Content for TS 36.463 Word version: 16.0.0

3.1 Definitions 3.2 Abbreviations 4.1 Procedure specification principles 4.2 Forwards and backwards compatibility 4.3 Specification notations 5.1 General 5.2 XwAP procedures 5.3 Parallel transactions
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1 Scope Word‑p. 8

The present document specifies the signalling procedures of the control plane between an eNB and WLAN Termination (WT). The Xw Application Protocol (XwAP) supports the functions of Xw interface by signalling procedures defined in this document.

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 36.300: "Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2".

[3]

TS 29.281: "General Packet Radio System (GPRS) Tunnelling Protocol User Plane (GTPv1-U)".

[4]

TS 36.462: "Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and Wireless LAN (WLAN); Xw signalling support"

[5]

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

[6]

ITU-T Recommendation X.680 (07/2002): "Information technology - Abstract Syntax Notation One (ASN.1): Specification of basic notation".

[7]

ITU-T Recommendation X.681 (07/2002): "Information technology - Abstract Syntax Notation One (ASN.1): Information object specification".

[8]

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

[9]

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

[10]

Wi-Fi Alliance® Technical Committee: Hotspot 2.0 Technical Task Group Hotspot 2.0 (Release 2) Technical Specification Version 3.11.

[11]

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

[12]

TR 25.921: "Guidelines and principles for protocol description and error handling"

[13]

TS 23.203: "Numbering, addressing and identification"

[14]

TS 23.401: "General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access"

[15]

TS 36.464: "Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and Wireless LAN (WLAN); Xw data transport"

[16]

TS 29.281: "General Packet Radio System (GPRS) Tunnelling Protocol User Plane (GTPv1-U)"

[17]

TS 33.401: "3GPP System Architecture Evolution (SAE); Security architecture"

[18]

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

3 Definitions and abbreviations Word‑p. 9

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:

XwAP protocol consists of Elementary Procedures (EPs). An XwAP Elementary Procedure is a unit of interaction between an eNB and WT. 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.

eNB UE XwAP ID:

Defined in TS 36.401.

E-RAB:

Defined in TS 36.401.

LWA bearer:

Defined in TS 36.300.

LWIP-SeGW:

Defined in TS 33.401.

UE-associated signalling:

Refers to XwAP messages associated to one UE, and which use the respective UE-associated logical Xw connection.

UE-associated logical Xw connection:

The UE-associated logical Xw connection transports UE-associated signalling. The identities WT UE XwAP ID and eNB UE XwAP ID are used to identify the particular UE-associated logical Xw connection that a message relates to.

WLAN Termination:

Defined in TS 36.300.

WT UE XwAP ID:

Defined in TS 36.401.

3.2 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.

Access Category

Downlink

eNB

E-UTRAN NodeB

Elementary Procedure

EPC

Evolved Packet Core

E-RAB

E-UTRAN Radio Access Bearer

E-UTRAN

Evolved UTRAN

Information Element

IKE

Internet Key Exchange

LWA

LTE/WLAN Aggregation

LWIP

LTE/WLAN Radio Level Integration with IPsec Tunnel

LWIP-SeGW

LWIP Security GateWay

PDCP

Packet Data Convergence Protocol

RCLWI

RAN Controlled LTE-WLAN Interworking

Sequence Number

TAC

Tracking Area Code

User Equipment

Uplink

WLAN Termination

Xw UP

Xw User Plane

4 General Word‑p. 10

4.1 Procedure specification principles

The principle for specifying the procedure logic is to specify the functional behaviour of the terminating node exactly and completely. Any rule that specifies the behaviour of the originating node 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. HANDOVER REQUEST 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. E-RAB ID 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 XwAP services Word‑p. 11

5.1 General

The present clause describes the services offered between an eNB and WT.

5.2 XwAP procedures

The Xw interface XwAP procedures may be UE-associated or non UE-associated. UE-associated XwAP procedures are used to handle the configuration and modification to support LWA or LWIP for a specific UE. Non UE-associated procedures support LWA, RCLWI and/or LWIP, and are not related to a specific UE.

5.3 Parallel transactions

Unless explicitly indicated in the procedure specification, at any instance in time one protocol peer shall have a maximum of one ongoing XwAP procedure related to a certain UE.

6 Services expected from signalling transport

The signalling connection shall provide in sequence delivery of XwAP messages. XwAP shall be notified if the signalling connection breaks.

Xw signalling transport is described in TS 36.462.

7 Functions of XwAP

The XwAP protocol provides the following functions:

Setting up the Xw. This function is used to exchange the necessary data for the eNB and the WT to set up the Xw interface and implicitly perform an Xw Reset.
WT Configuration Update. This function allows updating of application level data needed for the eNB and the WT to interoperate correctly on the Xw interface.
WLAN Status Reporting. This function allows the eNB to configure reporting of load-related information from the WT.
LTE-WLAN Aggregation. This function allows the eNB to request a WT to provide radio resources for LWA operation for a certain UE while keeping responsibility for that UE.
LTE-WLAN Radio Level Integration with IPsec Tunnel. This function allows the eNB to request a WT to provide tunnel resources for LWIP operation for a certain UE while keeping responsibility for that UE.
Reporting of General Error Situations. This function allows reporting of general error situations, for which function specific error messages have not been defined.
Resetting the Xw. This function is used to reset the Xw interface.

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

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

Function	Elementary Procedure(s)
WLAN Status Reporting	a) WT Status Reporting Initiation b) WT Status Reporting
Setting up the Xw	Xw Setup
WT Configuration Update	WT Configuration Update
LTE-WLAN Aggregation	a) WT Addition Preparation b) WT Association Confirmation c) eNB Initiated WT Modification d) WT Initiated WT Modification e) eNB Initiated WT Release f) WT Initiated WT Release
LTE-WLAN Radio Level Integration with IPsec Tunnel	a) LWIP Addition Preparation b) eNB Initiated LWIP Modification c) eNB Initiated LWIP Release d) WT Initiated LWIP Release
Reporting of General Error Situations	Error Indication
Resetting the Xw	Reset