ETSI TS 129 171 V15.4.0 (2020-01)

TECHNICAL SPECIFICATION
Digital cellular telecommunications system (Phase 2+) (GSM);
Universal Mobile Telecommunications System (UMTS);
LTE;
Location Services (LCS);
LCS Application Protocol (LCS-AP)
between the Mobile Management Entity (MME)
and Evolved Serving Mobile Location Centre (E-SMLC);
SLs interface
(3GPP TS 29.171 version 15.4.0 Release 15)

3GPP TS 29.171 version 15.4.0 Release 15 1 ETSI TS 129 171 V15.4.0 (2020-01)

Reference
RTS/TSGC-0429171vf40
Keywords
GSM,LTE,UMTS
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3GPP TS 29.171 version 15.4.0 Release 15 2 ETSI TS 129 171 V15.4.0 (2020-01)
Intellectual Property Rights
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Modal verbs terminology
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3GPP TS 29.171 version 15.4.0 Release 15 3 ETSI TS 129 171 V15.4.0 (2020-01)
Contents
Intellectual Property Rights . 2
Legal Notice . 2
Modal verbs terminology . 2
Foreword . 6
1 Scope . 7
2 References . 7
3 Definitions and abbreviations . 8
3.1 Definitions . 8
3.2 Abbreviations . 8
4 Functional Overview . 8
4.1 General . 8
5 LCS-AP Message Transport . 9
5.1 General . 9
5.2 Protocol Layering . 9
5.3 Usage of SCTP Associations . 10
6 LCS-AP Procedures . 10
6.1 General . 10
6.2 Procedures Applicable to LCS-AP . 10
6.2.1 Location Service Request . 10
6.2.1.1 General . 10
6.2.1.2 Successful Operation . 10
6.2.1.3 Unsuccessful Operation . 12
6.2.2 Location Information Exchange . 12
6.2.2.1 Connection Oriented Information Transfer . 12
6.2.2.1.1 General . 12
6.2.2.1.2 Successful Operation . 13
6.2.2.1.3 Abnormal Conditions . 13
6.2.2.2 Connectionless Information Transfer . 13
6.2.2.2.1 General . 13
6.2.2.2.2 Successful Operation . 14
6.2.2.2.3 Unsuccessful Operation . 14
6.2.2.2.4 Abnormal Conditions . 14
6.2.3 Ciphering Keys Delivery . 15
6.2.3.1 General . 15
6.2.3.2 Successful Operation . 15
6.2.3.3 Unsuccessful Operation . 15
6.3 Exception Procedures . 15
6.3.1 Location Abort . 15
6.3.1.1 General . 15
6.3.1.2 Normal Operation . 16
6.3.1.3 Abnormal Conditions . 16
6.3.2 Reset . 16
6.3.2.1 General . 16
6.3.2.2 Normal Operation . 16
6.3.2.3 Abnormal Conditions . 17
6.4 Error Handling . 17
6.4.1 Abnormal Conditions . 17
6.4.2 Overload . 17
7 LCS-AP Messages and Message Formats . 18
7.1 General . 18
7.2 Message Formats . 18
7.3 LCS-AP Messages . 18
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7.3.1 LCS-AP Location Request message . 18
7.3.2 LCS-AP Location Response message . 19
7.3.3 LCS-AP Location Abort Request message . 20
7.3.4 LCS-AP Connection Oriented Information message . 20
7.3.5 LCS-AP Connectionless Information message . 20
7.3.6 LCS-AP Reset Request message . 21
7.3.7 LCS-AP Reset Acknowledge message . 21
7.3.8 LCS-AP Ciphering Key Data message . 21
7.3.9 LCS-AP Ciphering Key Data Result message . 21
7.4 Information Elements . 22
7.4.1 General . 22
7.4.2 Message Type . 22
7.4.3 Location Type . 22
7.4.4 E-CGI . 22
7.4.5 LCS Client Type . 23
7.4.6 LCS Priority . 23
7.4.7 LCS QoS . 23
7.4.8 UE Positioning Capability . 24
7.4.9 Include Velocity . 24
7.4.10 IMSI . 24
7.4.11 IMEI. 25
7.4.12 Geographic Area . 26
7.4.13 Positioning Data . 28
7.4.14 Velocity Estimate . 32
7.4.15 Accuracy Fulfilment Indicator . 32
7.4.16 LCS Cause . 33
7.4.17 Payload Type . 34
7.4.18 APDU . 34
7.4.19 Network Element . 34
7.4.20 Return Error Request . 34
7.4.21 Return Error Cause . 34
7.4.22 Altitude and direction . 35
7.4.23 Geographical Coordinates . 35
7.4.24 Uncertainty Ellipse . 36
7.4.25 Horizontal Speed and Bearing . 36
7.4.26 Vertical Velocity . 36
7.4.27 PLMN Identity . 37
7.4.28 Correlation ID . 37
7.4.29 eNB ID . 38
7.4.30 LCS Service Type ID . 38
7.4.31 Cell Portion ID . 38
7.4.32 Civic Address. 38
7.4.33 Barometric Pressure . 39
7.4.34 RAT Type . 39
7.4.35 Coverage Level . 39
7.4.36 Ciphering Data . 39
7.4.37 Ciphering Data Ack . 40
7.4.38 Ciphering Data Error Report . 40
7.4.39 Ciphering Data Set . 40
7.4.40 Ciphering Data Error Report Contents. 44
7.4.41 High Accuracy Geographical Coordinates . 44
7.4.42 High Accuracy Uncertainty Ellipse . 45
7.4.43 High Accuracy Altitude . 45
7.5 Message and information element abstract syntax . 45
7.5.1 General . 45
7.5.2 Usage of protocol extension mechanism for non-standard use . 46
7.5.3 Elementary procedure definitions . 46
7.5.4 PDU definitions . 48
7.5.5 Information element definitions . 53
7.5.6 Common definitions . 61
7.5.7 Constant definitions . 62
7.5.8 Container Definitions . 63
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7.5.9 Message transfer syntax . 64
7.6 Handling of unknown, unforeseen and erroneous protocol data . 65
8 LCS-AP Timers . 65
8.1 General . 65
8.2 Timers of LCS-AP. 65
Annex A (informative): Change history . 66
History . 67

