Content for  TS 38.321  Word version:  18.3.0

The SP/AP SRS TCI State 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 associated with all TCI states indicated by the TCI State 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 associated with all TCI states indicated by the TCI State ID_i fields. The length of the field is 2 bits;
• C: This field indicates whether the octets containing TCI State Serving Cell ID field(s) and TCI State BWP ID field(s) are present. If this field is set to 1, TCI State Serving Cell ID field(s) and TCI State BWP ID field(s) are present, otherwise they are not present so MAC entity shall ignore TCI State Serving Cell ID field(s) and TCI State 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;
• TCI State Serving Cell ID_i: This field indicates the identity of the Serving Cell on which the TCI State used for SRS resource i is located. The length of the field is 5 bits;
• TCI State BWP ID_i: This field indicates a BWP as the codepoint of the DCI bandwidth part indicator field as specified in TS 38.212, on which the TCI State used for SRS resource i is located. If value of unifiedTCI-StateType in the Serving Cell indicated by TCI State Serving Cell ID_i is joint, this field indicates a DL BWP. If value of unifiedTCI-StateType in the Serving Cell indicated by TCI State Serving Cell ID_i is separate, this field indicates a UL BWP. The length of the field is 2 bits;
• TCI State ID_i: This field contains an identifier of the TCI state used for SRS resource i. TCI State ID0 refers to the first SRS resource within the resource set, TCI State ID1 refers to the second one and so on. If joint/downlink TCI State is used, 7-bits length TCI state ID i.e. TCI-StateId as specified in TS 38.331 is used. If separate downlink and uplink TCI State is used, the most significant bit of TCI state ID is considered as a reserved bit and the remaining 6 bits indicate the TCI-UL-State-Id as specified in TS 38.331. The length of the field is 7 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 Serving Cell Set based SRS TCI State Indication MAC CE is identified by a MAC subheader with eLCID as specified. It has a variable size with 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 associated with all TCI States indicated by the TCI State ID_i fields. The length of the field is 5 bits. The indicated Serving Cell is configured as part of simultaneousSpatial-UpdatedList1 or simultaneousSpatial-UpdatedList2 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 associated with all TCI States indicated by the TCI State ID_i fields. The length of the field is 2 bits;
• C: This field indicates whether the octets containing TCI State Serving Cell ID field(s) and TCI State BWP ID field(s) are present. If this field is set to 1, the TCI State Serving Cell ID field(s) and TCI State BWP ID field(s) are present, otherwise they are not present so MAC entity shall ignore TCI State Serving Cell ID field(s) and TCI State 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;
• TCI State Serving Cell ID_i: This field indicates the identity of the Serving Cell on which the TCI State used for SRS Resource ID_i is located. The length of the field is 5 bits;
• TCI State BWP ID_i: This field indicates a BWP as the codepoint of the DCI bandwidth part indicator field as specified in TS 38.212, on which the TCI State used for SRS Resource ID_i is located. If value of unifiedTCI-StateType in the Serving Cell indicated by TCI State Serving Cell ID_i is joint, this field indicates a DL BWP. If value of unifiedTCI-StateType in the Serving Cell indicated by TCI State Serving Cell ID_i is separate, this field indicates a UL BWP. The length of the field is 2 bits;
• TCI State ID_i: This field contains an identifier of the TCI state used for SRS resource i. TCI State ID0 refers to the first SRS resource which is indicated SRS Resource ID₀, TCI State ID1 refers to the second one and so on. If joint/downlink TCI State is used, 7-bits length TCI state ID i.e. TCI-StateId as specified in TS 38.331 is used. If separate downlink and uplink TCI State is used, the most significant bit of TCI state ID is considered as a reserved bit and the remaining 6 bits indicate the TCI-UL-State-Id as specified in TS 38.331. The length of the field is 7 bits;
• R: Reserved bit, set to 0.

