JP7095009B2 - Base station, communication method and integrated circuit - Google Patents

Description

The present disclosure relates to base stations and communication methods.

In recent years, it has been considered to realize an application that requires a reduction in delay time (delay critical). Examples of applications that require reduced delay times include autonomous driving of cars, ultra-reality applications in smart glasses, or communication between devices.

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

FIG. 1 shows an example of shortened TTI in the case of normal CP. When the TTI length is 0.5 msec (= 1 slot), 2 TTIs are arranged per 1 msec. Also, when 1slot is divided into TTI with 4OFDM symbols and TTI with 3OFDM symbols, 4TTI is placed per 1msec. If the TTI length is 1 OFDM symbol, 14 TTIs are placed per 1 msec.

By shortening the TTI length, the delay of CQI reporting can be shortened and the frequency of CQI reporting can be increased, which has the advantage of reducing the discrepancy between CQI reporting and the actual line quality.

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) informs the terminal (sometimes called UE (User Equipment)) of resource allocation and MCS (Modulation and coding scheme). It is conceivable that DCI (Downlink Control Information) is transmitted for each shortened TTI.

However, as shown in FIG. 2, when the base station transmits a DCI (EPDCCH (Enhanced Physical Downlink Control Channel)) having the same amount of information as the DCI of the conventional TTI having a TTI length of 1 msec (EPDCCH (Enhanced Physical Downlink Control Channel)) to each TTI, Compared to the conventional method, a control signal is required several times as much as TTI per 1 msec. Therefore, there is a problem that the ratio of the control signal to the resource increases and the 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.

The base station according to one aspect of the present disclosure includes a circuit for generating downlink control information (DCI) for resource allocation in a plurality of time units, and a transmission unit for transmitting the DCI. The first information for each of the plurality of time units and the second information for all of the plurality of time units are included, and the second information includes frequency resource allocation and MCS.

The communication method according to one aspect of the present disclosure includes a step of generating downlink control information (DCI) for resource allocation in a plurality of time units and a step of transmitting the DCI, and the DCI is the DCI. The first information for each of the plurality of time units and the second information for all of the plurality of time units are included, and the second information includes frequency resource allocation and MCS.

The integrated circuit according to one aspect of the present disclosure controls a process of generating downlink control information (DCI) for resource allocation in a plurality of time units and a process of transmitting the DCI, and the DCI is the DCI. The first information for each of the plurality of time units and the second information for all of the plurality of time units are included, and the second information includes frequency resource allocation and MCS.

It should be noted that these comprehensive or specific embodiments may be realized in a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium, and the system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium may be realized. It may be realized by any combination of.

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

Further advantages and effects in one aspect of the present disclosure will be apparent from the specification and drawings. Such advantages and / or effects are provided by some embodiments and the features described in the specification and drawings, respectively, but not all need to be provided in order to obtain one or more identical features. There is no.

Diagram showing an example of TTI length The figure provided for explaining the problem to be solved by one aspect of this disclosure. A block diagram showing a configuration of a main part of a base station according to the first embodiment. A block diagram showing a configuration of a main part of a terminal according to the first embodiment. Block diagram showing the configuration of the base station according to the first embodiment Block diagram showing the configuration of the terminal according to the first embodiment The figure which shows an example of the control information of DL included in DCI which concerns on Embodiment 1. The figure which shows the allocation example of DL which concerns on Embodiment 1. The figure which shows an example of the control information of UL included in DCI which concerns on Embodiment 1. The figure which shows the allocation example in the subframe N of UL in the case of supporting the non-adaptive retransmission and the Adaptive retransmission according to the first embodiment. The figure which shows the allocation example in the subframe N + X of UL in the case of supporting the non-adaptive retransmission and the Adaptive retransmission according to the first embodiment. The figure which shows the allocation example in the subframe N of UL in the case of supporting Adaptive retransmission which concerns on Embodiment 1. The figure which shows the allocation example in the subframe N + X of UL in the case of supporting Adaptive retransmission which concerns on Embodiment 1. Diagram showing the concept of PUCCH resources Diagram showing the concept of PUCCH resources when SRS is deployed The figure which shows the PUCCH resource which transmits the ACK / NACK signal in the case of 4TTI per subframe which concerns on Embodiment 2. The figure which shows the allocation example of DL which concerns on Embodiment 2. The figure which shows the allocation example of the ACK / NACK signal of UL which concerns on Embodiment 2. The figure which shows the PUCCH resource which transmits the ACK / NACK signal in the case of 14 TTI per subframe which concerns on Embodiment 2. Diagram showing an example of Spatial bundling Diagram showing an example of Time domain bundling The figure which shows the generation example of the ACK / NACK signal which concerns on the operation example 1 of Embodiment 2. The figure which shows the generation example of the ACK / NACK signal which concerns on the operation example 2 of Embodiment 2.

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

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

FIG. 3 is a block diagram showing a configuration of a main part of the base station 100 according to the embodiment of the present disclosure. In the base station 100 shown in FIG. 3, the PDCCH generation unit 103 has one Downlink Control Information (DCI) including control information for a plurality of first TTIs whose TTI length is shorter than that of the second TTI (Transmission Time Interval). Is generated, and the transmission unit 107 transmits DCI.

Further, FIG. 4 is a block diagram showing a configuration of a main part of the terminal 200 according to each embodiment of the present disclosure. In the terminal 200 shown in FIG. 4, the PDCCH receiving unit 207 provides one Downlink Control Information (DCI) including control information for a plurality of first TTIs whose TTI length is shorter than that of the second TTI (Transmission Time Interval). Upon reception, the signal separation unit 202 uses DCI to separate the downlink data signal from the received signal, and the signal allocation unit 210 uses DCI to allocate the uplink data signal to the uplink resource.

In DCI, the control information regarding the retransmission processing of the data signal is set for each of the plurality of first TTIs, and the control information regarding the processing other than the retransmission processing is set in common with the plurality of first TTIs.

(Embodiment 1)
[Base station configuration]
FIG. 5 is a block diagram showing the configuration of the base station 100 according to the present embodiment. In FIG. 5, the base station 100 includes a TTI determination unit 101, an MCS determination unit 102, a PDCCH (Physical Downlink Control Channel) generation unit 103, an error correction coding unit 104, a modulation unit 105, and a signal allocation unit 106. The transmission unit 107, the reception unit 108, the signal separation unit 109, the PUCCH (Physical Uplink Control Channel) reception unit 110, the demodulation unit 111, the error correction decoding unit 112, and the ACK / NACK determination unit 113. Have.

