CN112738845A

CN112738845A - Design method for one-trigger indication of HARQ feedback in NR-U system

Info

Publication number: CN112738845A
Application number: CN202011521522.8A
Authority: CN
Inventors: 李勇; 卢依一; 李俊丽
Original assignee: Beijing University of Posts and Telecommunications
Current assignee: Beijing University of Posts and Telecommunications
Priority date: 2020-12-21
Filing date: 2020-12-21
Publication date: 2021-04-30
Anticipated expiration: 2040-12-21
Also published as: CN112738845B

Abstract

The invention discloses a design method of one-trigger indication for HARQ feedback in an NR-U system, which comprises the following steps: adding a 2bit state bit in the one-shot DCI; and judging whether the base station side successfully receives the last HARQ feedback of the same HARQ process according to the definition of the state bit. The invention relates to a design method of single-trigger indication for HARQ feedback in an NR-U system, which solves the problem of data block loss by adding 2 bits in single-trigger DCI as a state bit of whether the last HARQ feedback of the same HARQ process is successfully received or not on a base station side.

Description

Design method for one-trigger indication of HARQ feedback in NR-U system

Technical Field

The invention relates to the technical field of mobile communication, in particular to a design method of one-trigger indication for HARQ feedback in an NR-U system.

Background

The mobile data traffic is increased explosively, the urgent demand of the wireless communication system for the spectrum resources is more and more intense, and therefore, 3GPP actively seeks an application deployment scheme of new technologies such as 5G on unlicensed spectrum. RAN-75 conferences of 3 months in 2017 proposed a study plan for NR-based unlicensed bands (NR-U), and the study was started in early 2018.

An important issue for deploying NR on unlicensed spectrum is to ensure fair coexistence with other Radio Access Technologies (RATs) using this frequency band, for which NR-U uses a "listen before talk" channel access mechanism (LBT), and the gNB/UE must first monitor whether the channel is occupied before communicating, and satisfy certain conditions for successful LBT.

When HARQ feedback is transmitted on an unlicensed band, unpredictable HARQ feedback delay is brought due to uncertainty of LBT result, and a hidden node problem may cause HARQ feedback failure, in order to provide multiple HARQ transmission opportunities, 3GPP RAN1#98b conference has agreed to support a protocol in which a base station requests one-shot group HARQ feedback for all HARQ processes that were previously configured and failed in feedback. In NR-U, the gNB may send a one-shot request to the UE instructing the UE to report feedback for all configured HARQ processes.

If the user receives the one-shot indication more than once, the corresponding HARQ feedback information needs to be transmitted for multiple times, and at this time, it is difficult for the base station to distinguish whether the HARQ feedback information is initially transmitted or retransmitted, and the problem of NACK-to-ACK conversion of newly transmitted data may be caused.

As shown in fig. 1, a base station sends PDSCH TB1 HARQ process X, a user sends ACK after correct reception and is correctly received by the base station, the base station sends new TB2 using the same HARQ process X, but the user does not receive PDSCH TB2 HARQ X due to interference of a hidden node, so the user does not operate, because the base station does not receive HARQ feedback of PDSCH TB2 HARQ process X, the user sends a One-shot request (One-shot trigger) to indicate that the user feeds back to process X, after receiving the One-shot request, the user mistakenly considers that HARQ feedback of the last transmission is not successfully received by the base station, so the user retransmits the feedback ACK of TB1 to the base station, and after receiving the single-shot request, the base station mistakenly considers that TB2 is successfully received by the user, and finally causes loss of a TB2 data block.

In view of the above problems, the existing solutions have disadvantages.

The existing solution is that the user adopts a default NACK mechanism, and the NDI value is not reported together with the HARQ-ACK of the corresponding PDSCH, and this scheme requires that once ACK is reported for the same HARQ process ID in the previous HARQ feedback, the UE resets the HARQ state of the HARQ process to NACK, which has the disadvantage that the same ACK multiple transmission is not supported, and therefore the ACK-to-NACK problem may be caused, as shown in fig. 2:

when the data TB1 primarily transmitted by the gNB is correctly received by the user, the corresponding HARQ feedback fails to be received at the base station due to hidden node or burst interference, and the base station uses the one-trigger HARQ mechanism to trigger feedback, because the user uses the default NACK mechanism, the user reports NACK to the base station when receiving the one-trigger request, so that the correctly received data at the user side is understood as erroneously received by the base station, and therefore the base station retransmits the correctly received data packet TB1, which may cause waste of unauthorized spectrum resources.

