JP7325581B2 - Terminal, communication method and integrated circuit - Google Patents

Description

The present disclosure relates to terminals, communication methods and integrated circuits.

In recent years, realization of applications that require a reduction in delay time (delay critical) has been considered. Examples of applications that require reduced latency include autonomous driving, hyper-reality applications in smart glasses, and communication between devices.

In order to realize these applications, 3GPP is studying latency reduction to reduce packet delays (see Non-Patent Document 1). In latency reduction, it is considered to shorten the TTI (Transmission Time Interval) length, which is the time unit for transmitting and receiving data, to a length between 0.5 msec and 1 OFDM symbol. Note that the conventional TTI length is 1 msec, which is equivalent to a unit called a subframe. 1 subframe is composed of 2 slots (1 slot is 0.5 msec). One slot consists of 7 OFDM (Orthogonal Frequency Division Multiplexing) symbols in the case of normal CP (Cyclic Prefix), and consists of 6 OFDM symbols in the case of extended CP.

FIG. 1 shows an example of shortened TTI for normal CP. If the TTI length is 0.5 msec (=1 slot), 2 TTIs are allocated per 1 msec. Also, when one slot is divided into a TTI of 4 OFDM symbols and a TTI of 3 OFDM symbols, 4 TTIs are allocated per 1 msec. Also, if the TTI length is 1 OFDM symbol, 14 TTIs are allocated per 1 msec.

By shortening the TTI length, the delay in CQI reporting can be shortened and the frequency of CQI reporting can be increased, so there is an advantage that the gap between the CQI report and the actual channel quality is reduced.

RP-150465, "New SI proposal: Study on Latency reduction techniques for LTE," Ericsson, Huawei, March 2015 3GPP TR 36.211 V13.0.0, “Physical channels and modulation (Release 13),” December 2015

When shortening the TTI length, the base station (sometimes called eNB) to the terminal (UE (User Equipment)) to notify resource allocation and MCS (Modulation and coding scheme) may transmit DCI (Downlink Control Information) for each shortened TTI.

However, as shown in FIG. 2, when the base station transmits a DCI (enhanced physical downlink control channel (EPDCCH) in FIG. 2) of the same amount of information as the DCI of the conventional TTI with a TTI length of 1 msec for each TTI, The control signal needs to be several times TTI per 1msec compared to the conventional one. Therefore, there is a problem that the ratio of control signals to resources increases and system throughput decreases.

One aspect of the present disclosure is to provide a base station, a terminal, and a communication method that can efficiently use resources even when the TTI length is shortened.

A terminal according to an aspect of the present disclosure is a time unit for transmitting and receiving data shorter than one subframe, and a receiving unit that receives downlink control information (DCI) for resource allocation in a plurality of the time units. , and a transmitter that transmits uplink data based on the DCI, wherein the DCI includes first information for each of the plurality of time units and second information for all of the plurality of time units. and wherein the second information includes frequency resource allocation and MCS.

A communication method according to an aspect of the present disclosure is a time unit for transmitting and receiving data that is shorter than one subframe, and a step of receiving downlink control information (DCI) for resource allocation in a plurality of the time units. and transmitting uplink data based on the DCI, wherein the DCI includes first information for each of the plurality of time units and second information for all of the plurality of time units. , the second information includes frequency resource allocation and MCS.

An integrated circuit according to one aspect of the present disclosure is a time unit for transmitting and receiving data shorter than one subframe, and a process of receiving downlink control information (DCI) for resource allocation in a plurality of the time units. , a process of transmitting uplink data based on the DCI, wherein the DCI includes first information for each of the plurality of time units and second information for all of the plurality of time units. , the second information includes frequency resource allocation and MCS.

In addition, these generic or specific aspects may be realized by systems, devices, methods, integrated circuits, computer programs, or recording media. may be realized by any combination of

According to one aspect of the present disclosure, resources can be used efficiently even when the TTI length is shortened.

Further advantages and advantages of one aspect of the present disclosure are apparent from the specification and drawings. Such advantages and/or advantages are provided by the several embodiments and features described in the specification and drawings, respectively, not necessarily all provided to obtain one or more of the same features. no.

Diagram showing an example of TTI length FIG. 4 is a diagram for explaining a problem to be solved by one aspect of the present disclosure; FIG. 3 is a block diagram showing the main configuration of the base station according to Embodiment 1; Block diagram showing the main configuration of the terminal according to Embodiment 1 FIG. 1 is a block diagram showing the configuration of a base station according to Embodiment 1; Block diagram showing the configuration of a terminal according to Embodiment 1 A diagram showing an example of DL control information included in DCI according to Embodiment 1 Diagram showing an example of DL allocation according to Embodiment 1 A diagram showing an example of UL control information included in DCI according to Embodiment 1 A diagram showing an example of UL allocation in subframe N when non-adaptive retransmission and adaptive retransmission are supported according to Embodiment 1 A diagram showing an example of UL subframe N+X allocation when supporting non-adaptive retransmission and adaptive retransmission according to Embodiment 1 A diagram showing an example of UL allocation in subframe N when adaptive retransmission is supported according to Embodiment 1 FIG. 10 is a diagram showing an example of allocation in UL subframe N+X when adaptive retransmission is supported according to Embodiment 1; Diagram showing the concept of PUCCH resources Diagram showing the concept of PUCCH resources when SRS is deployed Diagram showing PUCCH resources for transmitting ACK/NACK signals in the case of 4 TTIs per subframe according to Embodiment 2 Diagram showing an example of DL allocation according to Embodiment 2 FIG. 10 is a diagram showing an example of UL ACK/NACK signal allocation according to the second embodiment; Diagram showing PUCCH resources for transmitting ACK/NACK signals in the case of 14 TTIs per subframe according to Embodiment 2 Diagram showing an example of spatial bundling Diagram showing an example of time domain bundling FIG. 11 is a diagram showing an example of generation of ACK/NACK signals according to operation example 1 of the second embodiment; FIG. 11 is a diagram showing an example of generation of ACK/NACK signals according to operation example 2 of the second embodiment;

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

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

FIG. 3 is a block diagram showing a main configuration of base station 100 according to the embodiment of the present disclosure. In base station 100 shown in FIG. 3 , PDCCH generating section 103 generates one Downlink Control Information (DCI) containing control information for a plurality of first TTIs with TTI lengths shorter than that of second TTIs (Transmission Time Intervals). and the transmission unit 107 transmits the DCI.

Also, FIG. 4 is a block diagram showing a main configuration of terminal 200 according to each embodiment of the present disclosure. In terminal 200 shown in FIG. 4, PDCCH receiving section 207 receives one Downlink Control Information (DCI) containing control information for a plurality of first TTIs with TTI lengths shorter than the second TTI (Transmission Time Interval). Upon reception, signal separation section 202 uses DCI to separate the downlink data signal from the received signal, and signal allocation section 210 uses DCI to allocate the uplink data signal to uplink resources.

In DCI, control information related to data signal retransmission processing is set for each of a plurality of first TTIs, and control information related to processing other than retransmission processing is set commonly to a plurality of first TTIs.

(Embodiment 1)
[Base station configuration]
FIG. 5 is a block diagram showing the configuration of base station 100 according to this embodiment. In FIG. 5, base station 100 includes TTI determining section 101, MCS determining section 102, PDCCH (Physical Downlink Control Channel) generating section 103, error correction coding section 104, modulating section 105, and signal allocation section 106. , transmitting section 107, receiving section 108, signal separating section 109, PUCCH (Physical Uplink Control Channel) receiving section 110, demodulating section 111, error correction decoding section 112, and ACK/NACK determining section 113. have.

When allocating resources for a plurality of TTIs using one DCI, TTI determination section 101 determines to which TTI to allocate resources among the plurality of TTIs. TTI determining section 101 outputs information (TTI information) indicating the presence or absence of allocation to each of a plurality of TTIs to PDCCH generating section 103 .

