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Precoded faster-than-Nyquist signaling using optimal power allocation for OTFS

Zekun Hong, Shinya Sugiura, Chao Xu, Lajos Hanzo

TL;DR

The performance results demonstrate that the proposed FTN-based OTFS scheme can enhance the information rate while achieving a comparable BER performance to that of its conventional Nyquist-based OTFS counterpart that employs the same root-raised-cosine shaping filter.

Abstract

A precoded orthogonal time frequency space (OTFS) modulation scheme relying on faster-than-Nyquist (FTN) transmission over doubly selective fading channels is {proposed}, which enhances the spectral efficiency and improves the Doppler resilience. We derive the input-output relationship of the FTN signaling in the delay-Doppler domain. Eigenvalue decomposition (EVD) is used for eliminating both the effects of inter-symbol interference and correlated additive noise encountered in the delay-Doppler domain to enable efficient symbol-by-symbol demodulation. Furthermore, the power allocation coefficients of individual frames are optimized for maximizing the mutual information under the constraint of the derived total transmit power. Our performance results demonstrate that the proposed FTN-based OTFS scheme can enhance the information rate while achieving a comparable BER performance to that of its conventional Nyquist-based OTFS counterpart that employs the same root-raised-cosine shaping filter.

Precoded faster-than-Nyquist signaling using optimal power allocation for OTFS

TL;DR

The performance results demonstrate that the proposed FTN-based OTFS scheme can enhance the information rate while achieving a comparable BER performance to that of its conventional Nyquist-based OTFS counterpart that employs the same root-raised-cosine shaping filter.

Abstract

A precoded orthogonal time frequency space (OTFS) modulation scheme relying on faster-than-Nyquist (FTN) transmission over doubly selective fading channels is {proposed}, which enhances the spectral efficiency and improves the Doppler resilience. We derive the input-output relationship of the FTN signaling in the delay-Doppler domain. Eigenvalue decomposition (EVD) is used for eliminating both the effects of inter-symbol interference and correlated additive noise encountered in the delay-Doppler domain to enable efficient symbol-by-symbol demodulation. Furthermore, the power allocation coefficients of individual frames are optimized for maximizing the mutual information under the constraint of the derived total transmit power. Our performance results demonstrate that the proposed FTN-based OTFS scheme can enhance the information rate while achieving a comparable BER performance to that of its conventional Nyquist-based OTFS counterpart that employs the same root-raised-cosine shaping filter.

Paper Structure

This paper contains 11 sections, 3 figures.

Table of Contents

  1. Introduction
  2. System Model
  3. Transmit Signal
  4. Channel Model
  5. Receiver Model
  6. Power Allocation for the Proposed OTFS-FTN
  7. Mutual Information
  8. Power Allocation
  9. Demodulation
  10. Performance Results
  11. Conclusions

Figures (3)

  • Figure 1: Normalized information rate of the proposed OTFS-FTN signaling scheme with and without PA. The information rates of the conventional Nyquist-based OTFS schemes with the ideal rectangular pulse filter ($\beta=0$) and the RRC filter ($\beta=0.25$) are also plotted.
  • Figure 2: BER performance; (a) perfect/estimated CSI, (b) comparisons with EVD-FTN signaling ishihara2021eigendecomposition, DMFTN signaling ishihara2023differential, and OFDM.
  • Figure 3: BER performance for different packing ratios with the fixed transmission rate. (a) $R_\mathrm{t}=1.5$ bps/Hz. (b) $R_\mathrm{t}=3$ bps/Hz.