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TECHNICAL SPECIFICATION
5G;
NR;
Packet Data Convergence Protocol (PDCP) specification
(3GPP TS 38.323 version 15.4.0 Release 15)
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3GPP TS 38.323 version 15.4.0 Release 15 1 ETSI TS 138 323 V15.4.0 (2019-04)
Reference
RTS/TSGR-0238323vf40
Keywords
5G
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3GPP TS 38.323 version 15.4.0 Release 15 2 ETSI TS 138 323 V15.4.0 (2019-04)
Intellectual Property Rights
Essential patents
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pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
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Foreword
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, UMTS identities or
GSM identities. These should be interpreted as being references to the corresponding ETSI deliverables.
The cross reference between GSM, UMTS, 3GPP and ETSI identities can be found under
.
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI
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3GPP TS 38.323 version 15.4.0 Release 15 3 ETSI TS 138 323 V15.4.0 (2019-04)
Contents
Intellectual Property Rights . 2
Foreword . 2
Modal verbs terminology . 2
Foreword . 5
1 Scope . 6
2 References . 6
3 Definitions and abbreviations . 6
3.1 Definitions . 6
3.2 Abbreviations . 7
4 General . 7
4.1 Introduction . 7
4.2 Architecture . 7
4.2.1 PDCP structure . 7
4.2.2 PDCP entities . 8
4.3 Services . 9
4.3.1 Services provided to upper layers . 9
4.3.2 Services expected from lower layers . 9
4.4 Functions . 10
5 Procedures . 10
5.1 PDCP entity handling . 10
5.1.1 PDCP entity establishment . 10
5.1.2 PDCP entity re-establishment . 10
5.1.3 PDCP entity release . 11
5.1.4 PDCP entity suspend . 11
5.2 Data transfer . 12
5.2.1 Transmit operation . 12
5.2.2 Receive operation . 13
5.2.2.1 Actions when a PDCP Data PDU is received from lower layers . 13
5.2.2.2 Actions when a t-Reordering expires . 14
5.2.2.3 Actions when the value of t-Reordering is reconfigured . 14
5.3 SDU discard . 14
5.4 Status reporting . 15
5.4.1 Transmit operation . 15
5.4.2 Receive operation . 15
5.5 Data recovery . 15
5.6 Data volume calculation . 15
5.7 Header compression and decompression . 16
5.7.1 Supported header compression protocols and profiles . 16
5.7.2 Configuration of header compression . 17
5.7.3 Protocol parameters . 17
5.7.4 Header compression . 17
5.7.5 Header decompression . 18
5.7.6 PDCP Control PDU for interspersed ROHC feedback . 18
5.7.6.1 Transmit Operation . 18
5.7.6.2 Receive Operation . 18
5.8 Ciphering and deciphering . 18
5.9 Integrity protection and verification . 18
5.10 Handling of unknown, unforeseen, and erroneous protocol data . 19
5.11 PDCP duplication . 19
5.11.1 Activation/Deactivation of PDCP duplication . 19
5.11.2 Duplicate PDU discard . 19
6 Protocol data units, formats, and parameters . 20
6.1 Protocol data units . 20
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3GPP TS 38.323 version 15.4.0 Release 15 4 ETSI TS 138 323 V15.4.0 (2019-04)
6.1.1 Data PDU . 20
6.1.2 Control PDU . 20
6.2 Formats . 20
6.2.1 General . 20
6.2.2 Data PDU . 20
6.2.2.1 Data PDU for SRBs . 20
6.2.2.2 Data PDU for DRBs with 12 bits PDCP SN . 21
6.2.2.3 Data PDU for DRBs with 18 bits PDCP SN . 21
6.2.3 Control PDU . 22
6.2.3.1 Control PDU for PDCP status report . 22
6.2.3.2 Control PDU for interspersed ROHC feedback . 22
6.3 Parameters . 23
6.3.1 General . 23
6.3.2 PDCP SN . 23
6.3.3 Data . 23
6.3.4 MAC-I . 23
6.3.5 COUNT . 23
6.3.6 R . 24
6.3.7 D/C. 24
6.3.8 PDU type . 24
6.3.9 FMC . 24
6.3.10 Bitmap . 24
6.3.11 Interspersed ROHC feedback . 25
7 State variables, constants, and timers . 25
7.1 State variables . 25
7.2 Constants . 25
7.3 Timers . 25
Annex A (informative): Change history . 26
History . 27
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3GPP TS 38.323 version 15.4.0 Release 15 5 ETSI TS 138 323 V15.4.0 (2019-04)
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 38.323 version 15.4.0 Release 15 6 ETSI TS 138 323 V15.4.0 (2019-04)
1 Scope
The present document provides the description of the Packet Data Convergence Protocol (PDCP).
