The solution for support of IMS Emergency calls defined for Rel-7 in TS 23.167 has a number of limitations and potential limitations. These include restriction only to certain IP-CANs, restriction only to cases where at least part of the IP-CAN and visited IMS belong to the same operator, possible non-alignment with the various allowed IETF solutions and possible performance limitation. While it is possible that none of these limitations will be significant for some deployments of this service, it is not certain that this will apply to all deployments. Therefore it has been decided to evaluate both the service defined in TS 23.167 and possible extensions that might overcome these limitations.

The present document provides a study investigating possible limitations of the solution for IMS emergency calls defined for Rel-7 in TS 23.167, as well as possible extensions of that solution to reduce or eliminate some or all of the identified limitations. The study item is expected mainly to concern IMS although some aspects of IP-CAN support may also be included. The study item has the following objectives

• Evaluate the feasibility of supporting IMS emergency calls for combinations of IP access network A and IMS core network B not supported in Rel-7 including but not limited to the following cases:
  • A is any IP access network and B is the home 3GPP compliant IMS network for any emergency calling UE with adequate security credentials
  • A is any IP access network and B is a visited 3GPP compliant IMS network for any emergency calling roaming UE with adequate security credentials
    Additional user cases may also be proposed and evaluated during the SI if deemed applicable.
• Evaluate other enhancements to the solution for IMS emergency calls in Release 7 that may improve performance and/or reduce complexity
• Evaluate the feasibility of better aligning the solution in TS 23.167 with applicable IETF standards and draft standards (e.g. from the Ecrit and Geopriv working groups)
• Any enhancement to the support of IMS emergency calls shall remain backward compatible to the solution in Rel-7 from the perspective of the UE and any 3GPP network element. Furthermore, any enhancement should be based on the solution in Rel-7 and should avoid unnecessarily adding new network entities, protocols and interfaces and moving existing functions from one entity to another.

The study item is expected to enable SA WG2 to decide which of the above objectives if any may be worth supporting in Rel-8 and which extensions to the current solution would then be appropriate.

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.