Being capable of enhancing the spectral efficiency (SE), faster-than-Nyquist (FTN) signaling is a promising approach for wireless communication systems. This paper investigates the doubly-selective (i.e., time- and frequency-selective) channel estimation and data detection of FTN signaling. We consider the intersymbol interference (ISI) resulting from both the FTN signaling and the frequency-selective channel and adopt an efficient frame structure with reduced overhead. We propose a novel channel estimation technique of FTN signaling based on the least sum of squared errors (LSSE) approach to estimate the complex channel coefficients at the pilot locations within the frame. In particular, we find the optimal pilot sequence that minimizes the mean square error (MSE) of the channel estimation. To address the time-selective nature of the channel, we use a low-complexity linear interpolation to track the complex channel coefficients at the data symbols locations within the frame. To detect the data symbols of FTN signaling, we adopt a turbo equalization technique based on a linear soft-input soft-output (SISO) minimum mean square error (MMSE) equalizer. Simulation results show that the MSE of the proposed FTN signaling channel estimation employing the designed optimal pilot sequence is lower than its counterpart designed for conventional Nyquist transmission. The bit error rate (BER) of the FTN signaling employing the proposed optimal pilot sequence shows improvement compared to the FTN signaling employing the conventional Nyquist pilot sequence. Additionally, for the same SE, the proposed FTN signaling channel estimation employing the designed optimal pilot sequence shows better performance when compared to competing techniques from the literature.

翻译：为提升频谱效率，超奈奎斯特（FTN）信令是无线通信系统中一种颇具前景的方案。本文研究了FTN信令的双选择性（即时间选择性和频率选择性）信道估计与数据检测问题。我们考虑由FTN信令和频率选择性信道共同导致的符号间干扰（ISI），并采用一种开销降低的高效帧结构。基于最小平方误差和（LSSE）方法，我们提出了一种新颖的FTN信令信道估计技术，用于估计帧内导频位置处的复信道系数。具体而言，我们找到了使信道估计均方误差（MSE）最小化的最优导频序列。为应对信道的时间选择性，我们采用低复杂度的线性插值来跟踪帧内数据符号位置处的复信道系数。为检测FTN信令的数据符号，我们采用基于线性软输入软输出（SISO）最小均方误差（MMSE）均衡器的Turbo均衡技术。仿真结果表明，采用所设计的最优导频序列的FTN信令信道估计的MSE，低于为传统奈奎斯特传输设计的对应方案。与采用传统奈奎斯特导频序列的FTN信令相比，采用所提出的最优导频序列的FTN信令的误码率（BER）有所改善。此外，在同等频谱效率下，与文献中的竞争技术相比，采用所设计的最优导频序列的FTN信令信道估计展现出更优性能。