Base station, terminal, and communication method

Abstract

The present disclosure relates to a base station, a terminal, and a communication method. Specifically, a base station is disclosed, comprising: a transmitter that transmits a downlink signal to a terminal in a first short transmission time interval (sTTI) shorter than a subframe; and a receiver that receives an uplink signal transmitted from the terminal in a second sTTI shorter than the subframe and longer than the first sTTI, wherein the receiver receives the uplink signal transmitted in the second sTTI after a determined number of first sTTIs from a transmission timing of the downlink signal, and the determined number is applied to all first sTTIs of the subframe.

Description

[0001] This application is a divisional application of Chinese Patent Application No. 201680083088.5, filed on March 30, 2016, entitled "Base station, terminal, and communication method", with applicant Panasonic Intellectual Property Management Co., Ltd. TECHNICAL FIELD

[0002] The present disclosure relates to a base station, a terminal, and a communication method. BACKGROUND

[0003] In recent years, development of applications requiring latency time reduction (latency critical) has been considered. Examples of these applications requiring latency time reduction include automated vehicle driving, augmented reality applications in smart glasses, or inter-machine communication.

[0004] In 3GPP, in order to develop these applications, latency reduction for reducing packet data latency has been studied (see Non-Patent Literature 1). In latency reduction, shortening (reducing) the length (TTI length) of a transmission time interval (TTI) as a time unit for transmission and reception of data to a time length between 0.5 milliseconds and one orthogonal frequency division multiplexing (OFDM) symbol has been considered. Note that the conventional TTI length is 1 millisecond, which is equal to a unit called "subframe". One subframe is composed of two slots (one slot has 0.5 milliseconds). One slot is composed of seven OFDM symbols for normal cyclic prefix (CP) or six OFDM symbols for extended CP.

[0005] Figure 1 An example of a shortened TTI of normal CP is illustrated. When the TTI length is 0.5 milliseconds (= 1 slot), two TTIs are set per millisecond. When one slot is divided into a TTI composed of four OFDM symbols and a TTI composed of three OFDM symbols, four TTIs are set per millisecond. When the TTI length is one OFDM symbol, fourteen TTIs are set per millisecond.

[0006] Shortening the TTI length makes it possible to reduce the latency for CQI reporting and thus increase the frequency of CQI reporting, which has the advantage that the difference between the CQI report and the actual channel quality is reduced.

[0007] List of Citations

[0008] Non-Patent Literature

[0009] NPL 1

[0010] RP-150465, "New SI proposal: Study on Latency reduction techniques for LTE", Ericsson, Huawei, March 2015

[0011] NPL 2

[0012] 3GPP TR 36.211 V13.0.0, "Physical channels and modulation (Release 13)", December 2015 SUMMARY

[0013] When the TTI length is shortened, the length of a short TTI (hereinafter, "sTTI") can be different between downlink (DL) and uplink (UL). However, in legacy LTE / LTE-Advanced, the TTI length is the same between DL and UL, and the timing of data allocation, data transmission and reception, and feedback is commonly defined based on the same TTI length. For this reason, in the case where the DL and UL sTTI lengths are different from each other, it is necessary to redefine the timing of data allocation, data transmission and reception, and feedback.

[0014] An aspect of the present disclosure is to provide a base station, a terminal, and a communication method each of which is capable of appropriately configuring the timing of data allocation, data transmission and reception, and feedback for the case where the sTTI lengths are different between DL and UL.

[0015] A base station according to an aspect of the present disclosure includes a transmission section that transmits a downlink signal using a first short transmission time interval (sTTI) that is shorter in length than a TTI and used for downlink, and a reception section that receives an uplink signal using a second sTTI that is shorter in length than the TTI and used for uplink, the reception section receiving the uplink signal in the second sTTI located after a predetermined interval from a transmission timing of the downlink signal when the length of the first sTTI is shorter than the second sTTI, the predetermined interval being configured based on the length of the first sTTI.

[0016] A terminal according to an aspect of the present disclosure includes a reception section that receives a downlink signal using a first short transmission time interval (sTTI) that is shorter in length than a TTI and used for downlink, and a transmission section that transmits an uplink signal using a second sTTI that is shorter in length than the TTI and used for uplink, the transmission section transmitting the uplink signal in the second sTTI located after a predetermined interval from a reception timing of the downlink signal when the length of the first sTTI is shorter than the second sTTI, the predetermined interval being configured based on the length of the first sTTI.

[0017] A communication method according to an aspect of the present disclosure includes transmitting a downlink signal using a first short transmission time interval (sTTI) shorter in length than a TTI and used for a downlink, and receiving an uplink signal using a second sTTI shorter in length than the TTI and used for an uplink, when the first sTTI is shorter in length than the second sTTI, receiving the uplink signal in the second sTTI located after a predetermined interval from a transmission timing of the downlink signal, the predetermined interval being configured based on the length of the first sTTI.

[0018] A communication method according to an aspect of the present disclosure includes receiving a downlink signal using a first short transmission time interval (sTTI) shorter in length than a TTI and used for a downlink, and transmitting an uplink signal using a second sTTI shorter in length than the TTI and used for an uplink, when the first sTTI is shorter in length than the second sTTI, transmitting the uplink signal in the second sTTI located after a predetermined interval from a reception timing of the downlink signal, the predetermined interval being configured based on the length of the first sTTI.

[0019] A base station according to an aspect of the present disclosure includes a transmitter that transmits a downlink signal to a terminal in a first short transmission time interval (sTTI) shorter than a subframe, and a receiver that receives an uplink signal transmitted from the terminal in a second sTTI shorter than the subframe and longer than the first sTTI, wherein the receiver receives the uplink signal transmitted in the second sTTI after a determined number of first sTTIs from a transmission timing of the downlink signal, and the determined number is applied to all first sTTIs of the subframe.

[0020] A terminal according to an aspect of the present disclosure includes a receiver that receives a downlink signal transmitted from a base station in a first short transmission time interval (sTTI) shorter than a subframe, and a transmitter that transmits an uplink signal to the base station in a second sTTI shorter than the subframe and longer than the first sTTI, wherein the transmitter transmits the uplink signal in the second sTTI after a determined number of first sTTIs from a reception timing of the downlink signal, and the determined number is applied to all first sTTIs of the subframe.

[0021] A communication method according to an aspect of the present disclosure includes transmitting a downlink signal to a terminal in a first short transmission time interval sTTI shorter than a subframe, and receiving an uplink signal transmitted from the terminal in a second sTTI shorter than the subframe and longer than the first sTTI, wherein the receiving includes receiving the uplink signal transmitted in the second sTTI after a determined number of first sTTIs from a transmission timing of the downlink signal, and the determined number is applied to all of the first sTTIs of the subframe.

[0022] A communication method according to an aspect of the present disclosure includes receiving a downlink signal transmitted from a base station in a first short transmission time interval sTTI shorter than a subframe, and transmitting an uplink signal to the base station in a second sTTI shorter than the subframe and longer than the first sTTI, wherein the transmitting includes transmitting the uplink signal in the second sTTI after a determined number of first sTTIs from a reception timing of the downlink signal, and the determined number is applied to all of the first sTTIs of the subframe.

[0023] An integrated circuit controlling a process according to an aspect of the present disclosure, the process including transmitting a downlink signal to a terminal in a first short transmission time interval sTTI shorter than a subframe, and receiving an uplink signal transmitted from the terminal in a second sTTI shorter than the subframe and longer than the first sTTI, wherein the receiving includes receiving the uplink signal transmitted in the second sTTI after a determined number of first sTTIs from a transmission timing of the downlink signal, and the determined number is applied to all of the first sTTIs of the subframe.

[0024] An integrated circuit controlling a process according to an aspect of the present disclosure, the process including receiving a downlink signal transmitted from a base station in a first short transmission time interval sTTI shorter than a subframe, and transmitting an uplink signal to the base station in a second sTTI shorter than the subframe and longer than the first sTTI, wherein the transmitting includes transmitting the uplink signal in the second sTTI after a determined number of first sTTIs from a reception timing of the downlink signal, and the determined number is applied to all of the first sTTIs of the subframe.

[0025] Note that the above-mentioned general or specific aspects can be implemented by a system, apparatus, method, integrated circuit, computer program or recording medium, or any combination of a system, apparatus, method, integrated circuit, computer program and recording medium.

[0026] According to an aspect of the present disclosure, data allocation, data transmission and reception, and the timing of feedback can be appropriately configured for a case where the sTTI length is different between UL and DL.

[0027] The specification and drawings disclose more advantages and effects in an aspect of the present disclosure. These advantages and / or effects are provided by several embodiments and features disclosed in the specification and drawings, but all of these advantages and / or effects are not necessarily required to obtain one or more of the same. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a diagram illustrating exemplary TTI lengths;

[0029] Figure 2 is a block diagram illustrating a main configuration of a base station according to Embodiment 1;

[0030] Figure 3 is a block diagram illustrating a main configuration of a terminal according to Embodiment 1;

[0031] Figure 4 is a block diagram illustrating a configuration of a base station according to Embodiment 1;

[0032] Figure 5 is a block diagram illustrating a configuration of a terminal according to Embodiment 1;

[0033] Figure 6 is a diagram illustrating exemplary transmission and reception timing in UL data allocation according to Embodiment 1 (Operation Example 1-1);

[0034] Figure 7 is a diagram illustrating exemplary transmission and reception timing in UL data allocation according to Embodiment 1 (Operation Example 1-2);

[0035] Figure 8 is a diagram illustrating other exemplary transmission and reception timing in UL data allocation according to Embodiment 1 (Operation Example 1-2);

[0036] Figure 9 is a diagram illustrating exemplary transmission and reception timing in UL data allocation according to Embodiment 1 (Operation Example 1-3);

[0037] Figure 10 is a diagram illustrating other exemplary transmission and reception timing in UL data allocation according to Embodiment 1 (Operation Example 1-3);

[0038] Figure 11 is a diagram illustrating exemplary transmission and reception timing in DL data allocation according to Embodiment 1 (Operation Example 2-1);

[0039] Figure 12is a diagram illustrating exemplary transmission and reception timing in DL data allocation according to Embodiment 1 (Operation Example 2-2);

[0040] Figure 13A is a diagram illustrating other exemplary transmission and reception timing in DL data allocation according to Embodiment 1 (Operation Example 2-2);

[0041] Figure 13B is a diagram illustrating other exemplary transmission and reception timing in DL data allocation according to Embodiment 1 (Operation Example 2-2);

[0042] Figure 14 is a diagram illustrating other exemplary transmission and reception timing in DL data allocation according to Embodiment 1 (Operation Example 2-3);

[0043] Figure 15 is a diagram illustrating exemplary transmission and reception timing in UL data allocation according to Embodiment 2;

[0044] Figure 16 is a diagram illustrating other exemplary transmission and reception timing in DL data allocation according to Embodiment 2;

[0045] Figure 17 is a diagram illustrating exemplary transmission and reception timing in UL data allocation according to Embodiment 3;

[0046] Figure 18 is a diagram illustrating other exemplary transmission and reception timing in UL data allocation according to Embodiment 3; and

[0047] Figure 19 is a diagram illustrating exemplary transmission and reception timing in UL data allocation according to Embodiment 4. DETAILED DESCRIPTION

[0048] [BACKGROUND OF THE VARIOUS ASPECTS OF THE DISCLOSURE]

[0049] 3GPP uses OFDM in DL and single carrier transmission in UL.

[0050] In order to maintain single carrier transmission in UL, a reference signal (Demodulation Reference Signal: DMRS) and a data signal (Physical Uplink Shared Channel: PUSCH) cannot be mapped to the same symbol, which causes a problem in that overhead for the reference signal increases. In addition, a terminal (User Equipment: UE) transmits a signal in UL so that transmission power per time unit is low compared to DL in which a base station (eNB) transmits a signal. Thus, in UL, the UE needs to transmit a signal while spreading resources in a time domain to secure a desired reception power in the eNB.

[0051] Meanwhile, since OFDM is used in the DL, frequency multiplexing of reference signals and data signals (Physical Downlink Shared Channel: PDSCH) is easy, and the introduction of sTTI (shortening of TTI length) is easy compared to the UL. Further, DL traffic is considered large compared to UL traffic, and latency reduction is more required in the DL.

[0052] As described above, in shortening the TTI length, sTTI shorter than the sTTI in the UL can be configured in the DL.

[0053] In this regard, in an aspect of the present disclosure, an object is to appropriately define data allocation, transmission and reception timing of data and feedback in a case where the sTTI length is different between the DL and the UL; particularly, in a case where the length of sTTI for the DL (hereinafter, referred to as "DL sTTI") is shorter than that of sTTI for the UL (hereinafter, referred to as "UL sTTI").

[0054] Hereinafter, a detailed description will be given of embodiments of the present disclosure with reference to the accompanying drawings.