The Child IAB-DU Restricted Beam Indication MAC CE is identified by MAC subheader with eLCID as specified in Table 6.2.1-1b. It has a variable size with following fields (Figure 6.1.3.61-1):

• Resource Configuration ID: This fields indicates the RRC configuration which applies to this MAC CE and corresponds to iab-ResourceConfigID parameter in IAB-ResourceConfig as specified in TS 38.331. The length of the field is 16 bits;
• Number of child IAB-DU beams: This field indicates the number of restricted child IAB-DU beams included in the MAC CE. The length of the field is 8 bits. The number of restricted child IAB-DU beams is contained in the 3 rightmost bits of the field while the remaining 5 bits are considered as reserved bits;
• IAB-DU restricted beams type ID_i: This field determines the type of information used as an indication of a set of child IAB-DU's restricted beams, indicated with the Child IAB-DU Resource set ID_i field. IAB-DU restricted beams type ID0 refers to the first restricted beam within the resource set, IAB-DU restricted beams type ID1 to the second one and so on. If the value of the field is 00, SSB index is used (contained in the 6 rightmost bits of the Child IAB-DU Resource set ID_i field, with the two leftmost bits being set to zero). If the value of the field is 01, SSB index (contained in the 6 rightmost bits of the Child IAB-DU Resource set ID_i field) and STC index (contained in the two leftmost bits of the Child IAB-DU Resource set ID_i field) are both used. If the value of the field is set to 11, CSI-RS index, which is the NZP-CSI-RS-ResourceId as specified in TS 38.331, is used (comprising all 8 bits of the Child IAB-DU Resource set ID_i field). The length of the field is 2 bits;
• C_i1: This field indicates whether the octet containing the Number of cell configurations ID_i field is included or not. C01 refers to the first restricted beam within the resource set, C11 to the second one and so on. The field is set to 0 to indicate the octet is not included (and subsequently, that no cell information is included for the relevant restricted beam). The field is set to 1 to indicate that Number of cell configurations ID_i field is included. The length of the field is 1 bits;
• C_i2: This field indicates whether the child IAB-DU beam indicated with the Child IAB-DU Resource set ID_i field is associated with one or more uplink or downlink IAB-MT beams, indicated with the IAB-MT Resource set ID_ij fields. C02 refers to the first restricted beam within the resource set, C12 to the second one and so on. The field is set to 1 to indicate that at least one IAB-MT Resource set ID_ij field is included (and that Number of associated IAB-MT beams ID_i is included), and it is set to 0 to indicate that no IAB-MT Resource set ID_ij field is present (and that the Number of associated IAB-MT beams ID_i is absent). The length of the field is 1 bit;
• R: Reserved bit, set to 0;
• Child IAB-DU Resource set ID_i: an indication of the child IAB-DU's beam in the direction of which simultaneous operation is restricted. The length of the field is 8 bits;
• Number of cell configurations ID_i: This field indicates the number of cell configurations associated with the beam restriction indicated in Child IAB-DU Resource set ID_i. Number of cell configurations ID0 refers to the first restricted beam within the resource set, Number of cell configurations ID1 to the second one and so on. The length of the field is 8 bits;
• Cell info type ID_ij: indicates the type of information included in the Cell info ID_ij field. If the value of the field is set to zero, the combination of {MT CC, DU cell} is included in the Cell info ID_ij field, by including the IAB-DU cell in the first nine bits of the field, and the IAB-MT Serving Cell index into the next 5 bits of the field,. If the value of the field is set to one, only DU cell is included in the Cell info ID_ij field, by including the IAB-DU cell in the first nine bits of the field, and by setting the remaining five bits to zero. The length of the field is 1 bit;
• M_ij: This field indicates whether the octet containing multiplexing mode info (containing the Multiplexing mode info ID_ij field) is included or not. Mi0 refers to the first combination of {MT CC, DU cell} associated with Child IAB-DU Resource set ID_i, Mi1 to the second one and so on. The field is set to 1 to indicate that multiplexing mode info is included, and it is set to 0 to indicate that multiplexing mode info is not present. The length of the field is 1 bit;
