ETSI TS 136 323 V15.4.0 (2019-07)

TECHNICAL SPECIFICATION
LTE;
Evolved Universal Terrestrial Radio Access (E-UTRA);
Packet Data Convergence Protocol (PDCP) specification
(3GPP TS 36.323 version 15.4.0 Release 15)

3GPP TS 36.323 version 15.4.0 Release 15 1 ETSI TS 136 323 V15.4.0 (2019-07)

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RTS/TSGR-0236323vf40
Keywords
LTE
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3GPP TS 36.323 version 15.4.0 Release 15 2 ETSI TS 136 323 V15.4.0 (2019-07)
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Contents
Intellectual Property Rights . 2
Legal Notice . 2
Modal verbs terminology . 2
Foreword . 6
1 Scope . 7
2 References . 7
3 Definitions and abbreviations . 8
3.1 Definitions . 8
3.2 Abbreviations . 8
4 General . 9
4.1 Introduction . 9
4.2 PDCP architecture . 9
4.2.1 PDCP structure . 9
4.2.2 PDCP entities . 10
4.3 Services . 12
4.3.1 Services provided to upper layers . 12
4.3.2 Services expected from lower layers . 13
4.4 Functions . 13
4.5 Data available for transmission . 13
5 PDCP procedures . 15
5.1 PDCP Data Transfer Procedures . 15
5.1.1 UL Data Transfer Procedures . 15
5.1.2 DL Data Transfer Procedures . 16
5.1.2.1 Procedures for DRBs. 16
5.1.2.1.1 Void . 16
5.1.2.1.2 Procedures for DRBs mapped on RLC AM when the reordering function is not used . 16
5.1.2.1.2a RN procedures for DRBs mapped on RLC AM . 17
5.1.2.1.3 Procedures for DRBs mapped on RLC UM when the reordering function is not used . 17
5.1.2.1.3a RN procedures for DRBs mapped on RLC UM . 18
5.1.2.1.4 Procedures for DRBs mapped on RLC AM or RLC UM, for LWA bearers and SLRB when
the reordering function is used . 18
5.1.2.1.4.1 Procedures when a PDCP PDU is received from the lower layers . 18
5.1.2.1.4.2 Procedures when t-Reordering expires . 20
5.1.2.1.4.3 Procedures when the value of t-Reordering is reconfigured . 20
5.1.2.2 Procedures for SRBs when the PDCP duplication function is not used . 20
5.1.3 SL Data Transmission Procedures . 21
5.1.4 SL Data Reception Procedures . 21
5.2 Re-establishment procedure . 22
5.2.1 UL Data Transfer Procedures . 22
5.2.1.1 Procedures for DRBs mapped on RLC AM . 22
5.2.1.2 Procedures for DRBs mapped on RLC UM . 22
5.2.1.3 Procedures for SRBs . 23
5.2.2 DL Data Transfer Procedures . 23
5.2.2.1 Procedures for DRBs mapped on RLC AM while the reordering function is not used . 23
5.2.2.1a Procedures for DRBs mapped on RLC AM while the reordering function is used . 23
5.2.2.2 Procedures for DRBs mapped on RLC UM when the reordering function is not used . 24
5.2.2.2a Procedures for DRBs mapped on RLC UM when the reordering function is used . 24
5.2.2.3 Procedures for SRBs . 24
5.2.2.4 Procedures for LWA bearers . 24
5.3 PDCP Status Report . 25
5.3.1 Transmit operation . 25
5.3.2 Receive operation . 25
5.4 PDCP discard . 25
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5.4a Duplicate PDCP discard . 25
5.5 Header Compression and Decompression . 26
5.5.1 Supported header compression protocols and profiles . 26
5.5.2 Configuration of header compression . 26
5.5.3 Protocol parameters . 27
5.5.4 Header compression . 27
5.5.5 Header decompression . 27
5.5.6 PDCP Control PDU for interspersed ROHC feedback packet . 28
5.5.6.1 Transmit Operation . 28
5.5.6.2 Receive Operation . 28
5.6 Ciphering and Deciphering. 28
5.6.0 General . 28
5.6.1 SL Ciphering and Deciphering for one-to-many communication . 28
5.6.2 SL Ciphering and Deciphering for one-to-one communication . 29
5.6.3 Handling of LWA end-marker PDCP Control PDU . 29
