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Content for  TS 23.271  Word version:  17.0.0

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1  Scopep. 10

The present document specifies the stage 2 of the LoCation Services (LCS) feature in UMTS, GSM and EPS (for E-UTRAN), which provides the mechanisms to support mobile location services for operators, subscribers and third party service providers.
Location Services in 5GC are restricted to regulatory services and are specified in TS 23.501 and TS 23.502 in this release of the specification. The architecture and signalling procedures in NG-RAN are defined in TS 38.305.
The present document replaces the specifications TS 23.171 (Release 1999) and the system and core network parts of GSM 03.71 (Release 1999). TS 43.059 replaces the radio access network parts of GSM 03.71 (Release 1999).
Location Services may be considered as a network provided enabling technology consisting of standardised service capabilities, which enable the provision of location applications. The application(s) may be service provider specific. The description of the numerous and varied possible location applications which are enabled by this technology are outside the scope of the present document. However, clarifying examples of how the functionality being described may be used to provide specific location services may be included.
This stage 2 service description covers the LCS system functional model for the whole system, the LCS system architecture, state descriptions, message flows, etc.
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2  Referencesp. 10

The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
  • References are either specific (identified by date of publication, edition number, version number, etc.) or non specific.
  • For a specific reference, subsequent revisions do not apply.
  • For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.
[1]
TS 25.305: "Stage 2 functional specification of UE positioning in UTRAN".
[2]  Void.
[3]
TR 21.905: "Vocabulary for 3GPP Specifications".
[4]
TS 22.071: "Technical Specification Group Systems Aspects; Location Services (LCS); Stage 1".
[5]  Void.
[6]  Void.
[7]  Void.
[8]
TS 22.101: "Service principles".
[9]  Void.
[10]  Void.
[11]
TS 23.032: "Universal Geographical Area Description (GAD)".
[12]  Void.
[13]  Void.
[14]
TS 25.413: "UTRAN Iu Interface RANAP signalling".
[15]
TS 23.060: "General Packet Radio Service (GPRS); Service description; Stage 2".
[16]
TS 43.059: "Functional Stage 2 description of Location Services in GERAN".
[17]
TS 23.003: "Numbering, addressing and identification".
[18]
TS 29.002: "Mobile Application Part (MAP) Specification".
[19]  Void.
[20]
TS 23.002: "Network architecture".
[21]
TS 23.078: "Customised Applications for Mobile network Enhanced Logic (CAMEL) - stage 2".
[22]
TS 23.011: "Technical realization of Supplementary Services".
[23]
TS 23.007: "Restoration procedures".
[24]
TS 24.008: "Mobile Radio Interface - Layer 3 MM/CC Specification".
[25]
TS 25.331: "RRC protocol specification".
[26]
TS 23.127: "Virtual Home Environment/Open Service Access".
[27]
TS 29.198-01: "Open Service Access (OSA); Application Programming Interface (API); Part 1; Overview".
[28]
TS 29.198-02: "Open Service Access (OSA); Application Programming Interface (API); Part 2; Common Data".
[29]
TS 29.198-03: "Open Service Access (OSA); Application Programming Interface (API); Part 3; Framework".
[30]
TS 29.198-06: "Open Service Access (OSA); Application Programming Interface (API); Part 6: Mobility".
[31]
OMA MLP TS: "Mobile Location Protocol", [http://www.openmobilealliance.org].
[32]
ANSI J-STD-036B: "Enhanced Wireless 9-1-1 Phase 2".
[33]
RFC 2396:  "Uniform Resource Identifiers".
[34]
RFC 3261:  "SIP: Session Initiation Protocol".
[35]
TS 23.228: "IP multimedia subsystem (IMS)".
[35a]
ITU Recommendation E.164: "The international public telecommunication numbering plan".
[35b]
TS 22.060: "General Packet Radio Service (GPRS); Service Description, Stage 1".
[36]
OMA RLP TS: "Roaming Location Protocol", [http://www.openmobilealliance.org].
[36a]
TS 23.167: "IP Multimedia Subsystem (IMS) emergency sessions".
[37]
TS 31.111: "Universal Subscriber Identity Module (USIM) Application Toolkit (USAT)".
[38]
Open Mobile Alliance, OMA AD SUPL: "Secure User Plane Location Architecture", (http://www.openmobilealliance.org).
[39]
Open Mobile Alliance, OMA TS ULP: "User Plane Location Protocol", (http://www.openmobilealliance.org).
[40]
RFC 4119:  "A Presence-based GEOPRIV Location Object Format".
[41]
TS 23.401: "General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access".
[42]
TS 36.305: "Stage 2 functional specification of UE positioning in E-UTRAN".
[43]
TS 23.216: "Single Radio Voice Call Continuity (SRVCC); Stage 2".
[44]
TS 23.402: "Architecture enhancements for non-3GPP accesses".
[45]
TS 29.173: "Location Services (LCS); Diameter-based SLh interface for Control Plane LCS".
[46]
TS 29.171: "LCS Application Protocol (LCS-AP) between MME and E-SMLC; SLs Interface".
[47]
TS 36.355: "Evolved Universal Terrestrial Radio Access (E-UTRA); LTE Positioning Protocol (LPP)".
[48]
TS 36.455: "Evolved Universal Terrestrial Radio Access (E-UTRA); LTE Positioning Protocol Annex (LPPa)".
[49]
TS 36.413: "Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 Application Protocol (S1AP)".
[50]
TS 36.300: "Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall Description; Stage 2".
[51]
TS 29.272: "Evolved Packet System (EPS);Mobility Management Entity (MME) and Serving GPRS Support Node (SGSN) related interfaces based on Diameter protocol".
[52]
TS 23.234: "3GPP system to Wireless Local Area Network (WLAN) interworking".
[53]
TS 23.237: "IP Multimedia Subsystem (IMS) Service Continuity; Stage 2".
[54]
TS 23.501: " System Architecture for the 5G System; Stage 2".
[55]
TS 23.502: "Procedures for the 5G System; Stage 2".
[56]
TS 38.305: "Stage 2 functional specification of User Equipment (UE) positioning in NG-RAN".
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3  Definitions, symbols and abbreviationsp. 12

