here are already UEs in the market that support both FDD and TDD modes of operation, something which never really happened with 3G The uplink resource allocation is also handled by the eNodeB, with the physical layer signalling indicating every millisecond which devices are allowed to transmit user data in the uplink and in which part of the uplink spectrum. The multiple access with SC-FDMA is based on the transmitter principle as shown in Figure 2.4, with the QAM modulator transmitting one symbol at the time, and not parallel in time domain like in the downlink with OFDMA. The resulting symbol duration is shorter than in the downlink direction and for that reason the cyclic prefix is not added after each symbol but after a block of symbols. As the block of symbols in the uplink has the same duration as a single OFDMA symbol in downlink, the relative overhead is the same from the cyclic prefix also in the uplink. The resulting impact on the eNodeB receiver is that there is now inter-symbol interference between the symbols in the block of transmitted symbols and thus more advanced receiver is needed in the eNodeB side. The Minimum Mean Square Error (MMSE) receiver shown in Figure 2.4 is only an example with the actual receiver solution being left for an eNodeB vendor, similar to the many other algorithms in the eNodeB, such as scheduler solution for both uplink and downlink directions. The sub-carrier mapping in Figure 2.4 can be used to determine in which part of the uplink transmission spectrum the transmitted signal will be transmitted, based on the instructions from the eNodeB (uplink resource grants). Example of the uplink resource allocation is shown in Figure 2.5, with the uplink frequency band being shared by two devices. The uplink allocation for a single UE is always continuous n times 180 kHz piece of uplink spectrum in order to preserve the low peak-to-average uplink waveform. Depending on the frequency resource allocated by the eNodeB, UE transmits always min- imum of 180kHz, with the example of the m