Content for  TS 38.321  Word version:  18.3.0

The Enhanced SP/AP SRS Spatial Relation Indication MAC CE is identified by a MAC subheader with eLCID as specified in Table 6.2.1-1b. It has a variable size with following fields:

• A/D: This field indicates whether to activate or deactivate indicated SP SRS resource set. The field is set to 1 to indicate activation, otherwise it indicates deactivation. If the indicated SRS resource set ID is for the AP SRS resource set, MAC entity shall ignore this field;
• SRS Resource Set's Cell ID: This field indicates the identity of the Serving Cell, which contains the indicated SP/AP SRS Resource Set. If the C field is set to 0, this field also indicates the identity of the Serving Cell which contains all resources indicated by the Resource ID_i fields. The length of the field is 5 bits;
• SRS Resource Set's BWP ID: This field indicates a UL BWP as the codepoint of the DCI bandwidth part indicator field as specified in TS 38.212, which contains the indicated SP/AP SRS Resource Set. If the C field is set to 0, this field also indicates the identity of the BWP which contains all resources indicated by the Resource ID_i fields. The length of the field is 2 bits;
• C: This field indicates whether the octets containing Resource Serving Cell ID field(s) and Resource BWP ID field(s) are present. If this field is set to 1, Resource Serving Cell ID field(s) and Resource BWP ID field(s) are present, otherwise they are not present so MAC entity shall ignore Resource Serving Cell ID field(s) and Resource BWP ID field(s);
• SUL: This field indicates whether the MAC CE applies to the NUL carrier or SUL carrier configuration. This field is set to 1 to indicate that it applies to the SUL carrier configuration, and it is set to 0 to indicate that it applies to the NUL carrier configuration;
• SRS Resource Set ID: This field indicates the SP/AP SRS Resource Set ID identified by SRS-ResourceSetId as specified in TS 38.331. The length of the field is 4 bits;
• F_i: This field indicates the type of a resource used as a spatial relationship for SRS resource within SP/AP SRS Resource Set indicated with SP/AP SRS Resource Set ID field. F₀ refers to the first SRS resource within the resource set, F₁ to the second one and so on. The field is set to 1 to indicate NZP CSI-RS resource index is used, and it is set to 0 to indicate either SSB index or SRS resource index is used. The length of the field is 1 bit. This field is only present if MAC CE is used for activation of SP SRS resource set, i.e. the A/D field is set to 1, or for AP SRS resource set;
• Resource Serving Cell ID_i: This field indicates the identity of the Serving Cell on which the resource used for spatial relationship derivation for SRS resource i is located. The length of the field is 5 bits;
• Resource BWP ID_i: This field indicates a UL BWP as the codepoint of the DCI bandwidth part indicator field as specified in TS 38.212, on which the resource used for spatial relationship derivation for SRS resource i is located. The length of the field is 2 bits;
• Resource ID_i: This field contains an identifier of the resource used for spatial relationship derivation for SRS resource i. Resource ID₀ refers to the first SRS resource within the resource set, Resource ID₁ to the second one and so on. If F_i is set to 0, the first bit of this field is always set to 0. If F_i is set to 0, and the second bit of this field is set to 1, the remainder of this field contains SSB-Index as specified in TS 38.331. If F_i is set to 0, and the second bit of this field is set to 0, the remainder of this field contains SRS-ResourceId as specified in TS 38.331. The length of the field is 8 bits. This field is only present if MAC CE is used for activation of SP SRS resource set, i.e. the A/D field is set to 1, or for AP SRS resource set;
• R: Reserved bit, set to 0.

The SRS Pathloss Reference RS Update MAC CE is identified by a MAC subheader with eLCID as specified in Table 6.2.1-1b. It has a fixed size of 24 bits:

• Serving Cell ID: This field indicates the identity of the Serving Cell, which contains activated SRS Resource Set. The length of the field is 5 bits;
• BWP ID: This field indicates a UL BWP as the codepoint of the DCI bandwidth part indicator field as specified in TS 38.212, which contains activated SRS Resource Set. The length of the field is 2 bits;
• SRS Resource Set ID: This field indicates the SRS Resource Set ID identified by SRS-ResourceSetId as specified in TS 38.331. The length of the field is 4 bits;
• Pathloss Reference RS ID: This field indicates the Pathloss Reference RS ID identified by srs-PathlossReferenceRS-Id as specified in TS 38.331. It updates the pathloss reference RS for an SRS-resource set indicated by SRS Resource Set ID field. The length of the field is 6 bits;
• R: Reserved bit, set to 0.

