The source NG-RAN node initiates the procedure by sending the HANDOVER REQUEST message to the target NG-RAN node. When the source NG-RAN node sends the HANDOVER REQUEST message, it shall start the timer TXn
RELOCprep.
If the
Conditional Handover Information Request IE is contained in the HANDOVER REQUEST message, the target NG-RAN node shall consider that the request concerns a conditional handover and shall include the
Conditional Handover Information Acknowledge IE in the HANDOVER REQUEST ACKNOWLEDGE message.
If the
Target NG-RAN node UE XnAP ID IE is contained in the
Conditional Handover Information Request IE included in the HANDOVER REQUEST message, then the target NG-RAN node shall remove the existing prepared conditional HO identified by the
Target NG-RAN node UE XnAP ID IE and the
Target Cell Global ID IE. It is up to the implementation of the target NG-RAN node when to remove the HO information.
Upon reception of the HANDOVER REQUEST ACKNOWLEDGE message, the source NG-RAN node shall stop the timer TXn
RELOCprep and terminate the Handover Preparation procedure. If the procedure was initiated for an immediate handover, the source NG-RAN node shall start the timer TXn
RELOCoverall. The source NG-RAN node is then defined to have a Prepared Handover for that Xn UE-associated signalling.
For each
E-RAB ID IE included in the
QoS Flow To Be Setup List IE in the HANDOVER REQUEST message, the target NG-RAN node shall, if supported, store the content of the IE in the UE context and use it for subsequent inter-system handover.
If the
Masked IMEISV IE is contained in the HANDOVER REQUEST message the target NG-RAN node shall, if supported, use it to determine the characteristics of the UE for subsequent handling.
At reception of the HANDOVER REQUEST message the target NG-RAN node shall prepare the configuration of the AS security relation between the UE and the target NG-RAN node by using the information in the
UE Security Capabilities IE and the
AS Security Information IE in the
UE Context Information IE, as specified in
TS 33.501.
Upon reception of the
PDU Session Resource Setup List IE, contained in the HANDOVER REQUEST message, the target NG-RAN node shall behave the same as specified in
TS 38.413 for the PDU Session Resource Setup procedure. The target NG-RAN node shall report in the HANDOVER REQUEST ACKNOWLEDGE message the successful establishment of the result for all the requested PDU session resources. When the target NG-RAN node reports the unsuccessful establishment of a PDU session resource, the cause value should be precise enough to enable the source NG-RAN node to know the reason for the unsuccessful establishment.
For each PDU session if the
PDU Session Aggregate Maximum Bit Rate IE is included in the
PDU Session Resources To Be Setup List IE contained in the HANDOVER REQUEST message, the target NG-RAN node shall store the received PDU Session Aggregate Maximum Bit Rate in the UE context and use it when enforcing traffic policing for Non-GBR QoS flows for the concerned UE as specified in
TS 23.501.
For each QoS flow for which the source NG-RAN node proposes to perform forwarding of downlink data, the source NG-RAN node shall include the
DL Forwarding IE set to
"DL forwarding proposed" within the
Data Forwarding and Offloading Info from source NG-RAN node IE in the
PDU Session Resources To Be Setup List IE in the HANDOVER REQUEST message. The source NG-RAN node shall include the
DL Forwarding IE set to
"DL forwarding proposed" for all the QoS flows mapped to a DRB, if it requests a DAPS handover for that DRB.
For each PDU session for which the target NG-RAN node decides to admit the data forwarding for at least one QoS flow, the target NG-RAN node may include the
PDU Session level DL data forwarding UP TNL Information IE within the
Data Forwarding Info from target NG-RAN node IE in the
PDU Session Resource Admitted Info IE contained in the
PDU Session Resources Admitted List IE in the HANDOVER REQUEST ACKNOWLEDGE message.
