between the first CC group and the second CC group as uplink data transmission timings.

Thus, the user terminal performs scheduling and/or HARQ timing control independently for each CC group. Also, scheduling and/or HARQ timing control can be configured based on the TTI duration in each CC group (the TTI durations of CCs forming each CC group). Also, after uplink data is transmitted from the user terminal, the period until HARQ transmitted from the radio base station arrives can be a predetermined number of TTIs.

Also, cross-carrier scheduling when CA is applied, transmission of uplink control information (UCI on PUSCH) using an uplink data channel (PUSCH), CSI measurement/reporting, and so on can also be controlled on a per CC group basis. Also, the timing to apply cell (CC)-configuring activation/de-activation commands may also be configured per CC group based on the TTI duration (for example, in proportion to the TTI duration). The count of the number of subframes in the activation/deactivation timer and the PHR reporting timer controlled under the MAC layer may also be based on the configured TTI duration.

By controlling communication on a per CC group basis in this way, it is possible to communicate using a large number of CCs, and at the same time, it is possible to obtain an advantage by shortening the TTI duration, so that delay can be reduced by applying CC groups with short TTI durations and increased peak rates can be achieved by applying CA or DC.

The radio base station can report (configure) information on CC groups and/or the TTI duration of each CC group (the TTI durations of CCs included in CC groups) to the user terminal.

For example, the radio base station can report CC group information, including at least one of information on the CC groups configured, information on the TTI durations of the CC groups, information on the CCs included in the CC groups configured and information on the TTI duration of the CCs, to the user terminal. In this case, the radio base station can report the CC group information to the user terminal by higher layer signaling, downlink control information or a combination thereof.

Further, the radio base station can report (configure) the CC groups as the cell groups when DC is applied or as the PUCCH groups when CA is applied, to the user terminal. Alternatively, the radio base station reports only the information of CC groups, and the PUCCH groups and the cell groups may be configured on the user terminal side based on the information reported at the time CA and/or DC are applied.

Further, the TTI duration that is configured in the user terminal may be made CC group-specific information or may be made CC-specific information. When the TTI duration is made CC-specific information, the user terminal can assume that all the CCs in the same CC group have the same TTI duration.

In a second example, the UL transmission power configuration method for use when multiple CC groups (here, the first CC group and the second CC group) are configured according to the TTI durations of CCs will be described.

When CC groups are configured according to the TTI durations of CC as shown in <FIG> above, UL transmission is performed simultaneously between CCs with different TTI durations.

In this case, if the TTI duration differs between a plurality of UL cells (CCs), there is a possibility that the transmission period does not necessarily match between the cells. That is, if transmission power control that is based on the premise that the transmission period matches as in uplink CA in existing systems is applied, on an as-is basis, to UL transmission using multiple CCs (CC groups) with different TTI durations, there is a possibility that a problem arises.

Therefore, in the second example, if the TTI duration differs between UL cells, it is effective to apply a power control method in which power is preferentially configured for cells with early transmission timings. For example, when DC is used, power control can be performed among UL cells having different TTI durations using UL transmission power control (for example, DC PC mode <NUM>) that is applied when cell groups are asynchronous.

To be more specific, when the TTI duration differs between CCs, it is possible to configure the minimum guaranteed power to assign to each CC, and assign the remaining power to CCs with earlier transmission timings. The remaining power (surplus power) corresponds to the surplus power that is left after the minimum guaranteed power of each CC is subtracted from the maximum transmission power (Pcmax) of the user terminal.

Alternatively, if the TTI duration differs between UL cells, a configuration using DC PC mode <NUM> may be adopted only when the transmission starting timing differs by more than a predetermined value (for example, <NUM>) between the cells. For example, when the transmission timings match between the cells, the user terminal applies the power control for UL-CA, or applies the UL transmit power control (for example, DC PC mode <NUM>) that is used when cell groups are synchronous in DC. In this case, the user terminal can determine the transmission power to allocate to each cell according to the priority that is configured based on the channel type and/or the content of uplink control information.

When the transmission timings do not match between cells, the user terminal can apply the UL transmission power control that is used when cell groups are asynchronous in DC (for example, DC PC mode <NUM>). Whether the transmission timings do not match between cells can be judged based on, for example, whether or not the transmission starting timings differ by more than a predetermined value between the cells.

<FIG> shows an example of a case in which UL transmission (UL-CA) is made using a first CC (UL #<NUM>) to which a first TTI duration (for example, one ms) is applied and a second CC (UL #<NUM>) to which a second TTI duration (for example, <NUM>) is applied. Here, assume the case where, between the two TTIs (subframes) of the second CC overlapping the TTIs (subframes) of the first CC, the transmission-starting timing of the first-half TTI matches the transmission-starting timing of the first CC's TTI.

When UL transmission is performed in the TTI of the first CC and the first-half TTI of the second CC separately, the user terminal determines the UL transmission power in each CC by applying UL-CA power control or by applying DC PC mode <NUM>. In this case, the user terminal can determine the UL transmission power of each CC based on the channel type transmitted in each CC and/or the presence or the absence of uplink control information.

On the other hand, when UL transmission is performed in the TTI of the first CC and the second-half TTI of the second CC separately, the user terminal can determine the UL transmission power of each CC by applying DC PC mode <NUM>. In this case, the user terminal can preferentially allocate transmission power to the first TTI (long TTI) of the first CC, where the transmission starting timing is earlier. Also, in the case where the CC groups are asynchronous (for example, when asynchronous DC is applied), a configuration in which DC PC mode <NUM> is applied may be adopted.

Thus, when multiple CC groups are configured according to the TTI durations of CCs, the configuration of UL transmission power is controlled based on the transmission starting timing, and this makes it possible to properly determine the UL transmission power even if UL transmission overlaps between CCs with different TTI durations.

In a third example, a case where counter DAIs (C-DAIs) and/or total DAIs (T-DAIs) are applied to CC groups that are configured according to the TTI duration will be explained. First, counter DAIs and total DAIs will be explained below.

In existing systems (LTE Rel. <NUM> to <NUM>), as mentioned earlier, the codebook size of HARQ-ACKs (ACK/NACK bit sequence) to be transmitted on the PUCCH is determined semi-statically based on information reported by higher layer signaling.

