OTFS Based Random Access Preamble Transmission For High Mobility Scenarios

TL;DR

This paper introduces an OTFS-based random access preamble for high mobility scenarios, enabling robust uplink timing synchronization by estimating delay-Doppler parameters, outperforming 4G methods in Doppler-rich environments.

Contribution

It proposes a novel OTFS-based RA preamble and delay estimation method, improving timing synchronization robustness in high mobility conditions.

Findings

OTFS preamble enhances timing error probability in high Doppler scenarios.

The method outperforms 4G RA in multi-path Doppler environments.

Parameter analysis guides optimal OTFS configuration for synchronization.

Abstract

We consider the problem of uplink timing synchronization for Orthogonal Time Frequency Space (OTFS) modulation based systems where information is embedded in the delay-Doppler (DD) domain. For this, we propose a novel Random Access (RA) preamble waveform based on OTFS modulation. We also propose a method to estimate the round-trip propagation delay between a user terminal (UT) and the base station (BS) based on the received RA preambles in the DD domain. This estimate (known as the timing advance estimate) is fed back to the respective UTs so that they can advance their uplink timing in order that the signal from all UTs in a cell is received at the BS in a time-synchronized manner. Through analysis and simulations we study the impact of OTFS modulation parameters of the RA preamble on the probability of timing error, which gives valuable insights on how to choose these parameters. Exhaustive numerical simulations of high mobility scenarios suggests that the timing error probability (TEP) performance of the proposed OTFS based RA is much more robust to channel induced multi-path Doppler shift when compared to the RA method in Fourth Generation (4G) systems.