IFFT and the cyclic prefix is added. At the receiver side, the base station basically performs the reverse operations with respect to the process in the transmitter. The amplitude and phase variation due to the transmission in a frequency-selective fading are compensated by an equalizer. The equalizer is basically a one-tap frequency domain equalizer located at the output of the FFT in the receiver. The equalizer coefficients in Equation (6.10) can be generated based on either zero forcing (ZF) or minimum mean square error (MMSE). The zero forcing applies channel inversion, and the equalization coefficient is given by (6.13) The ZF has a disadvantage in terms of noise enhancement for small amplitudes of Hm,k [9]. To overcome the noise enhancement problem in the ZF technique, the FDE complex coefficient, Cm,k> can also be obtained under the MMSE criterion. This is given by [10] (6.14) © 2009 by Taylor & Francis Group, LLC Long Term Evolution: 3GPP LTE Radio and Cellular Technology Table 6.2 UTRA LTE Uplink Simulation Parameters Parameter Value Carrier frequency 2 GHz Transmission BW 10 MHz Subframe duration 0.5 ms Subcarrier spacing 15 kHz SC-FDM symbols/TTI 6 LBs, 2 SBsa CP duration 4.1 us FFT size/useful subcarriers 1024/600 MCS settings 2 BPSK: 1/6, 1/3 QPSK: 1/2, 2/3, 3/4 8 PSK: 1/3, 1/2, 2/3, 3/4 16 QAM: 1/2, 2/3, 3/4, 4/5 Channel code 3GPP rel. 6 compliant turbo code with basic rate 1/3 Rate matching, interleaver 3GPP rel. 6 compliant Channel estimation Ideal Antenna schemes Channel model Typical urban 6 paths [6] Speed 3 km/h LBs = long blocks; SBs = short blocks. where k denotes the subcarrier index, o? is the variance of the additive noise, and o2 is the variance of the transmitted pilot symbol. The performance of ZF and MMSE in an LTE scenario is investigated in both the SC-FDMA and OFDMA case. The simulation parameters are shown in Table 6.2. Figure 6.8 shows the performance of a lower-order modulation and coding scheme (MCS), BPSK with coding rate 1/6. This result is to represent the impact to the low 