DMRS Overhead Reduction via Orthogonal Code Patterns
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Solution Overview
Problem
Current LTE systems face high demodulation reference signal (DMRS) overhead, especially for rank 3 and rank 4 transmissions, which increases channel estimation complexity and resource usage, limiting efficiency and mobility support.
Innovation Solution
Implementing a method to transmit DMRSs using orthogonal codes of length 4 across 12 resource elements per physical resource block for rank 3 and rank 4 transmissions, reducing overhead by half compared to conventional methods, and specifying these settings in downlink control messages or lookup tables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional DMRS configuration is used for rank 3 and rank 4 transmissions, then channel estimation can be performed, but DMRS overhead is high and resource utilization is inefficient
Solution Approach 1:
The patent combines multiple DMRS configurations into unified lookup tables that define resource element patterns for different transmission ranks. By merging the configuration logic into pre-defined patterns with orthogonal codes of length 4, the system reduces DMRS overhead while maintaining channel estimation accuracy through optimized resource element allocation.
Solution Approach 2:
The patent changes the DMRS configuration parameters by specifying orthogonal codes of length 4 and defining specific resource element patterns in the lookup tables. These parameter changes enable reduced overhead configurations for rank 3 and rank 4 transmissions while preserving the necessary channel estimation capabilities through optimized parameter selection.
2Measurement precision
If more resource elements are allocated to DMRS, then channel estimation accuracy improves, but resource utilization for data transmission decreases
Solution Approach 1:
The patent optimizes resource utilization by changing the DMRS configuration parameters to use orthogonal codes of length 4 and specific resource element patterns. This allows adequate channel estimation accuracy to be achieved with fewer resource elements dedicated to DMRS, thereby increasing the number of resource elements available for data transmission and improving overall resource utilization.
Solution Approach 2:
The patent applies local quality optimization by defining specific resource element patterns in the lookup tables that allocate DMRS resources strategically. Different patterns are defined for different transmission ranks, optimizing the local distribution of DMRS resources to achieve necessary estimation accuracy while minimizing the impact on data transmission resources.
3Measurement precision
If different orthogonal cover code schemes are used for different antenna ports, then channel estimation accuracy varies, but configuration complexity increases
Solution Approach 1:
The patent applies universality by creating unified lookup tables that serve multiple antenna port configurations. The same lookup table structure and orthogonal code length (4) are used across different transmission ranks and antenna ports, providing a universal configuration mechanism that simplifies complexity while maintaining the ability to achieve appropriate channel estimation accuracy for each configuration through pattern selection.
4Quantity of substance
If DMRS overhead is reduced, then resource utilization improves, but channel estimation complexity may increase
Solution Approach 1:
The patent applies preliminary action by pre-defining optimized DMRS resource element patterns in lookup tables before transmission. These pre-configured patterns with orthogonal codes of length 4 are designed to minimize overhead while maintaining estimation efficiency. The UE can directly apply these pre-defined patterns without performing complex real-time optimization, thereby reducing channel estimation complexity despite reduced overhead.
Data Source
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AI summary
An embodiment method defines a demodulation reference signal (DMRS) pattern for transmitting DMRSs for rank 3 or rank 4 transmissions. The DMRS pattern specifies 12 REs in total per physical resource block (PRB) for carrying DMRSs on three or four antenna ports in antenna ports 7-14 for rank 3 or rank 4 transmissions. DMRS settings for transmitting DMRS according to the DMRS pattern may be specified using a downlink control information table.