Cubic Metric Reduction for Repetitive CAZAC Sequences in frequency domain

TL;DR

This paper proposes new methods to reduce cubic metric in CAZAC sequences used in 5G NR unlicensed spectrum channels, improving performance while maintaining sequence properties.

Contribution

The paper introduces novel cubic metric reduction mechanisms tailored for CAZAC sequences in 5G NR PRACH and PUCCH channels, balancing performance and complexity.

Findings

Proposed CM reduction schemes effectively lower cubic metric values.

Optimized parameters enhance sequence performance with manageable complexity.

Methods maintain auto-correlation and cross-correlation properties.

Abstract

In NR-based Access to Unlicensed Spectrum (NR-U) of 5G system, to satisfy the rules of Occupied Channel Bandwidth (OCB) of unlicensed spectrum, the channels of PRACH and PUCCH have to use some sequence repetition mechanisms in frequency domain. These repetition mechanisms will cause serious cubic metric(CM) problems for these channels, although these two types of channels are composed of Constant Amplitude Zero Auto-correlation(CAZAC) sequences.. Based on the characteristics of CAZAC sequences, which are used for PRACH and PUCCH (refer to PUCCH format 0 and format 1) in 5G NR, in this paper, we propose some new mechanisms of CM reduction for these two types of channels considering the design principles to ensure the sequence performance of the auto-correlation and cross-correlation. Then the proposed CM schemes are evaluated and the optimized parameters are further provided considering CM performance and the complexity.