Figure 6.5.1-1 shows the protocol layering used to support transfer of LPPa PDUs between an E-SMLC and eNode B.
The LPPa protocol is transparent to the MME. The MME routes the LPPa PDUs transparently based on a short Routing ID which corresponds to the involved E-SMLC node over the S1 interface without knowledge of the involved LPPa transaction. It carries the LPPa PDUs over S1 interface either in UE associated mode or non-UE associated mode.
Figure 6.5.2-1 shows LPPa PDU transfer between an E-SMLC and eNode B to support positioning of a particular UE.
Step 1.
Steps 1 to 3 are triggered when the E-SMLC needs to send an LPPa message to the serving eNode B for a target UE as part of an LPPa positioning activity. The E-SMLC then sends an LCS-AP PDU (as specified in
TS 29.171) to the MME including the Correlation ID corresponding to the UE and carrying an LPPa PDU comprising the message.
Step 2.
If the UE is in ECM-IDLE state (e.g. if the S1 connection was previously released due to data and signalling inactivity), the MME performs a network triggered service request as defined in
TS 23.401 in order to establish a signalling connection with the UE and assign a serving eNode B.
Step 3.
The MME forwards the LPPa PDU to the serving eNode B in an S1AP Downlink UE Associated LPPa Transport message over the S1 signalling connection corresponding to the UE and includes the Routing ID related to the E-SMLC. The MME need not retain state information for this transfer - e.g. can treat any response in step 4 as a separate non-associated transfer.
Step 4.
Steps 4 and 5 are triggered when a serving eNode B needs to send an LPPa message to the E-SMLC for a target UE as part of an LPPa positioning activity. The eNode B then sends an LPPa PDU to the MME in an S1AP Uplink UE Associated LPPa Transport message and includes the Routing ID received in step 3.
Step 5.
The MME forwards the LPPa PDU to the E-SMLC associated with the Routing ID received in step 4 in an LCS-AP PDU (as specified in
TS 29.171) including the Correlation ID corresponding to the UE. Steps 1 to 5 may be repeated.
Figure 6.5.3-1 shows LPPa PDU transfer between an E-SMLC and eNodeB when related to gathering data from the eNodeB for positioning support for all UEs.
Step 0.
An eNodeB may communicate with several TPs (including PRS-only TPs in case of PRS-based TBS is supported) to configure TPs, obtain TP configuration information, etc.
Step 1.
Steps 1 and 2 are triggered when the E-SMLC needs to send an LPPa message to an eNodeB to obtain data related to the eNodeB, and possibly associated TPs. The E-SMLC determines an MME with access to the eNodeB and then sends an LCS-AP PDU (as specified in
TS 29.171) to the MME carrying an LPPa PDU, the global identity of the eNodeB and the identity of the E-SMLC.
Step 2.
The MME forwards the LPPa PDU to the identified eNode B in an S1AP Downlink Non UE Associated LPPa Transport message and includes the Routing ID related to the E-SMLC. The MME need not retain state information for this transfer - e.g. can treat any response in step 3 as a separate non-associated transfer.
Step 3.
Steps 3 and 4 are triggered when an eNode B needs to send an LPPa PDU to an E-SMLC containing data applicable to the eNodeB, and possibly associated TPs. The eNodeB determines an MME with access to the E-SMLC and then sends an LPPa PDU to the MME in an S1AP Uplink Non UE Associated LPPa Transport message. The eNodeB includes the Routing ID related to the E-SMLC received at step 2.
Step 4.
The MME forwards the LPPa PDU to the E-SMLC associated to the Routing ID indicated in step 3 and includes the global identity of the eNodeB and the identity of the E-SMLC in an LCS-AP PDU (as specified in
TS 29.171). Steps 1 to 4 may be repeated.
Figure 6.5.4-1 shows LPPa PDU transfer between an E-SMLC and eNode B to support broadcast of assistance data.
Step 1.
Step 1 is triggered when the E-SMLC needs to send new or updated assistance information to an eNodeB for broadcasting in positioning system information messages. The E-SMLC determines an MME with access to the eNodeB and then sends an LCS-AP PDU (as specified in
TS 29.171) to the MME carrying an LPPa PDU, the global identity of the eNodeB and the identity of the E-SMLC.
Step 2.
The MME forwards the LPPa PDU to the identified eNode B in an S1AP Downlink Non UE Associated LPPa Transport message and includes the Routing ID related to the E-SMLC. The MME need not retain state information for this transfer.
Figure 6.5.4-2 shows LPPa PDU transfer between an eNode B and E-SMLC for providing feedback to the E-SMLC on assistance data broadcasting.