GSMA has been investigating a new VoLTE roaming architecture option, "S8 Home Routed (S8HR)". GSMA Product and Services Management Committee (PSMC) has informed 3GPP that they endorsed S8HR architecture as a candidate for VoLTE roaming under the assumption that the related issues (inclusive of Lawful Interception, Emergency Call, SRVCC, and others) will be resolved by 3GPP. S8HR is an architecture for IMS voice roaming whereby the PGW, PCRF, P-CSCF, ATCF and ATGW are located in the HPLMN also when the UE is roaming in a VPLMN. One of the main implications is that S8HR roaming architecture is not using Local Breakout anymore and therefore the IMS APN is resolved to point to a PGW in the HPLMN (rather than in the VPLMN). The S8HR architecture limits existing Lawful Interception solutions based on 3GPP standards in the VPLMN in detecting, retrieving and reporting to Law Enforcement Agencies targeted roaming IMS communication when obligated to do so by an intercept request (e.g. lawful authorization or warrant). Equivalent Lawful Interception services for VoLTE that are directly accessible at IMS level (as defined in TS 33.107) will have to be specifically implemented for S8HR in VPLMN potentially requiring new functions, and new interfaces to be defined. The proposed solutions will provide in real time the LI services that are normally directly accessible at IMS level in the VPLMN. The proposed solutions need to analyse each Inbound Roamer's SIP message, in order (when there is an interception decision) to initiate in real time duplication of CC, generation in real time of IRI (including CC correlation, Location processing) for delivery over X2 interface. The present document studies potential solutions for LI services for S8HR providing equivalent Lawful Interception services for VoLTE meeting the requirements defined in TS 33.106 when Confidentiality Protection is not used (no encryption of SIP messages, and no encryption of RTP flows) on any of the S8HR bearers, at point of Interception.

The present document studies and identifies the changes to the LI architecture, function and protocols for inbound roamers in the VPLMN when S8HR is employed which is equivalent to the LI service level for Local Breakout (LBO) in the VPLMN for VoLTE services. Covered by the present document includes:

• Potential enhancements to the LI service architecture to accommodate the S8HR roaming architecture in the VPLMN to meet all the current LI regulatory requirements applicable to voice and other IMS service roaming are considered and compared.
• Considerations on maximizing re-use of existing 3GPP defined capabilities such as PCC is considered.
• Exploration of the changes that may be needed to TS 33.107 and TS 33.108.

Finally, the present document provides recommendations for proceeding with implementing the selected approach. This study item takes into account GSMA related activities.

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.