Content for TS 38.321 Word version: 18.0.0

1… 4… 5… 5.1.2… 5.2… 5.4… 5.4.4… 5.5… 5.9… 5.18… 5.18.18… 5.19… 5.22… 5.22.1.4… 5.22.2… 5.23… 6… 6.1.3… 6.1.3.8… 6.1.3.11… 6.1.3.17… 6.1.3.21… 6.1.3.26… 6.1.3.31… 6.1.3.37… 6.1.3.42… 6.1.3.49… 6.1.3.53… 6.1.3.59… 6.1.3.64… 6.1.3.70… 6.1.3.74… 6.1.3.79… 6.1.4… 6.2… 7…

6.2 Formats and parameters 6.2.1 MAC subheader for DL-SCH and UL-SCH 6.2.2 MAC subheader for Random Access Response 6.2.2a MAC subheader for MSGB 6.2.3 MAC payload for Random Access Response 6.2.3a MAC payload for MSGB 6.2.4 MAC subheader for SL-SCH

6.2 Formats and parameters p. 289

6.2.1 MAC subheader for DL-SCH and UL-SCH p. 289

The MAC subheader consists of the following fields:

LCID: The Logical Channel ID field identifies the logical channel instance of the corresponding MAC SDU or the type of the corresponding MAC CE or padding as described in Table 6.2.1-1 and Table 6.2.1-1c for the DL-SCH and Table 6.2.1-2 and Table 6.2.1-2c for the UL-SCH. There is one LCID field per MAC subheader. The size of the LCID field is 6 bits. If the LCID field is set to 34 as in Table 6.2.1-1 or Table 6.2.1-2, one additional octet is present in the MAC subheader containing the eLCID field and follow the octet containing LCID field. If the LCID field is set to 33 as in Table 6.2.1-1 or Table 6.2.1-2, two additional octets are present in the MAC subheader containing the eLCID field and these two additional octets follow the octet containing LCID field;

NOTE 1:
For MBS broadcast, a logical channel is identified based on G-RNTI and LCID if the same LCID is allocated for logical channels corresponding to different G-RNTIs.
eLCID: The extended Logical Channel ID field identifies the logical channel instance of the corresponding MAC SDU or the type of the corresponding MAC CE as described in Table 6.2.1-1a, Table 6.2.1-1b, Table 6.2.1-2a and Table 6.2.1-2b for the DL-SCH and UL-SCH respectively. The size of the eLCID field is either 8 bits or 16 bits.

NOTE 2:
The extended Logical Channel ID space using two-octet eLCID and the relevant MAC subheader format is used, only when configured, on the NR backhaul links between IAB nodes or between IAB node and IAB Donor, or for multicast MTCHs.
L: The Length field indicates the length of the corresponding MAC SDU or variable-sized MAC CE in bytes. There is one L field per MAC subheader except for subheaders corresponding to fixed-sized MAC CEs, padding, and MAC SDUs containing UL CCCH. The size of the L field is indicated by the F field;
F: The Format field indicates the size of the Length field. There is one F field per MAC subheader except for subheaders corresponding to fixed-sized MAC CEs, padding, and MAC SDUs containing UL CCCH. The size of the F field is 1 bit. The value 0 indicates 8 bits of the Length field. The value 1 indicates 16 bits of the Length field;
LX: The LCID extension field indicates the use of extended LCID space. The size of the LX field is 1 bit. The LX field set to 1 indicates the use of Table 6.2.1-2c, otherwise R bit is present instead (i.e. set to 0);
R: Reserved bit, set to 0.

The MAC subheader is octet aligned.

