Faster-than-Nyquist (FTN) signal achieves higher spectral efficiency andcapacity compared to Nyquist signal due to its smaller pulse interval ornarrower subcarrier spacing. Shannon limit typically defines the upper-limitcapacity of Nyquist signal. To the best of our knowledge, the mathematicalexpression for the capacity limit of FTN non-orthogonal frequency-divisionmultiplexing (NOFDM) signal is first demonstrated in this paper. Themathematical expression shows that FTN NOFDM signal has the potential toachieve a higher capacity limit compared to Nyquist signal. In this paper, wedemonstrate the principle of FTN NOFDM by taking fractional cosinetransform-based NOFDM (FrCT-NOFDM) for instance. FrCT-NOFDM is first proposedand implemented by both simulation and experiment. When the bandwidthcompression factor $\alpha$ is set to $0.8$ in FrCT-NOFDM, the subcarrierspacing is equal to $40\%$ of the symbol rate per subcarrier, thus thetransmission rate is about $25\%$ faster than Nyquist rate. FTN NOFDM withhigher capacity would be promising in the future communication systems,especially in the bandwidth-limited applications.
展开▼
