Ethernet is the applied layer 2 technology. In the model, the OPNET built-in Ethernet model is used including the Address Resolution Protocol (ARP) and MAC modules. The ARP is responsible for translating between the physical MAC address and the logical IP address. The MAC includes the functions of addressing as well as channel access control. On the physical links, a variety of available Ethernet links, such as 10BaseT, 100BaseT, 1GBaseT, etc., can be chosen for building the lub links. Modeling of LIPE Multiplexing Schemes In this IP-based UTRAN model, both Composite IP (CIP) and Lightweight IP Encapsulation (LIPE) multiplexing schemes (introduced in A.11) are modeled. They are located between FP and UDP/IP layers. In order to support multiple services with their QoS requirements, different multiplexers can be implemented to support each QoS class. In the current model, two multiplexers for two different QoS classes are modeled: one is for the delay sensitive (typically for the voice application) and the other is for the delay insensitive services (such as web, ftp applications). These two multiplexers and the packetizers are located above the UDP/IP layer. For each multiplex, the number of FP PDUs to encapsulate into one LIPE or CIP container is determined by its configured multiplexing timer and the maximum container packet size. In order to optimize the performance of each service, the multiplexing timer and the maximum container packet length can be tuned individually for different services. For voice service, usually a small multiplexing timer and smaller packet length is better to ensure a small delay. For the delay insensitive data, a larger packet is more efficient for the bandwidth utilization. Modeling of QoS Scheme In this exact IP-based UTRAN model, the QoS provisioning is realized by setting up per QoS class buffer at the Ethernet layer and implementing a scheduler to serve them with different priorities. Currently the model only distinguishes two QoS categories: real time (RT) which is for the delay