PSTN call control over ATM switching system

The asynchronous transfer mode (ATM)-based broadband integrated services digital network (B-ISDN) may become the first network which can really fulfill the promise to integrate all types of communication services and applications. To achieve this objective, B-ISDN should ensure the continued support of existing interfaces and services, such as PSTN. This paper describes the system structure for accommodating PSTN subscribers in the ATM switching system, IWS (inter-working subsystem). We present the software structure for call processing and control between heterogeneous switches and some specific aspects for the voice service in the ATM switching system.