When allocating resources to a plurality of TTIs using one DCI, the TTI determination unit 101 determines which TTI to allocate the resources to among the plurality of TTIs. The TTI determination unit 101 outputs information (TTI information) indicating the presence / absence of allocation to each of the plurality of TTIs to the PDCCH generation unit 103.

Specifically, in the case of DL (downlink) allocation, the TTI determination unit 101 is input from the PUCCH receiving unit 110, the ACK / NACK signal mapped to the PUCCH and transmitted, or the error correction decoding unit 112. Based on the ACK / NACK signal that is multiplexed and transmitted to the UL (uplink) data signal, the TTI that needs to be retransmitted is determined, and the TTI to which the resource is allocated is determined based on the determination result. Further, the TTI determination unit 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 the allocation to other UEs, and determines the resource. Determine the TTI to allocate.

On the other hand, in the case of UL allocation, the TTI determination unit 101 determines the TTI that needs to be retransmitted based on the ACK / NACK signal for the UL data input from the ACK / NACK determination unit 113, and based on the determination result. Determine the TTI to which the resource will be allocated. Further, the TTI determination unit 101 allocates new data for each TTI in consideration of the amount of data obtained from the buffer status report of the UL data signal transmitted from the UE (not shown) and the allocation to other UEs. Determine and determine the TTI to allocate resources to.

The MCS determination unit 102 determines the MCS of the DL based on the ACK / NACK signal for the CQI information and the DL data signal input from the PUCCH reception unit 110. Further, the MCS determination unit 102 determines the UL MCS based on the reception quality of the SRS (Sounding Reference Signal) or UL data signal sent separately. The MCS determination unit 102 outputs information (MCS information) indicating the determined DL and UL MCS to the PDCCH generation unit 103. Further, the MCS determination unit 102 outputs the MCS of the DL to the error correction coding unit 104 and the modulation unit 105, and outputs the MCS of the UL to the demodulation unit 111 and the error determination decoding unit 112.

The PDCCH generation unit 103 generates a PDCCH or EPDCCH to which a plurality of TTIs are assigned. The PDCCH is placed in the first OFDM symbol (number of symbols: 1, 2 or 3) in the subframe, and the EPDCCH is placed in the OFDM symbol other than the OFDM symbol in which the PDCCH in the subframe is placed.

Specifically, the PDCCH generation unit 103 sets NDI (New Data Indicator) for the TTI that allocates DL and UL based on the TTI information input from the TTI determination unit 101. Further, in the case of DL allocation, the PDCCH generation unit 103 further sets the HARQ number (HARQ process number) and the Redandancy version for the TTI. Further, the PDCCH generation unit 103 generates DL and UL resource allocation information as information common to a plurality of TTIs. Then, the PDCCH generation unit 103 generates one DCI including the control information regarding the allocation to these TTIs and the TTI information. The PDCCH generation unit 103 generates PDCCH or EPDCCH using the MCS information input from the MCS determination unit 102, and outputs the PDCCH or EPDCCH to the signal allocation unit 106 and the signal separation unit 109.

The error correction coding unit 104 error-corrects and encodes the transmission data signal (DL data signal) or the signaling of the upper layer based on the MCS information of the DL input from the MCS determination unit 102, and modulates the coded signal. Output to 105.

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

The signal allocation unit 106 allocates a signal (including a data signal) received from the modulation unit 104 and a control signal (PDCCH or EPDCCH) received from the PDCCH generation unit 103 to a predetermined downlink resource. By assigning the control signal (PDCCH or EPDCCH) and the data signal (PDSCH) to a predetermined resource in this way, a transmission signal is formed. The formed transmission signal is output to the transmission unit 107.

The transmission unit 107 performs wireless transmission processing such as up-conversion on the transmission signal input from the signal allocation unit 106, and transmits the transmission signal to the terminal 200 via the antenna.

The receiving unit 108 receives the signal transmitted from the terminal 200 via the antenna, performs wireless reception processing such as down-conversion on the received signal, and outputs the received signal to the signal separation unit 109.

The signal separation unit 109 separates the UL data signal from the received signal and outputs it to the demodulation unit 111 based on the information input from the PDCCH generation unit 103, and the signal included in the PUCCH resource from the received signal (PUCCH signal. ACK). / NACK signal included) is separated and output to the PUCCH receiver 110.

The PUCCH receiving unit 110 extracts an ACK / NACK signal for the DL data signal from the PUCCH signal input from the signal separation unit 109, and outputs the ACK / NACK signal to the TTI determination unit 101 and the MCS determination unit 102. Further, the PUCCH receiving unit 110 extracts CQI information from the PUCCH signal input from the signal separating unit 109 and outputs it to the MCS determination unit 102.

The demodulation unit 111 performs demodulation processing on the signal input from the signal separation unit 109 based on the UL MCS information (modulation information) input from the MCS determination unit 102, and error-corrects and decodes the obtained signal. Output to unit 112.

The error correction decoding unit 112 decodes the signal input from the demodulation unit 111 based on the UL MCS information (error code information) input from the MCS determination unit 102, and the reception data signal (UL data) from the terminal 200. Signal). The error correction decoding unit 112 outputs the UL data signal to the ACK / NACK determination unit 113. Further, the error correction / decoding unit 112 extracts the ACK / NACK signal for the DL data signal, which is multiplexed and transmitted to the UL data signal, and outputs the ACK / NACK signal to the TTI determination unit 101.

The ACK / NACK determination unit 113 uses CRC (Cyclic Redundancy Check) for the UL data signal input from the error correction coding unit 112 to determine whether or not there is an error, and determines whether or not there is an error, and determines whether or not the determination result is UL. It is output to the TTI determination unit 101 as an ACK / NACK signal.

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

The receiving unit 201 receives the received signal via the antenna, performs reception processing such as down-conversion on the received signal, and then outputs the received signal to the signal separation unit 202.