5.6.3.1 Transmit operation . 29
5.6.3.2 Receive Operation . 29
5.7 Integrity Protection and Verification . 30
5.8 Handling of unknown, unforeseen and erroneous protocol data . 30
5.9 PDCP Data Recovery procedure . 30
5.10 Status report for LWA . 31
5.10.1 Transmit operation . 31
5.10.2 LWA status report . 31
5.10.3 Receive operation . 32
5.11 Uplink Data compression and decompression . 32
5.11.1 UDC protocol. 32
5.11.2 Configuration of UDC . 32
5.11.3 UDC header . 32
5.11.4 Uplink data compression . 32
5.11.5 Pre-defined dictionary . 33
5.11.6 UDC buffer reset procedure . 33
5.11.7 UDC checksum error handling . 33
6 Protocol data units, formats and parameters . 33
6.1 Protocol data units . 33
6.1.1 PDCP Data PDU . 33
6.1.2 PDCP Control PDU . 33
6.2 Formats . 34
6.2.1 General . 34
6.2.2 Control plane PDCP Data PDU . 34
6.2.3 User plane PDCP Data PDU with long PDCP SN (12 bits) . 34
6.2.4 User plane PDCP Data PDU with short PDCP SN (7 bits) . 35
6.2.5 PDCP Control PDU for interspersed ROHC feedback packet . 35
6.2.6 PDCP Control PDU for PDCP status report . 36
6.2.7 Void . 37
6.2.8 RN user plane PDCP Data PDU with integrity protection. 37
6.2.9 User plane PDCP Data PDU with extended PDCP SN (15 bits) . 37
6.2.10 User plane PDCP Data PDU for SLRB . 38
6.2.11 User plane PDCP Data PDU with further extended PDCP SN (18 bits) . 39
6.2.12 PDCP Control PDU for LWA status report . 39
6.2.13 PDCP Control PDU for LWA end-marker packet . 41
6.2.14 User plane PDCP Data PDU with long PDCP SN (12 bits) for UDC . 41
6.2.15 User plane PDCP Data PDU with extended PDCP SN (15 bits) for UDC . 42
6.2.16 User plane PDCP Data PDU with further extended PDCP SN (18 bits) for UDC . 42
6.2.17 PDCP Control PDU for UDC feedback packet. 42
6.3 Parameters . 43
6.3.1 General . 43
6.3.2 PDCP SN . 43
6.3.3 Data . 43
6.3.4 MAC-I . 43
6.3.5 COUNT . 43
6.3.6 R . 44
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6.3.7 D/C. 44
6.3.8 PDU type . 44
6.3.9 FMS . 44
6.3.10 Bitmap . 44
6.3.11 Interspersed ROHC feedback packet . 45
6.3.12 PGK Index . 45
6.3.13 PTK Identity . 45
6.3.14 SDU Type . 45
6.3.15 K ID . 45
D-sess
6.3.16 NMP. 46
6.3.17 HRW . 46
6.3.18 P . 46
6.3.19 LSN . 46
6.3.21 FU . 46
6.3.22 FR . 47
6.3.23 Checksum . 47
6.3.24 FE. 47
7 Variables, constants and timers . 47
7.1 State variables . 47
7.2 Timers . 48
7.3 Constants . 49
Annex A (informative): An example of UDC Checksum calculation . 50
Annex B (informative): Change history . 51
History . 53

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Foreword
rd
This Technical Specification has been produced by the 3 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.
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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 36.300: "Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal
Terrestrial Radio Access Network (E-UTRAN); Overall description".
[3] 3GPP TS 36.331: "Evolved Universal Terrestrial Radio Access (E-UTRA) Radio Resource
Control (RRC); Protocol Specification".
[4] 3GPP TS 36.321: "Evolved Universal Terrestrial Radio Access (E-UTRA) Medium Access
Control (MAC) protocol specification".
[5] 3GPP TS 36.322: "Evolved Universal Terrestrial Radio Access (E-UTRA) Radio Link Control
(RLC) protocol specification".
[6] 3GPP TS 33.401: "3GPP System Architecture Evolution: Security Architecture".
[7] IETF RFC 5795: "The RObust Header Compression (ROHC) Framework".
[8] IETF RFC 6846: "RObust Header Compression (ROHC): A Profile for TCP/IP (ROHC-TCP)".
