6.2 Formats and parameters
38.3213GPPMedium Access Control (MAC) protocol specificationNRRelease 17TS
6.2.1 MAC subheader for DL-SCH and UL-SCH
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 Tables 6.2.1-1, 6.2.1-1c and 6.2.1-2 for the DL-SCH and UL-SCH respectively. 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, 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, 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 tables 6.2.1-1a, 6.2.1-1b, 6.2.1-2a and 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;
– 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 226 |
64 to 290 |
Reserved |
|
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 Ci field |
|
232 |
296 |
Enhanced SCell Activation/Deactivation MAC CE with four octet Ci 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 broadcast on DL-SCH
|
Codepoint/Index |
LCID values |
|
0 |
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
|
Codepoint/Index |
LCID values |
|
|
0 |
CCCH of size 64 bits (referred to as "CCCH1" in TS 38.331 [5]), except for a 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 (referred to as "CCCH" in TS 38.331 [5]) for a RedCap UE |
|
|
36 |
CCCH of size 64 bits (referred to as "CCCH1" in TS 38.331 [5]) for a RedCap UE |
|
|
37–42 |
Reserved |
|
|
43 |
Truncated Enhanced BFR (one octet Ci) |
|
|
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 Ci) |
|
|
51 |
Truncated BFR (one octet Ci) |
|
|
52 |
CCCH of size 48 bits (referred to as "CCCH" in TS 38.331 [5]), except for a RedCap UE |
|
|
53 |
Recommended bit rate query |
|
|
54 |
Multiple Entry PHR (four octets Ci) |
|
|
55 |
Configured Grant Confirmation |
|
|
56 |
Multiple Entry PHR (one octet Ci) |
|
|
57 |
Single Entry PHR |
|
|
58 |
C-RNTI |
|
|
59 |
Short Truncated BSR |
|
|
60 |
Long Truncated BSR |
|
|
61 |
Short BSR |
|
|
62 |
Long BSR |
|
|
63 |
Padding |
|
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 228 |
64 to 292 |
Reserved |
|
229 |
293 |
Enhanced Multiple Entry PHR for multiple TRP (four octets Ci) |
|
230 |
294 |
Enhanced Multiple Entry PHR for multiple TRP (one octets Ci) |
|
231 |
295 |
Enhanced Single Entry PHR for multiple TRP |
|
232 |
296 |
Enhanced Multiple Entry PHR (four octets Ci) |
|
233 |
297 |
Enhanced Multiple Entry PHR (one octets Ci) |
|
234 |
298 |
Enhanced Single Entry PHR |
|
235 |
299 |
Enhanced BFR (one octet Ci) |
|
236 |
300 |
Enhanced BFR (four octet Ci) |
|
237 |
301 |
Truncated Enhanced BFR (four octet Ci) |
|
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 Ci) |
|
251 |
315 |
Truncated BFR (four octets Ci) |
|
252 |
316 |
Multiple Entry Configured Grant Confirmation |
|
253 |
317 |
Sidelink Configured Grant Confirmation |
|
254 |
318 |
Desired Guard Symbols |
|
255 |
319 |
Pre-emptive BSR |
6.2.2 MAC subheader for Random Access Response
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
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
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;
– 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 [6]. 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 [6]. 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.
Figure 6.2.3-1: MAC RAR
6.2.3a MAC payload for MSGB
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;
– 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 [6]. 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 [6]. 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.
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 [6]. 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 [18]. 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 [6]. 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 [6]. 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[6]. 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 [6]. 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.
Figure 6.2.3a-2: successRAR
6.2.4 MAC subheader for SL-SCH
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 [19] or TS 23.304 [26]. 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 [19] or TS 23.304 [26]. 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 Tables 6.2.4-1 for SL-SCH. There is one LCID field per MAC subheader except for SL-SCH subheader. The size of the LCID field is 6 bits;
– L: The Length field indicates the length of the corresponding MAC SDU 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" |
|
2 |
SCCH carrying other PC5-S messages that are protected |
|
3 |
SCCH carrying PC5-RRC messages |
|
4–19 |
Identity of the logical channel |
|
20–55 |
Reserved |
|
56 |
SCCH carrying RRC messages delivered via SL-RLC0 as specified in TS 38.331 [5] |
|
57 |
SCCH carrying RRC message delivered via SL-RLC1 as specified in TS 38.331 [5] |
|
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 |