The signal separation unit 202 separates a signal (PDCCH signal or EPDCCH signal) arranged in a resource to which PDCCH or EPDCCH may be assigned, and outputs the signal to the PDCCH reception unit 207. Further, the signal separation unit 202 separates the DL data signal from the reception signal based on the DL resource allocation information input from the PDCCH reception unit 207, and outputs the DL data signal to the demodulation unit 203. When resources for a plurality of TTIs are allocated by PDCCH or EPDCCH, the signal separation unit 202 outputs the DL data signal assigned to the same resource to the demodulation unit 203 in the plurality of TTIs to which the resources are allocated. do.

The demodulation unit 203 demodulates the signal received from the MCS information (modulation information) signal separation unit 202 of the DL input from the PDCCH reception unit 207, and outputs the demodulated signal to the error correction decoding unit 204.

The error correction decoding unit 204 decodes the demodulation signal received from the demodulation unit 203 based on the MCS information (error code information), NDI, HARQ number, and Redandancy version of the DL input from the PDCCH reception unit 207, and obtains the result. Output the received data signal. Further, the received data signal is output to the error determination unit 205.

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

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

The PDCCH receiving unit 207 receives the PDCCH signal or EPDCCH signal (that is, DCI) received from the signal separation unit 202, and if a plurality of TTIs are assigned in the DCI, NDI is extracted for each TTI. Further, the PDCCH receiving unit 207 extracts HARQ number and Redandancy version information for each TTI for the TTI to which the DL data resource is allocated. Further, the PDCCH receiving unit 207 extracts resource allocation information (DL resource allocation information, UL resource allocation information) and MCS information as information common to a plurality of TTIs, and outputs the DL resource allocation information to the signal separation unit 202. The UL resource allocation information is output to the signal allocation unit 210, the modulation information of the MCS information is output to the demodulation unit 203 and the modulation unit 209, and the error correction information and NDI of the MCS information are error-corrected and encoded. Output to unit 204 and error correction decoding unit 208. Further, the PDCCH receiving unit 207 outputs the HARQ number and the Redundancy version of the DL data to the error correction code unit 208.

The error correction coding unit 208 determines whether to newly allocate or retransmit the transmission data signal (UL data signal) based on the NDI input from the PDCCH reception unit 207. Further, the error correction coding unit 208 error-corrects and encodes the UL data signal based on the MCS information (error code information) input from the PDCCH receiving unit 207, and outputs the encoded data signal to the modulation unit 209. do.

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

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

The transmission unit 211 performs transmission processing such as up-conversion on the signal input from the signal allocation unit 210, and transmits the signal via the antenna.

[Operation of base station 100 and terminal 200]
The operation of the base station 100 and the terminal 200 having the above configuration will be described in detail.

In the present embodiment, when Latency reduction is performed, the base station 100 allocates resources to a plurality of TTIs using one DCI. At this time, the base station 100 includes a bit string (resource allocation) indicating the presence or absence of allocation for each of the plurality of TTIs in the one DCI, and notifies the terminal 200.

Here, if the shortening of the TTI length by Latency reduction increases the frequency of CQI reporting and shortens the delay from CQI measurement to reporting, the base station predicts quality close to the actual line quality. It has the advantage of being able to allocate resources and set MCS. However, if the frequency of CQI reporting is limited to a given period, such as every 10TTI or 5TTI, the base station will use the same CQI reporting for line quality until the CQI is updated. In anticipation, resource allocation and MCS settings will be performed. Therefore, under the above-mentioned restrictions, even if the frequency resources and MCS are the same for multiple TTIs during the period when the CQI is not updated, it is expected that the effect on the throughput reduction will be small.

Further, it can be expected that the followability of the outer loop control will be improved as the number of transmissions and receptions of the ACK / NACK signal increases due to the shortening of the TTI length. The outer loop control is a control in which the base station selects the MCS so that the target error rate is obtained according to the decryption determination result (ACK / NACK signal) of the packet reported by the UE. Therefore, shortening the TTI length and increasing the number of ACK / NACK signals per resource allocated to each of the plurality of TTIs is considered to be effective in improving the throughput.

In view of the above two points, shortening the TTI length is effective in improving the throughput by shortening the delay of CQI reporting and increasing the number of ACK / NACK signals, but the resource allocation and MCS settings are changed for each TTI. It is not considered necessary.

Therefore, in the present embodiment, the 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, the base station 100 sets control information (for example, frequency resource (PRB (Physical Resource Block)) and MCS) other than the control information related to the retransmission process in common to the plurality of TTIs.

By doing so, even when the 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 it is possible to reduce the overhead amount of DCI. Further, by notifying the control information for a plurality of TTIs with one DCI, the number of times the DCI is detected by the terminal 200 is reduced, so that the probability of the DCI detection error can be reduced.

Hereinafter, operation examples 1 and 2 according to the present embodiment will be described.

[Operation example 1: DL]
In this operation example, the base station 100 (PDCCH generation unit 103) notifies each TTI of the allocation of resources to a plurality of TTIs in one subframe of the DL as control information to be notified by one DCI. Add new TTI information (Resource allocation) indicating whether or not to allocate by.

For example, as TTI information, the base station 100 adds a bit string for the number of TTIs that can be assigned to one DCI at the same time. Each bit in the bit string corresponds to each of the TTIs that can be assigned to one DCI at the same time. For example, if a bit in the bit string is 1, it indicates that the corresponding TTI has an allocation, and if it is 0, it indicates that the corresponding TTI has no allocation. The terminal 200 specifies whether or not to allocate to each TTI based on the TTI information included in one DCI.

Further, the base station 100 standardizes the information that can be shared among the plurality of TTIs among the control information included in the conventional DCI, and individually sets the information that requires individual notification 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 contained in DCI also differs depending on the DCI format. FIG. 7 shows an example of control information (Common) commonly set in a plurality of TTIs designated by one DCI and control information set in individual TTIs (Each TTI) in this operation example.

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

In addition, the control information for UL included in the DCI of DL allocation 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 included in all DCI formats. The "Transport block to codeword swap flag" included in 2 / 2A is set individually for multiple TTIs, and control information regarding other DL allocations is set in common for multiple TTIs.

The Transport block to codeword swap flag is a parameter indicating the relationship between the codeword and the 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" is the opposite. The combination of transport block 1 and codeword 1 and transport block 2 and codeword 0 is shown. With the Transport block to codeword swap flag, the reception quality can be averaged between transport blocks by changing the combination of the transport block and codeword at the time of retransmission.