[0055] [Overview of Communication System]

[0056] The communication system according to each embodiment of the present disclosure includes a base station 100 and a terminal 200.

[0057] Figure 2 is a block diagram illustrating a main configuration of the base station 100 according to the embodiments of the present disclosure. In the following description of the embodiments, the same portions in the drawings are denoted with the same reference numerals, and repeated explanation is omitted. Figure 2 In the base station 100 illustrated, the transmission section 106 transmits a downlink signal using a first short transmission time interval (sTTI) (DL sTTI) shorter than a TTI and used for downlink, and the reception section 107 receives an uplink signal using a second sTTI (UL sTTI) shorter than a TTI and used for uplink. When the length of the first sTTI is shorter than that of the second sTTI, the reception section 107 receives the uplink signal using the second sTTI located after a predetermined interval from the transmission timing of the downlink signal, the predetermined interval being configured (configured using the length of the first sTTI as a basis for configuring the predetermined interval) based on the length of the first sTTI.

[0058] Figure 3 is a block diagram illustrating a main configuration of the terminal 200 according to each embodiment of the present disclosure. In the following description of the embodiments, the same portions in the drawings are denoted with the same reference numerals, and repeated explanation is omitted. Figure 3In the illustrated terminal 200, the reception section 201 receives a downlink signal using a first short transmission time interval (sTTI) (DL sTTI) that is shorter in length than the TTI and used for the downlink, and the transmission section 212 transmits an uplink signal using a second sTTI (UL sTTI) that is shorter in length than the TTI and used for the uplink. When the length of the first sTTI is shorter than that of the second sTTI, the transmission section 212 transmits the uplink signal using the second sTTI that is located a predetermined interval after the reception timing of the downlink signal, the predetermined interval being configured (configured using the length of the first sTTI as a basis for configuring the predetermined interval) on the basis of the length of the first sTTI.

[0059] Also, in the following, UL data signals and DL data signals allocated using sTTIs (DL sTTI and UL sTTI) are referred to as "sPUSCH" and "sPDSCH", respectively, and a downlink control signal (physical downlink control channel: PDCCH) to which a UL grant or a DL assignment is mapped and allocated using a DL sTTI is referred to as "sPDCCH".

[0060] (Embodiment 1)

[0061] [Configuration of base station]

[0062] Figure 4 is a block diagram illustrating a configuration of a base station 100 according to Embodiment 1. In Figure 4 In the illustrated configuration, the base station 100 includes an sTTI determination section 101, an sPDCCH generation section 102, an error correction encoding section 103, a modulation section 104, a signal allocation section 105, a transmission section 106, a reception section 107, a signal demultiplexing section 108, an ACK / NACK reception section 109, a demodulation section 110, an error correction decoding section 111, and an ACK / NACK generation section 112.

[0063] The sTTI determination section 101 determines DL and UL sTTI lengths. The sTTI determination section 101 outputs sTTI information indicating the determined sTTI lengths to the sPDCCH generation section 102, the signal allocation section 105, and the signal demultiplexing section 108. In addition, the sTTI determination section 101 outputs the sTTI information as upper layer signaling to the error correction encoding section 103.

[0064] The sPDCCH generating section 102 determines the data size that allows sTTI transmission and reception on the basis of the sTTI information input from the sTTI determining section 101. The sPDCCH generating section 102 generates an sPDCCH containing DL or UL resource assignment information (e.g., DL assignment or UL grant). The sPDCCH generating section 102 outputs the generated sPDCCH to the signal allocating section 105 so as to be transmitted to the terminal 200. Also, the sPDCCH generating section 102 outputs the DL resource assignment information to the signal allocating section 105 and outputs the UL resource assignment information to the signal demultiplexing section 108.

[0065] Further, the sPDCCH generating section 102 determines whether it is necessary to retransmit the DL data signal on the basis of the content (ACK or NACK) of the ACK / NACK signal (i.e., ACK / NACK signal for the DL data signal (sPDSCH) signal) input from the ACK / NACK receiving section 109 and generates an sPDCCH in accordance with the determination result.

[0066] Note that the data allocation (DL assignment and UL grant), data transmission and reception (PDSCH and PUSCH), and transmission and reception timing of feedback (ACK / NACK signal) in the base station 100 will be described in detail hereinafter.

[0067] The error correction encoding section 103 performs error correction encoding on the transmission data signal (DL data signal) and upper layer signaling input from the sTTI determining section 101 and outputs the encoded signal to the modulation section 104.

[0068] The modulation section 104 applies modulation processing to the signal received from the error correction encoding section 103 and outputs the modulated signal to the signal allocating section 105.

[0069] The signal allocating section 105 allocates the signal received from the modulation section 103, the control signal (sPDCCH) received from the sPDCCH generating section 102, or the ACK / NACK signal (i.e., ACK / NACK signal for the UL data signal (sPUSCH)) received from the ACK / NACK generating section 112 to a predetermined downlink resource on the basis of the sTTI information input from the sTTI determining section 101. The allocation of the control signal (sPDCCH) or the data signal (sPDSCH) to the predetermined resource forms a transmission signal. The transmission signal thus formed is output to the transmission section 106.

[0070] The transmission section 106 applies radio transmission processing such as up-conversion to the transmission signal input from the signal allocating section 105 and transmits the processed signal to the terminal 200 via an antenna.

[0071] The reception section 107 receives a signal transmitted from the terminal 200 via an antenna, applies radio reception processing such as frequency conversion to the received signal, and outputs the processed signal to the signal demultiplexing section 108.

[0072] The signal demultiplexing section 108 identifies the reception frequency and time timing for the sPUSCH (UL data signal) and ACK / NACK signal on the basis of the UL resource assignment information input from the sPDCCH generating section 102 and the sTTI information input from the sTTI determining section 101. The signal demultiplexing section 108 demultiplexes the UL data signal from the received signal and outputs the acquired signal to the demodulation section 110, and demultiplexes the ACK / NACK signal from the received signal and outputs the acquired signal to the ACK / NACK reception section 109.

[0073] The ACK / NACK reception section 109 outputs the content (ACK or NACK) of the ACK / NACK signal for the DL data signal input from the signal demultiplexing section 108 to the sPDCCH generating section 102.

[0074] The demodulation section 110 applies demodulation processing to the signal input from the signal demultiplexing section 108 and outputs the signal thus acquired to the error correction decoding section 111.

[0075] The error correction decoding section 111 decodes the signal input from the demodulation section 110 to acquire the data signal (UL data signal) received from the terminal 200. The error correction decoding section 111 outputs the UL data signal to the ACK / NACK generating section 112.

[0076] The ACK / NACK generating section 112 detects whether the UL data signal input from the error correction decoding section 111 has an error using a cyclic redundancy check (CRC) and outputs the detection result as an ACK / NACK signal to the signal assignment section 105.

[0077] [Configuration of terminal]

[0078] Figure 5 is a block diagram illustrating the configuration of the terminal 200 according to the present embodiment. In Figure 5 , the terminal 200 includes a reception section 201, a signal demultiplexing section 202, a demodulation section 203, an error correction decoding section 204, an sTTI configuration section 205, an error determining section 206, an ACK / NACK generating section 207, an sPDCCH reception section 208, an error correction encoding section 209, a modulation section 210, a signal assignment section 211, and a transmission section 212.

[0079] The reception section 201 receives a received signal via an antenna, and applies reception processing such as frequency conversion to the received signal, and outputs the processed signal to the signal demultiplexing section 202.

[0080] The signal demultiplexing section 202 demultiplexes a signal (sPDCCH signal) mapped to a resource to which an sPDCCH can be allocated on the basis of a DL sTTI length input from the sTTI configuring section 205, and outputs the acquired signal to the sPDCCH reception section 208. Further, the signal demultiplexing section 202 demultiplexes a DL data signal (sPDSCH) from the received signal on the basis of DL resource allocation information input from the sPDCCH reception section 208, and outputs the acquired signal to the demodulation section 203.

[0081] The demodulation section 203 demodulates a signal received from the signal demultiplexing section 202, and outputs the demodulated signal to the error correction decoding section 204.

[0082] The error correction decoding section 204 decodes a demodulated signal received from the demodulation section 203, and outputs the acquired received data signal. Further, the error correction decoding section 204 outputs the received data signal to the error determination section 206. Further, the error correction decoding section 204 decodes a demodulated signal received from the demodulation section 203, and outputs upper layer signaling (including sTTI information) acquired thereby to the sTTI configuring section 205.

[0083] The sTTI configuring section 205 configures DL and UL sTTI lengths on the basis of sTTI information input from the error correction decoding section 204, and then outputs information indicating the configured DL sTTI length to the signal demultiplexing section 202, and outputs information indicating the configured UL sTTI length to the signal allocating section 211.

[0084] The error determination section 206 uses CRC to detect whether or not a received data signal has an error, and outputs the detection result to the ACK / NACK generating section 207.

[0085] The ACK / NACK generating section 207 generates an ACK when there is no error, or generates a NACK when there is an error, on the basis of the detection result of a received data signal input from the error determination section 206, and outputs the generated ACK / NACK signal to the signal allocating section 211.

[0086] The sPDCCH receiving section 208 extracts resource assignment information (DL resource assignment information and UL resource assignment information) from the sPDCCH received from the signal demultiplexing section 202, and then outputs the DL resource assignment information to the signal demultiplexing section 202 and the UL resource assignment information to the signal allocating section 211.

[0087] The error correction encoding section 209 performs error correction encoding on the transmission data signal (UL data signal), and outputs the encoded data signal to the modulation section 210.

[0088] The modulation section 210 modulates the data signal received from the error correction encoding section 209, and outputs the modulated data signal to the signal allocating section 211.

[0089] The signal allocating section 211 allocates the data signal input from the modulation section 210 to resources on the basis of the information indicating the UL sTTI length received from the sTTI configuring section 205 and the UL resource assignment information received from the sPDCCH receiving section 207, and outputs the resultant signal to the transmission section 212. Further, the signal allocating section 211 allocates the ACK / NACK signal input from the ACK / NACK generating section 207 to the ACK / NACK resource, or multiplexes the ACK / NACK signal to the UL data signal, and outputs the resultant signal to the transmission section 212.

[0090] Note that the data allocation (DL allocation and UL grant), the data (PDSCH and PUSCH), and the transmission and reception timing of the feedback (ACK / NACK signal) in the terminal 200 will be described in detail below.

[0091] The transmission section 212 applies transmission processing such as up-conversion to the signal input from the signal allocating section 211, and outputs the processed signal via an antenna.

[0092] Further, the terminal 200 determines whether it is necessary to retransmit the UL data signal on the basis of the content (ACK or NACK) of the ACK / NACK signal (i.e., the ACK / NACK signal for the UL data signal (sPUSCH) signal) demultiplexed from the received signal in the signal demultiplexing section 202, and retransmits the sPUSCH (not shown) in accordance with the determination result.

[0093] [Operation of the base station 100 and the terminal 200]

[0094] The operation of the base station 100 and the terminal 200 each configured in the above-described manner will be described in detail.

[0095] In Embodiment 1, when the DL sTTI and the UL sTTI length are different from each other and the DL sTTI length is shorter than the UL sTTI length, the base station 100 and the terminal 200 determine the transmission and reception timing of data allocation (UL grant in sPDCCH and DL allocation), data (sPUSCH and sPDSCH), and feedback (ACK / NACK signal) based on the DL sTTI length.

[0096] More specifically, with respect to DL data, the terminal 200 (transmission part 212) sets the sPDCCH including the DL allocation and the sTTI to which the sPDSCH is to be allocated by this DL allocation to the same DL sTTI. In addition, the terminal 200 transmits the ACK / NACK signal for the sPDSCH in the UL sTTI located after a predetermined interval from the DL sTTI in which the sPDSCH is received (i.e., the DL sTTI in which the DL allocation is received), and this predetermined interval is configured based on the DL sTTI length. In other words, the base station 100 (reception part 107) receives the ACK / NACK signal for the sSDSCH in the UL sTTI located after a predetermined interval configured based on the DL sTTI length from the DL sTTI in which the sPDSCH is transmitted (the DL sTTI in which the DL allocation of the sPDSCH is transmitted).

[0097] In addition, with respect to UL data, the terminal 200 (transmission part 212) transmits the sPUSCH in the UL sTTI located after a predetermined interval from the reception timing of the sPDCCH including the UL grant, and this predetermined interval is configured based on the DL sTTI length. In other words, the base station 100 (reception part 107) receives the PUSCH in the UL sTTI located after a predetermined interval configured based on the DL sTTI length from the transmission timing of the sPDCCH including the UL grant.

[0098] Furthermore, the base station 100 (transmission part 106) transmits the ACK / NACK signal for the sPUSCH in the DL sTTI located after a predetermined interval from the UL sTTI in which the sPUSCH is received, and this predetermined interval is configured based on the DL sTTI length. In other words, the terminal 200 (reception part 201) receives the ACK / NACK signal for the sPUSCH in the DL sTTI located after a predetermined interval from the UL sTTI in which the sPUSCH is transmitted.