In the case of using FDD, the overall A/N bit size is determined based on the number of CCs configured by RRC signaling and the TM (Transmission Mode), which indicates whether MIMO (Multiple Input Multiple Output) is applicable in each CC. In a certain DL subframe, if a DL assignment is detected in at least one SCell, the user terminal feeds back A/Ns in all the CCs configured in the UL subframe a predetermined period later (for example, four ms later). Note that a NACK is generated for a cell where DL data assignment is not detected in the DL subframe (cell where PDSCH scheduling could not be identified).

When TDD is used, in addition to the above case using FDD, the overall size of the A/N bit sequence transmitted on the PUCCH is determined based on the number of DL subframes addressed by A/Ns per UL subframe. When the user terminal using TDD detects at least one DL assignment in the bundling window, the user terminal feeds back A/Ns for all the configured CCs using the PUCCH in the UL subframe a predetermined period later (for example, (n + k) ms later). Note that a NACK is generated for cells and/or subframes (cell/subframe where no scheduled PDSCH is identified) for which DL data assignment was not detected in the bundling window.

"Bundling window" refers to a group of DL subframes subject to A/N feedback in a certain UL subframe (including special subframes). The bundling window is specified by the UL/DL configuration of TDD. A user terminal that communicates using TDD is controlled to transmit an A/N for a DL signal transmitted in a predetermined subframe in a predetermined UL subframe based on the bundling window.

For example, suppose a case where four DL subframes are included in the bundling window corresponding to a certain UL subframe and one DL subframe is scheduled among the four DL subframes (when the user terminal detects one DL assignment). In this case, the user terminal uses this UL subframe to feed back the A/Ns for all the CCs that are configured via the PUCCH. That is, the user terminal controls the transmission of the A/N bit sequence based on the information reported by higher layer signaling regardless of the number of CCs to be scheduled and the number of subframes.

In this way, when the user terminal determines the bit size of A/Ns to feed back based on information reported by higher layer signaling, the situation might arise where the A/N bit size does not match the number of CCs actually scheduled.

As stated above, in LTE Rel. <NUM> and later, it is assumed that the restriction on the number of CCs that can be configured in a user terminal is relaxed and six or more CCs are configured. When the number of CCs to be configured is expanded, it is possible that the gap between the number of CCs configured and the number of CCs scheduled in each subframe increases.

Assume, for example, a case where the user terminal is configured with CC #<NUM> to CC #<NUM> (see <FIG>). When some of the CCs (CC #<NUM>, #<NUM>, #<NUM>, #<NUM>, #<NUM>, #<NUM> and #<NUM>) are scheduled in a given subframe (for example, FDD), in existing systems, the A/N bit size to allocate to the PUCCH is determined based on the number of all CC regardless of the number of scheduled CCs (see <FIG>). The user terminal feeds back NACKs for unscheduled CCs.

Similarly, if the bundling window contains four DL subframes (for example, TDD), in existing systems, the A/N bit size to allocate to the PUCCH is determined based on the number of all CC regardless of the number of CC scheduled in each subframe (see <FIG>).

As described above, when the number of CCs to be configured is expanded, it is possible that the gap between the number of CCs configured and the number of CCs scheduled in each subframe increases. If the number of CCs where DL signals are scheduled is less than the number of CCs to be configured and the codebook size is determined semi-statically as in conventional cases, this leads to the situation where most of the ACKs/NACKs transmitted from the user terminal are NACKs.

In general, the smaller the A/N codebook size, the smaller the amount of information that the user terminal transmits. Therefore, if the A/N codebook size can be reduced, the quality of communication (SINR: Signal to Interference plus Noise Power Ratio) required in radio transmission can be kept low. Therefore, it is effective to make it possible to dynamically change the codebook size of A/Ns that the user terminal feeds back, according to the number of CCs that are scheduled (and the number of subframes).

To allow the user terminal to accurately identify the scheduled CCs and subframes and adaptively control the A/N codebook size based on the number of scheduled CCs and subframes, it may be possible to use a DL assignment index (DAI: Downlink Assignment Indicator/Index). For example, the radio base station includes DAIs in the downlink control information (DL assignment) of each CC to be scheduled in a given subframe, and transmits it to the user terminal. DAIs are values assigned to every scheduled cell and used to indicate the number of scheduling CCs (the accumulative number of CCs, the count value, etc.).

When DL signals of a plurality of CCs are detected in a given subframe, if the values of DAIs included in the downlink control information of each CC are not consecutive, the UE can judge the UE has failed to detect the CC corresponding to the undetected DAI. In this way, by using DAIs, it is possible to match the recognition of the A/N codebook size between the user terminal and the radio base station and to appropriately identify the CCs that the user terminal has failed to detect.

However, the present inventors have found out that, even when DAIs are used, if the user terminal fails to detect the cell in which the DAI included in the downlink control information is the largest among the scheduled cells, the user terminal is unable to recognize this detection failure. For this reason, it is effective that the radio base station reports information on the number of CCs scheduled in downlink control information, to the user terminal. That is, it is effective that the radio base station includes information that is used to count scheduling CCs and information to indicate the number of scheduling CCs (total number), in the downlink control information of each CC, and reports this downlink control information to the user terminal. The information used to count scheduling CCs is also referred to as "counter DAIs," and the information to indicate the number of scheduling CCs is also referred to as "total DAIs.

For example, assume that CC #<NUM> to CC #<NUM> are configured on the user terminal (see <FIG>). When part of the CCs (CC #<NUM>, #<NUM>, #<NUM>, #<NUM>, #<NUM>, #<NUM> and #<NUM>) are scheduled in a given subframe, the radio base station configures counter DAIs in the downlink control information of the scheduling CCs, and also configures total DAIs (see <FIG>)). Here, a case is shown where the counter DAIs and the total DAIs are each represented by two bits. Consequently, the counter DAIs corresponding to CC #<NUM>, #<NUM>, #<NUM>, #<NUM>, #<NUM>, #<NUM> and #<NUM> are configured as "<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM>. " Also, since the number of scheduled CCs is seven, the total DAI is configured to "<NUM>.

The user terminal can identify the CCs where the user terminal has failed to detect the DL signals (for example, DL assignments) based on the counter DAIs, and recognize the detection failure of the last CC based on the total DAI.

Also, when four DL subframes are included in the bundling window (for example, TDD), for each subframe, the radio base station configures counter DAIs in the downlink control information of the scheduling CCs and configures total DAIs (see <FIG>). Note that when multiple subframes are included in the bundling window, the radio base station can configure counter DAIs and total DAIs for the scheduled CCs, on a per subframe basis. Alternatively, counter DAIs and/or total DAIs may be configured for CCs scheduled over multiple subframes. For example, counter DAIs may be configured over multiple subframes in the bundling window and total DAI may be configured on a per subframe basis.

