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Content for  TS 25.305  Word version:  16.0.0

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1  ScopeWord‑p. 8

The present document specifies the stage 2 of the UE Positioning function of UTRAN, which provides the mechanisms to support the calculation of the geographical position of a UE. UE position knowledge can be used for example in support of Radio Resource Management functions, location-based services for operators, subscribers and third party service providers. The purpose of this stage 2 specification is to define the UTRAN UE Positioning architecture, functional entities and operations to support positioning methods. This description is confined to the UTRAN Access Stratum. It does not define nor describe how the results of the UE position calculation can be utilised in the Core Network (e.g. LCS) or in UTRAN (e.g. RRM).
UE Positioning 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 specification covers the UTRAN positioning methods, state descriptions, and message flows to support UE Positioning.

2  References

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.

2.1  Normative references

[1]  Void.
TR 21.905: "Vocabulary for 3GPP Specifications".
[3]  Void.
TS 23.271: "Location Services (LCS); (Functional description) - Stage 2".
TS 22.071: "Location Services (LCS); Service description, Stage 1".
TS 22.100: "UMTS phase 1".
TS 22.101: "Services aspects; Service principles".
TS 22.105: "Services and Service Capabilities".
TS 22.115: "Services aspects; Charging and Billing".
TS 22.121: "Services aspects; The Virtual Home Environment; Stage 1".
TS 23.032: "Universal Geographical Area Description (GAD)".
TS 23.110: "UMTS Access Stratum; Services and Functions".
TS 23.171: "Functional stage 2 description of location services in UMTS".
TS 25.214: "Physical layer procedures (FDD)"
TS 25.215: "Physical layer - Measurements (FDD)".
TS 25.225: "Physical layer - Measurements (TDD)".
TS 25.306: "UE Radio Access Capabilities".
TS 25.331: "Radio Resource Control (RRC); protocol specification".
TS 25.413: "UTRAN Iu interface RANAP signalling".
TS 25.423: "UTRAN Iur interface RNSAP signalling".
TS 25.430: "UTRAN Iub interface: General aspects and Principles".
TS 25.433: "UTRAN Iub interface NBAP signalling".
ICD-GPS-200: "Navstar GPS Space Segment/Navigation User Interfaces".
RTCM-SC104: "RTCM Recommended Standards for Differential GNSS Service" (v.2.2.)
TS 24.008: "Mobile radio interface layer 3 specification, Core Network Protocols - Stage 3".
TS 25.224: "Physical layer procedures (TDD)".
TS 25.453: "UTRAN Iupc interface PCAP signalling".
TS 25.412: "Iu interface signalling transport".
BDS-SIS-ICD-2.0: "BeiDou Navigation Satellite System Signal In Space Interface Control Document Open Service Signal (Version 2.0), December 2013".
IEEE 802.11 Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications.
Bluetooth Special Interest Group: "Bluetooth Core Specification v4.2", December 2014.
ATIS-0500027: "Recommendations for Establishing Wide Scale Indoor Location Performance," May 2015.

2.2  Informative referencesWord‑p. 9

Third generation (3G) mobile communication system; Technical study report on the location services and technologies, ARIB ST9 December 1998.
The North American Interest Group of the GSM MoU ASSOCIATION: Location Based Services, Service Requirements Document of the Services Working Group.

3  Definitions and abbreviations

3.1  Definitions

For the purposes of the present document, the terms and definitions given in [7] and some of the terms and definitions in Annex A apply.

