JP7341298B2 - Base stations, communication methods and integrated circuits - Google Patents

Description

The present disclosure relates to a base station, a terminal, and a communication method.

In recent years, consideration has been given to realizing applications that require shortened delay times (delay critical). Examples of applications that require reduced latency include self-driving cars, hyper-reality applications in smart glasses, and communication between devices.

In order to realize these applications, 3GPP is considering latency reduction to reduce packet delay (see Non-Patent Document 1). Latency reduction considers shortening the TTI (Transmission Time Interval) length, which is a 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 equal to a unit called a subframe. 1 subframe consists of 2 slots (1 slot is 0.5msec). 1 slot 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 case of normal CP. When the TTI length is 0.5 msec (=1 slot), 2 TTIs are placed per 1 msec. Furthermore, when dividing 1 slot into a TTI of 4 OFDM symbols and a TTI of 3 OFDM symbols, 4 TTIs are arranged per 1 msec. Furthermore, when the TTI length is 1 OFDM symbol, 14 TTIs are arranged 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, which has the advantage of reducing the discrepancy between CQI reporting and 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, it is conceivable that the length of short TTI (sTTI) is different between DL (Downlink) and UL (Uplink). However, in conventional LTE/LTE-advanced, DL and UL have the same TTI length, and the timings of data allocation, data transmission, and feedback are commonly defined based on the same TTI length. Therefore, it is necessary to newly define the timing of data allocation, data transmission/reception, and feedback when the DL and UL sTTI lengths are different.

One aspect of the present disclosure is to provide a base station, a terminal, and a communication method that can appropriately set the timing of data allocation, data transmission/reception, and feedback when DL and UL have different sTTI lengths.

A base station according to an aspect of the present disclosure includes a transmitting unit that transmits a downlink signal using a first sTTI (short TTI) of a downlink that has a TTI length shorter than a TTI (Transmission Time Interval); a receiving unit that receives an uplink signal using a second sTTI of an uplink whose length is shortened, and when the length of the first sTTI is shorter than the second sTTI, the receiving unit transmits the downlink signal. From the timing, the uplink signal is received at the second sTTI after a predetermined interval set based on the length of the first sTTI.

A terminal according to an aspect of the present disclosure includes a receiving unit that receives a downlink signal using a first sTTI (short TTI) of a downlink that has a TTI length shorter than a TTI (Transmission Time Interval); a transmission unit that transmits an uplink signal using a second sTTI of an uplink that is shortened, and when the length of the first sTTI is shorter than the second sTTI, the transmission unit transmits the reception timing of the downlink signal. Then, the uplink signal is transmitted at the second sTTI after the predetermined interval, which is set based on the length of the first sTTI.

A communication method according to an aspect of the present disclosure transmits a downlink signal using a first sTTI (short TTI) of a downlink, which has a TTI length shorter than a TTI (Transmission Time Interval), and has a TTI length shorter than the TTI. If the uplink signal is received using the second sTTI of the uplink, and the length of the first sTTI is shorter than the second sTTI, the uplink signal is transmitted using the second sTTI of the downlink signal. The second sTTI is received after the predetermined interval, which is set as a reference.

A communication method according to an aspect of the present disclosure receives a downlink signal using a first sTTI (short TTI) of a downlink link, which has a TTI length shorter than a TTI (Transmission Time Interval), and has a TTI length shorter than the TTI. If the uplink signal is transmitted using the second sTTI of the uplink, and the length of the first sTTI is shorter than the second sTTI, the uplink signal is transmitted using the second sTTI of the uplink. The second sTTI is transmitted after the predetermined interval that is set as a reference.

Note that these comprehensive or specific aspects may be realized by a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium. It may be realized by any combination of the following.

According to one aspect of the present disclosure, it is possible to appropriately set the timing of data allocation, data transmission/reception, and feedback when DL and UL have different sTTI lengths.

Further advantages and advantages of one aspect of the disclosure will become apparent from the specification and drawings. Such advantages and/or effects may be provided by each of the several embodiments and features described in the specification and drawings, but not necessarily all are provided in order to obtain one or more of the same features. There isn't.

Diagram showing an example of TTI length Block diagram showing the main part configuration of a base station according to Embodiment 1 Block diagram showing the main part configuration of a terminal according to Embodiment 1 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 Diagram showing an example of transmission/reception timing during UL data allocation according to Embodiment 1 (operation example 1-1) Diagram showing an example of transmission/reception timing during UL data allocation according to Embodiment 1 (operation example 1-2) A diagram showing another example of transmission/reception timing during UL data allocation according to Embodiment 1 (operation example 1-2) Diagram showing an example of transmission/reception timing during UL data allocation according to Embodiment 1 (operation example 1-3) A diagram showing another example of transmission/reception timing during UL data allocation according to Embodiment 1 (operation example 1-3) Diagram showing an example of transmission/reception timing during DL data allocation according to Embodiment 1 (operation example 2-1) Diagram showing an example of transmission/reception timing during DL data allocation according to Embodiment 1 (operation example 2-2) A diagram showing another example of transmission/reception timing during DL data allocation according to Embodiment 1 (operation example 2-2) A diagram showing another example of transmission/reception timing during DL data allocation according to Embodiment 1 (operation example 2-2) A diagram showing another example of transmission/reception timing when DL data is allocated according to Embodiment 1 (operation example 2-3) A diagram showing an example of transmission and reception timing during UL data allocation according to Embodiment 2 A diagram showing another example of transmission/reception timing when DL data is allocated according to Embodiment 2 A diagram showing an example of transmission/reception timing during UL data allocation according to Embodiment 3 A diagram showing another example of transmission/reception timing when UL data is allocated according to Embodiment 3 A diagram showing an example of transmission and reception timing when UL data is allocated according to Embodiment 4

[Circumstances leading to one aspect of the present disclosure]
3GPP uses OFDM for DL and single carrier transmission for UL.

In order to maintain single carrier transmission in UL, a reference signal (DMRS: demodulation reference signal) and a data signal (PUSCH: Physical Uplink Shared Channel) cannot be placed in the same symbol, and the overhead of the reference signal becomes large. There is. Furthermore, in UL, since a terminal (UE: User Equipment) transmits a signal, the transmission power per time unit is lower than in DL, in which a base station (eNB) transmits a signal. Therefore, in UL, the UE needs to spread out resources on the time axis and transmit signals in order to secure the desired received power.

On the other hand, since DL uses OFDM, it is easy to frequency multiplex the reference signal and data signal (PDSCH: Physical Downlink Shared Channel), and it is easier to introduce sTTI (shortened TTI length) compared to UL. Furthermore, the amount of DL traffic is considered to be larger than the amount of UL traffic, so latency reduction is more required.

From the above, when shortening the TTI length, there is a possibility of setting a shorter sTTI in DL than in UL.

Therefore, in one aspect of the present disclosure, when the sTTI lengths are different between DL and UL, in particular, the length of DL's sTTI (hereinafter referred to as "DL sTTI") is different from the UL's sTTI (hereinafter referred to as "UL sTTI"). The purpose of this invention is to appropriately define data allocation, data transmission/reception, and feedback transmission/reception timing when the length is shorter than

Embodiments of the present disclosure will be described in detail below with reference to the drawings.

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

FIG. 2 is a block diagram showing a main part configuration of base station 100 according to an embodiment of the present disclosure. In the base station 100 shown in FIG. 2, the transmitter 106 transmits a downlink signal using the first sTTI (short TTI; DL sTTI) of the downlink, which has a shorter TTI length than the TTI (Transmission Time Interval), and transmits the downlink signal to the receiver. 107 receives an uplink signal using a second uplink sTTI (UL sTTI) with a shorter TTI length than the TTI. When the length of the first sTTI is shorter than the second sTTI, the receiving unit 107 receives the uplink signal at the second sTTI after a predetermined interval set based on the length of the first sTTI from the transmission timing of the downlink signal.

Further, FIG. 3 is a block diagram showing the main configuration of the terminal 200 according to each embodiment of the present disclosure. In the terminal 200 shown in FIG. 3, the receiving section 201 receives a downlink signal using a downlink first sTTI (short TTI; DL sTTI) having a TTI length shorter than the TTI (Transmission Time Interval), and transmits the downlink signal to the transmitting section 212. transmits an uplink signal using the second sTTI (UL sTTI) on the uplink link, which has a shorter TTI length than the TTI. When the length of the first sTTI is shorter than the second sTTI, the transmitter 212 transmits the uplink signal at the second sTTI after a predetermined interval set based on the length of the first sTTI from the reception timing of the downlink signal.

In addition, in the following, the UL data signal assigned by sTTI (DL sTTI, UL sTTI) will be expressed as "sPUSCH", the DL data signal will be expressed as "sPDSCH", and the downlink control signal ( PDCCH: Physical Downlink Control Channel) is expressed as "sPDCCH".

(Embodiment 1)
[Base station configuration]
FIG. 4 is a block diagram showing the configuration of base station 100 according to this embodiment. In FIG. 4, base station 100 includes sTTI determination section 101, sPDCCH generation section 102, error correction encoding section 103, modulation section 104, signal allocation section 105, transmission section 106, reception section 107, It includes a signal separation section 108, an ACK/NACK reception section 109, a demodulation section 110, an error correction decoding section 111, and an ACK/NACK generation section 112.

The sTTI determining unit 101 determines the DL and UL sTTI lengths. sTTI determining section 101 outputs sTTI information indicating the determined sTTI length to sPDCCH generating section 102, signal allocating section 105, and signal separating section 108. Furthermore, sTTI determining section 101 outputs sTTI information to error correction encoding section 103 as upper layer signaling.

The sPDCCH generation section 102 determines the data size that can be transmitted and received using the sTTI, based on the sTTI information input from the sTTI determination section 101. The sPDCCH generation unit 102 generates an sPDCCH including DL or UL resource allocation information (eg, DL assignment or UL grant). sPDCCH generation section 102 outputs the generated sPDCCH to signal allocation section 105 for transmission to terminal 200. Further, sPDCCH generation section 102 outputs DL resource allocation information to signal allocation section 105 and outputs UL resource allocation information to signal separation section 108.

Furthermore, the sPDCCH generation section 102 generates DL data based on the content (ACK or NACK) of the ACK/NACK signal (that is, the ACK/NACK signal for the DL data signal (sPDSCH)) input from the ACK/NACK reception section 109. Determine whether retransmission of the signal is necessary or not, and generate sPDCCH according to the determination result.

Note that the details of the transmission/reception timing of data assignment (DL assignment, UL grant), data transmission/reception (PDSCH, PUSCH), and feedback (ACK/NACK signal) in base station 100 will be described later.

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

Modulation section 104 performs modulation processing on the signal received from error correction encoding section 103 and outputs the modulated signal to signal allocation section 105 .

