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Content for  TS 38.473  Word version:  18.5.0

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1…   8…   9… 
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 F1AP services  6 Services expected from signalling transport  7 Functions of F1AP 
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1  Scope  p. 21

The present document specifies the 5G radio network layer signalling protocol for the F1 interface. The F1 interface provides means for interconnecting a gNB-CU and a gNB-DU of a gNB within an NG-RAN, or for interconnecting a gNB-CU and a gNB-DU of an en-gNB within an E-UTRAN. The F1 Application Protocol (F1AP) supports the functions of F1 interface by signalling procedures defined in the present document. F1AP is developed in accordance to the general principles stated in TS 38.401 and TS 38.470.
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2  References  p. 21

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 38.470: "NG-RAN; F1 general aspects and principles".
[3]
TS 38.413: "NG-RAN; NG Application Protocol (NGAP)".
[4]
TS 38.401: "NG-RAN; Architecture Description".
[5]
ITU-T Recommendation X.691 (2002-07): "Information technology - ASN.1 encoding rules - Specification of Packed Encoding Rules (PER)".
[6]
TS 38.300: "NR; Overall description; Stage-2".
[7]
TS 37.340: "NR; Multi-connectivity; Overall description; Stage-2".
[8]
TS 38.331: "NR; Radio Resource Control (RRC); Protocol specification".
[9]
TS 36.423: "Evolved Universal Terrestrial Radio Access Network (E-UTRAN); X2 Application Protocol (X2AP)".
[10]
TS 23.401: "General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access".
[11]
TS 23.203: "Policy and charging control architecture".
[12]
ITU-T Recommendation X.680 (07/2002): "Information technology - Abstract Syntax Notation One (ASN.1): Specification of basic notation".
[13]
ITU-T Recommendation X.681 (07/2002): "Information technology - Abstract Syntax Notation One (ASN.1): Information object specification".
[14]
TR 25.921: (version.7.0.0): "Guidelines and principles for protocol description and error".
[15]
TS 36.413: "Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 Application Protocol (S1AP)".
[16]
TS 38.321: "NR; Medium Access Control (MAC) protocol specification".
[17]
TS 38.104: "NR; Base Station (BS) radio transmission and reception".
[18]
TS 29.281: "General Packet Radio System (GPRS); Tunnelling Protocol User Plane (GTPv1-U) ".
[19]
TS 38.414: "NG-RAN; NG data transport".
[20]
TS 36.300: "Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2".
[21]
TS 23.501: "System Architecture for the 5G System".
[22]
TS 38.472: "NG-RAN; F1 signalling transport".
[23]
TS 23.003: "Numbering, addressing and identification".
[24]
TS 38.304: "NR; User Equipment (UE) procedures in Idle mode and RRC Inactive state ".
[25]
TS 36.104: "Base Station (BS) radio transmission and reception".
[26]
TS 38.101-1: "NR; User Equipment (UE) radio transmission and reception; Part 1: Range 1 Standalone".
[27]
TS 36.211: "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channels and modulation".
[28]
TS 38.423: "NG-RAN; Xn application protocol (XnAP)".
[29]
TS 32.422: "Trace control and configuration management".
[30]
TS 38.340: "NR; Backhaul Adaptation Protocol (BAP) specification".
[31]
TS 38.213: "NR; Physical layer procedures for control".
[32]
TS 38.314: "NR; Layer 2 measurements".
[33]
TS 38.211: "NR; Physical channels and modulation".
[34]
TS 38.214: "NR; Physical layer procedures for data".
[35]
TS 37.320: "Radio measurement collection for Minimization of Drive Tests (MDT)".
[36]
TS 23.032: "Technical Specification Group Services and System Aspects; Universal Geographical Area Description (GAD)".
[37]
TS 38.455: "NG-RAN; NR Positioning protocol A (NRPPa)".
[38]
TS 38.133: "NR; Requirements for support of radio resource management".
[39]
TS 37.355: "LTE Positioning Protocol (LPP)".
[40]
TS 23.287: "Architecture enhancements for 5G System (5GS) to support Vehicle-to-Everything (V2X) services".
[41]
TS 36.331: "Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification".
[42]
TS 38.305: "NG Radio Access Network (NG-RAN); Stage 2 functional specification of User Equipment (UE) positioning in NG-RAN".
[43]
TS 38.215: "NR; Physical layer (PHY); Measurements".
[44]
TS 23.304: "Proximity based Services (ProSe) in the 5G System (5GS)".
[45]  Void
[46]
TS 37.213: "NR; Physical layer procedures for shared spectrum channel access".
[47]
TS 37.483: "E1 Application Protocol (E1AP)".
[48]
IEEE Std 1588: "IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems", Edition 2019.
[49]
TS 23.273: "5G System (5GS) Location Services (LCS); Stage 2".
[50]
TS 29.571: "5G System; Common Data Types for Service Based Interfaces; Stage 3".
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3  Definitions and abbreviations  p. 23