That is, the 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, the base station 100 uses one DCI to make allocations to a plurality of TTIs. At this time, the base station 100 sets the control information related to the retransmission process for each of the plurality of TTIs, while the other control information (for example, resource allocation, MCS, etc.) is set in common for the plurality of TTIs. By assigning the base station 100 to a plurality of TTIs using one DCI, the ratio of the control information (DCI) to the resources can be reduced as compared with the case where the DCIs are individually transmitted for each TTI.

Also, by allocating the same frequency resource to multiple 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 by one DCI at the same time is 4.

In FIG. 8, the resource allocation indicating whether or not the resource is allocated to each TTI is (0,1,1,0), the resource is allocated to the second and third TTIs, and the first and fourth TTIs are assigned. Indicates that no resources have been allocated.

As shown in FIG. 8, the base station 100 indicates the terminal 200 a common frequency resource for the two TTIs assigned by DCI on the frequency axis, while the HARQ number (HARQ process number). NDI and RV are specified for each TTI.

In DL, there are cases where CRS (Cell specific Reference Signal) is used and DMRS (Demodulation Reference signal) is used as the Reference signal used for DL data demodulation. In the case of CRS, terminal 200 demodulates data using CRS located in 1 subframe or 1 slot regardless of whether resources are allocated to TTI.

On the other hand, in the case of DMRS, the following two methods can be considered as the demodulation method in the terminal 200.

The first method is for the terminal 200 to demodulate the data using only the DMRS located in the resource-allocated TTI. In this case, when allocating a plurality of TTIs, the base station 100 must always include the TTI in which the DMRS is arranged. This method has the advantage that the amount of DMRS resources used in the terminal 200 is reduced, so that it is easy to allocate the resources of other UEs to other TTIs.

The second method is for the terminal 200 to demodulate data using DMRS in one subframe or one slot, regardless of whether the resource is a TTI allocated. In this method, when the base station 100 allocates a plurality of TTIs, the DMRS that can be used in the terminal 200 does not change regardless of which TTI the resource is allocated to, so that the demodulation accuracy in the terminal 200 can be ensured. However, it is necessary to limit the antenna port of DMRS that can be used when allocating a plurality of terminals 200 to different TTIs, or to limit the allocation of TTIs to terminals 200 that can commonly use DMRS.

[Operation example 2: UL]
In this operation example, as in the case of DL, the base station 100 (PDCCH generation unit 103) notifies each TTI of resources for a plurality of TTIs in one subframe of UL as control information to be notified by one DCI. TTI information (Resource allocation) indicating whether or not to allocate by DCI is newly added to.

For example, as TTI information, the base station 100 adds a bit string for the number of TTIs that can be assigned to one DCI at the same time, as in the case of DL. Each bit in the bit string corresponds to each of the TTIs that can be assigned to one DCI at the same time. For example, if a bit in the bit string is 1, it indicates that the corresponding TTI has an allocation, and if it is 0, it indicates that the corresponding TTI has no allocation. The terminal 200 specifies whether or not to allocate to each TTI based on the TTI information included in one DCI.

FIG. 9 shows an example of control information (Common) commonly set in a plurality of TTIs designated by one DCI and control information set in individual TTIs (Each TTI) in this operation example. Since there are two types of DCI formats that instruct UL data allocation, DCI format 0 and DCI format 4, FIG. 9 shows an example when there are two types of DCI formats.

In UL allocation, unlike DL, there is no notification of HARQ process number and Redundancy version (RV), and HARQ process number and Redundancy version (RV) are set according to the predetermined rules between the base station 100 and the terminal 200. Change. Therefore, in UL allocation, only the New data indicator (NDI) is sent individually to multiple TTIs, and control information about other UL assignments is sent in common by multiple TTIs. That is, the control information regarding the retransmission process for the UL data signal is NDI.

In this way, the base station 100 uses one DCI to make allocations to a plurality of TTIs. At this time, the base station 100 sets the control signal (NDI) related to the retransmission processing for each of the plurality of TTIs, while setting other control information (for example, resource allocation, MCS, etc.) in common among the plurality of TTIs. By assigning the base station 100 to a plurality of TTIs using one DCI, the ratio of the control information (DCI) to the resources can be reduced as compared with the case where the DCIs are individually transmitted for each TTI.

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

Also, in UL, the UE transmits a retransmission signal using the TTI with the same HARQ number. However, as described above, since DCI does not include the notification of the HARQ number, the TTI corresponding to the signal of the same HARQ number is sequentially determined according to the predetermined rules. For example, in a conventional FDD that does not apply Latency reduction, the HARQ number is 8. Therefore, since the same HARQ number is used for every 8 TTI, the UE can retransmit the signal every 8 TTI.

At 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 by DCI (NDI), allocates resources by DCI each time it is retransmitted, and newly notifies MCS and the like. For allocations other than SPS (Semi Persistent Scheduling), the UE determines whether it is a retransmission or a new data allocation depending on the value of NDI. Specifically, at a certain HARQ number, if the NDI notified by DCI is the same as the NDI included in the DCI that indicated the UL data signal of the same HARQ number last time (Non toggle), the UE is retransmitted. Judging, if the NDI is different from the previous NDI (Toggle), the UE determines that it is a new data allocation. 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 TTI after 8 TTI without instructing retransmission after 8 TTI.

Non-Adaptive retransmission is a retransmission method in which the base station instructs the UE to retransmit only with the ACK / NACK signal indicated by PHICH (Physical HARQ Indicator Channel) and does not transmit DCI. In non-adaptive retransmission, the UE determines the presence or absence of retransmission according to PHICH. Specifically, in FDD, when NACK is notified by PHICH from the base station by DL after 4 TTI of UL data signal transmission, UE is TTI of the same HARQ number after 4 TTI and the same frequency as the previous transmission. Send a retransmission signal with resources and MCS. Also, if ACK is notified by PHICH and the UE does not detect DCI, the UE does not send the UL data signal with the corresponding HARQ number, but keeps the previously transmitted signal in the buffer and sends it to Adaptive retransmission. Be prepared.

In this operation example, when allocating multiple TTIs 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 supporting Non-adaptive retransmission and Adaptive retransmission]
10A and 10B show examples that support both non-adaptive and adaptive retransmissions. In FIGS. 10A and 10B, the number of TTIs per subframe is 4, and the number of TTIs that can be assigned by one DCI at the same time is 4. Further, in FIGS. 10A and 10B, the HARQ numbers are sequentially assigned to each TTI, and it is stipulated that the same HARQ number is assigned after the X subframe.