Also, control may be exerted by switching between the method of controlling the number of A/N bits using counter DAIs and total DAIs (see <FIG>) and the method of controlling the number of A/N bits based on the number of CCs configured in existing systems (see <FIG>). In this case, the radio base station may be configured to report which control method is used, to the user terminal, by using higher layer signaling or the like.

Thus, when the number of A/N bits is controlled using counter DAIs and total DAIs, as shown in <FIG>, the question is how to apply counter DAIs and/or total DAIs to the CC groups configured according to TTI durations.

Therefore, the present inventors have come up with the idea of separately applying counter DAIs and/or total DAIs, for each CC group with a different TTI duration. In the example shown in <FIG>, counter DAIs and total DAIs are independently controlled in the first CC group formed with CCs of the first TTI duration and the second CC group formed with CCs of the second TTI duration.

<FIG> shows an example in which counter DAIs and total DAIs are applied to each CC group. In the first CC group, DL transmission in CC #<NUM> to CC #<NUM> is scheduled in first TTI #n (normal SF #n). Different counter DAIs (here, <NUM>, <NUM>, <NUM>, and <NUM>) and a common total DAI (here, <NUM>) are included in the downlink control information of CC #<NUM> to CC #<NUM>, and the downlink control information is reported from the radio base station to the user terminal.

The user terminal feeds back A/Ns at the timing a predetermined period later (for example in first TTI #n + <NUM>) based on the reception result in first TTI #n. In this case, the user terminal can identify the CCs which have failed to be detected, considering the counter DAIs and the total DAI, and determine the A/N code book size.

Also, in the first CC group, in first TTI #n + <NUM> (normal SF #n + <NUM>), DL transmissions in CC #<NUM> and CC #<NUM> is scheduled. The radio base station includes different counter DAIs (here, <NUM> and <NUM>) and a common total DAI (here, <NUM>) in the downlink control information of CC #<NUM> and CC #<NUM> and reports the downlink control information to the user terminal.

The user terminal feeds back A/Ns at the timing a predetermined period later (for example in first TTI #n + <NUM>) based on the reception result in first TTI #n + <NUM>.

On the other hand, in second TTI #m (shortened SF #m) in the second CC group, DL transmission in CC #<NUM>, #<NUM>, and #<NUM> is scheduled. The radio base station includes different counter DAIs (here, <NUM>, <NUM>, <NUM>) and a common total DAI (here, <NUM>) in the downlink control information of CCs #<NUM>, #<NUM>, and #<NUM> and reports the downlink control information to the user terminal.

The user terminal feeds back A/Ns at the timing a predetermined period later (for example in second TTI #m + <NUM>) based on the reception result in second TTI #m. In this case, the user terminal can identify the CCs which have failed to be detected, and can determine the A/N codebook size, considering the counter DAIs and the total DAI.

In the second CC group, in second TTI #m + <NUM> (shortened SF #m + <NUM>), DL transmission in CC #<NUM> and CC #<NUM> is scheduled. The radio base station includes different counter DAIs (here, <NUM> and <NUM>) and a common total DAI (here, <NUM>) in the downlink control information of CC #<NUM> and CC #<NUM>, and reports the downlink control information to the user terminal. The user terminal feeds back A/Ns at the timing a predetermined period later (for example, in second TTI #m + <NUM>) based on the reception result in second TTI #m + <NUM>. Second TTIs #m and #m + <NUM> correspond to first TTI #n.

In this way, by individually applying counter DAIs and/or total DAIs per CC group with a different TTI duration, CCs that have failed to be detected can be appropriately identified for each CC group, and the A/N codebook size can be determined. By this, it is possible to properly control the feedback of A/Ns on a per CC group basis.

Further, the radio base station can be configured to simultaneously configure the user terminal to apply counter DAIs and total DAIs to a plurality of CC groups (here, the first CC group and the second CC group). Alternatively, the radio base station may be configured to independently configure the application of counter DAIs and total DAIs, per CC group, in the user terminal. By this, it is possible to flexibly control whether or not to configure counter DAIs and total DAIs, on a per CC group basis.

In a second embodiment, which falls within the scope of the claims, a case will be explained in which CCs with different TTI durations are configured in the same CC group. In the following description, it is shown that one CC group is configured, but the number of CC groups and the number of CCs forming each CC group are not particularly limited. In addition, each CC can use FDD or TDD as appropriate. In the following description, examples of UL transmission control (for example, transmission timing) for A/Ns will be described, but the present embodiment can be applied to other UL transmissions as well. <FIG>, <FIG> show examples useful for understanding the claims, <FIG> shows an example according to the claims.

<FIG> shows an example in which CCs (cells) to be transmitted and received using different TTI durations are included in the same CC group.

Here, when CC #<NUM> to CC #<NUM>, to which the first TTI duration is applied, and CC #<NUM> to CC #<NUM>, to which the second TTI duration is applied, form one CC group. In this case, uplink control information and the like for the CCs of the second TTI duration can be transmitted using a UL channel (for example, uplink control channel) of a predetermined CC of the first TTI duration.

In this way, by including CCs with different TTI durations in the same CC group and controlling scheduling and/or HARQ timing for each CC group, UL transmission (for example, UL transmission using the PUCCH) can be performed using one CC. In this case, unlike when CC groups are configured according to TTI durations (first embodiment), UL transmission by multiple CCs (for example, two CCs) is no longer necessary, so that it is possible to simplify the implementation of the user terminal.

Also, the TTI duration of each CC included in a CC group can be included in higher layer signaling such as RRC signaling, which reports configuration and reconfiguration of each CC.

When DC is applied, this higher layer signaling may be transmitted and received only from the CCs belonging to the MCG. When DC is applied, the user terminal may communicate with different radio base stations between the MCG and SCGs. To realize this, backhaul signaling may be introduced, in which the MeNB controlling the MCG and the SeNB controlling the SCG report the TTI duration of each CC included in each cell group to each other. For example, signaling may be introduced in which the MeNB specifies to the SeNB the TTI duration which the user terminal uses when communicating with the each CC of the SCG. This allows the SeNB to recognize the TTI duration used by the user terminal when communicating with the each CC of the SCG, which is configured in the user terminal by the MeNB via higher layer signaling, so that the SeNB can properly communicate with the user terminal.

