11 Special Procedures for RNC to RNC Communication

25.4133GPPRelease 17TSUTRAN Iu interface Radio Access Network Application Part (RANAP) signalling

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

11.1 General

This subclause specifies special procedures that are used for RNC to RNC communication, and that use other transport means than the RANAP procedures specified in clause 8.

11.2 RANAP Relocation Information

11.2.1 General

The purpose of the RANAP Relocation Information procedure is to handle the RANAP-related information that is carried transparently during relocation from a source RNC to a target RNC by RNSAP via the Iur Interface.

11.2.2 Operation

When during relocation it becomes necessary in the source RNC to generate RANAP information for transfer to the relocation target, the RNC shall form a RANAP RELOCATION INFORMATION message. The message shall be encoded according to the encoding rules specified for RANAP in the similar manner as for the normal RANAP messages. The outcome of the encoding will be an octet string, which shall not be sent to the CN via the Iu Interface, but shall be given to the appropriate local process for transparent transfer to the target RNC.

When the RANAP process in the target RNC receives an octet string containing a RANAP RELOCATION INFORMATION message that had been transparently transferred from the source RNC, it shall decode it according to the encoding rules specified for RANAP. This process is similar to receiving any normal RANAP message. The decoded information shall be passed to the appropriate processes in the RNC.

The RANAP RELOCATION INFORMATION message may contain the Direct Transfer Information List IE, the RAB Contexts List IE and the Source RNC PDCP context info IE. If present, the Direct Transfer Information List IE shall contain the NAS-PDU IE, the SAPI IE and the CN Domain Indicator IE. If present, the RAB Contexts List IE shall contain for each addressed RAB:

– the RAB ID IE;

– if available, the DL GTP-PDU Sequence Number IE;

– if available, the UL GTP-PDU Sequence Number IE;

– if available, the DL N-PDU Sequence Number IE;

– if available, the UL N-PDU Sequence Number IE.

Handling in case of RNSAP Relocation:

In case of RNSAP Relocation for each CS RAB operated in support mode (see TS 25.415 [6] for the definition of “support mode”) the source RNC shall include within the RANAP RELOCATION INFORMATION message the RNSAP Relocation Parameters IE containing the RAB Parameters List IE which shall include the UP Information IE. For each CS RAB operated in support mode for which the user data frame numbering is based on time the source RNC shall include the Timing Difference UL-DL IE within the UP Information IE.

In case of RNSAP Relocation for each PS RAB for which data volume reporting was configured, the source RNC shall include the RAB Data Volume Reports IE within the RAB Parameters List IE included in the RANAP RELOCATION INFORMATION message.

In case Location Reporting was configure at the source RNC for periodic reporting and/or report upon change of Service area and/or direct reporting, the source RNC shall include the Location Reporting Transfer Information IE within the RANAP RELOCATION INFORMATION message.

The Periodic Reporting Indicator IE within the Location Reporting Transfer Information IE shall be set to “periodic SAI” if periodic reporting is requested and the location information is requested to be a Service Area Identifier, to “periodic Geo” if periodic reporting is requested and the location information is requested to be a geographical area.

The Direct Reporting Indicator IE within the Location Reporting Transfer Information IE shall be set to “direct SAI” if periodic reporting is requested and the location information is requested to be a Service Area Identifier, to “direct Geo” if periodic reporting is requested and the location information is requested to be a geographical area.

The conditions for the presence of further IEs within the Location Reporting Transfer Information are specified in subclause 8.19.2.

If signalling based trace activation was triggered at the source RNC, the RANAP RELOCATION INFORMATION shall contain the UE Identity IE and the Trace Propagation Parameters IE in order to continue tracing at the target RNC accordingly.

11.3 RANAP Enhanced Relocation Information

11.3.1 General

The purpose of the RANAP Enhanced Relocation Information procedure is to handle the RANAP-related information that is carried transparently during enhanced relocation from a source RNC to a target RNC by RNSAP via the Iur Interface.

11.3.2 Operation

When during enhanced relocation it becomes necessary in the source RNC to generate RANAP information for transfer to the relocation target, the source RNC shall form a RANAP ENHANCED RELOCATION INFORMATION REQUEST message. The message shall be encoded according to the encoding rules specified for RANAP in the similar manner as for the normal RANAP messages. The outcome of the encoding will be an octet string, which shall be given to the appropriate local process for transparent transfer to the target RNC.

When the RANAP process in the target RNC receives an octet string containing a RANAP ENHANCED RELOCATION INFORMATION REQUEST message that had been transparently transferred from the source RNC, it shall decode it according to the encoding rules specified for RANAP. This process is similar to receiving any normal RANAP message. The decoded information shall be passed to the appropriate processes in the RNC.

