UL DM-RS Overhead Reduction in LTE Uplink
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Solution Overview
Problem
In LTE communication systems, the uplink DM-RS overhead is excessive, consuming unnecessary uplink spectrum and limiting the number of transmissions in UL subframes, necessitating a reduction in DM-RS overhead to balance DM-RS and shared data channel reliability.
Innovation Solution
A method and apparatus that determine whether to apply a DM-RS overhead reduction scheme for an uplink subframe, identify a UCI transmission scheme based on the scheme application, and transmit UCI in the subframe using the identified scheme, which may involve reducing the number of DM-RS symbols, adjusting the number of UCI in the shared channel, and configuring the DM-RS and UCI transmission to optimize resource usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of UL DM-RS is increased to improve reliability of the shared data channel, then the reliability is improved, but the uplink spectrum consumption increases and the number of transmissions is limited
Solution Approach 1:
The patent changes the parameter of DM-RS configuration by introducing a parameter indicator that can take different values (e.g., 0 or 1) to select between different DM-RS patterns. This allows dynamic adjustment of DM-RS density and positioning in the time-frequency grid, enabling the system to optimize between reliability and spectrum efficiency based on channel conditions and traffic requirements
Solution Approach 2:
The patent makes the DM-RS configuration dynamic by allowing the parameter indicator to be signaled through downlink control information (DCI), enabling real-time adaptation of DM-RS patterns according to varying channel conditions, mobility scenarios, and traffic types. This dynamic approach replaces static fixed DM-RS configurations with flexible, condition-based patterns
2Quantity of substance
If the number of UL DM-RS is reduced to decrease uplink overhead, then the uplink spectrum efficiency is improved, but the reliability of the shared data channel deteriorates
Solution Approach 1:
The patent employs parameter changes by defining multiple DM-RS patterns with different densities and positions, selected through a parameter indicator. When overhead reduction is needed, the system can select patterns with fewer DM-RS symbols or sparser distribution, thereby reducing uplink overhead while maintaining adequate reliability through intelligent pattern selection rather than uniform reduction
Solution Approach 2:
The patent applies local quality by allowing different DM-RS patterns in different time-frequency resources or for different users. Instead of uniformly reducing DM-RS across the board, the system can apply reduced DM-RS patterns only in specific regions or for specific traffic types where full DM-RS density is not critical, thereby locally optimizing overhead reduction while preserving reliability where needed
3Productivity
If the DM-RS overhead is reduced to increase the number of transmissions in UL subframe, then the productivity is improved, but the complexity of coordinating UCI transmission increases
Solution Approach 1:
The patent applies segmentation by separating the determination of DM-RS pattern selection from UCI transmission coordination. The parameter indicator segments the control information, allowing the DM-RS pattern to be determined independently based on channel conditions, while UCI transmission resources are allocated separately. This segmentation simplifies the overall coordination complexity by breaking down the joint optimization problem into independent sub-problems
Data Source
AI summary
In certain circumstances, the uplink resources (e.g., overhead) used for transmission of the UL DM-RS may be excessive, consuming an unnecessary amount of the available uplink spectrum. While there is a balance between the number of DM-RS and the reliability of the shared data channel, reduction of the UL DM-RS overhead may enable the UE to increase the number of transmissions in a UL subframes. Various DM-RS reduction techniques discussed include reducing the number of UL DM-RS generally, per resource block, or per pairs of resource units, and accommodating transmission of uplink control channel information when UL DM-RS is reduced. Further disclosed techniques relate to adjusting the number of UCI in the uplink shared channel.