In the subframe N shown in FIG. 10A, the resource allocation indicating the resource allocation to the TTI is (1,1,1,0), new data is assigned to the first, second, and third TTIs, and 4 No data has been assigned to the second TTI. For new data assigned to each TTI, frequency resource allocation (PRB) and MCS (MCS = 6) are set in common among 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, the subframe having the same HARQ number as subframe N) after the X subframe shown in FIG. 10B, HARQ # 0 is Adaptive retransmission, HARQ # 1 is Non-adaptive retransmission, and HARQ # Suppose a few 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 available (1). .. Further, in FIG. 10B, the NDI for the 1st TTI of HARQ # 0 is Non-toggle, indicating the allocation of retransmission data, and the NDI for the 3rd TTI of HARQ # 2 and the 4th TTI of HARQ # 3 is Toggle, which is new data. Indicates the assignment. The same frequency resource is assigned to the 1st TTI, 3rd TII, and 4th TTI of HARQ # 0, 2, 3 assigned by one DCI, and the same MCS (MCS = 7) is set.

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

As described above, the base station 100 transmits the PHICH including the ACK / NACK signal for the UL data signal assigned by the TTI that performs non-adaptive retransmission among the plurality of TTIs, and is assigned by the TTI that performs Adaptive retransmission. Send a DCI containing NDI for UL data signals. That is, the base station 100 does not include the allocation for the TTI that performs the non-adaptive retransmission in the DCI. Then, the terminal 200 performs a retransmission process based on PHICH in the TTI that performs non-adaptive retransmission, and performs a retransmission process based on the NDI in the TTI that performs Adaptive retransmission.

In this way, non-adaptive retransmission does not allocate to TTI using one DCI, so in subframes including TTI where non-adaptive retransmission is performed, new UL data allocation or Adaptive retransmission is performed in other TTIs. No DCI will be 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 allocation in DCI.

[When only Adaptive retransmission is supported]
11A and 11B show examples that support only Adaptive retransmissions. In FIGS. 11A and 11B, the number of TTIs per subframe is 4, and the number of TTIs that can be assigned by one DCI at the same time is 4. Further, in FIGS. 11A and 11B, the HARQ numbers are sequentially assigned to each TTI, and it is stipulated that the same HARQ number is assigned after the X subframe.

In the subframe N shown in FIG. 11A, the resource allocation indicating the resource allocation to the TTI is (1,1,1,0) as in FIG. 10A, and new data is allocated to the first, second, and third TTIs. No data has been assigned to the 4th TTI.

In subframe N + X (that is, the subframe whose HARQ number is the same as subframe N) after the X subframe shown in FIG. 11B, HARQ # 0 and # 1 are Adaptive retransmissions, and HARQ # 2 and 3 are new data allocations. 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, # 3 for Adaptive retransmission are assigned. Yes (1). Further, in FIG. 11B, the NDI for the 1st TTI of HARQ # 0 and the 2nd TTI of HARQ # 1 is Non-toggle, indicating the allocation of retransmission data, and the NDI for the 3rd TTI of HARQ # 2 and the 4th TTI of HARQ # 3 is Toggle. Indicates a new data allocation. The same frequency resource is assigned to HARQ # 0, 1,2,3 1st TTI, 2nd ^TTI , 3rd ^TII , and 4th ^TTI assigned by one DCI, and the same MCS (MCS =). 7) is set.

As described above, the base station 100 transmits the DCI including the NDI for the UL data signals assigned by the plurality of TTIs that perform Adaptive retransmission, but does not transmit the PHICH. This has the advantage that PHICH resources are not required if only Adaptive retransmission is supported. If any one of the TTIs in one subframe has Adaptive retransmission or new data allocation, the base station 100 transmits DCI in the subframe, but the allocation of retransmission data can also be notified by the same DCI. PHICH is not required. That is, a method that supports only Adaptive retransmission that does not require PHICH is effective in reducing overhead.

Also, when only Adaptive retransmission is supported, the frequency allocation and MCS within 1 subframe are common between TTIs. Having a common frequency resource has the advantage that the reference signal can be shared between TTIs and that it is less likely to collide with the data allocation of other UEs. In particular, since the data allocation of the conventional UE is performed in units of subframes or slots, if the frequency resources are available in the subframe or in the slots, there is an advantage that collisions are unlikely to occur when allocating the data resources of the conventional UE. There is.

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

The operation example 1 and the operation example 2 have been described above.

In this way, in the present embodiment, the base station 100 generates one DCI including the control information for the plurality of shortened TTIs and transmits it to the terminal 200. Further, in DCI, the control information regarding the retransmission processing of the DL / UL data signal is set for each of the plurality of shortened TTIs, and the control information other than the control information regarding the retransmission processing is assigned in common to the plurality of shortened TTIs.

As a result, Latency reduction is applied, and even when shortened TTI is used, the increase in the ratio of DCI to the total resources can be suppressed. Therefore, according to the present embodiment, resources can be efficiently used even when the TTI length is shortened.

Further, in the present embodiment, when the TTI length is shortened, the resource allocation for the TTI arranged in one subframe is included in one DCI. As a result, the same reference signal can be shared by TTIs contained in the same subframe. Therefore, since the reference signal does not need to be arranged for each TTI, it is possible to prevent a decrease in resources that can be allocated to data and prevent a decrease in throughput. Furthermore, in Latency reduction, the allocation of TTI in subframe units is notified by DCI, which facilitates scheduling with UEs to which Latency reduction is not applied (that is, UEs to which resources are allocated in subframe units). Become.

Further, according to the present embodiment, the DCI includes information (Resource allocation) indicating the presence or absence of allocation for each of the plurality of shortened TTIs. As a result, the terminal 200 can specify whether or not to allocate to a plurality of TTIs when the DCI can be correctly received. For example, when multiple TTIs are notified by individual DCIs, there may be a situation where the UE cannot detect the DCI even though the base station has transmitted the DCI. In the form of, misdetection can be avoided.

Although the HARQ number is shown in the present embodiment, the HARQ number is counted by the base station 100 and the terminal 200, respectively, and is not necessarily a common value. In addition, the number of HARQ numbers is specified, and by counting up the HARQ numbers to Cyclic for each TTI in the base station 100 and the terminal 200, the same HARQ process can be used between the base station 100 and the terminal 200. You can recognize that there is.

