Sub-sampled DMRS for PUSCH Repetitions
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Solution Overview
Problem
Current cellular wireless communication systems face challenges in managing signaling overhead, particularly with the use of DMRS in repeated mini-slots, which consumes significant resources and complicates channel estimation, especially in URLLC services requiring low latency and high reliability.
Innovation Solution
The implementation of sub-sampled DMRS patterns and dynamic signaling configurations, such as varying DMRS density and positions within mini-slots, reduces signaling overhead and improves resource allocation for data transmission, while maintaining decoding latency and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DMRS is transmitted in every repeated mini-slot, then channel estimation reliability is improved, but signaling overhead increases
Solution Approach 1:
The patent segments the DMRS transmission pattern by introducing different DMRS density configurations (first pattern with higher density, second pattern with lower density) that can be applied to different repeated mini-slots. This allows the system to divide the transmission into segments with varying DMRS overhead, rather than uniformly applying high-density DMRS to all repetitions.
Solution Approach 2:
The patent implements periodic variation in DMRS density by alternating between first and second DMRS patterns across repeated mini-slots. The gNB can configure the UE to switch between patterns in a periodic manner, providing channel estimation reliability at intervals while reducing overall signaling overhead during other periods.
2Reliability
If DMRS density is increased to improve decoding reliability for rapidly moving UEs, then decoding probability is improved, but resource availability for data transmission decreases
Solution Approach 1:
The patent applies local quality by using higher DMRS density (first pattern) only in specific repeated mini-slots where it is most needed, such as initial transmissions or transmissions in challenging channel conditions, while using lower DMRS density (second pattern) in other repetitions where the channel conditions are more stable or where data resources are more critical.
Solution Approach 2:
The patent implements partial action by not applying maximum DMRS density to all repeated mini-slots. Instead, it selectively applies high-density DMRS patterns only when necessary for decoding reliability, accepting that some repetitions will have lower DMRS density but compensating through diversity gain from multiple repetitions.
3Ease of operation
If consistent DMRS pattern is used across all repetitions, then channel estimation simplicity is improved, but adaptability to varying channel conditions deteriorates
Solution Approach 1:
The patent introduces dynamics by allowing the DMRS pattern to change across repeated mini-slots based on configured patterns. The gNB can signal to the UE which pattern to use in each repetition, enabling the system to adapt DMRS density dynamically to varying channel conditions, mobility levels, and traffic requirements while maintaining clear signaling rules for the UE.
Data Source
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AI summary
Sub-sampled DMRS are utilised in repeated mini-slots for PUSCH transmission. Each sub-sampled DMRS may be multiplex with data in the respective symbol.