[9] IETF RFC 3095: "RObust Header Compression (ROHC): Framework and four profiles: RTP,
UDP, ESP and uncompressed".
[10] IETF RFC 3843: "RObust Header Compression (ROHC): A Compression Profile for IP".
[11] IETF RFC 4815: "RObust Header Compression (ROHC): Corrections and Clarifications to RFC
3095".
[12] IETF RFC 5225: "RObust Header Compression (ROHC) Version 2: Profiles for RTP, UDP, IP,
ESP and UDP Lite".
[13] 3GPP TS 33.303: "Proximity-based Services; Security Aspects".
[14] 3GPP TS 23.303: "Proximity-based Services; Stage 2".
[15] 3GPP TS 36.360: "Evolved Universal Terrestrial Radio Access (E-UTRA); LTE-WLAN
Aggregation Adaptation Protocol (LWAAP) specification".
[16] IETF RFC 1951: "DEFLATE Compressed Data Format Specification version 1.3".
[17] IETF RFC 3485: "The Session Initiation Protocol (SIP) and Session Description Protocol (SDP)
Static Dictionary for Signaling Compression (SigComp)".
[18] IETF RFC 1979: "PPP Deflate Protocol".
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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].
NB-IoT: NB-IoT allows access to network services via E-UTRA with a channel bandwidth limited to 200 kHz.
Split bearer: in dual connectivity, a bearer whose radio protocols are located in both the MeNB and the SeNB to use
both MeNB and SeNB resources.
LWA bearer: in LTE-WLAN Aggregation, a bearer whose radio protocols are located in both the eNB and the WLAN
to use both eNB and WLAN resources.
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].
AILC Assistance Information bit for Local Cache
AM Acknowledged Mode
ARP Address Resolution Protocol
CID Context Identifier
DRB Data Radio Bearer carrying user plane data
EPS Evolved Packet System
E-UTRA Evolved UMTS Terrestrial Radio Access
E-UTRAN Evolved UMTS Terrestrial Radio Access Network
eNB E-UTRAN Node B
FIFO First In First Out
FMS First missing PDCP SN
HFN Hyper Frame Number
HRW Highest Received PDCP SN on WLAN
IETF Internet Engineering Task Force
IP Internet Protocol
L2 Layer 2 (data link layer)
L3 Layer 3 (network layer)
LWA LTE-WLAN Aggregation
MAC Medium Access Control
MAC-I Message Authentication Code for Integrity
MCG Master Cell Group
NB-IoT Narrow Band Internet of Things
NMP Number of Missing PDCP SDUs
PDCP Packet Data Convergence Protocol
PDU Protocol Data Unit
PEK ProSe Encryption Key
PGK ProSe Group Key
ProSe Proximity-based Services
PTK ProSe Traffic Key
R Reserved
RB Radio Bearer
RFC Request For Comments
RLC Radio Link Control
RN Relay Node
ROHC RObust Header Compression
RRC Radio Resource Control
RTP Real Time Protocol
SAP Service Access Point
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SCG Secondary Cell Group
SDU Service Data Unit
SLRB Sidelink Radio Bearer carrying Sidelink Communication or V2X sidelink communication data
SN Sequence Number
SRB Signalling Radio Bearer carrying control plane data
TCP Transmission Control Protocol
UDC Uplink Data Compression
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. Functionality specified for the UE equally applies to the
RN for functionality necessary for the RN. There is also functionality which is only applicable to the RN in its
communication with the E-UTRAN, in which case the specification denotes the RN instead of the UE. RN-specific
behaviour is not applicable to the UE. The functionality specified for the UE applies to communication on Uu interface
and PC5 interface [14].
4.2 PDCP 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 36.300 [2].

Figure 4.2.1.1 - PDCP layer, structure view
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Each RB (i.e. DRB, SLRB and SRB, except for SRB0 and SRB1bis) is associated with one PDCP entity. Each PDCP
entity is associated with one, two, or four (e.g uni-directional/bi-directional or split/non-split) RLC entities depending
on the RB characteristic (i.e. uni-directional or bi-directional) or RLC mode:
- For split bearers or for RBs configured with PDCP duplication, each PDCP entity is associated with two (bi-
directional) AM RLC entities, two (for same direction) UM RLC entities or four (uni-directional) UM RLC
entities.