Specifically, in the case of DL (downlink) allocation, TTI determining section 101 receives an ACK/NACK signal that is mapped to PUCCH and is transmitted as input from PUCCH receiving section 110, or an ACK/NACK signal that is transmitted as input from error correction decoding section 112. Based on the ACK/NACK signal that is multiplexed with the UL (uplink) data signal and transmitted, the TTI that requires retransmission is determined, and the TTI for resource allocation is determined based on the determination result. In addition, TTI determination section 101 determines the allocation of new data for each TTI in consideration of the amount of data input from the buffer of the DL data signal (not shown) and allocation to other UEs, and allocates resources. Determine the TTI to allocate.

On the other hand, in the case of UL allocation, TTI determination section 101 determines the TTI that requires retransmission based on the ACK/NACK signal for UL data input from ACK/NACK determination section 113, and based on the determination result. Determine the TTI for allocating resources. In addition, the TTI determination unit 101 considers the data amount obtained from the buffer status report of the UL data signal transmitted from the UE (not shown) and the allocation to other UEs, and new data allocation is performed for each TTI. Decide and determine the TTI to allocate resources.

MCS determining section 102 determines the DL MCS based on the CQI information and the ACK/NACK signal for the DL data signal input from PUCCH receiving section 110 . Also, MCS determining section 102 determines the UL MCS based on the received quality of the SRS (Sounding Reference Signal) or UL data signal sent separately. MCS determining section 102 outputs information (MCS information) indicating the determined MCS of DL and UL to PDCCH generating section 103 . Also, MCS determining section 102 outputs the DL MCS to error correction coding section 104 and modulating section 105 , and outputs the UL MCS to demodulating section 111 and error formulation decoding section 112 .

PDCCH generation section 103 generates PDCCH or EPDCCH to which multiple TTIs are allocated. The PDCCH is arranged in the first OFDM symbol (number of symbols: 1, 2 or 3) in the subframe, and the EPDCCH is arranged in the OFDM symbols other than the OFDM symbols in the subframe in which the PDCCH is arranged.

Specifically, based on the TTI information input from TTI determination section 101, PDCCH generation section 103 sets NDI (New Data Indicator) for TTIs to which DL and UL are to be allocated. Also, in the case of DL allocation, PDCCH generating section 103 further sets a HARQ number (HARQ process number) and a redundancy version for the TTI. PDCCH generation section 103 also generates DL and UL resource allocation information as information common to a plurality of TTIs. Then, PDCCH generation section 103 generates one DCI including control information regarding allocation to these TTIs and TTI information. PDCCH generation section 103 generates PDCCH or EPDCCH using the MCS information input from MCS determination section 102 and outputs the generated PDCCH or EPDCCH to signal allocation section 106 and signal separation section 109 .

Error correction coding section 104 performs error correction coding on a transmission data signal (DL data signal) or higher layer signaling based on the DL MCS information input from MCS determination section 102, and converts the coded signal to a modulation section. 105.

Modulation section 105 performs modulation processing on the signal received from error correction coding section 104 based on the DL MCS information input from MCS determination section 102, and outputs the modulated data signal to signal allocation section 106. do.

Signal allocation section 106 allocates signals (including data signals) received from modulation section 104 and control signals (PDCCH or EPDCCH) received from PDCCH generation section 103 to predetermined downlink resources. A transmission signal is formed by allocating a control signal (PDCCH or EPDCCH) and a data signal (PDSCH) to predetermined resources in this way. The formed transmission signal is output to transmission section 107 .

Transmitting section 107 performs radio transmission processing such as up-conversion on the transmission signal input from signal allocation section 106, and transmits the result to terminal 200 via an antenna.

Receiving section 108 receives a signal transmitted from terminal 200 via an antenna, performs radio reception processing such as down-conversion on the received signal, and outputs the result to signal separating section 109 .

Based on the information input from PDCCH generation section 103, signal separation section 109 separates the UL data signal from the received signal and outputs it to demodulation section 111, and extracts the signal included in the PUCCH resource (PUCCH signal, ACK) from the received signal. /NACK signal) and output to PUCCH receiving section 110 .

PUCCH receiving section 110 extracts an ACK/NACK signal for the DL data signal from the PUCCH signal input from signal separating section 109 and outputs the ACK/NACK signal to TTI determining section 101 and MCS determining section 102 . PUCCH receiving section 110 also extracts CQI information from the PUCCH signal input from signal separating section 109 and outputs the information to MCS determining section 102 .

Demodulation section 111 performs demodulation processing on the signal input from signal separation section 109 based on UL MCS information (modulation information) input from MCS determination section 102, and performs error correction decoding on the obtained signal. Output to unit 112 .

Error correction decoding section 112 decodes the signal input from demodulation section 111 based on the UL MCS information (error code information) input from MCS determination section 102, and converts the received data signal from terminal 200 (UL data signal). Error correction decoding section 112 outputs the UL data signal to ACK/NACK determination section 113 . Also, error correction decoding section 112 extracts an ACK/NACK signal for the DL data signal, which is multiplexed with the UL data signal and transmitted, and outputs it to TTI determination section 101 .

ACK/NACK determination section 113 uses a CRC (Cyclic Redundancy Check) to determine whether or not there is an error in the UL data signal input from error correction encoding section 112, and uses the determination result as UL. It is output to TTI decision section 101 as an ACK/NACK signal.

[Device configuration]
FIG. 6 is a block diagram showing the configuration of terminal 200 according to this embodiment. 6, terminal 200 includes receiving section 201, signal separation section 202, demodulation section 203, error correction decoding section 204, error determination section 205, ACK/NACK generation section 206, and PDCCH reception section 207. , an error correction coding unit 208 , a modulation unit 209 , a signal allocation unit 210 and a transmission unit 211 .

Receiving section 201 receives a received signal via an antenna, performs reception processing such as down-conversion on the received signal, and outputs the received signal to signal separating section 202 .

Signal separating section 202 separates signals (PDCCH signals or EPDCCH signals) mapped to resources to which PDCCH or EPDCCH may be allocated, and outputs the signals to PDCCH receiving section 207 . Also, based on the DL resource allocation information input from PDCCH receiving section 207 , signal separating section 202 separates the DL data signal from the received signal and outputs the DL data signal to demodulating section 203 . In addition, when resources for multiple TTIs are allocated in PDCCH or EPDCCH, signal separation section 202 outputs DL data signals allocated to the same resource in multiple TTIs to which resources are allocated to demodulation section 203. do.

Demodulation section 203 demodulates the signal received from DL MCS information (modulation information) signal separation section 202 input from PDCCH reception section 207 and outputs the demodulated signal to error correction decoding section 204 .

Error correction decoding section 204 decodes the demodulated signal received from demodulation section 203 based on the DL MCS information (error code information), NDI, HARQ number, and Redundancy version input from PDCCH receiving section 207, and obtains Outputs the received data signal. The received data signal is also output to error determination section 205 .

Error determination section 205 detects an error in the CRC of the received data signal and outputs the detection result to ACK/NACK generation section 206 .

ACK/NACK generation section 206 generates an ACK if there is no error based on the detection result of the received data signal input from error determination section 205, generates a NACK if there is an error, and generates the generated ACK/NACK. A NACK signal is output to signal allocation section 210 .

PDCCH receiving section 207 receives the PDCCH signal or EPDCCH signal (that is, DCI) received from signal separating section 202, and when multiple TTIs are allocated in the DCI, extracts NDI for each TTI. Also, the PDCCH receiving section 207 extracts the HARQ number and redundancy version information for each TTI to which the DL data resource is allocated. In addition, PDCCH receiving section 207 extracts resource allocation information (DL resource allocation information, UL resource allocation information) and MCS information as information common to multiple TTIs, and extracts DL resource allocation information from signal separation section 202. , outputs UL resource allocation information to signal allocation section 210, outputs modulation information among MCS information to demodulation section 203 and modulation section 209, and outputs error correction information among MCS information and NDI to error correction coding Output to section 204 and error correction decoding section 208 . PDCCH receiving section 207 also outputs the HARQ number and redundancy version of the DL data to error correcting coding section 208 .