Upon reception of the RANAP ENHANCED RELOCATION INFORMATION REQUEST message, the target RNC shall initiate allocation of requested resources.

The RANAP ENHANCED RELOCATION INFORMATION REQUEST message shall contain the following IE:

– Source RNC To Target RNC Transparent Container IE;

The RANAP ENHANCED RELOCATION INFORMATION REQUEST message may contain the following IEs:

– Old Iu Signalling Connection Identifier CS domain IE; if a connection to the CS domain exists;

– Old Iu Signalling Connection Identifier PS domain IE; if a connection to the PS domain exists;

– Global CN-ID for CS, if a connection to the CS domain exist;

– Global CN-ID for PS, if a connection to the PS domain exist;

– RABs to be Setup List;

– SNA Access Information IE (if available);

– UESBI-Iu IE (if available);

– Selected PLMN identity IE if in MOCN or GWCN configuration;

– CN MBMS Linking Information IE (if available);

– UE Aggregate Maximum Bit Rate IE;

– Anchor PLMN Identity IE (if available).

For each RAB requested to relocate in the RABs to be Setup List, the RANAP ENHANCED RELOCATION INFORMATION REQUEST message shall contain the following IEs in the RABs To Be Setup List IE:

– RAB ID IE;

– CN domain indicator IE;

– RAB parameters IE;

– User Plane Information IE;

– Source Side Iu UL TNL Information IE;

– Data Volume Reporting Indication IE (only for PS);

– PDP Type Information IE (only for PS).

For each RAB requested to relocate the message may include the following IEs:

– Data Forwarding TNL Information IE;

– Service Handover IE;

– Alternative RAB Parameter Values IE;

– E-UTRAN Service Handover IE;

– PDP Type Information extension IE (may be included if PDP Type Information IE is included).

If the Data Forwarding TNL Information IE is included in the RANAP ENHANCED RELOCATION INFORMATION REQUEST message, it indicates Iur UP resources, made available by the source RNC for forwarding of UL user data.

Note: The Source Side Iu UL TNL Information IE (in contrary to the Data Forwarding TNL Information IE) contains information to enable the target RNC to start transmission of user data towards the CN once the relocations have been successfully executed.

If the UE Aggregate Maximum Bit Rate IE is included in the RANAP ENHANCED RELOCATION INFORMATION REQUEST message, the target side shall, if supported, store the received UE Aggregate Maximum Bit Rate parameters to control the aggregate data rate of non-GBR traffic for this UE.

The RANAP ENHANCED RELOCATION INFORMATION REQUEST message shall contain the information (if any) required by the target RNC to build at least the same set of RABs as existing for the UE before the relocation and therefore the RANAP ENHANCED RELOCATION INFORMATION REQUEST may contain the RABs to be SETUP List IE.

The resource allocation actions executed by the target RNC are:

If the Relocation Type IE is set to "UE involved in relocation of SRNS":

– The target RNC should not accept a requested RAB if the RAB did not exist in the source RNC before the relocation;

– The target RNC may accept a requested RAB only if the RAB can be supported by the target RNC;

– Other RABs shall be rejected by the target RNC in the RANAP ENHANCED RELOCATION INFORMATION RESPONSE message with an appropriate value in the Cause IE, e.g. "Unable to Establish During Relocation";

– The target RNC shall include information adapted to the resulting RAB configuration in the target to source RNC transparent container to be included in the RANAP ENHANCED RELOCATION INFORMATION RESPONSE message sent to the source RNC;

– If any alternative RAB parameter values have been used when allocating the resources, these RAB parameter values shall be included in the RANAP ENHANCED RELOCATION INFORMATION RESPONSE message within the Assigned RAB Parameter Values IE;

– If d-RNTI for No IuCS UP IE is contained in the RANAP ENHANCED RELOCATION INFORMATION REQUEST message, the target RNC shall use this information to configure the resource for the UE over Iur during the relocation.

If the Relocation Type IE is set to "UE not involved in relocation of SRNS":

– The target RNC shall not accept a requested RAB if the RAB did not exist in the source RNC before the relocation;

– The target RNC may accept a RAB only if the radio bearer(s) for the RAB either exist(s) already and can be used for the RAB by the target RNC, or do(es) not exist before the relocation but can be established in order to support the RAB in the target RNC;

– If existing radio bearers are not related to any RAB that is accepted by the target RNC, the radio bearers shall be ignored during the relocation of SRNS and the radio bearers shall be released by the radio interface protocols after completion of relocation of SRNS;

– Usage of alternative RAB parameter values is not applicable for any relocation of type "UE not involved in relocation of SRNS".

If the UE History Information IE is included in the RANAP ENHANCED RELOCATION INFORMATION REQUEST message and the target RNC is configured to collect the information, the target RNC shall, if supported, collect information defined in the UE History Information IE.

