ex types) and TDD [10]. Layer 3 Radio Resource Control (RRC) Logical channels Layer 2 Medium Access Control Transport channels Layer 1 Physical layer Figure 3.2 Radio interface protocol architecture. Reproduced with permission from © 2009 3GPP [10] 3GPP Evolved Packet System (EPS) In the downlink, OFDM is selected as the air-interface for LTE. OFDM is a particular form of multi-carrier modulation (MCM). Generally, MCM is a parallel transmission method which divides an RF channel into several narrower bandwidth sub-carriers and transmits data simultaneously on each sub-carrier. OFDM is well suited for high data rate systems which operate in multi-path environments because of its robustness to delay spread. The cyclic extension enables an OFDM system to operate in multi-path channels without the need for complex equalizers. Thus, it allows frequency-selective scheduling, frequency-diverse scheduling, frequency reuse one-deployments and flexible bandwidth operation. Smart antenna technologies are also easier to support with OFDM, since each sub-carrier becomes flat faded and the antenna weights can be optimized on a per-sub-carrier or block of sub-carriers basis. In addition, OFDM enables broadcast services on a synchronized single frequency network (SFN) with appropriate cyclic prefix design. This allows broadcast signals from different cells to combine over- the-air, thus significantly increasing the received signal power and supportable data rates for broadcast services [11]. SC-FDMA was selected because of its better Peak-to-Average Ratio (PAPR) as compared to OOFDM in the uplink because of its inherent single carrier structure. SC-FDMA solution is based on the use of cyclic prefix to allow high performance and low complexity receiver implementation in the eNodeB. As such the receiver requirements are more complex than in the case of OFDMA for similar link performance but this is not considered to be a problem in the base station. The terminal is only assigned with contiguous spectrum blocks in the frequency dom