ion air-interface. The specification was created by the 3GPP and the name WCDMA is widely used for both the FDD and TDD operations. 3G networks consist of two major parts: the radio access network (RAN) and the core network (CN), as shown in Figure 1.5. The RAN consists of both the radio and transmission parts. 1.5.1 Radio Access Network (RAN) The main elements in this part of the network are the base station (BS) and the radio network controller (RNC). The major functions include management of the radio resources and telecommunication management. THIRD-GENERATION MOBILE NETWORKS lu-cs Ju-ps lu-es Internet lu-pt Figure 1.5 Third-generation system (WCDMA) Base Station (BS) The base station in 3G is also known as node B. The base station is an important entity as an interface between the network and WCDMA air interface. As in second-generation networks, transmission and reception of signals from the base station is done through om- nidirectional or directional antennas. The main functions of the BS include channel coding, interleaving, rate adaptation, spreading, etc., along with processing of the air-interface. Radio Network Controller (RNC) This acts as an interface between the base station and the core network. The RNC is responsible for control of the radio resources. Also, unlike in GSM, the RNC in conjunction with the base station is able to handle all the radio resource functions without the involvement of the core network. The major functions of the RNC involve load and congestion control of the cells, admission control and code allocation, routing of the data between the Iub and Iur interfaces etc. 1.5.2 Core Network (CN) The core network in 3G networks consists of two domains: a circuit-switched (CS) domain and a packet-switched (PS) domain. The CS part handles the real-time traffic and the PS part handles the other traffic. Both these domains are connected to other networks (e.g. CS to the PSTN, and PS to the public IP network). The protocol design of the UE and UTRAN is based on the new WCDMA technology