Content for  TS 38.321  Word version:  18.3.0

The Inter-UE Coordination Information MAC CE or Enhanced Inter-UE Coordination Information MAC CE is identified by a MAC subheader with corresponding LCID as specified in Table 6.2.4-1. The priority of the Inter-UE Coordination Information MAC CE or Enhanced Inter-UE Coordination Information MAC CE is fixed to '1' for Logical Channel Prioritization (LCP) procedure. The Inter-UE Coordination Information MAC CE (as shown in Figure 6.1.3.53-1) or the Enhanced Inter-UE Coordination Information MAC CE (as shown in Figure 6.1.3.53-2) has a variable size with following fields:

• RT: This field indicates the resource set type, i.e., preferred resource set or non-preferred resource set, as the codepoint value of the SCI format 2-C Resource set type field as specified in TS 38.212.
• RSL: This field indicates the location of reference slot, as the codepoint value of the SCI format 2-C Reference slot location field as specified in TS 38.212. The length of the field is 17 bits. If the length of Reference slot location field in SCI format 2-C as specified in TS 38.212 is shorter than 17 bit, this field contains Reference slot location field using the LSB bits;
• LSI_i: This field indicates the lowest subchannel indices for the first resource location of each TRIV, as the codepoint value of the SCI format 2-C Lowest subChannel indices field as specified in TS 38.212. LSI₀ indicates the lowest subchannel indices for the first resource location of TRIV within the first resource combination, LSI₁ indicates the lowest subchannel indices for the first resource location of TRIV within the second resource combination and so on. For Inter-UE Coordination Information MAC CE, the length of the field is 5 bits. If the length of Lowest subChannel indices field in SCI format 2-C as specified in TS 38.212 is shorter than 5 bit, this field contains Lowest subChannel indices field using the LSB bits; For Enhanced Inter-UE Coordination Information MAC CE, the length of the field is 4 bits. If the length of Lowest subChannel indices field in SCI format 2-C as specified in TS 38.212 is shorter than 4 bit, this field contains Lowest subChannel indices field using the LSB bits;
• LRI_i: This field is only included in the Enhanced Inter-UE Coordination Information MAC CE. It indicates the lowest RB set indices for the first resource location of each TRIV, as the codepoint value of the SCI format 2-C Lowest RB set indices field as specified in TS 38.212. LRI₀ indicates the lowest RB set indices for the first resource location of TRIV within the first resource combination, LRI₁ indicates the lowest RB set indices for the first resource location of TRIV within the second resource combination and so on. The length of the field is 3 bits. If the length of Lowest RB set indices field in SCI format 2-C as specified in TS 38.212 is shorter than 3 bits, this field contains Lowest RB set indices field using the LSB bits;
• RC_i:This field indicates resource combination, as the codepoint value of the SCI format 2-C Resource combinations field as specified in TS 38.212. The number of RC is based on upper bound of the L field in the MAC subheader as indicated in clause 6.2.1. RC₀ indicates the first resource combination, RC₁ indicates the second resource combination and so on. For Inter-UE Coordination Information MAC CE, the length of the field is 26 bits. If the length of Resource combinations field in SCI format 2-C as specified in TS 38.212 is shorter than 26 bit, this field contains Resource combinations field using the LSB bits; For Enhanced Inter-UE Coordination Information MAC CE, the length of the field is 28bis. If the length of Resource combination field in SCI format 2-C as specified in TS 38.212 is shorter than 28 bits, this field contains Resource combination field using the LSB bits;
• First resource location_i-1: This field indicates the first resource location, as the codepoint value of the SCI format 2-C 0 field as specified in TS 38.212. First Resource Location₀ indicates the first resource location for the second resource combination, First Resource Location₁ indicates the first resource location for the third resource combination and so on. The length of the field is 13 bits. If the length of First resource location field in SCI format 2-C as specified in TS 38.212 is shorter than 13 bit, this field contains First resource location field using the LSB bits;
• R: Reserved bit, set to 0.

The Inter-UE Coordination request MAC CE or Enhanced Inter-UE Coordination Request MAC CE is identified by a MAC subheader with corresponding LCID as specified in Table 6.2.4-1. The priority of the Inter-UE Coordination Request MAC CE or Enhanced Inter-UE Coordination Request MAC CE is fixed to '1' for Logical Channel Prioritization (LCP) procedure. The Inter-UE Coordination MAC CE has a fixed size of 48 bits (as shown in Figure 6.1.3.54-1), and the Enhanced Inter-UE Coordination Request MAC CE has a fixed size of 56 bits (as shown in Figure 6.1.3.54-2). The fields are defined as follows:

