5G(NR)-F1 Setup Procedure

 

F1 Setup

3GPP TS: 38.473

The purpose of the F1 Setup procedure is to exchange application level data needed for the gNB-DU and the gNB-CU to correctly interoperate on the F1 interface. This procedure shall be the first F1AP procedure triggered after a TNL association has become operational. The procedure uses non-UE associated signalling, it is cell related procedure.

This procedure erases any existing application level configuration data in the two nodes and replaces it by the one received. This procedure also re-initialises the F1AP UE-related contexts (if any) and erases all related signalling connections in the two nodes like a Reset procedure would do.

Successful Operation

The gNB-DU initiates the procedure by sending a F1 SETUP REQUEST message including the appropriate data to the gNB-CU. The gNB-CU responds with a F1 SETUP RESPONSE message including the appropriate data.

If the F1 SETUP REQUEST message contains the gNB-DU Name IE the gNB-CU may use this IE as a human readable name of the gNB-DU.

For NG-RAN, the gNB-DU shall include the gNB-DU System Information IE and the TAI Slice Support List IE.

The gNB-CU may include the Cells to be Activated List IE in the F1 SETUP RESPONSE message. The Cells to be Activated List IE includes a list of cells that the gNB-CU requests the gNB-DU to activate. The gNB-DU shall activate the cells included in the Cells to be Activated List IE and reconfigure the physical cell identity for cells for which the NR PCI IE is included.

For NG-RAN, the gNB-CU shall include the gNB-CU System Information IE in the F1 SETUP RESPONSE message.

The exchanged data shall be stored in respective node and used as long as there is an operational TNL association. When this procedure is finished, the F1 interface is operational and other F1 messages may be exchanged.

For NG-RAN, the gNB-DU may include the RAN Area Code IE in the F1 SETUP REQUEST message. The gNB-CU may use it according to TS 38.300 [6].

F1 SETUP REQUEST IEs.

This message is sent by the gNB-DU to transfer information for a TNL association.

Direction: gNB-DU ® gNB-CU

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Message Type	M		9.3.1.1		YES	reject
Transaction ID	M		9.3.1.23		YES	reject
gNB-DU ID	M		9.3.1.9		YES	reject
gNB-DU Name	O		PrintableString(SIZE(1..150,…))		YES	ignore
gNB-DU Served Cells List		1		List of cells configured in the gNB-DU	YES	reject
>gNB-DU Served Cells Item		1.. <maxCellingNBDU>			EACH	reject
>>Served Cell Information	M		9.3.1.10	Information about the cells configured in the gNB-DU	-	-
>>gNB-DU System Information	O		9.3.1.18	RRC container with system information owned by gNB-DU	-	-

 

Range bound	Explanation
maxCellingNBDU	Maximum no. cells that can be served by a gNB-DU. Value is 512.

 

9.3.1.1    Message Type

The Message Type IE uniquely identifies the message being sent. It is mandatory for all messages.

IE/Group Name	Presence	Range	IE type and reference	Semantics description
Message Type
>Procedure Code	M		INTEGER (0..255)
>Type of Message	M		CHOICE (Initiating Message, Successful Outcome, Unsuccessful Outcome, …)

 Procedure Code: every message has its procedure code, so that, that can be identified their class and message type by other nodes. 

Type of Message: The Type can be Initiating Message, Successful Outcome, Unsuccessful Outcome. it is selected by sending node.

9.3.1.23  Transaction ID

The Transaction ID IE uniquely identifies a procedure among all ongoing parallel procedures of the same type initiated by the same protocol peer. Messages belonging to the same procedure shall use the same Transaction ID. The Transaction ID is determined by the initiating peer of a procedure.

IE/Group Name	Presence	Range	IE type and reference	Semantics description
Transaction ID	M		INTEGER (0..255, …)

 

9.3.1.9    gNB-DU ID

The gNB-DU ID uniquely identifies the gNB-DU at least within a gNB-CU.

IE/Group Name	Presence	Range	IE type and reference	Semantics description
gNB-DU ID	M		INTEGER (0 .. 236-1)	The gNB-DU ID is independently configured from cell identifiers, i.e. no connection between gNB-DU ID and cell identifiers.

9.3.1.10 Served Cell Information

This IE contains cell configuration information of a cell in the gNB-DU.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
NR CGI	M		9.3.1.12		-	-
NR PCI	M		INTEGER (0..1007)	Physical Cell ID
5GS TAC	M		9.3.1.29	5GS Tracking Area Code	YES	reject
Configured EPS TAC	O		9.3.1.29a		–
Served PLMNs		1..<maxnoofBPLMNs>		Broadcast PLMNs	–	–
>PLMN Identity	M		9.3.1.14		-	-
>TAI Slice Support List	O		Slice Support List 9.3.1.37	Supported S-NSSAIs per TA.	YES	ignore
CHOICE NR-Mode-Info	M				–	–
>FDD
>>FDD Info		1			-	-
>>>UL FreqInfo	M		NR Frequency Info 9.3.1.17		–	–
>>>DL FreqInfo	M		NR Frequency Info 9.3.1.17		–	–
>>>UL Transmission Bandwidth	M		NR Transmission Bandwidth 9.3.1.15		–	–
>>>DL Transmission Bandwidth	M		NR Transmission Bandwidth 9.3.1.15		–	–
>TDD					-	-
>>TDD Info		1			-	-
>>> NR FreqInfo	M		NR Frequency Info 9.3.1.17		–	–
>>> Transmission Bandwidth	M		NR Transmission Bandwidth 9.3.1.15		–	–
Measurement Timing Configuration	M		OCTET STRING	Contains the MeasurementTimingConfiguration inter-node message defined in TS 38.331 [8].	–	–
RANAC	O		9.3.1.57	RAN Area Code	YES	ignore

 

Range bound	Explanation
maxnoofBPLMNs	Maximum no. of Broadcast PLMN Ids. Value is 6.

  

9.3.1.18          gNB-DU System Information

This IE contains the system information generated by the gNB-DU. here we have two mandatory parameters, you could further reach to 38.331 for details.

IE/Group Name	Presence	Range	IE type and reference	Semantics description
MIB message	M		OCTET STRING	MIB message, as defined in TS 38.331 [8].
SIB1 message	M		OCTET STRING	SIB1 message, as defined in TS 38.331 [8].