UL DMRS Sequence Selection for PAPR Reduction in 5G Wireless
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Solution Overview
Problem
In 5G wireless communication systems, the peak-to-average power ratio (PAPR) of uplink (UL) demodulation reference signals (DMRS) using QPSK modulation limits UL coverage improvement due to higher PAPR compared to pi/2 BPSK, and existing systems face challenges in seamlessly supporting both Rel-15 and Rel-16 reference signals for terminals and base stations.
Innovation Solution
The method involves identifying and using sequences with specific PAPR characteristics for pi/2 BPSK modulation in UL DMRS, allowing for the selection between Rel-15 and Rel-16 DMRS sequences based on transform precoding and modulation indications, ensuring compatibility and coverage enhancement by configuring appropriate DMRS sequences for UL transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If QPSK modulation is used for UL DMRS, then compatibility with existing systems is maintained, but PAPR increases limiting UL coverage improvement
Solution Approach 1:
The patent changes the modulation parameter from QPSK to pi/2 BPSK for UL DMRS transmission. This parameter change reduces the PAPR of the reference signal, thereby improving uplink coverage while maintaining compatibility through configurable indicators that allow existing QPSK-based systems to continue operating.
2Reliability
If pi/2 BPSK modulation is used for UL DMRS, then PAPR is reduced improving UL coverage, but compatibility with Rel-15 terminals becomes challenging
Solution Approach 1:
The patent introduces dynamic configurability through indicators that allow the system to switch between QPSK and pi/2 BPSK modulation for UL DMRS. This dynamic approach enables the system to adapt to different terminal types (Rel-15 and Rel-16), allowing pi/2 BPSK to be used for coverage enhancement when supported, while maintaining backward compatibility with existing terminals.
Solution Approach 2:
The patent changes the modulation parameter from QPSK to pi/2 BPSK for UL DMRS transmission. This parameter change reduces the PAPR of the reference signal, thereby improving uplink coverage while maintaining compatibility through configurable indicators that allow existing QPSK-based systems to continue operating.
3Productivity
If transform precoding is applied to PUSCH, then spectral efficiency improves, but system complexity increases requiring coordinated DMRS configuration
Solution Approach 1:
The patent implements a feedback mechanism where the base station sends an indicator to the terminal regarding the application of transform precoding to PUSCH. This feedback enables coordinated configuration of DMRS modulation (QPSK or pi/2 BPSK) based on the precoding state, allowing the system to achieve spectral efficiency improvements while managing complexity through standardized signaling procedures.
Data Source
AI summary
A method, performed by a user equipment (UE), of transmitting an uplink (UL) reference signal in a wireless communication system is provided. The method includes receiving first information indicating whether to apply transform precoding and pi/2 binary phase shift keying (BPSK) modulation to a physical uplink shared channel (PUSCH), receiving second information indicating whether to apply the pi/2 BPSK modulation to an UL demodulation reference signal (DMRS), and identifying a sequence having characteristics of a first peak-to-average power ratio (PAPR) based on the first information and the second information.