Section: 5.7A.3 Secondary RAT Usage Data Reporting Procedure
Content: The procedure in Figure 5.7A.3-1 may be used to report Secondary RAT usage data from eNodeB to the MME. It is executed by the eNodeB to report the Secondary RAT usage data information which is then included in messages on S11 towards Serving GW and S5/S8 interface to the PGW (e.g. during I-RAT handover procedures, S1 handover, X2 handover). This then further uses existing EPC signalling of the procedures involved. The procedure in Figure 5.7A.3-2 may be used to report the Secondary RAT usage data from MME to the Serving GW. Optionally, it is used to report the Secondary RAT usage data from Serving GW to the PDN GW when the reporting to PDN GW is activated. If the Secondary RAT usage data is provided by an S1AP message from eNodeB to MME other than the one indicated in Figure 5.7A.3-1, the procedures in clause 5.7A.3-2 may be used to transfer the secondary RAT usage data to the Serving GW and PDN GW (e.g. during S1 Release procedure). The eNodeB may also provide the user location information, e.g. ECGI, PSCell ID. During IRAT handovers, the procedures 5.7A.3-1 to 5.7A.3-2 in its entirety is executed to provide reporting of Secondary RAT usage data to the Serving GW and to the PDN GW if PGW secondary RAT usage data reporting is active. Handover related signalling of IRAT procedures may be used to provide reporting of Secondary RAT usage data to the Serving GW instead of the signalling of figure 5.7A.3-2, when PGW secondary RAT usage data reporting is not active. Figure 5.7A.3-1: RAN Secondary RAT usage data Reporting procedure 1. The eNodeB, if it supports Dual Connectivity with Secondary RAT (using NR radio (see clause 4.3.2a on Support for Dual Connectivity), using unlicensed spectrum in the form of LAA/LWA/LWIP/NR-U (see clause 4.3.30)) and it is configured to report Secondary RAT usage data for the UE, depending on certain conditions documented in this specification, it shall send a RAN usage data Report message to the MME including the Secondary RAT usage data for the UE. The eNodeB will send only one RAN usage report for a UE when the UE is subject to handover by RAN. The RAN usage data report includes a handover flag to indicate when the message is sent triggered by X2-handover. If Dual Connectivity is active or had been activated by that eNodeB, the eNodeB shall add the PSCell ID (and the time elapsed since the Dual Connectivity was released if Dual Connectivity is no longer activated) to the RAT usage data Report message. In the case of X2 handover, the MME is expected to handle a secondary RAT data reporting received from the source eNodeB within a short time after Path Switch Request by forwarding it to the SGW, e.g. using the GW Secondary RAT usage data Reporting procedure. Figure 5.7A.3-2: GW Secondary RAT usage data Reporting procedure The eNodeB, if it supports Dual Connectivity with Secondary RAT (using NR radio (see clause 4.3.2a on Support for Dual Connectivity), using unlicensed spectrum in the form of LAA/LWA/LWIP/NR-U (see clause 4.3.30)) and it is configured to report Secondary RAT usage data for the UE, it shall send include the Secondary RAT usage data for the UE to the MME in certain messages depending on certain conditions documented elsewhere in this TS. Secondary RAT usage reporting from the eNodeB is provided using S1 signalling message which are either at the UE level (eg. Path Switch Request, etc), or at bearer level (eg. E-RAB modification indication, Deactivate bearer response, etc.) as captured in relevant clauses in this specification. If Secondary RAT usage report is provided in bearer level signalling message by the eNodeB, the Secondary RAT usage report is related only to the specific bearer. 1. The MME forwards the Secondary RAT usage data and User Location Information, PSCell ID to the SGW in a Change Notification Request (Secondary RAT usage data) message. If the SGW is requested to forward Secondary RAT usage data to the PGW, the MME includes a flag causing the SGW to forward this to the PGW. Also, the MME informs the Serving GW if the secondary RAT usage data shall not be processed by the Serving GW (e.g. during Serving GW relocation when the usage data is to be forwarded via the target Serving GW). 2. The Serving GW may, based on flags received in the previous message and local configuration in the Serving GW, send the Change Notification (Secondary RAT usage data) message to the PDN GW. 3. The PDN GW acknowledges receiving the Secondary RAT usage data for the UE by a Change Notification Ack() message to the Serving GW. 4. The SGW acknowledges by sending a Change Notification ack() message back to the MME.