Table 6.2.1-1: Values of LCID for DL-SCH

Codepoint/ Index	LCID values
0	CCCH
1-32	Identity of the logical channel of DCCH, DTCH and multicast MTCH
33	Extended logical channel ID field (two-octet eLCID field)
34	Extended logical channel ID field (one-octet eLCID field)
35-46	Reserved
47	Recommended bit rate
48	SP ZP CSI-RS Resource Set Activation/Deactivation
49	PUCCH spatial relation Activation/Deactivation
50	SP SRS Activation/Deactivation
51	SP CSI reporting on PUCCH Activation/Deactivation
52	TCI State Indication for UE-specific PDCCH
53	TCI States Activation/Deactivation for UE-specific PDSCH
54	Aperiodic CSI Trigger State Subselection
55	SP CSI-RS/CSI-IM Resource Set Activation/Deactivation
56	Duplication Activation/Deactivation
57	SCell Activation/Deactivation (four octets)
58	SCell Activation/Deactivation (one octet)
59	Long DRX Command
60	DRX Command
61	Timing Advance Command
62	UE Contention Resolution Identity
63	Padding

Table 6.2.1-1a: Values of two-octet eLCID for DL-SCH

Codepoint	Index	LCID values
0 to (216 - 1)	320 to (216 + 319)	Identity of the logical channel

Table 6.2.1-1b: Values of one-octet eLCID for DL-SCH

Codepoint	Index	LCID values
0 to 216	64 to 280	Reserved
217	281	Enhanced SP CSI reporting on PUCCH Activation/Deactivation MAC CE
218	282	Cross-RRH TCI State Indication for UE-specific PDCCH MAC CE
219	283	LTM Cell Switch Command
220	284	Candidate Cell TCI States Activation/Deactivation
221	285	PSI-Based SDU Discard Activation/Deactivation MAC CE
222	286	Enhanced Unified TCI state Activation/Deactivation MAC CE for Joint TCI States
223	287	Enhanced Unified TCI state Activation/Deactivation MAC CE for Separate TCI States
224	288	NCR Access Link Beam Indication MAC CE
225	289	NCR Downlink Backhaul Link Beam Indication MAC CE
226	290	NCR Uplink Backhaul Link Beam Indication MAC CE
227	291	Serving Cell Set based SRS TCI State Indication MAC CE
228	292	SP/AP SRS TCI State Indication MAC CE
229	293	BFD-RS Indication MAC CE
230	294	Differential Koffset
231	295	Enhanced SCell Activation/Deactivation MAC CE with one octet C_i field
232	296	Enhanced SCell Activation/Deactivation MAC CE with four octet C_i field
233	297	Unified TCI States Activation/Deactivation MAC CE
234	298	PUCCH Power Control Set Update for multiple TRP PUCCH repetition MAC CE
235	299	PUCCH spatial relation Activation/Deactivation for multiple TRP PUCCH repetition MAC CE
236	300	Enhanced TCI States Indication for UE-specific PDCCH
237	301	Positioning Measurement Gap Activation/Deactivation Command
238	302	PPW Activation/Deactivation Command
239	303	DL Tx Power Adjustment
240	304	Timing Case Indication
241	305	Child IAB-DU Restricted Beam Indication
242	306	Case-7 Timing advance offset
243	307	Provided Guard Symbols for Case-6 timing
244	308	Provided Guard Symbols for Case-7 timing
245	309	Serving Cell Set based SRS Spatial Relation Indication
246	310	PUSCH Pathloss Reference RS Update
247	311	SRS Pathloss Reference RS Update
248	312	Enhanced SP/AP SRS Spatial Relation Indication
249	313	Enhanced PUCCH Spatial Relation Activation/Deactivation
250	314	Enhanced TCI States Activation/Deactivation for UE-specific PDSCH
251	315	Duplication RLC Activation/Deactivation
252	316	Absolute Timing Advance Command
253	317	SP Positioning SRS Activation/Deactivation
254	318	Provided Guard Symbols
255	319	Timing Delta

Table 6.2.1-1c: Values of LCID for MBS multicast MCCH and MBS broadcast on DL-SCH

Codepoint/ Index	LCID values
0	Broadcast MCCH or multicast MCCH
1-32	Identity of the logical channel of broadcast MTCH
33-63	Reserved