3.1  Definitionsp. 12

For the purposes of the present document, the following terms and definitions apply:
CAMEL:
CAMEL is a network functionality, which provides the mechanisms of Intelligent Network to a mobile user.
Call Related:
any LCS related operation which is associated with an established call in CS domain and a session via an active PDP context in PS domain.
Codeword:
access code, which is used by a Requestor or LCS Client in order to gain acceptance of a location request for a Target UE. The codeword is part of the privacy information that may be registered by a Target UE user.
Current Location:
after a location attempt has successfully delivered a location estimate and its associated time stamp, the location estimate and time stamp is referred to as the "current location" at that point in time.
Deferred location request:
location request where the location response (responses) is (are) required after a specific event has occurred. The event may or may not occur immediately.
Global Navigation Satellite System:
Global Navigation Satellite System (GNSS) consists of three functional elements: Space Segment (satellites), User Segment (receivers), and Control Segment (maintenance etc.). The GNSS receiver calculates its own position based on the received time differences for several satellites. GNSS include Global Positioning System (GPS) and GALILEO.
Immediate location request:
location request where a single location response only is required immediately
Initial Location:
in the context of an originating emergency call the location estimate and the associated time stamp at the commencement of the call set-up is referred to as "initial location".
Last Known Location:
current location estimate and its associated time stamp for Target UE stored in the LCS Server is referred to as the "last known location" and until replaced by a later location estimate and a new time stamp is referred to as the "last known location".
LCS (LoCation Services):
LCS is a service concept in system (e.g. GSM or UMTS) standardization. LCS specifies all the necessary network elements and entities, their functionalities, interfaces, as well as communication messages, due to implement the positioning functionality in a cellular network. Note that LCS does not specify any location based (value added) services except locating of emergency calls.
LCS Client:
software and/or hardware entity that interacts with a LCS Server for the purpose of obtaining location information for one or more Mobile Stations. LCS Clients subscribe to LCS in order to obtain location information. LCS Clients may or may not interact with human users. The LCS Client is responsible for formatting and presenting data and managing the user interface (dialogue). The LCS Client may reside in the Mobile Station (UE).
LCS Client Access barring list:
optional list of MSISDNs per LCS Client where the LCS Client is not allowed to locate any MSISDN therein.
LCS Client Subscription Profile:
collection of subscription attributes of LCS related parameters that have been agreed for a contractual period of time between the LCS client and the service provider.
LCS Feature:
capability of a PLMN to support LCS Client/server interactions for locating Target UEs.
LCS QoS Class:
The QoS class determines the degree of adherence to the quality of service information as required by the source of a location request.
LCS Server:
software and/or hardware entity offering LCS capabilities. The LCS Server accepts requests, services requests, and sends back responses to the received requests. The LCS server consists of LCS components, which are distributed to one or more PLMN and/or service provider.
LDR reference number:
the identity which is assigned and maintained by the H-GMLC and circulated between the LCS Client, R-GMLC, H-GMLC, V-GMLC, MSC/SGSN and UE. With the identity of the UE, the LDR reference number can unique identify a Location Deferred Request. Notes: UE is involved only when the event type of the deferred request is "change of area" or "periodic location". In addition, in a Periodical Immediate/deferred LCS Service Request, the LDR reference number is exclusive.
Linear Distance Threshold:
a straight line distance used for a deferred location request for the motion event. The linear distance threshold is defined by the LCS client and triggers a motion event when a UE moves by more than this distance from a previous location. The linear distance threshold is equivalent to a change of area event for leaving an area where the area is a circle with the linear distance threshold as a radius and centred on the previous location.
Local Information:
information related to a given location, or general information, which is made available in a given location.
Local Service:
service, which can be exclusively provided in the current serving network by a Value added Service Provider.
Location (Based) Application:
location application is an application software processing location information or utilizing it in some way. The location information can be input by a user or detected by network or UE. Navigation is one location application example.
Location Based Service (LBS):
service provided either by teleoperator or a 3rd party service provider that utilizes the available location information of the terminal. Location Application offers the User Interface for the service. LBS is either a pull or a push type of service (see Location Dependent Services and Location Independent Services). In ETSI/GSM documentation of SoLSA, LBS is called "Location Related Service". ETSI and/or 3GPP -wide terminology harmonization is expected here.
Location Dependent Service:
service provided either by teleoperator or a 3rd party service provider that is available (pull type) or is activated (push type) when the user arrives to a certain area. It doesn't require any subscription in advance, but the push type activation shall be confirmed by the user. The offered service itself can be any kind of service (e.g. a public Xerox machine or the discount list in a store).
Location Estimate:
geographic location of an UE and/or a valid Mobile Equipment (ME), expressed in latitude and longitude data. The Location Estimate shall be represented in a well-defined universal format. Translation from this universal format to another geographic location system may be supported, although the details are considered outside the scope of the primitive services. The location estimate may include the velocity of the UE.
Location Identifier:
information about the current location of the UE in the network. Location is indicated in network terms, for example using the global cell id in cellular networks, line-id in fixed broadband networks, the (MAC) address of the WLAN AP or Location Object as defined by RFC 4119, (OMA-Location also uses this term, but OMA so far defines the Location Identifier only for cellular access).
Location Independent Service:
service provided either by teleoperator or a 3rd party service provider that is available and therefore can be activated anywhere in the network coverage. It is activated by the user's request or by other user's activated service, and therefore it requires a subscription in advance (pull type). The offered service itself can be any kind of service (e.g. MMS, SWDL, or LBS!).
Location Retrieval Function (LRF):
this functional entity handles the retrieval of location information for the UE including, where required, interim location information, initial location information and updated location information. The LRF may interact with a separate RDF or contain an integrated RDF in order to obtain routing information. The LRF may interact with a separate GMLC or contain an integrated GMLC in order to obtain location information. The LRF may interact with or contain other types of location server functions in order to obtain location information.
Maximum reporting time:
maximum allowed time between successive area/motion event reports. Expiration of the maximum reporting time triggers a report, the UE indicates expiration of the maximum reporting time as the trigger event.
Minimum reporting time:
minimum allowed time between successive area/motion event reports. The UE defers any event report if needed until minimum reporting time expires.
Mobile Assisted positioning:
any mobile centric positioning method (e.g. IPDL-OTDOA, E-OTD, GPS) in which the UE provides position measurements to the network for computation of a location estimate by the network. The network may provide assistance data to the UE to enable position measurements and/or improve measurement performance.
Mobile Based positioning:
any mobile centric positioning method (e.g. IPDL-OTDOA, E-OTD, GPS) in which the UE performs both position measurements and computation of a location estimate and where assistance data useful or essential to one or both of these functions is provided to the UE by the network. Position methods where an UE performs measurements and location computation without network assistance data are not considered within this category.
Mobile Station:
mobile station (MS) consists of Mobile or User Equipment (ME or UE) with a valid SIM or USIM attached. The abbreviation "UE" in this specification refers both to MS and User Equipment, see below.
MO-LR Short Circuit:
use of an MO-LR based procedure to provide a location estimate directly from the UE to the serving SGSN or MSC using a Mobile Based positioning method (e.g. GPS) according to the requested LCS QoS and that is not obtained or verified by the RAN.
Network-based positioning:
a positioning method (i.e. UTDOA) in which multiple network nodes (e.g. LMUs) perform position radio measurements based on UL transmissions from a mobile terminal to provide them to an E SMLC for computation of a location estimate for the mobile terminal.
Non-dialable call back number:
In case of a SIM-less emergency call, or a non-registered (U)SIM emergency call, a non-dialable callback number shall be used to identify the target UE. The format and structure of the non-dialable callback number is according to national or regional regulations.
Non-registered (U)SIM emergency call:
The emergency call where the U(SIM) has not been authenticated and have not been registered in the VLR. Examples of such cases could be emergency call from a blocked (U)SIM due to mistyped PIN, or when the UE is in "enter PIN" mode, or the emergency call is performed in another network with no roaming agreement with the home PLMN. Any IMSI retrieved from such a (U)SIM cannot be trusted and so cannot be used to identify the calling party.
PLMN Access barring list:
optional list of MSISDN per PLMN where any LCS Client is not allowed to locate any MSISDN therein except for certain exceptional cases.
Positioning (/location detecting):
positioning is a functionality, which detects a geographical location and optionally, velocity (of e.g. a mobile terminal).
Positioning method (/locating method):
method or technical solution, which is used to get an estimate of the target mobile's geographical location. For example positioning methods based on radio cell coverage, GPS or Assisted GPS methods, which are based on the Time-Of-Arrival (TOA) algorithm, and UTDOA, OTDOA or E-OTD methods, which are based on the Time-Difference-Of-Arrival (TDOA) algorithm. The positioning methods are further described in E-UTRAN Stage 2, TS 36.305, UTRAN Stage 2, TS 25.305 and GERAN Stage 2, TS 43.059.
Predefined area:
geographical area, which is not related to cell or radio coverage. The mobile may take special action when it recognises it has entered or left a predefined area.
