Content for TS 37.483 Word version: 17.3.0
1 Scope
2 References
3 Definitions and abbreviations
3.1 Definitions
3.2 Abbreviations
4 General
4.1 Procedure specification principles
4.2 Forwards and backwards compatibility
4.3 Specification notations
5 E1AP services
6 Services expected from signalling transport
7 Functions of E1AP
...
...
1 Scope p. 12
The present document specifies the 5G radio network layer signalling protocol for the E1 interface. The E1 interface provides means for interconnecting a gNB-CU-CP and a gNB-CU-UP of a gNB within an NG-RAN, or for interconnecting a gNB-CU-CP and a gNB-CU-UP of an en-gNB within an E-UTRAN, or for interconnecting an eNB-CP and an eNB-UP of an eNB within an E-UTRAN, or for interconnecting an ng-eNB-CU-CP and an ng-eNB-CU-UP of an ng-eNB within an NG-RAN. The E1 Application Protocol (E1AP) supports the functions of E1 interface by signalling procedures defined in the present document. E1AP is developed in accordance to the general principles stated in TS 38.401 and TS 37.480.
2 References p. 12
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 38.401: "NG-RAN; Architecture Description".
[3]
TS 37.480: "E1 general aspects and principles".
[4]
TS 38.300: "NR; Overall description; Stage-2".
[5]
TR 25.921: (version.7.0.0) "Guidelines and principles for protocol description and error".
[6]
TS 38.413: "NG-RAN; NG Application Protocol (NGAP)".
[7]
ITU-T Recommendation X.691 (2002-07): "Information technology - ASN.1 encoding rules - Specification of Packed Encoding Rules (PER)".
[8]
ITU-T Recommendation X.680 (07/2002): "Information technology - Abstract Syntax Notation One (ASN.1): Specification of basic notation".
[9]
ITU-T Recommendation X.681 (07/2002): "Information technology - Abstract Syntax Notation One (ASN.1): Information object specification".
[10]
TS 38.331: "NR; Radio Resource Control (RRC); Protocol Specificaiton".
[11]
TS 23.401: "General Packet Radio Service (GPRS) Enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access".
[12]
TS 23.203: "Policy and Charging Control Architecture".
[13]
TS 33.501: "Security Architecture and Procedures for 5G System".
[14]
RFC 5905: "Network Time Protocol Version 4: Protocol and Algorithms Specification".
[15]
TS 29.281: "General Packet Radio System (GPRS) Tunnelling Protocol User Plane (GTPv1-U)".
[16]
TS 38.414: "NG-RAN; NG Data Transport".
[17]
TS 38.323: "NR; Packet Data Convergence Protocol (PDCP) specification".
[18]
TS 37.482: "E1 Signalling Transport".
[19]
TS 37.340: "NR; Multi-connectivity; Overall description; Stage-2".
[20]
TS 23.501: "System Architecture for the 5G System".
[21]
TS 36.331: "Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC) protocol specification".
[22]
TS 28.552: "Management and orchestration; 5G performance measurements".
[23]
TS 23.003: "Numbering, addressing and identification".
[24]
TS 32.422: "Trace control and configuration management".
[25]
TS 36.300: "Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2".
[26]
TS 32.425: "Performance measurements; Evolved Universal Terrestrial Radio Access Network (E-UTRAN)".
[27]
TS 37.320: "Universal Terrestrial Radio Access (UTRA) and Evolved Universal Terrestrial Radio Access (E-UTRA); Radio measurement collection for Minimization of Drive Tests (MDT);Overall description; Stage 2".
[28]
TS 38.474: "NG-RAN; F1 data transport".
[29]
TS 29.244: "Interface between the Control Plane and the User Plane Nodes; Stage 3".
[30]
TS 37.470: "W1 interface; General aspects and principles".
[31]
TS 36.401: "Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Architecture description".
[32]
TS 33.401: "3GPP System Architecture Evolution (SAE); Security architecture".
[33]
TS 36.331: "Radio Resource Control (RRC); Protocol specification".
[34]
TS 36.323: "Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Packet Data Convergence Protocol (PDCP) specification".
3 Definitions and abbreviations p. 13
3.1 Definitions p. 13
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.