- For LWA bearers, each PDCP entity is associated with one (bi-directional) AM RLC entity or two (uni-
directional) UM RLC entities and the LWAAP entity.
- Otherwise, each PDCP entity is associated with one UM RLC entity, two UM RLC entities (one for each
direction), or one AM RLC entity (bi-directional).
PDCP entities are located in the PDCP sublayer. The PDCP sublayer is configured by upper layers, see TS 36.331 [3].
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 carrying user plane data may be configured to use either uplink data compression (UDC) or to use header
compression.
Each PDCP entity is carrying the data of one radio bearer. In this version of the specification, the robust header
compression protocol (ROHC) and UDC, are supported. Every PDCP entity uses at most one ROHC or one UDC
compressor instance and at most one ROHC or UDC decompressor instance. ROHC and UDC are not supported
simultaneously for the same 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 36.300 [2].
For RNs, integrity protection and verification are also performed for the u-plane.
For split and LWA bearers, routing is performed in the transmitting PDCP entity, and reordering is performed in the
receiving PDCP entity.
For PDCP duplication, submission of duplicates is performed in the transmitting PDCP entity, and duplicate discard is
performed in the receiving PDCP entity.
For split bearers, except when PDCP duplication is configured and activated, when requested by lower layers to submit
PDCP PDUs, the transmitting PDCP entity shall:
- if ul-DataSplitThreshold is configured and the data available for transmission is larger than or equal to ul-
DataSplitThreshold:
- submit the PDCP PDUs to either the associated RLC entity configured for SCG or the associated RLC entity
configured for MCG, whichever the PDUs were requested by;
- else:
- if ul-DataSplitDRB-ViaSCG is set to TRUE by upper layers, see TS 36.331 [3]:
- if the PDUs were requested by the associated lower layers configured for SCG:
- submit the PDCP PDUs to the associated RLC entity configured for SCG;
- else:
- if the PDUs were requested by the associated lower layers configured for MCG:
- submit the PDCP PDUs to the associated RLC entity configured for MCG.
For LWA bearers, when submitting PDCP PDUs to lower layers, the transmitting PDCP entity shall:
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- if ul-LWA-DataSplitThreshold is configured and the data available for transmission is larger than or equal to ul-
LWA-DataSplitThreshold:
- submit the PDCP PDUs to either the associated RLC entity upon request from lower layers or the associated
LWAAP entity;
- else:
- if ul-LWA-DRB-ViaWLAN is set to TRUE by upper layers,see TS 36.331 [3]:
- submit the PDCP PDUs to the associated LWAAP entity;
- else:
- submit the PDCP PDUs to the associated RLC entity upon request from lower layers.
NOTE: The selection of PDCP PDUs submitted to the associated LWAAP entity is left up to the UE
implementation.
For bearers configured with PDCP duplication, when requested by lower layers to submit the PDCP PDUs, the
transmitting PDCP entity shall:
- if PDCP duplication is activated:
- if the PDCP PDU is a PDCP Data PDU:
- duplicate the PDCP Data PDU and submit the PDCP Data PDU to the associated RLC entities;
- else:
- submit the PDCP Control PDU to the primary RLC entity;
- else:
- submit the PDCP PDU to the associated RLC entity.
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Figure 4.2.2.1 - PDCP layer, functional view
4.3 Services
4.3.1 Services provided to upper layers
PDCP provides its services to the RRC and user plane upper layers at the UE or to the relay at the evolved Node B
(eNB). The following services are provided by PDCP to upper layers:
- transfer of user plane data;
- transfer of control plane data;
- header compression;
- uplink data compression;
- ciphering;
- integrity protection.
The maximum supported size of a PDCP SDU is 8188 octets, except in NB-IoT for which the maximum supported size
of a PDCP SDU is 1600 octets. The maximum supported size of a PDCP Control PDU is 8188 octets except in NB-IoT
for which the maximum supported size of PDCP Control PDU is 1600 octets.
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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
36.322 [5]):
- acknowledged data transfer service, including indication of successful delivery of PDCP PDUs;
- unacknowledged data transfer service;
- in-sequence delivery, except at re-establishment of lower layers;
- duplicate discarding, except at re-establishment of lower layers.
