Evolution of the UTRAN architecture

In this paper, we discuss possible evolution scenarios for the UMTS Terrestrial Radio Access Network (UTRAN) beyond 3GPP standards Release 5. The current UTRAN has inherited its centralised network architecture with a quite complex central radio network controller (RNC) and simple base stations (called "NodeB" in UMTS) from the 2nd generation GSM system. Fifteen years ago, this basic architecture was designed for GSM to provide wireless access to the circuit-switched, voice-oriented telecommunications network (PSTN). Though in the meantime, the network architecture has been extended to packet data services (General Packet Radio Service GPRS), the rise of the Internet and its different service requirements have not been reflected adequately. With standards Release 5 in 3GPP UMTS, as a first step towards a stronger Internet orientation, IP transport shall replace the ATM-based links between RNC and NodeB. However, the full advantage of IP transport cannot be realised, because of the unchanged characteristics of the interface that requires to carry synchronised radio link blocks with a high quality of service, regardless of the user-service to which they belong. To overcome this drawback and to enable real service differentiation, some modifications of the 3GPP Rel. 5 architecture have been investigated. Preserving the Iu interface between UTRAN and core network, the proposed architecture can take full advantage of the IP-based protocols in the transport network. In addition, it offers improved scalability due to its separation of control and user-plane.