Further, in the present embodiment, it is premised that the HARQ number is not notified by DCI in UL and the HARQ process is the same between the base station 100 and the terminal 200, but the UL is also the same as the DL. The HARQ number may be notified to. In this case, as with DL, the HARQ number is set individually for multiple UL TTIs in DCI.

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

Further, the DCI to which a plurality of TTIs are assigned may be arranged only in the PDCCH and may not be arranged in the EPDCCH. Since the PDCCH is placed at the head of the subframe, the time when the terminal 200 can complete the reception of DCI can be shortened. On the other hand, since EPDCCH is arranged up to the last OFDM symbol of the subframe, there is a feature that the terminal 200 can complete the reception of DCI for a long time. Therefore, by arranging the DCI in the PDCCH, the base station 100 completes the reception of the DCI at the terminal 200 early, and in the latency reduction, the terminal 200 feeds back the ACK / NACK signal to the DL data or the UL data signal. There is an advantage that the preparation period until transmission can be secured.

Conversely, a DCI that assigns multiple TTIs may be located only on the EPDCCH and not on the PDCCH. Since PDCCH is placed at the beginning of the subframe, the amount of resources is limited. A DCI that indicates multiple TTIs has a larger amount of information and a longer code length than a DCI that indicates only one TTI. On the other hand, EPDCCH has a feature that the adjustment of the resource amount is simpler than that of PDCCH because the resource can be increased in the frequency direction. Therefore, the base station 100 can prevent the resource tightness of the PDCCH by arranging the DCI to which the plurality of TTIs are assigned only in the EPDCCH.

In addition, although the resource in which the DCI is placed is PDCCH or EPDCCH, it may be New PDCCH newly set for Latency reduction.

(Embodiment 2)
In this embodiment, a method of transmitting an ACK / NACK signal to a DL data signal assigned to a plurality of TTIs in one subframe when Latency reduction is applied will be described.

Since the base station and the terminal according to the present embodiment have the same basic configuration as the base station 100 and the terminal 200 according to the first embodiment, FIGS. 5 and 6 will be referred to and described.

When multiple TTI DL data signals are assigned per subframe, an ACK / NACK signal for the DL data signal is generated for each TTI. Further, since the ACK / NACK signal is set for each code word, when a DL data signal is assigned, one or two ACK / NACK signals are generated per TTI.

Here, as described in the first embodiment, it is assumed that the base station 100 notifies the terminal 200 of the allocation of a plurality of TTIs using one DCI. In this case, the PUCCH resource used for transmitting the ACK / NACK signal may 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. This has the advantage that even if Latency reduction is applied, there is no need to specify the location of the PUCCH resource.

[PUCCH resource description]
The format of the PUCCH resource used to transmit the ACK / NACK signal depends on the number of bits in the ACK / NACK signal.

If the ACK / NACK signal is 1 bit, PUCCH format 1a is used, and if the ACK / NACK signal is 2 bits, PUCCH format 1b is used. If the ACK / NACK signal has 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. If it is instructed that PUCCH format 3 is used in the upper layer, PUCCH format 3 is used.

In addition, Frequency hopping is applied to the transmission of PUCCH, 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 in PUCCH format 1a / 1b.

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

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

Hereinafter, operation examples 1 and 2 according to the present embodiment will be described.

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

However, the terminal 200 limits the position where the ACK / NACK signal is arranged for each TTI. For example, in UL, the terminal 200 assigns ACK / NACK signals to DL data signals in the order assigned by TTI of DL. That is, the ACK / NACK signal for the DL data signal transmitted by the TTI at the earlier time among the plurality of TTIs is allocated to the resource at the earlier time among the PUCCH resources. As a result, the base station 100 can reduce the delay amount of the ACK / NACK signal when receiving the ACK / NACK signal for the DL data signals transmitted by the plurality of TTIs.

Further, in this operation example, the Reference signal placed in the slot is shared between the TTIs transmitted in the same slot.

<For 2TTI per subframe>
The 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 even in UL, and ACK / NACK of the DL data signal assigned to the 2nd slot in DL. Even in UL, the signal is transmitted only in the 2nd slot of the PUCCH resource.

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

In this way, the PUCCH resource of the terminal 200 to which Latency reduction is applied has no frequency hopping gain, but is encoded by the same Orthogonal sequences as the conventional UE, so that the orthogonality with the conventional PUCCH resource is maintained and at the same time. It has the advantage of being able to be assigned.

<For 4TTI per subframe>
FIG. 13 shows the allocation of PUCCH resources (SC-FDMA symbols) that transmit ACK / NACK signals to DL data signals assigned to TTIs in subframes in DL in the case of 4 TTIs per subframe.

As shown in FIG. 13, the UL 1st slot is common to the ACK / NACK signals corresponding to the 1st TTI and the 2nd TTI, and the UL 2nd ^slot is common to the ACK / NACK signals corresponding to the 3rd TTI and the 4th TTI. And. Further, as shown in FIG. 13, since the number of SC-FDMA symbols that transmit the ACK / NACK signal corresponding to each TTI is 2, the code length of the Orthogonal sequences is 2. For example, let Sequence index # 0 be the sign [+1 +1] and Sequence index # 1 be [+1 -1]. The Reference signal is placed in SC-FDMA # 2,3,4, and the code length of the Orthogonal sequences is 3.

14A and 14B show an operation example in the case of 4 TTI 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, the terminal 200 transmits an ACK / NACK signal for the DL data signal assigned by the 2nd TTI of the DL by SC-FDMA # 5 and 6 of the 1st slot of the UL. At that time, the terminal 200 transmits the Reference signal for the 2nd TTI by SC-FDMA # 2, 3 and 4 of the 1st slot.

Further, in FIG. 14B, the terminal 200 transmits the ACK / NACK signal for the DL data signal assigned by the 3rd TT of the DL by SC-FDMA # 0,1 of the 2nd slot of the UL and assigns it by the 4th TTI of the DL. The ACK / NACK signal for the DL data signal is transmitted by SC-FDMA # 5 and 6 in the 2nd slot of UL. At that time, the terminal 200 transmits a reference signal for the 3rd TTI and the 4th TTI with SC-FDMA # 2, 3, and 4 of the 2nd slot. In other words, the Reference signal is shared between the 3rd TTI and the 4th TTI.

