SPS PDSCH的HARQ反馈

R15 SPS HARQ反馈规则 38.213 9.1

General

UE在同一PUCCH中只期待被指示发送1个SPS PDSCH的HARQ-ACK信息，并且只为该PDSCH生成1bit HARQ-ACK信息。
If a UE receives a PDSCH without receiving a corresponding PDCCH, or if the UE receives a PDCCH indicating a SPS PDSCH release, the UE generates one corresponding HARQ-ACK information bit (only for the TB in the PDSCH). A UE does not expect to be indicated to transmit HARQ-ACK information for more than two SPS PDSCH receptions in a same PUCCH.

Only HARQ-ACK feedback for SPS PDSCHs shall be reported

根据激活DCI中配置的K1值，确定反馈时隙。根据SPS-Config中的n1PUCCH-AN参数确定反馈资源。
n1PUCCH-AN（PUCCH-ResourceId）：HARQ resource for PUCCH for DL SPS. The network configures the resource either as format0 or format1.

SPS HARQ-ACK is multiplexed with dynamic HARQ

对于半静态码本，根据激活DCI中配置的K1值，确定反馈时隙，以及根据反馈时机确定在码本中的位置。若预留的反馈比特数大于1，则UE将对应的HARQ-ACK信息重复多次，直至充满预留比特位。
对于动态码本，SPS HARQ-ACK比特被添加在码本尾部，多个小区的反馈信息按照serving cell index的升序排列。

R16 agreement for SPS HARQ feedback

Only HARQ-ACK feedback for SPS PDSCHs shall be reported

对于只有SPS HARQ-ACK进行反馈的情况：
与R15相比，为支持多SPS配置，R16支持更多比特的反馈，也因此支持PF2/3/4。通过RRC为所有SPS配置共同配置了至多4个PUCCH资源，且每个资源所能承载的载荷大小依次升高。UE基于HARQ-ACK有效载荷大小来确定要使用的实际PUCCH资源。多个SPS配置的反馈码本按照DL slot, SPS configuration index, serving cell index的升序排列。

• Support more than one bit of HARQ-ACK feedback for SPS PDSCH without an associated grant in a PUCCH resource
• PUCCH formats 2/3/4 are applicable in addition to PUCCH formats 0/1.
• Multiple PUCCH resources are configured common for all SPS configurations per HARQ-ACK codebook. The actual PUCCH resource to be used among PUCCH resources is determined based on HARQ-ACK payload size
  • Number of PUCCH resources is up to 4
  • FFS details (e.g., threshold for determining PUCCH resource)
• PUCCH resource i is selected if HARQ-ACK payload size (not including CRC) is in the range of {Ni,min, …, Ni,max} bits, where the number of PUCCH resources in the selection is from 0 up to 3.
  • N0,min=1, N0,max=2
  • For i≠0
    • Ni,max is configured by RRC; if not configured, Ni,max is 1706.
    • Ni,min is equal to Ni-1,max+1
  • Note: The above mechanism is equivalent to rel-15 procedure when a single PUCCH resource is configured per PUCCH resource set.
• The number of PRBs for the PUCCH transmission is determined by reusing rel-15 mechanism in Subclause 9.2.3 (UE procedure for reporting HARQ-ACK) of 38.213.
• The maximum code rate per PUCCH format is reused from the parameter associated with the identified HARQ-ACK codebook for SPS PDSCH
• HARQ-ACK bit order for SPS PDSCH reception without a corresponding PDCCH is determined
  • In ascending order of DL slot per {SPS configuration index, serving cell index}, and then in ascending order of SPS configuration index per {serving cell index}, and then in ascending order of serving cell index

SPS HARQ-ACK is multiplexed with dynamic HARQ

对于与动态调度码本进行复用的情况：
本质上重用R15 rule。对于半静态码本，根据联合释放DCI中SPS配置索引最低的SPS PDSCH激活DCI中指示的TDRA行索引以及释放DCI中指示的K1，得出其HARQ-ACK位的位置。对于动态码本，SPS HARQ-ACK比特被添加在码本尾部，多个SPS配置的反馈码本按照DL slot, SPS configuration index, serving cell index的升序排列。

• The PUCCH resource to be used is determined by reusing rel-15 mechanism.
• For type-1 HARQ-ACK codebook construction,
  • For cases where HARQ-ACK feedback for one or more SPS PDSCH receptions without a corresponding PDCCH is multiplexed with HARQ-ACK feedback for dynamic scheduled PDSCH and/or for SPS PDSCH release, or
  • For cases where HARQ-ACK feedback for SPS PDSCH release is multiplexed with HARQ-ACK feedback for dynamic scheduled PDSCH, or
  • For cases where only HARQ-ACK feedback for SPS PDSCH release shall be reported,
    • HARQ-ACK bit location for SPS PDSCH reception is derived by reusing Rel-15 mechanism (i.e., based on the TDRA table row index and K1 indicated in the activation DCI)
    • HARQ-ACK bit location for SPS PDSCH release with a separate release DCI is derived by reusing Rel-15 mechanism (i.e., based on the TDRA table row index indicated in the activation DCI and K1 indicated in the release DCI)
    • HARQ-ACK bit location for SPS PDSCH release with a joint release DCI is derived based on the TDRA table row index indicated in the activation DCI for SPS PDSCH with the lowest SPS configuration index among the jointly released configurations and K1 indicated in the release DCI
  • Note: There is no change on the number of HARQ-ACK bits for a PUCCH transmission regardless whether a joint release DCI is present or not.
• For type-2 HARQ-ACK codebook construction,
  • HARQ-ACK bit order for SPS PDSCH release with a separate/joint release DCI is derived by reusing rel-15 mechanism (i.e., based on DAI and K1 indicated in the release DCI)
  • HARQ-ACK bit order for SPS PDSCH with associated PDCCH is derived by reusing rel-15 mechanism (i.e., based on DAI and K1 indicated in the activation DCI)
  • For cases where HARQ-ACK feedback for one or more SPS PDSCH receptions without a corresponding PDCCH is multiplexed with HARQ-ACK feedback for dynamic scheduled PDSCH and/or for SPS PDSCH release,
    • HARQ-ACK for one or more SPS PDSCH receptions without a corresponding PDCCH is appended after HARQ-ACK bits for dynamic scheduled PDSCHs and/or for SPS PDSCH release
      In ascending order of DL slot per {SPS configuration index, serving cell index}, and then in ascending order of SPS configuration index per {serving cell index}, and then in ascending order of serving cell index

