e Emulation (PWE) Technology The above introduced fully IP transport solution requires a complete change of the transport network from ATM to IP in the UTRAN. However, substantial expenditures have been invested for the legacy ATM transport networks for numerous Node Bs and ATM-based interfaces. In order to maximize the usage of the existing ATM based infrastructure in the UTRAN for making the most profits for the network providers, an intermediate migration solution is required meanwhile for a gradual evolution towards fully IP transport. The intermediate migration solution should integrate the use of cost-efficient IP transport to reduce the transport cost while at the same time allow backward compatibility and interworking of RANs with different transport technologies. In this context, Carrier Ethernet [Sie06] is proposed as a cost-effective way for providing the migration solution. It is also a viable solution of converged fixed-mobile access networks, as well as a flexible and reliable way for enabling heterogeneous access networks towards an All-IP network. The deployment of Carrier Ethernet for UTRAN is realized by establishing Pseudo-Wires in the backhaul network. This technique is standardized by the IETF's Pseudo Wire Emulation Edge-to-Edge (PWE3) working group defining various types of Pseudo-Wires to emulate traditional and emerging services such as ATM or frame relay over Packet Switched Network (PSN) [RFC04, RFC05, RFC06]. Figure 2.3 depicts the integration of a Carrier Ethernet-based transport network into an ATM-based UTRAN by means of PWE technique. Both the NodeB and RNC are Customer Edges (CE). They are not aware of using an emulated ATM service over Ethernet, SO they keep transmitting and receiving ATM cells same as in the conventional ATM transport network. The NodeB and RNC are connected to the transport Ethernet network via two intermediate PWE routers which contain dual interfaces for ATM and Ethernet. Such routers are usually located at the edge of the ATM network and the Ethernet network