Asterisk as a Public Switched Telephone Network Gateway for an IMS test bed

Network operators are in the process of adopting the IP Multimedia Subsystem (IMS) as their main underlying infrastructure which will in turn be used as a Service Delivery Platform (SDP). This process requires the migration of current services to their IMS counterparts, as well as a compatibility layer enabling successfull communication between IMS and other network infrastructures. Any and all functionality within IMS is normally available through an Application Server (AS). This paper presents an implementation of a Public Switched Telephone Network (PSTN) Gateway which is able to successfully interface with an IMS test bed. Consequently, it also allows calls to be placed between IMS and other Voice over IP (VoIP) providers. The gateway is enabled as an AS with the help of Asterisk.