The second existing solution is that the UE reports the xor result of the latest NDI value of the corresponding PDSCH and the HARQ-ACK (if there is no previous NDI value for the HARQ process, the UE assumes that NDI is 0), which is a disadvantage of this scheme is that when a certain TB is transmitted for multiple times and is still not correctly received by the user, and the base station is ready to transmit the next new TB, if the new TB is received incorrectly or is lost at the user side, after receiving the one-shot request of the base station, the xor result of the previous TB is sent to the base station, and the base station uses the xor mechanism to decode, which causes the NACK-to-ACK problem that the new TB is mistakenly received correctly, as shown in table 1:

table 1 schematic table of the second prior art solution for the problem of NACK to ACK

When TB1 still fails to transmit for multiple times, the base station uses the same HARQ process to schedule the transmission of the newly transmitted data block, but the user does not receive TB2 and does not perform HARQ feedback on TB2 due to interference of hidden nodes, when the base station uses a one-shot mechanism to request the user to perform HARQ feedback again, the user will consider that the xor HARQ result of the last retransmission of TB1 is not successfully transmitted, so 0 is fed back to the base station again, and the base station will perform xor decoding (shown by a circle) on the NDI value 1 of TB2 after receiving the xor HARQ result to obtain a result of 1, which considers that TB2 is successfully received, but actually TB2 fails to receive, resulting in NACK-to-ACK problem, and causing the loss of newly transmitted data.

The third existing solution is that the user reports the latest NDI value and HARQ a/N of the corresponding HARQ process ID (if there is no previous NDI value for this HARQ process, the UE assumes NDI ═ 0), which has the disadvantage of significantly increasing the overhead of the relevant UCI, for example, when non-CBG-based HARQ (i.e. TB level) feedback is reported, the UCI size is basically doubled, and due to the uncertainty of the unlicensed spectrum LBT result, a one-trigger HARQ feedback mechanism may be frequently used, so if the overhead of the relevant UCI is doubled, it will have a certain impact on the detection at the base station side.

Based on the above technical problems in the prior art, the present invention provides a one-shot indication design method for HARQ feedback in an NR-U system.

Disclosure of Invention

In order to solve the technical problems in the prior art, the invention provides a one-shot indication design method for HARQ feedback in an NR-U system.

The invention adopts the following technical scheme:

the invention provides a one-shot indication design method for HARQ feedback in an NR-U system, which comprises the following steps: adding a 2bit state bit in the one-shot DCI; and judging whether the last HARQ feedback reception aiming at the same HARQ process of the base station end is successful or not according to the definition of the state bit.

Further, the length of the control information of the one-shot request can be increased, and 2-bit state bits are added to the control information.

Further, the control information of the one-shot request is carried in DCI format 1_ 1.

Further, the length of the control information of the one-shot request cannot be increased, and the status bit is carried by 2 bits in the control information of the PDSCH without scheduling.

Further, when the length of the control information of the one-shot request cannot be increased, the status bit is specifically carried by the following steps:

s1.1, triggering a feedback request by control information of a single-trigger request, and adopting control information of a PDSCH (physical Downlink shared channel) which is not scheduled to bear a newly-added state bit field;

s1.2, setting the frequency domain resource allocation field of the control information of the PDSCH which is not scheduled to be all 0 or all 1, and setting fields of MCS, NDI and RV to be reserved state;

s1.3, enabling the 2bit of the reserved state to be used for bearing the state bit.

Further, when the base station sends the one-shot request of the HARQ process, the state bit is set to a corresponding value to notify the UE according to whether the last HARQ feedback of the HARQ process is successfully received.