Based on the NDI input from PDCCH receiving section 207, error correction coding section 208 determines whether the transmission data signal (UL data signal) is newly allocated or retransmitted. Further, error correction coding section 208 performs error correction coding on the UL data signal based on MCS information (error code information) input from PDCCH receiving section 207, and outputs the coded data signal to modulation section 209. do.

Modulating section 209 modulates the data signal received from error correction coding section 208 based on the MCS information (modulation information) input from PDCCH receiving section 207, and outputs the modulated data signal to signal allocation section 210. .

Signal allocation section 210 allocates the data signal input from modulation section 209 to resources based on the UL resource allocation information received from PDCCH reception section 207 , and outputs the resource to transmission section 212 . Further, signal allocation section 210 allocates the ACK/NACK signal input from ACK/NACK generation section 206 to a PUCCH resource, or multiplexes it with the UL data signal and outputs it to transmission section 211 .

Transmitting section 211 performs transmission processing such as up-conversion on the signal input from signal allocation section 210 and transmits the result via an antenna.

[Operation of base station 100 and terminal 200]
Operations in base station 100 and terminal 200 having the above configurations will be described in detail.

With the present embodiment, when performing latency reduction, base station 100 allocates resources for a plurality of TTIs using one DCI. At this time, base station 100 notifies terminal 200 of one DCI including a bit string (resource allocation) indicating the presence or absence of allocation for each of a plurality of TTIs.

Here, if the frequency of CQI reporting increases and the delay from CQI measurement to reporting is shortened by shortening the TTI length by latency reduction, the base station predicts quality close to the actual channel quality. , resource allocation and MCS configuration. However, if the frequency of CQI reporting is limited to a predetermined period such as every 10 TTIs or every 5 TTIs, the base station uses the same CQI report to improve channel quality until the CQI is updated. Resource allocation and MCS setting will be performed in anticipation. Therefore, under the above-mentioned restrictions, even if the same frequency resource and MCS are used for a plurality of TTIs during the period in which the CQI is not updated, the impact on throughput reduction is expected to be small.

In addition, it can be expected that the trackability of the outer loop control will improve when the number of ACK/NACK signal transmissions/receptions increases due to the shortening of the TTI length. Outer-loop control is control in which a base station selects an MCS so as to achieve a target error rate according to a packet decoding decision result (ACK/NACK signal) reported by a UE. Therefore, shortening the TTI length and increasing the number of ACK/NACK signals per resource assigned to each of a plurality of TTIs is considered effective in improving throughput.

Considering the above two points, shortening the TTI length is effective in improving throughput by shortening the delay of CQI reporting and increasing the number of ACK/NACK signals, but changing the resource allocation and MCS setting for each TTI. It is considered unnecessary.

Therefore, in the present embodiment, base station 100 sets control information regarding ACK/NACK signal transmission/reception processing, that is, retransmission processing (HARQ processing), for each of a plurality of TTIs in one DCI. On the other hand, in one DCI, base station 100 configures control information other than control information related to retransmission processing (for example, frequency resources (PRB (Physical Resource Block)), MCS, etc.) in common for a plurality of TTIs.

By doing this, even when base station 100 allocates resources to a plurality of TTIs in latency reduction, it is possible to suppress an increase in control information included in one DCI, and reduce the DCI overhead amount. In addition, by notifying control information for a plurality of TTIs with one DCI, the number of DCI detections at terminal 200 is reduced, so that the probability of DCI detection errors can be reduced.

Operation examples 1 and 2 according to the present embodiment will be described below.

[Example 1: DL]
In this operation example, base station 100 (PDCCH generation section 103) uses DCI for each TTI in order to notify resource allocation for a plurality of TTIs within 1 subframe of DL as control information to be notified by one DCI. TTI information (Resource allocation) is newly added to indicate whether allocation is performed by

For example, as TTI information, base station 100 adds bit strings for the number of TTIs that can be assigned simultaneously to one DCI. Each bit in the bit string corresponds to each TTI that can be assigned to one DCI simultaneously. For example, a 1 in a bit string indicates that the corresponding TTI has an allocation, and a 0 indicates that the corresponding TTI does not have an allocation. Terminal 200 identifies the presence or absence of allocation for each TTI based on the TTI information included in one DCI.

Further, the base station 100 makes common information that can be shared among a plurality of TTIs among the control information included in the conventional DCI, and individually sets information that needs to be notified individually for each TTI. Base station 100 transmits all of this information in one DCI.

For example, in LTE/LTE-Advanced, the DCI format used differs depending on the transmission mode, and the information included in the DCI also differs depending on the DCI format. FIG. 7 shows an example of control information (Common) that is commonly set for a plurality of TTIs indicated by one DCI and control information that is set for each TTI (Each TTI) in this operation example.

However, in this operation example, format 1C is excluded. format 1C is used for allocation of BCCH (Broadcast Control Channel), PCCH (Paging Control Channel), RACH (Random Access Control Channel) response, and very compact scheduling of one that is monitored only by CSS (Common search space) This is because it is assumed that BCCH, PCCH, and RACH are not latency reduced since they are used for PDSCH codewords. Therefore, even if the DCI format is written as "ALL" in FIG. 7, the DCI format 1C is not included.

Also, the control information for UL included in DCI for DL assignment is one for UL, and is described as "One value for UL".

As shown in FIG. 7, in this operation example, "HARQ process number (HARQ number)", "New data indicator (NDI)", "Redundancy version (RV)" and DCI format The "Transport block to codeword swap flag" included in 2/2A is individually set for multiple TTIs, and other control information related to DL allocation is commonly set for multiple TTIs.

Note that the Transport block to codeword swap flag is a parameter that indicates the relationship between a codeword and a Transport block (data). For example, if there are two transport blocks, in the transport block to codeword swap flag, bit "0" indicates a combination of transport block 1 and codeword 0, transport block 2 and codeword 1, and bit "1" indicates the opposite. , the combination of transport block 1 and codeword 1 and transport block 2 and codeword 0. With the transport block to codeword swap flag, by changing the combination of transport block and codeword at the time of retransmission, reception quality can be averaged between transport blocks.

That is, HARQ process number, NDI, RV, and Transport block to codeword swap flag are control information related to retransmission processing for DL data signals.

In this way, base station 100 allocates multiple TTIs using one DCI. At this time, base station 100 configures control information related to retransmission processing for each of a plurality of TTIs, and configures other control information (for example, resource allocation, MCS, etc.) in common for a plurality of TTIs. When base station 100 allocates multiple TTIs using one DCI, it is possible to reduce the ratio of control information (DCI) to resources compared to the case where DCI is transmitted individually for each TTI.

Also, by allocating the same frequency resource to a plurality of TTIs, there is an advantage that the DL reference signal (RS) can be shared.

FIG. 8 shows an example of DL allocation. In FIG. 8, the number of TTIs per subframe is 4, and the number of TTIs that can be assigned simultaneously to one DCI is 4.

In FIG. 8, Resource allocation indicating the presence or absence of resource allocation for each TTI is (0, 1, 1, 0), resources are allocated to the second and third TTIs, and indicates that the resource has not been allocated.

As shown in FIG. 8 , from base station 100 to terminal 200, on the frequency axis, common frequency resources are indicated for two TTIs allocated by DCI, while HARQ numbers (HARQ process numbers, NDI and RV are indicated every TTI.

Also, in the DL, as a reference signal used for DL data demodulation, there are cases of using a CRS (Cell specific Reference Signal) and a case of using a DMRS (Demodulation Reference Signal). In the case of CRS, terminal 200 demodulates data using CRS arranged in 1 subframe or 1 slot, regardless of whether resources are allocated in TTIs.