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: "NG Radio Access Network; Overall description".
[3] 3GPP TS 38.331: "NR Radio Resource Control (RRC); Protocol Specification".
[4] 3GPP TS 38.321: "NR Medium Access Control (MAC) protocol specification".
[5] 3GPP TS 38.322: "NR Radio Link Control (RLC) protocol specification".
[6] 3GPP TS 33.501: "Security Architecture and Procedures for 5G System ".
[7] IETF RFC 5795: "The RObust Header Compression (ROHC) Framework".
[8] IETF RFC 3095: "RObust Header Compression (ROHC): Framework and four profiles: RTP,
UDP, ESP and uncompressed".
[9] IETF RFC 4815: "RObust Header Compression (ROHC): Corrections and Clarifications to RFC
3095".
[10] IETF RFC 6846: "RObust Header Compression (ROHC): A Profile for TCP/IP (ROHC-TCP)".
[11] IETF RFC 5225: "RObust Header Compression (ROHC) Version 2: Profiles for RTP, UDP, IP,
ESP and UDP Lite".
[12] 3GPP TS 36.321: "Evolved Universal Terrestrial Radio Access (E-UTRA) Medium Access
Control (MAC) protocol specification".
3 Definitions 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].
AM DRB: a data radio bearer which utilizes RLC AM.
Non-split bearer: a bearer whose radio protocols are located in either the MgNB or the SgNB to use MgNB or SgNB
resource, respectively.
PDCP data volume: the amount of data available for transmission in a PDCP entity.
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Split bearer: in dual connectivity, a bearer whose radio protocols are located in both the MgNB and the SgNB to use
both MgNB and SgNB resources.
UM DRB: a data radio bearer which utilizes RLC UM.
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].
AM Acknowledged Mode
CID Context Identifier
DRB Data Radio Bearer carrying user plane data
gNB NR Node B
HFN Hyper Frame Number
IETF Internet Engineering Task Force
IP Internet Protocol
MAC Medium Access Control
MAC-I Message Authentication Code for Integrity
PDCP Packet Data Convergence Protocol
PDU Protocol Data Unit
RB Radio Bearer
RFC Request For Comments
RLC Radio Link Control
ROHC RObust Header Compression
RRC Radio Resource Control
RTP Real Time Protocol
SAP Service Access Point
SDU Service Data Unit
SN Sequence Number
SRB Signalling Radio Bearer carrying control plane data
TCP Transmission Control Protocol
UDP User Datagram Protocol
UE User Equipment
UM Unacknowledged Mode
X-MAC Computed MAC-I
4 General
4.1 Introduction
The present document describes the functionality of the PDCP.
4.2 Architecture
4.2.1 PDCP structure
Figure 4.2.1.1 represents one possible structure for the PDCP sublayer; it should not restrict implementation. The figure
is based on the radio interface protocol architecture defined in TS 38.300 [2].
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Figure 4.2.1-1: PDCP layer, structure view
The PDCP sublayer is configured by upper layers TS 38.331 [3]. The PDCP sublayer is used for RBs mapped on
DCCH and DTCH type of logical channels. The PDCP sublayer is not used for any other type of logical channels.
Each RB (except for SRB0) is associated with one PDCP entity. Each PDCP entity is associated with one, two, or four
RLC entities depending on the RB characteristic (e.g uni-directional/bi-directional or split/non-split) or RLC mode. For
non-split bearers, each PDCP entity is associated with one UM RLC entity, two UM RLC entities (one for each
direction), or one AM RLC entity. For split bearers, each PDCP entity is associated with two UM RLC entities (for
same direction), four UM RLC entities (two for each direction), or two AM RLC entities (for same direction).
4.2.2 PDCP entities
The PDCP entities are located in the PDCP sublayer. Several PDCP entities may be defined for a UE. Each PDCP
entity is carrying the data of one radio bearer.
A PDCP entity is associated either to the control plane or the user plane depending on which radio bearer it is carrying
data for.
Figure 4.2.2.1 represents the functional view of the PDCP entity for the PDCP sublayer; it should not restrict
implementation. The figure is based on the radio interface protocol architecture defined in TS 38.300 [2].
For split bearers, routing is performed in the transmitting PDCP entity.