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Foreword
rd
This Technical Specification has been produced by the 3 Generation Partnership Project (3GPP).
The contents of the present document are subject to continuing work within the TSG and may change following formal
TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an
identifying change of release date and an increase in version number as follows:
Version x.y.z
where:
x the first digit:
1 presented to TSG for information;
2 presented to TSG for approval;
3 or greater indicates TSG approved document under change control.
y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections,
updates, etc.
z the third digit is incremented when editorial only changes have been incorporated in the document.
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1 Scope
The present document specifies the procedures and information coding for LCS Application Protocol (LCS-AP) that is
needed to support the location services in E-UTRAN. The LCS-AP message set is applicable to the SLs interface
between the E-SMLC and the MME. LCS-AP is developed in accordance to the general principles stated in 3GPP TS
23.271 [3].
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.
[1] 3GPP TR 21.905: "Vocabulary for 3GPP Specifications".
[2] 3GPP TS 36.305: "Stage 2 functional specification of User Equipment (UE) positioning in E-
UTRAN".
[3] 3GPP TS 23.271: "Functional stage 2 description of Location Services (LCS)".
[4] IETF RFC 4960: "Stream Control Transmission Protocol".
[5] TIA/EIA/IS-J-STD-036 (2000): "Wireless Enhanced Emergency Services".
[6] 3GPP TS 23.032: "Universal Geographical Area Description (GAD)".
[7] 3GPP TS 36.413: "S1 Application Protocol (S1AP)".
[8] ITU-T Recommendation X.680 (07/2002): "Information Technology - Abstract Syntax Notation
One (ASN.1): Specification of basic notation".
[9] ITU-T Recommendation X.681 (07/2002): "Information Technology - Abstract Syntax Notation
One (ASN.1): Information object specification".
[10] 3GPP TS 22.071: "Location Services (LCS); Service Description; Stage1".
[11] 3GPP TS 23.003: "Numbering, addressing and identification".
[12] ITU-T Recommendation X.691 (07/2002): "Information Technology - ASN.1 encoding rules -
Specification of Packed Encoding Rules (PER)".
[13] IETF RFC 4119: "A Presence-based GEOPRIV Location Object Format".
[14] IETF RFC 5139: "Revised Civic Location Format for Presence Information Data Format Location
Object".
[15] IETF RFC 6848: "Specifying Civic Address Extensions in the Presence Information Data Format
Location Object (PIDF-LO)".
[16] IETF RFC 5905: "Network Time Protocol Version 4: Protocol and Algorithms Specification".
[17] 3GPP TS 24.301: "Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage
3".
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3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the terms and definitions given in TR 21.905 [1] and the following apply. A
term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905 [1].
Elementary Procedure: LCS-AP protocol consists of Elementary Procedures (EPs). An LCS-AP Elementary
Procedure is a unit of interaction between the MME and the E-SMLC. An EP consists of an initiating message and
possibly a response message. Two kinds of EPs are used:
- Class 1: Elementary Procedures with response (success or failure),
- Class 2: Elementary Procedures without response.