Signaling may also be introduced in which one or more TTI durations which the user terminal can use when communicating with each CC of the SCG are reported from the SeNB to the MeNB. As a result, the MeNB can recognize the TTI duration that each CC of the SeNB can use for communication with the user terminal, and the MeNB can select an appropriate TTI duration out of the TTI durations that the SeNB can use in each CC for communication and configure it in the user terminal. If TTI durations that can be used when the user terminal communicates with each CC of the SCG are not reported from SeNB to MeNB, the MeNB may recognize that the <NUM>-ms normal TTI, specified in conventional LTE, is the only TTI duration that can be configured in each CC of the SeNB.

In configurations where CCs with different TTI durations are included in the same CC group, control may be performed so that the scheduling and/or HARQ timing vary depending on the TTI duration of the CC (or TTI duration of subframe). In the case shown in <FIG>, in first TTI #n (normal SF #n), A/N feedback for DL transmission of CC #<NUM> to CC #<NUM> and/or uplink data for UL grant of CC #<NUM> to CC #<NUM> are transmitted in first TTI #n + <NUM> (SF #n + <NUM>). When an A/N is not transmitted at the same time with UL data (PUSCH), it is transmitted on the uplink control channel of a predetermined CC, and, when an A/N is transmitted simultaneously with UL data, it can be included in the UL data and transmitted.

On the other hand, in the case shown here, in second TTI #m, A/N feedback for the DL transmission of CC #<NUM> to CC #<NUM> and/or uplink data for UL grants of CC #<NUM> to CC #<NUM> are transmitted in first TTI #n + <NUM> (SF #n + <NUM>). Here, two second TTIs correspond to the first TTI (here, second TTI #m and #m + <NUM> correspond to first TTI #n).

That is, the user terminal sets the timing to transmit an A/N in response to DL data of a shortened TTI (second TTI) earlier than the timing to transmit an A/N (for example, four ms later) in response to DL data of a normal TTI (first TTI). Further, the user terminal transmits the UL data transmission timing in response to a UL grant received in a CC of a shortened TTI (second TTI) earlier than the timing to transmit UL data (for example, four ms later) in response to a UL grant received in a CC of a normal TTI (first TTI). As a result of this, even if CCs with different TTI durations are included in the same CC group, scheduling and/or HARQ timing can be controlled according to TTI durations. As a result, delay of UL transmission can be suppressed.

As shown in <FIG>, when A/Ns for DL data scheduled at the same timing are not fed back at the same time among CCs with different TTI durations, it is possible to simultaneously transmit A/Ns in response to DL data scheduled at different timings (see <FIG>).

For example, A/Ns in response to DL data scheduled in CC #<NUM> to CC #<NUM> in first TTI #n and A/Ns in response to DL data scheduled in CC #<NUM> to CC #<NUM> in second TTI #m + <NUM> can be fed back at the same timing. In this case, A/Ns in response to DL data of CCs with different TTI durations can be multiplexed in an uplink control channel of a predetermined CC (here, CC #<NUM>) and transmitted.

Also, control may be performed so that multiple shortened TTIs (here, second TTIs) are fed back using one UL transmission (in this case, UL transmission in CC #<NUM>) (see <FIG>). For example, the user terminal can perform UL transmission in a number of shortened TTIs corresponding to one normal TTI (first TTI) at once. In the case shown in <FIG>, the user terminal performs UL transmission (for example, A/N) for the two shortened TTIs of second TTI #m + <NUM> and #m + <NUM> using a predetermined CC. As the predetermined CC, it is possible to use a CC (CC #<NUM>) of a normal TTI that is longer than the shortened TTI.

Also, the PUCCH resource to use for A/N feedback may be specified in a second TTI closer to the PUCCH transmission timing. That is, the UE can determine the PUCCH resource used for A/N feedback based on the DL control signal in the TTI closest to the PUCCH transmission timing. In this case, the radio base station can update the PUCCH resource specified in the DL scheduling timing of the first TTI at the scheduling timing of the second TTI in which A/N feedback is sent using the same PUCCH resource, so that the flexibility of control by the scheduler can be improved.

As shown in <FIG>, between CCs with different TTI durations, when the scheduling and/or HARQ timing are controlled based on the TTI duration of CCs, it may be possible to simultaneously transmit A/Ns in response to DL data scheduled at different timings. In this case, how to apply counter DAIs and/or total DAIs is the problem. Hereinafter, an example of a counter DAI and/or a total DAI application method in the second embodiment will be described. In the following description, it is shown that the counter DAIs and total DAIs are each <NUM> bits, but the present embodiment is not limited to this.

When CA is performed in CCs with different TTI durations, counter DAIs and/or total DAIs can be applied individually between CCs of the same TTI duration. As an example, counter DAIs that continuously count up can only be applied between CCs with the same TTI duration (see <FIG>). In <FIG>, for CC #<NUM>, #<NUM>, and #<NUM> scheduled in first TTI #n and CC #<NUM>, #<NUM>, and #<NUM> scheduled in second TTI #m + <NUM>, counter DAIs are individually configured. Likewise, total DAIs can also be independently configured be between CCs of the same TTI durations (between CCs where counter DAIs are configured).

In this case, the counter DAIs of TTIs which are temporally different become discontinuous. The user terminal identifies the A/N and A/N bit sequence of each CC based on the counter DAIs and total DAIs configured for each TTI duration, and controls the feedback. Note that the control unit of counter DAIs and total DAIs is not limited to the TTI duration of CCs.

Alternatively, control can be performed so that counter DAIs continuously count up between CCs that belong to the same CC group but have different TTI durations (see <FIG>). In <FIG>, continuous counter DAIs are configured in CC #<NUM>, #<NUM>, and #<NUM> scheduled in first TTI #n and CC #<NUM>, #<NUM>, and #<NUM> scheduled in second TTI #m + <NUM>. Likewise, total DAIs can also be configured considering the total number of scheduling CCs (here, <NUM>) between CCs with different TTI durations.

When consecutive counter DAIs are configured between different TTIs in time, counter DAIs can be configured that count up in order from the CC of the earliest timing (for example, scheduling timing). Alternatively, it is possible to determine the order of counting up based on the TTI duration of CCs (for example, CCs with longer TTI durations can be given priority)). If the scheduling timing and/or the TTI duration are the same between CCs, the order of counting up may be determined based on the CC indices, etc..