Elementary Procedure:
E1AP consists of Elementary Procedures (EPs). An Elementary Procedure is a unit of interaction between gNB-CU-CP and gNB-CU-UP, or between eNB-CP and eNB-UP, or between ng-eNB-CU-CP and ng-eNB-CU-UP. These Elementary Procedures are defined separately and are intended to be used to build up complete sequences in a flexible manner. If the independence between some EPs is restricted, it is described under the relevant EP description. Unless otherwise stated by the restrictions, the EPs may be invoked independently of each other as standalone procedures, which can be active in parallel. The usage of several E1AP EPs together is specified in stage 2 specifications (e.g., TS 37.480).
An EP consists of an initiating message and possibly a response message. Two kinds of EPs are used:
Conditional handover:
- Class 1: Elementary Procedures with response (success and/or failure).
- Class 2: Elementary Procedures without response.
- A signalling message explicitly indicates that the elementary procedure successfully completed with the receipt of the response.
- A signalling message explicitly indicates that the EP failed.
- On time supervision expiry (i.e., absence of expected response).
- One signalling message reports both successful and unsuccessful outcome for the different included requests. The response message used is the one defined for successful outcome.
as defined in TS 38.300.
Conditional PSCell Change:
as defined in TS 37.340.
DAPS Handover:
as defined in TS 38.300.
eNB-CP:
as defined in TS 36.401.
eNB-UP:
as defined in TS 36.401.
gNB:
as defined in TS 38.300.
gNB-CU:
as defined in TS 38.401.
gNB-DU:
as defined in TS 38.401.
gNB-CU-CP:
as defined in TS 38.401.
gNB-CU-UP:
as defined in TS 38.401.
MBS-associated signalling:
When E1AP messages associated to one MBS session uses the MBS-associated logical E1-connection for association of the message to the MBS session in gNB-CU-CP and gNB-CU-UP.
MBS-associated logical E1-connection:
The MBS-associated logical E1-connection uses the identities GNB-CU-CP MBS E1AP ID and GNB-CU-UP MBS E1AP ID according to the definition in TS 38.401. For a received MBS-associated E1AP message the gNB-CU-CP identifies the associated MBS session based on the GNB-CU-CP MBS E1AP ID IE and the gNB-CU-UP identifies the associated MBS session based on the GNB-CU-UP MBS E1AP ID IE.
MBS session resource:
as defined in TS 38.401.
Multicast F1-U Context:
as defined in TS 38.401.
ng-eNB-CU:
as defined in TS 37.470.
ng-eNB-CU-CP:
as defined in TS 38.401.
ng-eNB-CU-UP:
as defined in TS 38.401.
ng-eNB-DU:
as defined in TS 37.470.
PDU Session Resource:
as defined in TS 38.401.
UE-associated signalling:
When E1AP messages associated to one UE uses the UE-associated logical E1-connection for association of the message to the UE in gNB-CU-UP and gNB-CU-CP, or in eNB-CP and eNB-UP, or in ng-eNB-CU-CP and ng-eNB-CU-UP.
UE-associated logical E1-connection:
The UE-associated logical E1-connection uses the identities GNB-CU-CP UE E1AP ID and GNB-CU-UP UE E1AP ID according to the definition in TS 38.401. For a received UE associated E1AP message the gNB-CU-CP or eNB-CP or ng-eNB-CU-CP identifies the associated UE based on the GNB-CU-CP UE E1AP ID IE and the gNB-CU-UP or eNB-UP or ng-eNB-CU-UP identifies the associated UE based on the GNB-CU-UP UE E1AP ID IE.
Public Network Integrated NPN:
as defined in TS 23.501.
Stand-alone Non-Public Network:
as defined in TS 23.501.
3.2 Abbreviations p. 15
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.
5GC
5G Core Network
5QI
5G QoS Identifier
CAG
Closed Access Group
CGI
Cell Global Identifier
CHO
Conditional Handover
CN
Core Network
CP
Control Plane
CPA
Conditional PSCell Addition
CPC
Conditional PSCell Change
DAPS
Dual Active Protocol Stack
DL
Downlink
EHC
Ethernet Header Compression
EN-DC
E-UTRA-NR Dual Connectivity
EPC
Evolved Packet Core
IAB
Integrated Access and Backhaul
MBS
Multicast/Broadcast Service
MCG
Master Cell Group
NID
Network Identifier
NPN
Non-Public Network
PNI-NPN
Public Network Integrated Non-Public Network
PTP
Point to Point
PTM
Point to Multipoint
NSSAI
Network Slice Selection Assistance Information
RANAC
RAN Area Code
SCG
Secondary Cell Group
SDAP
Service Data Adaptation Protocol
SDT
Small Data Transmisson
SNPN
Stand-alone Non-Public Network
S-NSSAI
Single Network Slice Selection Assistance Information
TNLA
Transport Network Layer Association
UDC
Uplink Data Compression
4 General p. 15
4.1 Procedure specification principles p. 15
The principle for specifying the procedure logic is to specify the functional behaviour of the terminating node exactly and completely. Any rule that specifies the behaviour of the originating node shall be possible to be verified with information that is visible within the system.