Table 6.2.1-2: Values of LCID for UL-SCH when the LX field is not present or is set to 0

Codepoint/ Index	LCID values
0	CCCH of size 64 bits, except for an (e)RedCap UE
1-32	Identity of the logical channel of DCCH and DTCH
33	Extended logical channel ID field (two-octet eLCID field)
34	Extended logical channel ID field (one-octet eLCID field)
35	CCCH of size 48 bits for a RedCap UE
36	CCCH of size 64 bits for a RedCap UE
37	SL LBT failure
38-42	Reserved
43	Truncated Enhanced BFR (one octet C_i)
44	Timing Advance Report
45	Truncated Sidelink BSR
46	Sidelink BSR
47	Reserved
48	LBT failure (four octets)
49	LBT failure (one octet)
50	BFR (one octet C_i)
51	Truncated BFR (one octet C_i)
52	CCCH of size 48 bits, except for an (e)RedCap UE
53	Recommended bit rate query
54	Multiple Entry PHR (four octets C_i)
55	Configured Grant Confirmation
56	Multiple Entry PHR (one octet C_i)
57	Single Entry PHR
58	C-RNTI
59	Short Truncated BSR
60	Long Truncated BSR
61	Short BSR
62	Long BSR
63	Padding
NOTE: CCCH of size 48 bits and CCCH of size 64 bits are referred to as CCCH and CCCH1, respectively, in TS 38.331.

Table 6.2.1-2a: Values of two-octet eLCID for UL-SCH

Codepoint	Index	LCID values
0 to (216 - 1)	320 to (216 + 319)	Identity of the logical channel

Table 6.2.1-2b: Values of one-octet eLCID for UL-SCH

Codepoint	Index	LCID values
0 to 222	64 to 286	Reserved
223	287	Multiple Entry PHR with assumed PUSCH MAC CE (four octets C_i)
224	288	Multiple Entry PHR with assumed PUSCH MAC CE (one octets C_i)
225	289	Single Entry PHR with assumed PUSCH MAC CE
226	290	SL-PRS Resource Request
227	291	Refined Long BSR
228	292	Delay Status Report
229	293	Enhanced Multiple Entry PHR for multiple TRP (four octets C_i)
230	294	Enhanced Multiple Entry PHR for multiple TRP (one octets C_i)
231	295	Enhanced Single Entry PHR for multiple TRP
232	296	Enhanced Multiple Entry PHR (four octets C_i)
233	297	Enhanced Multiple Entry PHR (one octets C_i)
234	298	Enhanced Single Entry PHR
235	299	Enhanced BFR (one octet C_i)
236	300	Enhanced BFR (four octet C_i)
237	301	Truncated Enhanced BFR (four octet C_i)
238	302	Positioning Measurement Gap Activation/Deactivation Request
239	303	IAB-MT Recommended Beam Indication
240	304	Desired IAB-MT PSD range
241	305	Desired DL Tx Power Adjustment
242	306	Case-6 Timing Request
243	307	Desired Guard Symbols for Case 6 timing
244	308	Desired Guard Symbols for Case 7 timing
245	309	Extended Short Truncated BSR
246	310	Extended Long Truncated BSR
247	311	Extended Short BSR
248	312	Extended Long BSR
249	313	Extended Pre-emptive BSR
250	314	BFR (four octets C_i)
251	315	Truncated BFR (four octets C_i)
252	316	Multiple Entry Configured Grant Confirmation
253	317	Sidelink Configured Grant Confirmation
254	318	Desired Guard Symbols
255	319	Pre-emptive BSR

