In the growing 3G Universal Mobile Telecommunications System (UMTS) mobile network systems, in order to support a great variety of service characteristics efficiently, a number of different types of Radio Access Bearers (RAB) are provided to carry the packet switched (IP) traffic. Each radio bearer provides a certain peak data rate to transfer user data between UE (User Equipment) and CN (Core Network) for a certain traffic class. The selection of an appropriate bearer depends on the user subscription, service type, requested Quality of Service (QoS), radio characteristics etc. In this paper, the simulation results of transferring packet switched services with multiple RABs each supporting certain QoS are presented. The analytical approach to evaluate the application performance of a single RAB is then extended to support multiple RABs. Additionally, a more precise solution for analytically calculating the average response time for different file size distributions is described. With the help of these improvements the necessary bandwidth on the Iub interface can be determined.
