Analysis of Discrete-Time MIMO OFDM-Based Orthogonal Time Frequency Space Modulation

TL;DR

This paper provides a discrete-time analysis of MIMO OFDM-based OTFS, revealing capacity equivalence with OFDM and enabling practical low-complexity receiver design for high Doppler channels.

Contribution

It introduces a novel discrete-time vectorized formulation of MIMO OTFS, clarifying signal processing contributions and facilitating low-complexity receiver development.

Findings

MIMO OTFS and OFDM have the same ergodic capacity with cyclic prefix.

The analysis applies to general fast fading channels with arbitrary window functions.

The formulation enables practical low-complexity receiver design.

Abstract

Orthogonal Time Frequency Space (OTFS) is a novel modulation scheme designed in the Doppler-delay domain to fully exploit time and frequency diversity of general time-varying channels. In this paper, we present a novel discrete-time analysis of OFDM-based OTFS transceiver with a concise and vectorized input-output relationship that clearly characterizes the contribution of each underlying signal processing block in such systems. When adopting cyclic prefix in the time domain, our analysis reveals that the proposed MIMO OTFS and OFDM systems have the same ergodic capacity despite the well-known fact that the former has great advantages in low-complexity receiver design for high Doppler channels. The proposed discrete-time vectorized formulation is applicable to general fast fading channels with arbitrary window functions. It also enables practical low-complexity receiver design for which such a concise formulation of the input-output relationship is of great benefits.