[0099] When the UL timing determined based on the DL sTTI length does not match the boundary between the UL sTTIs, the base station 100 and the terminal 200 delay the transmission and reception of the UL signal (sPUSCH or ACK / NACK signal) to the timing matching the boundary between the UL sTTIs.

[0100] For example, the base station 100 and the terminal 200 define the timing of data allocation, data transmission and reception, and feedback (transmission timing of the second signal with respect to the first signal) as follows:

[0101] Timing for DL data

[0102] DL allocation in sPDCCH-sPDSCH: Same sTTI

[0103] sPDSCH-ACK / NACK feedback: At least after X DL sTTIs

[0104] Timing for UL data

[0105] UL grant in sPDCCH-sPUSCH: At least after X DL sTTIs

[0106] sPUSCH-ACK / NACK feedback: At least after X DL sTTIs

[0107] Note that the expression "at least after X DL sTTIs" means that there is an interval of at least (X-1) sTTIs from the completion of transmission and reception of the first signal (DL allocation, sPDSCH, UL grant, or sPUSCH) until the start of transmission and reception of the second signal (sPDSCH, ACK / NACK feedback, sPUSCH, or ACK / NACK feedback), and the second signal is allocated to the exactly first sTTI after the interval (the exactly first sTTI among the sTTIs after the interval).

[0108] Hereinafter, the operation of data allocation, data transmission and reception, and feedback in the base station 100 and the terminal 200 will be described in detail.

[0109] First, an operation example in UL data allocation will be described. In UL data allocation, synchronous HARQ is assumed. Note that in the following operation example, the HARQ process ID is shown for description, the HARQ process ID is not indicated to the terminal 200, and the UL sTTI number and the HARQ process ID are associated with each other in the base station 100 and the terminal 200.

[0110] <Operation Example 1-1: UL data allocation (UL seven-symbol sTTI and DL three / four-symbol sTTI)>

[0111] Figure 6An example of the exemplary transmission and reception timing of the sPDCCH and sPUSCH to which the UL grant indicating the transmission of the UL data signal (sPUSCH) is mapped, and the transmission and reception timing of the sPUSCH and the ACK / NACK signal for the sPUSCH in operation example 1-1 is illustrated.

[0112] In operation example 1-1, as shown in Figure 6 , the UL sTTI length is set to seven symbols, and the DL sTTI length is set to three / four symbols, while X is set to equal 4. Among the three / four symbol sTTI, the former half of four symbols and the latter half of three symbols in one slot form sTTI respectively (i.e., two sTTI in one slot) (see, for example, Figure 1 ). More specifically, in Figure 6 , each subframe has four DL sTTI, and DL sTTI #0 to #19 are allocated from subframes #0 to #4. Also, in Figure 6 , each subframe has two UL sTTI, and UL sTTI #0 to #9 are allocated from subframes #0 to #4.

[0113] In operation example 1-1, the number of DL sTTI (four DL sTTI per subframe) is twice the number of UL sTTI (two UL sTTI per subframe).

[0114] With respect to the UL grant and sPUSCH, when X = 4, the base station 100 and the terminal 200 start the transmission and reception of the sPUSCH at least four DL sTTI after the transmission and reception of the UL grant (sPDCCH) based on the DL sTTI length. More specifically, there is an interval of at least three (= X - 1) DL sTTI from the completion of the transmission and reception of the UL grant until the start of the transmission and reception of the sPUSCH. In other words, the base station 100 and the terminal 200 perform the transmission and reception of the sPUSCH in the exactly first UL sTTI located at an interval of three DL sTTI after the transmission and reception timing of the UL grant.

[0115] For example, when the base station 100 transmits the UL grant of HARQ process ID #0 in DL sTTI #0, the timing at an interval of three DL sTTI from the timing of the completion of the transmission and reception of the UL grant (DL sTTI #0) is DL sTTI #4. Thus, the terminal 200 transmits the sPUSCH of HARQ process ID #0 in UL sTTI #2 which is the same timing as DL sTTI #4.

[0116] Similarly, regarding sPUSCH and ACK / NACK signals, when X = 4, base station 100 and terminal 200 begin transmitting and receiving ACK / NACK signals for sPUSCH at least four DL sTTIs after the transmission and reception of sPUSCH, based on the DL sTTI length. More specifically, there is at least a three (=X-1) DL sTTI interval from the completion of sPUSCH transmission and reception until the start of ACK / NACK signal transmission and reception. In other words, base station 100 and terminal 200 perform ACK / NACK signal transmission and reception in exactly the first DL sTTI after the three DL sTTI interval following the timing of sPUSCH transmission and reception.

[0117] For example, when terminal 200 sends sPUSCH for HARQ processing ID #0 in UL sTTI #2, the timing after three DL sTTI intervals from the timing of completing the transmission and reception of sPUSCH is DL sTTI #9. Therefore, base station 100 sends an ACK / NACK signal for sPUSCH for HARQ processing ID #0 in DL sTTI #9.

[0118] As described above, when X=4, base station 100 and terminal 200 allocate UL license and sPUSCH, as well as sPUSCH and ACK / NACK signals, while inserting at least three DL sTTIs.

[0119] It is important to note that, in Figure 6 In this context, the number of symbols used for the interval of the three DL sTTIs varies depending on the combination of DL sTTIs forming the interval. More specifically, in the cases of DL sTTIs #1, #2, and #3, the interval of the three DL sTTIs comprises ten OFDM symbols, but in the cases of DL sTTIs #6, #7, and #8, the interval of the three DL sTTIs comprises eleven OFDM symbols. This is because a DL sTTI can consist of either four or three symbols.

[0120] Furthermore, in Operation Example 1-1, a restriction is applied to the UL license such that the UL license is at least (X-1) DL sTTIs at the time of the boundary between the UL sTTI and the UL sTTI. Figure 6 The timing preceding the three DLsTTIs in the sequence is only mapped to the last DLsTTI. Utilizing this limitation, as... Figure 6 As shown, UL licenses are mapped to half of multiple DL sTTIs, and UL licenses are not mapped to the remaining half. Therefore, compared to the case where terminal 200 monitors UL licenses in all DL sTTIs, the possibility of erroneous detection of UL licenses (false alarms) can be reduced.

[0121] Further, in operation example 1-1, the DL sTTI in which the ACK / NACK signal is transmitted and received is different from the DL sTTI in which the UL grant is transmitted and received. Thus, since the resource for the UL grant is different from the resource for the ACK / NACK signal, the degree of congestion of the resource mapped to the control signal is advantageously mitigated. Therefore, it is possible to avoid the situation that the UL data allocation must be limited due to the lack of the resource for the control signal in the DL.

[0122] Next, when the terminal 200 receives the ACK / NACK signal for the HARQ process ID #0 in the DL sTTI #9 in the Figure 6 Three different methods (options 1 to 3) can be used for the operation when the terminal 200 receives the ACK / NACK signal for the HARQ process ID #0 in the DL sTTI #9 in

[0123] Option 1: The terminal 200 attempts to detect the UL grant in the DL sTTI #10 in which the UL grant corresponding to the same HARQ process ID #0 is transmitted after receiving the ACK / NACK signal in the DL sTTI #9, regardless of whether the ACK / NACK signal is ACK or NACK. When the UL grant is detected in the DL sTTI #10, the terminal 200 discards the ACK / NACK signal and transmits the sPUSCH according to the indication of the UL grant. Meanwhile, when the UL grant is not detected in the DL sTTI #10, the terminal 200 does not transmit the UL data signal (sPUSCH) for the HARQ process ID #0 when the ACK / NACK signal received in the DL sTTI #9 is ACK, but transmits the retransmission signal for the HARQ process ID #0 in the UL sTTI #7 when the ACK / NACK signal received in the DL sTTI #9 is NACK.

[0124] Option 2: When the ACK / NACK signal received in the DL sTTI #9 is ACK, the terminal 200 attempts to detect the UL grant in the DL sTTI #10 in which the UL grant corresponding to the same HARQ process ID #0 is transmitted. When the UL grant is detected, the terminal 200 transmits the sPUSCH according to the indication of the UL grant. Meanwhile, when the UL grant is not detected, the terminal 200 does not transmit the UL data signal (sPUSCH) for the HARQ process ID #0. Also, when the ACK / NACK signal received in the DL sTTI #9 is NACK, the terminal 200 transmits the retransmission signal for the HARQ process ID #0 in the UL sTTI #7 without performing the detection of the UL grant in the DL sTTI #10 in which the UL grant corresponding to the same HARQ process ID #0 is transmitted.

[0125] Option 3: The terminal 200 attempts to detect a NACK in the DL sTTI #9. When a NACK is not detected in the DL sTTI #9, the terminal 200 attempts to detect an UL grant in the DL sTTI #10 in which an UL grant corresponding to the same HARQ process ID #0 is transmitted. When an UL grant is detected in the DL sTTI #10, the terminal 200 transmits an sPUSCH according to the indication of the UL grant. Meanwhile, when an UL grant is not detected in the DL sTTI #10, the terminal 200 does not transmit an UL data signal (sPUSCH) of the HARQ process ID #0. Also, when a NACK is detected in the DL sTTI #9, the terminal 200 transmits a retransmission signal of the HARQ process ID #0 in the UL sTTI #7 without performing detection of an UL grant in the DL sTTI #10 in which an UL grant corresponding to the same HARQ process ID #0 is transmitted.

[0126] As described above, in Options 1 and 2, it is assumed that an ACK or a NACK is always transmitted as an ACK / NACK signal as in the case of a conventional Physical HARQ Indicator Channel (PHICH), and the terminal 200 determines whether the signal indicates an ACK or a NACK. In Option 3, it is assumed that an ACK / NACK signal is transmitted only for a NACK (an error exists), and the terminal 200 detects the presence of the ACK / NACK signal.

[0127] In Option 1, since the terminal 200 always attempts to detect an UL grant, even when an ACK is erroneously detected as a NACK, it is possible to prevent a retransmission signal from being transmitted at a wrong timing as long as an UL grant is detected. In Options 2 and 3, since the terminal 200 does not perform detection of an UL grant when a NACK is detected, it is possible to save power consumption of the terminal 200.

[0128] Note that the minimum value of the number of UL HARQ processes is determined from the transmission interval of an sPUSCH for the same UL HARQ process ID. In Figure 6 In the example in FIG. 12, an sPUSCH of an UL HARQ process ID #0 is transmitted in the UL sTTI #2, and an ACK / NACK for the sPUSCH is transmitted in the DL sTTI #9. Thus, since whether retransmission is necessary is determined in the DL sTTI #9, the base station 100 can transmit an UL grant of the same UL HARQ process ID #0 in or after the DL sTTI #9. When the ACK / NACK is detected in the DL sTTI #9 (in the example in FIG. 12, the ACK / NACK is detected in the DL sTTI #9), the base station 100 transmits the UL grant in the DL sTTI #10. Figure 10When the UL grant is transmitted from the base station 100 in the DL sTTI #10 (which will be described in detail below), the UL sTTI #7 is the first UL sTTI from the terminal 200 to transmit the sPUSCH after the interval of three DL sTTIs. Thus, the timing to transmit the sPUSCH of the same UL HARQ process ID #0 can be transmitted becomes the interval of five UL sTTIs. When the transmission interval of the same UL HARQ process is five UL sTTIs, five UL HARQ processes can be transmitted in five UL sTTIs, so that the minimum value of the number of UL HARQ processes can be determined to be five.

[0129] Note that a number greater than 5 can also be configured as the number of UL HARQ processes. In this case, since the retransmission interval becomes long, the delay time increases. Further, when the number of UL HARQ processes increases to a large number, the required buffer increases accordingly, so that the number of UL HARQ processes is desirably configured with the minimum possible value.

[0130] Note that, in Figure 6 the base station 100 transmits the UL grant in the DL sTTI #10 which is the interval of three DL sTTIs before the UL sTTI #7, but does not transmit the UL grant in the DL sTTI #9. This is because there is no impact on the total amount of delay even when the UL grant is transmitted in the DL sTTI #10. Note that the number of UL HARQ processes can be determined in advance on the basis of the DL and UL sTTI lengths, and the minimum possible value can be identified and configured for the base station 100 and the terminal 200, respectively, as described above.

[0131] Note that, although attention is given to the HARQ process ID #0, the same applies to the other HARQ process IDs #2, #3, and #4 herein.

[0132] <Operation Example 1-2: UL Data Allocation (UL Three / Four Symbol sTTI and DL Two Symbol sTTI)>

[0133] Figure 7 An exemplary transmission and reception timing of the sPDCCH and sPUSCH to which the UL grant indicating the transmission of the UL data signal (sPUSCH) is mapped, and the transmission and reception timing of the sPUSCH and the ACK / NACK signal for the sPUSCH in Operation Example 1-2 are illustrated.

