Content for TS 36.455 Word version: 16.1.0

3.1 Definitions 3.2 Symbols 3.3 Abbreviations 4.1 Procedure specification principles 4.2 Forwards and backwards compatibility 4.3 Specification notations 5.1 LPPa procedure modules 5.2 Parallel transactions
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1 Scope Word‑p. 7

The present document specifies the control plane radio network layer signalling procedures between eNB and E-SMLC. LPPa supports the concerned functions by signalling procedures defined in this document. LPPa is developed in accordance with the general principles stated in TS 36.401.

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]

TR 21.905: "Vocabulary for 3GPP Specifications".

[2]

TS 36.401: "Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Architecture Description".

[3]

TS 36.413: "Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 Application Protocol (S1AP)".

[4]

ITU-T Recommendation X.691 (2002-07): "Information technology - ASN.1 encoding rules - Specification of Packed Encoding Rules (PER)".

[5]

TS 36.104: "Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Base Station (BS) radio transmission and reception".

[6]

TS 36.211: "Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Physical Channels and Modulation".

[7]

TS 23.032: "Technical Specification Group Services and System Aspects; Universal Geographical Area Description (GAD)".

[8]

TS 36.133: "Evolved Universal Terrestrial Radio Access (E-UTRA); Requirements for support of radio resource management".

[9]

TR 25.921: (version.7.0.0) "Guidelines and principles for protocol description and error handling".

[10]

TS 36.331: "Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification".

[11]

IEEE Std 802.11™-2012: IEEE Standard for Information technology - Telecommunications and information exchange between systems - Local and metropolitan area network.

[12]

TS 36.213: "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures".

[13]

TS 36.355: "Evolved Universal Terrestrial Radio Access (E-UTRA); LTE Positioning Protocol (LPP)".

3 Definitions, symbols and abbreviations Word‑p. 8

3.1 Definitions

For the purposes of the present document, the terms and definitions given in TR 21.905 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.

Elementary Procedure:

LPPa protocol consists of Elementary Procedures (EPs). An LPPa Elementary Procedure is a unit of interaction between the eNB 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.

Cell Portion:

A geographical part of a cell. A cell portion is semi-static, and identical for both the UL and the DL. Within a cell, a cell portion is uniquely identified by its Cell Portion ID.

Transmission Point (TP):

A set of geographically co-located transmit antennas for one cell, part of one cell or one PRS-only TP. Transmission Points can include base station (eNB) antennas, remote radio heads, a remote antenna of a base station, an antenna of a PRS-only TP, etc. One cell can be formed by one or multiple transmission points. For a homogeneous deployment, each transmission point may correspond to one cell.

PRS-only TP:

A TP which only transmits PRS signals for PRS-based TBS positioning and is not associated with a cell.

3.2 Symbols

For the purposes of the present document, the following symbols apply:

3.3 Abbreviations

For the purposes of the present document, the abbreviations given in TR 21.905 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.

BSSID

Basic Service Set IDentifier

CID

Cell-ID (positioning method)

Downlink

E-CID

Enhanced Cell-ID (positioning method)

eNB

E-UTRAN NodeB

Elementary Procedure

EPC

Evolved Packet Core

E-SMLC

Evolved Serving Mobile Location Centre

E-UTRAN

Evolved UTRAN

GNSS

Global Navigation Satellite System

HESSID

Homogeneous Extended Service Set IDentifier

Information Element

LCS

LoCation Services

LPP

LTE Positioning Protocol

LPPa

LTE Positioning Protocol Annex

MME

Mobility Management Entity

Network

OTDOA

Observed Time Difference of Arrival

RSSI

Received Signal Strength Indicator

S1AP

S1 Application Protocol

SBAS

Satellite-based Augmentation System

SRS

Sounding Reference Signal

SSID

Service Set IDentifier

Transmission Point

User Equipment

Uplink

UTDOA

Uplink Time Difference of Arrival

WLAN

Wireless Local Area Network

4 General Word‑p. 9

4.1 Procedure specification principles

The principle for specifying the procedure logic is to specify the functional behaviour of the terminating eNB exactly and completely. Any rule that specifies the behaviour of the originating eNB shall be possible to be verified with information that is visible within the system.

