Content for TS 37.324 Word version: 18.0.0
1 Scope
2 References
3 Definitions, symbols and abbreviations
4 General
4.1 Introduction
4.2 SDAP architecture
4.3 Services
4.4 Functions
...
...
1 Scope p. 6
The present document specifies the Service Data Adaptation Protocol (SDAP) for a UE with connection to the 5G-CN or for a UE in NR sidelink communication.
2 References p. 6
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]
TR 21.905: "Vocabulary for 3GPP Specifications".
[2]
TS 38.300: "NG Radio Access Network; Overall description".
[3]
TS 38.331: "NR Radio Resource Control (RRC); Protocol Specification".
[4]
TS 23.501: "System Architecture for the 5G System".
[5]
TS 23.287: "Architecture enhancements for 5G System (5GS) to support Vehicle-to-Everything (V2X) services".
[6]
TS 24.587: "Vehicle-to-Everything (V2X) services in 5G System (5GS); Stage 3".
3 Definitions, symbols and abbreviations p. 6
3.1 Definitions p. 6
For the purposes of the present document, the terms and definitions given in TR 21.905 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.
PC5 QoS flow to SL-DRB mapping rule:
a mapping rule determining on which SL-DRB packets of a PC5 QoS flow shall be carried.
QoS flow to DRB mapping rule:
a mapping rule determining on which DRB packets of a QoS flow shall be carried.
Reflective QoS flow to DRB mapping:
a QoS flow to DRB mapping scheme where a UE monitors the QoS flow to DRB mapping rule in the DL, and applies it to in the UL.
NR sidelink communication:
AS functionality enabling at least V2X communication as defined in TS 23.287, between two or more nearby UEs, using NR technology but not traversing any network node.
3.2 Abbreviations p. 6
For the purposes of the present document, the abbreviations given in TR 21.905 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.
PQFI
PC5 QoS Flow ID
QFI
QoS Flow ID
RDI
Reflective QoS flow to DRB mapping Indication
RQI
Reflective QoS Indication
SDAP
Service Data Adaptation Protocol
SL
Sidelink
SL-DRB
Sidelink Data Radio Bearer
4 General p. 7
4.1 Introduction p. 7
The objective is to describe the SDAP architecture and the SDAP entity from a functional point of view. The specified functionality only applies to UE with connection to the 5G-CN and UE in NR sidelink communication.
4.2 SDAP architecture p. 7
4.2.1 SDAP structure p. 7
Figure 4.2.1-1 illustrates one possible structure for the SDAP sublayer; it should not restrict implementation. The figure is based on the radio interface protocol architecture defined in TS 38.300.
The SDAP sublayer is configured for DRBs by RRC (TS 38.331). The SDAP sublayer maps QoS flows to DRBs. One or more QoS flows may be mapped onto one DRB. One QoS flow is mapped onto only one DRB at a time in the UL.
The SDAP sublayer is configured for MRBs by RRC (TS 38.331). The SDAP sublayer maps MBS QoS flows to MRBs. One or more MBS QoS flows may be mapped onto one MRB.
In NR sidelink communication, the SDAP sublayer maps PC5 QoS flows to SL-DRBs. One or more PC5 QoS flows may be mapped onto one SL-DRB. One PC5 QoS flow is mapped onto only one SL-DRB at a time in the NR sidelink for transmission.
4.2.2 SDAP entities p. 8
The SDAP entities are located in the SDAP sublayer. Several SDAP entities may be defined for a UE. There is an SDAP entity configured for each individual PDU session or MBS session for NR Uu. For NR sidelink, SDAP entity is configured per Destination Layer-2 ID and cast type in the UE.
An SDAP entity receives/delivers SDAP SDUs from/to upper layers and submits/receives SDAP data PDUs to/from its peer SDAP entity via lower layers.
- At the transmitting side, when an SDAP entity receives an SDAP SDU from upper layers, it constructs the corresponding SDAP data PDU and submits it to lower layers;
- At the receiving side, when an SDAP entity receives an SDAP data PDU from lower layers, it retrieves the corresponding SDAP SDU and delivers it to upper layers.
Reflective QoS flow to DRB mapping is performed at UE, as specified in the clause 5.3.2, if DL SDAP header is configured.
Reflective QoS flow to MRB mapping is not supported. There is no SDAP header for MRB.
For NR sidelink communication, reflective PC5 QoS flow to SL-DRB mapping is not supported.
4.3 Services p. 9
4.3.1 Services provided to upper layers p. 9
The SDAP sublayer provides its service to the user plane upper layers. The following services are provided by SDAP to upper layers:
- transfer of user plane data.
4.3.2 Services expected from lower layers p. 9
An SDAP entity expects the following services from lower layers:
- user plane data transfer service;
- in-order delivery except when out of order delivery is configured by RRC (TS 38.331).
4.4 Functions p. 9
The SDAP sublayer supports the following functions:
- transfer of user plane data;
- mapping between a QoS flow and a DRB for both DL and UL;
- mapping between an MBS QoS flow and an MRB for DL;
- mapping between a PC5 QoS flow and a SL-DRB for NR sidelink communication;
- marking QoS flow ID in both DL and UL packets;
- marking PC5 QoS flow ID in unicast of NR sidelink communication packets;
- reflective QoS flow to DRB mapping for the UL SDAP data PDUs.