[0134] In Operation Example 1-2, as Figure 7 indicated, the UL sTTI length is set to three / four symbols, and the DL sTTI length is set to two symbols, and X is set to be equal to 4. More specifically, in the DL sTTI #10, the UL grant is transmitted from the base station 100 to the terminal 200, and the sPUSCH is transmitted from the terminal 200 to the base station 100 in the UL sTTI #7 which is the interval of three DL sTTIs.Figure 7 In Operation Example 1-1, each subframe has seven DL sTTIs, and DL sTTIs #0 to #27 are allocated from subframes #0 to #3. Also, in Figure 7 In Operation Example 1-2, each subframe has four UL sTTIs, and UL sTTIs #0 to #15 are allocated from subframes #0 to #3.

[0135] In Operation Example 1-2, the number of DL sTTIs (seven DL sTTIs per subframe) is four-sevenths (7 / 4) of the number of UL sTTIs (four UL sTTIs per subframe).

[0136] When X = 4, as in Operation Example 1-1, the base station 100 and the terminal 200 allocate the UL grant and the sPUSCH, and the sPUSCH and the ACK / NACK signal while inserting an interval of at least three DL sTTIs.

[0137] For example, regarding the UL grant and the sPUSCH, when the base station 100 transmits the UL grant of HARQ process ID #0 in DL sTTI #1, the timing after an interval of three DL sTTIs from the timing at which the transmission and reception of the UL grant are completed (DL sTTI #1) is DL sTTI #5. Since the timing of the DL sTTI #5 does not coincide with the boundary between the UL sTTIs, the terminal 200 delays the transmission of the sPUSCH until UL sTTI #3, which is the first UL sTTI located after the timing of the DL sTTI #5, and transmits the sPUSCH of HARQ process ID #0 in the UL sTTI #3.

[0138] Also, regarding the sPUSCH and the ACK / NACK signal, when the terminal 200 transmits the sPUSCH of HARQ process ID #0 in UL sTTI #3, the timing after an interval of three DL sTTIs from the timing at which the transmission and reception of the sPUSCH are completed (DL sTTI #6) is DL sTTI #10. Thus, the base station 100 transmits the ACK / NACK signal for the sPUSCH of HARQ process ID #0 in the DL sTTI #10.

[0139] In Operation Example 1-2, as in Operation Example 1-1, a restriction is applied to the UL grant so that the UL grant is mapped only to the last DL sTTI at a timing at least (X-1) DL sTTIs (three DL sTTIs in Figure 7 In Operation Example 1-2, as in Operation Example 1-1, a restriction is applied to the UL grant so that the UL grant is mapped only to the last DL sTTI at a timing at least (X-1) DL sTTIs (three DL sTTIs in Figure 7As shown. Thus, compared to the case where the terminal 200 monitors the UL grant in all the DL sTTIs, it is possible to reduce the possibility of erroneously detecting the UL grant (false alarm).

[0140] Further, in operation example 1-2, as in operation example 1-1, the DL sTTI in which the ACK / NACK signal is transmitted and received is different from the DL sTTI in which the UL grant is transmitted and received. Thus, since the resource for the UL grant is different from the resource for the ACK / NACK signal, it is advantageously mitigated to what extent the congestion of the resource to which the control signal is mapped. Thus, it is possible to avoid the situation where it is necessary to limit the UL data allocation due to the lack of the resource for the control signal in the DL.

[0141] However, in operation example 1-2, unlike operation example 1-1, the number of the DL sTTIs is seven-fourths (7 / 4) of the number of the UL sTTIs, so that it is impossible to map all the ACK / NACK signals and the UL grants to the different DL sTTIs.

[0142] In Figure 7 sTTI mapping, although the UL grant and the ACK / NACK signal are not mapped to the DL sTTI #11 and the DL sTTI #18, the UL grant and the ACK / NACK signal are mapped to the DL sTTI #10 and the DL sTTI #17.

[0143] At this point, in order to disperse the control signal resource, the base station 100 can make an adjustment to transmit the ACK / NACK signal of the same HARQ process ID as the UL grant of the HARQ process ID just before the DL sTTI in which this ACK / NACK signal is transmitted. Figure 8 An operation example of adjusting the DL sTTI to which the ACK / NACK signal is mapped is illustrated.

[0144] In Figure 8 sTTI mapping, the ACK / NACK signal of the HARQ process ID #0 mapped to the DL sTTI #10 in Figure 7 is mapped to the DL sTTI #11 just before the DL sTTI #12 in which the UL grant of the mapped HARQ process ID #0 is transmitted. Also, in Figure 8 sTTI mapping, the ACK / NACK signal of the HARQ process ID #4 mapped to the DL sTTI #17 in Figure 7 is mapped to the DL sTTI #18 just before the DL sTTI #19 in which the UL grant of the mapped HARQ process ID #4 is transmitted. Thus, the control signals (the UL grant and the ACK / NACK signal) are dispersedly mapped.

[0145] Note that, in terms of the delay, the mapping of the ACK / NACK signal can be performed at any interval as long as the interval is three DL sTTIs away from the same HARQ process ID's sPUSCH and the interval is the next sPUSCH three DL sTTIs away where the retransmission for the same HARQ process ID can be performed. Thus, even when the ACK / NACK signal for HARQ process ID #0 that has been mapped to DL sTTI #10 is mapped to DL sTTI #11 and the ACK / NACK signal for HARQ process ID #4 that has been mapped to DL sTTI #17 is mapped to DL sTTI #18, there is no problem in terms of the delay.

[0146] As Figure 8 delaying the ACK / NACK signal backward allows the base station 100 to determine whether to perform adaptive retransmission or non-adaptive retransmission on the basis of the state of backward scheduling, so that the scheduler flexibility of the base station 100 can be improved.

[0147] <Operation Example 1-3: UL Data Allocation (UL Seven-Symbol sTTI and DL Two-Symbol sTTI)>

[0148] Figure 9 An exemplary transmission and reception timing of the sPDCCH and sPUSCH to which the UL grant indicating the transmission of the UL data signal (sPUSCH) is mapped, and the transmission and reception timing of the sPUSCH and the ACK / NACK signal for the sPUSCH are illustrated in Operation Example 1-3.

[0149] In Operation Example 1-3, as shown in Figure 9 , the UL sTTI length is set to seven symbols and the DL sTTI length is set to two symbols, and X is set to be equal to 4. More specifically, in Figure 9 , each subframe has seven DL sTTIs, and DL sTTIs #0 to #27 are allocated from subframes #0 to #3. Also, in Figure 9 , each subframe has two UL sTTIs, and UL sTTIs #0 to #7 are allocated from subframes #0 to #3.

[0150] In other words, in Operation Example 1-3, the number of DL sTTIs (seven DL sTTIs per subframe) is seven-halves (7 / 2) times the number of UL sTTIs (two UL sTTIs per subframe).

[0151] When X = 4, the base station 100 and the terminal 200 allocate the UL grant and sPUSCH, and the sPUSCH and the ACK / NACK signal while inserting at least three DL sTTIs as in Operation Example 1-1.

[0152] For example, with respect to the UL grant and the sPUSCH, when the base station 100 transmits the UL grant of HARQ process ID #0 in the DL sTTI #3, the timing after the interval of three DL sTTIs from the timing at which the transmission and reception of the UL grant is completed (DL sTTI #3) is the DL sTTI #7. The terminal 200 transmits the sPUSCH of HARQ process ID #0 in the UL sTTI #2 which is the same timing as the DL sTTI #7.

[0153] Also, with respect to the sPUSCH and the ACK / NACK signal, when the terminal 200 transmits the sPUSCH of HARQ process ID #0 in the UL sTTI #2, the timing after the interval of three DL sTTIs from the timing at which the transmission and reception of the sPUSCH is completed (DL sTTI #10) is the DL sTTI #14. Thus, the base station 100 transmits the ACK / NACK signal for the sPUSCH of HARQ process ID #0 in the DL sTTI #14.

[0154] In operation example 1-3, as in operation example 1-1, a restriction is applied to the UL grant so that the UL grant is mapped only to the last DL sTTI at a timing at least (X-1) DL sTTIs (three DL sTTIs in Figure 9 from the timing of the boundary between the UL sTTIs. With this restriction, the UL grant is mapped to two DL TTIs in the DL sTTIs within a single subframe, and the UL grant is not mapped to the remaining five DL sTTIs, as shown in Figure 9 Thus, compared to the case in which the terminal 200 monitors the UL grant in all the DL sTTIs, it is possible to reduce the possibility of erroneously detecting the UL grant (false alarm).

[0155] Further, in operation example 1-3, as in operation example 1-1, the DL sTTI in which the ACK / NACK signal is transmitted and received is different from the DL sTTI in which the UL grant is transmitted and received. Thus, since the resource for the UL grant is different from the resource for the ACK / NACK signal, it is advantageously alleviated to what extent the congestion of the resource to which the control signal is mapped. Thus, it is possible to avoid the situation in which it is necessary to limit the UL data allocation due to the lack of the resource for the control signal in the DL.

[0156] However, in operation example 1-3, the number of DL sTTIs is seven-halves (7 / 2) times the number of UL sTTIs, so that it is not possible to map all the ACK / NACK signals and the UL grant to different DL sTTIs as in operation example 2.

[0157] At this point, in order to disperse control signal resources, the base station 100 can make an adjustment to transmit this ACK / NACK signal in a DL sTTI that is just before a DL sTTI in which an UL grant of the same HARQ process ID as the ACK / NACK signal is transmitted. Figure 10 An operation example of adjusting the DL sTTI to which the ACK / NACK signal is mapped is illustrated.

[0158] In Figure 10 , the ACK / NACK signal of HARQ process ID #0 mapped to the DL sTTI #14 in Figure 9 is mapped to the DL sTTI #16 (located two DL sTTIs behind the DL sTTI #14) that is just before the DL sTTI #17 in which the UL grant of HARQ process ID #0 is mapped. Also, in Figure 10 , the ACK / NACK signal of HARQ process ID #1 mapped to the DL sTTI #17 in Figure 9 is mapped to the DL sTTI #19 (located two DL sTTIs behind the DL sTTI #17) that is just before the DL sTTI #20 in which the UL grant of HARQ process ID #1 is mapped. Thus, the control signals (UL grant and ACK / NACK signal) are dispersedly mapped.

[0159] As in operation example 1-2, the mapping of the ACK / NACK signal can be performed at any interval in terms of delay, as long as the interval is three DL sTTIs from the same HARQ process ID and the interval is three DL sTTIs from the next sPUSCH in which retransmission for the same HARQ process ID can be performed. Thus, even when the ACK / NACK signal of HARQ process ID #0 that has been mapped to the DL sTTI #14 is mapped to the DL sTTI #16 and the ACK / NACK signal of HARQ process ID #1 that has been mapped to the DL sTTI #17 is mapped to the DL sTTI #19, there is no problem in terms of delay.

[0160] Delaying the ACK / NACK signal backward as in Figure 10 allows the base station 100 to determine whether to perform adaptive retransmission or non-adaptive retransmission on the basis of the state of backward scheduling, so that the scheduler flexibility of the base station 100 can be improved.

[0161] So far, operation examples 1-1, 1-2, and 1-3 in UL data allocation have been described.

[0162] Next, a description of an operation example in the DL data allocation will be given. In the DL data allocation, asynchronous HARQ is assumed. Further, the HARQ process ID is notified to the terminal 200 through the DL allocation.

[0163] Note that, although the following operation example will be described in a case where the serial HARQ process ID is allocated to the serial DL sTTI, it is by no means limited to this case.

[0164] <Operation Example 2-1: UL data allocation (UL seven-symbol sTTI and DL three / four-symbol sTTI)>

[0165] Figure 11 An exemplary transmission and reception timing of the sPDCCH and sPDSCH to which the DL allocation indicating the transmission of the DL data signal (sPDSCH) in Operation Example 2-1 is mapped, and a transmission and reception timing of the sPDSCH and the ACK / NACK signal for the sPDSCH are illustrated.

[0166] In Operation Example 2-1, as shown in Figure 11 , the UL sTTI length is set to seven symbols, and the DL sTTI length is set to three / four symbols, while X is set to equal to 4. More specifically, in Figure 11 , each subframe has four DL sTTIs, and DL sTTIs #0 to #11 are allocated from subframes #0 to #2. Also, in Figure 11 , each subframe has two UL sTTIs, and UL sTTIs #0 to #5 are allocated from subframes #0 to #2.

[0167] In other words, in Operation Example 2-1, as in Operation Example 1-1, the number of DL sTTIs (four DL sTTIs per subframe) is twice the number of UL sTTIs (two UL sTTIs per subframe).

[0168] With respect to the DL allocation and the sPDSCH, the base station 100 transmits the sPDSCH indicated by the DL allocation in the same DL sTTI as the DL sTTI in which the DL allocation is transmitted and received. For example, when the DL allocation of the HARQ process ID #0 is transmitted in the DL sTTI #0, the base station 100 transmits the sPDSCH in the same DL sTTI #0.