Further, at the UE side, when receiving the one-shot request, the UE side checks the set value of the status bit to determine whether the feedback expected by the base station side is the last HARQ feedback or the HARQ feedback of the newly transmitted TB.

Preferably, the status bits are denoted as HFRI (HARQ feedback indication), and the meaning of the status bits is defined as follows:

when HFRI is 00, the value is a default value;

when the HFRI is 01, it indicates that the last HARQ feedback of the same HARQ process was successfully received;

when the HFRI is 10, it indicates that the last HARQ feedback reception of the same HARQ process failed;

when HFRI is 11, this value is temporarily undefined.

Preferably, the determining whether the last HARQ feedback reception for the same HARQ process by the base station is successful includes:

s2.1, the base station sends a PDSCH TB1 HARQ process X;

s2.2, after correctly receiving the PDSCH TB1 HARQ process X, the UE sends ACK and is correctly received by the base station;

s2.3, the base station adopts the HARQ process same as the S2.1 to send a new TB 2;

s2.4, if the base station does not receive the feedback of the PDSCH TB2 HARQ process X, the base station sends a one-shot request to the UE to indicate that the HFRI field is set to 01 to inform the UE when the user feeds back the process X, and the base station end successfully receives the feedback of the TB1 of the HARQ process X;

s2.5, the UE carries out HARQ feedback on the TB of the process X after receiving the one-shot request, the UE knows that the last feedback of the process X is successfully received by the base station end according to the value of the HFRI field, the current trigger feedback is the feedback aiming at the newly transmitted TB of the same process X, the UE does not receive the newly transmitted TB from the same HARQ process X, the current feedback is set to be NACK feedback to the base station end, the base station end learns that the TB2 of the process X fails to receive after receiving the HARQ feedback, and the retransmission TB2 is carried out.

s3.1, the base station sends a PDSCH TB1 HARQ process X, and the retransmission of the TB1 exceeding the maximum retransmission times still fails, wherein the maximum retransmission times are configured by an RRC high layer;

s3.2, the base station adopts the HARQ process which is the same as the S3.1 to schedule the new data block TB2 for transmission;

s3.3, if the UE does not receive TB2, the UE does not perform HARQ feedback on TB 2;

s3.4, when the base station triggers the UE to perform HARQ feedback again by adopting a one-trigger mechanism, the HFRI is set to be 01 so as to indicate that the HARQ feedback of the last TB of the same HARQ process is successfully received;

s3.5, after receiving the trigger request in S3.4, the UE learns that the feedback base station of the last TB of the same HARQ process has successfully received the request according to the value of HFRI, and the trigger is a newly transmitted TB for the process;

and S3.6, the user sends the result 1 after the XOR to the base station, the base station end also carries out the XOR operation, the XOR operation result of the received 1 and the NDI value 1 is 0, and the base station retransmits the TB 2.

Compared with the prior art, the invention has the following advantages:

the invention relates to a design method of single-trigger indication for HARQ feedback in an NR-U system, which solves the problem of data block loss by adding 2 bits in single-trigger DCI as a state bit of whether the last HARQ feedback of the same HARQ process is successfully received or not by a base station end.

Drawings

FIG. 1 is a diagram illustrating a single trigger indicating that there is a NACK to ACK problem with newly transmitted data in the prior art;

fig. 2 is a diagram illustrating an ACK to NACK problem in a first prior art solution;

fig. 3 is a schematic diagram illustrating that setting the HFRI field in embodiment 1 of the present invention solves the NACK-to-ACK problem in fig. 1;

fig. 4 is a schematic diagram illustrating that setting the HFRI field in embodiment 2 of the present invention solves the ACK-to-NACK problem in fig. 2;

FIG. 5 is a diagram illustrating the NACK to ACK problem in an extended scenario in the prior art;

fig. 6 is a schematic diagram illustrating setting of HFRI field in embodiment 4 to solve the NACK-to-ACK problem in fig. 5.

Detailed Description

In order that the above objects, features and advantages of the present invention can be more clearly understood, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments, it being understood that the embodiments and features of the embodiments of the present application can be combined with each other without conflict.