The Global CN ID IE and Old Iu Signalling Identifier IE (for PS and/or for CS) are used by the target RNC to establish new Iu Signalling connection(s) between the target RNC towards the CS and/or PS domain.

The RANAP ENHANCED RELOCATION INFORMATION REQUEST message may also include an alternative RAB configuration for a RAB specified in the Alternative RAB configuration IE in the Alternative RAB Parameter Values IE. If Alternative RAB configuration IE for a RAB is included in the RANAP ENHANCED RELOCATION INFORMATION REQUEST message, the target RNC is allowed to use the alternative configuration.

The RNC shall, if supported, use the UESBI-Iu IE when included in the RANAP ENHANCED RELOCATION INFORMATION REQUEST message. If UESBI-Iu IE contains an IMEISV the RNC may use this information to determine the characteristics of the UE for subsequent handling.

If the CN MBMS Linking Information IE is included in the RANAP ENHANCED RELOCATION INFORMATION REQUEST message, the RNC shall, if supported, use the CN MBMS Linking Information IE to perform suitable UE linking as described in TS 25.346 [42].

If the SNA Access Information IE is contained in the RANAP ENHANCED RELOCATION INFORMATION REQUEST message, the target RNC shall store this information and use it to determine whether the UE has access to radio resources in the UTRAN. The target RNC shall consider that the UE is authorised to access only the PLMNs identified by the PLMN identity IE in the SNA Access Information IE. If the Authorised SNAs IE is included for a given PLMN (identified by the PLMN identity IE), then the target RNC shall consider that the access to radio resources for the concerned UE is restricted to the LAs contained in the SNAs identified by the SNAC IEs.

If the SNA Access Information IE is not contained in the RANAP ENHANCED RELOCATION INFORMATION REQUEST message, the target RNC shall consider that no access restriction applies to the UE in the UTRAN.

If the Trace Recording Session Information IE is provided within the Source RNC to Target RNC Transparent Container IE, the Target RNC should store that information to include it in a potential future Trace Record for that UE.

After all necessary resources for accepted RABs including the initialised Iu user plane, are successfully allocated, the target RNC shall send a RANAP ENHANCED RELOCATION INFORMATION RESPONSE message to the source RNC.

For each RAB successfully setup the RNC shall include the following IEs in the RABs Setup List IE:

– RAB ID.

For each RAB the target RNC has admitted to execute data forwarding, the target RNC shall include the Data Forwarding Information IE in the RANAP ENHANCED RELOCATION INFORMATION RESPONSE message. If no ALCAP is used, the RNC shall include the DL Forwarding Transport Layer Address IE and the DL Forwarding Transport Association IE within the Data Forwarding Information IE in the RANAP ENHANCED RELOCATION INFORMATION RESPONSE message.

If applicable, the target RNC shall have executed the initialisation of the user plane mode between the source and the target RNC as requested by the source RNC in the User Plane Mode IE. If the target RNC cannot initialise the requested user plane mode for any of the user plane mode versions in the UP Mode Versions IE according to the rules for initialisation of the respective user plane mode versions, as described in TS 25.415 [6], the target RNC may either decide to not relocate the respective RAB or to omit data forwarding for that RAB.

For each RAB the RNC is not able to setup during the Enhanced Relocation Information procedure, the RNC shall include the CN Domain Indicator IE RAB ID IE and the Cause IE within the RABs Failed To Setup IE. The resources associated with the RABs indicated as failed to set up shall not be released in the source RNC until the relocation is completed. This is in order to make a return to the old configuration possible in case of a failed or cancelled relocation.

The RANAP ENHANCED RELOCATION INFORMATION RESPONSE message sent to the source RNC shall, if applicable, include the Target RNC To Source RNC Transparent Container IE.

Handling in case of RNSAP Relocation:

In case of RNSAP Relocation for each CS RAB operated in support mode (see TS 25.415 [6] for the definition of “support mode”) the source RNC shall include within the RANAP ENHANCED RELOCATION INFORMATION REQUEST message the RAB Parameters List IE which shall include the UP Information IE. For each CS RAB operated in support mode for which the user data frame numbering is based on time the source RNC shall include the Timing Difference UL-DL IE within the UP Information IE.

The source RNC shall also include within the RANAP ENHANCED RELOCATION INFORMATION REQUEST message

– the CSG Id IE (if available),

– the CSG Membership Status IE (if available).

Handling in case of Enhanced Relocation between RNC and hybrid cell:

The source RNC shall also include within the RANAP ENHANCED RELOCATION INFORMATION REQUEST message the CSG Id IE, if available. If the CSG Id IE is included, the CSG Membership Status IE shall be included as well.

Annex A (informative):
RANAP guidelines