5.14 Configuration Transfer procedure

23.4013GPPGeneral Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) accessRelease 18TS

The purpose of the Configuration Transfer is to enable the transfer of information between two eNodeBs at any time via S1 interface and the Core Network. An example of application is to exchange the eNodeBs IP addresses in order to be able to use X2 interface between the eNodeBs for Self-Optimised Networks (SON), as specified in TS 36.413 [36].

5.14.1 Architecture Principles for Configuration Transfer

Configuration Transfer between two eNodeBs follows the principles used by RAN Information Management (RIM) procedures (see clause 5.15) between UTRAN, E-UTRAN and GERAN i.e. providing a generic mechanism for the exchange of arbitrary information between applications belonging to the RAN nodes. However Configuration Transfer is only used for intra- E-UTRAN information exchange whereas RIM procedures are designed for inter-RAT information exchange involving GERAN/UTRAN. Such a separate procedure allows avoiding impacts to other RAT access systems when transferred information is added or modified.

The information is transferred via the MME core network node(s). In order to make the information transparent for the Core Network, the information is included in an E-UTRAN transparent container that includes source and target eNodeB addresses, which allows the Core Network nodes to route the messages. If the information is to be transferred between a source eNodeB and a target en-gNB via a target eNodeB for Dual Connectivity with E-UTRAN as Master RAN node and NR as Secondary RAN node as defined in TS 37.340 [85], the source eNodeB indicates the target en-gNB and may indicate the connected target eNodeB as described in TS 36.300 [5], and the target eNode B further transfers the E-UTRAN transparent container to the en-gNB transparently. The mechanism is depicted in figure 5.14 1. An example for such transferred information is the SON information, as specified in TS 36.413 [36].

Figure 5.14-1: inter E-UTRAN Configuration Transfer basic network architecture

The E-UTRAN transparent containers are transferred from the source E-UTRAN node to the destination E-UTRAN node by use of Configuration Transfer messages.

An eNodeB Configuration Transfer message is used from the eNodeB to the MME over S1 interface, a MME Configuration Transfer message is used from the MME to the eNodeB over S1 interface, and a Configuration Transfer Tunnel message is used to tunnel the E-UTRAN transparent container from a source MME to a target MME over the S10 interface.

Each Configuration Transfer message carrying the E-UTRAN transparent container is routed and relayed independently by the core network node(s). Any relation between messages is transparent for the MME, i.e. a request/response exchange between applications, for example SON applications, is routed and relayed as two independent messages by the MME. An MME supporting the Configuration Transfer procedures provides addressing, routing and relaying functions.

5.14.2 Addressing, routing and relaying

5.14.2.1 Addressing

All the Configuration Transfer messages contain the addresses of the source and destination RAN nodes. An eNodeB is addressed by the Target eNodeB Identifier. For Dual Connectivity with E-UTRAN as Master RAN node and NR as Secondary RAN node as defined in TS 37.340 [85], the destination RAN node includes the candidate en-gNB Identifier and may include a target eNodeB Identifier for the target eNodeB which is X2 connected to the candidate en-gNB and a TAI associated with the en-gNB.

5.14.2.2 Routing

The following description applies to all the Configuration Transfer messages used for the exchange of the E-UTRAN transparent container.

The source RAN node sends a message to its MME including the source and destination addresses. The MME uses the destination address to route the message encapsulated in a GTPv2 message to the correct MME via the S10 interface (see TS 29.274 [43]).

The MME connected to the target eNodeB decides which RAN node to send the message to, based on the destination address. For Dual Connectivity with E-UTRAN as Master RAN node and NR as Secondary RAN node as defined in TS 37.340 [85], target eNodeB decides which candidate en-gNB to send the message to, based on the destination address.

5.14.2.3 Relaying

The MME performs relaying between GTPv2 messages as described in TS 29.274 [43]. The MME performs relaying between S1 and S10 messages as described in TS 36.413 [36], TS 23.501 [83] and TS 29.274 [43]. The Target eNodeB performs relaying between S1 and X2 message as described in TS 36.413 [36] and TS 36.423 [76].

5.14.2.4 Applications using the Configuration Transfer procedures

The RAN node applications, which use the Configuration Transfer procedures, are fully transparent for the MME. These applications are described in RAN specifications. An example of application is the transfer of information required for Self-Optimised Networks (SON).