Based on the sTTI information input from sTTI determination section 101, signal allocation section 105 selects a signal received from modulation section 104, a control signal (sPDCCH) received from sPDCCH generation section 102, or a control signal (sPDCCH) input from ACK/NACK generation section 112. The ACK/NACK signal (that is, the ACK/NACK signal for the UL data signal (sPDSCH)) is assigned to a predetermined downlink resource. A transmission signal is formed by allocating the control signal (sPDCCH) or data signal (sPDSCH) to a predetermined resource in this manner. The formed transmission signal is output to the transmission section 106.

Transmitting section 106 performs wireless transmission processing such as up-conversion on the transmission signal input from signal allocation section 105, and transmits the signal to terminal 200 via the antenna.

Receiving section 107 receives a signal transmitted from terminal 200 via an antenna, performs wireless reception processing such as down-conversion on the received signal, and outputs it to signal separation section 108 .

Signal separation section 108 determines the reception frequency and time of the sPUSCH (UL data signal) and ACK/NACK signal based on the UL resource allocation information input from sPDCCH generation section 102 and the sTTI information input from sTTI determination section 101. Identify timing. Then, signal separation section 108 separates the UL data signal from the received signal and outputs it to demodulation section 110 , and separates the ACK/NACK signal from the received signal and outputs it to ACK/NACK reception section 109 .

ACK/NACK receiving section 109 outputs the contents of the ACK/NACK signal (ACK or NACK) for the DL data signal input from signal separating section 108 to sPDCCH generating section 102 .

Demodulation section 110 performs demodulation processing on the signal input from signal separation section 108 and outputs the obtained signal to error correction decoding section 111.

Error correction decoding section 111 decodes the signal input from demodulation section 110 to obtain a received data signal (UL data signal) from terminal 200. Error correction decoding section 111 outputs the UL data signal to ACK/NACK generation section 112.

The ACK/NACK generation unit 112 uses a CRC (Cyclic Redundancy Check) to determine whether or not there is an error in the UL data signal input from the error correction decoding unit 111, and converts the determination result into an ACK/NACK. It is output to signal allocation section 105 as a signal.

[Terminal configuration]
FIG. 5 is a block diagram showing the configuration of terminal 200 according to this embodiment. In FIG. 5, terminal 200 includes receiving section 201, signal separating section 202, demodulating section 203, error correction decoding section 204, sTTI setting section 205, error determining section 206, and ACK/NACK generating section 207. , an sPDCCH receiving section 208, an error correction encoding section 209, a modulating section 210, a signal allocation section 211, and a transmitting section 212.

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

Based on the DL sTTI length input from sTTI setting section 205, signal separation section 202 separates a signal (sPDCCH signal) allocated to a resource to which sPDCCH may be allocated, and outputs it to sPDCCH reception section 208. do. Furthermore, signal separation section 202 separates a DL data signal (sPDSCH) from the received signal based on DL resource allocation information input from sPDCCH reception section 208 and outputs it to demodulation section 203 .

Demodulation section 203 demodulates the signal received from signal separation section 202 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 and outputs the obtained received data signal. Additionally, error correction decoding section 204 outputs the received data signal to error determining section 206 . Additionally, error correction decoding section 204 decodes the demodulated signal received from demodulation section 203 and outputs the obtained upper layer signaling (including sTTI information) to sTTI setting section 205 .

The sTTI setting section 205 sets the sTTI length for DL and UL based on the sTTI information input from the error correction decoding section 204, and outputs information indicating the set DL sTTI length to the signal separation section 202, Information indicating the UL sTTI length is output to signal allocation section 211.

Error determination section 206 detects an error in the CRC of the received data signal, and outputs the detection result to ACK/NACK generation section 207.

Based on the detection result of the received data signal inputted from the error determining section 206, the ACK/NACK generation section 207 generates an ACK if there is no error, generates a NACK if there is an error, and generates the generated ACK/NACK. The NACK signal is output to the signal allocation section 211.

The sPDCCH receiving section 208 extracts resource allocation information (DL resource allocation information, UL resource allocation information) from the sPDCCH received from the signal separation section 202, outputs the DL resource allocation information to the signal separation section 202, and extracts the UL resource allocation information. is output to the signal allocation section 211.

Error correction encoding section 209 performs error correction encoding on the transmission data signal (UL data signal) and outputs the encoded data signal to modulation section 210 .

Modulating section 210 modulates the data signal received from error correction encoding section 209 and outputs the modulated data signal to signal allocation section 211.

Signal allocation section 211 allocates the data signal input from modulation section 210 to resources based on the information indicating the UL sTTI length received from sTTI setting section 205 and the UL resource allocation information received from sPDCCH reception section 208, and transmits the data signal. output to section 212. Further, the signal allocation section 211 allocates the ACK/NACK signal input from the ACK/NACK generation section 207 to an ACK/NACK resource, or multiplexes it with the UL data signal and outputs it to the transmission section 212.

Note that the details of the reception of data assignment (DL assignment, UL grant), data transmission/reception (PDSCH, PUSCH), and transmission/reception timing of feedback (ACK/NACK signal) in terminal 200 will be described later.

The transmitting unit 212 performs transmission processing such as up-conversion on the signal input from the signal allocation unit 211, and transmits the signal via the antenna.

Furthermore, the terminal 200 transmits the UL data signal based on the content (ACK or NACK) of the ACK/NACK signal separated from the received signal by the signal separation section 202 (that is, the ACK/NACK signal for the UL data signal (sPUSCH)). It is determined whether retransmission of sPUSCH is necessary or not, and the sPUSCH is retransmitted according to the determination result (not shown).

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

In this embodiment, the DL sTTI length and the UL sTTI length are different, and when the DL sTTI length is shorter than the UL sTTI length, the base station 100 and the terminal 200 perform data allocation (in the sPDCCH) based on the DL sTTI length. Determines the transmission/reception timing of UL grant, DL assignment), data transmission/reception (sPUSCH, sPDSCH), and feedback (ACK/NACK signal).

Specifically, regarding DL data, the terminal 200 (transmission unit 212) sets the sTTI for receiving the sPDCCH including DL assignment and the sPDSCH assigned by the DL assignmetn to be the same DL sTTI. Furthermore, the terminal 200 sends an ACK/ACK to the sPDSCH in the UL sTTI after a predetermined interval set based on the length of the DL sTTI from the timing of the DL sTTI that received the sPDSCH (that is, the DL sTTI that received the DL assignment). Send NACK signal. In other words, the base station 100 (receiving unit 107) transmits the UL after a predetermined interval set based on the length of the DL sTTI from the timing of the DL sTTI that transmitted the sPDSCH (DL sTTI that transmitted the DL assignment of the sPDSCH). An ACK/NACK signal for the sPDSCH is received at sTTI.

Regarding UL data, the terminal 200 (transmission unit 212) transmits the sPUSCH at a UL sTTI after a predetermined interval set based on the length of the DL sTTI from the reception timing of the sPDCCH including the UL grant. That is, the base station 100 (receiving unit 107) receives the sPUSCH at the UL sTTI after a predetermined interval set based on the length of the DL sTTI from the transmission timing of the sPDCCH including the UL grant.

Furthermore, the base station 100 (transmission unit 106) transmits an ACK/NACK signal for the sPUSCH at a DL sTTI after a predetermined interval set based on the length of the DL sTTI from the timing of the UL sTTI at which the sPUSCH is received. . That is, the terminal 200 (receiving unit 201) receives the ACK/NACK signal for the sPUSCH at the DL sTTI after a predetermined interval from the timing of the UL sTTI that transmitted the sPUSCH.

Furthermore, if the UL timing determined based on the DL sTTI length does not match the UL sTTI boundary, the base station 100 and the terminal 200 transmit and receive the UL signal (sPUSCH or ACK/NACK signal) to match the UL sTTI boundary. delay until the time is right.

For example, the base station 100 and the terminal 200 define the timing of data allocation, data transmission/reception, and feedback (the transmission timing of the second signal with respect to the first signal) as follows.
Timing regarding DL data
DL assignment in sPDCCH - sPDSCH : same sTTI
sPDSCH - ACK/NACK feedback : after at least X DL sTTIs
Timing regarding UL data
UL grant in sPDCCH - sPUSCH : after at least X DL sTTIs
sPUSCH - ACK/NACK feedback : after at least X DL sTTIs

Note that "at least X DL sTTIs" means that the second signal (sPDSCH, ACK/NACK feedback, or This indicates that there is an interval of at least (X-1) sTTI before starting transmission/reception of sPUSCH or ACK/NACK feedback, and the second signal is assigned to the first sTTI after that interval.

The operations of data allocation, data transmission/reception, and feedback in base station 100 and terminal 200 will be described in detail below.

First, an example of the operation at the time of UL data allocation will be explained. UL data allocation assumes synchronous HARQ. Note that in the operation example below, the HARQ process ID is shown for explanation, but the HARQ process ID is not notified to the terminal 200, and the base station 100 and the terminal 200 each use the UL sTTI number and the HARQ process ID. It is associated with an ID.

<Operation example 1-1: UL data allocation (UL 7 symbols sTTIs and DL 3/4 symbols sTTIs)>
Figure 6 shows the transmission and reception timing between the sPDCCH and sPUSCH in which a UL grant instructing the transmission of a UL data signal (sPUSCH) is arranged, and the transmission and reception between the sPUSCH and an ACK/NACK signal for the sPUSCH in operation example 1-1. An example of timing is shown.

In operation example 1-1, as shown in FIG. 6, the UL sTTI length is 7 symbols, the DL sTTI length is 3/4 symbols, and X=4. In 3/4 symbols sTTIs, each sTTI is composed of the first 4 symbols and the last 3 symbols in one slot (that is, two sTTIs per slot) (see FIG. 1, for example). That is, in FIG. 6, there are four DL sTTIs per subframe, and DL sTTIs #0 to #19 are allocated from subframe #0 to subframe #4. Further, in FIG. 6, there are two UL sTTIs per subframe, and UL sTTIs #0 to #9 are allocated from subframe #0 to subframe #4.

That is, in operation example 1-1, the number of DL sTTIs (four per subframe) is twice the number of UL sTTIs (two per subframe).

Regarding the UL grant and sPUSCH, when X=4, the base station 100 and the terminal 200 start transmitting and receiving the sPUSCH at least 4 DL sTTIs after transmitting and receiving the UL grant (sPDCCH) based on the DL sTTI length. That is, there is an interval of at least 3 DL sTTI (=X-1) after the transmission and reception of the UL grant is completed until the transmission and reception of the sPUSCH is started. That is, the base station 100 and the terminal 200 transmit and receive the sPUSCH at the first UL sTTI after an interval of 3 DL sTTIs from the transmission/reception timing of the UL grant.

For example, if the base station 100 transmits a UL grant with HARQ process ID #0 at DL sTTI#0, the timing after an interval of 3DL sTTI from the timing at which transmission/reception of the UL grant is completed (DL sTTI#0) is the DL sTTI. It is #4. Therefore, the terminal 200 transmits sPUSCH with HARQ process ID #0 at UL sTTI#2, which is the same timing as DL sTTI#4.