Also, as shown in <FIG>, when multiple shortened TTIs are subject to feedback using one UL transmission, the counter DAIs and/or total DAIs can be configured based on the TTI duration and/or scheduling timing of the CCs.

In the case shown in <FIG>, counter DAIs and total DAIs are individually controlled for each CC having a different scheduling timing. In particular, in CCs scheduled in first TTI #n, CCs scheduled in second TTI #m + <NUM>, and CCs scheduled in second TTI #m + <NUM>, independent total DAIs are configured. Counter DAIs can be configured likewise. By doing this, A/Ns and so on can be judged on a per TTI basis.

<FIG> shows the case where counter DAIs and total DAIs are individually controlled for each CC with a different TTI duration. To be more specific, independent total DAIs are configured in a CC scheduled in the first TTI and a CC scheduled in the second TTI. Counter DAI can be configured likewise. That is, consecutive counter DAIs are configured in second TTI #m + <NUM> and #m + <NUM> that perform UL transmission at the same timing. Also, total DAIs are configured based on the number of CCs scheduled in second TTI #m + <NUM> and #m + <NUM>. With this, it is possible to judge A/Ns and so on for CCs having the same TTI duration based on one type of counter DAI and total DAI.

In the case shown in <FIG>, regardless of the TTI duration of CCs or the scheduling timing, Counter DAIs and total DAIs are configured for CCs that perform UL transmission at the same CC and/or timing. To be more specific, continuous counter DAIs are configured among the CCs scheduled in first TTI #n, the CCs scheduled in second TTI #m + <NUM> and the CCs scheduled in second TTI #m + <NUM>. Also, total DAIs are configured based on the number of CCs scheduled in first TTI #n, second TTI #m + <NUM>, and second TTI #m + <NUM>). As a result of this, regardless of the TTI duration of CCs, it is possible to judge A/Ns and so on for CCs that carry out UL transmission at the same time based on one type of counter DAI and total DAI.

Also, in the case where continuous counter DAIs are configured in CCs that have the same TTI duration but have different timings (CCs scheduled in second TTI #m + <NUM> and #m + <NUM>, in this case) the count-up order of the counter DAIs can be appropriately configured (see <FIG> and <FIG>). For example, it is possible that counter DAIs count up in the CC direction after counting up in multiple shortened TTI directions (time direction) (see <FIG>)). Accordingt to the claims, counter DAIs count up in the CC direction and then count up in the TTI direction (see <FIG>). Also, when continuous counter DAIs are configured between CCs with different TTI durations (<FIG>), it is possible to count up sequentially from the CC with the earliest scheduling timing (or the CC with the longest TTI duration).

Note that the method of applying counter DAIs and total DAIs is not limited to the method shown in <FIG>). For example, it is possible to configure counter DAIs and total DAIs by considering the CCs scheduled in first TTI #n and the CCs scheduled in second TTI #m + <NUM>. On the other hand, apart from this, a configuration in which counter DAIs and total DAIs are configured in consideration of the CCs scheduled in second TTI #m + <NUM> may be used. This configuration corresponds to a configuration in which "y" in second TTI #m + <NUM> in <FIG> is replaced by "x.

Thus, when a CC group is formed with CCs with different TTI durations, by applying counter DAIs and/or total DAIs, A/N transmission in response to CCs with different TTI durations can be performed appropriately.

In the third example, the capability information (UE capability signaling) reported from the user terminal to the radio base station when CCs (cells) that transmit and receive in different TTI durations are included in the same CC group will be explained.

User terminals that support CA and/or DC that bundle CCs of different TTI durations can report, to the radio base station, information about the size that can be transmitted and received over all TTIs included in the normal TTI (first TTI) period and/or the number of times of blind decoding of a downlink control channel (see <FIG>). For example, in <FIG>, the user terminal reports capability information, taking into account CC #<NUM> to CC #<NUM> in the first TTI #n period and CC #<NUM> to CC #<NUM> in the second TTI #m and #m + <NUM> periods corresponding to first TTI #n, to the radio base station.

Note that the size that can be transmitted and received can be the number of transport block bits (DL/UL-SCH TB bits) in the DL shared channel and/or the UL shared channel. The downlink control channel can be the PDCCH and/or the EPDCCH.

Alternatively, the user terminal can report to the radio base station information on the size that can be transmitted and received in one TTI of each CC included in a normal TTI (first TTI) period and/or information on the number of times of blind decoding of a downlink control channel (see <FIG>)). For example, in <FIG>, the user terminal reports capability information (first capability information), taking CC #<NUM> to CC #<NUM> of the first TTI #n period and CC #<NUM> to CC #<NUM> in the second TTI #m period corresponding to a part of the first TTI #n period, to the radio base station. Further, the user terminal reports capability information (second capability information), taking CC #<NUM> to CC #<NUM> of the first TTI #n period and CC #<NUM> to CC #<NUM> in the second TTI #m + <NUM> period corresponding to a part of the first TTI #n period, to the radio base station. The user terminal may transmit both the first capability information and the second capability information to the radio base station, or the user terminal may transmit one capability information (for example, the capability information with the smaller bit size and the smaller number of times of blind decoding) to the radio base station.

As shown in <FIG>, when, for shortened TTIs, the size that can be transmitted and received and the number of times of blind decoding are determined by the user terminal for each shortened TTI (unit of transmission) and transmitted to the radio base station, compared to the case of <FIG>, the radio base station can configure more sizes and numbers of times of blind decoding.

Now, the structure of the radio communication system according to an embodiment of the present invention will be described below. In this radio communication system, the radio communication methods of the above-described embodiments are employed. Note that the radio communication methods of the above-described embodiments 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 one embodiment of the present invention. The radio communication system <NUM> can adopt carrier aggregation (CA) and/or dual connectivity (DC) to group a plurality of fundamental frequency blocks (component carriers) into one, where the LTE system bandwidth (for example, <NUM>) constitutes one unit. Note that the radio communication system <NUM> may be referred to as "SUPER <NUM>," "LTE-A" (LTE-Advanced), "IMT-Advanced," "<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 or DC by using a plurality of cells (CCs) (for example, six or more CCs).

Note that the configuration of the frequency band for use in each radio base station is by no means limited to these.

A structure may be employed here in which wire connection (for example, means in compliance with the CPRI (Common Public Radio Interface) such as optical fiber, the X2 interface and so on) or wireless connection is established between the radio base station <NUM> and the radio base station <NUM> (or between two radio base stations <NUM>).

