7 Functions of RANAP

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

RANAP protocol has the following functions:

– Relocating serving RNC. This function enables to change the serving RNC functionality as well as the related Iu resources (RAB(s) and Signalling connection) from one RNC to another.

– Overall RAB management. This function is responsible for setting up, modifying and releasing RABs.

– Queuing the setup of RAB. The purpose of this function is to allow placing some requested RABs into a queue, and indicate the peer entity about the queuing.

– Requesting RAB release. While the overall RAB management is a function of the CN, the RNC has the capability to request the release of RAB.

– Release of all Iu connection resources. This function is used to explicitly release all resources related to one Iu connection.

– Requesting the release of all Iu connection resources. While the Iu release is managed from the CN, the RNC has the capability to request the release of all Iu connection resources from the corresponding Iu connection.

– SRNS context forwarding function. This function is responsible for transferring SRNS context from the RNC to the CN for intersystem change in case of packet forwarding.

– Controlling overload in the Iu interface. This function allows adjusting the load in the control plane of the Iu interface.

– Resetting the Iu. This function is used for resetting an Iu interface.

– Sending the UE Common ID (permanent NAS UE identity) to the RNC. This function makes the RNC aware of the UE’s Common ID.

– Paging the user. This function provides the CN for capability to page the UE.

– Controlling the tracing of the subscriber or user equipment activity. This function allows setting the trace mode for a given subscriber or user equipment. This function also allows the deactivation of a previously established trace.

– MDT function. This function is to enable the transfer of MDT measurements collected by the UE.

– Transport of NAS information between UE and CN (see TS 24.008 [8]). This function has two sub-classes:

1. Transport of the initial NAS signalling message from the UE to CN. This function transfers transparently the NAS information. As a consequence also the Iu signalling connection is set up.

2. Transport of NAS signalling messages between UE and CN, This function transfers transparently the NAS signalling messages on the existing Iu signalling connection. It also includes a specific service to handle signalling messages differently.

– Controlling the security mode in the UTRAN. This function is used to send the security keys (ciphering and integrity protection) to the UTRAN, and setting the operation mode for security functions.

– Controlling location reporting. This function allows the CN to operate the mode in which the UTRAN reports the location of the UE.

– Location reporting. This function is used for transferring the actual location information from RNC to the CN.

– Data volume reporting function. This function is responsible for reporting unsuccessfully transmitted DL data volume over UTRAN for specific RABs.

– Reporting general error situations. This function allows reporting of general error situations, for which function specific error messages have not been defined.

– Location related data. This function allows the CN to either retrieve from the RNC deciphering keys (to be forwarded to the UE) for the broadcast assistance data, or request the RNC to deliver dedicated assistance data to the UE.

– Information Transfer. This function allows the CN to transfer information to the RNC.

– Uplink Information Exchange. This function allows the RNC to transfer or request information to the CN. For instance the RNC has the capability to request MBMS specific information to the CN e.g. the Multicast Service lists for a given UE or the IP Multicast Address and APN for one or several MBMS Bearer Services.

– MBMS RANAP overall function. This function allows the following different sub-functions:

– MBMS RAB management. This function is responsible for setting up, updating and releasing the MBMS RAB as well as the MBMS Iu signalling connection corresponding to one MBMS Session. The MBMS RAB is defined for the CN PS domain only.

– MBMS CN (PS domain) de-registration. This function makes the RNC aware that a given Multicast Service is no longer available.

– MBMS UE linking/de-linking. This function makes the RNC aware that a given UE, with existing Iu-ps signalling connection, has joined/left some Multicast Service(s).

– Requesting MBMS Service registration/de-registration. While the overall MBMS CN de-registration is a function of the CN (PS domain), the RNC has the capability to register/de-register to a specific Multicast Service.

– QoE function. This function is to enable the transfer of QoE measurements collected by the UE.

These functions are implemented by one or several RANAP elementary procedures described in the following clause.