at architecture with the enhanced Node B (eNode B) directly connected to the access gateway (aGW), where the lub interface with its stringent delay constraints is no longer needed. The architecture of LTE radio access network is illustrated in Figure 2.4. The eNode B is in charge of single cell Radio Resource Management (RRM) decision, handover decision, scheduling of users in UL/DL, etc. The GW provides termination of the LTE bearer and acts as a mobility anchor point for the user plane. The eNode B is connected to the aGW with the S1 interface. Between the eNode Bs the X2 interface is defined, which is used to connect the eNode Bs with each other in the network. Unlike HSPA, which was accommodated within the Release 99 UMTS architecture, 3GPP defines a new Packet Core, the EPC network architecture, to support the E-UTRAN. The EPC is designed to have a simplified network architecture with a reduction in the number of network elements, simpler functionality and improved redundancy. And most importantly it allows for connections and handover to other 3G networks and non-3GPP fixed line and wireless access technologies (e.g. WLAN, WiMAX), giving the service providers the ability to deliver a seamless mobility experience. Additionally, to reduce the operator system cost LTE/SAE will provide a smooth evolution path for the existing 2G and 3G networks, SO that the inter-working with UMTS Re199/HSDPA/HSUPA and GSM/GPRS is possible. 2 UMTS Evolution eNode B eNode B eNode B E-UTRAN Figure 2.4: LTE radio access network Though LTE/SAE is not a major concern of this thesis, it is worthy to mention here as it is SO far the latest evolution of UMTS which is going to receive a lot of attention in the upcoming years. By understanding its goals and targets on increasing efficiency, reducing costs, improving services, making use of new spectrum opportunities, and better integration with other open standards, it helps to recognize the new requirements imposed by the LTE/SAE in the transport network and in the core network in the f