• Cell info ID_ij: indicates the cell configuration associated with beam restriction indicated in Child IAB-DU Resource set ID_i. Cell info ID_i0 field refers to the first cell configuration associated with the beam restriction indicated in Child IAB-DU Resource set ID_i, Cell info ID_i1 field refers to the second cell configuration associated with the beam restriction indicated in Child IAB-DU Resource set ID_i, and so on. The length of the field is 15 bits;
• Multiplexing mode info ID_ij: The two rightmost bits indicate which of the four multiplexing modes defined in TS 38.473 is applicable. The third rightmost bit of this field indicates whether multiplexing restrictions mode information contained in the two rightmost bits of the field are applicable to non-overlapping frequency resources. This bit is set to 1 when multiplexing mode information contained in the two rightmost bits of the Multiplexing mode info ID_ij field is applicable to non-overlapping frequency resources. This field is set to 0 when multiplexing mode information contained in the two rightmost bits of the Multiplexing mode info ID_ij field is not applicable to non-overlapping frequency resources. The remaining 5 bits of this field are set to zero. The length of the field is 8 bits;
• Number of associated IAB-MT beams ID_i: This field indicates the number of IAB-MT beams associated with the beam indicated in Child IAB-DU Resource set ID_i. Number of associated IAB-MT beams ID0 refers to the first restricted beam within the resource set, Number of associated IAB-MT beams ID1 to the second one and so on. The length of the field is 8 bits. The number of IAB-MT beams associated with the beam indicated in Child IAB-DU Resource set ID_i is contained in the 3 rightmost bits of the field while the remaining 5 bits are considered as reserved bits;
• Associated IAB-MT's beams type ID_ij: This field determines the type of information used as an indication of an uplink or downlink IAB-MT beam associated with the child IAB-DU's restricted beams, indicated with the IAB-MT Resource set ID_ij. If the value of the field is 00, the information included in the IAB-MT Resource set ID_ij field is the TCI state ID (contained in the 7 rightmost bits of the field). If the value of the field is 01, the information included in the IAB-MT Resource set ID_ij field is the SSB ID (contained in the 6 rightmost bits of the field). If the value of the field is 10, the information included in the IAB-MT Resource set ID_ij field is the CSI-RS index (comprising all 8 bits), which is the NZP-CSI-RS-ResourceId as specified in TS 38.331. If the value of the field is 11, the information included in the 6 rightmost bits in the IAB-MT Resource set ID_ij field is the SRS-ResourceID. The length of the field is 2 bits;
• IAB-MT Resource set ID_ij: an indication of the IAB-MTs downlink or uplink beams which are associated with the child IAB-DU restricted beam indicated in Child IAB-DU Resource set ID_i field. IAB-MT Resource set ID_i0 field refers to the first IAB-MT's beam associated with the child IAB-DU's restricted beam indicated in Child IAB-DU Resource set ID_i field, IAB-MT Resource set ID_i1 field refers to the second IAB-MT's beam associated with the child IAB-DU's restricted beam indicated in Child IAB-DU Resource set ID_i field, and so on. The length of the field is 8 bits.

The IAB-MT Recommended Beam Indication MAC CE is identified by MAC subheader with eLCID as specified in Table 6.2.1-2b. It has a variable size with following fields (Figure 6.1.3.62-1):

• Resource Configuration ID: This field indicates the RRC configuration which applies to this MAC CE and corresponds to iab-ResourceConfigID parameter in IAB-ResourceConfig as specified in TS 38.331. The length of the field is 16 bits;
• Number of IAB-MT beams: This field indicates the number of recommended IAB-MT beams included in the MAC CE. The length of the field is 8 bits. The number of recommended IAB-MT beams is contained in the 3 rightmost bits of the field while the remaining 5 bits are considered as reserved bits;