Similarly, regarding the sPUSCH and the ACK/NACK signal, when X=4, the base station 100 and the terminal 200 transmit the ACK/NACK signal for the sPUSCH at least 4 DL sTTIs after the transmission/reception of the sPUSCH, based on the DL sTTI length. Start sending and receiving. That is, there is an interval of at least 3 DL sTTI after the transmission and reception of the sPUSCH is completed until the transmission and reception of the ACK/NACK signal is started. That is, the base station 100 and the terminal 200 transmit and receive the ACK/NACK signal at the first DL sTTI after an interval of 3 DL sTTIs from the transmission/reception timing of the sPUSCH.

For example, when the terminal 200 transmits sPUSCH with HARQ process ID #0 using UL sTTI#2, the timing after an interval of 3DL sTTI from the timing when the transmission/reception of sPUSCH is completed (DL sTTI#5) is DL sTTI#9. be. Therefore, base station 100 transmits an ACK/NACK signal for sPUSCH of HARQ process ID#0 in DL sTTI#9.

In this way, when X=4, base station 100 and terminal 200 allocate UL grants and sPUSCH, and sPUSCH and ACK/NACK signals, respectively, at intervals of 3 DL sTTI or more.

Note that in FIG. 6, the number of symbols corresponding to the 3 DL sTTI interval differs depending on the combination of DL sTTIs forming the 3 DL sTTI interval. Specifically, in the case of DL sTTI #1, 2, and 3, the 3 DL sTTI interval is 10 OFDM symbols, but in the case of DL sTTI #6, 7, and 8, the 3 DL sTTI interval is 11 OFDM symbols. This is because the DL sTTI may consist of 4 symbols or 3 symbols.

In addition, in operation example 1-1, the UL grant is placed only in the rearmost DL sTTI at a timing that is more than (X-1) DL sTTI (3 DL sTTI in Figure 6) before the UL sTTI boundary timing. and limit. In this case, as shown in FIG. 6, UL grants are allocated to half of the plurality of DL sTTIs, and no UL grants are allocated to the remaining half of the DL sTTIs. Thereby, the probability of erroneously detecting a UL grant (false alert) can be reduced compared to the case where the terminal 200 monitors UL grants at all DL sTTIs.

Further, in operation example 1-1, the DL sTTI in which the ACK/NACK signal is transmitted and received is different from the DL sTTI in which the UL grant is transmitted and received. In this way, since the resources used for UL grants and the resources used for ACK/NACK signals are different, there is an advantage that the degree of congestion of resources where control signals are allocated is alleviated. This makes it possible to avoid restrictions on UL data allocation due to a lack of control signal resources in DL.

Next, in FIG. 6, there are three methods (options 1 to 3) regarding the operation when the terminal 200 receives the ACK/NACK signal of HARQ process ID #0 at DL sTTI #9.

Option 1:
After receiving the ACK/NACK signal in DL sTTI#9, the terminal 200 receives the DL sTTI# in which the UL grant corresponding to the same HARQ process ID#0 is transmitted regardless of whether the ACK/NACK signal is ACK or NACK. Attempt to detect UL grant at 10. When detecting a UL grant in DL sTTI#10, the terminal 200 discards the ACK/NACK signal and transmits sPUSCH according to the instruction of the UL grant. On the other hand, if the terminal 200 does not detect a UL grant in DL sTTI#10, if the ACK/NACK signal received in DL sTTI#9 is ACK, the terminal 200 transmits the UL data signal (sPUSCH) of HARQ process ID#0. If the ACK/NACK signal received at DL sTTI#9 is NACK, a retransmission signal of HARQ process ID #0 is transmitted at UL sTTI#7.

Option 2:
If the ACK/NACK signal received in DL sTTI#9 is ACK, terminal 200 attempts to detect a UL grant in DL sTTI#10, in which a UL grant corresponding to the same HARQ process ID#0 is transmitted. When detecting a UL grant, the terminal 200 transmits sPUSCH according to the instruction of the UL grant. On the other hand, if no UL grant is detected, the terminal 200 does not transmit the UL data signal (sPUSCH) of HARQ process ID #0. Furthermore, if the ACK/NACK signal received in DL sTTI#9 is NACK, the terminal 200 does not detect a UL grant in DL sTTI#10, where a UL grant corresponding to the same HARQ process ID#0 is transmitted. Then, send a retransmission signal for HARQ process ID #0 using UL sTTI#7.

Option 3:
Terminal 200 attempts to detect NACK with DL sTTI#9. If a NACK is not detected in DL sTTI#9, the terminal 200 attempts to detect a UL grant in DL sTTI#10, where a UL grant corresponding to the same HARQ process ID#0 is transmitted. When detecting a UL grant in DL sTTI#10, the terminal 200 transmits sPUSCH according to the instruction of the UL grant. On the other hand, if a UL grant is not detected in DL sTTI#10, the terminal 200 does not transmit the UL data signal (sPUSCH) of HARQ process ID#0. Furthermore, when detecting a NACK in DL sTTI#9, the terminal 200 detects a UL grant in DL sTTI#10, where a UL grant corresponding to the same HARQ process ID#0 is transmitted, and detects a NACK in HARQ process ID#9. Send a retransmission signal of 0 with UL sTTI#7.

In this way, in option 1 and option 2, the ACK/NACK signal is always transmitted as ACK or NACK like the conventional PHICH (Physical HARQ Indicator Channel), and the terminal 200 does not know whether it is ACK or NACK. It is assumed that judgment will be made. Option 3 assumes that the ACK/NACK signal is transmitted only in the case of NACK (with an error), and that the terminal 200 detects whether or not the ACK/NACK signal is present.

In option 1, the terminal 200 always attempts to detect a UL grant, so even if an ACK is mistakenly determined to be a NACK, if a UL grant is detected, it is possible to prevent the terminal 200 from transmitting a retransmission signal at the wrong timing. can. Furthermore, in options 2 and 3, the terminal 200 does not detect a UL grant when detecting a NACK, so the power consumption of the terminal 200 can be suppressed.

Note that the minimum value of the number of UL HARQ processes is determined from the transmission interval of sPUSCH with the same UL HARQ process ID. In FIG. 6, sPUSCH with UL HARQ process ID#0 is transmitted in UL sTTI#2, and ACK/NACK thereto is transmitted in DL sTTI#9. Therefore, since it is determined at DL sTTI#9 whether retransmission is necessary, the base station 100 can transmit the UL grant of the same UL HARQ ID#0 after DL sTTI#9. When the base station 100 transmits a UL grant at DL sTTI#9 (DL sTTI#10 in FIG. 10; details will be described later), the terminal 200 transmits sPUSCH at the first UL sTTI after 3 DL sTTI intervals. There will be a certain UL sTTI #7. Therefore, sPUSCHs with the same UL HARQ process ID#0 can be transmitted at 5 UL sTTI intervals. When the transmission interval of the same UL HARQ process is 5 UL sTTI, five UL HARQ processes can be transmitted during 5 UL sTTI, so the minimum value of the number of UL HARQ processes can be determined to be 5.

Note that the number of UL HARQ processes can also be set to a value greater than 5. In that case, the retransmission interval becomes longer, so the delay time increases. Furthermore, as the number of UL HARQ processes increases, the required buffer also increases, so it is desirable to set the number of UL HARQ processes to the minimum possible value.

Note that in FIG. 6, the base station 100 does not transmit a UL grant in DL sTTI #9, but transmits a UL grant in DL sTTI #10, which is three DL sTTI intervals before UL sTTI #7. This is because transmitting a UL grant at DL sTTI#10 does not affect the overall amount of delay. Note that the number of UL HARQ processes may be determined in advance from the DL sTTI length and the UL sTTI length, or the number of UL HARQ processes may be determined in advance by specifying the minimum possible value and setting it at the base station 100 and the terminal 200, respectively. good.

Furthermore, although we focused on HARQ process ID#0 here, the same applies to other HARQ process IDs#2 to #4.

<Operation example 1-2: UL data allocation (UL 3/4 symbols sTTIs and DL 2 symbols sTTIs)>
Figure 7 shows the transmission and reception timing between the sPDCCH and sPUSCH in which a UL grant instructing the transmission of a UL data signal (sPUSCH) is arranged, and the transmission and reception between the sPUSCH and an ACK/NACK signal for the sPUSCH in operation example 1-2. An example of timing is shown.

In operation example 1-2, as shown in FIG. 7, the UL sTTI length is 3/4 symbols, the DL sTTI length is 2 symbols, and X=4. That is, in FIG. 7, there are seven DL sTTIs per subframe, and DL sTTIs #0 to #27 are allocated from subframe #0 to subframe #3. Further, in FIG. 7, there are four UL sTTIs per subframe, and UL sTTIs #0 to #15 are allocated from subframe #0 to subframe #3.

That is, in operation example 1-2, the number of DL sTTIs (7 per subframe) is 7/4 times the number of UL sTTIs (4 per subframe).

When X=4, as in operation example 1-1, the base station 100 and the terminal 200 allocate the UL grant and the sPUSCH, and the sPUSCH and the ACK/NACK signal, respectively, with an interval of 3 DL sTTI or more.

For example, regarding UL grant and sPUSCH, if base station 100 transmits UL grant with HARQ process ID #0 with DL sTTI#1, the interval of 3DL sTTI from the timing when transmission/reception of UL grant is completed (DL sTTI#1) The later timing is DL sTTI#5. Since the timing of DL sTTI#5 does not match the UL sTTI boundary, the terminal 200 delays the transmission of sPUSCH until UL sTTI#3, which is the first UL TTI after the timing of DL sTTI#5, and transmits the UL sTTI. Send sPUSCH with HARQ process ID #0 using #3.

Similarly, regarding sPUSCH and ACK/NACK signals, if the terminal 200 transmits sPUSCH with HARQ process ID #0 in UL sTTI#3, the interval of 3DL sTTI from the timing when transmission/reception of sPUSCH is completed (DL sTTI#6) The later timing is DL sTTI#10. Therefore, the base station 100 transmits an ACK/NACK signal for the sPUSCH of HARQ process ID#0 in DL sTTI#10.

In addition, in operation example 1-2, as in operation example 1-1, the UL grant is issued at the most backward timing at least (X-1) DL sTTI (3 DL sTTI in Figure 7) before the timing of the UL sTTI boundary. Restricts the DL to be placed only in sTTI. In this case, as shown in FIG. 7, UL grants are allocated to four DL sTTIs among the DL sTTIs in one subframe, and no UL grants are allocated to the remaining three DL sTTIs. Thereby, the probability of erroneously detecting a UL grant (false alert) can be reduced compared to the case where the terminal 200 monitors UL grants at all DL sTTIs.

