DMRS Cover Code Mapping for More Antenna Ports
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Solution Overview
Problem
The existing 3GPP NR Rel-15 DMRS sequences support only 12 orthogonal cover codes, which is insufficient to support more antenna ports, limiting the capacity for future improvements.
Innovation Solution
Introduce a set of cover codes that ensure maximum correlation power between two cover codes is greater than 0 in each half PRB, allowing for more DMRS antenna ports by ensuring pair-wise orthogonality within each PRB, with specific formulas for generating these cover codes to maintain low interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If orthogonal cover codes are used to support multiple antenna ports, then the number of supported DMRS ports is limited to 12, but increasing the number of antenna ports is needed to improve system capacity
Solution Approach 1:
The patent divides each PRB into two half-PRBs and applies different correlation constraints to each half. Specifically, it allows maximum correlation power >0 in one half-PRB while maintaining orthogonality in the other half-PRB. This segmentation enables more DMRS ports (beyond the traditional 12) to be supported by relaxing constraints in a localized manner, thereby improving system capacity while maintaining acceptable interference levels
Solution Approach 2:
The patent applies different correlation properties to different regions (half-PRBs) of the frequency domain. Instead of requiring uniform orthogonality across the entire PRB, it allows non-zero correlation in specific half-PRB regions while maintaining orthogonality in other regions. This local differentiation enables increased DMRS port capacity by allowing more sequences to coexist with controlled interference only in specific localized regions
2Quantity of substance
If more DMRS antenna ports are supported, then data transmission capacity is improved, but interference between DMRS sequences increases
Solution Approach 1:
By segmenting the PRB into two half-PRBs and applying different correlation constraints to each, the patent localizes interference to specific regions. This allows more DMRS ports to be supported overall, while the interference between sequences is confined to localized half-PRB regions rather than affecting the entire frequency band, thereby managing interference levels while increasing capacity
Solution Approach 2:
The patent changes the correlation parameter constraints by allowing maximum correlation power >0 in one half-PRB while maintaining orthogonality in the other half-PRB. This parameter differentiation enables more DMRS ports to be supported while controlling interference through selective application of correlation constraints in different frequency regions
Data Source
AI summary
A first communication device determines a DMRS sequence based on a cover code in a set of cover codes; and thereafter determines a DMRS by mapping the DMRS sequence onto one or more PRBs. The cover code is dependent on a DMRS antenna port index, and cover codes in the set of cover codes are orthogonal to each other in each PRB, and wherein a maximum correlation power between two cover codes in the set of cover codes is larger than 0 in each half PRB. Finally, the first communication device transmits the DMRS via a DMRS antenna port having DMRS antenna port index to a second communication device which receive the DMRS and associated data signal. The second communication device demodulates the associated data signal based on the received DMRS and the DMRS sequence.