Privacy Class:
list of LCS Clients defined within a privacy exception class to which permission may be granted to locate the target UE. The permission shall be granted either on activation by the target UE or permanently for a contractual period of time agreed between the target UE and the service provider.
Privacy Exception List:
list consisting of various types of privacy classes (i.e. operator related, personal etc.). Certain types of classes may require agreement between the service provider and the target UE.
Privacy Profile Register, PPR:
The PPR stores privacy information of the target mobile. The PPR also executes privacy checks and sends the privacy check results to other network elements using the Lpp interface. PPR may be a standalone network entity or the PPR functionality may be integrated in H-GMLC.
Prohibited area:
area where the mobile must not activate its transmitter. The Prohibited area may be a Predefined area described above or related to radio cell(s).
Pseudo-external identity:
The pseudo-external identity is not the identity of real external LCS client but the identity, which is used for notifying the result of the enhanced privacy check. The pseudo-external identity shall keep the compatibility with pre Rel-6 privacy mechanisms, which does not understand privacy check result made by H-GMLC/PPR. Each operator defines its own the pseudo-external identities.
Pseudonym:
A fictitious identity, which may be used to conceal the true identity (i.e. MSISDN and IMSI) of a target UE from the requestor and the LCS client.
Pseudonym mediation device:
Functionality that verifies pseudonyms to verinyms.
Request id:
identity which is used to identify the correspondence of a location request to multiple responses when the Response method is ASYNC. Each receiving GMLC (R-GMLC or V-GMLC or H-GMLC) allocates and maintains the Request id to identify each ASYNC location request, and includes it in the responses to the source entity of the location request (i.e. LCS client or GMLC).
Requestor:
the originating entity which has requested the location of the target UE from the LCS client.
Requestor Identity:
This identifier is identifying the Requestor and can be e.g. MSISDN or logical name.
Response method:
method how a GMLC, which receives a location request message from another entity (i.e. LCS client or GMLC), responds to the location request. There are two methods, synchronous (SYNC) and asynchronous (ASYNC). When the requesting entity wishes multiple responses (either about one or several target UE's location) to a single location request the procedure is ASYNC and when the requesting entity wishes a single response the procedure is SYNC. The source entity of the location request (i.e. LCS client or GMLC) can choose a preferred method and informs the method to the receiving GMLC. However, the selection of the method used is made by the receiving GMLC and when the ASYNC method is selected the Request id is notified to the source entity. The receiving GMLC can turn a SYNC request into an ASYNC procedure, e.g. in an overload situation, and the source entity (i.e. LCS client or GMLC) should be able to receive multiple responses even though the request was SYNC.
Routing Determination Function (RDF):
The functional entity, which may be integrated in a Location Server (e.g. GMLC) or in an LRF, provides the proper PSAP destination address to the E-CSCF for routing the emergency request. It can interact with a location functional entity (e.g. GMLC) to manage ESQK allocation and management, and deliver location information to the PSAP.
Service Area Identifier (SAI):
information, which is used to identify an area consisting of one or more cells belonging to the same Location Area, see TS 25.413. Such an area is called a Service Area and can be used for indicating the location of a UE to the CN. For this specification, only a Service Area that is defined to be applicable to the PS and CS domains shall be used.
Service coverage:
a list of country codes where an LCS client offers its location services. Country code in this context means E.164 country code for a geographic area [35a].
Service Type:
attribute of specific location based service provided by the LCS client, as defined in TS 22.071.
Serving cell identity:
the Cell Global Identification (CGI), see TS 23.003, of the cell currently used by the target UE, e.g. for an emergency call in A-mode.
SIM-less emergency call:
The emergency call that is originated from a UE, which does not have a SIM or USIM.
Subscription Profile:
profile detailing the subscription to various types of privacy classes.
Target area:
geographical area which is used for change of area type deferred location request. The target area is defined by the LCS client and is expressed as geographical area using a shape defined in TS 23.032, as a geographical area using local coordinate system, as an E.164 country code for a geographic area [35a], as a PLMN identity or as a geopolitical name of the area (e.g. London).
Target UE:
UE being positioned.
User Equipment:
term 'User Equipment', or 'UE', as defined in TR 21.905. UE in this specification may also refer to a Mobile Equipment or User Equipment used for emergency calls, that do not have valid SIM or USIM.
Velocity:
The speed of a UE and the direction in which it is travelling, encoded as defined in TS 23.032. Velocity may be defined as either 2-D (horizontal) velocity or 3-D (horizontal and vertical) velocity. Both 2-D and 3-D velocity may be reported either with or without uncertainty.
Verinym:
True identity, i.e. MSISDN or IMSI, of the target UE.
Further UMTS related definitions are given in TS 22.101.
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3.2  Symbolsp. 16