3.2  Abbreviations

For the purposes of the present document, the following abbreviations apply.
3rd Generation MSC
3rd Generation SGSN
Assisted Global Navigation Satellite System
Assisted Global Positioning Systems
Association of Radio Industries and Business
BeiDou Navigation Satellite System
Customised Application For Mobile Network Enhanced Logic
Core Network
Controlling RNC
Differential Global Navigation Satellite System
Differential Global Positioning Systems
Drift RNC
European Geostationary Navigation Overlay Service
Enhanced Observed Time Difference
GPS Aided Geo Augmented Navigation
Geometric Dilution of Precision
GLObal'naya NAvigatsionnaya Sputnikovaya Sistema (Engl.: Global Navigation Satellite System)
Gateway MLC
Global Navigation Satellite System
General Packet Radio System
Global Positioning System
Home Location Register
HandOver Word
Integrity Monitor
Idle Period Downlink
Location Based Services
Location Client Control Function
Location Client Function
LoCation Services
Location Information Relay Function
Location Measurement Unit
Location System Assistance Data Function
Location System Control Function
Location System Control Function in SAS
Location System Operation Function
Metropolitan Beacon System
Mobile Location Centre
Multimedia Messaging Service
Multi-functional Satellite Augmentation System
Mobile services Switching Centre
Non Access Stratum
Observed Time Difference Of Arrival
Positioning Calculation Application Part
Position Calculation Function
Public Land Mobile Network
Pseudo-Range Correction
Positioning Radio Co-ordination Function
Positioning Radio Communication Function
Pseudo-Range Rate Correction
Positioning Radio Resource Management
Positioning Signal Measurement Function
Quality of Service
Quasi-Zenith Satellite System
Radio Access Network
Radio Access Network Application Part
Radio Network Controller
Radio Resource Management
Real Time Difference
Round Trip Time
Service Area Identifier
Stand-Alone SMLC
Satellite Based Augmentation System
Serving GPRS Support Node
Subscriber Identity Module
Short Message Service
Serving RNC
Site Selection Diversity Transmit
Terrestrial Beacon System
Time Of Arrival
Time Of Week
UMTS-(LCS functional block)
internal UTRAN Location Client Function
UTRAN Location System Control Function
UTRAN Location System Operations Function
UTRAN Location Information Relay Function
UTRAN Location System Control Function in SAS
UTRAN Location System Assistance Data Function
UTRAN Position Radio Co-ordination Function
UTRAN Position Calculation Function
UTRAN Position Signal Measurement Function
UTRAN Position Radio Resource Management
UTRAN Position Related Communication Function
User Differential Range Error
User Equipment
Universal Mobile Telecommunication System
User Service Identity Module
Universal Time Coordinates
Uplink - Time Difference Of Arrival
Universal Terrestrial Radio Access Network
Wide Area Augmentation System
Wideband Code Division Multiple Access
Wireless Local Area Network

4  Main concepts and requirementsWord‑p. 11

The stage 1 LCS description providing an overall service description and the core requirements for the LCS at the service level is given in [5]. The stage 2 LCS description providing a system functional model for the whole system, the LCS system architecture, state descriptions and message flows are described in [13].
By measuring radio signals the capability to determine the geographic position and velocity of the UE shall be provided. The position information may be requested by and reported to a client (application) associated with the UE, or by a client within or attached to the CN. The position information may also be utilised internally by UTRAN, for example, for location-assisted handover or to support other features such as home location billing. The position information shall be reported in standard formats, such as those for cell based or geographical co-ordinates, together with the estimated errors (uncertainty) of the position and velocity of the UE and, if available, the positioning method (or the list of the methods) used to obtain the position estimate. Restrictions on the geographic shape encoded within the 'position information' parameter may exist for certain LCS client types. The SRNC shall comply with any shape restrictions defined in GSM/UMTS and, in a particular country, with any shape restrictions defined for a specific LCS client type in relevant national standards. For example, in the US, national interim standard TIA/EIA/IS-J-STD-036 restricts the geographic shape for an emergency services LCS client to minimally either an "ellipsoid point" or an "ellipsoid point with uncertainty circle and confidence" as defined in [11].
It shall be possible for the majority of the UE (active or inactive) within a network to use the feature without compromising the radio transmission or signalling capabilities of the UTRAN.
The uncertainty of the position measurement shall be network implementation dependent at the choice of the network operator. The uncertainty may vary between networks as well as from one area within a network to another. The uncertainty may be hundreds of metres in some areas and only a few metres in others. In the event that the position measurement is also a UE-assisted process, the uncertainty may also depend on the capabilities of the UE. In some jurisdictions, there is a regulatory requirement for location service accuracy that is part of an emergency service. Further details of the accuracy requirements can be found in [5].
The uncertainty of the position information is dependent on the method used, the position of the UE within the coverage area and the activity of the UE. Several design options of the UTRAN system (e.g. size of cell, adaptive antenna technique, path loss estimation, timing accuracy, Node B surveys) shall allow the network operator to choose a suitable and cost effective UE Positioning method for their market.
There are many different possible uses for the positioning information. The positioning functions may be used internally by the UTRAN, by value-added network services, by the UE itself or through the network, and by "third party" services. The feature may also be used by an emergency service (which may be mandated or "value-added"), but the location service is not exclusively for emergencies.
The UTRAN is a new radio system design without a pre-existing deployment of UE operating according to the radio interface. This freedom from legacy equipment enables the location service feature design to make use of appropriate techniques to provide the most accurate results. The technique must also be a cost-effective total solution, must allow evolution to meet evolving service requirements and be able to take advantage of advances in technology over the lifetime of UTRAN deployments.