The following specification principles have been applied for the procedure text in clause 8:

The procedure text discriminates between:
1. Functionality which "shall" be executed
  The procedure text indicates that the receiving node "shall" perform a certain function Y under a certain condition. If the receiving node supports procedure X but cannot perform functionality Y requested in the initiating message of a Class 1 EP, the receiving node shall respond with the message used to report unsuccessful outcome for this procedure, containing an appropriate cause value.
2. Functionality which "shall, if supported" be executed
  The procedure text indicates that the receiving node "shall, if supported," perform a certain function Y under a certain condition. If the receiving node supports procedure X, but does not support functionality Y, the receiving node shall proceed with the execution of the EP, possibly informing the requesting node about the not supported functionality.
Any required inclusion of an optional IE in a response message is explicitly indicated in the procedure text. If the procedure text does not explicitly indicate that an optional IE shall be included in a response message, the optional IE shall not be included. For requirements on including Criticality Diagnostics IE, see section 10.

4.2 Forwards and backwards compatibility

The forwards and backwards compatibility of the protocol is assured by a mechanism where all current and future messages, and IEs or groups of related IEs, include ID and criticality fields that are coded in a standard format that will not be changed in the future. These parts can always be decoded regardless of the standard version.

4.3 Specification notations

For the purposes of the present document, the following notations apply:

Procedure

When referring to an elementary procedure in the specification the Procedure Name is written with the first letters in each word in upper case characters followed by the word "procedure", e.g. Handover Preparation procedure.

Message

When referring to a message in the specification the MESSAGE NAME is written with all letters in upper case characters followed by the word "message", e.g. ERROR INDICATION message.

When referring to an information element (IE) in the specification the Information Element Name is written with the first letters in each word in upper case characters and all letters in Italic font followed by the abbreviation "IE", e.g. Cause IE.

Value of an IE

When referring to the value of an information element (IE) in the specification the "Value" is written as it is specified in sub clause 9.2 enclosed by quotation marks, e.g. "Value".

5 LPPa services Word‑p. 10

The present clause describes the services an eNB offers to the E-SMLC.

5.1 LPPa procedure modules

The procedures are divided into two modules as follows:

LPPa Location Information Transfer Procedures;
LPPa Management Procedures;

The LPPa Location Information Transfer Procedures module contains procedures used to handle the transfer of positioning related information between eNB and E-SMLC.

The Management Procedures module contains procedures that are not related specifically to positioning, i.e. error handling.

5.2 Parallel transactions

Unless explicitly indicated in the procedure specification, at any instance in time one protocol peer may have more than one ongoing LPPa procedure.

6 Services expected from lower layer

Within E-UTRAN, LPPa protocol uses the services provided by the S1AP protocol. An LPPa message is carried inside an S1AP message.

S1AP signalling is described in TS 36.413.

7 Functions of LPPa

The LPPa protocol provides the following functions:

E-CID Location Information Transfer. This function allows the eNB to exchange location information with the E-SMLC for the purpose of E-CID positioning.
OTDOA Information Transfer. This function allows the eNB to exchange information with the E-SMLC for the purpose of OTDOA positioning.
UTDOA Information Transfer. This function allows the eNB to exchange information with the E-SMLC for the purpose of supporting UTDOA.
Assistance Information Transfer. This function allows the E-SMLC to exchange information with the eNB for the purpose of assistance information broadcasting.
Reporting of General Error Situations. This function allows reporting of general error situations, for which function specific error messages have not been defined.

The mapping between the above functions and LPPa EPs is shown in the table below.

Table 7-1: Mapping between LPPa functions and LPPa EPs

Function	Elementary Procedure(s)
E-CID Location Information Transfer	a) E-CID Measurement Initiation b) E-CID Measurement Failure Indication c) E-CID Measurement Report d) E-CID Measurement Termination
OTDOA Information Transfer	OTDOA Information Exchange
UTDOA Information Transfer	a) UTDOA Information Exchange b) UTDOA Information Update
Assistance Information Transfer	a) Assistance Information Control b) Assistance Information Feedback
Reporting of General Error Situations	Error Indication