For each QoS flow for which the source NG-RAN node has not yet received the SDAP end marker packet if QoS flow re-mapping happened before handover, the source NG-RAN node shall include the
UL Forwarding Proposal IE within the
Data Forwarding and Offloading Info from source NG-RAN node IE in the HANDOVER REQUEST message, and if the target NG-RAN node decides to admit uplink data forwarding for at least one QoS flow, the target NG-RAN node may include the
PDU Session Level UL Data Forwarding UP TNL Information IE in the
Data Forwarding Info from target NG-RAN node IE in the
PDU Session Resources Admitted Item IE contained in the
PDU Session Resources Admitted List IE in the HANDOVER REQUEST ACKNOWLEDGE message to indicate that it accepts the uplink data forwarding.
For each PDU session resource successfully setup at the target NG-RAN, the target NG-RAN node may allocate resources for additional Xn-U PDU session resource GTP-U tunnels, indicated in the
Secondary Data Forwarding Info from target NG-RAN node List IE.
For each PDU session in the HANDOVER REQUEST message, if the
Alternative QoS Parameters Set List IE is included in the
GBR QoS Flow Information IE in the
PDU Session Resources To Be Setup List IE, the target NG-RAN node may accept the setup of the involved QoS flow when notification control has been enabled if the requested QoS parameters set or at least one of the alternative QoS parameters sets can be fulfilled at the time of handover as specified in
TS 23.501. In case the target NG-RAN node accepts the handover fulfilling one of the alternative QoS parameters it shall indicate the alternative QoS parameters set which it can currently fulfil in the
Current QoS Parameters Set Index IE within the
PDU Session Resources Admitted List IE of the HANDOVER REQUEST ACKNOWLEDGE message while setting the QoS parameters towards the UE according to the requested QoS parameters set as specified in
TS 23.501.
For each DRB for which the source NG-RAN node proposes to perform forwarding of downlink data, the source NG-RAN node shall include the
DRB ID IE and the
mapped QoS Flows List IE within the
Source DRB to QoS Flow Mapping List IE contained in the
PDU Session Resources To Be Setup List IE in the HANDOVER REQUEST message. The source NG-RAN node may include the
QoS Flow Mapping Indication IE in the
Source DRB to QoS Flow Mapping List IE to indicate that only the uplink or downlink QoS flow is mapped to the DRB. If the target NG-RAN node decides to use the same DRB configuration and to map the same QoS flows as the source NG-RAN node, the target NG-RAN node includes the
DL Forwarding GTP Tunnel Endpoint IE within the
Data Forwarding Response DRB List IE in the HANDOVER REQUEST ACKNOWLEDGE message to indicate that it accepts the proposed forwarding of downlink data for this DRB.
The target NG-RAN node may additionally include the
Redundant DL Forwarding UP TNL Information IE if at least one of the QoS flow mapped to the DRB is eligible to the redundant transmission feature as indicated in the
Redundant QoS Flow Indicator IE within the
PDU Session Resource To Be Setup List IE received in the HANDOVER REQUEST message for the QoS flow.
If the HANDOVER REQUEST ACKNOWLEDGE message contains the
UL Forwarding UP TNL Information IE for a given DRB in the
Data Forwarding Response DRB List IE within
Data Forwarding Info from target NG-RAN node IE in the
PDU Session Resources Admitted List IE and the source NG-RAN node accepts the data forwarding proposed by the target NG-RAN node, the source NG-RAN node shall perform forwarding of uplink data for the DRB.
If the HANDOVER REQUEST includes PDU session resources for PDU sessions associated to S-NSSAIs not supported by target NG-RAN, the target NG-RAN node shall reject such PDU session resources. In this case, and if at least one
PDU Session Resource To Be Setup Item IE is admitted, the target NG-RAN node shall send the HANDOVER REQUEST ACKNOWLEDGE message including the
PDU Session Resources Not Admitted List IE listing corresponding PDU sessions rejected at the target NG-RAN.
If the
Mobility Restriction List IE is
-
contained in the HANDOVER REQUEST message, the target NG-RAN node shall
-
store the information received in the Mobility Restriction List IE in the UE context;
-
use this information to determine a target for the UE during subsequent mobility action for which the NG-RAN node provides information about the target of the mobility action towards the UE, except when one of the PDU sessions has a particular ARP value (TS 23.501) in which case the information shall not apply;
-
use this information to select a proper SCG during dual connectivity operation.