The one-shot indication design method for HARQ feedback in the NR-U system comprises the following steps: adding a 2bit state bit in the one-shot DCI; and judging whether the last HARQ feedback reception aiming at the same HARQ process of the base station end is successful or not according to the definition of the state bit.

When the length of the control information of the one-shot request cannot be increased, the status bit is carried by 2 bits in the control information of the PDSCH without scheduling, and the status bit is carried by the following steps:

s1.2, setting a frequency domain resource allocation field of control information of a PDSCH (physical downlink shared channel) not to be scheduled to be all 0 or all 1, and setting an MCS (modulation and coding scheme) modulation and coding scheme, an NDI (data new indicator) and an RV (redundancy version) field to be in a reserved state;

And when the base station end sends the one-shot request of the HARQ process, the state bit is set to a corresponding value to inform the UE according to whether the last HARQ feedback of the HARQ process is successfully received.

And when the UE end receives the one-shot request, checking the set value of the state bit to determine whether the feedback expected by the base station end is the last HARQ feedback or the newly transmitted TB HARQ feedback.

The length of the control information of the one-shot request can be increased, and 2-bit state bits are added to the control information.

Here, the status bit is denoted as HFRI (HARQ feedback indication), and the meaning of the status bit is defined as follows:

when HFRI is 00, the value is a default value, and at this time, no scene is represented;

when HFRI is 11, this value is temporarily undefined and is convenient to expand later.

Example 1

In this embodiment, for the problem that NACK to ACK of newly transmitted data exists in a single trigger request in the prior art, as shown in fig. 1, the following technical solution is used to solve the problem:

as shown in fig. 3, the base station sends PDSCH TB1 HARQ process X, the user sends ACK after receiving correctly and is received correctly by the base station, the base station sends new TB2 using the same HARQ process, but the user does not receive PDSCH TB2 due to hidden node interference, so the UE does not perform feedback operation, because the base station does not receive feedback of PDSCH TB2 HARQ process X, the base station sends a one-shot request to the UE to instruct the user to perform feedback on process X, and because the base station knows that the feedback of TB1 of process X has been successfully received, the base station sets HFRI field to 01 to inform the UE that the base station has successfully received feedback of TB1 of HARQ process X, the UE needs to perform HARQ feedback on TB of process X after receiving the one-shot request, and according to the value of HFRI field, the UE knows that the last feedback base station of process X has been successfully received, so this-time trigger feedback is feedback for new TB of the same process X, because the UE does not receive the newly transmitted TB from the same HARQ process X, the feedback is set as NACK feedback to the base station, and the base station considers that the reception of TB2 of process X fails after receiving the HARQ feedback, and then retransmits TB 2.

In the above embodiment, the problem of NACK/DTX to ACK in the above scenario in the prior art can be avoided.

Example 2

In this embodiment, as shown in fig. 2, for the problem of ACK to NACK in a single trigger request in the prior art, the following technical solutions are used to solve the problem:

as shown in fig. 4, when the base station correctly receives data TB1 sent in process X by the UE, and its corresponding HARQ feedback fails to be received at the base station due to interference of a hidden node, and the base station uses the one-shot HARQ feedback request, because the feedback from the UE to TB1 of process X is not correctly received, setting the HFRI field in the one-shot feedback DCI to 10 indicates that the base station fails to receive the HARQ feedback, and the UE knows that the HARQ feedback of TB1 of process X that has been transmitted is not correctly received by the base station according to the meaning indicated by the HFRI after receiving the DCI, and thus needs to retransmit the HARQ feedback corresponding to the process once. Therefore, repeated transmission of the data packet in the unauthorized frequency band is avoided, the resource utilization rate is improved, and the transmission delay of the data packet is reduced to a certain extent.