On the other hand, in the case of DMRS, the following two methods are conceivable as demodulation methods in terminal 200 .

The first method is a method in which terminal 200 demodulates data using only DMRSs allocated in TTIs to which resources are allocated. In this case, the base station 100 must ensure that the TTIs in which the DMRSs are allocated are included when allocating a plurality of TTIs. This method reduces the amount of DMRS resources used by terminal 200, and thus has the advantage of facilitating allocation of resources for other UEs to other TTIs.

The second method is a method in which terminal 200 demodulates data using DMRS within 1 subframe or within 1 slot, regardless of whether it is a TTI to which resources are allocated. With this method, when base station 100 allocates a plurality of TTIs, the DMRSs that can be used by terminal 200 do not change regardless of which TTIs resources are assigned to, so demodulation accuracy at terminal 200 can be ensured. However, it is necessary to limit the DMRS antenna ports that can be used when allocating a plurality of terminals 200 to different TTIs, or to limit TTI allocation to terminals 200 that can use DMRS in common.

[Operation example 2: UL]
In this operation example, similarly to DL, base station 100 (PDCCH generation section 103), as control information to be notified by one DCI, is used to notify resources for multiple TTIs within 1 subframe of UL. TTI information (Resource allocation) is newly added to indicate whether allocation is performed by DCI.

For example, as TTI information, the base station 100 adds bit strings for the number of TTIs that can be assigned simultaneously to one DCI, like DL. Each bit in the bit string corresponds to each TTI that can be assigned to one DCI simultaneously. For example, a 1 in a bit string indicates that the corresponding TTI has an allocation, and a 0 indicates that the corresponding TTI does not have an allocation. Terminal 200 identifies the presence or absence of allocation for each TTI based on the TTI information included in one DCI.

FIG. 9 shows an example of control information (Common) that is commonly set for a plurality of TTIs indicated by one DCI and control information that is set for each TTI (Each TTI) in this operation example. Note that there are two types of DCI formats, DCI format 0 and DCI format 4, which instruct UL data allocation, so FIG. 9 shows an example in which there are two types of DCI formats.

In UL allocation, unlike DL, HARQ process number and Redundancy version (RV) are not notified, and HARQ process number and Redundancy version (RV) are not reported according to a predetermined rule between base station 100 and terminal 200. Change. Therefore, in UL allocation, only the New data indicator (NDI) is transmitted individually in multiple TTIs, and other control information related to UL allocation is transmitted in common in multiple TTIs. That is, the control information for retransmission processing for UL data signals is NDI.

In this way, base station 100 allocates multiple TTIs using one DCI. At this time, the base station 100 configures a control signal (NDI) related to retransmission processing for each of multiple TTIs, and configures other control information (for example, resource allocation, MCS, etc.) in common for multiple TTIs. When base station 100 allocates multiple TTIs using one DCI, it is possible to reduce the ratio of control information (DCI) to resources compared to the case where DCI is transmitted individually for each TTI.

Moreover, there is an advantage that the same frequency resource can be allocated to multiple TTIs, so that the UL reference signal (RS) can be shared. In particular, in UL, it is necessary to transmit an RS for each terminal 200, so sharing the RS in a plurality of TTIs is effective in reducing the RS and improving the channel quality measurement accuracy.

Also, in UL, UEs transmit retransmissions using TTIs with the same HARQ number. However, since DCI does not include HARQ number notification as described above, TTIs corresponding to signals with the same HARQ number are sequentially determined according to a predetermined rule. For example, the HARQ number is 8 in conventional FDD to which latency reduction is not applied. Therefore, since the same HARQ number is used every 8 TTIs, the UE can retransmit the signal every 8 TTIs.

In UL, there are two retransmission methods called adaptive retransmission and non-adaptive retransmission.

Adaptive retransmission is a retransmission method in which the base station instructs the UE to retransmit using DCI (NDI), allocates resources using DCI, and newly notifies MCS and the like each time retransmission is performed. In assignments other than SPS (Semi Persistent Scheduling), the UE determines whether it is retransmission or new data assignment according to the value of NDI. Specifically, in a certain HARQ number, if the NDI notified by DCI is the same as the NDI included in the DCI that instructed the UL data signal of the same HARQ number last time (Non-toggle), the UE is retransmitted. If the NDI is different from the previous NDI (Toggle), the UE determines that new data is allocated. Adaptive retransmission can be instructed to retransmit until new data is assigned with the same HARQ number, and it is also possible to instruct retransmission after 16 TTIs after 8 TTIs without instructing retransmission after 8 TTIs.

Non-adaptive retransmission is a retransmission method in which a base station instructs a UE to retransmit only with an ACK/NACK signal indicated by a PHICH (Physical HARQ Indicator Channel) and does not transmit DCI. In non-adaptive retransmission, the UE determines whether or not to retransmit according to the PHICH. Specifically, in FDD, when NACK is notified by the PHICH from the base station in DL after 4 TTIs of UL data signal transmission, the UE further transmits at TTI with the same HARQ number after 4 TTIs and uses the same frequency as the previous transmission. Send a retransmission signal on the resource and MCS. In addition, when ACK is notified by PHICH and the UE does not detect DCI, the UE does not transmit the UL data signal with the corresponding HARQ number, but instead performs adaptive retransmission while saving the previously transmitted signal in the buffer. Prepare.

In this operation example, when multiple TTIs are allocated in latency reduction, a case where both non-adaptive retransmission and adaptive retransmission are supported, and a case where only adaptive retransmission is supported will be described.

[When non-adaptive retransmission and adaptive retransmission are supported]
10A and 10B show an example of supporting both non-adaptive and adaptive retransmissions. 10A and 10B, the number of TTIs per subframe is 4, and the number of TTIs that can be assigned to one DCI at the same time is 4. In FIG. Also, in FIGS. 10A and 10B, HARQ numbers are assigned sequentially for each TTI, and the same HARQ number is assigned after X subframes.

In subframe N shown in FIG. 10A , Resource allocation indicating resource allocation for TTIs is (1, 1, 1, 0), new data is allocated to the first, second, and third TTIs, and 4 th TTI has no data allocated. For new data allocated to each TTI, frequency resource allocation (PRB) and MCS (MCS=6) are set commonly between TTIs, and NDI is set for each TTI. In FIG. 10A, all NDIs for the 1st, 2nd and 3rd TTIs are Toggle (new data allocation).

In subframe N+X (that is, a subframe with the same HARQ number as subframe N) after X subframes shown in FIG. Suppose 2,3 are new data allocations.

In this case, the Resource allocation shown in FIG. 10B is (1, 0, 1, 1).

That is, in the resource allocation shown in FIG. 10B, new data allocation and allocation to 1st TTI, 3rd TTI, and 4th TTI corresponding to HARQ numbers #0, #2, and #3 for adaptive retransmission are present (1). . Also, in FIG. 10B, the NDI for the 1st TTI of HARQ#0 is Non-toggle, which indicates allocation of retransmission data, the NDI for the 3rd TTI of HARQ#2 and the 4th TTI of HARQ#3 is Toggle, and new data Show assignment. The same frequency resource is allocated to the 1st TTI, 3rd TII, and 4th TTI of HARQ#0, 2, and 3 allocated by one DCI, and the same MCS (MCS=7) is set.

On the other hand, in subfrme N+X, no allocation (0) is made to the 2nd TTI corresponding to HARQ number #1 for non-adaptive retransmission. That is, the DCI notified from base station 100 does not include allocation for the 2nd TTI for non-adaptive retransmission. In FIG. 10B, the PHICH for the 2nd TTI of HARQ#1 is NACK. Therefore, in the case of non-adaptive retransmission, terminal 200 retransmits using the same frequency resource and MCS (MCS=6) as Subframe N.

