For GERAN and UTRAN access networks, the core network sends location requests to the access network, which then sends the corresponding responses back to the core network.
Communication between access and core networks is accomplished through Iu interface in UMTS whereas the A, Gb and Iu interfaces are used for the purpose in GSM (see
TS 25.305 and
TS 43.059).
The core network request for a location estimate of a target UE shall contain sufficient information to enable location of the Target UE according to the required QoS using any positioning method supported by the PLMN and, where necessary, UE. For location services the core network may request the geographical co-ordinates and velocity of the Target UE.
In Iu mode the core network may also request in which Service Area the Target UE is located. The Service Area information may be used for routing of corresponding Emergency calls, or for CAMEL services.
In A/Gb mode this corresponds to the usage of Cell ID in the core network. It should be noted that the Service Area concept is different from the Localized Service Area concept used for SoLSA services.
When the location of a Target UE in Idle Mode is requested, the core network shall determine which RAN entity is associated with the Target UE.
The access network reports the location of the Target UE to the core network entities. The location report may contain the following information as defined in the corresponding location request:
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the geographical co-ordinates of the Target UE;
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the positioning method used to obtain the location estimate if the access network is either GERAN in the A/Gb mode, GERAN in the Iu mode or UTRAN in the Iu mode.
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the service area in which the Target UE is located;
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achieved quality level of the location estimate;
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velocity estimate of the Target UE, if available;
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achieved quality level of the velocity estimate of the Target UE, if available.
For E-UTRAN access networks, the MME sends location requests to the E-SMLC via the SLs interface (see
clause 7.8). The E-SMLC then sends core network measurement requests, as described in
clause 7.1a.1, to the access network via the MME. The access network sends corresponding network measurement reports, as described in
clause 7.1a.2, back to the E-SMLC, again via the MME.
Communication between access and core networks is accomplished through S1 interface in E-UTRAN (see
TS 36.305.
The core network request for network measurements shall contain sufficient information to enable the desired measurements to be provided by the access network.
The core network shall determine which RAN entities are associated with the Target UE.
The access network reports measurements pertaining to the Target UE back to the E-SMLC as defined in the corresponding core network measurement request.
The Um, Uu and Uu-LTE interfaces are used to communicate among the LCS entities associated with the BSC, RNC, the UE and the stand-alone (Type A) Location Measurement Units (LMU). The Um, Uu and Uu-LTE interfaces are also used to communicate between the LCS entities in the core network and the UE.
The Um/Uu/Uu-LTE interfaces may pass measurement requests and results to and from UE or the stand-alone LMU.
The Um/Uu/Uu-LTE interfaces may also pass location requests from internal or external LCS Clients (Applications) at the UE. Note that these requests may require the services of the LCS entities associated with the core network to authenticate clients and subscriber subscriptions to aspects of the LCS.
The Um/Uu/Uu-LTE interfaces may also be used for broadcast of information that may be used by the UE or stand-alone LMU for their LCS operations. This may, for example, include timing information about nearby Node-B/BTS transmissions that may assist the UE or LMU in making their measurements. In UTRAN code information may be included.
The Um, Uu and Uu-LTE interfaces may also pass messages relating to changes or reporting of the data associated with the Location System Operations Function (LSOF) in the UE or the remote LMU.
UTRAN Stage 2 specification
TS 25.305 specifies LCS signalling over the Uu interface and GERAN Stage 2 specification
TS 43.059 specifies LCS signalling over the Um interface correspondingly. E-UTRAN Stage 2 specification
TS 36.305 specifies LCS signalling over the Uu-LTE interface.
Message segmentation is specified in GERAN LCS Stage 2,
TS 43.059.
The following interfaces are based on MAP in LCS.
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Lh interface: interface between GMLC and HSS. This interface is used by the GMLC to request the address of the H-GMLC, and/or the address of the visited MSC or SGSN for a particular target UE whose location has been requested
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Lg interface: interface between GMLC MSC and GMLC - SGSN. This interface is used by the GMLC to convey a location request to the MSC or SGSN currently serving a particular target UE whose location was requested. The interface is used by the MSC or SGSN to return location results to the GMLC.
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Lc interface: interface between GMLC and gsmSCF, CAMEL. This interface is used to get location information for CAMEL based services.
The following MAP services are defined for LCS.
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MAP-SEND-ROUTING-INFO-FOR-LCS Service.
This service is used between the GMLC and the HLR/HSS to retrieve the routing information needed for routing a location service request to the serving VMSC , SGSN. The service may be used in GMLC - HSS interface to retrieve routing information in order to route the location service request to the correct VMSC, SGSN and MSC Server.
In case the service is used between the R-GMLC and the HSS, the H-GMLC address of the target UE to be located is retrieved. The address of the V-GMLC associated with the serving node and PPR may also be retrieved.
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MAP-PROVIDE-SUBSCRIBER-LOCATION Service.
This service is used by a GMLC to request the location and optionally, velocity, of a target UE from the visited MSC, SGSN or MSC Server at any time.
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MAP-SUBSCRIBER-LOCATION-REPORT Service.
This service is used by a VMSC, SGSN or MSC Server to provide the location of a target UE to a GMLC when a request for location is either implicitly administered or made at some earlier time.
The MAP Subscriber Location Report could also be used to send information about location and, if requested and available, velocity of the Target UE (for MO LR) to an external client.
Lpp is the interface between H-GMLC and PPR. If the UE subscribers LCS privacy information is kept in the PPR this interface is used by the H-GMLC to request the PPR to perform a privacy check. The Lpp interface shall conform to the protocol as specified in (reference to be added) and the procedures defined in
clause 9 of this specification.
