Time-Domain DMRS Sequence Generation for Low PAPR Uplink
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Solution Overview
Problem
Current wireless communication systems, particularly in 5G NR, face challenges in efficiently selecting and transmitting demodulation reference signals (DMRS) for uplink transmissions, which affects the orthogonality and correlation properties of DMRS sequences, leading to suboptimal performance in multi-user multiplexing scenarios.
Innovation Solution
A method is introduced where a UE generates and transmits a time-domain based DMRS sequence, modulates it using π/2-BPSK or 8-PSK, and maps the symbols to subcarriers, employing specific schemes like circular shifts and orthogonal masks to ensure orthogonality and low Peak-to-Average Power Ratio (PAPR), thereby supporting multiple user multiplexing and improving channel estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional DMRS sequences are used in uplink transmissions, then the DMRS can be transmitted, but the orthogonality and correlation properties deteriorate in multi-user multiplexing scenarios
Solution Approach 1:
The patent applies parameter changes by modifying the DMRS sequence generation parameters specifically for uplink transmissions. The base sequence is generated with parameters optimized for uplink characteristics, and circular shifts are applied to create orthogonal variations. This allows multiple users to multiplex their DMRS signals while maintaining orthogonality and correlation properties, resolving the contradiction between reliable sequence properties and multi-user adaptability.
2Measurement precision
If DMRS sequences are designed for high orthogonality, then channel estimation improves, but the Peak-to-Average Power Ratio (PAPR) increases
Solution Approach 1:
The patent applies local quality by using π/2-BPSK modulation specifically for the DMRS symbols in uplink transmissions. This modulation scheme maintains constant envelope properties that keep PAPR low, while still providing sufficient orthogonality through circular shifts and base sequence design. The localized application of this modulation to DMRS symbols allows high channel estimation accuracy without the penalty of high PAPR that would affect the entire transmission.
3Productivity
If multiple users multiplex DMRS signals, then system capacity increases, but sequence orthogonality deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the DMRS resource space into multiple orthogonal dimensions. Base sequences are segmented into different groups, and circular shifts are applied to create orthogonal variations within each group. This segmented approach allows multiple users to multiplex their DMRS signals across different orthogonal dimensions (different base sequences and/or different circular shifts), thereby increasing system capacity while maintaining sequence orthogonality through the structured segmentation of the resource space.
Data Source
AI summary
In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be a UE. The UE receives an indication for transmitting a particular DMRS sequence in an uplink transmission. The particular DMRS sequence is time domain based. The UE generates the particular DMRS sequence. The UE modulates the particular DMRS sequence to obtain a set of symbols. The UE maps a plurality of symbols of the set of symbols to a plurality of subcarriers. The UE transmits the plurality of symbols on the plurality of subcarriers.