-
use this information to select proper RNA(s) for the UE when moving the UE to RRC_INACTIVE.
-
not contained in the HANDOVER REQUEST message, the target NG-RAN node shall
-
consider that no roaming and no access restriction apply to the UE except for the PNI-NPN mobility as described in TS 23.501.
The target NG-RAN node shall consider that roaming or access to CAG cells is only allowed if the
Allowed PNI-NPN ID List IE is contained in the HANDOVER REQUEST message, as described in
TS 23.501.
If the
Trace Activation IE is included in the HANDOVER REQUEST message the target NG-RAN node shall, if supported, initiate the requested trace function as specified in
TS 32.422.
If the
Index to RAT/Frequency Selection Priority IE is contained in the HANDOVER REQUEST message, the target NG-RAN node shall store this information and use it as defined in
TS 23.501.
If the UE Context Reference at the
S-NG-RAN IE is contained in the HANDOVER REQUEST message the target NG-RAN node may use it as specified in
TS 37.340. In this case, the source NG-RAN node may expect the target NG-RAN node to include the
UE Context Kept Indicator IE set to
"True" in the HANDOVER REQUEST ACKNOWLEDGE message, which shall use this information as specified in
TS 37.340.
For each PDU session, if the
Network Instance IE is included in the
PDU Session Resource To Be Setup List IE and the
Common Network Instance IE is not present, the target NG-RAN node shall, if supported, use it when selecting transport network resource as specified in
TS 23.501.
Redundant transmission:
-
For each PDU session, if the Redundant UL NG-U UP TNL Information at UPF IE is included in the PDU Session Resource To Be Setup List IE, the target NG-RAN node shall, if supported, use it as the uplink termination point for the user plane data for the redundant transmission for the concerned PDU session.
-
For each PDU session, if the Additional Redundant UL NG-U UP TNL Information at UPF List IE is included in the PDU Session Resource To Be Setup List IE, the target NG-RAN node shall, if supported, use them as the uplink termination points for the user plane data for the redundant transmission for the concerned PDU session.
-
For each PDU session, if the Redundant Common Network Instance IE is included in the PDU Session Resource To Be Setup List IE, the target NG-RAN node shall, if supported, use it when selecting transport network resource for the redundant transmission as specified in TS 23.501.
-
For each PDU session, if the Redundant PDU Session Information IE is included in the PDU Session Resource To Be Setup List IE contained in the HANDOVER REQUEST message, the target NG-RAN node shall, if supported, store the received information in the UE context and set up the redundant user plane for the concerned PDU session, as specified in TS 23.501. If the PDU Session Pair ID IE is included in the Redundant PDU Session Information IE, the target NG-RAN node may store and use it to identify the paired PDU sessions.
If the
TSC Traffic Characteristics IE is included in the QoS Flows To Be Setup List in the
PDU Session Resource To Be Setup List IE, the target NG-RAN node shall, if supported, use it as specified in
TS 23.501.
For each PDU session, if the
Common Network Instance IE is included in the
PDU Session Resource To Be Setup List IE or in the
Additional UL NG-U UP TNL Information at UPF List IE, or in the
Additional Redundant UL NG-U UP TNL Information at UPF List IE, the target NG-RAN node shall, if supported, use it when selecting transport network resource for the concerned NG-U transport bearer as specified in
TS 23.501.
For each PDU session for which the
Security Indication IE is included in the
PDU Session Resource To Be Setup List IE and the
Integrity Protection Indication IE or
Confidentiality Protection Indication IE is set to
"required", the target NG-RAN node shall perform user plane integrity protection or ciphering, respectively. If the NG-RAN node is not able to perform the user plane integrity protection or ciphering, it shall reject the setup of the PDU Session Resources with an appropriate cause value.
If the NG-RAN node is an ng-eNB, it shall reject all PDU sessions for which the
Integrity Protection Indication IE is set to
"required".