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 <NUM>, 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 make 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 not limited to these combinations, and OFDMA may be used in the uplink.

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 Blocks) is communicated in 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 is frequency-division-multiplexed with the PDSCH (downlink shared data channel) and used to communicate DCI and so on, like the PDCCH.

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. Uplink control information (UCI: Uplink Control Information), including at least one of delivery acknowledgment information (ACK/NACK) and radio quality information (CQI), is transmitted by the PUSCH or the PUCCH. By means of the PRACH, random access 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 according to one embodiment of the present invention. A 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 sections <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>.

Baseband signals that are pre-coded and output from the baseband signal processing section <NUM> on a per antenna basis are converted into a radio frequency band in the transmitting/receiving sections <NUM>, and then transmitted. 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>.

The transmitting/receiving sections (transmitting sections) <NUM> transmit DL signals from a plurality of CCs. Further, the transmitting/receiving sections (transmitting sections) <NUM> can transmit CC group information, which includes information about at least one of the CC groups to configure in the user terminal, the TTI durations of the CC groups, the CCs included in the CC groups, and the TTI durations of the CCs. Also, when counter DAIs and/or total DAIs are applied, the transmitting/receiving sections (transmitting sections) <NUM> include counter DAI and/or total DAIs in the downlink control information (for example, DL assignment) of the scheduling CCs). As for the application method of counter DAIs and total DAIs, any of the methods described in the above embodiments can be applied.

The transmitting/receiving sections (receiving sections) <NUM> receive UL signals transmitted for each CC group formed with at least one CC (for example, A/N, PUSCH, CSI, etc.). The transmitting/receiving sections <NUM> can be constituted by 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.

Note that a transmitting/receiving section <NUM> may be structured as a transmitting/receiving section in one entity, or may be constituted by a transmitting section and a receiving section.

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. Also, the communication path interface <NUM> may transmit and/or receive signals (backhaul signaling) with other radio base stations <NUM> via an inter-base station interface (for example, an interface in compliance with the CPRI (Common Public Radio Interface), such as 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 present embodiment. Note that, although <FIG> primarily shows functional blocks that pertain to characteristic parts of the present embodiment, 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 generation section (generation 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. Also, the control section <NUM> controls the scheduling of system information, synchronization signals, paging information, CRSs (Cell-specific Reference Signals), CSI-RSs (Channel State Information Reference Signals) and so on. Furthermore, the control section <NUM> also controls the scheduling of uplink reference signals, uplink data signals that are transmitted in the PUSCH, and uplink control signals that are transmitted in the PUCCH and/or the PUSCH.

The control section <NUM> controls the retransmission of downlink data/new data transmission based on delivery acknowledgment signals (HARQ-ACKs) fed back from the user terminals. Further, the control section <NUM> controls reception processing of HARQ-ACK fed back from the user terminal based on the bundling window in response to DL transmission. Note that the reception processing may be performed in the received signal processing section <NUM> based on commands from the control section <NUM>. Further, the control section <NUM> can configure the CC groups to be configured in the user terminal. The methods described in the above embodiments can be applied as methods of configuring CCs that form CC groups (<FIG>, <FIG>, etc.). 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 generation section <NUM> generates DL signals (downlink control signals, downlink data signals, downlink reference signals and so on) based on commands from the control section <NUM>, and outputs these signals to the mapping section <NUM>. To be more specific, the transmission signal generation section <NUM> generates a downlink data signal (PDSCH) including user data, and outputs it to the mapping section <NUM>. Further, the transmission signal generation section <NUM> generates a downlink control signal (PDCCH/EPDCCH) including DCI (UL grant), and outputs it to the mapping section <NUM>. Further, the transmission signal generation section <NUM> generates downlink reference signals such as CRS and CSI-RS, and outputs them to the mapping section <NUM>.

When counter DAIs and/or total DAIs are applied, the transmission signal generation section <NUM> generates downlink control information (for example, DL assignment) including counter DAIs and/or total DAIs. When CA is performed between CCs with different TTI durations, the transmission signal generation section <NUM> can individually apply counter DAIs and/or total DAIs between CCs with the same TTI duration (see <FIG>. ) (CCs in the same CC group). Alternatively, the control section <NUM> may apply counter DAIs and/or total DAIs between CCs with different TTI durations (see <FIG>). Also, when consecutive counter DAIs are configured between TTIs that are different in time, the control section <NUM> can configure counter DAIs that count up based on a predetermined rule (<FIG>)). For the transmission signal generation 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 generation section <NUM> to predetermined radio resources based on commands from the control section <NUM>, and outputs these 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 reception process (for example, demapping, demodulation, decoding, etc.) of the UL signals (HARQ-ACK, PUSCH, etc.) transmitted from the user terminal <NUM>. The processing results are output to the control 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 according to an embodiment of the present invention. 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 signals are 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 (receiving sections) <NUM> receive DL signals transmitted from a plurality of component carriers (CCs). Further, the transmitting/receiving sections (receiving sections) <NUM> transmit CC group information including at least one of the CC groups to be configured, the TTI duration in the CC groups, the CCs included in the CC groups, and the information on the TTI duration of the CCs. Further, the transmitting/receiving sections (receiving sections) <NUM> can receive downlink control information including counter DAIs and/or total DAIs. The transmitting/receiving sections (transmitting sections) <NUM> transmit UL signal to predetermined CCs. When CA is applied, the transmitting/receiving sections (transmitting sections) <NUM> can feed back uplink control information (for example, A/Ns) in response to DL data in each CC in predetermined CCs.

Further, the transmitting/receiving sections <NUM> (transmitting sections) transmit information on the size that can be transmitted and received over all TTIs included in a normal TTI (first TTI) period and/or information on the number of times of blind decoding of a downlink control channel (see <FIG>)). Alternatively, the transmitting/receiving sections (transmitting sections) <NUM> transmit information on the size that can be transmitted and received in one TTI of each CC included in a normal TTI (first TTI) period and/or information on the number of times of blind decoding of a downlink control channel (see <FIG>)). 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, pre-coding, 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> and transmitted. 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 according to the present embodiment. 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 generation section <NUM>, a mapping section <NUM>, a received signal processing section <NUM> and a decision section <NUM>.

The control section <NUM> acquires 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 of uplink control signals (for example, delivery acknowledgement signals (HARQ-ACKs) and so on) and uplink data signals based on the downlink control signals, the results of deciding whether or not re transmission control is necessary for the downlink data signals, and so on. To be more specific, the control section <NUM> can control the transmission signal generation section <NUM>, the mapping section <NUM> and the received signal processing section <NUM>.

