Orthogonal DMRS Overhead Reduction via Time-First CCE-to-REG Mapping
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Solution Overview
Problem
Current wireless communication systems, particularly 5G NR, face challenges in reducing signal overhead for downlink control channels while maintaining channel estimation quality, especially in multi-user multiple-input multiple-output (MU-MIMO) scenarios, where orthogonal demodulation reference signals (DMRSs) lead to high overhead.
Innovation Solution
Implementing orthogonal DMRSs via frequency division multiplexing (FDM), code division multiplexing (CDM), and time division multiplexing (TDM) across multiple symbols for downlink control channels, which reduces overhead without degrading channel estimation quality by using time-first CCE-to-REG mapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If orthogonal DMRSs are used for MU-MIMO downlink control channels, then channel estimation quality is improved, but signal overhead increases
Solution Approach 1:
The control channel is divided into multiple control channel elements (CCEs), each containing multiple resource element groups (REGs). DMRS resources are segmented and assigned to different CCEs/REGs, allowing orthogonal DMRS to be distributed across multiple symbols rather than concentrated in one location, thereby reducing peak overhead while maintaining estimation quality
Solution Approach 2:
The patent introduces time dimension by using time-first CCE-to-REG mapping, where CCEs are mapped to REGs across multiple time symbols. This temporal distribution of DMRS resources reduces the concentration of reference signals in frequency domain, effectively reducing overhead while preserving channel estimation capability through time-diversity
2Measurement precision
If orthogonal DMRSs are used for MU-MIMO downlink control channels, then spectral efficiency is reduced due to high overhead, but channel estimation quality improves
Solution Approach 1:
The patent implements dynamic DMRS resource allocation based on the number of CCEs allocated to a PDCCH. The DMRS pattern adapts to the control channel size: for smaller CCE allocations, fewer DMRS resources are used, while larger allocations receive more DMRS resources. This dynamic approach optimizes the trade-off between overhead and estimation quality, improving spectral efficiency
Solution Approach 2:
The patent changes the DMRS resource allocation parameters based on the control channel configuration. By adjusting the number and position of DMRS resources according to the CCE-to-REG mapping and control channel size, the system optimizes spectral efficiency while maintaining adequate channel estimation quality for MU-MIMO operations
Data Source
AI summary
Various aspects described herein relate to techniques for using orthogonal demodulation reference signals (DMRSs) for downlink control channels in wireless communications systems. In an aspect, a method for a user equipment (UE) includes receiving one or more DMRSs over a multi-symbol downlink control channel. The method may further include identifying a time-first control channel element (CCE)-to-resource element group (REG) mapping for the multi-symbol downlink control channel, and identifying an orthogonal DMRS of the one or more DMRSs based on the time-first CCE-to-REG mapping, and decoding the multi-symbol downlink control channel based on at least the identified orthogonal DMRS.