For each PDU session for which the
Security Indication IE is included in the
PDU Session Resource To Be Setup List IE and the
Integrity Protection Indication IE or the
Confidentiality Protection Indication IE is set to
"preferred", the target NG-RAN node should, if supported, perform user plane integrity protection or ciphering, respectively and shall notify the SMF whether it succeeded the user plane integrity protection or ciphering or not for the concerned security policy.
For each PDU session for which the
Maximum Integrity Protected Data Rate IE is included in the
Security Indication IE in the
PDU Session Resources To Be Setup List IE, the NG-RAN node shall store the respective information and, if integrity protection is to be performed for the PDU session, it shall enforce the traffic corresponding to the received
Maximum Integrity Protected Data Rate IE, for the concerned PDU session and concerned UE, as specified in
TS 23.501.
For each PDU session for which the
Security Indication IE is included in the
PDU Session Resource To Be Setup List IE and the
Integrity Protection Indication IE or
Confidentiality Protection Indication IE is set to
"not needed", the target NG-RAN node shall not perform user plane integrity protection or ciphering, respectively, for the concerned PDU session.
For each PDU session, if the
Additional UL NG-U UP TNL Information List IE is included in the
PDU Session Resources To Be Setup List IE contained in the HANDOVER REQUEST message, the target NG-RAN node may forward the UP transport layer information to the target S-NG-RAN node as the uplink termination point for the user plane data for this PDU session split in different tunnel.
If the
Location Reporting Information IE is included in the HANDOVER REQUEST message, then the target NG-RAN node should initiate the requested location reporting functionality as defined in
TS 38.413.
Upon reception of
UE History Information IE in the HANDOVER REQUEST message, the target NG-RAN node shall collect the information defined as mandatory in the
UE History Information IE and shall, if supported, collect the information defined as optional in the
UE History Information IE, for as long as the UE stays in one of its cells, and store the collected information to be used for future handover preparations.
If the
Trace Activation IE is included in the HANDOVER REQUEST message which includes
-
the MDT Activation IE set to "Immediate MDT and Trace", then the target NG-RAN node shall if supported, initiate the requested trace session and MDT session as described in TS 32.422.
-
the MDT Activation IE set to "Immediate MDT Only" or "Logged MDT only", the target NG-RAN node shall, if supported, initiate the requested MDT session as described in TS 32.422 and the target NG-RAN node shall ignore the Interfaces To Trace IE, and the Trace Depth IE.
-
the MDT Location Information IE, within the MDT Configuration IE, the target NG-RAN node shall, if supported, store this information and take it into account in the requested MDT session.
-
the MDT Activation IE set to "Immediate MDT Only" or "Logged MDT only", and if the Signalling based MDT PLMN List IE is included in the MDT Configuration IE, the target NG-RAN node may use it to propagate the MDT Configuration as described in TS 37.320.
-
the Bluetooth Measurement Configuration IE, within the MDT Configuration IE, the target NG-RAN node shall, if supported, take it into account for MDT Configuration as described in TS 37.320.
-
the WLAN Measurement Configuration IE, within the MDT Configuration IE, the target NG-RAN node shall, if supported, take it into account for MDT Configuration as described in TS 37.320.
-
the Sensor Measurement Configuration IE, within the MDT Configuration IE, the target NG-RAN node shall take it into account for MDT Configuration as described in TS 37.320.
-
the MDT Configuration IE and if the target NG-RAN node is a gNB receiving a MDT Configuration-EUTRA IE, or the target NG-RAN node is a ng-eNB receiving a MDT Configuration-NR IE, the target NG-RAN node shall store it as part of the UE context, and use it as described in TS 37.320.
If the
Management Based MDT PLMN List IE is contained in the HANDOVER REQUEST message, the target NG-RAN node shall, if supported, store the received information in the UE context, and use this information to allow subsequent selection of the UE for management based MDT defined in
TS 32.422.
If the HANDOVER REQUEST message includes the
Management Based MDT PLMN List IE, the target NG-RAN node shall, if supported, store it in the UE context, and take it into account if it includes information regarding the PLMN serving the UE in the target NG-RAN node.