4.1  AssumptionsWord‑p. 12

As a basis for the operation of UE Positioning in UTRAN the following assumptions apply:
  • both TDD and FDD will be supported;
  • the provision of the UE Positioning function in UTRAN is optional through support of the specified method(s) in Node B, the SAS, and the RNC;
  • UE Positioning is applicable to any target UE whether or not the UE supports LCS, but with restrictions on use of certain positioning method depending on UE capability as defined in [17];
  • The SMLC may be either a stand-alone network element (SAS) or an internal function of the RNC;
  • UE Positioning information is transported between RNCs via the Iur interface independent of whether the SMLC is a stand-alone network element (SAS) or an internal function of the RNC;
  • the positioning information may be used for internal system operations to improve system performance;
  • different types of LMU are defined, e.g. a standalone LMU and/or LMU integrated in Node B;
  • the UE Positioning architecture and functions shall include the option to accommodate several techniques of measurement and processing to ensure evolution to follow changing service requirements and to take advantage of advancing technology;
  • the RNC manages the overall coordination and scheduling of resources required to perform positioning of a UE. It may also calculate the final position and velocity estimate and accuracy.

4.2  UE Positioning Methods

The UTRAN may utilise one or more positioning methods in order to determine the position of an UE.
Positioning the UE involves two main steps:
  • signal measurements; and
  • Position estimate and optional velocity computation based on the measurements.
The signal measurements may be made by the UE, the Node B or an LMU. The basic signals measured are typically the UTRA radio transmissions, however, some methods may make use of other transmissions such as general radio navigation signals.
The positioning function should not be limited to a single method or measurement. That is, it should be capable of utilising other standard methods and measurements, as are available and appropriate, to meet the required service needs of the location service client. This additional information could consist of readily available UTRAN measurements such as RTT in FDD or Rx Timing deviation measurement and knowledge of the UE timing advance, in TDD.
The position estimate computation may be made by the UE or by the UTRAN (i.e. SRNC or SAS).

4.3  Standard UE Positioning MethodsWord‑p. 13

The standard positioning methods supported within UTRAN are:
  • cell ID based method;
  • OTDOA method that may be assisted by network configurable idle periods;
  • network-assisted GNSS methods;
  • U-TDOA;
  • Barometric Pressure method;
  • WLAN method;
  • Bluetooth method;
  • Terrestrial Beacon System methods.

