Lapped-OFDM as an alternative to CP-OFDM for 5G asynchronous access and cognitive radio

In spite of widely recognized benefits, the acceptance of filter bank multicarrier (FBMC) as an alternative to cyclic prefix orthogonal frequency division multiplexing (CP-OFDM) for the physical layer of future mobile and wireless communication systems is restrained by the introduction of offset-quadrature amplitude modulation (OQAM). The proposed approach, based on the so-called lapped transform, combines a simple yet efficient perfect reconstruction real filter bank with QAM modulation. Real processing of the real and imaginary components of the QAM data samples introduces a symmetry of the used carriers and the spectrum of the multicarrier signal can be either continuous or fragmented. Implementing the receiver with an extended FFT allows for frequency domain channel equalization and the performance achieved is sufficient to avoid the need for a cyclic prefix. The scheme is appropriate for asynchronous access and the filter provides a high level of spectral protection, as required by users in cognitive radio scenarios.