If the
Mobility Information IE is provided in the HANDOVER REQUEST message, the target NG-RAN node shall, if supported, store this information. The target NG-RAN shall, if supported, store the C-RNTI assigned at the source cell as received in the HANDOVER REQUEST message.
Upon reception of the UE History Information from the
UE IE in the HANDOVER REQUEST message, the target NG-RAN node shall, if supported, store the collected information and use it for future handover preparations.
For each QoS flow which has been successfully established in the target NG-RAN node, if the
QoS Monitoring Request IE was included in the
QoS Flow Level QoS Parameters IE contained in the HANDOVER REQUEST message, the target NG-RAN node shall store this information, and shall, if supported, perform delay measurement and QoS monitoring, as specified in
TS 23.501. If the
QoS Monitoring Reporting Frequency IE was included in the
QoS Flow Level QoS Parameters IE contained in the HANDOVER REQUEST message, the target NG-RAN node shall store this information, and shall, if supported, use it for RAN part delay reporting.
If the
5GC Mobility Restriction List Container IE is included in the HANDOVER REQUEST message, the target NG-RAN node shall, if supported, store this information in the UE context and use it as specified in
TS 38.300.
V2X:
-
If the NR V2X Services Authorized IE is included in the HANDOVER REQUEST message and it contains one or more IEs set to "authorized", the target NG-RAN node shall, if supported, consider that the UE is authorized for the relevant service(s).
-
If the LTE V2X Services Authorized IE is included in the HANDOVER REQUEST message and it contains one or more IEs set to "authorized", the target NG-RAN node shall, if supported, consider that the UE is authorized for the relevant service(s).
-
If the NR UE Sidelink Aggregate Maximum Bit Rate IE is included in the HANDOVER REQUEST message, the target NG-RAN node shall, if supported, use the received value for the concerned UE's sidelink communication in network scheduled mode for NR V2X services.
-
If the LTE UE Sidelink Aggregate Maximum Bit Rate IE is included in the HANDOVER REQUEST message, the target NG-RAN node shall, if supported, use the received value for the concerned UE's sidelink communication in network scheduled mode for LTE V2X services.
5G ProSe:
-
If the 5G ProSe Authorized IE is included in the HANDOVER REQUEST message and it contains one or more IEs set to "authorized", the target NG-RAN node shall, if supported, consider that the UE is authorized for the relevant service(s).
-
If the 5G ProSe UE PC5 Aggregate Maximum Bit Rate IE is included in the HANDOVER REQUEST message, the target NG-RAN node shall, if supported, use the received value for the concerned UE's sidelink communication in network scheduled mode for 5G ProSe services.
-
If the 5G ProSe PC5 QoS Parameters IE is included in the HANDOVER REQUEST message, the target NG-RAN node shall, if supported, use it as defined in TS 23.304.
If the
PC5 QoS Parameters IE is included in the HANDOVER REQUEST message, the target NG-RAN node shall, if supported, use it as defined in
TS 23.287.
If the
DAPS Request Information IE is included for a given DRB in the HANDOVER REQUEST message, the target NG-RAN node shall consider that the request concerns a DAPS handover for that DRB, as described in
TS 38.300. Accordingly, the target NG-RAN node shall include the
DAPS Response Information IE in the HANDOVER REQUEST ACKNOWLEDGE message.
If the
Maximum Number of CHO Preparations IE is included in the
Conditional Handover Information Acknowledge IE contained in the HANDOVER REQUEST ACKNOWLEDGE message, then the source NG-RAN node should not prepare more candidate target cells for a CHO for the same UE towards the target NG-RAN node than the number indicated in the IE.
If the
Estimated Arrival Probability IE is contained in the
Conditional Handover Information Request IE included in the HANDOVER REQUEST message, then the target NG-RAN node may use the information to allocate necessary resources for the incoming CHO.