The PUSCH Pathloss Reference RS Update MAC CE is identified by a MAC subheader with eLCID as specified in Table 6.2.1-1b. It has a variable size and consists of the following fields:

• Serving Cell ID: This field indicates the identity of the Serving Cell, which contains activated PUSCH Pathloss Reference RS. The length of the field is 5 bits;
• BWP ID: This field indicates a UL BWP as the codepoint of the DCI bandwidth part indicator field as specified in TS 38.212, which contains activated PUSCH Pathloss Reference RS. The length of the field is 2 bits;
• T: If the UE is configured with two SRS resources sets for codebook or non-codebook, as specified in TS 38.331, in the indicated bandwidth part of the indicated Serving Cell, if this field is set to 0, SRI ID(s) to be updated are the ones associated with the first SRS resource set, and if is set to 1 the SRI ID(s) to be updated are the ones associated with the second SRS resource set. Otherwise, this field is a reserved bit set to 0;
• PUSCH Pathloss Reference RS ID: This field indicates the PUSCH Pathloss Reference RS ID identified by PUSCH-PathlossReferenceRS-Id as specified in TS 38.331, which is to be updated in the SRI PUSCH power control mappings indicated by SRI ID fields indicated in the same MAC CE. The length of the field is 6 bits;
• C: This field indicates the presence of the additional SRI ID in the last octet of this MAC CE. If this field is set to 1, two SRI ID(s) are present in the last octet. Otherwise only one SRI ID (i.e. the first SRI ID) is present in the last octet;
• SRI ID: This field indicates the SRI PUSCH power control ID identified by sri-PUSCH-PowerControlId as specified in TS 38.331. The length of the field is 4 bits;
• R: Reserved bit, set to 0.

The Serving Cell Set based SRS Spatial Relation indication MAC CE is identified by a MAC subheader with eLCID as specified in Table 6.2.1-1b. It has a variable size and consists of the following fields:

• SRS Resource's Cell ID: This field indicates the identity of the Serving Cell, which contains the indicated SP/AP SRS Resource. If the C field is set to 0, this field also indicates the identity of the Serving Cell which contains all resources indicated by the Resource ID_i fields. The length of the field is 5 bits. The indicated Serving Cell is configured as part of a simultaneousSpatial-UpdatedList1 or simultaneousSpatial-UpdatedList2 as specified in TS 38.331, and this MAC CE applies to all the Serving Cells configured in the set simultaneousSpatial-UpdatedList1 or simultaneousSpatial-UpdatedList2, respectively;
• SRS Resource's BWP ID: This field indicates a UL BWP as the codepoint of the DCI bandwidth part indicator field as specified in TS 38.212, which contains the indicated AP/SP SRS Resource. If the C field is set to 0, this field also indicates the identity of the BWP which contains all resources indicated by the Resource ID_i fields. The length of the field is 2 bits;
• C: This field indicates whether the octets containing Resource Serving Cell ID field(s) and Resource BWP ID field(s) are present. If this field is set to 1, the Resource Serving Cell ID field(s) and Resource BWP ID field(s) are present, otherwise they are not present so MAC entity shall ignore Resource Serving Cell ID field(s) and Resource BWP ID field(s);
• SRS Resource ID_i: This field indicates the SP/AP SRS Resource ID identified by SRS-ResourceId as specified in TS 38.331. The length of the field is 6 bits;
• F_i: This field indicates the type of a resource used as a spatial relationship for SRS resource indicated with SRS Resource ID_i field. F₀ refers to the first SRS resource which is indicated SRS Resource ID₁, F₁ to the second one and so on. The field is set to 1 to indicate NZP CSI-RS resource index is used, and it is set to 0 to indicate either SSB index or SRS resource index is used. The length of the field is 1 bit;
• Resource Serving Cell ID_i: This field indicates the identity of the Serving Cell on which the resource used for spatial relationship derivation for SRS Resource ID_i is located. The length of the field is 5 bits;
• Resource BWP ID_i: This field indicates a UL BWP as the codepoint of the DCI bandwidth part indicator field as specified in TS 38.212, on which the resource used for spatial relationship derivation for SRS Resource ID_i is located. The length of the field is 2 bits;
• Resource ID_i: This field contains an identifier of the resource used for spatial relationship derivation for SRS resource i. Resource ID₀ refers to the first SRS resource which is indicated SRS Resource ID₀, Resource ID₁ to the second one and so on. If F_i is set to 0, the first bit of this field is always set to 0. If F_i is set to 0, and the second bit of this field is set to 1, the remainder of this field contains SSB-Index as specified in TS 38.331. If F_i is set to 0, and the second bit of this field is set to 0, the remainder of this field contains SRS-ResourceId as specified in TS 38.331. The length of the field is 8 bits.
• R: Reserved bit, set to 0.

The LBT failure MAC CE of one octet is identified by a MAC subheader with LCID as specified in Table 6.2.1-2. It has a fixed size and consists of a single octet containing 8 C-fields as follows (Figure 6.1.3.30-1). The LBT failure MAC CE of four octets is identified by a MAC subheader with LCID as specified in Table 6.2.1-2. It has a fixed size and consists of four octets containing 32 C-fields as follows (Figure 6.1.3.30-2). A single octet format is used when the highest ServCellIndex of this MAC entity's Serving Cell for which consistent LBT failure is detected is less than 8, otherwise four octets format is used.

• C_i: If there is a Serving Cell configured for the MAC entity with ServCellIndex i as specified in TS 38.331 and if consistent LBT failure have been triggered and not cancelled in this Serving Cell, the field is set to 1, otherwise the field is set to 0.