• RT: If the value of sl-DetermineResourceType (as specified in clause 6.3.5 of TS 38.331) is set to ueb, this field indicates the resource set type, i.e., preferred resource set or non-preferred resource set, as the codepoint value of the SCI format 2-C Resource set type field as specified in TS 38.212. This field is ignored if the value of sl-DetermineResourceType is set to uea;
• RP: This field indicates the resource reservation period, as the codepoint value of the SCI format 2-C Resource reservation period field as specified in TS 38.212. The length of the field is 4 bits. If the length of Resource reservation period field in SCI format 2-C as specified in TS 38.212 is shorter than 4 bit, this field contains Resource reservation period field using the LSB bits;
• Priority: This field indicates the priority, as the codepoint value of the SCI format 2-C Priority field as specified in TS 38.212. The length of the field is 3 bits;
• RSWL: This field indicates resource selection window location, as the codepoint value of the SCI format 2-C Resource selection window location field as specified in TS 38.212. The length of the field is 34 bits. If the length of Resource selection window location field in SCI format 2-C as specified in TS 38.212 is shorter than 34 bit, this field contains Resource selection window location field using the LSB bits;
• Number of Subchannel: This field indicates the number of subchannels, as the codepoint value of the SCI format 2-C Number of subchannels field as specified in TS 38.212. For Inter-UE Coordination Request MAC CE, the length of the field is 5 bits. If the length of Number of subchannels field in SCI format 2-C as specified in TS 38.212 is shorter than 5 bit, this field contains Number of subchannels field using the LSB bits; for Enhanced Inter-UE Coordination Request MAC CE, the length of the field is 4 bits. If the length of Number of subchannel field in SCI format 2-C as specified in TS 38.212 is shorter than 4 bits, this field contains Number of subchannel field using the LSB bits;
• Number of RB Set: This field is only included in the enhanced format. It indicates the number of RB sets, as the codepoint value of the SCI format 2-C Number of RB set field as specified in TS 38.212. The length of the field is 3 bits. If the length of Number of RB set field in SCI format 2-C as specified in TS 38.212 is shorter than 3 bits, this field contains Number of RB set field using the LSB bits;
• R: Reserved bit, set to 0.

The Enhanced SCell Activation/Deactivation MAC CE with one octet C_i field is identified by a MAC subheader with eLCID as specified in Table 6.2.1-1b. It has a variable size and consists of seven C-fields, one R-field and zero or more TRS ID_j fields in ascending order based on the ScellIndex for SCells indicated by the C_i field(s) to be activated. The Enhanced SCell Activation/Deactivation MAC CE of with one octet C_i field is defined as follows (Figure 6.1.3.55-1). The Enhanced SCell Activation/Deactivation MAC CE with four octet C_i field is identified by a MAC subheader with eLCID as specified in Table 6.2.1-1b. It has a variable size and consists of 31 C-fields, one R-field and zero or more TRS ID_j fields in ascending order based on the ScellIndex for SCells indicated by the C_i field(s) to be activated. The Enhanced SCell Activation/Deactivation MAC CE with four octet C_i field is defined as follows (Figure 6.1.3.55-2).

• C_i: If there is an SCell configured for the MAC entity with SCellIndex i as specified in TS 38.331, this field indicates the activation/deactivation status of the SCell with SCellIndex i, else the MAC entity shall ignore the C_i field. The C_i field is set to 1 to indicate that the SCell with SCellIndex i shall be activated and that a TRS ID_j field is included for the SCell. The C_i field is set to 0 to indicate that the SCell with SCellIndex i shall be deactivated and that no TRS ID field is included for this SCell;
• TRS ID_j: If TRS ID_j is set to a non-zero value, it indicates the corresponding TRS address by scellActivationRS-Id as specified in TS 38.331 is activated. If TRS ID_j is set to zero, it indicates that no TRS is used for the corresponding SCell;
• R: Reserved bit, set to 0.

The Timing Advance Report MAC CE is identified by MAC subheader with LCID as specified in Table 6.2.1-2. It has a fixed size and consists of two octets defined as follows (Figure 6.1.3.56-1):

• R: Reserved bit, set to 0;
• Timing Advance: Except for ATG in FR1, the Timing Advance field indicates the least integer number of slots, using subcarrier spacing of 15 kHz, greater than or equal to the Timing Advance value (see clause 4.3.1 of TS 38.211).
  For ATG in FR1, the Timing Advance field indicates the least integer number of symbols greater than or equal to the Timing Advance value (see clause 4.3.1 of TS 38.211). The symbol duration is based on the subcarriers spacing the UE is currently configured with. In this release of the specification, only 15 kHz and 30 kHz SCS are applicable and only values 1 … 56 are used.
  The length of the field is 14 bits.

The Differential Koffset MAC CE is identified by a MAC subheader with eLCID as specified in Table 6.2.1-1b. It has a fixed size and consists of a single octet defined as follows (Figure 6.1.3.57-1):

• R: Reserved bit, set to 0;
• Differential Koffset: This field indicates the differential Koffset in the number of slots (see clause 4.2 of TS 38.213), using subcarrier spacing of 15 kHz. The length of the field is 6 bits.

The BFD-RS 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 includes a BFD-RS-ID0 field and a BFD-RS-ID1 field (optional) of failureDetectionSet1, and a BFD-RS-ID0 field and a BFD-RS-ID1 field (optional) of failureDetectionSet2. It has a variable size consisting of following fields:

• Serving Cell ID: This field indicates the identity of the Serving Cell for which the MAC CE applies. The length of the field is 5 bits;
• BWP ID: This field indicates a DL BWP for which the MAC CE applies as the codepoint of the DCI bandwidth part indicator field as specified in TS 38.213. The length of the BWP ID field is 2 bits;
• S: This field indicates the presence of the octet containing the BFD-RS ID₁ of the same BFD-RS set. The S field set to 1 indicates that the octet containing BFD-RS ID₁ is included. The S field set to 0 indicates that the octet containing the BFD-RS ID₁ of the same BFD-RS set is not included;
• BFD-RS ID_i: This field indicates the BFD-RS resource from failureDetectionSet1 or failureDetectionSet2 as specified in TS 38.331;
• R: Reserved bit, set to 0.