If the
IAB Node Indication IE is contained in the HANDOVER REQUEST message, the target NG-RAN node shall, if supported, consider that the handover is for an IAB node. In addition:
-
If the No PDU Session Indication IE is contained in the HANDOVER REQUEST message, the target NG-RAN node shall, if supported, consider the UE as an IAB-node which does not have any PDU sessions activated, and ignore the PDU Session Resources To Be Setup List IE, and shall not take any action with respect to PDU session setup. Subsequently, the source NG-RAN node shall, if supported, ignore the PDU Session Resources Admitted To Be Added List IE in the HANDOVER REQUEST ACKNOWLEDGE message.
If the
UE Radio Capability ID IE is contained in the HANDOVER REQUEST message, the target NG-RAN node shall, if supported, store this information in the UE context and use it as defined in
TS 23.501 and
TS 23.502.
If for a given QoS Flow the
Source DL Forwarding IP Address IE is included within the
Data Forwarding and Offloading Info from source NG-RAN node IE in the
PDU Session Resources To Be Setup List IE contained in the HANDOVER REQUEST message, the target NG-RAN node shall, if supported, store this information and use it as part of its ACL functionality configuration actions, if such ACL functionality is deployed.
If the
MBS Session Information List IE is contained in the HANDOVER REQUEST message, the target NG-RAN node shall, if supported, establish an NG-RAN MBS session resources context as specified in
TS 23.247 and
TS 38.300, if applicable.
If the HANDOVER REQUEST message includes the
MBS Area Session ID IE, the target NG-RAN, if supported, shall use this information as an indication from which MBS Area Session ID the UE is handed over. For each MBS session for which the
Active MBS Session Information IE is included in the
MBS Session Information Item List IE, the target NG-RAN shall, if supported, use this information to setup respective MBS session resources. The target NG-RAN node shall, if supported, consider that the MBS sessions for which the
Active MBS Session Information IE is not included are inactive.
If the HANDOVER REQUEST ACKNOWLEDGE message contains in the
MBS Session Information Response List IE the
MBS Data Forwarding Response Info IE that the source NG-RAN node shall use the information for forwarding MBS traffic to the target NG-RAN node.
If the
MBS Session Associated Information List IE is included in the
PDU Session Resources To Be Setup List IE in the HANDOVER REQUEST message, the target NG-RAN node shall, if supported, use the information contained in the
Associated QoS Flows Information List IE as specified in
TS 23.247.
For each MRB indicated in the
MBS Mapping and Data Forwarding Request Info from source NG-RAN node IE, the target NG-RAN node shall use the
MRB ID IE and, if included, the
MRB Progress Information IE which includes the highest PDCP SN of the packet which has already been delivered to the UE for the MRB, to decide whether to apply data forwarding for that MRB and to establish respective resources.
The source NG-RAN shall, for each MRB in the
MBS Data Forwarding Response Info from target NG-RAN node IE in the HANDOVER REQUEST ACKNOWLEDGE message, start data forwarding to the indicated DL Forwarding UP TNL Information. If the
MRB Progress Information IE is included the source NG-RAN node may use the information to determine when to stop data forwarding.
If the
Time Synchronisation Assistance Information IE is contained in the HANDOVER REQUEST message, the target NG-RAN node shall, if supported, store this information in the UE context and use it as defined in
TS 23.501.
If the
QMC Configuration Information IE is contained in the HANDOVER REQUEST message, the target NG-RAN node shall, if supported, take it into account for QoE measurements handling, as described in
TS 38.300.
If the
UE Slice-Maximum Bit Rate List IE is contained in HANDOVER REQUEST message, the target NG-RAN node shall, if supported, store the received UE Slice Maximum Bit Rate List in the UE context, and use the received UE Slice Maximum Bit Rate value for each S-NSSAI for the concerned UE as specified in
TS 23.501.
Interaction with SN Status Transfer procedure:
If the
UE Context Kept Indicator IE set to
"True" and the
DRBs transferred to MN IE are included in the HANDOVER REQUEST ACKNOWLEDGE message, the source NG-RAN node shall, if supported, include the uplink/downlink PDCP SN and HFN status received from the S-NG-RAN node in the SN Status Transfer procedure towards the target NG-RAN node, as specified in
TS 37.340.