Further, in operation example 1-2, as in operation example 1-1, the DL sTTI in which the ACK/NACK signal is transmitted and received is different from the DL sTTI in which the UL grant is transmitted and received. In this way, since the resources used for UL grants and the resources used for ACK/NACK signals are different, there is an advantage that the degree of congestion of resources where control signals are allocated is alleviated. This makes it possible to avoid restrictions on UL data allocation due to a lack of control signal resources in DL.

However, in operation example 1-2, unlike operation example 1-1, the number of DL sTTIs is 7/4 times the number of UL sTTIs, so the ACK/NACK signal and UL grant should all be placed in different DL sTTIs. I can't.

In the sTTI arrangement in FIG. 7, neither UL grant nor ACK/NACK signal is arranged in DL sTTI #11 and DL sTTI #18, whereas UL grant and ACK/NACK signals are arranged in DL sTTI #10 and DL sTTI #17. and ACK/NACK signals are arranged.

Therefore, in order to distribute the control signal resources, the base station 100 transmits the ACK/NACK signal to one DL sTTI before the UL grant with the same HARQ process ID as the HARQ process ID of the ACK/NACK signal is transmitted. may be adjusted to be transmitted with a DL sTTI of FIG. 8 shows an operational example of adjusting the DL sTTI in which the ACK/NACK signal is placed.

In FIG. 8, the ACK/NACK signal of HARQ process ID#0 placed in DL sTTI#10 in FIG. Placed at #11. Similarly, in Figure 8, the ACK/NACK signal of HARQ process ID#4 that was placed in DL sTTI#17 in Figure 7 is one of the DL sTTI#19 where the UL grant of HARQ process ID#4 is placed. Placed in previous DL sTTI#18. As a result, control signals (UL grant and ACK/NACK signals) are distributed and arranged.

From a delay perspective, the arrangement of ACK/NACK signals should be 3 DL sTTI intervals from the sPUSCH with the same HARQ process ID, and 3 DL sTTI intervals from the next sPUSCH with the same HARQ process ID that may be retransmitted. . Therefore, the ACK/NACK signal of HARQ process ID#0 placed in DL sTTI#10 is placed in DL sTTI#11, and the ACK/NACK signal of HARQ process ID#4 placed in DL sTTI#17 is Even if it is placed in DL sTTI#18, there is no problem from a delay perspective.

By delaying the ACK/NACK signal backwards as shown in FIG. 8, the base station 100 can determine whether to perform adaptive retransmission or non-adaptive retransmission from the backward scheduling state. The flexibility of the scheduler of station 100 can be improved.

<Operation example 1-3: UL data allocation (UL 7 symbols sTTIs and DL 2 symbols sTTIs)>
Figure 9 shows the transmission and reception timing between the sPDCCH and sPUSCH in which a UL grant instructing the transmission of a UL data signal (sPUSCH) is arranged, and the transmission and reception between the sPUSCH and an ACK/NACK signal for the sPUSCH in operation example 1-3. An example of timing is shown.

In operation example 1-3, as shown in FIG. 9, the UL sTTI length is 7 symbols, the DL sTTI length is 2 symbols, and X=4. That is, in FIG. 9, there are seven DL sTTIs per subframe, and DL sTTIs #0 to #27 are allocated from subframe #0 to subframe #3. Furthermore, in FIG. 9, there are two UL sTTIs per subframe, and UL sTTIs #0 to #7 are allocated from subframe #0 to subframe #3.

That is, in operation example 1-3, the number of DL sTTIs (7 per subframe) is 7/2 times the number of UL sTTIs (2 per subframe).

When X=4, as in operation example 1-1, the base station 100 and the terminal 200 allocate the UL grant and the sPUSCH, and the sPUSCH and the ACK/NACK signal, respectively, with an interval of 3 DL sTTI or more.

For example, regarding UL grant and sPUSCH, if the base station 100 transmits a UL grant with HARQ process ID #0 at DL sTTI#3, the interval of 3DL sTTI from the timing when transmission/reception of UL grant is completed (DL sTTI#3) The later timing is DL sTTI#7. Terminal 200 transmits sPUSCH with HARQ process ID #0 at UL sTTI#2, which is the same timing as DL sTTI#7.

Similarly, regarding sPUSCH and ACK/NACK signals, if the terminal 200 transmits sPUSCH of HARQ process ID #0 with UL sTTI#2, the interval of 3DL sTTI from the timing when transmission/reception of sPUSCH is completed (DL sTTI#10) The later timing is DL sTTI#14. Therefore, the base station 100 transmits an ACK/NACK signal for the sPUSCH of HARQ process ID#0 in DL sTTI#14.

In addition, in operation example 1-3, as in operation example 1-1, the UL grant is issued at the most backward timing at least (X-1) DL sTTI (3 DL sTTI in Figure 9) before the timing of the UL sTTI boundary. Restricts the DL to be placed only in sTTI. In this case, as shown in FIG. 9, UL grants are allocated to two DL sTTIs among the DL sTTIs in one subframe, and no UL grants are allocated to the remaining five DL sTTIs. Thereby, the probability of erroneously detecting a UL grant (false alert) can be reduced compared to the case where the terminal 200 monitors UL grants at all DL sTTIs.

Further, in operation example 1-3, as in operation example 1-1, the DL sTTI in which the ACK/NACK signal is transmitted and received is different from the DL sTTI in which the UL grant is transmitted and received. In this way, since the resources used for UL grants and the resources used for ACK/NACK signals are different, there is an advantage that the degree of congestion of resources where control signals are allocated is alleviated. This makes it possible to avoid restrictions on UL data allocation due to a lack of control signal resources in DL.

However, in operation example 1-3, the number of DL sTTIs is 7/2 times the number of UL sTTIs, so as in operation example 1-2, the ACK/NACK signal and UL grant should all be placed in different DL sTTIs. I can't.

Therefore, in order to distribute the control signal resources, the base station 100 transmits the ACK/NACK signal to one DL sTTI before the UL grant with the same HARQ process ID as the HARQ process ID of the ACK/NACK signal is transmitted. may be adjusted to be transmitted with a DL sTTI of FIG. 10 shows an operational example of adjusting the DL sTTI in which the ACK/NACK signal is placed.

In FIG. 10, the ACK/NACK signal of HARQ process ID#0 placed in DL sTTI#14 in FIG. It is placed at #16 (DL sTTI two places behind DL sTTI #14). Similarly, in FIG. 10, the ACK/NACK signal of HARQ process ID#1 that was placed in DL sTTI#17 in FIG. It is placed in the previous DL sTTI#19 (two DL sTTIs behind DL sTTI#17). As a result, control signals (UL grant and ACK/NACK signals) are distributed and arranged.

Similar to operation example 1-2, from the perspective of delay, the arrangement of ACK/NACK signals is 3 DL sTTI intervals from the sPUSCH of the same HARQ process ID, and 3 DL sTTI intervals from the sPUSCH of the same HARQ process ID that may be retransmitted. DL sTTI interval is sufficient. Therefore, the ACK/NACK signal of HARQ process ID#0 placed in DL sTTI#14 is placed in DL sTTI#16, and the ACK/NACK signal of HARQ process ID#1 placed in DL sTTI#17 is Even if it is placed in DL sTTI#19, there is no problem from a delay perspective.

Furthermore, by delaying the ACK/NACK signal backwards as shown in FIG. 10, the base station 100 can determine whether to perform adaptive retransmission or non-adaptive retransmission from the backward scheduling state. , the flexibility of the scheduler of the base station 100 can be improved.

The above describes operation examples 1-1 to 1-3 when allocating UL data.

Next, an example of the operation at the time of DL data allocation will be described. DL data allocation assumes Asynchronous HARQ. Further, the HARQ process ID is notified to the terminal 200 by DL assignment.

Note that in the operation example below, a case will be described in which consecutive HARQ process IDs can be assigned to consecutive DL sTTIs, but the present invention is not limited to this.

<Operation example 2-1: DL data allocation (UL 7 symbols sTTIs and DL 3/4 symbols sTTIs)>
Figure 11 shows the transmission and reception timing between the sPDCCH and sPDSCH where a DL assignment that instructs the transmission of a DL data signal (sPDSCH) is arranged, and the transmission and reception between the sPDSCH and an ACK/NACK signal for the sPDSCH in operation example 2-1. An example of timing is shown.

In operation example 2-1, as shown in FIG. 11, the UL sTTI length is 7 symbols, the DL sTTI length is 3/4 symbols, and X=4. That is, in FIG. 11, there are four DL sTTIs per subframe, and DL sTTIs #0 to #11 are allocated from subframe #0 to subframe #2. Furthermore, in FIG. 11, there are two UL sTTIs per subframe, and UL sTTIs #0 to #5 are allocated from subframe #0 to subframe #2.

That is, in Operation Example 2-1, the number of DL sTTIs (4 per subframe) is twice the number of UL sTTIs (2 per subframe), as in Operation Example 1-1.

Regarding the DL assignment and sPDSCH, the base station 100 transmits the sPDSCH specified by the DL assignment using the same DL sTTI as the DL sTTI that transmits and receives the DL assignment. For example, when transmitting DL assignment of HARQ process ID #0 with DL sTTI#0, base station 100 transmits sPDSCH with the same DL sTTI#0.

Regarding the sPDSCH and the ACK/NACK signal, when X=4, the base station 100 and the terminal 200 transmit the ACK/NACK signal for the sPDSCH at least 4 DL sTTIs after the transmission/reception of the sPDSCH, based on the DL sTTI length. Start sending and receiving. That is, there is an interval of at least 3 DL sTTI (=X-1) after the transmission and reception of the sPDSCH is completed until the transmission and reception of the ACK/NACK signal is started. That is, the base station 100 and the terminal 200 transmit and receive an ACK/NACK signal at the first UL sTTI after an interval of 3 DL sTTIs from the transmission/reception timing of the sPDSCH.

For example, if the base station 100 transmits an sPDSCH with HARQ process ID#0 with DL sTTI#0, the timing after an interval of 3DL sTTI from the timing when the transmission/reception of sPDSCH is completed (DL sTTI#0) is DL sTTI#4. It is. Therefore, the terminal 200 transmits an ACK/NACK signal for the sPDSCH of HARQ process ID#0 at UL sTTI#2, which is the same timing as DL sTTI#4.

Note that although we focused on HARQ process ID#0 here, the same applies to other HARQ process IDs #2 to #4.

In FIG. 11, the number of DL sTTIs is twice the number of UL sTTIs, so the terminal 200 transmits two ACK/NACK signals for each sPDSCH received in two DL sTTIs, per UL sTTI. At that time, the terminal 200 transmits multiple ACK/NACKs using the UL resource, for example, by multiplexing or bundling.

In LTE/LTE-Advanced, the start position of the UL resource on which the UE transmits the ACK/NACK signal is indicated by an upper layer parameter called N1_PUCCH, and the amount of offset from the start position is determined from the (E)CCE number.