[0169] Also, regarding the sPDSCH and ACK / NACK signal, when X = 4, the base station 100 and the terminal 200 start transmission and reception of the ACK / NACK signal for the sPDSCH at least four DL sTTIs after the transmission and reception of the sPDSCH based on the DL sTTI length. More specifically, there is an interval of at least three (= X - 1) DL sTTIs from the completion of the transmission and reception of the sPDSCH until the start of the transmission and reception of the ACK / NACK signal. In other words, the base station 100 and the terminal 200 perform the transmission and reception of the ACK / NACK signal in the exactly first UL sTTI after the interval of three DL sTTIs from the transmission and reception timing of the sPDSCH.

[0170] For example, when the base station 100 transmits the sPDSCH of HARQ process ID #0 in the DL sTTI #0, the timing after the interval of three DL sTTIs from the completion of the transmission and reception of the sPDSCH (DL sTTI #0) is the DL sTTI #4. Thus, the terminal 200 transmits the ACK / NACK signal for the sPDSCH of HARQ process ID #0 in the UL sTTI #2 which is the same timing as the DL sTTI #4.

[0171] Note that, although attention is given to HARQ process ID #0, the same applies to other HARQ process IDs #2, #3, and #4 herein.

[0172] In Figure 11 In this case, the terminal 200 multiplexes or bundles a plurality of ACK / NACKs, for example, and transmits the ACK / NACK using the UL resource.

[0173] In LTE / LTE-Advanced, the start position of the UL resource for transmitting the ACK / NACK signal from the UE is indicated by an upper layer parameter called "N1_PUCCH", and the offset from the start position can be found from the (E)CCE number.

[0174] Meanwhile, in operation example 2-1, with respect to the sPDSCH and the ACK / NACK signal, the terminal 200 can identify the transmission position of the ACK / NACK signal from the DL assignment received in the DL sTTI having a larger sTTI number (i.e., located in a later DL sTTI) among the plurality of DL sTTIs used when receiving the sPDSCH for which the corresponding ACK / NACK signal is to be transmitted in the same UL sTTI. This is because the backward-located DL sTTI allows the scheduler to change the resource allocation considering the ACK / NACK resource later, thereby improving the scheduler flexibility. For example, in Figure 11 , the terminal 200 identifies the transmission position of the ACK / NACK signal from the DL assignment received in the sPDCCH in the DL sTTI #2 having a larger DL sTTI number between the DL sTTIs #1 and #2 used when receiving the sPDSCH corresponding to the ACK / NACK signal to be transmitted in the UL sTTI #3.

[0175] Further, with respect to the sPDSCH and the ACK / NACK signal, when the sPDSCH is actually received in one of the plurality of DL sTTIs used when receiving the sPDSCH for which the corresponding ACK / NACK signal is to be transmitted in the same UL sTTI, the terminal 200 identifies the transmission position of the ACK / NACK signal from the DL assignment received in the DL sTTI.

[0176] It is to be noted that the transmission position of the ACK / NACK signal is determined from the shift amount based on the DL sTTI and the shift amount based on the CCE number from the DL assignment of N1_PUCCH indicated by the upper layer. It is assumed that the shift amount based on the DL sTTI is predetermined. Also, for each DL sTTI, N1_PUCCH can be indicated by the upper layer.

[0177] <Operation example 2-2: DL data assignment (UL three / four-symbol sTTI and DL two-symbol sTTI)>

[0178] Figure 12 An exemplary transmission and reception timing of the sPDCCH and the sPDSCH to which the DL assignment indicating the transmission of the DL data signal (sPDSCH) is mapped, and the transmission and reception timing of the sPDSCH and the ACK / NACK signal for the sPDSCH are illustrated in operation example 2-2.

[0179] In operation example 2-2, as shown in Figure 12 , the UL sTTI length is set to three / four symbols, and the DL TTI length is set to two symbols, and X is set to be equal to 4. More specifically, in Figure 12In Operation Example 2-1, each subframe has seven DL sTTIs, and DL sTTIs #0 to #13 are allocated in subframes #0 and #1. Also, in Figure 12 In Operation Example 2-2, each subframe has four UL sTTIs, and UL sTTIs #0 to #7 are allocated in subframes #0 and #1.

[0180] In other words, in Operation Example 2-2, the number of DL sTTIs (seven DL sTTIs per subframe) is four-sevenths (7 / 4) of the number of UL sTTIs (four UL sTTIs per subframe), as in Operation Example 2-1.

[0181] As for the DL assignment and the sPDSCH, the base station 100 transmits the sPDSCH indicated by the DL assignment in the same DL sTTI as the DL sTTI in which the DL assignment is transmitted and received. For example, when the DL assignment of HARQ process ID #0 is transmitted in DL sTTI #0, the base station 100 transmits the sPDSCH in the same DL sTTI #0.

[0182] As for the sPDSCH and the ACK / NACK signal, when X = 4, the base station 100 and the terminal 200 start transmission and reception of the ACK / NACK signal for the sPDSCH at least four DL sTTIs away from the transmission and reception of the sPDSCH based on the DL sTTI length. More specifically, there is an interval of at least three (= X - 1) DL sTTIs from the completion of the transmission and reception of the sPDSCH until the start of the transmission and reception of the ACK / NACK signal. In other words, the base station 100 and the terminal 200 transmit and receive the ACK / NACK signal in the very first UL sTTI located at an interval of three DL sTTIs away from the transmission and reception timing of the sPDSCH.

[0183] For example, when the base station 100 transmits the sPDSCH of HARQ process ID #0 in DL sTTI #0, the timing at an interval of three DL sTTIs away from the timing of the completion of the transmission and reception of the sPDSCH (DL sTTI #0) is DL sTTI #4. Since the timing of the DL sTTI #4 does not match the boundary between the UL sTTIs, the terminal 200 delays the transmission of the ACK / NACK signal until UL sTTI #3, which is the very first UL sTTI located after the timing of the DL sTTI #4, and transmits the ACK / NACK signal for the sPDSCH of HARQ process ID #0 in UL sTTI #3.

[0184] Also, in Figure 12In the case where the number of DL sTTIs is seven-fourths (7 / 4) of the number of UL sTTIs, the terminal 200 transmits ACK / NACK signals for two DL sTTIs per UL sTTI, or transmits ACK / NACK signals for one DL sTTI per UL sTTI. In Figure 12 In the case where the number of DL sTTIs is seven-fourths (7 / 4) of the number of UL sTTIs, the terminal 200 transmits ACK / NACK signals for two DL sTTIs per UL sTTI, or transmits ACK / NACK signals for one DL sTTI per UL sTTI. In

[0185] Further, in the case where the number of DL sTTIs is seven-fourths (7 / 4) of the number of UL sTTIs, the terminal 200 transmits ACK / NACK signals for two DL sTTIs per UL sTTI, or transmits ACK / NACK signals for one DL sTTI per UL sTTI. In Figure 12 In the case where the number of DL sTTIs is seven-fourths (7 / 4) of the number of UL sTTIs, the terminal 200 transmits ACK / NACK signals for two DL sTTIs per UL sTTI, or transmits ACK / NACK signals for one DL sTTI per UL sTTI. In

[0186] It is to be noted that, for example, when an application such as interference control, CoMP, D2D, and the like is determined and used in units of subframes, it is advantageous to determine the usage method in units of subframes. In this regard, as shown in FIG. 13A or 13B, all ACK / NACK signals for DL data signals (sPDSCHs) allocated to the same subframe can be transmitted in the same subframe. In other words, the base station 100 and the terminal 200 transmit and receive ACK / NACK signals for a plurality of sPDSCHs transmitted and received in the same subframe in a plurality of UL sTTIs within a single subframe, respectively. Figure 13A

[0187] In the case where the number of DL sTTIs is seven-fourths (7 / 4) of the number of UL sTTIs, the terminal 200 transmits ACK / NACK signals for two DL sTTIs per UL sTTI, or transmits ACK / NACK signals for one DL sTTI per UL sTTI. In Figure 13A In the case where the number of DL sTTIs is seven-fourths (7 / 4) of the number of UL sTTIs, the terminal 200 transmits ACK / NACK signals for two DL sTTIs per UL sTTI, or transmits ACK / NACK signals for one DL sTTI per UL sTTI. In

[0188] As the first implementation method, Figure 12 ​The timing of the ACK / NACK signal shown is shifted backward by one UL sTTI. As a second implementation method, X = 4 is changed to X = 6. The value of X is configured so as to allow the ACK / NACK signal for the DL data signal (sPDSCH) allocated in the same subframe to be transmitted in the same subframe. Thus, it is advantageous to easily allocate interference control, CoMP, D2D, etc. of the UL subframe in units of subframes.

[0189] Note that the number of ACK / NACK signals transmitted in the UL sTTI is different between the first and second implementation methods, but the maximum value and the minimum value of the number of ACK / NACK signals are the same between the first and second implementation methods.

[0190] <Operation Example 2-3: DL Data Allocation (UL Seven-Symbol sTTI and DL Two-Symbol sTTI)>

[0191] Figure 14 Exemplary transmission and reception timings of sPDCCH and sPDSCH to which a DL allocation indicating transmission of a DL data signal (sPDSCH) is mapped in Operation Example 2-3, and transmission and reception timings of sPDSCH and an ACK / NACK signal for the sPDSCH are illustrated.

[0192] In Operation Example 2-3, as shown in Figure 14 , the UL sTTI length is set to seven symbols, and the DL sTTI length is set to two symbols, and X is set to equal 4. More specifically, in Figure 14 , each subframe has seven DL sTTIs, and DL sTTIs #0 to #13 are allocated in subframes #0 and #1. Also, in Figure 14 , each subframe has two UL sTTIs, and UL sTTIs #0 to #3 are allocated in subframes #0 and #1.

[0193] In other words, in Operation Example 2-3, as in Operation Example 1-3, the number of DL sTTIs (seven DL sTTIs per subframe) is seven-halves (7 / 2) times the number of UL sTTIs (two UL sTTIs per subframe).

[0194] With regard to the DL allocation and the sPDSCH, the base station 100 allocates the sPDSCH indicated by the DL allocation in the same DL sTTI as the DL sTTI in which the DL allocation is transmitted and received. For example, when the DL allocation of HARQ process ID #0 is transmitted in DL sTTI #0, the base station 100 transmits the sPDSCH in the same DL sTTI #0.

[0195] As for the sPDSCH and the ACK / NACK signal, when X = 4, the base station 100 and the terminal 200 start transmission and reception of the ACK / NACK signal for the sPDSCH after at least four DL sTTIs from the transmission and reception of the sPDSCH based on the DL sTTI length. More specifically, there is an interval of at least three (= X - 1) DL sTTIs from the completion of the transmission and reception of the sPDSCH until the start of the transmission and reception of the ACK / NACK signal. In other words, the base station 100 and the terminal 200 transmit and receive the ACK / NACK signal in the exactly first UL sTTI after the interval of three DL sTTIs from the transmission and reception timing of the sPDSCH.

[0196] For example, when the base station 100 transmits the sPDSCH of HARQ process ID #0 in the DL sTTI #0, the timing after the interval of three DL sTTIs from the completion of the transmission and reception of the sPDSCH (DL sTTI #0) is the DL sTTI #4. Since the timing of the DL sTTI #4 does not match the boundary between the DL sTTI and the UL sTTI, the terminal 200 delays the transmission of the ACK / NACK signal until the UL sTTI #2 which is the exactly first UL sTTI after the timing of the DL sTTI #4, and transmits the ACK / NACK signal for the sPDSCH of HARQ process ID #0 in the UL sTTI #2.

[0197] Also, in Figure 14 , since the number of DL sTTIs is two and a half times (7 / 2) the number of UL sTTIs, the terminal 200 transmits the ACK / NACK signal for four DL sTTIs per UL sTTI, or transmits the ACK / NACK signal for three DL sTTIs per UL sTTI. In Figure 14 , the ACK / NACK signal for four DL sTTIs is transmitted in the UL sTTI #2, and the ACK / NACK signal for three DL sTTIs is transmitted in the UL sTTI #3. As has been described, the maximum value of the number of ACK / NACK signals to be transmitted varies for each UL sTTI, so that the terminal 200 can change the format for the transmission of the ACK / NACK signal for each UL sTTI.

[0198] So far, Operation Examples 2-1, 2-2, and 2-3 in the DL data allocation have been described.