Table 6.2.1-2c: Values of LCID for UL-SCH when the LX field is set to 1

Codepoint	Index	LCID values
0	(216 + 320)	CCCH of size 48 bits for an eRedCap UE
1	(216 + 321)	CCCH of size 64 bits for an eRedCap UE
2	(216 + 322)	CCCH of size 48 bits for PUCCH repetition of Msg4 HARQ-ACK, except for an (e)RedCap UE
3	(216 + 323)	CCCH of size 64 bits for PUCCH repetition of Msg4 HARQ-ACK, except for an (e)RedCap UE
4	(216 + 324)	CCCH of size 48 bits for PUCCH repetition of Msg4 HARQ-ACK of a RedCap UE
5	(216 + 325)	CCCH of size 64 bits for PUCCH repetition of Msg4 HARQ-ACK of a RedCap UE
6	(216 + 326)	CCCH of size 48 bits for PUCCH repetition of Msg4 HARQ-ACK of an eRedCap UE
7	(216 + 327)	CCCH of size 64 bits for PUCCH repetition of Msg4 HARQ-ACK of an eRedCap UE
8 to 63	(216 + 328) to (216 + 383)	Reserved
NOTE 1: The MAC entity may use the code point corresponding to a given feature or feature combination in Table 6.2.1-2c only if network indicates support for the corresponding feature or feature combination. NOTE 2: CCCH of size 48 bits and CCCH of size 64 bits are referred to as CCCH and CCCH1, respectively, in TS 38.331.

6.2.2 MAC subheader for Random Access Response p. 294

The MAC subheader consists of the following fields:

E: The Extension field is a flag indicating if the MAC subPDU including this MAC subheader is the last MAC subPDU or not in the MAC PDU. The E field is set to 1 to indicate at least another MAC subPDU follows. The E field is set to 0 to indicate that the MAC subPDU including this MAC subheader is the last MAC subPDU in the MAC PDU;
T: The Type field is a flag indicating whether the MAC subheader contains a Random Access Preamble ID or a Backoff Indicator. The T field is set to 0 to indicate the presence of a Backoff Indicator field in the subheader (BI). The T field is set to 1 to indicate the presence of a Random Access Preamble ID field in the subheader (RAPID);
R: Reserved bit, set to 0;
BI: The Backoff Indicator field identifies the overload condition in the cell. The size of the BI field is 4 bits;
RAPID: The Random Access Preamble IDentifier field identifies the transmitted Random Access Preamble (see clause 5.1.3). The size of the RAPID field is 6 bits. If the RAPID in the MAC subheader of a MAC subPDU corresponds to one of the Random Access Preambles configured for SI request, MAC RAR is not included in the MAC subPDU.

The MAC subheader is octet aligned.

6.2.2a MAC subheader for MSGB |R16| p. 294

The MAC subheader consists of the following fields:

E: The Extension field is a flag indicating if the MAC subPDU including this MAC subheader is the last MAC subPDU (other than MAC subPDU for MAC SDU) or not in the MAC PDU. The E field is set to 1 to indicate at least another MAC subPDU (other than MAC subPDU for MAC SDU) follows. The E field is set to 0 to indicate that the MAC subPDU including this MAC subheader is the last MAC subPDU (other than MAC subPDU for MAC SDU) in the MAC PDU;
T1: The T1 field is a flag indicating whether the MAC subheader contains a Random Access Preamble ID or T2. The T1 field is set to 1 to indicate the presence of a Random Access Preamble ID field in the subheader (RAPID). The T1 field is set to 0 to indicate the presence of T2 field in the subheader;
T2: The T2 field is a flag indicating whether the MAC subheader contains a Backoff Indicator (BI) or a MAC SDU indicator (S). The T2 field is set to 0 to indicate the presence of a Backoff Indicator field in the subheader. The T2 field is set to 1 to indicate the presence of the S field in the subheader;
S: This field indicates whether 'MAC subPDU(s) for MAC SDU' follow the MAC subPDU including this MAC subheader or not; The S field is set to 1 to indicate presence of 'MAC subPDU(s) for MAC SDU'. The S field is set to 0 to indicate absence of 'MAC subPDU(s) for MAC SDU';
R: Reserved bit, set to 0;
BI: The Backoff Indicator field identifies the overload condition in the cell. The size of the BI field is 4 bits;
RAPID: The Random Access Preamble IDentifier field identifies the transmitted Random Access Preamble (see clause 5.1.3). The size of the RAPID field is 6 bits.