3.1  Definitions  p. 23

elementary procedure:
F1AP consists of Elementary Procedures (EPs). An Elementary Procedure is a unit of interaction between gNB-CU and gNB-DU. 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 F1AP EPs together is specified in stage 2 specifications (e.g., TS 38.470).
An EP consists of an initiating message and possibly a response message. Two kinds of EPs are used:
  • Class 1: Elementary Procedures with response (success and/or failure).
  • Class 2: Elementary Procedures without response.
For Class 1 EPs, the types of responses can be as follows:
Successful:
  • A signalling message explicitly indicates that the elementary procedure successfully completed with the receipt of the response.
Unsuccessful:
  • A signalling message explicitly indicates that the EP failed.
  • On time supervision expiry (i.e., absence of expected response).
Successful and Unsuccessful:
  • 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.
Class 2 EPs are considered always successful.
BH RLC channel:
as defined in TS 38.300.
CG-SDT-CS-RNTI:
as defined in TS 38.300.
Complete candidate configuration:
one type of a candidate configuration as defined in TS 38.331.
Conditional handover:
as defined in TS 38.300.
Conditional PSCell Addition:
as defined in TS 37.340.
Conditional PSCell Change:
as defined in TS 37.340.
DAPS Handover:
as defined in TS 38.300.
EN-DC operation:
Used in this specification when the F1AP is applied for gNB-CU and gNB-DU in E-UTRAN.
F1-terminating IAB-donor:
as defined in TS 38.401.
gNB:
as defined in TS 38.300.
gNB-CU:
as defined in TS 38.401.
gNB-CU UE F1AP ID:
as defined in TS 38.401.
gNB-DU:
as defined in TS 38.401.
gNB-DU UE F1AP ID:
as defined in TS 38.401.
en-gNB:
as defined in TS 37.340.
IAB-DU:
as defined in TS 38.300.
IAB-MT:
as defined in TS 38.300.
IAB-donor:
as defined in TS 38.300.
IAB-donor-CU:
as defined in TS 38.401.
IAB-donor-DU:
as defined in TS 38.401.
IAB-node:
as defined in TS 38.300.
MBS-associated signalling:
When F1AP messages associated to one MBS session uses the MBS-associated logical F1-connection for association of the message to the MBS session in gNB-DU and gNB-CU.
MBS-associated logical F1-connection:
The MBS-associated logical F1-connection uses the identities GNB-CU MBS F1AP ID and GNB-DU MBS F1AP ID according to the definition in TS 38.401. For a received MBS-associated F1AP message the gNB-CU identifies the associated MBS session based on the GNB-CU MBS F1AP ID IE and the gNB-DU identifies the associated MBS session based on the GNB-DU MBS F1AP ID IE.
MBS Session context in a gNB-DU:
as defined in TS 38.401.
MBS session resource:
as defined in TS 38.401.
Mobile IAB-DU:
as defined in TS 38.300.
Mobile IAB-MT:
as defined in TS 38.300.
Mobile IAB-node:
as defined in TS 38.300.
MP Relay UE:
as defined in TS 38.300.
MP Remote UE:
as defined in TS 38.300.
Multi-path:
as defined in TS 38.300.
Multicast F1-U Context:
as defined in TS 38.401.
Other SI:
as defined in TS 38.300.
PC5 Relay RLC channel:
as defined in TS 38.300.
Public network integrated NPN:
as defined in TS 23.501.
RRC-terminating IAB-donor:
as defined in TS 38.401.
SRAP:
Sidelink relay adaptation protocol, as defined in TS 38.300.
Stand-alone Non-Public Network:
as defined in TS 23.501.
UE-associated logical F1-connection:
The UE-associated logical F1-connection uses the identities GNB-CU UE F1AP ID and GNB-DU UE F1AP ID according to the definition in TS 38.401. For a received UE associated F1AP message the gNB-CU identifies the associated UE based on the GNB-CU UE F1AP ID IE and the gNB-DU identifies the associated UE based on the GNB-DU UE F1AP ID IE. The UE-associated logical F1-connection may exist before the F1 UE context is setup in gNB-DU.
UE-associated signalling:
When F1AP messages associated to one UE uses the UE-associated logical F1-connection for association of the message to the UE in gNB-DU and gNB-CU.
U2N Relay UE:
a UE that provides functionality to support connectivity to the network for U2N Remote UE(s).
U2N Remote UE:
a UE that communicates with the network via a U2N Relay UE.
U2U Relay UE:
as defined in TS 38.300.
U2U Remote UE:
as defined in TS 38.300.
Uu Relay RLC channel:
as defined in TS 38.300.
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3.2  Abbreviations  p. 25

