ETSI TS 138 321 V15.8.0 (2020-01)

ETSI TS 138 321 V15.8.0 (2020-01)






TECHNICAL SPECIFICATION
5G;
NR;
Medium Access Control (MAC) protocol specification
(3GPP TS 38.321 version 15.8.0 Release 15)

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3GPP TS 38.321 version 15.8.0 Release 15 1 ETSI TS 138 321 V15.8.0 (2020-01)



Reference
RTS/TSGR-0238321vf80
Keywords
5G
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3GPP TS 38.321 version 15.8.0 Release 15 2 ETSI TS 138 321 V15.8.0 (2020-01)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
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Legal Notice
This Technical Specification (TS) has been produced by ETSI 3rd Generation Partnership Project (3GPP).
The present document may refer to technical specifications or reports using their 3GPP identities. These shall be
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The cross reference between 3GPP and ETSI identities can be found under http://webapp.etsi.org/key/queryform.asp.
Modal verbs terminology
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provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI

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3GPP TS 38.321 version 15.8.0 Release 15 3 ETSI TS 138 321 V15.8.0 (2020-01)
Contents
Intellectual Property Rights . 2
Legal Notice . 2
Modal verbs terminology . 2
Foreword . 6
1 Scope . 7
2 References . 7
3 Definitions, symbols and abbreviations . 8
3.1 Definitions . 8
3.2 Abbreviations . 8
4 General . 9
4.1 Introduction . 9
4.2 MAC architecture . 9
4.2.1 General . 9
4.2.2 MAC Entities . 9
4.3 Services . 10
4.3.1 Services provided to upper layers . 10
4.3.2 Services expected from physical layer . 11
4.4 Functions . 11
4.5 Channel structure . 11
4.5.1 General . 11
4.5.2 Transport Channels . 11
4.5.3 Logical Channels . 12
4.5.4 Mapping of Transport Channels to Logical Channels . 12
4.5.4.1 General . 12
4.5.4.2 Uplink mapping . 12
4.5.4.3 Downlink mapping . 12
5 MAC procedures . 13
5.1 Random Access procedure . 13
5.1.1 Random Access procedure initialization . 13
5.1.2 Random Access Resource selection . 16
5.1.3 Random Access Preamble transmission . 18
5.1.4 Random Access Response reception. 19
5.1.5 Contention Resolution . 21
5.1.6 Completion of the Random Access procedure . 22
5.2 Maintenance of Uplink Time Alignment . 22
5.3 DL-SCH data transfer . 24
5.3.1 DL Assignment reception . 24
5.3.2 HARQ operation . 25
5.3.2.1 HARQ Entity. 25
5.3.2.2 HARQ process . 25
5.3.3 Disassembly and demultiplexing . 26
5.4 UL-SCH data transfer . 27
5.4.1 UL Grant reception . 27
5.4.2 HARQ operation . 28
5.4.2.1 HARQ Entity. 28
5.4.2.2 HARQ process . 30
5.4.3 Multiplexing and assembly . 30
5.4.3.1 Logical Channel Prioritization . 30
5.4.3.1.1 General . 30
5.4.3.1.2 Selection of logical channels . 31
5.4.3.1.3 Allocation of resources . 31
5.4.3.2 Multiplexing of MAC Control Elements and MAC SDUs . 32
5.4.4 Scheduling Request. 32
ETSI

