Uplink DMRS Sequence Design for Low PAPR in 5G NR

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current 5G wireless systems face challenges in reducing the peak-to-average-power-ratio (PAPR) of demodulation reference signals (DMRS) for pi/2 BPSK modulation in DFT-S-OFDM based PUSCH/PUCCH, leading to degraded performance compared to data symbols, especially with pulse shaping.

Innovation Solution

The proposed solution involves designing new DMRS sequences with low PAPR by using computer-generated sequences (CGS) and Gold Code-based sequences for specific resource allocations, which are generated in the time domain and mapped to pi/2 BPSK constellation, followed by DFT-spreading and OFDM symbol generation, to minimize cross-correlation and PAPR.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional DMRS sequences are used for pi/2 BPSK modulation in DFT-S-OFDM, then the DMRS can be generated with standard sequences, but the PAPR of DMRS becomes higher than data symbols, degrading performance

Engineering Contradiction:

ImproveDMRS performanceVSAvoidPAPR

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The patent changes the fundamental parameters of the DMRS sequence design by using computer-generated sequences with specific mathematical properties (constant modulus, low autocorrelation) instead of conventional sequences. This parameter change in sequence generation methodology directly reduces PAPR while maintaining reliability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies different sequence generation strategies for different resource allocation scenarios (small resource allocation uses one CGS approach, large resource allocation uses another), optimizing local properties for each case to achieve low PAPR specifically where needed for pi/2 BPSK modulation

Inventive Principle:

Principle #3Local quality

2Stress or pressure

If computer-generated sequences are designed with specific properties, then PAPR is reduced to the same level as data symbols, but the sequence design complexity increases

Engineering Contradiction:

ImprovePAPRVSAvoidsequence design

Core Design Contradiction:

Stress or pressureVSDevice complexity

Solution Approach 1:

The patent pre-generates sequences with desired properties (constant modulus, low autocorrelation) before transmission. This preliminary design phase creates lookup tables or pre-computed sequences that can be directly applied during transmission, reducing real-time complexity while achieving low PAPR

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses computer-generated sequences that replicate the favorable properties of ideal low-PAPR waveforms. These CGS serve as templates or copies of optimal sequence structures that can be systematically generated and applied across different scenarios

Inventive Principle:

Principle #26Copying

Data Source

PatentUS11190329B2Uplink low-PAPR DMRS sequence design

Publication Date: 2021.11.30 INTEL CORP

AI summary

An apparatus of user equipment (UE) includes processing circuitry coupled to a memory, where to configure the UE for DMRS processing in an NR network, the processing circuitry is to generate a plurality of binary sequences of length L, the binary sequences being arranged according to a signal quality metric. A set of CGSs is generated using the binary sequences, based on minimizing cross-correlation between subsets of binary sequences of different lengths selected from the plurality of binary sequences. A CGS is selected from the set of CGSs as a DMRS, based on uplink PRB resource allocation. The DMRS is encoded for transmission, where the encoding includes BPSK modulation and discrete Fourier transformation (DFT) spreading of the DMRS.