ler than that of the original subband-based approach. In the receiver side, in order to filter out the signals of the neighboring subbands, the received signal in baseband is first passed through the receiver spectrum shaping filter. Subcarrier-based, subband-based, or a composite approach can be employed by the receiver, independent of the approach employed by the transmitter. After the subband spectrum shaping, the resulting signal is processed by the regular OFDM processing within that subband. The filters used in F-OFDM processing must satisfy a number of criteria. The passband of the filter should be as flat as possible over the subcarriers contained in the subband. This ensures that the distortion caused by the filter in the data subcarriers, especially the subband edge subcarriers, is minimal. The frequency roll-off of filter should start from the edges of the passband and the transition band of the filter should be sufficiently steep. This ensures that the system bandwidth is utilized as efficient as possible and the guard band overhead is minimized. Also, the neighboring subband signals with different numerologies can be placed next to each other in frequency with minimal number of guard subcarriers. The filter should further have sufficient stop-band attenuation to ensure that the leakage into the neighboring subbands is negligible. The F-OFDM waveform processing introduces negligible delay at the receiver side. Signal processing delay of F-OFDM depends on the receiver processing capabilities. It should be noted that the only extra signal processing block in F-OFDM receiver compared to CP- OFDM is the receiver subband spectrum shaping filter. The delay due to spectrum shaping filter is implementation-specific and depends on the receiver processing capabilities. The rest of receiver processing blocks in F-OFDM, for example, FFT block size, channel estima- tion/equalization are the same as those in CP-OFDM [49]. The F-OFDM concept can be used in the asynchronous access of multiple UEs in the uplink as sho