The following specification principles have been applied for the procedure text in clause 8:
-
The procedure text discriminates between:
- Functionality which "shall" be executed. The procedure text indicates that the receiving node "shall" perform a certain function Y under a certain condition. If the receiving node supports procedure X but cannot perform functionality Y requested in the REQUEST message of a Class 1 EP, the receiving node shall respond with the message used to report unsuccessful outcome for this procedure, containing an appropriate cause value.
- Functionality which "shall, if supported" be executed. The procedure text indicates that the receiving node "shall, if supported," perform a certain function Y under a certain condition. If the receiving node supports procedure X, but does not support functionality Y, the receiving node shall proceed with the execution of the EP, possibly informing the requesting node about the not supported functionality.
- Any required inclusion of an optional IE in a response message is explicitly indicated in the procedure text. If the procedure text does not explicitly indicate that an optional IE shall be included in a response message, the optional IE shall not be included. For requirements on including Criticality Diagnostics IE, see clause 10.
4.2 Forwards and backwards compatibility p. 16
The forwards and backwards compatibility of the protocol is assured by mechanism where all current and future messages, and IEs or groups of related IEs, include ID and criticality fields that are coded in a standard format that will not be changed in the future. These parts can always be decoded regardless of the standard version.
4.3 Specification notations p. 16
For the purposes of the present document, the following notations apply:
Procedure
When referring to an elementary procedure in the specification the Procedure Name is written with the first letters in each word in upper case characters followed by the word "procedure", e.g. Handover Preparation procedure.
Message
When referring to a message in the specification the MESSAGE NAME is written with all letters in upper case characters followed by the word "message", e.g. HANDOVER REQUEST message.
IE
When referring to an information element (IE) in the specification the Information Element Name is written with the first letters in each word in upper case characters and all letters in Italic font followed by the abbreviation "IE", e.g. E-RAB ID IE.
Value of an IE
When referring to the value of an information element (IE) in the specification the "Value" is written as it is specified in the specification enclosed by quotation marks, e.g. "Value".
Value of an IE
When referring to the value of an information element (IE) in the specification the "Value" is written as it is specified in the specification enclosed by quotation marks, e.g. "Value".
5 E1AP services p. 16
E1AP provides the signalling service between the gNB-CU-CP and the gNB-CU-UP, or between the eNB-CP and the eNB-UP, or between the ng-eNB-CU-CP and the ng-eNB-CU-UP that is required to fulfil the E1AP functions described in clause 7. E1AP services are divided into three groups:
Non UE-associated services:
Unless explicitly indicated in the procedure specification, at any instance in time one protocol endpoint shall have a maximum of one ongoing E1AP procedure related to a certain UE.
Unless explicitly indicated in the procedure specification, at any instance in time one protocol endpoint shall have a maximum of one ongoing E1AP procedure related to a certain MBS session.
They are related to the whole E1 interface instance between the gNB-CU-CP and gNB-CU-UP, or between the eNB-CP and eNB-UP, or between the ng-eNB-CU-CP and ng-eNB-CU-UP utilising a non UE-associated signalling connection.
UE-associated services:
They are related to one UE. E1AP functions that provide these services are associated with a UE-associated signalling connection that is maintained for the UE in question.
MBS-associated services:
They are related to one MBS session. E1AP functions that provide these services are associated with an MBS-associated signalling connection that is maintained for the MBS session in question.
6 Services expected from signalling transport p. 17
The signalling connection shall provide in sequence delivery of E1AP messages. E1AP shall be notified if the signalling connection breaks.
7 Functions of E1AP p. 17
The functions of E1AP are described in TS 37.480.
