duced latency (below 30 ms), higher user data rates (DL and UL peak data rates up to 100 Mbps and 50 Mbps, respectively), improved system capacity and coverage, as well as reduced CAPEX and OPEX for the operators [9]. In order to fulfill those requirements, 3GPP agreed on a simplified radio archi- tecture. All user plane functionalities for the radio access were grouped under one entity, the evolved Node B (eNB), instead of being spread over several network ele- ments as traditionally in GERAN (BTS/BSC) and UTRAN (Node B/RNC) [8]. Figure 10.2 depicts the resulting radio architecture where: The E-UTRAN consists of eNBs, providing the E-UTRA user plane (PDCP, RLC, MAC) and control plane protocol terminations (RRC) toward the UE and hosting all radio functions such as Radio Resource Management (RRM), dynamic allocation of resources to UEs in both uplink and downlink (scheduling), IP header compression and encryption of user data stream, and measurement and measurement reporting configu- ration for mobility and scheduling. The eNBs may be interconnected by means of the X2 interface. The eNBs are also connected by means of the S1 interface to the Evolved Packet Core (EPC), which resides in the MME/SAE gateway. Figure 10.3 shows the E-UTRA frame structure, which consists of 10 sub- frames, each containing 14 symbol blocks. In the E-UTRAN system, one © 2009 by Taylor & Francis Group, LLC Long Term Evolution: 3GPP LTE Radio and Cellular Technology One radio frame, Tf = 10 ms sub-frame #0 sub-frame #1 sub-frame #1 sub-frame #9 Sub-frame 1.0 ms for a UE PRB DL TB for PDCCH PDSCH Control Control Control Sysinfo S-SCH P-SCH PUSCH PILOT PILOT Figure 10.3 Frame structure in E-UTRAN system [44]. (Source: M. Rinne, Pajukoski et al., "Evaluation of recent advances of the Evolved 3G (E-UTRA) for the VolP and best effort traffic scenarios," IEEE SPAWC, June 2007.) sub-frame (1 TTI) of length 1.0 ms is regarded as the minimum time allocation unit. In the frequency domain, a minimum allocation unit is a Physical Resource Block (PRB),