The MAC subheader is octet aligned.

6.2.3 MAC payload for Random Access Response p. 295

The MAC RAR is of fixed size as depicted in Figure 6.2.3-1, and consists of the following fields:

R: Reserved bit, set to 0;
TI: If two TAGs are configured for the Serving Cell in which the Random Access procedure is being performed, this field indicates one of the two TAGs to which the Timing Advance Command is applied. If tag2-flag is set to true by upper layers, the field set to 0 indicates the tag2-Id and the field set to 1 indicates the tag-Id of the Serving Cell, otherwise the field set to 0 indicates the tag-Id and the field set to 1 indicates the tag2-Id of the Serving Cell. If the Serving Cell in which the Random Access procedure is being performed is not configured with two TAGs, the R bit is present instead;
Timing Advance Command: The Timing Advance Command field indicates the index value TA used to control the amount of timing adjustment that the MAC entity has to apply in TS 38.213. The size of the Timing Advance Command field is 12 bits;
UL Grant: The Uplink Grant field indicates the resources to be used on the uplink in TS 38.213. The size of the UL Grant field is 27 bits;
Temporary C-RNTI: The Temporary C-RNTI field indicates the temporary identity that is used by the MAC entity during Random Access. The size of the Temporary C-RNTI field is 16 bits.

The MAC RAR is octet aligned.

Reproduction of 3GPP TS 38.321, Fig. 6.2.3-1: MAC RAR

Figure 6.2.3-1: MAC RAR

6.2.3a MAC payload for MSGB |R16| p. 296

The fallbackRAR is of fixed size as depicted in Figure 6.2.3a-1, and consists of the following fields:

R: Reserved bit, set to 0;
TI: If two TAGs are configured for the SpCell, this field indicates one of the two TAGs to which the Timing Advance Command is applied. If tag2-flag is set to true by upper layers, the field set to 0 indicates the tag2-Id and the field set to 1 indicates the tag-Id of the SpCell, otherwise the field set to 0 indicates the tag-Id and the field set to 1 indicates the tag2-Id of the SpCell. If the SpCell is not configured with two TAGs, the R bit is present instead;
Timing Advance Command: The Timing Advance Command field indicates the index value TA used to control the amount of timing adjustment that the MAC entity has to apply in TS 38.213. The size of the Timing Advance Command field is 12 bits;
UL Grant: The Uplink Grant field indicates the resources to be used on the uplink in TS 38.213. The size of the UL Grant field is 27 bits;
Temporary C-RNTI: The Temporary C-RNTI field indicates the temporary identity that is used by the MAC entity during Random Access. The size of the Temporary C-RNTI field is 16 bits.

The fallbackRAR is octet aligned.

Reproduction of 3GPP TS 38.321, Fig. 6.2.3a-1: fallbackRAR

Figure 6.2.3a-1: fallbackRAR

The successRAR is of fixed size as depicted in Figure 6.2.3a-2, and consists of the following fields:

UE Contention Resolution Identity: This field contains the UL CCCH SDU. If the UL CCCH SDU is longer than 48 bits, this field contains the first 48 bits of the UL CCCH SDU.
R: Reserved bit, set to 0;
ChannelAccess-CPext: The channel access type and CP extension for the PUCCH resource containing the HARQ feedback for MSGB in shared spectrum channel access as specified in TS 38.213. The field is only present when the MSGB HARQ feedback is to be transmitted with shared spectrum channel access as specified in TS 37.213. Otherwise, the field is not present and R bits are present instead. The size of the ChannelAccess-CPext field is 2 bits;
TPC: The TPC command for the PUCCH resource containing HARQ feedback for MSGB, as specified in TS 38.213. The size of the TPC field is 2 bits;
HARQ Feedback Timing Indicator: The PDSCH-to-HARQ feedback timing indicator field for MSGB HARQ feedback as specified in TS 38.213. The size of the HARQ Feedback Timing Indicator field is 3 bits;
PUCCH Resource Indicator: The PUCCH resource indicator for HARQ feedback for MSGB, as specified in TS 38.213. The size of the PUCCH resource Indicator field is 4 bits;
Timing Advance Command: The Timing Advance Command field indicates the index value TA used to control the amount of timing adjustment that the MAC entity has to apply in TS 38.213. The size of the Timing Advance Command field is 12 bits;
C-RNTI: The C-RNTI field indicates the identity that is used by the MAC entity upon completion of Random Access. The size of the C-RNTI field is 16 bits.