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
A2X
Aircraft-to-Everything
AMF
Access and Mobility Management Function
ARP
Antenna Reference Point
ARPI
Additional RRM Policy Index
BH
Backhaul
CAG
Closed Access Group
CG
Cell Group
CG-SDT
Configured Grant-Small Data Transmission
CGI
Cell Global Identifier
CHO
Conditional Handover
CN
Core Network
CP
Control Plane
CPA
Conditional PSCell Addition
CPAC
Conditional PSCell Addition or Change
CPC
Conditional PSCell Change
DAPS
Dual Active Protocol Stack
DL
Downlink
DL-PRS
Downlink Positioning Reference Signal
EN-DC
E-UTRA-NR Dual Connectivity
EPC
Evolved Packet Core
eRedCap
Enhanced Reduced Capability
FSA ID
MBS Frequency Selection Area (FSA) ID
GPSI
Generic Public Subscription Identifier
IAB
Integrated Access and Backhaul
IMEISV
International Mobile station Equipment Identity and Software Version number
LMF
Location Management Function
LTM
L1/L2 Triggered Mobility
MBS
Multicast/Broadcast Service
MP
Multi-path
MT-SDT
Mobile Terminated Small Data Transmission
N3C
Non-3GPP Connection
NID
Network Identifier
NPN
Non-Public Network
NSAG
Network Slice AS Group
NSSAI
Network Slice Selection Assistance Information
PDC
Propagation Delay Compensation
PEIPS
Paging Early Indication with Paging Subgrouping
PNI-NPN
Public Network Integrated NPN
posSIB
Positioning SIB
PSI
PDU Set Importance
PTM
Point to Multipoint
PTP
Point to Point
QMC
QoE Measurement Collection
QoE
Quality of Experience
RANAC
RAN Area Code
RedCap
Reduced Capability
RIM
Remote Interference Management
RIM-RS
RIM Reference Signal
RRC
Radio Resource Control
RSPP
Ranging/Sidelink Positioning Protocol
RSRP
Reference Signal Received Power
S-CPAC
Subsequent Conditional PSCell Addition or Change
S-NSSAI
Single Network Slice Selection Assistance Information
SDT
Small Data Transmission
SNPN
Stand-alone Non-Public Network
SUL
Supplementary Uplink
TAC
Tracking Area Code
TAG
Timing Advance Group
TAI
Tracking Area Identity
TEG
Timing Error Group
TRP
Transmission-Reception Point
TSS
Timing Synchronisation Status
U2N
UE-to-Network
U2U
UE-to-UE
UL-AoA
Uplink Angle of Arrival
UL-RSCP
UL Reference Signal Carrier Phase
UL-RTOA
Uplink Relative Time of Arrival
UL-SRS
Uplink Sounding Reference Signal
V2X
Vehicle-to-Everything
Z-AoA
Zenith Angles of Arrival
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4  General  p. 26

4.1  Procedure specification principles  p. 26

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:
    1. 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.
    2. 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.
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4.2  Forwards and backwards compatibility  p. 27

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. 27

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".
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5  F1AP services  p. 27

F1AP provides the signalling service between gNB-DU and the gNB-CU that is required to fulfil the F1AP functions described in clause 7. F1AP services are divided into the following groups:
Non UE-associated services:
They are related to the whole F1 interface instance between the gNB-DU and gNB-CU utilising a non UE-associated signalling connection.
UE-associated services:
They are related to one UE. F1AP 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 service. F1AP functions that provide these services are associated with a MBS-associated signalling connection that is maintained for the MBS service in question.
Unless explicitly indicated in the procedure specification, at any instance in time one protocol endpoint shall have a maximum of one ongoing F1AP 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 F1AP procedure related to a certain MBS session.
All considerations of gNB-DU in this specification also apply to the IAB-DU and IAB-donor-DU, unless stated otherwise. All considerations of gNB-CU in this specification apply to the IAB-donor-CU as well, unless stated otherwise.
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6  Services expected from signalling transport  p. 27

The signalling connection shall provide in sequence delivery of F1AP messages. F1AP shall be notified if the signalling connection breaks.

7  Functions of F1AP  p. 28

The functions of F1AP are described in TS 38.470.

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