State Key Laboratory of Information Photonics and Optical Communications, School of Information and Communication Engineering, Beijing University of Posts and Telecommunications (BUPT), Beijing, 100876, China.
Department of Electrical Engineering, Columbia University, New York, 10026, USA.
Sci Rep. 2017 Jun 13;7(1):3380. doi: 10.1038/s41598-017-03571-6.
Faster-than-Nyquist (FTN) signal achieves higher spectral efficiency and capacity compared to Nyquist signal due to its smaller pulse interval or narrower subcarrier spacing. Shannon limit typically defines the upper-limit capacity of Nyquist signal. To the best of our knowledge, the mathematical expression for the capacity limit of FTN non-orthogonal frequency-division multiplexing (NOFDM) signal is first demonstrated in this paper. The mathematical expression shows that FTN NOFDM signal has the potential to achieve a higher capacity limit compared to Nyquist signal. In this paper, we demonstrate the principle of FTN NOFDM by taking fractional cosine transform-based NOFDM (FrCT-NOFDM) for instance. FrCT-NOFDM is first proposed and implemented by both simulation and experiment. When the bandwidth compression factor α is set to 0.8 in FrCT-NOFDM, the subcarrier spacing is equal to 40% of the symbol rate per subcarrier, thus the transmission rate is about 25% faster than Nyquist rate. FTN NOFDM with higher capacity would be promising in the future communication systems, especially in the bandwidth-limited applications.
与奈奎斯特信号相比，快于奈奎斯特（FTN）信号由于其更小的脉冲间隔或更窄的子载波间隔，实现了更高的频谱效率和容量。香农极限通常定义了奈奎斯特信号的上限容量。据我们所知，本文首次展示了 FTN 非正交频分复用（NOFDM）信号的容量限制的数学表达式。该数学表达式表明，FTN 非正交频分复用信号有可能比奈奎斯特信号实现更高的容量限制。在本文中，我们通过实例展示了分数余弦变换（FrCT）-NOFDM 的原理。FrCT-NOFDM 首先通过仿真和实验提出并实现。当 FrCT-NOFDM 中的带宽压缩因子α设置为 0.8 时，子载波间隔等于每个子载波符号率的 40%，因此传输速率比奈奎斯特速率快约 25%。具有更高容量的 FTN-NOFDM 在未来的通信系统中很有前途，特别是在带宽受限的应用中。