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3GPP TS 38.323 version 15.4.0 Release 15 9 ETSI TS 138 323 V15.4.0 (2019-04)
Figure 4.2.2-1: PDCP layer, functional view
4.3 Services
4.3.1 Services provided to upper layers
The PDCP layer provides its services to the RRC or SDAP layers. The following services are provided by PDCP to
upper layers:
- transfer of user plane data;
- transfer of control plane data;
- header compression;
- ciphering;
- integrity protection.
The maximum supported size of a PDCP SDU is 9000 bytes. The maximum supported size of a PDCP Control PDU is
9000 bytes.
4.3.2 Services expected from lower layers
A PDCP entity expects the following services from lower layers per RLC entity (for a detailed description see TS
38.322 [5]):
- acknowledged data transfer service, including indication of successful delivery of PDCP PDUs;
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3GPP TS 38.323 version 15.4.0 Release 15 10 ETSI TS 138 323 V15.4.0 (2019-04)
- unacknowledged data transfer service.
4.4 Functions
The PDCP layer supports the following functions:
- transfer of data (user plane or control plane);
- maintenance of PDCP SNs;
- header compression and decompression using the ROHC protocol;
- ciphering and deciphering;
- integrity protection and integrity verification;
- timer based SDU discard;
- for split bearers, routing;
- duplication;
- reordering and in-order delivery;
- out-of-order delivery;
- duplicate discarding.
5 Procedures
5.1 PDCP entity handling
5.1.1 PDCP entity establishment
When upper layers request a PDCP entity establishment for a radio bearer, the UE shall:
- establish a PDCP entity for the radio bearer;
- set the state variables of the PDCP entity to initial values;
- follow the procedures in subclause 5.2.
5.1.2 PDCP entity re-establishment
When upper layers request a PDCP entity re-establishment, the UE shall additionally perform once the procedures
described in this section. After performing the procedures in this section, the UE shall follow the procedures in
subclause 5.2.
When upper layers request a PDCP entity re-establishment, the transmitting PDCP entity shall:
- for UM DRBs and AM DRBs, reset the header compression protocol for uplink and start with an IR state in U-
mode (as defined in RFC 3095 [8] and RFC 4815 [9]) if drb-ContinueROHC is not configured in TS 38.331 [3];
- for UM DRBs and SRBs, set TX_NEXT to the initial value;
- for SRBs, discard all stored PDCP SDUs and PDCP PDUs;
- apply the ciphering algorithm and key provided by upper layers during the PDCP entity re-establishment
procedure;
- apply the integrity protection algorithm and key provided by upper layers during the PDCP entity re-
establishment procedure;
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- for UM DRBs, for each PDCP SDU already associated with a PDCP SN but for which a corresponding PDU has
not previously been submitted to lower layers:
- consider the PDCP SDUs as received from upper layer;
- perform transmission of the PDCP SDUs in ascending order of the COUNT value associated to the PDCP
SDU prior to the PDCP re-establishment without restarting the discardTimer, as specified in subclause 5.2.1;
- for AM DRBs, from the first PDCP SDU for which the successful delivery of the corresponding PDCP Data
PDU has not been confirmed by lower layers, perform retransmission or transmission of all the PDCP SDUs
already associated with PDCP SNs in ascending order of the COUNT values associated to the PDCP SDU prior
to the PDCP entity re-establishment as specified below:
- perform header compression of the PDCP SDU as specified in the subclause 5.7.4;
- perform integrity protection and ciphering of the PDCP SDU using the COUNT value associated with this
PDCP SDU as specified in the subclause 5.9 and 5.8;
- submit the resulting PDCP Data PDU to lower layer, as specified in subclause 5.2.1.
When upper layers request a PDCP entity re-establishment, the receiving PDCP entity shall:
- process the PDCP Data PDUs that are received from lower layers due to the re-establishment of the lower layers,
as specified in the subclause 5.2.2.1;
- for SRBs, discard all stored PDCP SDUs and PDCP PDUs;
- for SRBs and UM DRBs, if t-Reordering is running:
- stop and reset t-Reordering;
- for UM DRBs, deliver all stored PDCP SDUs to the upper layers in ascending order of associated COUNT
values after performing header decompression;
- for AM DRBs, perform header decompression for all stored PDCP SDUs if drb-ContinueROHC is not
configured in TS 38.331 [3];
- for UM DRBs and AM DRBs, reset the header compression protocol for downlink and start with NC state in U-
mode (as defined in RFC 3095 [8] and RFC 4815 [9]) if drb-ContinueROHC is not configured in TS 38.331 [3];
- for UM DRBs and SR
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