Support for CDMA circuit mobiles in a SIP-based packet core network: A step on the path to IMS

This paper introduces an architecture based on the Internet Protocol Multimedia Subsystem (IMS) standards that provides packet transport for wireless circuit mode voice services. The motivating force behind this architecture is transcoder-free operation (TrFO), which improves voice quality for mobile-to-mobile calls while reducing the cost of the equipment required to support them. Included in this paper are a description of the architecture, examples of call scenarios supported by the architecture, examples of call flows that demonstrate the use of the Session Initiation Protocol (SIP) in the architecture, and a description of the IMS components that are reused in the architecture.