wn in Fig. 3.19. 3.2.3.2 Filter Bank Multicarrier Filter bank multicarrier (FBMC) is an OFDM-based waveform wherein subcarriers are indi- vidually processed through filters that suppress their side-lobes, making them strictly band- limited. The transmitter and receiver may still be implemented through FFT/IFFT blocks or polyphase filter structures and band-limitedness may offer larger spectral efficiency than OFDM. During the study of waveforms, FBMC was found promising mainly due to signal band-limitedness in order to relax synchronization requirements in the uplink and/or in the 338 Chapter 3 IFFT/CP Spectrum f((n) Spectrum CP removal/ insertion shaping f. (n) Channel 1(n) shaping filter synchronization f1 (-n) IFFT/CP Spectrum Spectrum CP removal/ insertion shaping f(n(n) Channel hn(n) shaping filter synchronization fn (-n) gNB processing Figure 3.19 F-OFDM uplink asynchronous communication. downlink with coordinated transmission, its greater robustness to frequency mis-alignments among users when compared to OFDM, and its more flexible exploitation of frequency white spaces in cognitive radio networks. The rectangular impulse adopted in OFDM sys- tems is not well-localized in time and frequency, making it sensitive to timing and fre- quency offsets (e.g., introduced by channel, or local oscillator mismatch). As we discussed earlier, ideal time and frequency well-localized pulse does not exist in practice for the conventional OFDM according to Balian- - Low theorem. 12 However, if pulse amplitude modulation (PAM) symbols instead of QAM symbols are considered, time and frequency well-localized pulse can be achieved in a multicarrier system called FBMC. The transmit signal can be expressed as k=-00 where g(t) is a square-integrable function on real domain (Gabor set), which is manifested as the rectangular pulse in OFDM, and Sk,n denotes real-valued data symbols. In FBMC, the pulse g(t) can be designed to achieve better time and frequency localization properties using filter design methods. Usually, the prototyp