In this way, the base station 100 transmits the PHICH including the ACK/NACK signal for the UL data signal assigned in the TTI for non-adaptive retransmission among a plurality of TTIs, and the TTI for adaptive retransmission is assigned. Transmit DCI including NDI for UL data signals. In other words, the base station 100 does not include the allocation for the TTIs for non-adaptive retransmission in the DCI. Then, terminal 200 performs retransmission processing based on PHICH in TTIs in which non-adaptive retransmission is performed, and performs retransmission processing based on NDI in TTIs in which adaptive retransmission is performed.

Thus, in non-adaptive retransmissions, assignment to TTIs using one DCI is not performed, so in subframes including TTIs in which non-adaptive retransmissions are performed, in other TTIs, new UL data assignments or adaptive retransmissions DCI is not sent if there is no data for Therefore, there is an advantage that the overhead of the control signal can be reduced when there is no DCI allocation.

[When only adaptive retransmission is supported]
Figures 11A and 11B show an example of supporting only adaptive retransmissions. 11A and 11B, the number of TTIs per subframe is 4, and the number of TTIs that can be assigned to one DCI at the same time is 4. In FIG. Also, in FIGS. 11A and 11B, HARQ numbers are assigned sequentially for each TTI, and it is defined that the same HARQ number is assigned after X subframes.

In subframe N shown in FIG. 11A, Resource allocation indicating resource allocation for TTIs is (1, 1, 1, 0) as in FIG. 10A, and new data is allocated to the first, second, and third TTIs. and the fourth TTI has no data assigned.

In subframe N+X (that is, a subframe with the same HARQ number as subframe N) after X subframes shown in FIG. Suppose there is

In this case, the Resource allocation shown in FIG. 11B is (1, 1, 1, 1).

That is, in the resource allocation shown in FIG. 11B, new data allocation and allocation to 1st TTI, 2nd TTI, 3rd TTI, and 4th TTI corresponding to HARQ numbers #0, #1, #2, and #3 for adaptive retransmission are performed. Yes (1). Also, in FIG. 11B , the NDI for the 1st TTI of HARQ#0 and the 2nd TTI of HARQ#1 is non-toggle, indicating allocation of retransmission data, and the NDI for the 3rd TTI of HARQ#2 and the 4th TTI of HARQ#3 is toggle. , indicating a new data allocation. Note that HARQ#0, 1, 2, and 3 1stTTI, ^2nd TTI, ^3rd TII, and ^4th TTI assigned by one DCI are assigned the same frequency resource and the same MCS (MCS= 7) is set.

In this way, base station 100 transmits DCI including NDI for UL data signals allocated in multiple TTIs for adaptive retransmission, but does not transmit PHICH. This has the advantage of eliminating the need for PHICH resources when only adaptive retransmission is supported. Note that if there is adaptive retransmission or new data allocation in any one of the TTIs within one subframe, the base station 100 transmits DCI in that subframe, but retransmission data allocation can also be notified with the same DCI. PHICH is unnecessary. In other words, a scheme that supports only adaptive retransmission that does not require PHICH is effective in reducing overhead.

Also, when only adaptive retransmission is supported, frequency allocation and MCS within one subframe are common between TTIs. The common frequency resource has the advantage of being able to share reference signals between TTIs and the advantage of being less likely to collide with data allocation of other UEs. In particular, conventional UE data allocation is performed in units of subframes or slots, so if frequency resources are available within a subframe or slot, there is an advantage that collisions are less likely to occur when allocating data resources for conventional UEs. There is

Note that in UL, if resources are not allocated to all TTIs within one subframe, terminal 200 may transmit only reference signals arranged in the allocated TTIs. In this case, a reference signal can be transmitted in each UE if signals addressed to other UEs are allocated in other TTIs.

Operation example 1 and operation example 2 have been described above.

Thus, in the present embodiment, base station 100 generates one DCI including control information for multiple shortened TTIs and transmits it to terminal 200 . In DCI, control information related to retransmission processing of DL/UL data signals is set for each of multiple shortened TTIs, and control information other than control information related to retransmission processing is commonly assigned to multiple shortened TTIs.

As a result, even when latency reduction is applied and a shortened TTI is used, it is possible to suppress an increase in the ratio of DCI to all resources. Therefore, according to the present embodiment, resources can be used efficiently even when the TTI length is shortened.

Furthermore, in the present embodiment, when shortening the TTI length, one DCI includes resource allocation for TTIs arranged in one subframe. This allows TTIs included in the same subframe to share the same reference signal. Therefore, since reference signals do not need to be arranged for each TTI, it is possible to prevent reduction of resources that can be allocated to data and prevent deterioration of throughput. Furthermore, in latency reduction, by notifying TTI allocation in units of subframes using DCI, scheduling between UEs to which latency reduction is not applied (that is, UEs to which resources are allocated in units of subframes) is facilitated. Become.

Further, according to the present embodiment, the DCI includes information (resource allocation) indicating whether or not there is an allocation to each of a plurality of shortened TTIs. By this means, terminal 200 can identify the presence or absence of assignment to a plurality of TTIs when the DCI is correctly received. For example, when a plurality of TTIs are notified by individual DCI, even though the base station has transmitted the DCI, a situation where the UE cannot detect the DCI (misdetection) may occur, whereas this implementation can avoid misdetection.

Although HARQ numbers are illustrated in the present embodiment, the HARQ numbers are counted by base station 100 and terminal 200, respectively, and are not necessarily common values. In addition, the number of HARQ numbers is defined, and the base station 100 and the terminal 200 cyclically count up the HARQ number for each TTI. can recognize that there is

Further, in the present embodiment, it is assumed that the HARQ number is not notified by DCI in UL and the same HARQ process is used between base station 100 and terminal 200, but in UL as well as in DL may notify the HARQ number to In this case, HARQ numbers are individually set for a plurality of UL TTIs in DCI, similar to DL.

Also, the case where a plurality of TTIs that can be assigned using one DCI has been described as a TTI within 1 subframe, but a plurality of TTIs that can be assigned using one DCI can be set within 1 slot or as defined in advance. It may be the number of TTIs. The advantages of allocating multiple TTIs described above are also obtained within one slot or as a defined number of TTIs.

Also, a DCI that allocates multiple TTIs may be mapped only to the PDCCH and not mapped to the EPDCCH. Since the PDCCH is arranged at the beginning of the subframe, it is possible to shorten the time in which terminal 200 can complete DCI reception. On the other hand, since the EPDCCH is arranged up to the last OFDM symbol of the subframe, there is a feature that the time in which terminal 200 can complete DCI reception becomes longer. Therefore, by arranging DCI in PDCCH, base station 100 completes reception of DCI at terminal 200 early, and in latency reduction, terminal 200 feeds back an ACK/NACK signal for DL data or a UL data signal. There is an advantage that it is possible to secure a preparation period until the transmission of the

Conversely, DCIs that allocate multiple TTIs may be mapped only to EPDCCHs and not mapped to PDCCHs. Since the PDCCH is placed at the beginning of the subframe, the amount of resources is limited. DCI that indicates a plurality of TTIs is characterized by a large amount of information and a longer code length than DCI that indicates only one TTI. On the other hand, the EPDCCH has the feature that it is easier to adjust the amount of resources than the PDCCH because the resources can be increased in the frequency direction. Therefore, base station 100 can prevent PDCCH resource tightness by allocating DCIs that allocate multiple TTIs only to EPDCCHs.

In addition, although PDCCH or EPDCCH is used as a resource in which DCI is allocated, it may be New PDCCH newly set for latency reduction.

(Embodiment 2)
In the present embodiment, a method of transmitting ACK/NACK signals for DL data signals assigned to multiple TTIs in one subframe when latency reduction is applied will be described.

Since the base station and terminal according to this embodiment have the same basic configuration as base station 100 and terminal 200 according to Embodiment 1, they will be described with reference to FIGS.

When multiple TTIs of DL data signals are allocated per subframe, an ACK/NACK signal for the DL data signals is generated for each TTI. Also, since an ACK/NACK signal is set for each codeword, one or two ACK/NACK signals are generated per TTI when a DL data signal is assigned.