4.3.1  Cell ID and Enhanced Cell ID Based Methods

In the cell ID based (i.e. cell coverage) method, the position of an UE is estimated with the knowledge of its serving Node B. The information about the serving Node B and cell may be obtained by paging, locating area update, cell update, URA update, or routing area update.
The cell coverage based positioning information can be indicated as the Cell Identity of the used cell, the Service Area Identity or as the geographical co-ordinates of a position related to the serving cell. The position information shall include a QoS estimate (e.g. regarding achieved accuracy) and, if available, the positioning method (or the list of the methods) used to obtain the position estimate.
When geographical co-ordinates are used as the position information, the estimated position of the UE can be a fixed geographical position within the serving cell (e.g. position of the serving Node B), the geographical centre of the serving cell coverage area, or some other fixed position within the cell coverage area. Enhanced Cell ID methods use additional UE and/or UTRAN radio resource related measurements.
The operation of the cell ID and Enhanced Cell ID based positioning methods are described in clause 8.

4.3.2  OTDOA-IPDL Method with network configurable idle periods

The OTDOA-IPDL method involves measurements made by the UE and LMU of the UTRAN frame timing (e.g. SFN-SFN observed time difference). These measures are then sent to the SRNC and, in networks which include an SAS, may be forwarded to the SAS. Depending on the configuration of the network, the position of the UE is calculated in the SRNC or in the SAS.
The simplest case of OTDOA-IPDL is without idle periods. In this case the method can be referred to as simply OTDOA.
The Node B may provide idle periods in the downlink, in order to potentially improve the hearability of neighbouring Node Bs. The support of these idle periods in the UE is optional. Support of idle periods in the UE means that its OTDOA performance will improve when idle periods are available.
Alternatively, the UE may perform the calculation of the position using measurements and assistance data.
The detailed description of the OTDOA-IPDL positioning method and its operation are described in clause 9.

4.3.3  Network-assisted GNSS MethodsWord‑p. 14

These methods make use of UEs, which are equipped with radio receivers capable of receiving GNSS signals.
Examples of GNSS include GPS, Modernized GPS, Galileo, GLONASS, Satellite Based Augmentation Systems (SBAS), Quasi Zenith Satellite System (QZSS), and BeiDou Navigation Satellite System (BDS).
In this concept, different GNSS (e.g. GPS, Galileo, etc.) can be used separately or in combination to perform the location of a UE.
The operation of the network-assisted GNSS methods is described in clause 13.

4.3.4  U-TDOA Method |R7|

The U-TDOA positioning method is based on network measurements of the Time Of Arrival (TOA) of a known signal sent from the UE and received at four or more LMUs. The method requires LMUs in the geographic vicinity of the UE to be positioned to accurately measure the TOA of the bursts. Since the geographical coordinates of the measurement units are known, the UE position can be calculated via hyperbolic trilateration. This method will work with existing UE without any modification.
The operation of the U-TDOA location method is described in clause 12.

4.3.5  Barometric Pressure positioning |R13|

The barometric pressure method makes use of barometric pressure sensors for identifying height information and to determine the vertical component of the position of the UE. This method should be combined with other positioning methods to determine the 3D position of the UE.
The operation of the Barometric Pressure positioning method is described in clause 14.

4.3.6  WLAN positioning |R13|

The WLAN positioning method makes use of the WLAN measurements (AP identifiers and optionally other measurements) and databases to determine the location of the UE. The UE measures received signals from WLAN [32] access points. Using the measurements results and a references database, the location of the UE is calculated.
The operation of the WLAN positioning method is described in clause 15.

4.3.7  Bluetooth positioning |R13|

The Bluetooth positioning method makes use of the Bluetooth measurements (Bluetooth beacon identifiers and optionally other measurements) and databases to determine the location of the UE. The UE measures received signals from Bluetooth [33] beacons. Using the measurements results and a references database, the location of the UE is calculated.
The operation of the Bluetooth positioning method is described in clause 16.

4.3.8  TBS positioning |R13|

A Terrestrial Beacon System (TBS) consists of a network of ground-based transmitters, broadcasting signals only for positioning purposes. The current type of TBS positioning signals are the MBS (Metropolitan Beacon System) signals [34].
The operation of the TBS positioning method is described in clause 17.

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