A study on evolving the architecture of circuit switched domain in UMTS core networks

Most mobile operators, particularly those operators with 2G GSM networks, prefer UMTS R99 or R4 as their 3G standard to evolve and upgrade their legacy 2G mobile networks. The UMTS technique, as a smooth replacement for GSM technique, provides an evolved path for the mobile operators to deploy the next generation IP based soft-switch mobile core networks. This paper first describes the basic architecture and topology of UMTS R4 core network and introduces two options in network planning: flat structure or layered structure. To propose an evolution path, the paper then suggests a “three layer structure” solution to seamlessly converge UMTS R4 core network with legacy GSM core network. The proposed solution approach achieves the all-IP vision and is capable of convergence with IMS and EPC.