[0199] As described above, in Embodiment 1, the base station 100 and the terminal 200 transmit and receive downlink signals (sPDCCH, sPDSCH, and ACK / NACK signals) using DL sTTIs of which the length is shorter than TTIs, and transmit and receive uplink signals (sPUSCH and ACK / NACK signals) using UL sTTIs of which the length is shorter than TTIs. In this case, when the DL sTTI length is shorter than the UL sTTI length, the base station 100 and the terminal 200 transmit and receive the uplink signals in the UL sTTI located after a predetermined interval from the transmission timing of the downlink signals, the predetermined interval being configured based on the DL sTTI length. Also, when the determined transmission and reception timing does not match the boundary with the UL sTTI, the base station 100 and the terminal 200 delay the transmission and reception timing until the timing matching the boundary with the UL sTTI.

[0200] Thus, even when the DL and UL sTTI lengths are different from each other, the base station 100 and the terminal 200 can start the transmission and reception of signals from the boundary between the DL sTTIs and the boundary between the UL sTTIs. Therefore, according to Embodiment 1, the timing of data allocation, data transmission and reception, and feedback for the case where the DL and UL sTTI lengths are different from each other can be appropriately configured.

[0201] Note that, in Embodiment 1, an example in which the ACK / NACK signals are allocated to the ACK / NACK resources is shown, but the ACK / NACK resources can be Physical Uplink Control Channel (PUCCH) resources. Also, when the UL data signals are allocated, a method in which the ACK / NACK signals are multiplexed to the UL data signals and transmitted can be used. In this case, when there is even one UL sTTI to which the UL data signals are allocated among the plurality of UL sTTIs, the terminal 200 can transmit the ACK / NACK signals for the sPDSCHs transmitted in the plurality of DL sTTIs in the UL sTTI. With this configuration, the situation in which the PUCCH format and the PUSCH format coexist in a subframe no longer occurs, and the terminal 200 can advantageously transmit signals in a subframe using a single format.

[0202] Also, as for the combination of the DL and UL sTTI lengths, the operation of the present disclosure can be applied to combinations other than those shown in the operation example of Embodiment 1.

[0203] (Embodiment 2)

[0204] The basic configuration of the base station and the terminal according to Embodiment 2 is common to that of the base station 100 and the terminal 200 according to Embodiment 1, so reference will be made to Figure 4 and 5The base station and terminal according to Embodiment 2 are described.

[0205] In Example 2, when the lengths of DL and UL sTTI are different from each other and the length of DL sTTI is shorter than the length of UL sTTI, the base station 100 and the terminal 200 determine the timing of data allocation (UL permission and DL allocation in sPDCCH), data transmission and reception (sPUSCH and sPDSCH), and feedback (ACK / NACK signal) transmission and reception based on the length of DL sTTI and absolute time.

[0206] The term "absolute time" refers to a fixed length of time that takes into account processing delays or the time required for communication with higher layers.

[0207] Furthermore, when the UL timing determined based on the DL sTTI length does not match the boundary between the UL sTTI, the base station 100 and the terminal 200 delay the UL timing until the timing matches the boundary between the UL sTTI, as in Example 1.

[0208] More specifically, regarding DL data, base station 100 and terminal 200 transmit and receive ACK / NACK signals for sPDSCH within a UL sTTI after a predetermined interval following the transmission and reception timing of sPDSCH, and this predetermined interval is configured based on the DL sTTI length and absolute time.

[0209] Furthermore, regarding UL data, base station 100 and terminal 200 transmit and receive sPUSCH allocated by UL license within a UL sTTI located after a predetermined interval for transmitting and receiving the sPDCCH containing UL license, and this predetermined interval is configured based on the DL sTTI length and absolute time. Moreover, base station 100 and terminal 200 transmit and receive ACK / NACK signals for sPUSCH within a DL sTTI located after a predetermined interval for transmitting and receiving the sPUSCH, and this predetermined interval is configured based on the DL sTTI length and absolute time.

[0210] For example, base station 100 and terminal 200 may transmit and receive a second signal at a time elapsed after a predetermined number (X) of DL sTTI intervals, obtained by adding the absolute time (Y) to the first signal's transmission and reception timing. More specifically, base station 100 and terminal 200 define the timing for data allocation, data transmission and reception, and feedback (for the transmission timing of the second signal of the first signal) in the following manner. Absolute time in this document is represented by "Y milliseconds".

[0211] Timing for DL ​​data

[0212] DL assignment in sPDCCH-sPDSCH: same sTTI

[0213] sPDSCH-ACK / NACK feedback: at least X DL sTTI+Y ms later

[0214] Timing for UL data

[0215] UL grant in sPDCCH-sPUSCH: at least X DL sTTI+Y ms later

[0216] sPUSCH-ACK / NACK feedback: at least X DL sTTI+Y ms later

[0217] It is to be noted that the expression "at least X DL sTTI+Y ms later" means that there is an interval of at least (X-1) sTTI+Y ms from completion of transmission and reception of the first signal (DL assignment, sPDSCH, UL grant, or sPUSCH) until start of transmission and reception of the second signal (sPDSCH, ACK / NACK feedback, sPUSCH, or ACK / NACK feedback), and the second signal is assigned to the very first sTTI after the interval.

[0218] Hereinafter, the operation of data assignment, data transmission and reception, and feedback in the base station 100 and the terminal 200 will be described in detail.

[0219] Hereinafter, as in operation examples 1-1 and 2-1 of Embodiment 1, the UL sTTI length is set to seven symbols and the DL sTTI length is set to three / four symbols, and X is set to be equal to 4. In addition, the absolute time Y = 0.5 ms.

[0220] Figure 15 An exemplary transmission and reception timing of sPDCCH and sPUSCH to which the UL grant indicating the transmission of the UL data signal (sPUSCH) is mapped, and the transmission and reception timing of sPUSCH and the ACK / NACK signal for sPUSCH are illustrated.

[0221] As for the UL grant and sPUSCH, when X = 4, the base station 100 and the terminal 200 start transmission and reception of the sPUSCH after at least four DL sTTIs + 0.5 msec from transmission and reception of the UL grant (sPDCCH) based on the DL sTTI length and the absolute time Y. More specifically, there is an interval of at least three (= X - 1) DL sTTIs + 0.5 msec from completion of transmission and reception of the UL grant until start of transmission and reception of the sPUSCH. In other words, the base station 100 and the terminal 200 transmit the sPUSCH in the exactly first UL sTTI after the interval of three DL sTTIs + 0.5 msec.

[0222] Also, as for the sPUSCH and the ACK / NACK signal, when X = 4, the base station 100 and the terminal 200 start transmission and reception of the ACK / NACK signal for the sPUSCH after at least four DL sTTIs + 0.5 msec from transmission and reception of the sPUSCH based on the DL sTTI length and the absolute time Y. More specifically, there is an interval of at least three (= X - 1) DL sTTIs + 0.5 msec from completion of transmission and reception of the sPUSCH until start of transmission and reception of the ACK / NACK signal. In other words, the base station 100 and the terminal 200 transmit and receive the ACK / NACK signal in the exactly first DL sTTI after the interval of three DL sTTIs + 0.5 msec from transmission and reception timing of the sPUSCH.

[0223] Figure 16 FIG. illustrates exemplary transmission and reception timing of a DL assignment indicating transmission of a DL data signal (sPDSCH), and sPDCCH and sPDSCH to which the DL assignment is mapped, and transmission and reception timing of the sPDSCH and an ACK / NACK signal for the sPDSCH.

[0224] As for the DL assignment and sPDSCH, the base station 100 transmits the sPDSCH indicated by the DL assignment in the same DL sTTI as a DL sTTI in which the DL assignment is transmitted and received.

[0225] As for the sPDSCH and ACK / NACK signal, when X = 4, the base station 100 and the terminal 200 start transmission and reception of the ACK / NACK signal for the sPDSCH after at least four DL sTTIs + 0.5 msec from the transmission and reception of the sPDSCH based on the DL sTTI length and the absolute time Y. More specifically, there is an interval of at least three (= X - 1) DL sTTIs + 0.5 msec from the completion of the transmission and reception of the sPDSCH until the start of the transmission and reception of the ACK / NACK signal. In other words, the base station 100 and the terminal 200 transmit the ACK / NACK signal in the exactly first UL sTTI after the interval of three DL sTTIs + 0.5 msec from the transmission and reception timing of the sPDSCH.

[0226] Thus, the base station 100 and the terminal 200 can ensure the delay in processing or the time required for the upper layer communication in each device.

[0227] [Variation]

[0228] The base station 100 and the terminal 200 can define the timing of data allocation, data transmission and reception, and feedback (transmission timing of the second signal for the first signal) in the following manner.

[0229] Timing for DL data

[0230] DL allocation in sPDCCH-sPDSCH: Same sTTI

[0231] sPDSCH-ACK / NACK feedback: At least Max (X - 1 DL sTTIs, Y msec) interval

[0232] Timing for UL data

[0233] UL grant in sPDCCH-sPUSCH: At least Max (X - 1 DL sTTIs, Y msec) interval

[0234] sPUSCH-ACK / NACK feedback: At least Max (X - 1 DL sTTIs, Y msec) interval

[0235] Note that the expression "Max (X - 1 DL sTTIs, Y msec)" means that the larger one of X - 1 DL sTTIs and Y msec is selected.

[0236] In other words, the base station 100 and the terminal 200 transmit the second signal in the exactly first UL sTTI after the interval of the larger one of the predetermined number (X - 1) of DL sTTIs and the absolute time Y from the transmission and reception timing of the first signal.

[0237] With this configuration, when the sTTI length is longer than the absolute time Y, the delay in processing or the time required for upper layer communication in each device can be ensured only by the sTTI length, and the interval can be configured using only the sTTI length without configuring the absolute time Y, so that a configuration with an additional delay can be avoided. Meanwhile, when the sTTI length is shorter than the absolute time Y, the delay in processing or the time required for upper layer communication in each device can be sufficiently ensured.

[0238] (Embodiment 3)

[0239] The basic configuration of the base station and the terminal according to Embodiment 3 is common to the base station 100 and the terminal 200 according to Embodiment 1, and thus will be described with reference to Figure 4 and Figure 5 The base station and the terminal according to Embodiment 3 will be described.

[0240] In Embodiments 1 and 2, it is assumed that the base station 100 and the terminal 200 can use all sTTIs. However, due to the existence of an area used by a legacy terminal (a terminal that does not support sTTI), a PDCCH area for a common search space, or mapping of a reference signal such as a cell-specific reference signal (CRS), a demodulation reference signal (DMRS), a channel state information reference signal (CSI-RS), or a sounding reference signal (SRS), the resources available for transmitting and receiving data and control signals in the sTTI area are reduced. For this reason, it can be considered that data and control signals are transmitted and received without using sTTI, or adjacent sTTIs are combined to use sTTI as a single sTTI. Further, the number of sTTIs can be different between DL and UL because the amount of control signals and reference signals is different between DL and UL.

[0241] At this point, in this embodiment, a description will be given of a method of configuring the timing of data allocation, data transmission and reception, and feedback for the case where the available sTTI varies for each subframe.

[0242] The base station 100 and the terminal 200 use, as a DL reference subframe, a subframe in which all sTTIs are available, excluding adjacent subframes to be combined to be used as a single sTTI, and thus have the maximum number of sTTIs. The base station 100 and the terminal 200 determine the transmission and reception timing of data allocation (UL grant and DL allocation in sPDCCH), data (sPUSCH and sPDSCH), and feedback (ACK / NACK signal) based on the DL sTTI length in the DL reference subframe.

[0243] Further, as in Embodiment 1, when the boundary between the UL timing determined based on the DL sTTI length and the UL sTTI does not match, the base station 100 and the terminal 200 delay the UL timing to the timing that matches the boundary between the UL sTTI.

[0244] More specifically, as in Embodiment 1, the base station 100 and the terminal 200 can define the timing of data allocation, data transmission and reception, and feedback (transmission timing of the second signal for the first signal) in the following manner.

[0245] Timing for DL data

[0246] DL allocation in sPDCCH-sPDSCH: Same sTTI

[0247] sPDSCH-ACK / NACK feedback: After at least X DL sTTIs

[0248] Timing for UL data

[0249] UL grant in sPDCCH-sPUSCH: After at least X DL sTTIs

[0250] sPUSCH-ACK / NACK feedback: After at least X DL sTTIs

[0251] Note that the expression "at least X DL sTTIs" means that there is an interval of at least (X-1) sTTIs from the completion of transmission and reception of the first signal (DL allocation, sPDSCH, UL grant, or sPUSCH) until the start of transmission and reception of the second signal (sPDSCH, ACK / NACK feedback, sPUSCH, or ACK / NACK feedback), and the second signal is allocated in the exactly first sTTI after the interval.

[0252] In this embodiment, when a DL sTTI located before a predetermined interval from the timing of reception of an uplink signal (sPUSCH) (the timing defined above) is unavailable for signal allocation in a subframe having a smaller number of DL sTTIs available for signal allocation than the DL reference subframe, the base station 100 transmits a downlink signal (sPDCCH) in the last DL sTTI located before the DL sTTI unavailable for signal allocation. Also, when a DL sTTI located after a predetermined interval from the timing of the UL sTTI of reception of an uplink signal (sPUSCH) (the timing defined above) is unavailable for signal allocation in a subframe having a smaller number of DL sTTIs available for signal allocation than the reference subframe, the base station 100 transmits an ACK / NACK signal for the uplink signal in the first DL sTTI located after the DL sTTI unavailable for signal allocation.