On the other hand, in operation example 2-1, the terminal 200 transmits the sPDSUC and the ACK/NACK signal to multiple DL sTTIs used for receiving the sPDSCH in which the corresponding ACK/NACK signals are transmitted in the same UL sTTI. The transmission position of the ACK/NACK signal may be specified from the DL assignment received at the DL sTTI with the larger DL sTTI number (that is, the later DL sTTI). This is because in the latter half of the DL sTTI, the scheduler can change the resource allocation in consideration of the ACK/NACK resources later, which increases the flexibility of scheduling. For example, in FIG. 11, the terminal 200 selects the DL sTTI number that is larger among the DL sTTI#1 and DL sTTI#2 used to receive the sPDSCH corresponding to the ACK/NACK signal transmitted in UL sTTI#3. The transmission position of the ACK/NACK signal is specified from the DL assignment received on the sPDCCH of DL sTTI#2.

Furthermore, regarding the sPDSCH and the ACK/NACK signal, the terminal 200 determines whether the corresponding ACK/NACK signal is actually in one DL sTTI among the multiple DL sTTIs used for receiving the sPDSCH transmitted in the same UL sTTI. When receiving the sPDSCH, the transmission position of the ACK/NACK signal is specified from the DL assignment received in the corresponding DL sTTI.

Note that the transmission position of the ACK/NACK signal is determined from the shift amount based on the DL sTTI and the shift amount based on the CCE number of the DL assignment from the N1_PUCCH notified by the upper layer. It is assumed that the shift amount based on DL sTTI is determined in advance. It is also conceivable that N1_PUCCH is notified in the upper layer for each DL sTTI.

<Operation example 2-2: DL data allocation (UL 3/4 symbols sTTIs and DL 2 symbols sTTIs)>
FIG. 12 shows the transmission and reception timing between the sPDCCH and the sPDSCH in which a DL assignment that instructs the transmission of a DL data signal (sPDSCH) is arranged, and the transmission and reception between the sPDSCH and the ACK/NACK signal for the sPDSCH in operation example 2-2. An example of timing is shown.

In operation example 2-2, as shown in FIG. 12, the UL sTTI length is 3/4 symbols, the DL sTTI length is 2 symbols, and X=4. That is, in FIG. 12, there are seven DL sTTIs per subframe, and DL sTTIs #0 to #13 are allocated from subframe #0 to subframe #1. Further, in FIG. 12, there are four UL sTTIs per subframe, and UL sTTIs #0 to #7 are allocated from subframe #0 to subframe #1.

That is, in Operation Example 2-2, the number of DL sTTIs (7 per subframe) is 7/4 times the number of UL sTTIs (4 per subframe), as in Operation Example 1-2.

Regarding the DL assignment and sPDSCH, the base station 100 transmits the sPDSCH specified by the DL assignment using the same DL sTTI as the DL sTTI that transmits and receives the DL assignment. For example, when transmitting DL assignment of HARQ process ID #0 with DL sTTI#0, base station 100 transmits sPDSCH with the same DL sTTI#0.

Regarding the sPDSCH and the ACK/NACK signal, when X=4, the base station 100 and the terminal 200 transmit the ACK/NACK signal for the sPDSCH at least 4 DL sTTIs after the transmission/reception of the sPDSCH, based on the DL sTTI length. Start sending and receiving. That is, there is an interval of at least 3 DL sTTI (=X-1) after the transmission and reception of the sPDSCH is completed until the transmission and reception of the ACK/NACK signal is started. That is, the base station 100 and the terminal 200 transmit and receive an ACK/NACK signal at the first UL sTTI after an interval of 3 DL sTTIs from the transmission/reception timing of the sPDSCH.

For example, if the base station 100 transmits an sPDSCH with HARQ process ID#0 with DL sTTI#0, the timing after an interval of 3DL sTTI from the timing when the transmission/reception of sPDSCH is completed (DL sTTI#0) is DL sTTI#4. It is. Since the timing of DL sTTI#4 does not match the boundary of UL sTTI, terminal 200 delays the transmission of the ACK/NACK signal until UL sTTI#3, which is the first UL sTTI after the timing of DL sTTI#4. , sends an ACK/NACK signal for sPDSCH of HARQ process ID#0 using UL sTTI#3.

In addition, in FIG. 12, the number of DL sTTIs is 7/4 times the number of UL sTTIs, so when the terminal 200 transmits two DL sTTI ACK/NACK signals per UL sTTI and one DL sTTI per UL sTTI. There are cases where an sTTI ACK/NACK signal is sent. In FIG. 12, two DL sTTI ACK/NACK signals are transmitted in each of UL sTTI #3, #4, and #5, and one DL sTTI ACK/NACK signal is transmitted in UL sTTI #6. In this way, since the maximum number of ACK/NACK signals to be transmitted differs for each UL sTTI, the terminal 200 can change the format used for transmitting ACK/NACK signals for each UL sTTI.

In addition, in FIG. 12, some ACK/NACK signals for the DL data signal (sPDSCH) assigned to the same subframe #0 are transmitted in the same subframe #0 as sPDSCH, and the remaining ACK/NACK signals are transmitted in the subframe Sent in #1. In other words, ACK/NACK signals for sPDSCH assigned to the same subframe #0 are transmitted in different subframes #0 and #1. This shortens the feedback delay for the DL data signal, making latency reduction more efficient.

Note that, for example, when determining and using applications such as interference control, CoMP, and D2D in units of subframes, it is desirable that usage methods be determined in units of subframes. Therefore, as shown in FIG. 13A or 13B, all ACK/NACK signals for DL data signals (sPDSCH) assigned to the same subframe may be transmitted in the same subframe. That is, the base station 100 and the terminal 200 transmit and receive ACK/NACK signals for each of the plurality of sPDSCHs transmitted and received in the same subframe, using the plurality of UL sTTIs in one subframe.

In FIGS. 13A and 13B, since subframe #1 is the subframe in which the ACK/NACK signal for sPDSCH transmitted in the final DL sTTI #6 of DL subframe #0 is transmitted, other DL sTTI of DL subframe #0 All signals, including the ACK/NACK signal for sPDSCH transmitted in subframe #1, are transmitted in subframe #1.

As a first implementation method, the timing of the ACK/NACK signal shown in FIG. 12 is shifted backward by 1 UL sTTI. Also, as a second implementation method, change X=4 to X=6. The value of X is set so that ACK/NACK signals for DL data signals (sPDSCH) assigned to the same subframe can be transmitted in the same subframe. This has the advantage of making it easier to allocate UL subframe interference control, CoMP, D2D, etc. in subframe units.

Note that although the first implementation method and the second implementation method differ in the number of ACK/NACK signals transmitted in UL sTTI, the maximum and minimum values of the number of ACK/NACK signals are the same.

<Operation example 2-3: DL data allocation (UL 7 symbols sTTIs and DL 2 symbols sTTIs)>
FIG. 14 shows the transmission and reception timing between the sPDCCH and the sPDSCH in which a DL assignment that instructs the transmission of a DL data signal (sPDSCH) is arranged, and the transmission and reception between the sPDSCH and an ACK/NACK signal for the sPDSCH in operation example 2-3. An example of timing is shown.

In operation example 2-3, as shown in FIG. 14, the UL sTTI length is 7 symbols, the DL sTTI length is 2 symbols, and X=4. That is, in FIG. 14, there are seven DL sTTIs per subframe, and DL sTTIs #0 to #13 are allocated from subframe #0 to subframe #1. Further, in FIG. 14, there are two UL sTTIs per subframe, and UL sTTIs #0 to #3 are allocated from subframe #0 to subframe #1.

That is, in Operation Example 2-3, the number of DL sTTIs (7 per subframe) is 7/2 times the number of UL sTTIs (2 per subframe), as in Operation Example 1-3.

Regarding the DL assignment and sPDSCH, the base station 100 allocates the sPDSCH specified by the DL assignment to the same DL sTTI that transmits and receives the DL assignment. For example, when transmitting DL assignment of HARQ process ID #0 with DL sTTI#0, base station 100 transmits sPDSCH with the same DL sTTI#0.

Regarding the sPDSCH and the ACK/NACK signal, when X=4, the base station 100 and the terminal 200 transmit the ACK/NACK signal for the sPDSCH at least 4 DL sTTIs after the transmission/reception of the sPDSCH, based on the DL sTTI length. Start sending and receiving. That is, there is an interval of at least 3 DL sTTI (=X-1) after the transmission and reception of the sPDSCH is completed until the transmission and reception of the ACK/NACK signal is started. That is, the base station 100 and the terminal 200 transmit and receive an ACK/NACK signal at the first UL sTTI after an interval of 3 DL sTTIs from the transmission/reception timing of the sPDSCH.

For example, if the base station 100 transmits an sPDSCH with HARQ process ID#0 with DL sTTI#0, the timing after an interval of 3DL sTTI from the timing when the transmission/reception of sPDSCH is completed (DL sTTI#0) is DL sTTI#4. It is. Since the timing of DL sTTI#4 does not match the boundary of UL sTTI, terminal 200 delays the transmission of the ACK/NACK signal until UL sTTI#2, which is the first UL sTTI after the timing of DL sTTI#4. , sends an ACK/NACK signal for sPDSCH of HARQ process ID#0 using UL sTTI#2.

In addition, in FIG. 14, the number of DL sTTIs is 7/2 times the number of UL sTTIs, so when the terminal 200 transmits 4 DL sTTI ACK/NACK signals per UL sTTI, and when the terminal 200 transmits 3 DL sTTIs per UL sTTI, There are cases where an sTTI ACK/NACK signal is sent. In FIG. 14, ACK/NACK signals of four DL sTTIs are transmitted in UL sTTI #2, and ACK/NACK signals of three DL sTTIs are transmitted in UL sTTI #3. In this way, since the maximum number of ACK/NACK signals to be transmitted differs for each UL sTTI, the terminal 200 can change the format used for transmitting ACK/NACK signals for each UL sTTI.

The above describes the operation examples 2-1 to 2-3 when allocating DL data.

In this way, in this embodiment, base station 100 and terminal 200 transmit and receive downlink signals (sPDCCH, sPDSCH, ACK/NACK signals) using DL sTTI, which has a shorter TTI length than TTI, and It also transmits and receives uplink signals (sPUSCH, ACK/NACK signals) using UL sTTI with a shortened TTI length. At that time, if the DL sTTI length is shorter than the UL sTTI length, the base station 100 and terminal 200 transmit and receive uplink signals at the UL sTTI after a predetermined interval set based on the DL sTTI length from the transmission timing of the downlink signal. do. Furthermore, if the determined transmission/reception timing does not match the UL sTTI boundary, the base station 100 and the terminal 200 delay the transmission/reception timing until the determined transmission/reception timing coincides with the UL sTTI boundary.

Thereby, even if the DL sTTI length and the UL sTTI length are different, the base station 100 and the terminal 200 can start transmitting and receiving signals from the respective boundaries of the DL sTTI and the UL sTTI. Therefore, according to this embodiment, the timing of data allocation, data transmission/reception, and feedback can be appropriately set when the sTTI lengths are different between DL and UL.