Example 3

In this embodiment, for the problem of converting new data NACK to ACK in the prior art, as shown in table 1, the following technical solutions are used to solve the problem:

as shown in table 2:

table 2 schematic table for setting HFRI field to solve NACK to ACK conversion problem in Table 1

When retransmission of TB1 still fails for multiple times, the base station uses the same HARQ process to schedule transmission of a new data block TB2, but the UE fails to receive TB2 due to interference of hidden nodes and does not perform HARQ feedback on TB2, when the base station uses a one-shot mechanism to trigger the UE to perform HARQ feedback again, setting HFRI in trigger DCI to 01 to indicate that HARQ feedback of the previous TB of the same HARQ process has been successfully received, after receiving the trigger request, the UE knows that the feedback base station of the previous TB of the same HARQ process has been successfully received according to the value of HFRI, the trigger is a new TB for the process, and therefore the new data is transmitted, that is, NDI is 1 (shown in TB2 new transmission grey cell), but since the user does not receive the new data, the HARQ feedback value of the new data is 0(NACK), the xor operation is performed on the base station side, and the xor operation result of the received 1 and the NDI value 1 is 0 (shown in grey cell after one-shot), the base station retransmits TB 2.

Example 4

In this embodiment, for ambiguity appearing in an extended scene, the following technical solution is used to solve the ambiguity:

as shown in fig. 5, when TB1 data of process X transmitted for the first time is correctly received by the UE, and its corresponding HARQ feedback causes ACK to be unsuccessfully transmitted to the base station side due to hidden node interference, according to the Rel-15 HARQ order, "the UE does not expect to receive another PDSCH in a given HARQ process before the HARQ-ACK of the HARQ process is expected to end", but the process can be scheduled after slot n, if the UE misses new transmission TB2 of the same process after slot n and the base station triggers one HARQ feedback without NDI, the UE reports ACK of process TB1, which may cause a possibility problem that new transmission TB2 NACK is changed to ACK.

As shown in fig. 6, in the embodiment, by setting the HFRI field to 10 (because HARQ feedback of TB1 of the same process is not received), the UE knows that the base station has sent new data after receiving the HARQ feedback, and feeds back NACK to the base station because it has not received the new data, thereby avoiding the occurrence of switching NACK to ACK for the new data.

The present invention is not limited to the above-described embodiments, which are described in the specification and illustrated only for illustrating the principle of the present invention, but various changes and modifications may be made within the scope of the present invention as claimed without departing from the spirit and scope of the present invention. The scope of the invention is defined by the appended claims.

Claims

1. A design method of one-shot indication for HARQ feedback in an NR-U system is characterized by comprising the following steps: adding a 2bit state bit in the one-shot DCI; and judging whether the last HARQ feedback reception aiming at the same HARQ process of the base station end is successful or not according to the definition of the state bit.

2. The NR-U system of claim 1, wherein the length of the control information of the one-shot request can be increased, and 2-bit status bits are added to the control information.

3. The method of claim 1, wherein the length of the control information of the one-shot request cannot be increased, and the status bits are carried by 2 bits of the control information of the PDSCH without scheduling.

4. The method of claim 3, wherein when the length of the control information of the one-shot request cannot be increased, the method specifically carries the status bit by the following steps:

s1.2, setting the frequency domain resource allocation field of the control information of the PDSCH which is not scheduled to be all 0 or all 1, and setting fields of MCS, NDI and RV to be reserved;

5. The NR-U system of claim 1, wherein when the base station sends the one-shot request of the HARQ process, the base station sets the status bit to a corresponding value to inform the UE of the successful reception of the last HARQ feedback of the HARQ process.

6. The NR-U system of claim 1, wherein when the UE receives the one-shot request, the UE checks the value of the status bit setting to determine whether the feedback expected by the base station is the last HARQ feedback or the newly transmitted TB HARQ feedback.

7. The method of any of claims 1-6, wherein the status bits are denoted as HFRI, and the meaning of the status bits is defined as follows:

when HFRI is 00, the value is a default value;

when HFRI is 11, this value is temporarily undefined.

8. The method of claim 1, wherein the determining whether the last HARQ feedback reception of the base station for the same HARQ process is successful comprises:

s2.1, the base station sends a PDSCH TB1 HARQ process X;

9. The method of claim 1, wherein the determining whether the last HARQ feedback reception of the base station for the same HARQ process is successful comprises: