The exclusive usage of QoS mechanisms as described in TS 23.207 is not enough to guarantee full end-to-end QoS when interworking with external IP network domains, e.g. in those backbone networks which do not themselves contain IMS network elements. This is mainly because the described QoS concept presumes that the interconnecting IP networks are controlled by PLMN operators or other IMS operators. As a result, it is problematical to provide complete end-to-end QoS guarantees when interworking with external IP network domains or backbone networks which provide IP QoS mechanisms. Especially for delay-sensitive services with strict end-to-end QoS requirements such as conversational speech or streaming video, the existing QoS concept may not satisfy the service requirements when interworking with such IP network domains and backbone networks. Consequently, new QoS concepts that are scalable and can take into account overall end-to-end network performance must be assessed.

The present document investigates possible solutions to enhance the end-to-end QoS architecture as currently specified in TS 23.207 to achieve improved end-to-end QoS in the case of interworking with IP network domains or backbone networks that provide IP QoS mechanisms and enhanced interworking with other next generation networks. Within this technical report, emerging QoS standardization efforts from TISPAN, ITU-T, and the IETF should be taken into account.