The control section <NUM> can control UL signal transmission for each CC group formed with at least one CC according to the TTI duration (see <FIG>). For example, the control section <NUM> controls the transmission of uplink data and/or uplink control information for a plurality of CC groups at different timings. Also, when the transmission periods of UL signals for multiple CCs with different TTI durations overlap, the control section <NUM> can preferentially configure UL transmission power to CC with earlier transmission timings (see <FIG>).

The control section <NUM> can control A/N transmission based on counter DAIs and/or total DAIs, which are configured per CC group and included in downlink control information (see <FIG>). For example, the control section <NUM> can determine the number of scheduling CCs in each CC group based on counter DAIs and/or total DAIs that are configured on a per CC group basis.

Alternatively, the control section <NUM> can control the transmission of UL signals in CC groups formed with a plurality of CCs having different TTI durations (see <FIG>)). For example, in a CC group formed with a plurality of CCs having different TTI durations, the control section <NUM> performs control so that the uplink control information corresponding to each CC is transmitted in a predetermined CC at different timings according to the TTI duration of each CC (see <FIG>)). Also, between CCs with different TTI durations, the control section <NUM> can perform control so that A/Ns in response to DL data scheduled at different timings are simultaneously transmitted in a predetermined CC. Also, between CCs with different TTI durations, the control section <NUM> can perform control so that UL data in response to UL grants scheduled at different timings are transmitted at the same timing). 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 generation 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 generation 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 generation 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 generation section <NUM> to generate an uplink data signal. For the transmission signal generation 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 generation 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 receiving processes (for example, demapping, demodulation, decoding and so on) of DL signals (for example, downlink control signals transmitted from the radio base station, 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>. The received signal processing section <NUM> outputs, for example, broadcast information, system information, RRC signaling, DCI and so on, to the control section <NUM>.

The received signal processing 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. Also, the received signal processing section <NUM> can constitute the receiving section according to the present invention.

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>. When downlink signals (PDSCH) are transmitted from multiple CCs (for example, six or more CCs), retransmission control decisions (ACKs/NACKs) are made on a per CC basis, and output 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/or 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 by using these multiple devices.

That is, the radio base stations, user terminals and so according to embodiments of the present invention may function as a computer that executes the processes of the radio communication method of the present invention. <FIG> is a diagram to show an example hardware structure of a radio base station and a user terminal according to an embodiment of the present invention. Physically, a radio base station <NUM> and a user terminal <NUM>, which have been described above, may be formed as a computer apparatus that includes a processor <NUM>, a memory <NUM>, a storage <NUM>, a communication apparatus <NUM>, an input apparatus <NUM>, an output apparatus <NUM> and a bus <NUM>.

Note that the hardware structure of the radio base station <NUM> and the user terminal <NUM> may be designed to include one or more of each apparatus shown in the drawings, or may be designed not to include part of the apparatuses.

Each function of the radio base station <NUM> and the user terminal <NUM> is implemented by reading predetermined software (programs) on hardware such as the processor <NUM> and the memory <NUM>, and by controlling the calculations in the processor <NUM>, the communication in the communication apparatus <NUM>, and the reading and/or writing of data in the memory <NUM> and the storage <NUM>.

The processor <NUM> may control the whole computer by, for example, running an operating system. The processor <NUM> may be configured with a central processing unit (CPU) including an interface with a peripheral device, a control device, a computing device, a register, and the like. For example, the above-described baseband signal process section <NUM> (<NUM>), call processing section <NUM> and so on may be implemented by the central processing apparatus <NUM>.

Further, the processor <NUM> reads a program (program code), a software module or data from the storage <NUM> and/or the communication device <NUM> to the memory <NUM>, and executes various processes according to these. As for the programs, programs to allow the computer to execute at least part of the operations of the above-described embodiments may be used. For example, the control section <NUM> of the user terminals <NUM> may be stored in the memory <NUM> and implemented by a control program that operates on the processor <NUM>, and other functional blocks may be implemented likewise.

The memory <NUM> is a computer-readable recording medium, and may be constituted by, for example, at least one of a ROM (Read Only Memory), an EPROM (Erasable Programmable ROM), a RAM (Random Access Memory) and so on. The memory <NUM> may be referred to as a "register," a "cache," a "main memory" (primary storage apparatus) or the like. The memory <NUM> can store executable programs (program codes), software modules, and the like for implementing the radio communication methods according to embodiments of the present invention.

The storage <NUM> is a computer readable recording medium, and is configured with at least one of an optical disk such as a CD-ROM (Compact Disc ROM), a hard disk drive, a flexible disk, a magneto-optical disk, a flash memory and so on. The storage <NUM> may be referred to as a "secondary storage apparatus.

The communication apparatus <NUM> is hardware (transmitting/receiving device) for allowing inter-computer communication by using wired and/or wireless networks, and may be referred to as, for example, a "network device," a "network controller," a "network card," a "communication module" and so on. For example, the above-described transmitting/receiving antennas <NUM> (<NUM>), amplifying sections <NUM> (<NUM>), transmitting/receiving sections <NUM> (<NUM>), communication path interface <NUM> and so on may be implemented by the communication apparatus <NUM>.

The input apparatus <NUM> is an input device for receiving input from the outside (for example, a keyboard, a mouse, etc.). The output apparatus <NUM> is an output device for allowing sending output to the outside (for example, a display, a speaker, etc.).

Further, the respective devices such as the processor <NUM> and the memory <NUM> are connected by a bus <NUM> for communicating information. The bus <NUM> may be formed with a single bus, or may be formed with buses that vary between the apparatuses.

For example, the processor <NUM> may be implemented with at least one of these hardware.

Note that the terminology used in this description and the terminology that is needed to understand this description may be replaced by other terms that convey the same or similar meanings. For example, "channels" and/or "symbols" may be replaced by "signals" (or "signaling"). Also, "signals" may be "messages. " Furthermore, "component carriers" (CCs) may be referred to as "cells," "frequency carriers," "carrier frequencies" and so on.

Further, a radio frame may be comprised of one or more periods (frames) in the time domain. Each of one or more periods (frames) constituting a radio frame may be referred to as a "subframe. " Further, a subframe may be comprised of one or more slots in the time domain. Further, a slot may be comprised of one or more symbols (OFDM symbols, SC-FDMA symbols, etc.) in the time domain.

