Deterministic Pilot Design and Channel Estimation for Downlink Massive MIMO-OTFS Systems in Presence of the Fractional Doppler

TL;DR

This paper introduces a novel downlink channel estimation scheme for massive MIMO-OTFS systems affected by fractional Doppler, utilizing deterministic pilot design and a modified sensing matrix algorithm to improve accuracy and reduce overhead in high-mobility scenarios.

Contribution

It proposes a new CSI acquisition method with deterministic pilot design and a modified sensing matrix algorithm tailored for fractional Doppler in massive MIMO-OTFS systems.

Findings

Significant reduction in pilot overhead.

Enhanced channel estimation accuracy.

Superior performance over traditional algorithms.

Abstract

Although the combination of the orthogonal time frequency space (OTFS) modulation and the massive multiple-input multiple-output (MIMO) technology can make communication systems perform better in high-mobility scenarios, there are still many challenges in downlink channel estimation owing to inaccurate modeling and high pilot overhead in practical systems. In this paper, we propose a channel state information (CSI) acquisition scheme for downlink massive MIMO-OTFS in presence of the fractional Doppler, including deterministic pilot design and channel estimation algorithm. First, we analyze the input-output relationship of the single-input single-output (SISO) OTFS based on the orthogonal frequency division multiplexing (OFDM) modem and extend it to massive MIMO-OTFS. Moreover, we formulate an accurate model for the practical system in which the fractional Doppler is considered and the influence of subpaths is revealed. A deterministic pilot design is then proposed based on the model and the structure of the pilot matrix to reduce pilot overhead and save memory consumption. Since channel geometry changes very slowly relative to the communication timescale, we put forward a modified sensing matrix based channel estimation (MSMCE) algorithm to acquire the downlink CSI. Simulation results demonstrate that the proposed downlink CSI acquisition scheme has significant advantages over traditional algorithms.