9.1.5A NI-LR using Location Based Routing – applicable to North American Emergency Calls only

23.2713GPPFunctional stage 2 description of Location Services (LCS)Release 17TS

Figure 9.4A illustrates positioning for an emergency service call using location based routing.

Figure 9.4A: Positioning for a NI-LR Emergency Service Call using Location Based Routing

9.1.5A.1 Location Preparation Procedure

1) An initially idle UE requests radio connection setup indicating a request for an Emergency Service call to the VMSC/MSC server via RAN.

2) RAN shall convey the CM service request to the core network. (Before having a CM connection there must be a radio connection.) The UE may identify itself using a TMSI, IMSI or IMEI.

3) The VMSC/MSC server determines that the serving cell serves an area that contains portions of multiple emergency services zones. Therefore, the VMSC/MSC server delays call setup and initiates procedures to obtain the UE’s location for routing the emergency call to the emergency services LCS client. The VMSC/MSC server sends a Location Request message to RAN associated with the UE’s current location area. This message includes the type of location information requested, the UE’s location capabilities and a QoS with low delay and low horizontal accuracy.

9.1.5A.2 Positioning Measurement Establishment Procedure

4) RAN determines the positioning method and instigates the particular message sequence for this method, as specified in UTRAN Stage 2, TS 25.305 [1] and GERAN Stage 2, TS 43.059 [16].

9.1.5A.3 Location Calculation and Release Procedure

5) When a location estimate best satisfying the requested QoS has been obtained, RAN returns it to the VMSC/MSC server. If a location estimate could not be obtained, the RAN returns a location response containing a failure cause and no location estimate. If a failure is received, the VMSC/MSC server initiates emergency call setup using the normal NI-LR procedures.

6) The VMSC/MSC server sends a MAP Subscriber Location Report to a GMLC associated with the emergency services provider to which the emergency call will be sent. This message shall carry any location estimate returned in step 5, the age of this estimate and may carry the MSISDN, IMSI, IMEI of the calling UE, the information about the positioning method used and the serving cell identity or SAI of the UE. In case of a SIM-less emergency call, or a non-registered (U)SIM emergency call, the IMEI shall be always sent and the MSISDN shall be populated with a non-dialable callback number as specified in clause 6.4.3. The message shall also indicate the event that triggered the location report. Any NA-ESRD and NA-ESRK that was assigned by the VMSC/MSC server shall be included. The message shall also include an indication that the VMSC/MSC server supports the capability to replace an NA-ESRK or NA-ESRD value with the one assigned by the GMLC. The VMSC/MSC server and GMLC may record charging information.

7) The GMLC translates the location estimate into a zone identity and assigns either a NA-ESRK or a NA-ESRD, which was requested by the VMSC/MSC server. The GMLC shall include either the NA-ESRK value or the NA-ESRD value in the MAP Subscriber Location Report ack and send it to the VMSC/MSC server. The GMLC stores either the assigned NA-ESRD or the assigned NA- ESRK and any NA-ESRD that was sent by the VMSC/MSC server in step 6.

9.1.5A.4 Location Preparation Procedure

8) The emergency call procedure is applied. The VMSC/MSC server, RAN and UE continue the normal procedure for emergency call origination towards the appropriate emergency services client. Call setup information sent into the PSTN may include the UE location plus information that will enable the emergency service provider to request UE location at a later time (NA-ESRD or NA-ESRK in North America). The NA-ESRK or NA-ESRD used shall be the one received from the GMLC. If a NA-ESRK or NA-ESRD is not received from the GMLC then the VMSC/MSC server shall employ default routing for the call using a default NA-ESRK, default NA-ESRD or other default number as in clause 9.1.5.1 step 3.

9) At any time after step 8, the emergency services LCS client may request location information.

10) At any time after step 6, the GMLC may send a MAP Provide Subscriber Location message to the VMSC/MSC server. This message includes a QoS with higher delay and higher horizontal accuracy required for an emergency call. In case of a SIM-less emergency call, or a non-registered (U)SIM emergency call, the IMEI shall be included in the message.

If the GMLC is capable of determining whether the initial location satisfies the higher accuracy requirements for an emergency call, then the GMLC may not need to request for a higher accuracy location.

11) The VMSC/MSC server sends a Location Request message to RAN. This message includes the type of location information requested, the UE’s location capabilities and requested higher accuracy QoS.

9.1.5A.5 Positioning Measurement Establishment Procedure

12) same as step 4.

9.1.5A.6 Location Calculation and Release Procedure

13) same as step 5.

14) The VMSC/MSC server returns the location information and its age, the information about the positioning method used and the serving cell identity or SAI of the UE to the GMLC. The GMLC shall replace the previously stored low accuracy location information with the higher accuracy information for later retrieval by the emergency services LCS client. The VMSC/MSC server and GMLC may record charging information.

15) The GMLC may forward the information received in the previous step to the emergency services LCS client. The client is expected to have requested this information from GMLC before. The information about the positioning method used may be sent with this location information from the GMLC to the LCS client.

16) same as step 10 for normal NI-LR.

17) same as step 11 for normal NI-LR.

18) same as step 12 for normal NI-LR.