For the purposes of the present document, the following symbols apply:
Dh
Interface between LIMS-IWF and SLF
Gb
Interface between 2G-SGSN and BSS
Gs
Interface between MSC and SGSN
La
Interface between GMLC and AAA
Lc
Interface between gateway MLC and gsmSCF (CAMEL interface)
Le
Interface between External User and MLC (external interface)
Lg
Interface between Gateway MLC - VMSC, GMLC - MSC Server, GMLC - SGSN (gateway MLC interface)
Lgd
Interface between GMLC and SGSN (Diameter based)
Lh
Interface between Gateway MLC and HLR (MAP based)
Lid
Interface between GMLC and PMD.
Lpp
Interface between GMLC(H-GMLC) and PPR entity.
Lr
Interface between Gateway MLCs
Ml
Interface between the E-CSCF and LRF
Sh
Interface between LIMS-IWF and HSS
SLg
Interface between GMLC and MME
SLh
Interface between GMLC and HSS (Diameter based)
SLs
Interface between MME and E-SMLC
Um
GERAN Air Interface
Uu
UTRAN Air Interface
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3.3  Abbreviationsp. 16

For the purposes of the present document, the following abbreviations apply:
2G-
Second Generation
3G-
Third Generation
A-GNSS
Assisted Global Navigation Satellite System
AAA
Authentication, Authorization, Accounting
AC
Admission Control
AI
Application Interface (prefix to interface class method)
ANM
Answer Message (ISUP)
APN
Access Point Name
APN-NI
APN Network Identifier
ARIB
Association of Radio Industries and Business
ATD
Absolute Time Difference
BCCH
Broadcast Control Channel
BER
Bit Error Rate
BSSID
Basic Service Set Identifier
BSS
Base Station Subsystem
BTS
Base Transceiver Station
CAMEL
Customised Application For Mobile Network Enhanced Logic
CAP
CAMEL Application Part
CM
Connection Management
CN
Core Network
CSCF
Call Service Control Function
CSE
Camel Service Environment
DL
Downlink
DNS
Domain Name System
DRNC
Drift RNC
E-CSCF
Emergency CSCF
E-OTD
Enhanced Observed Time Difference
E-SLP
Emergency SUPL Location Platform
E-SMLC
Evolved Serving Mobile Location Centre
E-STN-DR
Emergency Session Transfer Number for DRVCC
FER
Frame Error Rate
GERAN
GSM EDGE Radio Access Network
GGSN
Gateway GPRS Support Node
GMLC
Gateway MLC
GNSS
Global Navigation Satellite System
GPRS
General Packet Radio Service
GPS
Global Positioning System
HE
Home Environment
H-GMLC
Home-GMLC
H-LIMS-IWF
Home-LIMS-IWF
HSS
Home Subscriber Server
HLR
Home Location Register
HPLMN
Home Public Land Mobile Network
IMEI
International Mobile Equipment Identity
IMS
IP Multimedia Subsystem
IMSI
International Mobile Subscriber Identity
IP
Internet Protocol
IPDL
Idle Period Downlink
IW-MT-LR
Mobile Terminated Location Request for an I-WLAN
I-WLAN
Interworking WLAN
LA
Location Application
LAF
Location Application Function
LBS
Location Based Services
LCAF
Location Client Authorization Function
LCCF
Location Client Control Function
LCCTF
Location Client Co-ordinate Transformation Function
LCF
Location Client Function
LCZTF
Location Client Zone Transformation Function
LCS
LoCation Services
LDR
Location Deferred Request
LIMS-IWF
Location IMS - Interworking Function
LIR
Location Immediate Request
LMU
Location Measurement Unit
LRF
Location Retrieval Function
LSAF
Location Subscriber Authorization Function
LSBcF
Location System Broadcast Function
LSBF
Location System Billing Function
LSCF
Location System Control Function
LSCTF
Location System Co-ordinate Transformation Function
LSOF
Location System Operation Function
LSPF
Location Subscriber Privacy Function
LSTF
Location Subscriber Translation Function
MAP
Mobile Application Part
ME
Mobile Equipment
MExE
Mobile Execution Environment
MGCF
Media Gateway Control Function
MLC
Mobile Location Centre
MLP
Mobile Location Protocol
MM
Mobility Management
MO-LR
Mobile Originated Location Request
MS
Mobile Station
MSC
Mobile services Switching Centre
MSISDN
Mobile Station Integrated Services Data Network
MT-LR
Mobile Terminated Location Request
NA-ESRD
North American Emergency Service Routing Digits
NA-ESRK
North American Emergency Service Routing Key
NI-LR
Network Induced Location Request
NPLI
Network Provided Location Information
OMA
Open Mobile Alliance
OSA
Open Service Architecture
OTDOA
Observed Time Difference Of Arrival
PC
Power Control
PCF
Power Calculation Function
PLMN
Public Land Mobile Network
PMD
Pseudonym mediation device functionality
POI
Privacy Override Indicator
PPR
Privacy Profile Register
PRCF
Positioning Radio Co-ordination Function
PRRM
Positioning Radio Resource Management
PSAP
Public Safety Answering Point
PSE
Personal Service Environment
PSM
Power Saving Mode
PSMF
Positioning Signal Measurement Function
PSTN
Public Switched Telephone Network
QoS
Quality of Service
RA
Routing Area
RACH
Random Access Channel
RAN
Radio Access Network
RANAP
Radio Access Network Application Part
R-GMLC
Requesting-GMLC
RDF
Routing Determination Function
RIS
Radio Interface Synchronization
R-LIMS-IWF
Requesting-LIMS-IWF
RLP
Roaming Location Protocol
RNC
Radio Network Controller
RRM
Radio Resource Management
RTD
Real Time Difference
RTT
Round Trip Time
SAI
Service Area Identifier
SAT
SIM Application Tool-Kit
SCCP
Signalling Connection Control Part
SCS
Service Capability Server
SGSN
Serving GPRS Support Node
SI
Service Interface (prefix to interface class method)
SIM
Subscriber Identity Module
SIP
Session Initiation Protocol
SIP-URI
SIP Uniform Resource Identifier
SIR
Signal Interference Ratio
SLF
Subscription Locator Function
SLP
SUPL Location Platform
SLPP
Subscriber LCS Privacy Profile
SMLC
Serving Mobile Location Centre
SMS
Short Message Service
SP
Service Point
SRNC
Serving RNC
SS7
Signalling System No 7
SUPL
Secure User Plane Location
TA
Timing Advance
TAU
Tracking Area Update
TEL-URL
Telephone Uniform Resource Locator
TMSI
Temporary Mobile Subscriber Identity
TOA
Time Of Arrival
TTTP
Transfer To Third Party
UDT
SCCP Unitdata message
UE
User Equipment
UL
Uplink
UMTS
Universal Mobile Telecommunication System
UPLI
UE Provided Location Information
USIM
Universal Subscriber Identity Module
UTDOA
Uplink Time Difference of Arrival
UTRAN
Universal Terrestrial Radio Access Network
VASP
Value Added Service Provider
V-GMLC
Visited -GMLC
VHE
Virtual Home Environment
WCDMA
Wideband Code Division Multiple Access
Further related abbreviations are given in TR 21.905.
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4  Main conceptsp. 20