Activation and Release for multiple SPS configurations

不支持联合激活，支持联合释放。对于联合释放DCI，只生成1位HARQ比特进行反馈。并且联合释放的多个SPS配置应具有相同的优先级。

• Support DCI format 1-0, 1-1 and 1_2 for Rel-16 SPS activation and for Rel-16 SPS release.
• HPN field in the applicable DL DCI formats with CRC scrambled by CS-RNTI and NDI=0 is used to indicate which SPS configuration is to be activated and which SPS configuration(s) is/are to be released
  • M LSB HPN bits is used to indicate which configuration is to be activated and which configuration(s) is/are to be released.
  • M is determined by the bit length for HPN field for each DCI format for activation and release of SPS configuration(s)
• There is no consensus to support joint activation in a DCI for two or more SPS configurations for a given BWP of a serving cell in rel-16.
• Support joint release in a DCI for two or more SPS configurations for a given BWP of a serving cell
  • Reusing the joint release mechanism as that defined for UL type 2 CG
• For both type-1 and type-2 HARQ-ACK codebook construction, one HARQ-ACK bit is generated for SPS PDSCH release with a joint release DCI
• In Rel-16, when the SPS configurations are released by a joint release DCI, Multiple SPS configurations to be released by the joint release DCI should have the same priority.

Collision handling

• For a rel-16 UE provided by SPS-PUCCH-AN-List a set of PUCCH resources, in case of collision between HARQ-ACK for SPS PDSCH without a corresponding PDCCH and SR for the same priority, reuse Rel-15 rule for collision between HARQ-ACK for dynamic scheduled PDSCH and SR in order to determine the PUCCH resource
• For a UE not indicating a capability to receive more than one unicast PDSCH per slot, in a slot with more than one SPS PDSCHs each without a corresponding PDCCH and no dynamic scheduled PDSCH and/or SPS PDSCH release, a UE is not required to receive SPS PDSCHs other than the SPS PDSCH with the lowest SPS configuration index among SPS PDSCHs in a slot (regardless of whether SPS PDSCHs are overlapped or not).
  • The UE shall report HARQ-ACK feedback only for the SPS PDSCH with the lowest SPS configuration index among SPS PDSCHs in the slot.
• In case of collision in time domain among SPS PDSCHs each without a corresponding PDCCH after excluding SPS PDSCHs overlapping semi-static UL symbols,
  • A UE receives and decodes one or more of SPS PDSCHs within a group of overlapping SPS PDSCHs on the same serving cell according to the following procedure.
    • Step 0: set j=0-number of selected PDSCH for decoding. Set Q to set of activated SPS PDSCHs within a slot
    • Step 1: A UE receives and decodes one of SPS PDSCHs with the lowest SPS configuration index within Q, set j=j+1. Designate the received SPS PDSCH as survivor SPS PDSCH.
    • Step 2: The survivor SPS PDSCH in step 1 and any other SPS PDSCH(s) overlapping (even partially) with the survivor SPS PDSCH in step 1 are excluded from Q.
    • Step 3: Repeat step 1 and 2 until the group is empty or j≥N, where N is the number of unicast PDSCHs in a slot supported by the UE

General

• There is no consensus on support of DL SPS periodicity shorter than 1 slot in Rel-16.
• In Rel-16, multiple DL SPS configurations can be configured on different serving cells in a cell group.

Multiple Active Configured Grant Configurations

Use Case

• Use case 1: Support different service/traffic types with different requirements on latency, reliability, packet size etc., running simultaneously at the UE side;
  
  

• Use case 2: To ensure K repetitions without sacrificing the latency for a given URLLC service, similar as multiple UL SPS configurations supported in LTE HRLLC. The main features for use case 2 are following:

  • The multiple configured grant configurations have the same periodicity but can have different time offsets
  • UE should start PUSCH transmission at the beginning of a first repetition of a transmission occasion of a configured grant configuration and continue K times repetition.
    

• Use case 3: R2 assumes short SPS/CG periodicities and/or multiple SPS/CG configurations and/or combination thereof could be used to mitigate the periodicity misalignment between the TSN periodicity and CG/SPS periodicity. Other solutions not precluded, e.g. to address resource consumption.

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