Note that although this embodiment shows an example in which the ACK/NACK signal is allocated to the ACK/NACK resource, the ACK/NACK resource may be a PUCCH (Physical Uplink Control Channel) resource. Furthermore, when a UL data signal is allocated, there is also a method of multiplexing an ACK/NACK signal with the UL data signal and transmitting the signal. In this case, if at least one of the multiple UL sTTIs is assigned a UL data signal, the terminal 200 may transmit an ACK/NACK signal for the sPDSCH transmitted in multiple DL sTTIs using that UL sTTI. good. This has the advantage that the PUCCH format and the PUSCH format do not coexist within the subframe, and the terminal 200 can transmit the signal within the subframe in one format.

Further, the operation of the present disclosure can be applied to combinations of the DL sTTI length and the UL sTTI length other than those shown in the operation example of this embodiment.

(Embodiment 2)
The base station and terminal according to this embodiment have the same basic configuration as the base station 100 and terminal 200 according to Embodiment 1, so they will be explained with reference to FIGS. 4 and 5.

In this embodiment, when the DL sTTI length and the UL sTTI length are different and the DL sTTI length is shorter than the UL sTTI length, the base station 100 and the terminal 200 perform data allocation (based on the DL sTTI length and absolute time). Determines the transmission/reception timing of UL grant, DL assignment within sPDCCH, data transmission/reception (sPUSCH, sPDSCH), and feedback (ACK/NACK signal).

Absolute time is a fixed length of time that takes into account processing delays or time required for communication with upper layers.

Further, as in Embodiment 1, when the UL timing determined based on the DL sTTI length does not match the UL sTTI boundary, the base station 100 and the terminal 200 delay it until the timing matches the UL sTTI boundary.

Specifically, regarding DL data, the base station 100 and the terminal 200 transmit an ACK/NACK signal for the sPDSCH at the UL sTTI after a predetermined interval set based on the DL sTTI length and absolute time from the transmission/reception timing of the sPDSCH. Send and receive.

Regarding UL data, the base station 100 and the terminal 200 receive the UL sTTI allocated by the UL grant after a predetermined interval set based on the DL sTTI length and absolute time from the transmission/reception timing of the sPDCCH including the UL grant. Send and receive sPUSCH. Furthermore, the base station 100 and the terminal 200 transmit and receive an ACK/NACK signal for the sPUSCH at a DL sTTI after a predetermined interval that is set based on the DL sTTI length and absolute time from the transmission/reception timing of the sPUSCH.

For example, the base station 100 and the terminal 200 transmit the second signal at a time after a predetermined number (X) of DL sTTI intervals plus absolute time (Y) from the transmission/reception timing of the first signal. may be sent and received. Specifically, the base station 100 and the terminal 200 define the timing of data allocation, data transmission/reception, and feedback (the transmission timing of the second signal with respect to the first signal) as follows. Here, the absolute time is expressed as Y msec.
Timing regarding DL data
DL assignment in sPDCCH - sPDSCH : same sTTI
sPDSCH - ACK/NACK feedback : after at least X DL sTTIs + Y msec
Timing regarding UL data
UL grant in sPDCCH - sPUSCH : after at least X DL sTTIs + Y msec
sPUSCH - ACK/NACK feedback : after at least X DL sTTIs + Y msec

Note that "at least X DL sTTIs + Y msec" means that the second signal (sPDSCH, ACK/ACK/ There is an interval of at least (X-1) sTTI + Y msec before starting to send or receive NACK feedback, sPUSCH or ACK/NACK feedback), and the second signal is assigned to the first sTTI after that interval. show.

The operations of data allocation, data transmission/reception, and feedback in base station 100 and terminal 200 will be described in detail below.

In the following, the UL sTTI length is set to 7 symbols, the DL sTTI length is set to 3/4 symbols, and X=4, similar to Operation Example 1-1 and Operation Example 2-1 of Embodiment 1. Also, assume that the absolute time Y=0.5 msec.

FIG. 15 shows an example of the transmission/reception timing between sPDCCH and sPUSCH in which a UL grant instructing transmission of a UL data signal (sPUSCH) is arranged, and the transmission/reception timing between sPUSCH and an ACK/NACK signal for the sPUSCH.

Regarding UL grant and sPUSCH, when X=4, base station 100 and terminal 200 transmit sPUSCH at least 4 DL sTTIs + 0.5 msec after transmission/reception of UL grant (sPDCCH) based on DL sTTI length and absolute time Y. Start sending and receiving. That is, there is an interval of at least 3 DL sTTI (=X-1) + 0.5 msec after the transmission and reception of the UL grant is completed until the transmission and reception of the sPUSCH is started. That is, the base station 100 and the terminal 200 transmit and receive sPUSCH at the first UL sTTI after an interval of 3 DL sTTI+0.5 msec.

Similarly, regarding the sPUSCH and ACK/NACK signals, when X=4, the base station 100 and the terminal 200 transmit the corresponding sPUSCH at least 4 DL sTTIs + 0.5 msec after the transmission/reception of the sPUSCH, based on the DL sTTI length and absolute time Y. Start transmitting and receiving ACK/NACK signals to sPUSCH. That is, there is an interval of at least 3 DL sTTI+0.5 msec after the transmission and reception of the sPUSCH is completed until the transmission and reception of the ACK/NACK signal is started. That is, the base station 100 and the terminal 200 transmit and receive the ACK/NACK signal at the first DL sTTI after an interval of 3 DL sTTI+0.5 msec from the sPUSCH transmission/reception timing.

Further, FIG. 16 shows an example of the transmission/reception timing between the sPDCCH and the sPDSCH in which a DL assignment that instructs the transmission of a DL data signal (sPDSCH) is arranged, and the transmission/reception timing between the sPDSCH and the ACK/NACK signal for the sPDSCH. .

Regarding the DL assignment and sPDSCH, the base station 100 transmits the sPDSCH specified by the DL assignment using the same DL sTTI as the DL sTTI that transmits and receives the DL assignment.

Regarding the sPDSCH and the ACK/NACK signal, when X=4, the base station 100 and the terminal 200 transmit the sPDSCH at least 4 DL sTTIs + 0.5 msec after the transmission/reception of the sPDSCH, based on the DL sTTI length and absolute time Y. Start sending and receiving ACK/NACK signals for That is, there is an interval of at least 3 DL sTTI (=X-1) + 0.5 msec after the completion of transmission and reception of sPDSCH until the start of transmission and reception of ACK/NACK signals. That is, the base station 100 and the terminal 200 transmit and receive the ACK/NACK signal at the first UL sTTI after an interval of 3 DL sTTI+0.5 msec from the transmission/reception timing of the sPDSCH.

By doing so, the base station 100 and the terminal 200 can secure processing delays in each device or time required for communication with upper layers.

[variation]
The base station 100 and the terminal 200 may define the timing of data allocation, data transmission/reception, and feedback (the transmission timing of the second signal with respect to the first signal) as follows.

Timing regarding DL data:
DL assignment in sPDCCH - sPDSCH : same sTTI
sPDSCH - ACK/NACK feedback : at least Max(X-1 DL sTTIs, Y msec) interval
Timing regarding UL data
UL grant in sPDCCH - sPUSCH : At least Max(X-1 DL sTTIs, Y msec) interval
sPUSCH - ACK/NACK feedback : at least Max(X-1 DL sTTIs, Y msec) interval

Note that Max(X-1 DL sTTIs, Y msec) selects the larger of X-1 DL sTTIs and Ymsec.

That is, the base station 100 and the terminal 200 transmit 2 UL sTTIs at the first UL sTTI after the greater of the predetermined number of DL sTTI intervals (X-1) and the absolute time Y has elapsed from the transmission/reception timing of the first signal. Send and receive the second signal.

In this way, if the sTTI length is longer than the absolute time Y, the sTTI length alone can secure the time required for processing delays in each device or for communication with upper layers, without setting the absolute time Y. Since the interval can be set using only the sTTI length, it is possible to avoid setting extra delays. Furthermore, when the sTTI length is shorter than the absolute time Y, sufficient time can be secured for processing delays in each device or for communication with upper layers.

(Embodiment 3)
The base station and terminal according to this embodiment have the same basic configuration as the base station 100 and terminal 200 according to Embodiment 1, so they will be explained with reference to FIGS. 4 and 5.

In the first and second embodiments, it is assumed that base station 100 and terminal 200 can use all sTTIs. However, the area used for conventional terminals (terminals that do not support sTTI), the PDCCH area used for common search space, CRS (Cell-specific Reference Signal), DMRS (Demodulation Reference Signal), CSI-RS Due to the arrangement of reference signals such as Channel State Information Reference Signal (Channel State Information Reference Signal) and SRS (Sounding Reference Signal), resources that can be used for transmitting and receiving data and control signals in the sTTI area decrease. Therefore, it is conceivable that the sTTI is not used for transmitting and receiving data and control signals, or that adjacent sTTIs are used together as one sTTI. Furthermore, since the amounts of control signals and reference signals are different between DL and UL, it is possible that the number of sTTIs is different.

Therefore, in this embodiment, a method of setting the timing of data allocation, data transmission/reception, and feedback when the usable sTTI differs for each subframe will be described.

The base station 100 and the terminal 200 use the subframe with the largest number of sTTIs as the reference subframe for DL, in which all sTTIs in a subframe can be used, and adjacent sTTIs are not combined into one sTTI. . Based on the DL sTTI length in the DL reference subframe, the transmission/reception timing of data allocation (UL grant in sPDCCH, DL assignment), data transmission/reception (sPUSCH, sPDSCH), and feedback (ACK/NACK signal) is determined.

Further, as in Embodiment 1, when the UL timing determined based on the DL sTTI length does not match the UL sTTI boundary, the base station 100 and the terminal 200 delay it until the timing matches the UL sTTI boundary.

Specifically, as in Embodiment 1, the base station 100 and the terminal 200 change the timing of data allocation, data transmission/reception, and feedback (the timing of transmission of the second signal relative to the first signal) as follows. stipulate.
Timing regarding DL data
DL assignment in sPDCCH - sPDSCH : same sTTI
sPDSCH - ACK/NACK feedback : after at least X DL sTTIs
Timing regarding UL data
UL grant in sPDCCH - sPUSCH : after at least X DL sTTIs
sPUSCH - ACK/NACK feedback : after at least X DL sTTIs

Note that "at least X DL sTTIs" means that the second signal (sPDSCH, ACK/NACK feedback, or This indicates that there is an interval of at least (X-1) sTTI before starting transmission/reception of sPUSCH or ACK/NACK feedback, and the second signal is assigned to the first sTTI after that interval.

Furthermore, in the present embodiment, the base station 100 performs a subframe in which the number of DL sTTIs that can be used for signal allocation is smaller than the subframe that serves as a DL reference, and a predetermined interval before the timing of receiving an uplink signal (sPUSCH). If the DL sTTI (timing specified above) cannot be used for signal allocation, the downlink signal (sPDCCH) is transmitted using the rearmost DL sTTI before the DL sTTI that cannot be used for signal allocation. Similarly, in a subframe in which the number of DL sTTIs that can be used for signal allocation is smaller than the reference subframe, the base station 100 assigns a DL sTTI (described above) after a predetermined interval from the timing of the UL sTTI at which the uplink signal (sPUSCH) is received. If the specified timing) cannot be used for signal allocation, an ACK/NACK signal for the uplink signal is transmitted at the first DL sTTI after the DL sTTI that cannot be used for signal allocation.

The operations of data allocation, data transmission/reception, and feedback in base station 100 and terminal 200 will be described in detail below.

[Operation example 3-1]
FIG. 17 shows an example of the transmission/reception timing between sPDCCH and sPUSCH in which a UL grant instructing transmission of a UL data signal (sPUSCH) is arranged, and the transmission/reception timing between sPUSCH and an ACK/NACK signal for the sPUSCH.

As shown in FIG. 17, similarly to operation example 1-2 of the first embodiment (see FIG. 7), the UL sTTI length is set to 3/4 symbols, the DL sTTI length is set to 2 symbols, and X=4. Furthermore, the base station 100 and the terminal 200 cannot use the sixth DL sTTI (DL sTTI #5, #12, #19, #26) of any subframe.

Regarding UL grant and sPUSCH, when X=4, in the subframe shown in operation example 1-2 (subframe serving as DL reference), sPUSCH transmitted at UL sTTI#5 is transmitted at the same timing as UL sTTI#5. It was allocated in the UL grant sent in DL sTTI#5, 3 DL sTTI intervals before DL sTTI#9. However, in FIG. 17, DLs TTI#5 cannot be used. Therefore, the base station 100 transmits a UL grant in DL sTTI#4, which is one before DL sTTI#5. Similarly, the base station 100 transmits the UL grant instructing the allocation of UL sTTI #9 and UL sTTI #13 to sPUSCH, which was scheduled to be transmitted in DL sTTI #12 and #19 shown in FIG. 17, to DL sTTI #11. , Send with #18.

Regarding sPUSCH and ACK/NACK signals, when X=4, in the subframe shown in operation example 1-2 (subframe that is the reference for DL), the ACK/NACK signal for sPUSCH of UL sTTI #4 is UL sTTI It was sent at DL sTTI#12, 3 DL sTTI intervals after DL sTTI#8 at the same timing as #4. However, in FIG. 17, DL sTTI #12 cannot be used. Therefore, the base station 100 delays the transmission timing of the ACK/NACK signal and transmits it at DL sTTI#13. Similarly, when X=4, in operation example 1-2, the ACK/NACK signal for sPUSCH of UL sTTI#8, #12 is DL sTTI#15, #22 at the same timing as UL sTTI#8, #12. It was sent in DL sTTI #19, #26 after 3 DL sTTI intervals. However, in FIG. 17, DL sTTI #19 and #26 cannot be used. Therefore, the base station 100 delays the transmission timing of the ACK/NACK signal and transmits it at DL sTTI #20 and #27.

Furthermore, in FIG. 17, the number of DL sTTIs is greater than the number of UL sTTIs, so even if some DL sTTIs cannot be used, the number of UL HARQ processes is not affected. However, if there are many unusable DL sTTIs, or if consecutive DL sTTIs cannot be used, the amount of delay will increase, so it is necessary to increase the number of UL HARQ processes.

[Operation example 3-2]
Operation example 3-2 describes the operation when the UL sTTI length and the DL sTTI length are the same.

FIG. 18 shows an example of the transmission/reception timing between sPDCCH and sPUSCH in which a UL grant instructing the transmission of a UL data signal (sPUSCH) is arranged, and the transmission/reception timing between sPUSCH and an ACK/NACK signal for the sPUSCH.

As shown in FIG. 18, both the UL sTTI length and the DL sTTI length are set to 3/4 symbols, and X=4. In other words, 1 subframe is divided into 4sTTI. Furthermore, the base station 100 and the terminal 200 cannot use the third DL sTTI (DL sTTI#2, #10, #18) of even-numbered subframes. In other words, the number of DL sTTIs that can be used for signal assignment using sTTI in even-numbered subframes is small compared to odd-numbered subframes (subframes that serve as DL standards).

If all DL sTTIs are available, the minimum number of UL HARQ process IDs is 8 for X=4. However, in operation example 3-2, some DL sTTIs cannot be used, which increases the delay of UL allocation and ACK/NACK feedback, so the minimum number of HARQ process IDs is 9.

Regarding UL grant and sPUSCH, when X=4, if all DL sTTIs can be used, sPUSCH transmitted in UL sTTI#6 is 3DL sTTI from DL sTTI#6 at the same timing as UL sTTI#6. It is allocated in the UL grant sent in DL sTTI#2 before the interval. However, in FIG. 18, DLs TTI#2 of subframe#0 cannot be used. Therefore, the base station 100 transmits a UL grant in DL sTTI#1, which is one before DL sTTI#2. Similarly, the base station 100 transmits the UL grant instructing the allocation of UL sTTI #14 and UL sTTI #22 to sPUSCH, which was scheduled to be transmitted in DL sTTI #10 and #18 shown in FIG. 18, to DL sTTI #9. , Send with #17.

Regarding the sPUSCH and ACK/NACK signals, when X=4, if all DL sTTIs can be used, the ACK/NACK signal for the sPUSCH of UL sTTI#6 is the DL signal with the same timing as UL sTTI#6. It was sent at DL sTTI #10 after 3 DL sTTI intervals from sTTI #6. However, in FIG. 18, DL sTTI #10 cannot be used. Therefore, the base station 100 delays the transmission timing of the ACK/NACK signal and transmits it at DL sTTI#11. Similarly, in the case of X=4, if all DL sTTIs can be used, the ACK/NACK signal for sPUSCH of UL sTTI#14 will be sent after 3DL sTTI intervals from DL sTTI#14 at the same timing as UL sTTI#14. It was sent in DL sTTI #18. However, in FIG. 18, DL sTTI #18 cannot be used. Therefore, the base station 100 delays the transmission timing of the ACK/NACK signal and transmits it at DL sTTI#19.

The operation example 3-1 and operation example 3-2 have been described above.

In this way, in the present embodiment, even if there is a DL sTTI to which no signal can be assigned within a DL subframe, the base station 100 and the terminal 200 use the DL sTTI as a reference in the same manner as in the first embodiment. determines data allocation, data transmission/reception, and feedback timing. Furthermore, if the determined DL timing is a DL sTTI to which the above signal cannot be allocated, the base station 100 and the terminal 200 transmit the DL signal (data signal or ACK/NACK signal) at a timing before or after the determined timing. Send.

As a result, even if the number of DL sTTIs differs between subframes, the base station 100 and the terminal 200 can start transmitting and receiving signals from the respective boundaries of DL sTTI and UL sTTI in the same manner as in Embodiment 1. . Therefore, according to the present embodiment, it is possible to appropriately set the timings of data allocation, data transmission/reception, and feedback when shortening the TTI length.

Note that if the first DL sTTI in the DL subframe cannot be used, PDCCH can be used instead. Since the base station 100 transmits the control signal and ACK/NACK signal assigned to sTTI on the PDCCH, no delay occurs, and therefore there is an advantage that the number of HARQ process IDs is not affected.

(Embodiment 4)
The base station and terminal according to this embodiment have the same basic configuration as the base station 100 and terminal 200 according to Embodiment 1, so they will be explained with reference to FIGS. 4 and 5.

When operating with the sTTI length, it may be possible to return to the normal TTI length due to reasons such as poor line quality or no need for latency reduction. Therefore, in this embodiment, the operation when switching from the sTTI length to the normal TTI length (1 subframe) will be described.

Possible methods for returning to the normal TTI include a method of allocating a normal TTI length using CSS (Common Search Space), or a method of instructing a change to the normal TTI length using the MAC layer. At this time, there are two ways to continue the HARQ process ID used in sTTI even in normal TTI and one not to continue it.

If the HARQ process ID is not to be continued, the base station 100 and the terminal 200 erase the signals in the HARQ buffer and start communication anew using all new data.

On the other hand, when continuing the HARQ process ID, in DL, the base station 100 instructs the terminal 200 to continue the HARQ process ID in a DL assignment with a normal TTI length.

Furthermore, in the case of UL, since the HARQ process ID is not notified to the terminal 200, the base station 100 and the terminal 200 need a mechanism to share the UL HARQ process ID between the sTTI and the normal TTI in advance. As a mechanism for sharing the UL HARQ process ID, the terminal 200 associates sTTI and TTI based on the subframe in which the TTI length switching is received.

FIG. 19 shows an example of operation for switching between sTTI and TTI in subframe #1.

In FIG. 19, sTTI is applied to subframe #0, and the terminal 200 detects UL grants of HARQ process IDs #0, #1, #2, and #3. It is also assumed that the terminal 200 detects a normal TTI UL grant on the PDCCH of subframe #1.

In this case, for HARQ process IDs #0, #1, #2, and #3 that operate using sTTI, the terminal 200 performs sPUSCH transmission processing using sTTI even in the UL of subframe #1. At this time, the base station 100 may transmit an ACK/NACK signal for sPUSCH transmitted in sTTI in subframe #2. Furthermore, if NACK is transmitted in subframe #1, terminal 200 can retransmit sPUSCH in subframe #3 (not shown). By doing so, it is possible to effectively utilize resources until PUSCH transmission switches to normal TTI.

Note that even if the base station 100 cancels the transmission of ACK/NACK signals in subframe #2, makes the terminal 200 recognize everything as ACK, and only allows adaptive retransmission using normal TTI. good.

In the first DL sTTI of Subframe #1, if sTTI operation continues, UL HARQ process ID #4 can be transmitted. Therefore, the terminal 200 recognizes that the UL grant with UL HARQ process ID #4 is transmitted on the PDCCH of subframe #1 using subframe #1 as a reference, and in accordance with the LTE/LTE-Advanced regulations, 4 subframes later (3 DL subframe Send PUSCH with HARQ process ID #4 in subframe #5 after the interval). Furthermore, the terminal 200 recognizes that the UL grant with HARQ process ID #5 has been transmitted in the PDCCH of the next subframe #2.

In this way, the base station 100 and the terminal 200 use sTTI in HARQ process IDs #0 to #3, and switch from sTTI to TTI after UL HARQ process ID #4. That is, the base station 100 and the terminal 200 use a common HARQ process ID when using sTTI (DL sTTI and UL sTTI) and when using TTI.

By doing so, even when switching from sTTI to normal TTI, base station 100 and terminal 200 can continue retransmission processing of UL data signals. Furthermore, since the base station 100 and the terminal 200 do not need to have double HARQ buffers for sTTI and TTI, the amount of buffers can be reduced.

Each embodiment of the present disclosure has been described above.

