A crucial element of cellular communication networks is the achievable spectral efficiency (SE). Indeed, motivated by the continuous growth in mobile data traffic in wireless networks, improving SE has represented one of the key goals of the 3rd Generation Partner Project (3GPP) along several generations of communication standards. In this paper, we propose a novel transmission scheme based on intentionally overlapping the subcarriers of adjacent users considering two state-of-the-art waveforms: the orthogonal frequency division multiplexing (OFDM) and the filter bank multi-carrier with offset quadrature amplitude modulation FBMC/OQAM). We investigate the achievable spectral efficiency improvement of the proposed transmission scheme in the presence and absence of timing offset impairments under the tapped delay line B (TDL-B) multipath 3GPP model of the 5G QuaDRiGa channel. According to the test results, the proposed transmission technique achieves up to 20% SE improvement for FBMC/OQAM when associated to the overlap-save FBMC receiver and 12% for OFDM.