Uplink DMRS Pattern Configuration for Code Rate Enhancement
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Solution Overview
Problem
Current LTE uplink data transmission systems experience increased overhead due to repetitive transmissions, leading to higher code rates and reduced spectral efficiency, especially with the use of Demodulation Reference Signals (DMRS) in subslot-based transmissions.
Innovation Solution
The implementation of pre-configured or dynamically indicated DMRS patterns for data repetition in uplink transmissions, allowing for reduced DMRS overhead by determining a reference signal pattern that includes fewer reference signals and optimizing their placement, enabling efficient data transmission with low block error rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DMRS are included in every subslot-based uplink transmission repetition, then channel estimation accuracy is improved, but overhead increases and code rate decreases
Solution Approach 1:
Multiple uplink transmission repetitions share a single common DMRS resource. Instead of placing DMRS in every repetition, the system combines the reference signal resources across K-1 repetitions, allowing one DMRS to serve multiple transmissions. This merging approach maintains channel estimation accuracy while significantly reducing the total number of DMRS resources required.
Solution Approach 2:
A single DMRS resource is designed to serve multiple functions across different transmission repetitions. The common DMRS placed in the first subslot is reused by subsequent repetitions, making one reference signal universal for multiple uplink transmissions. This multi-functionality reduces overhead while maintaining the ability to estimate channels for all repetitions.
2Productivity
If DMRS overhead is reduced by using fewer reference signals, then code rate improves and spectral efficiency increases, but channel estimation reliability may deteriorate
Solution Approach 1:
The system performs channel estimation using the common DMRS in the first subslot before subsequent data transmissions. By establishing the channel estimate early and reusing it for multiple repetitions, the system maintains reliable channel knowledge without requiring DMRS in every transmission. This preliminary action ensures reliability while improving spectral efficiency.
Solution Approach 2:
The channel estimation obtained from the common DMRS is continuously applied across multiple transmission repetitions. Instead of performing separate estimations for each repetition, the system maintains a continuous valid channel estimate that serves all K-1 repetitions, ensuring reliability throughout the transmission sequence while using fewer reference signals.
3Measurement precision
If reference signals are placed in every uplink repetition, then demodulation accuracy is maintained, but the proportion of data symbols decreases
Solution Approach 1:
The patent extracts the DMRS from individual repetition structures and consolidates it into a shared resource. By taking out the redundant reference signals from each repetition and combining them into a single common DMRS, the system maintains demodulation capability while increasing the proportion of symbols available for data transmission in each repetition.
4Reliability
If repetitive transmissions are implemented for reliability, then link robustness improves, but code rate overhead increases
Solution Approach 1:
The system merges the reference signal resources across multiple repetitive transmissions into a single common DMRS. This combining approach allows the system to maintain K-1 repetitive transmissions for link robustness while reducing the overhead associated with reference signals, thereby improving the effective code rate for data transmission.
Data Source
AI summary
According to some embodiments, a method is performed by a wireless device for transmitting uplink data. The method comprises determining a predetermined configuration according to which to transmit uplink data and one or more repetitions of the uplink data. The method further comprises determining a cyclic shift for one or more reference signals transmitted with the uplink data and the one or more repetitions of the uplink data. The method further comprises transmitting the uplink data, the one or more repetitions, and the one or more references signals to a network node. The uplink data and the one or more repetitions are transmitted according to the predetermined configuration. The one or more references signals are transmitted according to the cyclic shift.