A general description of location services and service requirements are given in the specification TS 22.071. The positioning of the UE is a service provided by the Access Network. In particular, all Access Networks (e.g. UTRAN, GERAN, E-UTRAN), that facilitate determination of the locations of User Equipments, shall be able to exchange location information with the core network as defined in the present document (when connected to a Core Network). Optionally, location information may also be communicated between GMLCs, located in the same or a different PLMN, via the specified GMLC to GMLC interface.
By making use of the radio signals the capability to determine the (geographic) location of the user equipment (UE) or mobile station (UE) shall be provided. The location information may be requested by and reported to a client (application) associated with the UE, or by a client within or attached to the Core Network. The location information may also be utilised internally in the system; for example, for location assisted handover or to support other features such as home location billing. The location information request may ask for the velocity of the UE as part of the positioning information. The position information shall be reported in standard, i.e. geographical co-ordinates, together with the time-of-day and the estimated errors (uncertainty) of the location of the UE according to specification TS 23.032. The velocity of the UE may be optionally returned in a format specified in TS 23.032.
It shall be possible for the majority of the UE (active or idle) within a network to use the feature without compromising the radio transmission or signalling capabilities of the GSM/UMTS/EPS networks.
The UE and the network may support a number of different positioning methods and the UE may support or not support privacy invocation request and response. The UE informs the core network and radio access network about its LCS capabilities in this respect as defined in TS 24.008 and TS 25.331.
The uncertainty of the location measurement shall be network design (implementation) dependent at the choice of the network operator, this is further described in TS 25.305, TS 36.305, and TS 43.059.
There are many different possible uses for the location information. The positioning feature may be used internally by the GSM/UMTS/EPS network (or attached networks), by value-added network services, by the UE itself or through the network, and by "third party" services. The positioning feature may also be used by an emergency service (which may be mandated or "value-added"), but the position service is not exclusively for emergencies.
There are regulatory requirements to support anonymity in location services in some countries.
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4.1  Assumptionsp. 20

As a basis for the further development work on LCS in GSM, UMTS and EPS the following assumptions apply:
  • positioning methods are Access Network specific, although commonalties should be encouraged between Access Networks;
  • commercial location services are only applicable for an UE with a valid SIM or USIM;
  • the provision of the location services in the Access Network is optional through support of the specified method(s);
  • the provision of location services is optional in MSC, SGSN and MME;
  • LCS is applicable to any target UE whether or not the UE supports LCS, but with restrictions on choice of positioning method or notification of a location request to the UE user when LCS or individual positioning methods, respectively, are not supported by the UE;
  • LCS shall be applicable for both circuit switched and packet switched services;
  • the location information may be used for internal system operations to improve system performance;
  • it shall be possible to accommodate future techniques of measurement and processing to take advantage of advancing technology so as to meet new service requirements;
  • it may be necessary to support LCS signalling between separate access networks via the core network. For UMTS, the Iur interface should be used if available;
  • Provide positioning procedures through the circuit-switched domain are also applicable to GPRS UEs which are GPRS and IMSI attached;
  • it shall be possible for more than one LCS Client to request and obtain the location of the same target UE at the same time.
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4.2  Location Services Categoriesp. 21