Here, as described in Embodiment 1, base station 100 notifies terminal 200 of multiple TTI assignments using one DCI. In this case, the PUCCH resource used for transmitting the ACK/NACK signal can be implicitly determined by being associated with the CCE (Control Channel Element) number or ECCE (Enhanced CCE) number of the PDCCH or EPDCCH that transmitted the DCI. is assumed. By doing so, there is an advantage that it is not necessary to newly indicate the location of the PUCCH resource even when latency reduction is applied.

[Description of PUCCH resource]
The format of the PUCCH resource used for transmitting the ACK/NACK signal differs depending on the number of bits of the ACK/NACK signal.

When the ACK/NACK signal is 1 bit, PUCCH format 1a is used, and when the ACK/NACK signal is 2 bits, PUCCH format 1b is used. Also, when the ACK/NACK signal is 3 bits or more, the number of bits is reduced by bundling/multiplexing or channel selection, and PUCCH format 1a/1b or PUCCH format 3 is used. Note that PUCCH format 3 is used when the upper layer indicates that PUCCH format 3 is to be used.

Also, frequency hopping is applied to PUCCH transmission, and PUCCH is transmitted at different frequencies (PRB) in the 1st slot and 2nd slot of UL.

12A and 12B are conceptual diagrams of PUCCH resources of PUCCH format 1a/1b.

As shown in FIGS. 12A and 12B, in the case of Normal CP, in PUCCH format 1a/1b, ACK/NACK signals are arranged in SC-FDMA symbols #0, 1, 5, and 6 in each slot, and reference signal (RS) are arranged in SC-FDMA symbol#2, 3, and 4 in each slot. The ACK/NACK signal is coded by orthogonal sequences of code length 4, and the reference signal is coded by orthogonal sequences of code length 3. However, as shown in FIG. 12B, when the SRS is placed in the last OFDM symbol of the 2nd slot, the ACK/NACK signal is also encoded with orthogonal sequences of code length 3.

PUCCH format 3 is a format that can transmit multiple ACK/NACK bits simultaneously, and can transmit up to 48 bits. The reference signal is arranged in SC-FDMA symbols #1 and 5 in each slot in the case of normal CP, and arranged in SC-FDMA symbol #3 in each slot in extended CP (for example, Non-Patent Document 2 ).

Operation examples 1 and 2 according to the present embodiment will be described below.

[Operation example 1]
In this operation example, terminal 200 (signal allocation section 210) makes the arrangement of ACK/NACK signals generated for each TTI common to the arrangement of ACK/NACK signals and reference sisgnal of conventional PUCCH format 1a/1b. .

However, terminal 200 limits the positions where ACK/NACK signals are arranged for each TTI. For example, terminal 200 allocates ACK/NACK signals to DL data signals in the order of allocation in DL TTIs. That is, the ACK/NACK signal for the DL data signal transmitted in the earlier TTI among the multiple TTIs is mapped to the earlier resource among the PUCCH resources. By this means, the base station 100 can reduce the delay amount of the ACK/NACK signal when receiving the ACK/NACK signal for the DL data signal transmitted in multiple TTIs.

In addition, in this operation example, the reference signal arranged in the slot is shared between TTIs transmitted in the same slot.

<For 2 TTI per 1 subframe>
Terminal 200 transmits an ACK/NACK signal for the DL data signal assigned to the 1st slot in DL only in the 1st slot of the PUCCH resource in UL, and ACK/NACK the DL data signal assigned to the 2nd slot in DL. Signals are transmitted only in the 2nd slot of the PUCCH resource, even in UL.

At this time, terminal 200 uses the same Orthogonal sequences as conventional PUCCH for ACK/NACK signals.

In this way, although there is no frequency hopping gain in the PUCCH resource of terminal 200 to which latency reduction is applied, it is coded with the same Orthogonal sequences as conventional UEs. It has the advantage of allowing allocation.

<In case of 4TTI per 1 subframe>
FIG. 13 shows allocation of PUCCH resources (SC-FDMA symbols) for transmitting ACK/NACK signals for DL data signals allocated to TTIs within a subframe on DL in the case of four TTIs per subframe.

As shown in Fig. 13, the 1st slot of UL is common for ACK/NACK signals corresponding to 1st TTI and 2nd TTI, and the ^2nd slot of UL is common for ACK/NACK signals corresponding to 3rd TTI and 4th TTI. and Also, as shown in FIG. 13, the number of SC-FDMA symbols for transmitting ACK/NACK signals corresponding to each TTI is two, so the code length of Orthogonal sequences is two. For example, Sequence index#0 is the sign [+1 +1] and Sequence index#1 is [+1 -1]. Reference signals are assigned to SC-FDMA#2, 3, and 4, and the code length of Orthogonal sequences is 3.

14A and 14B show an operation example in the case of 4 TTIs per subframe.

In the DL shown in FIG. 14A, DL data signals are assigned to the 2nd TTI, 3rd TTI, and 4th TTI.

In FIG. 14B, terminal 200 transmits an ACK/NACK signal for a DL data signal allocated in the 2nd TTI of DL using SC-FDMA#5 and #6 of the 1st slot of UL. At that time, terminal 200 transmits a reference signal for the 2nd TTI in SC-FDMA#2, 3, 4 of the 1st slot.

Also, in FIG. 14B , terminal 200 transmits an ACK/NACK signal for the DL data signal allocated in the 3rd TT of DL using SC-FDMA#0,1 in the 2nd slot of UL, and allocates it using the 4th TTI of DL. ACK/NACK signals for the received DL data signals are transmitted using SC-FDMA#5 and 6 in the 2nd slot of UL. At that time, terminal 200 transmits reference signals for the 3rd TTI and 4th TTI using SC-FDMA#2, 3, and 4 in the 2nd slot. That is, the 3rd TTI and the 4th TTI share the reference signal.

Note that when the final SC-FDMA symbol (SC-FDMA#6) of the 2nd slot of UL is reserved in the SRS, the symbol capable of transmitting the 4thTTI ACK/NACK signal is one symbol (SC-FDMA#5). In this case, the ACK/NACK signal transmission method is a method of transmitting the ACK/NACK signal using only one symbol, and a method of bundling or multiplexing the 3rd TTI ACK/NACK signal and the 4th TTI ACK/NACK signal for transmission. There is. Bundling is a method of reducing the number of bits when the number of ACK/NACK bits is larger than the number of transmittable bits, and reduces the amount of information. Multiplexing is a method in which each ACK/NACK signal is 1 bit, combined (multiplexed) into 2 bits, and transmitted in Format 1b.

The method of transmitting an ACK/NACK signal using only one symbol degrades the reception quality of the 4th TTI ACK/NACK signal, but has the advantage of not extending the delay time of the 3rd TTI ACK/NACK signal.

On the other hand, the method of bundling or multiplexing the ACK/NACK signal of the 3rd TTI and the ACK/NACK signal of the 4th TTI for transmission increases the delay time of the ACK/NACK signal of the 3rd TTI, but the ACK/NACK signal after bundling There is an advantage that the signal reception quality can be ensured. Specifically, terminal 200 assigns ACK/NACK signals to SC-FDMA symbols #0, 1, and 5 in the 2nd slot, and sets the code length of Orthogonal sequences to 3.

<For 14 TTI per subframe>
In the case of 14 TTIs per subframe, if an ACK/NACK signal is transmitted every TTI, SC-FDMA symbols for transmitting reference signals (RS) will run out. Therefore, in this operation example, terminal 200 bundles or multiplexes ACK/NACK signals of a plurality of TTIs and transmits them.

FIG. 15 shows allocation of PUCCH resources (SC-FDMA symbols) for transmitting ACK/NACK signals for DL data signals allocated to TTIs within a subframe on DL in the case of 14 TTIs per subframe.