A PDCP entity expects the following services from the LWAAP entity (for a detailed description see TS 36.360 [15]):
- user plane data transfer service;
4.4 Functions
The Packet Data Convergence Protocol supports the following functions:
- header compression and decompression of IP data flows using the ROHC protocol;
- compression and decompression of uplink PDCP SDU;
- transfer of data (user plane or control plane);
- maintenance of PDCP SNs;
- in-sequence delivery of upper layer PDUs at re-establishment of lower layers;
- duplicate elimination of lower layer SDUs at re-establishment of lower layers for radio bearers mapped on RLC
AM;
- ciphering and deciphering of user plane data and control plane data;
- integrity protection and integrity verification of control plane data;
- integrity protection and integrity verification of sidelink one-to-one communication data;
- for RNs, integrity protection and integrity verification of user plane data;
- timer based discard;
- duplicate transmission and duplicate discarding;
- for split and LWA bearers, routing and reordering.
PDCP uses the services provided by the RLC sublayer and the LWAAP sublayer.
PDCP is used for SRBs, DRBs, and SLRBs mapped on DCCH, DTCH, and STCH type of logical channels. PDCP is
not used for any other type of logical channels. PDCP is not used for SRB1bis.
4.5 Data available for transmission
For the purpose of MAC buffer status reporting, the UE shall consider PDCP Control PDUs, as well as the following as
data available for transmission in the PDCP layer:
For SDUs for which no PDU has been submitted to lower layers:
- the SDU itself, if the SDU has not yet been processed by PDCP, or
- the PDU if the SDU has been processed by PDCP.
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In addition, for radio bearers that are mapped on RLC AM, if the PDCP entity has previously performed the re-
establishment procedure, the UE shall also consider the following as data available for transmission in the PDCP layer:
For SDUs for which a corresponding PDU has only been submitted to lower layers prior to the PDCP re-
establishment, starting from the first SDU for which the delivery of the corresponding PDUs has not been
confirmed by the lower layer, except the SDUs which are indicated as successfully delivered by the PDCP
status report, if received:
- the SDU, if it has not yet been processed by PDCP, or
- the PDU once it has been processed by PDCP.
For radio bearers that are mapped on RLC AM, if the PDCP entity has previously performed the data recovery
procedure, the UE shall also consider as data available for transmission in the PDCP layer, all the PDCP PDUs that
have only been submitted to re-established AM RLC entity prior to the PDCP data recovery, starting from the first
PDCP PDU whose successful delivery has not been confirmed by lower layers, except the PDUs which are indicated as
successfully delivered by the PDCP status report, if received.
In addition, for bearers configured with PDCP duplication, when PDCP duplication is activated, for SDUs for which a
PDU has only been submitted to lower layers associated with one logical channel, for the purpose of MAC buffer status
reporting associated with the other logical channel the UE shall consider:
- the PDU, if the PDU has not yet been confirmed to be successfully delivered by those lower layers.
For split bearers, when indicating the data available for transmission to a MAC entity for BSR triggering and Buffer
Size calculation, the UE shall:
- if ul-DataSplitThreshold is configured and the data available for transmission is larger than or equal to ul-
DataSplitThreshold:
- indicate the data available for transmission to both the MAC entity configured for SCG and the MAC entity
configured for MCG;
- else:
- if ul-DataSplitDRB-ViaSCG is set to TRUE by upper layer, see TS 36.331 [3]:
- indicate the data available for transmission to the MAC entity configured for SCG only;
- if ul-DataSplitThreshold is configured, indicate the data available for transmission as 0 to the MAC entity
configured for MCG;
- else:
- indicate the data available for transmission to the MAC entity configured for MCG only;
- if ul-DataSplitThreshold is configured, indicate the data available for transmission as 0 to the MAC entity
configured for SCG.
For uplink LWA bearers, when indicating the data available for transmission to the MAC entity for BSR triggering and
Buffer Size calculation, the UE shall:
- if ul-LWA-DataSplitThreshold is configured and the data available for transmission is larger than or equal to ul-
LWA-DataSplitThreshold:
- indicate the data available for transmission to the MAC entity;
- else:
- if ul-LWA-DRB-ViaWLAN is set to TRUE by upper layers, see TS 36.331 [3]:
- indicate the data available for transmission as 0 to the MAC entity;
- else:
- indicate the data available for transmission to the MAC entity.
ETSI
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