Low-PAPR Joint Channel Estimation and Data Detection in ZP-OTFS System

Orthogonal Time Frequency Space (OTFS) systems face significant challenges in channel estimation due to high pilot overhead and peak-to-average power ratio (PAPR). To address these issues, we propose a two-step channel estimation method for Zero-Pad OTFS (ZP-OTFS), a modified OTFS system characterized by multiple zero rows along the delay axis. This method strategically inserts pilot sequences into the zero bins of the ZP-OTFS system, effectively mitigating overhead and PAPR. Comprehensive simulation results validate the effectiveness of our proposed method, demonstrating its superior performance over traditional embedded pilot estimation in high Signal-to-Noise Ratio (SNR) scenarios. Specifically, our method achieves a lower normalized mean square error (NMSE) and better bit error rates (BER) at high SNRs

Reliability oriented OTFS-based LEO satellites joint transmission scheme

This paper investigates a dual satellite transmission scheme with coherent reception. The receiver has a single synchronization circuit and is locked to only one of the satellites. Beam-centric pre-compensation techniques are considered in the paper. The cooperation area in which coherent reception is feasible is characterized analytically. The application of precoding to the orthogonal time and frequency space (OTFS) waveform is considered to counteract the residual offsets, which result from the displacement of the receiver from the selected reference point. Numerical evaluations show that the dual satellite scheme improves the system spectral efficiency as well the link reliability in comparison with the single satellite transmission scheme.This paper is part of the R+D+i project (PID2020-115323RB-C31) funded by MCIN/AEI/ 10.13039/501100011033.Peer ReviewedPostprint (author's final draft

OTFS-NOMA: An Efficient Approach for Exploiting Heterogenous User Mobility Profiles

This paper considers a challenging communication scenario, in which users have heterogenous mobility profiles, e.g., some users are moving at high speeds and some users are static. A new non-orthogonal multiple-access (NOMA) transmission protocol that incorporates orthogonal time frequency space (OTFS) modulation is proposed. Thereby, users with different mobility profiles are grouped together for the implementation of NOMA. The proposed OTFS-NOMA protocol is shown to be applicable to both uplink and downlink transmission, where sophisticated transmit and receive strategies are developed to remove inter-symbol interference and harvest both multi-path and multi-user diversity. Analytical results demonstrate that both the high-mobility and low-mobility users benefit from the application of OTFS-NOMA. In particular, the use of NOMA allows the spreading of the high-mobility users' signals over a large amount of time-frequency resources, which enhances the OTFS resolution and improves the detection reliability. In addition, OTFS-NOMA ensures that low-mobility users have access to bandwidth resources which in conventional OTFS-orthogonal multiple access (OTFS-NOMA) would be solely occupied by the high-mobility users. Thus, OTFS-NOMA improves the spectral efficiency and reduces latency