Base station, terminal, and communication method

1. A base station comprising:

a generator, which, in operation, generates downlink control information (DCI) containing control information for a plurality of first transmission time intervals (TTIs) each having a TTI length shorter than a second TTI; and

a transmitter, which, in operation, transmits the DCI, wherein

first control information on retransmission processing for a data signal is configured for each of the plurality of first TTIs, second control information other than the first control information is configured in common among the plurality of first TTIs corresponding to the first control information, a Demodulation Reference signal (DMRS) is mapped to the plurality of first TTIs, and the transmitter transmits the first control information and the second control information in a same subframe.

2. The base station according to claim 1 , wherein the DCI contains information indicating the presence or absence of an assignment for each of the plurality of first TTIs.

3. The base station according to claim 1 , wherein control information on retransmission processing for a downlink data signal is information indicating an HARQ process number, a new data indicator (NDI), a redundancy version (RV), or a combination of a plurality of transport blocks and codewords in the DCI.

4. The base station according to claim 1 , wherein control information on retransmission processing for an uplink data signal is a new data indicator (NDI) in the DCI.

5. The base station according to claim 3 , wherein

the transmitter, in operation, transmits a physical HARQ indicator channel (PHICH) containing an ACK/NACK signal for an uplink data signal assigned in a TTI in which non-adaptive retransmission is performed among the plurality of first TTIs,

the transmitter, in operation, transmits the DCI containing the NDI for an uplink data signal assigned in a TTI in which adaptive retransmission is performed among the plurality of first TTIs, and

the DCI contains no assignment for the TTI in which non-adaptive retransmission is performed.

6. The base station according to claim 3 , wherein

the transmitter, in operation, transmits the DCI containing the NDI for an uplink data signal assigned in the plurality of first TTIs in which adaptive retransmission is performed, and

the transmitter, in operation, transmits no physical HARQ indicator channel (PHICH).

7. The base station according to claim 1 , wherein the plurality of first TTIs is placed in one subframe.

8. The base station according to claim 1 , wherein the plurality of first TTIs is placed in one slot.

9. The base station according to claim 1 , further comprising a receiver, which, in operation, receives an ACK/NACK signal for a downlink data signal transmitted in the plurality of first TTIs, wherein

the ACK/NACK signal for a downlink data signal transmitted in an earlier time TTI among the plurality of first TTIs is mapped to an earlier time resource among uplink resources.

10. The base station according to claim 9 , wherein

the receiver, in operation, receives a reference signal, and

the reference signal is shared between TTIs placed in the same slot as that in which the ACK/NACK signal is mapped among the plurality of first TTIs.

11. The base station according to claim 1 , further comprising a receiver, in operation, receives an ACK/NACK signal for a downlink data signal transmitted in the plurality of first TTIs, wherein

ACK/NACK signals corresponding respectively to the plurality of first TTIs are bundled or multiplexed, and mapped over ACK/NACK resources within one subframe.

12. A terminal comprising:

a receiver, which, in operation, receives downlink control information (DCI) containing control information for a plurality of first transmission time intervals (TTIs) each having a TTI length shorter than a second TTI; and

circuitry, which, in operation, demultiplexes a downlink data signal from a received signal using the DCI, and assigns an uplink data signal to an uplink resource using the DCI, wherein

first control information on retransmission processing for a data signal is configured for each of the plurality of first TTIs, second control information other than the first control information is configured in common among the plurality of first TTIs corresponding to the first control information, a Demodulation Reference signal (DMRS) is mapped to the plurality of first TTIs, and the transmitter transmits the first control information and the second control information in a same subframe.

13. A communication method comprising:

generating downlink control information (DCI) containing control information for a plurality of first transmission time intervals (TTIs) each having a TTI length shorter than a second TTI; and

transmitting the DCI, wherein

first control information on retransmission processing for a data signal is configured for each of the plurality of first TTIs, second control information other than the first control information is configured in common among the plurality of first TTIs corresponding to the first control information, a Demodulation Reference signal (DMRS) is mapped to the plurality of first TTIs, and the transmitter transmits the first control information and the second control information in a same subframe.

14. A communication method comprising:

receiving downlink control information (DCI) containing control information for a plurality of first transmission time intervals (TTIs) each having a TTI length shorter than a second TTI;

demultiplexing a downlink data signal from a received signal using the DCI; and

assigning an uplink data signal to an uplink resource using the DCI, wherein

first control information on retransmission processing for a data signal is configured for each of the plurality of first TTIs, second control information other than the first control information is configured in common among the plurality of first TTIs corresponding to the first control information, a Demodulation Reference signal (DMRS) is mapped to the plurality of first TTIs, and the transmitter transmits the first control information and the second control information in a same subframe.