• IAB-MT beam type ID_i: This field determines the type of information used as an indication of an uplink or downlink IAB-MT beam, indicated with the IAB-MT Resource set ID_i. If the value of the field is 00, the information included in the IAB-MT Resource set ID_i field is the TCI state ID (contained in the 7 rightmost bits of the field). If the value of the field is 01, the information included in the IAB-MT Resource set ID_i field is the SSB ID (contained in the 6 rightmost bits of the field). If the value of the field is 10, the information included in the IAB-MT Resource set ID_i field is the CSI-RS index (comprising all 8 bits), which is the NZP-CSI-RS-ResourceId as specified in TS 38.331. If the value of the field is 11, the information included in the 6 rightmost bits in the IAB-MT Resource set ID_i field is the SRS-ResourceID. The length of the field is 2 bits;
• IAB-MT Resource set ID_i: an indication of the IAB-MTs recommended downlink or uplink beams. IAB-MT Resource set ID0 field refers to the first IAB-MT's beam, IAB-MT Resource set ID1 field refers to the second IAB-MT's beam, and so on. The length of the field is 8 bits;
• C_i1: This field indicates whether the octet containing the Number of cell configurations ID_i field is included or not. C01 refers to the first recommended beam within the resource set, C11 to the second one and so on. The field is set to 0 to indicate the octet is not included (and subsequently, that no cell information is included for the relevant recommended beam). The field is set to 1 to indicate that Number of cell configurations ID_i field is included. The length of the field is 1 bits;
• R: Reserved bit, set to 0;
• Number of cell configurations ID_i: This field indicates the number of cell configurations associated with the beam indicated in IAB-MT Resource set ID_i. Number of cell configurations ID0 refers to the first recommended beam within the resource set, Number of cell configurations ID1 to the second one and so on. The length of the field is 8 bits;
• Cell info type ID_ij: indicates the type of information included in the Cell info ID_ij field. If the value of the field is set to zero, the combination of {MT CC, DU cell} is included in the Cell info ID_ij field, by including the IAB-DU cell in the first nine bits of the field, and the IAB-MT Serving Cell index into the next 5 bits of the field. If the value of the field is set to one, only MT CC information is included in the Cell info ID_ij field, by including the IAB-MT Serving Cell index in the first 5 bits of the field, and by setting the remaining nine bits to zero. The length of the field is 1 bit;
• M_ij: This field indicates whether the octet containing multiplexing mode info (containing the Multiplexing mode info ID_ij field) is included or not. Mi0 refers to the first combination of {MT CC, DU cell} associated with IAB-MT Resource set ID_i, Mi1 to the second one and so on. The field is set to 1 to indicate that multiplexing mode info is included, and it is set to 0 to indicate that multiplexing mode info is not present. The length of the field is 1 bit;
• Cell info ID_ij: indicates the cell configuration associated with beam recommendation indicated in IAB-MT Resource set ID_i. Cell info ID_i0 field refers to the first cell configuration associated with the beam recommendation indicated in IAB-MT Resource set ID_i, Cell info ID_i1 field refers to the second cell configuration associated with the beam recommendation indicated in IAB-MT Resource set ID_i, and so on. The length of the field is 14 bits.
• Multiplexing mode info ID_ij: The two rightmost bits indicate which of the four multiplexing modes defined in TS 38.473 is applicable. The third rightmost bit of this field indicates whether multiplexing restrictions mode information contained in the two rightmost bits of the field are applicable to non-overlapping frequency resources. This bit is set to 1 when multiplexing mode information contained in the two rightmost bits of the Multiplexing mode info ID_ij field is applicable to non-overlapping frequency resources. This field is set to 0 when multiplexing mode information contained in the two rightmost bits of the Multiplexing mode info ID_ij field is not applicable to non-overlapping frequency resources. The remaining 5 bits of this field are set to zero. The length of the field is 8 bits.