Generally there are four categories of usage of the location service. These are the Commercial LCS, the Internal LCS, the Emergency LCS and the Lawful Intercept LCS. The definition of these services and their categories is outside the scope of the present document.
  • The Commercial LCS (or Value Added Services) will typically be associated with an application that provides a value-added service to the subscriber of the service, through knowledge of the UE location (and optionally, velocity) and if available, and at the operator's discretion, the positioning method used to obtain the location estimate. This may be, for example, a directory of restaurants in the local area of the UE, together with directions for reaching them from the current UE location.
  • The Internal LCS will typically be developed to make use of the location information of the UE for Access Network internal operations. This may include; for example, location assisted handover and traffic and coverage measurement. This may also include support certain O&M related tasks, supplementary services, IN related services and GSM bearer services and teleservices.
  • The Emergency LCS will typically be part of a service provided to assist subscribers who place emergency calls. In this service, the location of the UE caller and, if available, the positioning method used to obtain the location estimate is provided to the emergency service provider to assist them in their response. This service may be mandatory in some jurisdictions. In the United States, for example, this service is mandated for all mobile voice subscribers.
  • The Lawful Intercept LCS will use the location information to support various legally required or sanctioned services.
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4.3  Positioning methodsp. 21

The LCS feature utilises one or more positioning methods in order to determine the location of user equipment (UE). Determining the position of a UE involves two main steps:
  • Radio signal measurements; and
  • Position estimate computation based on the measurements.
The positioning methods for UTRAN are further described in TS 25.305.

4.3.1  Standard LCS Methods in UTRANp. 21

The specification TS 25.305 UTRAN Stage 2 specifies the locating methods to be supported:
  • cell coverage based positioning method;
  • OTDOA positioning method;
  • A-GNSS based positioning methods;
  • UTDOA positioning method;
  • Barometric pressure sensor method;
  • WLAN method;
  • Bluetooth method;
  • Terrestrial Beacon System method.
For more details on these positioning methods, refer to TS 25.305.

4.3.2  Standard LCS Methods in GERANp. 22

The specification TS 43.059 GERAN LCS Stage 2 specifies the locating methods to be supported in GERAN:
  • cell coverage based positioning method;
  • Enhanced Observed Time Difference (E-OTD) positioning method;
  • A-GNSS based positioning methods;
  • Uplink Time Difference of Arrival (UTDOA) positioning method.

4.3.3  Standard LCS Methods in E-UTRAN |R9|p. 22

Locating methods specified in TS 36.305 applicable to E-UTRAN comprise:
  • uplink and downlink cell coverage based positioning methods;
  • OTDOA positioning method;
  • A-GNSS based positioning methods;
  • UTDOA positioning method;
  • Barometric pressure sensor method;
  • WLAN method;
  • Bluetooth method;
  • Terrestrial Beacon System methods.
Hybrid positioning using multiple methods from the list of positioning methods above is also supported.
In case of the Home eNodeB, applicable locating methods may be restricted, e.g. when a Home eNodeB is connected via Home eNodeB GW.
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4.4  Types of Location Requestp. 22

4.4.1  Immediate Location Requestp. 22

Request for location where the LCS Server replies immediately to the LCS Client with the current location estimate if this could be obtained.

4.4.2  Deferred Location Requestp. 22

Request for location contingent on some current or future events where the response from the LCS Server to the LCS Client may occur some time after the request was sent.

