Performance Analysis of Coded OTFS Systems over High-Mobility Channels

TL;DR

This paper analyzes the error performance of coded OTFS modulation in high-mobility channels, revealing a fundamental trade-off between coding gain and diversity gain, and demonstrating significant performance improvements over OFDM.

Contribution

It provides a performance upper bound for coded OTFS, explores the trade-off between coding and diversity gains, and evaluates the impact of coding parameters through analysis and simulations.

Findings

Coded OTFS outperforms OFDM in high-mobility environments.

A fundamental trade-off exists between coding gain and diversity gain in OTFS.

Performance improvements are verified with classical and modern codes.

Abstract

Orthogonal time frequency space (OTFS) modulation is a recently developed multi-carrier multi-slot transmission scheme for wireless communications in high-mobility environments. In this paper, the error performance of coded OTFS modulation over high-mobility channels is investigated. We start from the study of conditional pairwise-error probability (PEP) of the OTFS scheme, based on which its performance upper bound of the coded OTFS system is derived. Then, we show that the coding improvement for OTFS systems depends on the squared Euclidean distance among codeword pairs and the number of independent resolvable paths of the channel. More importantly, we show that there exists a fundamental trade-off between the coding gain and the diversity gain for OTFS systems, i.e., the diversity gain of OTFS systems improves with the number of resolvable paths, while the coding gain declines. Furthermore, based on our analysis, the impact of channel coding parameters on the performance of the coded OTFS systems is unveiled. The error performance of various coded OTFS systems over high-mobility channels is then evaluated. Simulation results demonstrate a significant performance improvement for OTFS modulation over the conventional orthogonal frequency division multiplexing (OFDM) modulation over high-mobility channels. Analytical results and the effectiveness of the proposed code design are also verified by simulations with the application of both classical and modern codes for OTFS systems.