4 General

24.2343GPP3GPP system to Wireless Local Area Network (WLAN) interworkingRelease 12Stage 3TSWLAN User Equipment (WLAN UE) to network protocols

4.1 3GPP WLAN interworking system

Within this specification, no distinction is made between roaming and non-roaming scenarios. Therefore, within the scope of this specification, the Wa and Wd reference points defined in 3GPP TS 23.234 [2] are considered identical.

The WLAN UE is equipped with a universal integrated circuit card (UICC) in order to access the WLAN interworking service. For emergency cases, and dependent on local regulations, access shall be possible even if the WLAN UE is not equipped with a valid SIM or valid USIM.

NOTE: IMS emergency call can fail due to local regulation and or roaming agreements. Even after the failure of the IMS emergency call a WLAN UE can further attempt the IMS emergency call following the procedures for when the WLAN UE is not equipped with a valid SIM or a valid USIM.

The 3GPP AAA server procedures covered in the present document are:

– Authentication of the 3GPP subscriber based on the SIM/USIM credentials; and

– Access authorization of the 3GPP subscriber based on the WLAN access authorization information retrieved from HLR/HSS.

Other functionalities of the 3GPP AAA server are covered in 3GPP TS 29.234 [3].

WLAN technologies other than those compliant with IEEE 802.11 1999 [11], such as HiperLAN or Bluetooth, are not described specifically in this version of the present document. However, they are not excluded.

4.2 WLAN UE identities

4.2.1 General

WLAN UEs use network access identifier (NAI) as identification towards the 3GPP WLAN AAA server in the EAP Response/Identity message. The NAI is structured according to 3GPP TS 23.003 [1A].

4.2.2 Root NAI

This is the NAI format used by the WLAN UE when it attempts to authenticate directly to HPLMN (see IETF RFC 4284 [12] and 3GPP TS 23.234 [2]). The root NAI format is specified in 3GPP TS 23.003 [1A] subclause 14.3. The usage of the root NAI is specified in clause 5.

4.2.3 Decorated NAI

This is the NAI format used by the WLAN UE when it attempts to authenticate to HPLMN via VPLMN (see IETF RFC 4284 [12] and 3GPP TS 23.234 [2]). The decorated NAI format is specified in 3GPP TS 23.003 [1A] subclause 14.4. The usage of the decorated NAI is specified in clause 5.

4.2.4 Alternative NAI

This is the NAI format used by the WLAN UE when it attempts to obtain a list of available PLMNs during a manual selection procedure. The alternative NAI format is specified in 3GPP TS 23.003 [1A] subclause 14.6. The usage of alternative NAI is specified in clause 5.

4.2.4A Emergency NAI

This is the NAI format used by the WLAN UE when it attempts to authenticate for making an IMS emergency call. The emergency NAI format is specified in 3GPP TS 23.003 [1A] subclause 14.8. The usage of the emergency NAI is specified in clauses 4, 6 and 8.

4.2.5 Username

The generation of, and the rules for the use of the username part of an NAI in the WLAN UE are defined in subclause 6.1. The format of the username part of an NAI is defined in 3GPP TS 23.003 [1A].

4.3 Scanning procedures

4.3.1 IEEE 802.11 WLANs

For IEEE 802.11 [11] WLANs, the WLAN name is provided in the SSID information element.

The WLAN UE becomes aware of the supported WSIDs of the WLAN by performing scanning procedures as specified in IEEE 802.11-2007 [11].

There are two types of scanning procedures specified in IEEE 802.11-2007 [11]:

i) Passive scanning.

ii) Active scanning.

The WLAN UE shall support passive scanning according to IEEE 802.11-2007 [11]. If active scanning is supported then, the WLAN UE should use active scanning according to IEEE 802.11-2007 [11].

In order to assist PLMN selection procedure, the WLAN UE shall create a list of available WSIDs. The list of available WSIDs consists of all WSIDs found in passive scanning and all WSIDs received as a result of active scanning.

The WLAN UE may support additional active scanning procedures as defined in IEEE Std 802.11u™-2011 [23]. If the WLAN UE and WLAN support the IEEE Std 802.11u™-2011 [23] procedures, the list of available PLMNs may be constructed through the use of the Access Network Query Protocol (ANQP).

4.3.2 Other WLAN technologies

Other WLAN technologies, such as HiperLAN or Bluetooth, are not described in this TS but are not excluded.

4.4 Network discovery

4.4.1 General

Network discovery can be performed in three ways:

1) if the "HPLMN Direct Access Indicator" as specified in subclause 7.11 allows direct access, then direct connection from the I-WLAN to HPLMN using internet where authentication has been performed using a none IEEE 802.1x authentication mechanism;

2) via a PLMN using IEEE 802.1x authentication access; or

3) via IEEE Std 802.11u™-2011 [23] ANQP.

In case 1) the WLAN UE once it has obtained I-WLAN access shall perform tunnel management procedures per the clause 8 to access the HPLMN.

In case 2) when IEEE 802.1x authentication mechanisms are used, the network discovery procedure shall be executed between the WLAN UE and the local AAA for the purpose of sending to the WLAN UE the supported PLMNs list for WLAN access for the manual selection procedure. The WLAN UE shall support the identity selection hints for EAP procedure as specified in IETF RFC 4284 [12]. The WLAN UE shall send the alternative NAI to the local AAA to trigger the network discovery procedure. If the I-WLAN is unable to route the WLAN UE’s EAP authentication signalling to the 3GPP AAA server based on the NAI sent in the initial EAP-Response/Identity message and if the local AAA:

a) supports identity selection hints for EAP procedure as described in IETF RFC 4284 [12], then the I-WLAN sends a subsequent EAP-Request/Identity message to the WLAN UE including the supported PLMNs list for WLAN access; or

b) does not support identity selection hints for EAP procedure as described in IETF RFC 4284 [12], then the I-WLAN sends an EAP-Failure message to the WLAN UE.

In case 3) for WLANs and WLAN UEs that support IEEE Std 802.11u™-2011 [23], the WLAN UE shall use ANQP to trigger the sending of the generic container. If the WLAN supports advertisement of PLMNs via IEEE Std 802.11u™-2011 [23] the WLAN shall send back an ANQP response to the WLAN UE including the supported PLMNs list, using the format defined in Annex A. If the WLAN UE receives alternative ANQP responses, where the "Info ID" is not "3GPP Cellular Network information", the behaviour of the WLAN UE is outside the scope of this specification.

NOTE: How the WLAN system obtains the Supported PLMN list when using IEEE Std 802.11u™-2011 [23] procedures is outside of the scope of this specification.

For PLMNs that support emergency optimizations, this is indicated via the inclusion of the emergency specific service realm as defined in 3GPP TS 23.003 [1A].

4.4.2 WLAN UE procedures

Upon reception of an IEEE Std 802.11u™-2011 [23] ANQP response or EAP-Request/Identity message including the supported PLMNs list for WLAN access, the WLAN UE shall:

1) perform PLMN selection according to subclause 5.2;

2) if not authenticating for the purposes of performing IMS emergency call:

a) if the selected PLMN is the HPLMN, then use root NAI as specified in subclause 4.2.2; and

b) if the selected PLMN is a PLMN other than the HPLMN, then use the decorated NAI as specified in subclause 4.2 and using the PLMN ID of the selected PLMN;

3) if authenticating for the purposes of performing IMS emergency call:

a) use emergency NAI as specified in subclause 4.2.4A; and

4) attempt to authenticate as specified in subclause 6.1.1 and using the NAI determined in the prior step.

As an implementation option, the WLAN UE may store the supported PLMNs list for WLAN access.