[0253] Hereinafter, the operation of data allocation, data transmission and reception, and feedback in the base station 100 and the terminal 200 will be described in detail.

[0254] [Operation Example 3-1]

[0255] Figure 17 An exemplary transmission and reception timing of sPDCCH and sPUSCH to which a UL grant indicating the transmission of a UL data signal (sPUSCH) is mapped, and the transmission and reception timing of sPUSCH and an ACK / NACK signal for this sPUSCH are illustrated.

[0256] As shown in Figure 17 , as in Operation Example 1-2 in Embodiment 1 (see Figure 7 ), the UL sTTI length is set to three / four symbols, and the DL TTI length is set to two symbols, while X is set to equal to 4. Meanwhile, the base station 100 and the terminal 200 cannot use the sixth DL sTTI (DL sTTI #5, #12, #19, and #26) in all subframes.

[0257] Regarding the UL grant and sPUSCH, when X = 4, in the subframe (DL reference subframe) in Operation Example 1-2, the sPUSCH transmitted in UL sTTI #5 is allocated by the UL grant transmitted in the DL sTTI #5 located before the DL sTTI #5 by three DL sTTI intervals from the DL sTTI #9 which is the same timing as the UL sTTI #5. However, in Figure 17In this case, DL sTTI #5 is not available. Therefore, the base station 100 transmits the UL grant in DL sTTI #4 just before DL sTTI #5. Also, the base station 100 transmits the UL grant in DL sTTIs #11 and #18, which indicates the allocation for sPUSCH in UL sTTI #9 and UL sTTI #13 and plans to transmit in DL sTTIs #12 and #19.

[0258] As for the sPUSCH and the ACK / NACK signal, when X = 4, in the subframes (DL reference subframes) shown in Operation Example 1-2, the ACK / NACK signal for the sPUSCH in UL sTTI #4 is transmitted in DL sTTI #12 located at an interval of three DL sTTIs from DL sTTI #8 which is the same timing as UL sTTI #4. However, in Figure 17 In this case, DL sTTI #12 is not available. Therefore, the base station 100 delays the transmission timing of the ACK / NACK signal and transmits the signal in DL sTTI #13. Also, when X = 4, in Operation Example 1-2, the ACK / NACK signal for the sPUSCH in UL sTTIs #8 and #12 is transmitted in DL sTTIs #19 and #26 located at an interval of three DL sTTIs from DL sTTIs #15 and #22 which are the same timing as UL sTTIs #8 and #12, respectively. However, in Figure 17 In this case, DL sTTIs #19 and 26 are not available. Therefore, the base station 100 delays the transmission timing of the ACK / NACK signal and transmits the signal in DL sTTIs #20 and #27.

[0259] Meanwhile, in Figure 17 In this case, the number of DL sTTIs is greater than the number of UL sTTIs, so that there is no influence on the number of UL HARQ processes even when some DL sTTIs are not available. However, when there are many unavailable DL sTTIs or serial DL sTTIs are not available, the amount of delay increases, so that it is necessary to increase the number of UL HARQ processes.

[0260] [Operation Example 3-2]

[0261] In Operation Example 3-2, a description of the operation for the case where the UL and DL sTTI lengths are the same will be given.

[0262] Figure 18An example of the exemplary transmission and reception timing of the sPDCCH and sPUSCH to which the UL grant indicating the transmission of the UL data signal (sPUSCH) is mapped, and the transmission and reception timing of the sPUSCH and the ACK / NACK signal for the sPUSCH are illustrated.

[0263] As Figure 18 illustrated, the UL and DL sTTI lengths are each set to three / four symbols, and X is set to equal 4. In other words, one subframe is divided into four sTTIs. Meanwhile, the base station 100 and the terminal 200 cannot use the third DL sTTI (DL sTTI #2, #10, and #18) in the even-numbered subframes. In other words, the number of DL sTTIs available for signal allocation using sTTI is less in the even-numbered subframes than in the odd-numbered subframes (DL reference subframes).

[0264] In the case where all DL sTTIs are available, when X is equal to 4, the minimum number of UL HARQ process IDs is eight. However, since some DL sTTIs are not available in operation example 3-2, the delay in the UL allocation and ACK / NACK feedback increases, such that the minimum number of UL HARQ process IDs is nine.

[0265] Regarding the UL grant and sPUSCH, when X = 4 and all DL sTTIs are available, the sPUSCH transmitted in the UL sTTI #6 is allocated by the UL grant transmitted in the DL sTTI #2 located three DL sTTIs apart from the DL sTTI #6 as the same timing as the UL sTTI #6. However, in Figure 18 , the DL sTTI #2 is not available. Therefore, the base station 100 transmits the UL grant in the DL sTTI #1 just before the DL sTTI #2. Also, the base station 100 transmits the UL grant in the DL sTTI #9 and #17, which indicates the allocation for the sPUSCH in the UL sTTI #14 and #22 and is scheduled to be transmitted in the DL sTTI #10 and #18.

[0266] Regarding the sPUSCH and ACK / NACK signal, when X = 4 and all DL sTTIs are available, the ACK / NACK signal for the sPUSCH in the UL sTTI #6 is transmitted in the DL sTTI #10 located three DL sTTIs apart from the DL sTTI #6 as the same timing as the UL sTTI #6. However, in Figure 18In this case, the DL sTTI #10 is unavailable. Therefore, the base station 100 delays the transmission timing of the ACK / NACK signal and transmits the signal in the DL sTTI #11. Also, when X = 4 and all the DL sTTIs are available, the ACK / NACK signal for the sPUSCH in the UL sTTI #14 is transmitted in the DL sTTI #18 located at an interval of three DL sTTIs from the DL sTTI #14 which is the same timing as the UL sTTI #14. However, in this case, the DL sTTI #18 is unavailable. Therefore, the base station 100 delays the transmission timing of the ACK / NACK signal and transmits the signal in the DL sTTI #19. Figure 18 In this case, the DL sTTI #10 is unavailable. Therefore, the base station 100 delays the transmission timing of the ACK / NACK signal and transmits the signal in the DL sTTI #11. Also, when X = 4 and all the DL sTTIs are available, the ACK / NACK signal for the sPUSCH in the UL sTTI #14 is transmitted in the DL sTTI #18 located at an interval of three DL sTTIs from the DL sTTI #14 which is the same timing as the UL sTTI #14. However, in this case, the DL sTTI #18 is unavailable. Therefore, the base station 100 delays the transmission timing of the ACK / NACK signal and transmits the signal in the DL sTTI #19.

[0267] So far, operation examples 3-1 and 3-2 have been described.

[0268] As described above, in Embodiment 3, even when the DL subframe has a DL sTTI which cannot be allocated a signal, the base station 100 and the terminal 200 determine the timing of data allocation, data transmission and reception, and feedback based on the DL sTTI length as in Embodiment 1. Further, when the determined DL timing is a DL sTTI which cannot be allocated a signal, the base station 100 and the terminal 200 transmit a DL signal (a data signal or an ACK / NACK signal) at a timing before or after the determined DL timing.

[0269] Thus, even when the number of DL sTTIs is different between subframes, the base station 100 and the terminal 200 can start transmission and reception of a signal from the boundary between DL sTTIs and the boundary between UL sTTIs as in Embodiment 1. Therefore, according to Embodiment 3, the timing of data allocation, data transmission and reception, and feedback for the case of a shortened TTI length can be appropriately configured.

[0270] Note that, when the top DL sTTI in the DL subframe is unavailable, a PDCCH can be used as an alternative. The base station 100 transmits a control signal to be allocated in a sTTI and an ACK / NACK signal using the PDCCH, so there is no delay and there is an advantage of having no impact on the number of HARQ process IDs.

[0271] (Embodiment 4)

[0272] The basic configuration of the base station and the terminal according to Embodiment 4 is common to the base station 100 and the terminal 200 according to Embodiment 1, so reference will be made to Figure 4 and 5 the description of the base station and the terminal according to Embodiment 1.

[0273] There can be a case where the sTTI length returns to the normal TTI length during the operation using the sTTI length because of poor communication quality or because the latency reduction is no longer needed. At this point, in Embodiment 4, a description will be given of the operation of switching from the sTTI length to the normal TTI length (one subframe).

[0274] As a method of returning to the normal TTI, a method of using a common search space (CSS) allocated in the normal TTI length or a method of instructing a change to the normal TTI length by the MAC layer can be considered. In these cases, there are a method of keeping the HARQ process IDs used in the sTTI and a method of not keeping the HARQ process IDs used in the sTTI.

[0275] When the HARQ process IDs are not kept, the base station 100 and the terminal 200 delete the signals in the HARQ buffer and restart the communication as all new data.

[0276] Meanwhile, when the HARQ process IDs are kept, the base station 100 instructs the kept HARQ process IDs to the terminal 200 using the DL allocation with the normal TTI length.

[0277] Also, in the case of UL, the HARQ process IDs are not instructed to the terminal 200, so that the base station 100 and the terminal 200 need to share the structure of the UL HARQ process IDs in advance between the sTTI and the normal TTI. As the structure of sharing the HARQ process IDs, the terminal 200 associates the sTTI with the TTI based on the subframe of the switching of the reception TTI length.

[0278] Figure 19 An operation of switching between the sTTI and the TTI in subframe #1 is illustrated.

[0279] In Figure 19 In subframe #0, the sTTI is applied, and the terminal 200 detects UL grants of HARQ process IDs #0, #1, #2, and #3. Also, it is assumed that the terminal 200 detects an UL grant in the normal TTI in the PDCCH of subframe #1.

[0280] In this case, for the HARQ process IDs #0, #1, #2, and #3 as the sTTI operation, the terminal 200 performs a transmission process of sPUSCH in the UL of subframe #1 using the sTTI operation. In this case, the base station 100 can transmit ACK / NACK signals for the sPUSCH transmitted in the sTTI in subframe #2. Also, when NACK is transmitted in subframe #1, the terminal 200 can retransmit the sPUSCH (not shown) in subframe #3. As a result, it is possible to effectively utilize the resources used until the PUSCH transmission is switched to the normal TTI.

[0281] Note that the base station 100 can cancel the transmission of the ACK / NACK signal in subframe #2, and cause the terminal 200 to recognize all ACKs and allow the adaptive retransmission using only the normal TTI.

[0282] In the top DL sTTI of subframe #1, the UL HARQ process ID #4 is transmittable while maintaining the sTTI operation. At this point, the terminal 200 recognizes that the UL grant of the UL HARQ process ID #4 is transmitted in the PDCCH of subframe #1, and transmits the PUSCH of the HARQ process ID #4 in subframe #5 located four subframes (the interval of three DL subframes) after subframe #1 according to the rule of LTE / LTE-Advanced based on subframe #1. Further, the terminal 200 recognizes that the UL grant of the HARQ process ID #5 is transmitted in the PDCCH of the next subframe #2.

[0283] As described above, the base station 100 and the terminal 200 use the sTTI for the HARQ process IDs #0 to #3, and switch the sTTI to the TTI for the UL HARQ process ID #4 and thereafter. More specifically, the base station 100 and the terminal 200 use the common HARQ process ID between the period when the sTTI (DL sTTI and UL sTTI) is used and the period when the TTI is used.

[0284] As a result, the base station 100 and the terminal 200 can maintain the retransmission processing of the UL data signal even when the switching from the sTTI to the normal TTI is performed. Also, the base station 100 and the terminal 200 can reduce the amount of the buffer because the base station 100 and the terminal 200 do not need to have the copy of the HARQ buffer for the sTTI and the TTI.

[0285] So far, each embodiment of the present disclosure has been described.

[0286] Note that the HARQ timing based on FDD has been described in the above-described embodiments, but the present disclosure can be applied to the HARQ timing based on TDD. When the present disclosure is applied to the HARQ timing based on TDD, the binding between subframes can also be applied.

[0287] Further, the case where the transmission and reception timing of the signal is determined based on the DL sTTI length has been described in the above-described embodiments, but the transmission and reception timing of the signal can be determined based on the UL sTTI length.

[0288] Also, the case where X is equal to 4 has been described in the above-described embodiments, but the value of X can be a value other than 4.

[0289] Further, in the above-described embodiments, the UL transmission timing is also adjusted by a timing advance (TA). Thus, in addition to the timing defined in the above-described embodiments, the actual UL transmission timing can be determined to start transmission by TA that is advanced by a predetermined amount.

