Digital cellular telecommunications system (Phase 2+); Universal Mobile Telecommunications System (UMTS); General requirements on interworking between the Public Land Mobile Network (PLMN) and the Integrated Services Digital Network (ISDN) or Public Switc
"The present document identifies the Mobile-services Switching Centre/Interworking Functions (MSC/IWFs) and requirements to support interworking between: a) PLMN and PSTN; b) PLMN and ISDN; for circuit switched services in the PLMN. It is not possible to treat ISDN and PSTN as one type of network@ even when both ISDN and PSTN subscribers are served by the same exchange because of the limitations of the PSTN subscribers access i.e. analogue connection without D-channel signalling. Within the present document@ the requirements for voice and non-voice (data) calls are considered separately. From R99 onwards the following services are no longer required by a PLMN: - the dual Bearer Services ""alternate speech/data"" (BS 61) and ""speech followed by data"" (BS 81); - the dedicated services for PAD (BS 4x) and Packet access (BS 5x); - the single asynchronous and synchronous Bearer Services (BS 21..26@ BS 31..34). From Rel-4 onwards the following services are no longer required by a PLMN: - the synchronous Bearer Service non-transparent (BS 30 NT); - the Basic Packet access; - Non-transparent facsimile (TS 61/62 NT) for the A/Gb mode and GERAN Iu mode. If a PLMN still provides these services it shall fulfil the specification of former releases. The present document is valid for a PLMN in A/Gb mode as well as in Iu mode. If text applies only for one of these systems it is explicitly mentioned by using the terms ""A/Gb mode"" and ""Iu mode"". If text applies to both of the systems@ but a distinction between the ISDN/PSTN and the PLMN is necessary@ the term ""PLMN"" is used. NOTE: The Gb interface does not play any role in the scope of the present document although the term ""A/Gb mode"" is used."