The successRAR is octet aligned.

Reproduction of 3GPP TS 38.321, Fig. 6.2.3a-2: successRAR

Figure 6.2.3a-2: successRAR

6.2.4 MAC subheader for SL-SCH |R16| p. 297

The MAC subheader consists of the following fields:

V: The MAC PDU format version number field indicates which version of the SL-SCH subheader is used. In this version of the specification, the V field is set to 0. The size of the V field is 4 bits;
SRC: The SRC field carries the 16 most significant bits of the Source Layer-2 ID set to the identifier provided by upper layers as defined in TS 23.287 or TS 23.304. The length of the field is 16 bits;
DST: The DST field carries the 8 most significant bits of the Destination Layer-2 ID set to the identifier provided by upper layers as defined in TS 23.287 or TS 23.304. The length of the field is 8 bits;
LCID: The Logical Channel ID field identifies the logical channel instance of the corresponding MAC SDU or the type of the corresponding MAC CE within the scope of one Source Layer-2 ID and Destination Layer-2 ID pair or padding as described in Table 6.2.4-1 for SL-SCH. There is one LCID field per MAC subheader except for SL-SCH subheader. The values of LCID from 21 to 36 identify the logical channels used to send duplicated RLC SDUs from logical channels of which the values of LCID from 4 to 19 respectively in sequential order. The size of the LCID field is 6 bits;
L: The Length field indicates the length of the corresponding MAC SDU or variable-sized MAC CE in bytes. There is one L field per MAC subheader except for SL-SCH subheader and subheaders corresponding to the fixed-sized MAC CE or padding. The size of the L field is indicated by the F field;
F: The Format field indicates the size of the Length field. There is one F field per MAC subheader except for SL-SCH subheader and subheaders corresponding to the fixed-sized MAC CE or padding. The size of the F field is 1 bit. The value 0 indicates 8 bits of the Length field. The value 1 indicates 16 bits of the Length field;
R: Reserved bit, set to 0.

The MAC subheader is octet aligned.

Table 6.2.4-1: Values of LCID for SL-SCH

Index	LCID values
0	SCCH carrying PC5-S messages that are not protected
1	SCCH carrying PC5-S messages "Direct Security Mode Command" and "Direct Security Mode Complete","ProSe direct link security mode command" and "ProSe direct link security mode complete"
2	SCCH carrying other PC5-S messages that are protected
3	SCCH carrying PC5-RRC messages
4-19	Identity of the logical channel
20	SCCH carrying PC5-S messages ("Direct Security Mode Command" and "Direct Security Mode Complete") which is used for duplication
21	SCCH carrying other PC5-S messages that are protected which is used for duplication
22	SCCH carrying PC5-RRC messages which is used for duplication
23-38	Identity of the logical channel which is used for duplication
39-54	Reserved
55	SCCH carrying end-to-end SL-SRB0/1/2/3 messages delivered via SL-U2U-RLC as specified in TS 38.331
56	SCCH carrying RRC messages delivered via SL-RLC0 as specified in TS 38.331
57	SCCH carrying RRC message delivered via SL-RLC1 as specified in TS 38.331
58	SCCH for Sidelink Discovery Messages
59	Sidelink Inter-UE Coordination Request
60	Sidelink Inter-UE Coordination Information
61	Sidelink DRX Command
62	Sidelink CSI Reporting
63	Padding