When the final SC-FDMA symbol (SC-FDMA # 6) of the 2nd slot of UL is secured in SRS, the symbol that can transmit the ACK / NACK signal of 4th TTI is 1 symbol (SC-FDMA # 5). In this case, as a method of transmitting the ACK / NACK signal, a method of transmitting the ACK / NACK signal with only one symbol and a method of bundling or multiplexing the 3rd TTI ACK / NACK signal and the 4th TTI ACK / NACK signal are transmitted. 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 the amount of information is reduced. In addition, Multiplexing is a method in which each ACK / NACK signal is 1 bit, and is combined (multiplexed) into 2 bits and transmitted in Format 1b.

The method of transmitting the ACK / NACK signal with only one symbol has an advantage that the delay time of the ACK / NACK signal of the 3rd TTI does not have to be extended, although the reception quality of the ACK / NACK signal of the 4th TTI deteriorates.

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

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

FIG. 15 shows the allocation of PUCCH resources (SC-FDMA symbols) that transmit ACK / NACK signals to DL data signals assigned to TTIs in subframes in DL in the case of 14 TTIs per subframe.

When DL data is assigned to a plurality of TTIs, the terminal 200 bundles or multiplexes the ACK / NACK signal, and sets the number of SC-FDMA symbols to transmit the ACK / NACK signal to 2. Therefore, the code length of the Orthogonal sequences of the ACK / NACK signal of each TTI is 2 per subframe, as in the case of 4TTI. The Reference signal is placed in SC-FDMA # 2,3,4, and the code length of the Orthogonal sequences is 3.

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

As a method of applying bundled 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, the terminal 200 does not apply bundled and multiplexing and ACKs each codeword. Alternatively, the signal corresponding to NACK is transmitted by BPSK or QPSK.

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

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

On the other hand, when the number of ACK / NACK bits after Spatial bundling is 3 or 4, the terminal 200 further bundles the ACK / NACK signal between the TTIs. As the Bundling method, for example, the method used at the time of Carrier aggregation of TDD (see FIG. 17) is followed. By this Bundling, the number of bits of the ACK / NACK signal is compressed to 2 bits.

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

In the case where the ACK / NACK signal is transmitted with SC-FDMA symbols # 0 and 1 in the 1st slot shown in FIG. 18, DL data signals are assigned to the two TTIs, the 1st TTI and the 2nd TTI, and the number of codewords for each is the same. It is 1 and the total number of codewords is 2.

Further, in the case where the ACK / NACK signal is transmitted by the SC-FDMA symbols # 5 and 6 of the 2nd slot shown in FIG. 18, the DL data signal is assigned to one TTI of the 12th TTI, and 2 codewords are transmitted by MIMO transmission. Assigned.

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

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

In the case where the ACK / NACK signal is transmitted with SC-FDMA symbols # 0 and 1 in the 2nd slot shown in FIG. 18, DL data signals are assigned to the four TTIs of 8th TTI, 9th TTI, 10th TTI, and 11th TTI. Two codewords are assigned to MIMO transmission in each TTI. Therefore, the total number of codewords is eight. In this case, the terminal 200 first Spatial Bundling the ACK / NACK signal in each TTI according to FIG. 16, and then Time domain Bundling (4 to 2 bundling) the ACK / NACK signal between the TTIs 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 this operation example, since the method of allocating a plurality of TTIs described in the first embodiment is premised, if the terminal 200 can correctly receive the DCI, all the DL data allocations of the TTIs in the same subframe are performed. Can be received correctly. Therefore, the terminal 200 does not mistake the total number of codewords. This point also has the advantage of the first embodiment. Therefore, the terminal 200 can perform Bundling or multiplexing only on the TTI in which the data allocation has occurred, and compress and transmit the ACK / NACK signal.

[Operation example 2]
In this operation example, the terminal 200 Bundling or multiplexing the ACK / NACK signal generated for each TTI and arranges the ACK / NACK signal in one subframe of the UL over the resource for ACK / NACK.

This can support PUCCH frequency hopping.

Further, in this operation example, the 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 traditional UEs.

For example, if PUCCH format 1a / 1b is used and PUCCH format 3 is not used, the terminal 200 compresses all TTI ACK / NACK signals to 2 bits. The compression method is the same as in Operation Example 1 of the present embodiment, in which ACK / NACK signals of a plurality of codewords are spatially bundled in the TTI, and then time domain bundling is performed between the TTIs (see FIGS. 16 and 17).

When the number of assigned TTIs per subframe is 2, the ACK / NACK signal can be compressed to 2 bits by Spatial bundling, so the Time domain bundling between TTIs becomes unnecessary.

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

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

Further, when transmission in PUCCH format 3 is permitted by the signal of the upper layer, the terminal 200 can transmit a plurality of ACK / NACK signals using PUCCH format 3. In this case, since the terminal 200 can transmit the ACK / NACK signal without compressing it, there is an advantage that the amount of information of the ACK / NACK signal does not decrease.

In this embodiment, the case where the ACK / NACK signal is transmitted by the PUCCH resource has been described. However, when the UL data signal is assigned to the subframe and TTI for transmitting the PUCCH, the ACK / NACK signal is UL. There is also a method of transmitting on a data signal. In this case, if any one of the plurality of UL TTIs is assigned a UL data signal, the terminal 200 carries a plurality of ACK / NACK signals corresponding to the DL TTI on the TTI and transmits the TTI. You may. By doing so, the PUCCH format and the PUSCH format are not mixed in the UL subframe, and the terminal 200 has an advantage that the subframe can be transmitted in one format.

The operation example 1 and the operation example 2 have been described above.

As described above, in the present embodiment, when the terminal 200 transmits the ACK / NACK signal for the DL data signal transmitted by the shortened TTI by the PUCCH resource, the terminal 200 corresponds to the TTI of the earlier time among the plurality of shortened TTIs. The ACK / NACK signal to be used is placed in the resource (SC-FDMA symbol) of the earlier time among the PUCCH resources. By doing so, the ACK / NACK signal corresponding to the earlier TTI among the plurality of 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 the slot is shared with respect to the TTI corresponding to the ACK / NACK signal arranged in one slot. This eliminates the need to place a Reference signal for each TTI.