4.4.2.1  Types of eventp. 22

a)
UE available: Any event in which the MSC/SGSN/MME has established a contact with the UE. Note, this event is considered to be applicable when the UE is temporarily unavailable due to inaction by the user, temporarily loss of radio connectivity or IMSI detach and so on. Note that IMSI detach is only applicable in the case the UE has previously been registered and information is still kept in the node. The UE Available event only requires one response and after this response, the UE Available event is concluded.
b)
Change of Area: An event where the UE enters or leaves a pre-defined geographical area or if the UE is currently within the pre-defined geographical area. Only one type of area event may be defined (i.e. entering, leaving or remaining within the area). The LCS client defines the target area as a geographical area, as an E.164 country code for a geographic area [35a], as a PLMN identity or as a geopolitical name of the area. The LCS server may translate and define the target area as the identities of one or more radio cells, location areas, routing areas, tracking areas, country code or PLMN identity. The target UE must not give the target UE user access to the area definitions and network identities. The change of area event may be reported one time only, or several times. The area event report must not be repeated more often than allowed by the LCS client. The change of area event report shall contain an indication of the event occurrence. The location estimate may be included in the report. If an area event is detected by the UE but an event report cannot be sent (e.g. because the UE cannot access the network or due to a minimum reporting interval), a report shall be sent later when possible irrespective of whether the area event still applies for the current UE location. For E-UTRAN access, area event reporting is controlled by a minimum and a maximum reporting time. The minimum reporting time defines the minimum allowed time between successive area events. The maximum reporting time defines the maximum time between successive reports. When a UE sends a report due to expiration of the maximum reporting time, the UE indicates expiration of the maximum reporting time as the trigger event. The maximum reporting time enables the LCS client, R-GMLC and H-GMLC to remain aware of continuing support by the UE for the area event (e.g. to detect if area event reporting may have been aborted due to UE power off).
c)
Periodic Location: An event where a defined periodic timer expires in the UE and activates a location report or a location request. If a periodic event is detected by the UE but an event report cannot be sent (e.g. because the UE cannot access the network temporarily), a report shall be sent later when possible and the periodic timer for the next event shall then be started. The reporting duration for periodic location shall equal the requested number of reports multiplied by the periodic interval even when reports are delayed.
d)
Motion: An event where the UE moves by more than some predefined linear distance from a previous location. The motion event may be reported one time only, or several times. The motion event report shall contain an indication of the event occurrence. A location estimate may be included in the report if requested by the LCS client. For successive motion event reports, motion is determined relative to the UE location corresponding to the immediately preceding event report (including an event report triggered by expiration of the maximum reporting time). If a motion event is detected by the UE but an event report is deferred (e.g. because the UE cannot access the network temporarily), a report shall be sent later when possible irrespective of whether the motion event still applies to the current UE location. Motion reporting is controlled by a minimum and a maximum reporting time. The minimum reporting time defines the minimum allowed time between successive event reports. The maximum reporting time defines the maximum time between successive reports. When a UE sends a report due to expiration of the maximum reporting time, the UE indicates expiration of the maximum reporting time as the trigger event. The maximum reporting time enables the LCS client, R-GMLC and H-GMLC to remain aware of continuing support by the UE for the motion event (e.g. to detect if motion event reporting may have been aborted due to UE power off).
e)
Other events are FFS.
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4.5  Concurrent Location Requests |R7|p. 23

The LCS Server is enabled to support concurrent location requests for the same target UE. The following principles apply.
  1. Under certain conditions, an entity may combine concurrent location requests by fully executing one request and using the ensuing location estimate result(s) to satisfy the other request(s) without fully executing the latter and as allowed by QoS requirements. The allowed conditions for each type of entity are defined below:
    1. An R GMLC may combine concurrent MT LR requests for the same target UE LCS Client pair.
    2. An H GMLC may combine concurrent MT LR requests for the same target UE if privacy requirements can be fully resolved by the H GMLC (e.g. no notification or verification needed for the UE for any MT LR that will not be fully executed).
    3. A V GMLC may combine concurrent MT LR and NI LR related location requests for the same target UE provided it is clear and unambiguous for any MT LR that will not be fully executed (e.g. from the contents of any MAP Provide Subscriber Location request received from the H GMLC) that no outstanding privacy related actions are required for the UE (e.g. no privacy notification and/or privacy verification interaction with the UE and no privacy subscription verification in the VLR, SGSN or MME).
    4. An MSC, MSC server, SGSN or MME may combine concurrent MT LR, MO LR and NI LR location requests once any needed privacy related actions (e.g. UE notification and verification) have been performed for each MT LR.
    5. A UE may combine concurrent MO LR requests for LCS Clients internal to or associated with the UE.
  2. Except under the conditions permitted in (1), different concurrent location requests shall be treated separately and shall not be visibly combined or made dependent on one another by any entity within the LCS Server. This means that the procedures defined here in clause 9 continue to apply to each separate location request and do not visibly impact one another.
  3. Implementation limitations are allowed whereby an entity that, either itself or in association with another entity, cannot support concurrent location requests or more than a certain number of concurrent location requests is allowed to reject or defer a new concurrent request or cancel one or more existing requests. When concurrent location requests are supported, each entity needs to ensure it correlates each location/position response with the associated request.
  4. In support of principles 1, 2 and 3, an entity (e.g. GMLC, MSC, MSC server, SGSN, MME, UE) that receives a new location request (e.g. MT LR, MO LR, NI LR) while already supporting previous location requests for the same target UE may reject the new location request, defer (i.e. queue) the new request, cancel one or more previous requests (where a procedure for cancellation has been defined), allow the new location request to proceed concurrently with and separately from the previous requests if allowed on applicable interfaces or, for the specific cases defined in principle 1, combine the new request with one or more previous requests if this will not impair or affect service support for the new request (e.g. privacy and QoS).
  5. In support of principle 4, LCS Client priority and any other relevant priority information (e.g. UE subscription preferences) should be considered. In particular, location requests associated with emergency services or lawful interception clients should be given priority over other location requests.
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