3.2 Abbreviations
For the purposes of the present document, the abbreviations given in TR 21.905 [1] and the following apply. An
abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in
TR 21.905 [1].
CID Cell-ID (positioning method)
E-CID Enhanced Cell-ID (positioning method)
E-SMLC Enhanced Serving Mobile Location Centre
E-UTRAN Envolved Universal Terrestrial Radio Access Network
GNSS Global Navigation Satellite System
GPS Global Positioning System
LCS LoCation Services
LCS-AP LCS Application Protocol
LPP LTE Positioning Protocol
LPPa LTE Positioning Protocol Annex
LTE Long Term Evolution
MBS Metropolitan Beacon System
MO-LR Mobile Originated Location Request
MT-LR Mobile Terminated Location Request
NI-LR Network Induced Location Request
MME Mobility Management Entity
OTDOA Observed Time Difference Of Arrival
PDU Protocol Data Unit
SCTP Stream Control Transmission Protocol
SET SUPL Enabled Terminal
SLP SUPL Location Platform
SUPL Secure User Plane Location
TA Timing Advanced
UE User Equipment
U-TDOA Uplink Time Difference Of Arrival

4 Functional Overview
4.1 General
Figure 4.1-1 below shows the architecture applicable to the positioning of a UE with E-UTRAN access. The SLs
interface is used to convey LCS-AP messages and parameters between the MME to the E-SMLC. It is also used for
tunnelling LTE Positioning Protocols (LPP between the E-SMLC and the target UE, LPPa between the E-SMLC and
the eNB), which are transparent to the MME as described in 3GPP TS 36.305 [2].
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E-SMLC
SLs
S1
UE
Serving
MME
eNB
LTE-Uu
S1
Neighbor
eNB
Figure 4.1-1 Positioning Interfaces in E-UTRAN

