New Multicarrier Modulations for 5G

Recent advances in filter bank multicarrier (FBMC) techniques are presented and compared with the conventional cyclic prefix (CP)-OFDM approach, in the context of 5G. After a brief description of some adaptations of CP-OFDM, FBMC combined with offset-QAM is considered, pointing out the crucial issue of subchannel equalization to compensate for the absence of cyclic prefix. Implementation has to be carried out in the frequency domain, in order to reach high performance without further increasing latency and allow for per user equalization and carrier frequency offset compensation. However, due to the delay objectives and the computational complexity, the prototype filter length, and overlapping factor, must be small, which limits the performance. Then, an alternative approach is proposed, FBMC combined with pulse amplitude modulation (PAM). Like OFDM, FBMC-PAM possesses the perfect reconstruction property and, equipped with the sine prototype filter, it yields good performance with the overlapping factor K = 2, which makes it an attractive option whenever asynchronous access and high level of out-of-band rejection are required. Finally, the case of nonoverlapping emitted symbols is considered and a CP-less OFDM scheme with frequency domain equalizer in the receiver is included in the performance comparison.