[0290] In Embodiment 1, the application restriction is made so that the UL grant is transmitted only in a specific DL sTTI, but other embodiments are by no means limited to this restriction. The transmission of the UL grant can be performed in any DL sTTI as long as the DL sTTI is located at least sTTI X DL sTTIs away from the UL in which the PUSCH can be transmitted, and the UL grant for a single UL sTTI can be transmitted from a plurality of DL sTTIs. In this case, the number of DL sTTIs to be monitored by the terminal 200 for the UL grant increases, but there is an advantage in that the control signal can be easily dispersed.

[0291] Further, the shortening of the TTI length is not only applied to a system in which LTE is extended, but also applied to a system implemented with a new frame format called "New Radio Access Technology (RAT)".

[0292] The above-described embodiments have been described with an example in which an aspect of the present disclosure is implemented by using hardware configurations by way of example, but the present disclosure can also be implemented by software in cooperation with hardware.

[0293] Further, the functional blocks used in the description of the embodiments are generally implemented as LSI devices, which are integrated circuits having inputs and outputs. The integrated circuits can control the functional blocks used in the description of the embodiments and can include inputs and outputs. The functional blocks can be formed as separate chips, or a part or all of the functional blocks can be integrated into a single chip. The term "LSI" is used herein, but depending on the level of integration, the term "IC", "system LSI", "super LSI", or "ultra LSI" can also be used.

[0294] Further, the circuit integration is not limited to the LSI, and can be realized by a dedicated circuit system or a general-purpose processor. After the LSI is manufactured, a field programmable gate array (FPGA) that can be programmed, or a reconfigurable processor where the connection and the setting of circuit cells in the LSI can be reconfigured can be used.

[0295] If a circuit integration technology replacing LSIs emerges as a result of the progress of semiconductor technology or other technologies derived from the technology, the functional blocks can be integrated using such technology. Another possibility is the application of biotechnology, etc.

[0296] The base station of the present disclosure includes a transmission section that transmits a downlink signal using a first short transmission time interval (sTTI) that is shorter in length than a TTI and is used for a downlink, and a reception section that receives an uplink signal using a second sTTI that is shorter in length than the TTI and is used for an uplink, the reception section receiving the uplink signal in the second sTTI located after a predetermined interval from a transmission timing of the downlink signal when the length of the first sTTI is shorter than that of the second sTTI, the predetermined interval being configured based on the length of the first sTTI.

[0297] In the base station of the present disclosure, the reception section receives the uplink signal in the very first second sTTI located after an interval of a predetermined number of first sTTIs from a transmission timing of the downlink signal.

[0298] In the base station of the present disclosure, the reception section delays a reception timing of the uplink signal when a timing after an interval of a predetermined number of first sTTIs from a transmission timing of the downlink signal does not match a boundary between the second TTIs.

[0299] In the base station of the present disclosure, the downlink signal contains downlink allocation control information indicating an allocation for a downlink data signal, and the reception section receives an ACK / NACK signal for the downlink data signal in a second sTTI located after a predetermined interval from a timing of a first sTTI in which the downlink data signal is transmitted.

[0300] In the base station of the present disclosure, the downlink signal contains uplink allocation control information indicating an allocation for an uplink signal, and the transmission section transmits an ACK / NACK signal for the uplink signal in a first sTTI located after a predetermined interval from a timing of a second sTTI in which the uplink signal is received.

[0301] In the base station of the present disclosure, a first sTTI in which the uplink allocation control information is transmitted and a first sTTI in which the ACK / NACK signal is transmitted are different from each other.

[0302] In the base station of the present disclosure, the transmission section transmits the ACK / NACK signal in a first sTTI immediately before a first sTTI in which uplink allocation control information having the same HARQ process ID as that of the ACK / NACK signal is transmitted.

[0303] In the base station of the present disclosure, the reception section receives an ACK / NACK signal for each of a plurality of downlink signals transmitted in a single subframe in a plurality of second sTTIs within the single subframe.

[0304] In the base station of the present disclosure, the receiving section receives the uplink signal in the just first second sTTI located after a larger one of a predetermined number of intervals of the first sTTI and an absolute time from a transmission timing of the downlink signal.

[0305] In the base station of the present disclosure, the receiving section receives the uplink signal in the just first second sTTI located after a larger one of a predetermined number of intervals of the first sTTI and an absolute time from a transmission timing of the downlink signal.

[0306] In the base station of the present disclosure, the transmitting section configures a predetermined interval based on a length of the first sTTI forming a reference subframe, and when a first sTTI located a predetermined interval before a timing of receiving the uplink signal is unavailable for signal allocation in a subframe having a smaller number of the first sTTIs available for signal allocation than the reference subframe, the transmitting section transmits the downlink signal in a last first sTTI located before the first sTTI unavailable for signal allocation.

[0307] In the base station of the present disclosure, the downlink signal contains uplink allocation control information indicating an allocation for the uplink signal, the transmitting section configures a predetermined interval based on a length of the first sTTI forming a reference subframe, and when a first sTTI located a predetermined interval after a timing of receiving the second sTTI of the uplink signal is unavailable for signal allocation in a subframe having a smaller number of the first sTTIs available for signal allocation than the reference subframe, the transmitting section transmits an ACK / NACK signal for the uplink signal in the just first first sTTI located after the first sTTI unavailable for signal allocation.

[0308] In the base station of the present disclosure, when use of the first sTTI and the second sTTI is switched to use of TTIs, the transmitting section and the receiving section use a common HARQ process ID.

[0309] The terminal of the present disclosure includes a receiving section that receives a downlink signal using a first short transmission time interval (sTTI) shortened in length from a TTI and used for a downlink, and a transmitting section that transmits an uplink signal using a second sTTI shortened in length from the TTI and used for an uplink, and when a length of the first sTTI is shorter than the second sTTI, the transmitting section transmits the uplink signal in the second sTTI located a predetermined interval after a timing of receiving the downlink signal, the predetermined interval being configured based on the length of the first sTTI.

[0310] The communication method of the present disclosure includes transmitting a downlink signal using a first short transmission time interval (sTTI) that is shorter in length than a TTI and used for a downlink, and receiving an uplink signal using a second sTTI that is shorter in length than a TTI and used for an uplink, when the length of the first sTTI is shorter than that of the second sTTI, the uplink signal is received in the second sTTI located after a predetermined interval from the transmission timing of the downlink signal, the predetermined interval being configured based on the length of the first sTTI.

[0311] The communication method of the present disclosure includes receiving a downlink signal using a first short transmission time interval (sTTI) that is shorter in length than a TTI and used for a downlink, and transmitting an uplink signal using a second sTTI that is shorter in length than a TTI and used for an uplink, when the length of the first sTTI is shorter than that of the second sTTI, the uplink signal is transmitted in the second sTTI located after a predetermined interval from the reception timing of the downlink signal, the predetermined interval being configured based on the length of the first sTTI.

[0312] Industrial applicability

[0313] An aspect of the present disclosure is useful in a mobile communication system.

[0314] List of reference numerals

[0315] 100 base station

[0316] 101 sTTI determining section

[0317] 102 sPDCCH generating section

[0318] 103, 209 error correction encoding section

[0319] 104, 210 modulation section

[0320] 105, 211 signal allocating section

[0321] 106, 212 transmitting section

[0322] 107, 201 receiving section

[0323] 108, 202 signal demultiplexing section

[0324] 109 ACK / NACK receiving section

[0325] 110, 203 demodulation section

[0326] 111, 204 error correction decoding section

[0327] 112 ACK / NACK determining section

[0328] 200 terminal

[0329] 205 sTTI configuration section

[0330] 206 error determination section

[0331] 207 ACK / NACK generation section

[0332] 208 sPDCCH reception section

Claims

1. A base station comprising: a transmitter that transmits a downlink signal to a terminal in a first short transmission time interval (sTTI) shorter than a subframe; and a receiver that receives an uplink signal transmitted from the terminal in a second sTTI shorter than the subframe and longer than the first sTTI, wherein the receiver receives the uplink signal transmitted in the second sTTI after a larger one of a determined number of first sTTIs from a transmission timing of the downlink signal and an absolute time, and the determined number is applied to all first sTTIs of the subframe, and wherein the absolute time refers to a fixed time length of a delay in processing or a time required for communication with an upper layer.

2. The base station of claim 1, wherein, The downlink signal contains downlink control information indicating allocation of downlink data, and the uplink signal is an ACK / NACK signal for the downlink data.

3. The base station of claim 1, wherein, The downlink signal contains downlink control information indicating allocation of the uplink signal, and the transmitter transmits an ACK / NACK signal for the uplink signal in a first sTTI after a determined number of first sTTIs from a second sTTI in which the uplink signal is received.

4. The base station of claim 3, wherein, The transmitter transmits the ACK / NACK signal in a first sTTI just before a first sTTI in which downlink control information with a same HARQ process ID as that of the ACK / NACK signal is transmitted.

5. The base station of claim 1, wherein, The transmitter and the receiver use a common HARQ process ID or maintain a HARQ process ID when switching between TTIs and sTTIs as subframes.

6. The base station of claim 1, wherein, The determined number is configured as a variable parameter between the base station and the terminal. 7.A terminal comprising: a receiver that receives a downlink signal transmitted from a base station in a first short transmission time interval (sTTI) shorter than a subframe; and a transmitter that transmits an uplink signal to the base station in a second sTTI shorter than the subframe and longer than the first sTTI, wherein the transmitter transmits the uplink signal in the second sTTI after a larger one of a determined number of first sTTIs from a reception timing of the downlink signal and an absolute time, and the determined number is applied to all first sTTIs of the subframe, and wherein the absolute time refers to a fixed time length of a delay in processing or a time required for communication with an upper layer.

8. The terminal according to claim 7, wherein The downlink signal contains downlink control information indicating allocation of downlink data, and the uplink signal is an ACK / NACK signal for the downlink data.

9. The terminal according to claim 7, wherein The downlink signal contains downlink control information indicating allocation of the uplink signal, and the receiver receives an ACK / NACK signal for the uplink signal transmitted from the base station in a first sTTI after a determined number of first sTTIs from a second sTTI in which the uplink signal is transmitted.

10. The terminal according to claim 9, wherein The receiver receives the ACK / NACK signal in a first sTTI immediately before a first sTTI in which downlink control information of a same HARQ process ID as the ACK / NACK signal is transmitted.

11. The terminal of claim 7, wherein, The transmitter and the receiver use a common HARQ process ID or maintain a HARQ process ID when switching between a TTI and an sTTI as a subframe.

12. The terminal of claim 7, wherein, The determined number is configured as a variable parameter between the base station and the terminal.

13. A communication method comprising: transmitting a downlink signal to a terminal in a first short transmission time interval (sTTI) shorter than a subframe; and receiving an uplink signal transmitted from the terminal in a second sTTI shorter than the subframe and longer than the first sTTI, wherein the receiving includes receiving the uplink signal transmitted in a second sTTI after a larger one of a determined number of first sTTIs and an absolute time from a transmission timing of the downlink signal, and the determined number is applied to all first sTTIs of the subframe, and wherein the absolute time refers to a fixed length of time of a delay in processing or a time required for communication with an upper layer.

14. A communication method comprising: receiving a downlink signal transmitted from a base station in a first short transmission time interval (sTTI) shorter than a subframe; and transmitting an uplink signal to the base station in a second sTTI shorter than the subframe and longer than the first sTTI, wherein the transmitting includes transmitting the uplink signal in a second sTTI after a larger one of a determined number of first sTTIs and an absolute time from a reception timing of the downlink signal, and the determined number is applied to all first sTTIs of the subframe, and wherein the absolute time refers to a fixed length of time of a delay in processing or a time required for communication with an upper layer.

15. An integrated circuit that controls a method comprising: transmitting a downlink signal to a terminal in a first short transmission time interval (sTTI) shorter than a subframe; and receiving an uplink signal transmitted from the terminal in a second sTTI shorter than the subframe and longer than the first sTTI, wherein the receiving includes receiving the uplink signal transmitted in a second sTTI after a larger one of a determined number of first sTTIs and an absolute time from a transmission timing of the downlink signal, and the determined number is applied to all first sTTIs of the subframe, and wherein the absolute time refers to a fixed length of time of a delay in processing or a time required for communication with an upper layer.

16. An integrated circuit that controls a method comprising: receiving a downlink signal transmitted from a base station in a first short transmission time interval (sTTI) shorter than a subframe; and transmitting an uplink signal to the base station in a second sTTI shorter than the subframe and longer than the first sTTI, wherein the transmitting includes transmitting the uplink signal in a second sTTI after a larger one of a determined number of first sTTIs and an absolute time from a reception timing of the downlink signal, and the determined number is applied to all first sTTIs of the subframe, and wherein the absolute time refers to a fixed length of time of a delay in processing or a time required for communication with an upper layer. The sending includes: sending the uplink signal in a second sTTI after a larger one of a determined number of first sTTIs and an absolute time from a receiving timing of the downlink signal, and the determined number is applied to all first sTTIs of the subframe, and The absolute time refers to a fixed time length of a delay in processing or a time required for communication with an upper layer.

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