When DL data is allocated to multiple TTIs, terminal 200 performs bundling or multiplexing of ACK/NACK signals and sets the number of SC-FDMA symbols for transmitting ACK/NACK signals to two. Therefore, the code length of the orthogonal sequences of the ACK/NACK signal of each TTI is 2 per 1 subframe, as in 4TTIs. Reference signals are assigned to SC-FDMA#2, 3, and 4, and the code length of Orthogonal sequences is 3.

As shown in FIG. 15, in UL, 1st slot SC-FDMA symbols #0 and 1 are common to ACK/NACK signals corresponding to 1st TTI to 4th TTI, and 1st slot SC-FDMA symbols #5 and 6 are common. are common for the ACK/NACK signals corresponding to the 5th TTI to 7th TTI, SC-FDMA symbols #0 and 1 of the 2nd slot are common to the ACK/NACK signals corresponding to the 8th TTI to 11th TTI, and SC-FDMA symbols #5 and #6 are common for ACK/NACK signals corresponding to 12th TTI to 14th TTI.

As a method of applying bundling and multiplexing in the case of 14 TTIs per subframe, if the total number of codewords of a plurality of TTIs is 2 or less, terminal 200 does not apply bundling and multiplexing, and ACKs each codeword. Alternatively, a signal corresponding to NACK is transmitted in BPSK or QPSK.

On the other hand, when the total number of codewords of a plurality of TTIs is 3 or more, terminal 200 first bundles (spatial bundling) an ACK/NACK signal if a plurality of codewords are allocated within a TTI. As a bundling method, for example, the bundling method used for TDD carrier aggregation (see FIG. 16) is followed.

In this operation example, as shown in FIG. 15, ACK/NACK signals of 4 TTIs at maximum are transmitted as one signal, so the number of ACK/NACK bits after spatial bundling is 4 at maximum. When the number of ACK/NACK bits after spatial bundling is 2, terminal 200 transmits a signal corresponding to ACK or NACK in QPSK.

On the other hand, when the number of ACK/NACK bits after spatial bundling is 3 or 4, terminal 200 further bundles the ACK/NACK signal between TTIs. As a bundling method, for example, the method used for TDD carrier aggregation (see FIG. 17) is followed. This bundling compresses the number of bits of the ACK/NACK signal to 2 bits.

FIG. 18 shows an operation example in the case of 14 TTIs per subframe.

In the case where ACK/NACK signals are transmitted in SC-FDMA symbols #0 and 1 of the 1st slot shown in FIG. 1 and the total number of codewords is 2.

Also, in the case where ACK/NACK signals are transmitted in SC-FDMA symbols #5 and #6 of the 2nd slot shown in FIG. assigned.

Therefore, in these cases where the total number of codewords in multiple TTIs is 2 or less, terminal 200 transmits a signal corresponding to ACK or NACK of each codeword in BPSK or QPSK.

Next, in the case where ACK/NACK signals are transmitted in SC-FDMA symbols #5 and #6 of the 1st slot shown in FIG. 18, DL data signals are allocated to three TTIs of 5th TTI, 6th TTI and 7th TTI, The number of codewords for each is 1, and the total number of codewords is 3. In this case, terminal 200 performs time domain bundling (3 to 2 bundling) of ACK/NACK signals of the 5th TTI, 6th TTI, and ^7th TTI according to FIG. In FIG. 18, the ACK/NACK signals of the three TTIs are ACK, ACK, and ACK, respectively, so after bundling, they become ACK and ACK.

Also, in the case where ACK/NACK signals are transmitted in SC-FDMA symbols #0 and 1 of the 2nd slot shown in FIG. and 2 codewords are allocated for MIMO transmission in each TTI. Therefore, the total number of codewords is eight. In this case, terminal 200 first performs Spatial Bundling of ACK/NACK signals within each TTI according to FIG. Compress the ACK/NACK signal to 2 bits. In FIG. 18, the ACK/NACK signals of each TTI after spatial bundling are ACK, ACK, NACK, NACK, and the ACK/NACK signals after time domain bundling are NACK, ACK.

In addition, in this operation example, since it is premised on the multiple TTI allocation method described in Embodiment 1, if the terminal 200 can correctly receive the DCI, all TTI DL data allocation in the same subframe can be received correctly. Therefore, the terminal 200 does not miscalculate the total number of codewords. This point is also an advantage of the first embodiment. Therefore, terminal 200 can compress and transmit ACK/NACK signals by performing bundling or multiplexing only on TTIs in which data allocation has occurred.

[Operation example 2]
In this operation example, terminal 200 performs bundling or multiplexing on ACK/NACK signals generated in each TTI, and arranges them over resources for ACK/NACK within one subframe of UL.

This allows PUCCH frequency hopping to be supported.

Also, in this operation example, terminal 200 uses the existing PUCCH format regardless of the number of TTIs in one subframe. This has the advantage of being able to share PUCCH resources with conventional UEs.

For example, when PUCCH format 1a/1b is used and PUCCH format 3 is not used, terminal 200 compresses ACK/NACK signals of all TTIs to 2 bits. As in Operation Example 1 of the present embodiment, the compression method performs spatial bundling of ACK/NACK signals of a plurality of codewords within a TTI, and then time domain bundling between TTIs (see FIGS. 16 and 17).

Note that when the number of TTIs allocated per subframe is 2, the ACK/NACK signal can be compressed to 2 bits by spatial bundling, so time domain bundling between TTIs is unnecessary.

Also, when the number of TTIs assigned per subframe is 3 or 4, terminal 200 performs time domain bundling between TTIs in addition to spatial bundling. Time domain bundling is performed according to FIG. Also, when application of Channel selection is determined in advance, terminal 200 can transmit a 3-bit or 4-bit ACK/NACK signal without performing time domain bundling.

In addition, when the number of TTIs allocated per subframe is 5 or more, terminal 200 compresses the ACK/NACK signal to 4 bits if application of Channel selection is predetermined. On the other hand, when application of Channel selection is not defined, terminal 200 compresses the ACK/NACK signal to 2 bits. As a method of compressing an ACK/NACK signal of 5 bits or more to a ACK/NACK signal of 2 bits, for example, the method shown in FIG. 17 can be considered.

Also, when transmission in PUCCH format 3 is permitted by higher layer signals, terminal 200 can transmit multiple ACK/NACK signals using PUCCH format 3. In this case, since the terminal 200 can transmit the ACK/NACK signal without compression, there is an advantage that the information amount of the ACK/NACK signal does not decrease.

In this embodiment, a case has been described in which ACK/NACK signals are transmitted using PUCCH resources. There is also a method of transmitting in a data signal. In this case, if any one of a plurality of UL TTIs is assigned an UL data signal, the terminal 200 transmits a plurality of ACK/NACK signals corresponding to the DL TTIs on that TTI. may By doing so, the PUCCH format and the PUSCH format do not coexist within the UL subframe, and terminal 200 has the advantage of being able to transmit subframes in one format.

Operation example 1 and operation example 2 have been described above.

Thus, in the present embodiment, when terminal 200 transmits ACK/NACK signals for DL data signals transmitted in shortened TTIs using PUCCH resources, terminal 200 supports the earlier TTI among a plurality of shortened TTIs. The more ACK/NACK signals are allocated to earlier time resources (SC-FDMA symbols) among PUCCH resources. By doing so, the ACK/NACK signal corresponding to the earlier TTI among the multiple shortened TTIs in one subframe is fed back to the base station 100 earlier, and the delay amount of the ACK/NACK signal can be reduced. .

Further, in the present embodiment, the reference signal arranged in one slot is shared for the TTI corresponding to the ACK/NACK signal arranged in one slot. By doing so, it becomes unnecessary to arrange the reference signal for each TTI.