5 LCS-AP Message Transport
5.1 General
The LCS-AP is a logical interface between the MME and the E-SMLC. This clause specifies the standards for signaling
transport to be used across LCS-AP.
5.2 Protocol Layering
Figure 5.2-1 below shows the protocol layering used to support the transfer of LCS-AP PDUs between an E-SMLC and
a MME. The LTE Positioning Protocols (LPP and LPPa) can be carried in LCS-AP messages which are transparent to
the MME.
LPP/
LPPa
Relay
NAS
LCS-AP
LCS-AP
S1-AP
SCTP SCTP SCTP
IP IP IP
L2 L2 L2
L1 L1 L1
SLs
MME E-SMLC
Figure 5.2-1 Protocol Layering for LCS-AP
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5.3 Usage of SCTP Associations
SCTP (see IETF RFC 4960 [4]) shall be supported as the transport layer of LCS-AP messages.
Semi-permanent SCTP associations shall be established between MME and E-SMLC, i.e. the SCTP associations shall
remain up under normal circumstances.
Local multi-homing should be supported. Remote multi-homing shall be supported.
Multiple local SCTP endpoints may be supported. Multiple remote SCTP endpoints shall be supported. When multiple
local or remote SCTP endpoints are configured, several simultaneous SCTP associations shall be supported between
MME and E-SMLC.
The MME shall establish the SCTP association. Since under normal operation there should always be an SCTP
association established between an MME and an E-SMLC, if the E-SMLC needs to initiate a message towards an MME
it shall do so over an existing SCTP association already established with that MME.
When an entity detects that an SCTP association has been lost, all resources for transactions open on that association
shall be released.
The registered port number for LCS-AP is 9082. The registered payload protocol identifier for LCS-AP is 29.
6 LCS-AP Procedures
6.1 General
The LCS-AP interface can be divided into the following procedures:
- Location service request procedure
- Location information exchange procedure
The E-UTRAN positioning capabilities are intended to be forward compatible to other access types and other position
methods, in an effort to reduce the amount of additional positioning support needed in the future.
6.2 Procedures Applicable to LCS-AP
6.2.1 Location Service Request
6.2.1.1 General
The purpose of the location service request procedure is to obtain the location estimate for a target UE in E-UTRAN.
6.2.1.2 Successful Operation
MME
E-SMLC
LOCATION REQUEST
LOCATION RESPONSE
Figure 6.2.1.2-1 Location Service Request Procedure, Successful Operation
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The initiator (MME) of the location service request procedure sends a LCS-AP Location Request message to the E-
SMLC associated with the current or last known serving cell for the target UE and starts the timer T3x01. The message
contains the following mandatory (M), conditional (C) and optional (O) information, where conditional parameters are
required if available.
- Correlation ID (M)
- Location Type (M)
- Cell Identifier (M)
- LCS Client Type (C)
- LCS Priority (C)
- LCS Service Type ID (C)
- LCS QoS (C)
- UE Positioning Capability (O)
- Include Velocity (O)
- IMSI of target UE (O)
- IMEI of target UE (O)
- APDU (O)
- RAT Type (O)
- Coverage Level (O)
The Correlation ID is assigned by the MME and enables association of the location response with the location request
when more than one location service request procedure is ongoing for the UE with the same E-SMLC.
The Location Type IE indicates the type of Location Information being requested. The following types are supported:
- Current geographic location estimate
- Location assistance data for the target UE
- Last known location estimate
If the location estimate is requested, the E-SMLC performs positioning procedure on the target UE using a particular
position method or a combination of more than one positioning method based on the UE capability. If UE capability is
unknown, the E-SMLC may request UE position capability through LPP as defined in 3GPP TS 36.305 [2].
Alternatively, if assistance data was requested, the E-SMLC may provide positioning assistance data to the UE. The E-
SMLC may invoke the following LCS-AP procedures to get assistance data:
- Connection Oriented Information Transfer
- Connectionless Information Transfer
Otherwise, if a last known location estimate is requested, the E-SMLC obtains a geographic location estimate using
only the information provided in the LCS-AP Location Request message. The E-SMLC shall not attempt to obtain
location information for the target UE from either the E-UTRAN or the target UE (e.g. because the UE may not be
currently reachable).
If a location estimate or a last known location estimate was requested and was subsequently obtained, the E-SMLC shall
return a LCS-AP Location Response to the initiator of the location request using the same SCTP association as the
location request. This message contains the following mandatory (M), conditional (C) and optional parameters (O).
- Correlation ID (M)
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- Location Estimate (M).
- Accuracy Fulfilment Indicator (O).
- Velocity estimate (C).
- Positioning Data (C).
- E-UTRAN Cell Identifier (O).
- Cell Portion ID (O).
- Civic Address (O).
- Barometric Pressure (O).
If assistance data was instead requested for an UE and the E-SMLC was able successfully to transfer this to the UE, the
E-SMLC shall return a LCS-AP Location Response to the initiator of the location request (MME). This message shall
contain no parameters. The absence of a LCS Cause parameter in this case implies that the transfer was successful.
If the MME receives the LCS-AP Location Response for corresponding request message, the MME shall stop the timer
T3x01.
6.2.1.3 Unsuccessful Operation
If the E-SMLC is unable to obtain any of the location information requested or if requested LCS assistance data could
not be transferred, the E-SMLC shall return a LCS-AP Location Response to the initiator of the Location Request
carrying the following parameters:
- Correlation ID (M)
- LCS Cause (M)
- Positioning Data (O)
The E-SMLC shall use the same SCTP association for the Location Response as was used for the request.
If the MME receives the LCS-AP Location Response for corresponding request message, the MME shall stop the timer
T3x01.
On the expiry of the timer T3x01, the MME shall abort the procedure, release any resources allocated for this location
request procedure and notify the node that triggered the Location Request about the error.
6.2.2 Location Information Exchange
6.2.2.1 Connection Oriented Information Transfer
6.2.2.1.1 General
The Connection Oriented Information transfer procedure enables two-way transfer of LPP and LPPa messages between
an E-SMLC and a MME. The procedure is only valid while a location request procedure for the target UE is ongoing.
This procedure makes use of the same SCTP association as the location request procedure for the particular target UE.
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6.2.2.1.2 Successful Operation