Via the LCS Authorisation Request, the H-GMLC can request the PPR to perform the privacy check. There exist two types of LCS Authorisation Request:
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LCS Authorisation Request without location estimate (send by H-GMLC before location request);
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LCS Authorisation Request with location estimate (to check location related privacy settings).
The following attributes are identified for LCS Authorisation Request information flow:
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Target UE identity, (one or both of MSISDN and IMSI), if needed;
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If PPR contains PMD functionality the LCS Authorisation Request may contain the same information as the LCS Identity request, i.e. the pseudonym of the target UE, if needed.
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Indication on call/session related MT-LR;
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LCS Client identity, i.e. LCS client external identity or internal identity;
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LCS Client type, (i.e. Value added, Emergency, PLMN operator or Lawful interception);
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LCS Client name, if needed (and type of LCS client name if available);
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Service type, if needed;
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Codeword, if needed;
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Requestor identity, if needed (and type of Requestor identity if available);
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Type of location, i.e. "current location", "current or last known location" or "initial location";
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Velocity of the UE, if needed;
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LCS capability sets of serving nodes, if needed;
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Location estimate, if needed and available (This is only relevant for LCS Authorisation Request with location estimate);
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Type of Deferred Location Request, if needed (i.e. UE available, Change of Area, Motion or Periodic Location);
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Geographic area for change of area event, if needed;
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Parameters for Periodic Location event, if needed (i.e. reporting interval, total number of reports, request for MO-LR short circuit).
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Parameters for change of area event, if needed (i.e. type of area event, indication of single or multiple reports, minimum interval between reports, whether location estimates are requested, duration, maximum interval between reports, maximum sampling interval);
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Parameters for motion event, if needed (i.e. linear distance threshold, indication of single or multiple reports, minimum interval between reports, whether location estimates are requested, duration, maximum interval between reports, maximum sampling interval).
The LCS Authorisation Response is sent by the PPR to the H-GMLC as the result for the LCS Authorisation Request.
The following attributes are identified for the LCS Authorisation Response information flow:
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Indicator for location request is to be barred, if needed. If this is set, no other indicators shall be included in the response;
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Indicator for call/session related class of privacy check related actions, if needed;
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positioning not allowed;
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positioning allowed without notifying the UE user;
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positioning allowed with notification to the UE user;
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positioning requires notification and verification by the UE user; positioning is allowed only if granted by the UE user or if there is no response to the notification;
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positioning requires notification and verification by the UE user; positioning is allowed only if granted by the UE user.
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Indicator for call/session unrelated class of privacy check related actions, if needed;
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positioning not allowed;
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positioning allowed without notifying the UE user;
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positioning allowed with notification to the UE user;
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positioning requires notification and verification by the UE user; positioning is allowed only if granted by the UE user or if there is no response to the notification;
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positioning requires notification and verification by the UE user; positioning is allowed only if granted by the UE user.
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Pseudo external ID, if needed (see Annex C);
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Indicator on additional privacy check with location estimate, if needed;
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Indicator on additional notification/verification by the UE user without positioning (existing location estimate to be returned to the LCS Client if this is successful), if needed;
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Same information as in the LCS Identity Response, in case the PMD is integrated in PPR, if needed;
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Indicator for MO-LR short circuit allowed/not allowed, if needed.
The LCS Privacy Profile Update notification is sent to the H-GMLC from the PPR in order to notify the H-GMLC about the change of UEs privacy profile.
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Target UE identity, (one or both of MSISDN and IMSI);
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Indication on the changed UEs privacy profile
The LCS Privacy Profile Update notification ack. is sent to the PPR as the result of the LCS Privacy Profile Update Request by H-GMLC.
Lid is the interface between H-GMLC and PMD. If the UE subscribers pseudonym can be mapped or decrypted to the corresponding verinym in the standalone PMD. The Lid interface shall conform to the protocol as specified in (reference to be added) and the procedures defined in
clause 9 of this specification.
Via the LCS Identity Request, the H-GMLC can request the PMD to retrieve the verinym of the subscriber.
The following attribute is identified for the LCS Identity Request:
The PMD sends the LCS Identity Response to the H-GMLC as a result of the LCS Identity Request by the H-GMLC.
The following attribute is identified for the LCS Identity Response information flow:
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Target UE identity, (one or both of MSISDN and IMSI);
Dh is the interface between LIMS-IWF and SLF. The purpose of this interface is to retrieve the address of the correct HSS serving the user. Dh is an optional interface.
Sh is the interface between LIMS-IWF and HSS. The purpose of this interface is to retrieve the user's MSISDN.
Ml is the interface between the E-CSCF and LRF. For details, refer to
TS 23.167.
SLg is the interface that is used by the GMLC to convey a location request to the MME currently serving a particular target UE whose location was requested. The interface is also used by the MME to return location results to the GMLC.
SLs is the interface between the MME and the E-SMLC. This interface is used to convey location requests from the MME to the E-SMLC and to convey corresponding location reports back from the E-SMLC to the MME.
It is also used for tunnelling core network measurement requests from the E-SMLC to the RAN, using RAN specified protocols transparent to the MME as described in
TS 36.305.
SLh is the Diameter based interface between the HSS and the GMLC as described in
TS 29.173.
SLm is the interface between the E-SMLC and the LMU. This interface allows the E-SMLC to exchange measurement information with the LMU for the purpose of UTDOA positioning as described in
TS 36.305.
Lgd is the interface that is used by the GMLC to convey a location request to the SGSN currently serving a particular target UE whose location was requested. The interface is also used by the SGSN to return location results to the GMLC. This interface is applicable only for an SGSN supporting EPS based interfaces and protocols.