 is used to suppress OOB emissions. However, for GFDM, multiple OFDM symbols are grouped into a block and a CP is added to the block. Within a block, the prototype filter is cyclic-shift in time, for dif- ferent OFDM symbols. Therefore, better OOB leakage suppression can be achieved relative to CP-OFDM. However, the approach results in a complicated receiver to handle the ISI and ICI. Furthermore, the prototype filter may require more complicated modulation, for example, OQAM as in FBMC, and more complex receiver architecture. Higher block pro- cessing latency is inevitable in GFDM given that there is no possibility for pipelining, and multiplexing with CP-OFDM requires a large guard band, which would add to the overhead. The comparison of the PSDs of the OFDM and GFDM signals is shown in Fig. 3.25. In the processing of the GFDM signal, a pulse-shaping filter with roll-off factor B = 0.1 and N = 10 symbols were used. Furthermore, we assume that NFFT = 1024 , OFDM Ng = 10 and GFDM Ng = 100 samples. It is shown that while the relative complexity of GFDM pro- cessing is more than that of OFDM, the OOB components are significantly more suppressed compared to that of the OFDM signal. 3.2.3.5 Faster Than Nyquist Signal Processing Faster than Nyquist (FTN) is a non-orthogonal transmission scheme which was one of the approaches initially considered for 5G systems that was expected to improve the spectrum New Radio Access Physical Layer Aspects (Part 1) 345 efficiency by increasing the data rate. It was observed a few decades ago that the binary sinc pulse can be transmitted faster than what the Nyquist theorem states without increasing the bit error rate and despite of ISI. The idea was extended to frequency domain to reduce subcarrier spacing. The transmit signal of FTN can be expressed as follows [4]: where AT < 1 is the time compression factor, which means that the pulses are transmitted faster a factor of 1/AT and AF < 1 is the frequency compression factor, which means the spectral efficiency is increased by a factor