A communication method for calling on the circuit switched domain of core networks of GSM/WCDMA

The invention provides a communication method for calling on the circuit switched domain of core networks of GSM/WCDMA. The method sets up a call signaling and communicates between (G)MSCs or (G)MSC Servers through SIP/SIP-T protocol, which solves the problem of communication between the core networks of WCDMA and fixed NGN, cama2000 in ALL IP network. According to the invention, all servers use unite SIP/SIP-T signaling, and terminal to terminal route takes the place of former hop by hop route by the route solution, such as, ENUM, route server, etc, to make hierarchical network into planar network, which reduces the network architecture and takes the advantage of IP network.