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3GPP TS 38.321 version 15.8.0 Release 15 4 ETSI TS 138 321 V15.8.0 (2020-01)
5.4.5 Buffer Status Reporting . 34
5.4.6 Power Headroom Reporting . 36
5.5 PCH reception . 38
5.6 BCH reception . 38
5.7 Discontinuous Reception (DRX) . 38
5.8 Transmission and reception without dynamic scheduling . 40
5.8.1 Downlink . 40
5.8.2 Uplink . 41
5.9 Activation/Deactivation of SCells . 42
5.10 Activation/Deactivation of PDCP duplication. 43
5.11 MAC reconfiguration . 44
5.12 MAC Reset . 44
5.13 Handling of unknown, unforeseen and erroneous protocol data . 45
5.14 Handling of measurement gaps . 45
5.15 Bandwidth Part (BWP) operation . 45
5.16 SUL operation . 47
5.17 Beam Failure Detection and Recovery procedure . 48
5.18 Handling of MAC CEs . 49
5.18.1 General . 49
5.18.2 Activation/Deactivation of Semi-persistent CSI-RS/CSI-IM resource set . 49
5.18.3 Aperiodic CSI Trigger State Subselection . 49
5.18.4 Activation/Deactivation of UE-specific PDSCH TCI state . 50
5.18.5 Indication of TCI state for UE-specific PDCCH . 50
5.18.6 Activation/Deactivation of Semi-persistent CSI reporting on PUCCH . 50
5.18.7 Activation/Deactivation of Semi-persistent SRS . 50
5.18.8 Activation/Deactivation of spatial relation of PUCCH resource . 50
5.18.9 Activation/Deactivation of semi-persistent ZP CSI-RS resource set . 51
5.18.10 Recommended Bit Rate . 51
5.19 Data inactivity monitoring . 51
6 Protocol Data Units, formats and parameters . 52
6.1 Protocol Data Units . 52
6.1.1 General . 52
6.1.2 MAC PDU (DL-SCH and UL-SCH except transparent MAC and Random Access Response) . 52
6.1.3 MAC Control Elements (CEs) . 53
6.1.3.1 Buffer Status Report MAC CEs . 53
6.1.3.2 C-RNTI MAC CE . 58
6.1.3.3 UE Contention Resolution Identity MAC CE . 58
6.1.3.4 Timing Advance Command MAC CE . 58
6.1.3.5 DRX Command MAC CE . 59
6.1.3.6 Long DRX Command MAC CE . 59
6.1.3.7 Configured Grant Confirmation MAC CE . 59
6.1.3.8 Single Entry PHR MAC CE . 59
6.1.3.9 Multiple Entry PHR MAC CE . 60
6.1.3.10 SCell Activation/Deactivation MAC CEs . 62
6.1.3.11 Duplication Activation/Deactivation MAC CE. 63
6.1.3.12 SP CSI-RS/CSI-IM Resource Set Activation/Deactivation MAC CE . 63
6.1.3.13 Aperiodic CSI Trigger State Subselection MAC CE . 64
6.1.3.14 TCI States Activation/Deactivation for UE-specific PDSCH MAC CE . 65
6.1.3.15 TCI State Indication for UE-specific PDCCH MAC CE . 65
6.1.3.16 SP CSI reporting on PUCCH Activation/Deactivation MAC CE . 66
6.1.3.17 SP SRS Activation/Deactivation MAC CE . 67
6.1.3.18 PUCCH spatial relation Activation/Deactivation MAC CE. 68
6.1.3.19 SP ZP CSI-RS Resource Set Activation/Deactivation MAC CE . 69
6.1.3.20 Recommended bit rate MAC CE . 69
6.1.4 MAC PDU (transparent MAC) . 70
6.1.5 MAC PDU (Random Access Response) . 70
6.2 Formats and parameters . 71
6.2.1 MAC subheader for DL-SCH and UL-SCH . 71
6.2.2 MAC subheader for Random Access Response. 72
6.2.3 MAC payload for Random Access Response . 73
ETSI

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3GPP TS 38.321 version 15.8.0 Release 15 5 ETSI TS 138 321 V15.8.0 (2020-01)
7 Variables and constants . 73
7.1 RNTI values . 73
7.2 Backoff Parameter values . 74
7.3 DELTA_PREAMBLE values . 75
7.4 PRACH Mask Index values. 76
Annex A (informative): Change history . 77
History . 79

ETSI

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3GPP TS 38.321 version 15.8.0 Release 15 6 ETSI TS 138 321 V15.8.0 (2020-01)
Foreword
This Technical Specification has been produced by the 3rd Generation Partnership Project (3GPP).
The contents of the present document are subject to continuing work within the TSG and may change following formal
TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an
identifying change of release date and an increase in version number as follows:
Version x.y.z
where:
x the first digit:
1 presented to TSG for information;
2 presented to TSG for approval;
3 or greater indicates TSG approved document under change control.
y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections,
updates, etc.
z the third digit is incremented when editorial only changes have been incorporated in the document.
ETSI

