 to RAN resources and radio characteristics. The E-UTRAN should provide mechanisms to support the efficient transmission and operation of higher layer protocols over the radio interface, such as IP header compression. E-UTRAN should support further enhanced IMS and core network. E-UTRA should support various types of service including currently available services like web- browsing, FTP, video-streaming or VoIP, and more advanced services (e.g., real-time video or push-to-x) in the PS- domain. VoIP should be supported with at least as good radio, backhaul efficiency and latency as voice traffic over the UMTS CS networks. The E-UTRA and E-UTRAN requirements should minimize the complexity of the E-UTRA UE in terms of size, weight, battery life (standby and active) consistent with the provision of the advanced services of the E-UTRA/UTRAN. Overall the entire E-UTRA and E-UTRAN System should be made cost efficient. LTE Air Interface Figure 3.2 shows E-UTRA radio interface protocol architecture around LTE showing layers 1-3. The physical layer interfaces with MAC (sublayer of Layer 2) and the Radio Resource Control Layer (sublayer of Layer 3). The circles between different layer/sublayers indicate Service Access Points (SAPs). The physical layer offers data transport services to higher layers through a transport channel via the MAC sublayer. The transport channel is characterized by how the information is transferred over the radio interface. MAC offers different Logical channels to the Radio Link Control (RLC) sublayer of Layer 2 where a logical channel is characterized by the type of information transferred [10]. 3.4.1 Multiple Access The multiple access scheme for the LTE physical layer is based on Orthogonal Frequency Division Multiplexing (OFDM) with a cyclic prefix (CP) in the downlink, and on Single-Carrier Frequency Division Multiple Access (SC-FDMA) with a cyclic prefix in the uplink. To support transmission in paired and unpaired spectrum, two duplex modes are supported, namely FDD (full duplex and half dupl