become compute intensive for massive MIMO system. Consider an 8-layer X 64-antenna matrix and an 8X1 input vector that needs to be multiplied for each symbol at a 28,000 symbol/second rate for <6 GHz operation. Signal-to-noise ratio (SNR)/Error Vector Magnitude (EVM) requirements define the required precision of the FFT. Assuming 30 dB SNR required for 256QAM operation, the (i)FFT precision would need to provide margin by having SNR of ~ 45 dB or better. Digital up conversion, channelization, and digital down conversion Digital up-conversion (DUC) functionalities are channel filter, up-sampling, and mixing in the case where multiple separate digital carriers are transmitted over a single (analog chain and) antenna. The channel filter aims to filter out-of-band signal components to meet Adjacent Channel Leakage Ratio (ACLR) requirements. Up-sampling is done in the case of multiple carriers to bring all carriers to the composite (sum of all carriers) sampling rate. Mixing is to multiplex all carriers and is only present in the case of multicarrier. This brings Tx signal to DAC sampling rate. Some filtering is done to remove the alias. The analog filter will also remove part of the aliasing so up-sampling filters are designed in conjunction of the analog filter SO that both provide a good aliasing rejection. Digital down conversion is the reverse step of DUC and used in the receiver path to bring the sampled signal down to baseband and provide antialiasing filtering beyond what was provided by analog filters. If needed, channelization is included to separate out individual RF carriers. Peak-to-average power ratio reduction and performance improvement techniques The OFDM waveform has gained a lot of popularity in the past two decades thanks to its robustness against multipath channel which is caused by the multiple reflections that occur on the radio channel of an air interface or even on the cable. The OFDM waveform (Fig. 2-32) breaks the channel in multiple quasi independent subchannels centered on sub- carriers. T