In the present embodiment, it is assumed that the base station 100 notifies the terminal 200 of the allocation of a plurality of TTIs by using one DCI in the same manner as in the first embodiment. However, in the present embodiment, the method of notifying the allocation of a plurality of TTIs is not limited to the method described in the first embodiment, and other methods may be used. The method of the present embodiment can also be applied to, for example, when a DL data signal is assigned by DCI for each TTI without assuming the method of allocating a plurality of TTIs of the first embodiment. In this case, among the plurality of TTIs, there may be a TTI in which the terminal 200 cannot detect the DCI even though the base station 100 transmits the DCI. In this case, the base station 100 can specify the TTI to be the target of the Bundling or multiplexing by adding the information of the assigned number of TTIs to the DCI. As a result, when the base station 100 and the terminal 200 can identify the TTI that the terminal 200 could not detect, the base station 100 and the terminal 200 can be treated as a DTX in the same manner as the NACK.

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

The embodiments of the present disclosure have been described above.

In the above embodiment, the 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 realized by software in cooperation with hardware.

Further, each functional block used in the description of the above embodiment is typically realized as an LSI which is an integrated circuit. The integrated circuit may control each functional block used in the description of the above embodiment and may include an input and an output. These may be individually integrated into one chip, or may be integrated into one chip so as to include a part or all of them. Although it is referred to as LSI here, it may be referred to as IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.

Further, the method of making an integrated circuit is not limited to the 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 connection and settings of the circuit cells inside the LSI may be used.

Furthermore, if an integrated circuit technology that replaces an LSI appears due to advances in semiconductor technology or another technology derived from it, it is naturally possible to integrate functional blocks using that technology. The application of biotechnology may be possible.

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

In the base stations of the present disclosure, the DCI contains information indicating the presence or absence of allocation to each of the plurality of first TTIs.

In the base station of the present disclosure, in DCI, the control information regarding the retransmission process for the downlink data signal is the HARQ process number, New Data Indicator (NDI), Redundancy Version (RV), or a plurality of transport blocks and codewords. It is information which shows the combination of.

In the base station of the present disclosure, in DCI, the control information regarding the retransmission process for the uplink data signal is the New Data Indicator (NDI).

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

In the base station of the present disclosure, the transmitting unit transmits DCI including NDI for the uplink data signals assigned by the plurality of first TTIs that perform Adaptive retransmission, and the transmitting unit transmits PHICH (Physical HARQ Indicator Channel). do not do.

In the base station of the present disclosure, a plurality of first TTIs are arranged in one subframe.

In the base station of the present disclosure, a plurality of first TTIs are arranged in one slot.

The base station of the present disclosure further comprises a receiving unit for receiving an ACK / NACK signal with respect to the downlink data signal transmitted by the first TTI, and is transmitted at the earlier TTI in the first TTI. The ACK / NACK signal for the downlink data signal is allocated to the resource at the earlier time among the uplink resources.

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

In the base station of the present disclosure, a receiving unit for receiving an ACK / NACK signal for a downlink data signal transmitted by the first TTI is further provided, and the ACK / NACK signal corresponding to the first TTI is Bundling or It is multiplexed and distributed over the resources for ACK / NACK in one subframe.

The 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 whose TTI length is shorter than that of the second TTI (Transmission Time Interval), and the DCI. A signal separation unit that separates the downlink data signal from the received signal and a signal allocation unit that allocates the uplink data signal to the uplink resource using the DCI are provided, and the data signal retransmission processing is performed in the DCI. The control information regarding the plurality of first TTIs is set for each of the plurality of first TTIs, and the frequency resource and the control information regarding the MCS (Modulation and coding scheme) are commonly set for the plurality of first TTIs, and DMRS (Demodulation Reference). signal) is arranged in the plurality of first TTIs.

The communication method of the present disclosure generates one Downlink Control Information (DCI) including control information for a plurality of first TTIs whose TTI length is shorter than that of the second TTI (Transmission Time Interval), and transmits the DCI. However, in the DCI, the control information regarding the data signal retransmission processing is set for each of the plurality of first TTIs, and the frequency resource and the control information regarding the MCS (Modulation and coding scheme) are the plurality of first TTIs. Commonly set for TTI, DMRS (Demodulation Reference signal) is arranged in 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 whose TTI length is shorter than that of the second TTI (Transmission Time Interval), and uses the DCI. The downlink data signal is separated from the received signal, the uplink data signal is assigned to the uplink resource using the DCI, and the control information regarding the data signal retransmission processing in the DCI is for each of the plurality of first TTIs. The frequency resources and control information related to the MCS (Modulation and coding scheme) are set in common to the plurality of first TTIs, and the DMRS (Demodulation Reference signal) is arranged in 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 Receiver unit 109,202 Signal separation unit 110 PUCCH receiver 111, 203 Demodulation unit 112, 204 Error correction decoding unit 113 ACK / NACK judgment unit 200 Terminal 205 Error judgment unit 206 ACK / NACK generation unit 207 PDCCH receiver

Claims (9)

A circuit that generates downlink control information (DCI) for resource allocation in a plurality of time units, which is a time unit for transmitting and receiving data, which is shorter than one subframe.
The transmitter that transmits the DCI and
Equipped with
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.
base station. The DCI contains information indicating whether or not resources are allocated to each of the plurality of time units.
The base station according to claim 1. The first information includes HARQ process number, New Data Indicator (NDI), Redundancy Version (RV), or information indicating a combination of a plurality of transport blocks and codewords.
The base station according to claim 1 or 2. The DCI is used for resource allocation of uplink data in the plurality of time units.
The base station according to any one of claims 1 to 3. The plurality of time units are included in one subframe.
The base station according to any one of claims 1 to 3. The plurality of time units are included in one slot.
The base station according to any one of claims 1 to 3. Each of the plurality of time units is shorter than one slot.
The base station according to any one of claims 1 to 3. A process of generating downlink control information (DCI) for resource allocation in a plurality of the time units, which is a time unit for transmitting and receiving data, which is shorter than one subframe.
The process of transmitting the DCI and
Equipped with
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 generating downlink control information (DCI) for resource allocation in a plurality of time units, which is a time unit for transmitting and receiving data, which is shorter than one subframe.
The process of transmitting the DCI and
Control 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.
Integrated circuit.

Images