Endpoint A
Endpoint B
CONNECTION ORIENTED INFORMATION

Figure 6.2.2.1.2-1 Connection Oriented Information, Successful Operation
The initiator of the procedure (E-SMLC or MME) with a LPP or LPPa message to transfer concerning a particular
target UE sends a LCS-AP Connection Oriented Information message to a recipient carrying the following parameters:
- Correlation ID (M)
- Payload Type (M)
- APDU (M);
The Correlation ID in this message is the Correlation ID used for the Location Request. It shall be present for a message
transfer from the E-SMLC to the MME and for a message transfer from the MME to the E-SMLC.
The Payload Type shall be present to indicate the type of the APDU. The supported information types are LPP and
LPPa.
The APDU shall contain an LPP APDU when communicating between the E-SMLC and the target UE or an LPPa
APDU when communicating between the E-SMLC and serving eNB. The MME shall forward this to the serving eNB
for the target UE.
If the intended recipient is the E-SMLC for a target UE, the message is terminated in the E-SMLC. The E-SMLC shall
then perform interpretation of the APDU.
6.2.2.1.3 Abnormal Conditions
At an intermediate entity, if a received LCS-AP Connection Oriented Information message contains unrecognized
information or if the message cannot be sent on, the message shall be discarded.
6.2.2.2 Connectionless Information Transfer
6.2.2.2.1 General
The Connectionless Information transfer procedure enables two-way transfer of LPPa messages between an E-SMLC
and a MME when there is no existing signalling connection association. This procedure can be used to query eNBs for
the information not related to a UE connection, such as Timing information on the eNB.
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6.2.2.2.2 Successful Operation

Endpoint A
Endpoint B
CONNECTIONLESS INFORMATION
CONNECTIONLESS INFORMATION
Figure 6.2.2.2.2-1 Connectionless Information Procedure, Successful Operation
The initiator of the procedure (either E-SMLC or MME) sends a LCS-AP Connectionless Information message to a
recipient carrying the following parameters:
- Source Entity (M)
- Destination Entity (M)
- APDU (M)
- Return Error Request (O)
The source entity identifies the sender. The recipient entity identifies the final destination. The APDU contains a LPPa
APDU to be transferred. The Return Error Request may be included to request notification in the event of unsuccessful
transfer and indicate the type of notification needed. If the recipient entity is not the final destination, the recipient shall
transfer the LCS-AP Connectionless Information message to either the final destination or an intermediate entity
capable of forward it to the final destination.
6.2.2.2.3 Unsuccessful Operation
If the message cannot be transferred by an intermediate entity or destination entity and the Return Error Request is not
included, the message shall be discarded. If the Return Error Request is included, the intermediate or destination entity
shall, depending on the Return Error Request type, send a LCS-AP Connectionless Information message to, or towards,
the original source containing the following parameters:
- Source Entity (M)
- Destination Entity (M)
- APDU (M)
- Return Error Cause (M)
The Source entity shall indicate the Destination Entity in the original received message. The Destination Entity shall
indicate the Source Entity in the original message. The Return Error cause shall indicate the reason for unsuccessful
transfer. The APDU shall contain any originally received APDU.
If a received LCS-AP Connectionless Information message containing a Return Error Cause cannot be transferred by an
intermediate entity, it shall be discarded with no return error message.
6.2.2.2.4 Abnormal Conditions
At an intermediate entity, if a received LCS-AP Connectionless Information message contains unrecognized or invalid
information, the message shall be discarded.
At the recipient entity, if a received LCS-AP Connectionless Information message contains invalid or unrecognized
information as defined for LCS-AP, the message shall be discarded.
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6.2.3 Ciphering Keys Delivery
6.2.3.1 General
The purpose of the ciphering keys delivery procedure is to enable the E-SMLC to send ciphering keys for broadcast
assistance data to the MME so that the MME can then distribute the ciphering keys to suitably subscribed UEs.
6.2.3.2 Successful Operation
MME
E-SMLC
CIPHERING KEY DATA
CIPHERING KEY DATA RESULT
Figure 6.2.3.2-1 Ciphering Keys Delivery Procedure, Successful Operation
The initiator (E-SMLC) of the ciphering keys delivery procedure sends a Ciphering Key Data message to the MME and
starts the timer T3x03. The message contains the following mandatory (M) information:
- Ciphering Data (M):
If the MME is able to successfully store all ciphering data sets included in the Ciphering Key Data message, the MME
sends a Ciphering Key Data Result message. The message contains the following mandatory (M) information:
- Ciphering Data Ack (M)
If the E-SMLC receives the Ciphering Key Data Result message, the E-SMLC shall stop the timer T3x03.
6.2.3.3 Unsuccessful Operation
If the MME is unable to successfully store one or more ciphering data sets included in the Ciphering Key Data message,
the MME shall return a Ciphering Key Data Result message carrying the following mandatory (M) information:
- Ciphering Data Error Report (M)
If the E-SMLC receives the Ciphering Key Data Result message message, the E-SMLC shall stop the timer T3x03.
On the expiry of the timer T3x03, the E-SMLC shall abort the procedure and release any resources allocated for this
ciphering keys delivery procedure.
6.3 Exception Procedures
6.3.1 Location Abort
6.3.1.1 General
The purpose of the Location Abort procedure is to cancel an ongoing positioning attempt or the request for assistance
data. This message can be sen
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