Joint Precoding and Pre-Equalization for Faster-Than-Nyquist Transmission Over Multipath Fading Channels

• Published in: IEEE transactions on vehicular technology Vol. 71; no. 4; pp. 3948 - 3963
• Main Authors: Wen, Shan, Liu, Guanghui, Liu, Chengxiang, Qu, Huiyang, Zhang, Lei, Imran, Muhammad Ali
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.04.2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Channel estimation; channel estimation and data detection; Channels; Complexity; Equalization; Fading channels; Faster-than-Nyquist signaling (FTNS); Frequency domain analysis; multipath fading channel; Partial transmit sequences; Performance enhancement; pre-equalization; Precoding; Receivers; Transmitters; waveform design
• ISSN: 0018-9545; 1939-9359
• DOI: 10.1109/TVT.2022.3146423

Faster-than-Nyquist signaling (FTNS) has emerged as a promising technique to increase communication capacity in bandwidth-limited channels. However, the presence of FTN-induced inter-symbol interference (FTN-ISI) in the received observations, is detrimental to channel estimation (CE) and data detection in terms of computational complexity and performance. This paper copes with these problems by incorporating linear pre-equalization (LPE) and composite precoding formed by linear spectral precoding and Tomlinson-Harashima precoding (THP), into the FTNS. Specifically, LPE completely pre-equalizes the FTN-ISI, while spectral precoding resolves the LPE-caused signal spectral broadening by introducing proper artificial ISI, which is pre-equalized by THP. Channel-induced ISI, as the only ISI component in the observations, is estimated and equalized using the classical frequency-domain low-complexity schemes. We show that there are four advantages of the LPE-aided CE over the CE designed for the FTN transmissions without FTN-ISI pre-equalization, namely lower pilot overhead, simpler yet optimal pilot sequence design, lower mean-squared error of CE, and more robust against the FTN-ISI. Simulation results show that our scheme improves the performance of CE and detection, compared to existing FTN frequency-domain CE and equalization schemes.