Adaptive DMRS Pattern Nulling for Channel Estimation
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Solution Overview
Problem
In 5G NR systems, the cyclic prefix (CP) length is insufficient for higher numerologies, leading to inter-symbol interference (ISI) and inter-carrier interference (ICI), which degrades channel estimation accuracy and reduces spectrum efficiency, especially in non-line-of-sight environments and high-speed scenarios.
Innovation Solution
Adapting the DMRS pattern by nulling specific resource elements to form a comb structure, increasing the subcarrier spacing and reducing interference, thereby improving channel estimation and decoding processing, even in cases where the CP length is insufficient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the CP length is increased to cover excessive delay spread, then reliability is improved, but spectrum efficiency deteriorates due to increased overhead
Solution Approach 1:
The patent applies local quality by configuring different CP lengths for different UEs based on their specific channel conditions. Cell-edge UEs experiencing excessive delay spread are configured with extended CP, while other UEs use normal CP, thereby achieving reliable connections for affected UEs without system-wide spectrum efficiency degradation.
Solution Approach 2:
The patent introduces dynamic adaptability by allowing the network to switch between normal CP and extended CP configurations based on UE-specific channel conditions. This dynamic adjustment enables the system to optimize the trade-off between reliability and spectrum efficiency for each UE individually.
2Reliability
If the CP length is increased to improve cell-edge UE connections, then reliability is improved, but overhead increases resulting in lower spectrum efficiency
Solution Approach 1:
The patent implements local quality by applying extended CP configuration selectively only to cell-edge UEs that experience excessive delay spread, rather than system-wide. This localized application reduces the overall overhead in the system while maintaining reliable connections for affected UEs.
3Measurement precision
If advanced receivers such as time-domain channel shortening or iteratively interference-cancellation are applied, then measurement precision is improved, but device complexity increases and accurate channel estimates are required
Solution Approach 1:
The patent applies beforehand cushioning by configuring extended CP in advance for UEs experiencing excessive delay spread. This preventive measure protects the channel estimation from ISI and ICI corruption before advanced receiver processing is applied, reducing the complexity requirements and improving the effectiveness of subsequent channel estimation algorithms.
4Measurement precision
If DMRS pattern is adapted by nulling specific resource elements to form comb structure, then channel estimation accuracy is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by nulling specific resource elements in the DMRS pattern to form a comb structure. This segmentation of the DMRS resources in the frequency domain provides better channel estimation accuracy by reducing interference, while the structured comb pattern maintains manageable processing complexity through regular spacing.
Data Source
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AI summary
The invention relates to a network access node and a client device for adaptive DMRS. The network access node (100) transmits DMRS according to a first DMRS pattern in a radio channel to a client device (300), and upon determining that a delay spread of the radio channel exceeds a cyclic prefix length of the first DMRS pattern obtains a second DMRS pattern formed from the first DMRS pattern with one or more nulled resource elements associated with DMRSs. The network access node thereafter transmits DMRSs according to the second DMRS pattern to the client device (300). Thereby, a more robust DMRS pattern can be provided when the delay spread of the radio channel exceeds the cyclic prefix length. Hence, improved channel estimation is possible. Furthermore, the invention also relates to corresponding methods and a computer program.