It should be noted that this embodiment has been described on the premise that base station 100 notifies terminal 200 of allocation of multiple TTIs using one DCI, as in Embodiment 1. FIG. However, in this embodiment, the method of notifying allocation of multiple TTIs is not limited to the method described in Embodiment 1, and other methods may be used. The method of the present embodiment can also be applied, for example, to the case of allocating DL data signals by DCI for each TTI without assuming the method of allocating a plurality of TTIs in the first embodiment. In this case, among a plurality of TTIs, even though base station 100 has transmitted DCI, there is a possibility that terminal 200 cannot detect DCI (misdetection). In this case, the base station 100 can specify the TTIs to be subjected to the bundling or multiplexing by adding information on the number of allocated TTIs to the DCI. As a result, when the base station 100 and the terminal 200 can identify the TTI that the terminal 200 cannot detect, it can be treated as DTX in the same way as NACK.

Also, in the present embodiment, the method of compressing ACK/NACK signals based on FDD has been described. However, when applying to TDD, the method of this embodiment can be applied by further applying bundling between subframes.

The embodiments of the present disclosure have been described above.

In the above-described embodiment, a case where one aspect of the present disclosure is configured by hardware has been described as an example, but the present disclosure can also be implemented by software in cooperation with hardware.

Each functional block used in the description of the above embodiments is typically implemented as an LSI, which is an integrated circuit. The integrated circuit may control each functional block used in the description of the above embodiments and may have inputs and outputs. These may be made into one chip individually, or may be made into one chip so as to include part or all of them. Although LSI is used here, it may also be called IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.

Also, the method of circuit integration is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array) that can be programmed after the LSI is manufactured, or a reconfigurable processor that can reconfigure the connections and settings of the circuit cells inside the LSI may be used.

Furthermore, if an integration technology that replaces the LSI appears due to advances in semiconductor technology or another derived technology, the technology may naturally be used to integrate the functional blocks. Application of biotechnology, etc. is possible.

The base station of the present disclosure includes a generation unit that generates one Downlink Control Information (DCI) including control information for a plurality of first TTIs with a TTI length shorter than a second TTI (Transmission Time Interval); and a transmission unit that transmits DCI, wherein control information related to data signal retransmission processing is set for each of the plurality of first TTIs in the DCI, and frequency resources and MCS (Modulation and coding scheme) Control information is set in common to the plurality of first TTIs, and DMRS (Demodulation Reference Signal) is allocated to the plurality of first TTIs.

In the base station of the present disclosure, DCI includes information indicating whether or not there is allocation for each of the plurality of first TTIs.

In the base station of the present disclosure, in DCI, control information related to retransmission processing for downlink data signals is HARQ process number, New Data Indicator (NDI), Redundancy Version (RV), or multiple transport blocks and codewords is information indicating a combination of

In the base station of the present disclosure, in DCI, control information related to retransmission processing for uplink data signals is New Data Indicator (NDI).

In the base station of the present disclosure, the transmission unit transmits a PHICH (Physical HARQ Indicator Channel) including an ACK/NACK signal for an uplink data signal assigned in a TTI that performs non-adaptive retransmission among a plurality of first TTIs. Then, DCI including NDI for the uplink data signal allocated in the TTI for adaptive retransmission is transmitted, and the DCI does not include the allocation for the TTI for non-adaptive retransmission.

In the base station of the present disclosure, the transmitting unit transmits DCI including NDI for uplink data signals allocated in multiple first TTIs for adaptive retransmission, and the transmitting unit transmits PHICH (Physical HARQ Indicator Channel). do not.

In the base station of the present disclosure, multiple first TTIs are arranged within one subframe.

In the base station of the present disclosure, multiple first TTIs are arranged within one slot.

The base station of the present disclosure further includes a receiving unit that receives an ACK/NACK signal for the downlink data signal transmitted in the first TTI, and is transmitted in an earlier TTI in the first TTI. An ACK/NACK signal for a downlink data signal is mapped to an earlier time resource among uplink resources.

In the base station of the present disclosure, the receiving unit receives a reference signal, and the reference signal is shared among TTIs in which ACK/NACK is arranged in the same slot among the plurality of first TTIs.

The base station of the present disclosure further includes a receiving unit that receives an ACK/NACK signal for the downlink data signal transmitted in the first TTI, and the ACK/NACK signal corresponding to each of the first TTIs is Bundling or It is multiplexed and arranged over resources for ACK/NACK within one subframe.

A terminal of the present disclosure includes a receiving unit that receives one Downlink Control Information (DCI) including control information for a plurality of first TTIs with a TTI length shorter than a second TTI (Transmission Time Interval), and the DCI and a signal allocation unit that allocates the uplink data signal to uplink resources using the DCI, wherein the DCI retransmits the data signal. Control information for is set for each of the plurality of first TTIs, control information for frequency resources and MCS (Modulation and coding scheme) is set commonly for the plurality of first TTIs, DMRS (Demodulation Reference signal) is placed in the plurality of first TTIs.

The communication method of the present disclosure generates one Downlink Control Information (DCI) containing control information for a plurality of first TTIs with a TTI length shorter than that of a second TTI (Transmission Time Interval), and transmits the DCI. and, in the DCI, control information related to data signal retransmission processing is set for each of the plurality of first TTIs, and control information related to frequency resources and MCS (Modulation and coding scheme) is set to the plurality of first TTIs. A DMRS (Demodulation Reference Signal) is allocated to the plurality of first TTIs.

The communication method of the present disclosure receives one Downlink Control Information (DCI) including control information for a plurality of first TTIs with a TTI length shorter than a second TTI (Transmission Time Interval), and uses the DCI separates a downlink data signal from a received signal, and assigns the uplink data signal to an uplink resource using the DCI, and in the DCI, control information related to retransmission processing of the data signal is generated for each of the plurality of first TTIs. Control information about frequency resources and MCS (Modulation and coding scheme) is set in common to the plurality of first TTIs, and DMRS (Demodulation Reference signal) is allocated to the plurality of first TTIs .

One aspect of the present disclosure is useful for mobile communication systems.

100 base station 101 TTI determination unit 102 MCS determination unit 103 PDCCH generation unit 104, 208 error correction coding unit 105, 209 modulation unit 106, 210 signal allocation unit 107, 211 transmission unit 108, 201 reception unit 109, 202 signal separation unit 110 PUCCH receiving section 111, 203 demodulating section 112, 204 error correction decoding section 113 ACK/NACK determining section 200 terminal 205 error determining section 206 ACK/NACK generating section 207 PDCCH receiving section

Claims (9)

a receiving unit that receives downlink control information (DCI) for resource allocation in a plurality of time units, which is a time unit for transmitting and receiving data that is shorter than one subframe;
a transmission unit that transmits uplink data based on the DCI;
and
the DCI includes first information for each of the plurality of time units and second information for all of the plurality of time units, the second information including frequency resource allocation and MCS;
terminal. The DCI includes information indicating the presence or absence of resource allocation for each of the plurality of time units,
A terminal according to claim 1 . The first information includes HARQ process number, New Data Indicator (NDI), Redundancy Version (RV), or information indicating a combination of multiple transport blocks and codewords,
A terminal according to claim 1 or 2. The plurality of time units are included in one subframe,
A terminal according to any one of claims 1 to 3. The plurality of time units are included in one slot,
A terminal according to any one of claims 1 to 3. each of the plurality of time units is shorter than one subframe;
A terminal according to any one of claims 1 to 3. each of the plurality of time units is shorter than one slot;
A terminal according to any one of claims 1 to 3. receiving downlink control information (DCI) for resource allocation in a plurality of time units, which are time units for transmitting and receiving data shorter than one subframe;
transmitting uplink data based on the DCI;
and
the DCI includes first information for each of the plurality of time units and second information for all of the plurality of time units, the second information including frequency resource allocation and MCS;
Communication method. A process of receiving downlink control information (DCI) for resource allocation in a plurality of time units, which is a time unit for transmitting and receiving data shorter than one subframe;
a process of transmitting uplink data based on the DCI;
to control the
the DCI includes first information for each of the plurality of time units and second information for all of the plurality of time units, the second information including frequency resource allocation and MCS;
integrated circuit.

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