Note that although the above embodiment describes the timing of HARQ based on FDD, it is also applicable to the timing of HARQ based on TDD. When applying the present disclosure to the timing of HARQ based on TDD, bundling between subframes may be further applied.

Further, in the above embodiment, a case has been described in which the signal transmission/reception timing is determined based on the DL sTTI length, but the signal transmission/reception timing may be determined based on the ULsTTI length.

Furthermore, in the above embodiment, the explanation has been made assuming that X=4, but the value of X may be any other value.

Further, in the above embodiment, the transmission timing in UL is also adjusted by Timing Advanced (TA). Therefore, the actual UL transmission timing may be determined to start transmission earlier by a predetermined TA in addition to the timing specified in the above embodiment.

Further, in the first embodiment, it is limited that the UL grant is transmitted only from a specific DL sTTI, but the other embodiments are not limited to this. The UL grant may be transmitted at least X DL sTTI before the UL sTTI that can transmit PUSCH, and the UL grant for one UL sTTI may be transmitted from multiple DL sTTIs. In this case, the number of DL sTTIs for monitoring UL grants at terminal 200 increases, but there is an advantage that control signals can be easily distributed.

Furthermore, shortening the TTI length can be applied not only to systems that expand LTE, but also to systems implemented using a new frame format called New RAT (Radio Access Technology).

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

Furthermore, each functional block used in the description of the above embodiments is typically realized as an LSI, which is an integrated circuit having an input terminal and an output terminal. The integrated circuit may control each functional block used in the description of the above embodiments, and may include an input terminal and an output terminal. These may be integrated into one chip individually, or may be integrated into one chip including some or all of them. Although it is referred to as an LSI here, it may also be called an IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.

Further, the method of circuit integration is not limited to LSI, and may be implemented using 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 circuit cells inside the LSI may be used.

Furthermore, if an integrated circuit technology that replaces LSI emerges due to advancements in semiconductor technology or other derived technology, then of course the functional blocks may be integrated using that technology. Possibilities include the application of biotechnology.

The base station of the present disclosure includes a transmitting unit that transmits a downlink signal using the first sTTI (short TTI) of the downlink, which has a TTI length shorter than the TTI (Transmission Time Interval), and an uplink transmitter, which has the TTI length shorter than the TTI. a receiving unit that receives an uplink signal using a second sTTI of a line, and when the length of the first sTTI is shorter than the second sTTI, the receiving unit calculates the length of the first sTTI from the transmission timing of the downlink signal. The uplink signal is received at the second sTTI after a predetermined interval set as a reference.

In the base station of the present disclosure, the receiving unit receives the uplink signal at the first second sTTI after a predetermined number of first sTTIs from the transmission timing of the downlink signal.

In the base station of the present disclosure, the reception unit delays the reception timing of the uplink signal if the same timing after a predetermined number of first sTTI intervals from the transmission timing of the downlink signal does not coincide with the boundary of the second sTTI.

In the base station of the present disclosure, the downlink signal includes downlink allocation control information indicating the allocation of the downlink data signal, and the receiving unit receives the downlink data at the second sTTI after a predetermined interval from the timing of the first sTTI at which the downlink data signal was transmitted. Receive an ACK/NACK signal for the signal.

In the base station of the present disclosure, the downlink signal includes uplink allocation control information indicating allocation of the uplink signal, and the transmitting unit sends an ACK/ACK to the uplink signal at the first sTTI after a predetermined interval from the timing of the second sTTI when the uplink signal is received. Send NACK signal.

In the base station of the present disclosure, the first sTTI to which uplink allocation control information is transmitted is different from the first sTTI to which an ACK/NACK signal is transmitted.

In the base station of the present disclosure, the transmitting unit transmits the ACK/NACK signal to the first sTTI immediately before the first sTTI to which uplink allocation control information with the same HARQ process ID as the HARQ process ID of the ACK/NACK signal is transmitted. Send by.

In the base station of the present disclosure, the receiving unit receives ACK/NACK signals for each of the plurality of downlink signals transmitted in the same subframe at the plurality of second sTTIs in one subframe.

In the base station of the present disclosure, the receiving unit receives an uplink signal at the first second sTTI after a time period obtained by adding an absolute time to a predetermined number of first sTTI intervals from the transmission timing of the downlink signal.

In the base station of the present disclosure, the receiving unit receives the uplink signal at the first second sTTI after a predetermined number of first sTTI intervals and absolute time have elapsed from the transmission timing of the downlink signal.

In the base station of the present disclosure, the transmitting unit sets a predetermined interval based on the length of the first sTTI constituting the reference subframe, and the transmitting unit determines that the number of first sTTIs that can be used for signal allocation is longer than the reference subframe. If the first sTTI that is a predetermined interval before the timing of receiving an uplink signal cannot be used for signal allocation in a subframe with a small number of subframes, the downlink signal is transmitted using the rearmost first sTTI before the first sTTI that cannot be used for signal allocation. .

In the base station of the present disclosure, the downlink signal includes uplink allocation control information indicating allocation of uplink signals, and the transmitting unit sets a predetermined interval based on the length of the first sTTI that constitutes the reference subframe, and the transmitting unit In a subframe where the number of first sTTIs that can be used for signal allocation is smaller than the reference subframe, if the first sTTI after a predetermined interval from the timing of the second sTTI that received an uplink signal cannot be used for signal allocation, the signal An ACK/NACK signal for an uplink signal is transmitted at the first sTTI after the first sTTI that cannot be used for allocation.

In the base station of the present disclosure, the transmitting unit and the receiving unit use a common HARQ process ID when switching from using the first sTTI and the second sTTI to using the TTI.

The terminal of the present disclosure includes a receiving unit that receives a downlink signal using a first sTTI (short TTI) on the downlink, which has a TTI length shorter than the Transmission Time Interval (TTI), and an uplink signal, which has a TTI length shorter than the TTI. a transmitting unit configured to transmit an uplink signal using a second sTTI of The uplink signal is transmitted at the second sTTI after a predetermined interval set as .

The communication method of the present disclosure transmits a downlink signal using a downlink first sTTI (short TTI) with a TTI length shorter than the TTI (Transmission Time Interval), and an uplink first sTTI (short TTI) with a TTI length shorter than the TTI. When an uplink signal is received using 2sTTI and the length of the first sTTI is shorter than the second sTTI, the uplink signal is transmitted at the first sTTI after a predetermined interval set based on the length of the first sTTI from the transmission timing of the downlink signal. Received with 2s TTI.

The communication method of the present disclosure receives a downlink signal using a downlink first sTTI (short TTI) with a TTI length shorter than the TTI (Transmission Time Interval), and receives a downlink signal using an uplink first sTTI (short TTI) with a TTI length shorter than the TTI. When an uplink signal is transmitted using 2sTTI and the length of the first sTTI is shorter than the second sTTI, the uplink signal is transmitted at a predetermined interval after a predetermined interval set based on the length of the first sTTI from the reception timing of the downlink signal. Sent with 2sTTI.

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

100 base station 101 sTTI determination section 102 sPDCCH generation section 103, 209 error correction coding section 104, 210 modulation section 105, 211 signal allocation section 106, 212 transmission section 107, 201 reception section 108, 202 signal separation section 109 ACK/NACK Receiving section 110, 203 Demodulating section 111, 204 Error correction decoding section 112 ACK/NACK generating section 200 Terminal 205 sTTI setting section 206 Error determining section 207 ACK/NACK generating section 208 sPDCCH receiving section

Claims (10)

a transmitter that transmits a downlink signal to a terminal using a first sTTI (short Transmission Time Interval) shorter than one subframe;
a receiving unit that receives an uplink signal for the downlink signal transmitted from the terminal using a second sTTI that is shorter than the one subframe and longer than the first sTTI;
Equipped with
The receiving unit receives the uplink signal transmitted using the second sTTI after a predetermined number of times after the first sTTI from the transmission timing of the downlink signal, and receives the second sTTI after a predetermined number of the first sTTI from the transmission timing of the downlink signal. If the timing several times later does not match the boundary of the second sTTI, receiving the uplink signal transmitted using the first second sTTI after a predetermined number of times after the first sTTI;
the predetermined number is applied to all the first sTTIs within the one subframe;
base station. The downlink signal includes downlink control information indicating allocation of downlink data,
The uplink signal is an ACK/NACK signal for the downlink data,
The base station according to claim 1. The downlink signal includes downlink control information indicating allocation of the uplink signal,
The transmitting unit transmits an ACK/NACK signal for the upstream signal to the terminal using the first sTTI that is a predetermined number of times after the first sTTI from the second sTTI that received the upstream signal.
The base station according to claim 1. The transmitter transmits the ACK/NACK signal at the first sTTI that is immediately before the first sTTI to which the downlink control information having the same HARQ process ID as the HARQ process ID of the ACK/NACK signal is transmitted. ,
The base station according to claim 3. The receiving unit receives the uplink signal transmitted using the first second sTTI after adding an absolute time to the predetermined number of first sTTIs from the transmission timing of the downlink signal.
The base station according to claim 1. The receiving unit receives the uplink signal transmitted using the first second sTTI after the larger of the predetermined number of first sTTIs and absolute time from the transmission timing of the downlink signal.
The base station according to claim 1. The transmitting unit and the receiving unit use a common HARQ process ID when switching between using the first sTTI and the second sTTI and using the one subframe TTI, or continue using the HARQ process ID.
The base station according to claim 1. the predetermined number is set as a variable parameter between the base station and the terminal;
The base station according to claim 1. a transmission step of transmitting a downlink signal to a terminal using a first sTTI (short Transmission Time Interval) shorter than one subframe;
a receiving step of receiving an uplink signal for the downlink signal transmitted from the terminal using a second sTTI that is shorter than the one subframe and longer than the first sTTI;
Equipped with
The receiving step includes receiving the upstream signal transmitted using the second sTTI that is a predetermined number of times after the first sTTI from the transmission timing of the downlink signal, and using the second sTTI after a predetermined number of the first sTTI from the transmission timing of the downlink signal. If the timing several times later does not match the boundary of the second sTTI, receiving the uplink signal transmitted using the first second sTTI after a predetermined number of times after the first sTTI;
the predetermined number is applied to all the first sTTIs within the one subframe;
Communication method. A transmission process of transmitting a downlink signal to a terminal using a first sTTI (short Transmission Time Interval) shorter than one subframe;
a reception process of receiving an uplink signal for the downlink signal transmitted from the terminal using a second sTTI that is shorter than the one subframe and longer than the first sTTI;
control,
The receiving process includes receiving the upstream signal transmitted using the second sTTI that is a predetermined number of times after the first sTTI from the transmission timing of the downlink signal, and using the second sTTI after a predetermined number of the first sTTI from the transmission timing of the downlink signal. If the timing several times later does not match the boundary of the second sTTI, receiving the uplink signal transmitted using the first second sTTI after a predetermined number of times after the first sTTI;
the predetermined number is applied to all the first sTTIs within the one subframe;
integrated circuit.

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