A radio frame, a subframe, a slot and a symbol all represent the time unit in signal communication. Radio frames, subframes, slots and symbols may be called by other names. For example, one subframe may be referred to as a "transmission time interval" (TTI), or a plurality of consecutive subframes may be referred to as a "TTI," and one slot may be referred to as a "TTI. " That is, a subframe and a TTI may be a subframe (one ms) in existing LTE, may be a shorter period than one ms (for example, <NUM> to <NUM> symbols), or may be a longer period of time than one ms.

Here, a TTI refers to the minimum time unit of scheduling in wireless communication, for example. For example, in LTE systems, the radio base station schedules the allocation radio resources (such as the frequency bandwidth and transmission power that can be used by each user terminal) to each user terminal in TTI units. The definition of TTIs is not limited to this.

A resource block (RB) is a resource allocation unit in the time domain and the frequency domain, and may include one or a plurality of consecutive subcarriers in the frequency domain. Also, an RB may include one or more symbols in the time domain and may be one slot, one subframe or one TTI in length. One TTI and one subframe each may be comprised of one or more resource blocks. Note that an RB may be referred to as a "physical resource block" (PRB: Physical RB), a "PRB pair," an "RB pair," or the like.

Further, a resource block may be comprised of one or more resource elements (REs).

Note that the structures of radio frames, subframes, slots, symbols and the like described above are merely examples. For example, configurations such as the number of subframes included in a radio frame, the number of slots included in a subframe, the number of symbols and RBs included in a slot, the number of subcarriers included in an RB, the number of symbols in a TTI, the symbol duration and the cyclic prefix (CP) length can be variously changed.

Also, the information and parameters described in this description may be represented in absolute values or in relative values with respect to a predetermined value, or may be represented in other information formats. For example, radio resources may be specified by predetermined indices.

The information, signals and/or others described in this description may be represented by using a variety of different technologies. For example, data, instructions, commands, information, signals, bits, symbols and chips, all of which may be referenced throughout the description, may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or photons, or any combination of these.

Also, software and commands may be transmitted and received via communication media. For example, when software is transmitted from a website, a server or other remote sources by using wired technologies (coaxial cables, optical fiber cables, twisted-pair cables, digital subscriber lines (DSL) and so on) and/or wireless technologies (infrared radiation and microwaves), these wired technologies and/or wireless technologies are also included in the definition of communication media.

Further, the radio base station in this specification may be read by a user terminal. For example, each aspect/embodiment of the present invention may be applied to a configuration in which communication between a radio base station and a user terminal is replaced with communication of a plurality of user terminals (D2D: Device-to-Device). In this case, the user terminal <NUM> may have the functions of the radio base station <NUM> described above. In addition, wording such as "uplink" and "downlink" may be interpreted as "side. " For example, an uplink channel may be interpreted as a side channel.

Likewise, a user terminal in this specification may be interpreted as a radio base station. In this case, the radio base station <NUM> may have the functions of the user terminal <NUM> described above.

The example s/embodiments illustrated in this description may be used individually or in combinations, and the mode of may be switched depending on the implementation. Also, a report of predetermined information (for example, a report to the effect that "X holds") does not necessarily have to be sent explicitly, and can be sent implicitly (by, for example, not reporting this piece of information).

Reporting of information is by no means limited to the example s/embodiments described in this description, and other methods may be used as well. For example, reporting of information may be implemented by using physical layer signaling (for example, DCI (Downlink Control Information) and UCI (Uplink Control Information)), higher layer signaling (for example, RRC (Radio Resource Control) signaling, broadcast information (the MIB (Master Information Blocks) and SIBs (System Information Blocks) and so on) and MAC (Medium Access Control) signaling, other signals or combinations of these. Also, the MAC signaling may be reported, for example, by a MAC control element (MAC CE (Control Element)).

The examples/embodiments illustrated in this description may be applied to LTE (Long Term Evolution), LTE-A (LTE-Advanced), LTE-B (LTE-Beyond), SUPER <NUM>, IMT-Advanced, <NUM> (4th generation mobile communication system), <NUM> (5th generation mobile communication system), FRA (Future Radio Access), New-RAT (Radio Access Technology), CDMA <NUM>, UMB (Ultra Mobile Broadband), IEEE <NUM> (Wi-Fi (registered trademark)), IEEE <NUM> (WiMAX (registered trademark)), IEEE <NUM>, UWB (Ultra-WideBand), Bluetooth (registered trademark), and other adequate systems, and/or next-generation systems that are enhanced based on these.

The order of processes, sequences, flowcharts and so on that have been used to describe the examples/embodiments herein may be re-ordered as long as inconsistencies do not arise. For example, although various methods have been illustrated in this description with various components of steps in exemplary orders, the specific orders that illustrated herein are by no means limiting.

Claim 1:
A user terminal (<NUM>) configured to communicate with a plurality of cells, the user terminal comprising:
a receiving section (<NUM>) configured to receive multiple downlink control information including a counter Downlink Assignment Indicator, DAI, from the plurality of cells; and
a transmission section (<NUM>) configured to transmit a delivery acknowledgement signal for a downlink shared data channel received from each of the plurality of cells based on the counter DAI, wherein
the plurality of cells include first cells (CC#<NUM> - CC#<NUM>) and second cells (CC#<NUM> - CC#<NUM>), the first cells including first count cells at a first time index (#n), and the second cells including second count cells at a second time index (#m+<NUM>) and third count cells at a third time index (#m+<NUM>) subsequent to the second time index (#m+<NUM>), the first time index (#n) being located prior to the second time index (#m+<NUM>), wherein continuous counter DAI is configured for the first count cells, the second count cells and the third count cells,
the first cells (CC#<NUM> - CC#<NUM>) are configured with a first-time unit, and the second cells (CC#<NUM> - CC#<NUM>) are configured with a second-time unit shorter than the first-time unit and shorter than a subframe,
a value of the counter DAI is counted up from a lowest cell index of the first count cells to a maximum cell index of the first count cells,
after the maximum cell index is reached, the value of the counter DAI is counted up from a lowest cell index of the second count cells at the second time index (#m+<NUM>) to a maximum cell index of the second count cells, and
after the maximum cell index of the second count cells is reached, the value of the counter DAI is counted up from a lowest cell index of the third count cells at the third time index (#m+<NUM>) to a maximum cell index of the third count cells.