d CN and Uu between User Equip- ment (UE) and NodeB or 3G BS. Within UTRAN, the RNCs communicate with each other over Iur and with 3G-BSs over lub. The key functions to manage are thus: The Radio Access Bearer (RAB) functionality provides the CN with a set of ser- vices between the core network and the UE. It offers RABs appropriate for voice, CS data and PS data, including required information processing and signalling. It also supports multiple RAB connections to one UE, e.g. both voice and packet switched services concurrently to one MS. The UMTS Network and Radio Access Technology Link control functions, i.e. paging, signalling channel management, RAB services, allocation and control of radio and other RAB resources. Mobility functions include: handover, cell re-selection, macro-diversity combining and location update management. Capacity management functions, i.e. control the trade 6 off between capacity, quality and coverage. The essential tasks are: Capacity control handling allocation of the radio resources, which depends upon resource information from involved cells and neighbouring cells. Admission control managing access of new users into the network based, it de- pends on network load status, subscriber priorities and resource availability. Congestion control reducing load in high load situations, e.g. by queuing or delaying packet or best effort traffic. Quality control based on power control features. Transmission and Interface control will aim to manage the logical interfaces, Iu, Iur, lub, which can flexibly be mixed on the physical transport. For example, we can use the same links for access to the CN to carry Iur, or concentration of traffic to several 3G BSs on one physical link. 8.3.4.2 The Core Network (CN) Building Blocks The management of the CN components in this example take into account the horizon- tal integration of functional elements. As illustrated in Figure 8.6, the architecture has a total separation of the payload transport and traffic control into the user plane and the control 