. The number of taps required for the equalizer is proportional to the symbol rate and the multipath delay. For an OFDM system, if the guard interval is larger than the multipath delay, the ISI can be eliminated and orthogonality can be main- tained among subcarriers. Since each OFDM subcarrier occupies a very narrow spectrum, in the order of a few kHz, even under severe multipath distortion, they are only subject to flat fading. In other words, the OFDM converts a wideband frequency-selective fading channel to a series of narrowband frequency non-selective fading subchannels by using the parallel mul- ticarrier transmission scheme. Since OFDM data subcarriers are statistically independent and identically distributed, based on the central-limit theorem, when the number of subcarriers NFFT is large, the OFDM signal distribution tends to be Gaussian. New Radio Access Physical Layer Aspects (Part 1) 321 3.2.1.2 Pre- and Post-processing Signal-to-Noise Ratio In an OFDM system, the SNR is a measure of channel quality and is a key factor of link-level error assessment. There are different methods for calculation of SNR in single-antenna and multi-antenna transmission systems. For single-input/single-output systems, the SNR can be viewed as the received SNR, that is, the received SNR before the detector. The post-processing SNR is often used for MIMO links and represents the SNR after combining in the receiver and measures the likelihood that a coded message is decoded successfully. In link-level simulations, the SNR r is typically calculated using the following method. Let's vector X = transmit signal where = 1, 2, ,NTX is the complex-valued transmitted symbols from the kth transmit antenna. Note that NTX is the number of transmit antennas. It can be shown that the total transmit signal power can be obtained as 07 = trace(Rx) where Rx denotes the autocorrelation matrix of the transmitted signal. The transmit power from the kth antenna is given as =E{|xx12} = 1/NTX (uniformly distributed power). If H represents the chan