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3GPP TS 38.321 version 15.8.0 Release 15 7 ETSI TS 138 321 V15.8.0 (2020-01)
1 Scope
The present document specifies the NR MAC protocol.
2 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present
document.
- References are either specific (identified by date of publication, edition number, version number, etc.) or
non-specific.
- For a specific reference, subsequent revisions do not apply.
- For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including
a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same
Release as the present document.
[1] 3GPP TR 21.905: "Vocabulary for 3GPP Specifications".
[2] 3GPP TS 38.300: "NR; Overall description; Stage 2".
[3] 3GPP TS 38.322: "NR; Radio Link Control (RLC) protocol specification".
[4] 3GPP TS 38.323: "NR; Packet Data Convergence Protocol (PDCP) protocol specification".
[5] 3GPP TS 38.331: "NR; Radio Resource Control (RRC); Protocol specification".
[6] 3GPP TS 38.213: "NR; Physical Layer Procedures for control".
[7] 3GPP TS 38.214: "NR; Physical Layer Procedures for data".
[8] 3GPP TS 38.211: "NR; Physical channels and modulation".
[9] 3GPP TS 38.212: "NR; Multiplexing and channel coding".
[10] Void.
[11] 3GPP TS 38.133: "NR; Requirements for support of radio resource management".
[12] 3GPP TS 36.133: "Evolved Universal Terrestrial Radio Access (E-UTRA); Requirements for
support of radio resource management".
[13] 3GPP TS 26.114: "Technical Specification Group Services and System Aspects; IP Multimedia
Subsystem (IMS); Multimedia Telephony; Media handling and interaction".
[14] 3GPP TS 38.101-1: "NR; User Equipment (UE) radio transmission and reception; Part 1: Range 1
Standalone".
[15] 3GPP TS 38.101-2: "NR; User Equipment (UE) radio transmission and reception; Part 2: Range 2
Standalone".
[16] 3GPP TS 38.101-3: "NR; User Equipment (UE) radio transmission and reception; Part 3: Range 1
and Range 2 Interworking operation with other radios".
[17] 3GPP TS 36.213: "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Layer
Procedures".
ETSI

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3GPP TS 38.321 version 15.8.0 Release 15 8 ETSI TS 138 321 V15.8.0 (2020-01)
3 Definitions, symbols and abbreviations
3.1 Definitions
For the purposes of the present document, the terms and definitions given in TR 21.905 [1] and the following apply. A
term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905 [1].
HARQ information: HARQ information for DL-SCH or for UL-SCH transmissions consists of New Data Indicator
(NDI), Transport Block size (TBS), Redundancy Version (RV), and HARQ process ID.
Msg3: Message transmitted on UL-SCH containing a C-RNTI MAC CE or CCCH SDU, submitted from upper layer
and associated with the UE Contention Resolution Identity, as part of a Random Access procedure.
PDCCH occasion: A time duration (i.e. one or a consecutive number of symbols) during which the MAC entity is
configured to monitor the PDCCH.
Serving Cell: A PCell, a PSCell, or an SCell in TS 38.331 [5].
Special Cell: For Dual Connectivity operation the term Special Cell refers to the PCell of the MCG or the PSCell of the
SCG depending on if the MAC entity is associated to the MCG or the SCG, respectively. Otherwise the term Special
Cell refers to the PCell. A Special Cell supports PUCCH transmission and contention-based Random Access, and is
always activated.
Timing Advance Group: A group of Serving Cells that is configured by RRC and that, for the cells with a UL
configured, using the same timing reference cell and the same Timing Advance value. A Timing Advance Group
containing the SpCell of a MAC entity is referred to as Primary Timing Advance Group (PTAG), whereas the term
Secondary Timing Advance Group (STAG) refers to other TAGs.
NOTE: A timer is running once it is started, until it is stopped or until it expires; otherwise it is not running. A
timer can be started if it is not running or restarted if it is running. A Timer is always started or restarted
from its initial value. The duration of a timer is not updated until they are stopped or expires (e.g. due to
BWP switching).
3.2 Abbreviations
For the purposes of the present document, the abbreviations given in TR 21.905 [1] and the following apply. An
abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in
TR 21.905 [1].
BSR Buffer Status Report
BWP Bandwidth Part
CE Control Element
CSI Channel State Information
CSI-IM CSI Intereference Measurement
CSI-RS CSI Reference Signal
CS-RNTI Configured Scheduling RNTI
INT-RNTI Interruption RNTI
LCG Logical Channel Group
LCP Logical Channel Prioritization
MCG Master Cell Group
NUL Normal Uplink
NZP CSI-RS Non-Zero Power CSI-RS
PHR Power Headroom Report
PTAG Primary Timing Advance Group
QCL Quasi-colocation
RS Reference Signal
SCG Secondary Cell Group
SFI-RNTI Slot Format Indication RNTI
SI System Information
SpCell Special Cell
ETSI

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