The DL TX Power Adjustment MAC CE and Desired DL TX Power Adjustment MAC CEs are identified by MAC subheaders with eLCIDs as specified in Table 6.2.1-1b and Table 6.2.1-2b, respectively. Otherwise the format of the two MAC CEs is identical. Each has a variable size with following fields (Figure 6.1.3.63-1):

• Resource Configuration ID: This field indicates the RRC configuration which applies to this MAC CE and corresponds to iab-ResourceConfigID parameter in IAB-ResourceConfig as specified in TS 38.331. The length of the field is 16 bits;
• DL Tx Power adjustment: For the case of the Desired DL TX Power Adjustment MAC CE, this field contains desired DL TX power adjustment sent by an IAB-MT to assist with the parent node's DL TX power allocation. For the case of the DL TX Power Adjustment MAC CE, this fields contains adjustment to a node's DL TX power sent by its parent node. The value of the power adjustment is in both cases contained in the 5 right-most bits of the field with codepoints (00000, 00001, …, 11101, 11110) indicating the corresponding value (-15dB, -14dB, …, 14dB, 15dB) and the codepoint 11111 not being used, while the remaining 3 bits are set to zero. The length of the field is 8 bits;
• Reference CSI-RS ID: This field indicates the CSI-RS used as reference for power adjustment, which is identified by NZP-CSI-RS-ResourceId as specified in TS 38.331. The indicated DL TX power adjustment is in terms of a relative offset to the CSI-RS TX power of the indicated CSI-RS. The length of this field is 8bits;
• C₀: This field indicates whether the octet containing multiplexing mode info (containing the Multiplexing mode info field) is included or not. The field is set to 1 to indicate that multiplexing mode info is included, and it is set to 0 to indicate that multiplexing mode info is not present. The length of the field is 1 bit;
• C₁: This field indicates whether the two octets containing the Cell info are included or not. The field is set to 0 to indicate the two octets are not included (and subsequently, that no cell information is included). The field is set to 1 to indicate that the two octets are included. The length of the field is 1 bits;
• C₂: This field indicates whether any information on IAB-MT DL beams is included or not. The field is set to 1 to indicate that at least one IAB-MT Resource set ID_i field is included, and it is set to 0 to indicate that no IAB-MT Resource set ID_i field is present. The length of the field is 1 bit;
• R: Reserved bit, set to 0.
• Multiplexing mode info: The two rightmost bits indicate which of the four multiplexing modes defined in TS 38.473 is applicable. The third rightmost bit of this field indicates whether multiplexing restrictions mode information contained in the two rightmost bits of the field are applicable to non-overlapping frequency resources. This bit is set to 1 when multiplexing mode information contained in the two rightmost bits of the Multiplexing mode info field is applicable to non-overlapping frequency resources. This field is set to 0 when multiplexing mode information contained in the two rightmost bits of the Multiplexing mode info field is not applicable to non-overlapping frequency resources. The remaining 5 bits of this field are set to zero. The length of the field is 8 bits;
• Number of IAB-MT DL beams: This field indicates the number of IAB-MT beams included in the MAC CE. The length of the field is 8 bits;
• IAB-MT beam type ID_i: This field determines the type of information used as an indication of a downlink IAB-MT beam, indicated with the IAB-MT Resource set ID_i. If the value of the field is 00, the information included in the IAB-MT Resource set ID_i field is the TCI state ID (contained in the 7 rightmost bits of the field). If the value of the field is 01, the information included in the IAB-MT Resource set ID_i field is the SSB ID (contained in the 6 rightmost bits of the field). If the value of the field is 10, the information included in the IAB-MT Resource set ID_i field is the CSI-RS index (comprising all 8 bits), which is the NZP-CSI-RS-ResourceId as specified in TS 38.331. The length of the field is 2 bits;
• IAB-MT Resource set ID_i: an indication of the IAB-MTs downlink beams. IAB-MT Resource set ID0 field refers to the first IAB-MT downlink beam, IAB-MT Resource set ID1 field refers to the second IAB-MT downlink beam, and so on. The length of the field is 8 bits;
• DU resource configuration: when this field is set to 00, the provided power adjustment is applied on FDM resources where the simultaneous MT and DU signals are non-overlapping in the frequency-domain; when this field is set to 01, the provided power adjustment is applied on non-FDM resources where the simultaneous MT and DU signals may overlap in the frequency-domain for a given (MT CC, DU cell); when this field is set to 10, the provided power adjustment is applied on FDM resources where the simultaneous MT and DU signals are non-overlapping in the frequency-domain, and on non-FDM resources where the simultaneous MT and DU signals may overlap in the frequency-domain for a given (MT CC, DU cell). The length of the field is 2 bits;
• Cell info: indicates the cell configuration associated with the information contained in the MAC CE. The length of the field is 14 bits. IAB-DU cell is contained in the first nine bits of the field, while the Child IAB-MT Serving Cell index into the next 5 bits of the field. The length of the field is 14 bits.