Multi-Antenna UE Precoder Restriction for Lower DCI Overhead
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Solution Overview
Problem
Current NR UL transmission schemes face challenges in supporting multi-antenna UEs, particularly with the introduction of up to 8 antenna ports, as they result in a large DCI overhead for signaling precoding matrices and transmission ranks.
Innovation Solution
The proposed solution involves restricting the set of possible precoding matrices for multi-antenna UEs by defining a subset of precoders based on UE capability and antenna configuration. This is achieved through predetermined rules, RRC or MAC CE configurations, or explicit DCI indications, thereby reducing the DCI overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the set of all possible precoding matrices is used for multi-antenna UEs, then the precoding capability and adaptability are improved, but the DCI overhead increases significantly
Solution Approach 1:
The patent segments the complete set of precoding matrices into multiple subsets based on different criteria (e.g., antenna port groups, coherence characteristics). Instead of signaling the full set, the system signals which subset is active, thereby reducing DCI overhead while maintaining the ability to adapt to different UE capabilities and channel conditions through proper subset selection.
Solution Approach 2:
The patent applies different precoding matrix subsets to different antenna port groups or spatial layers based on local channel characteristics and coherence properties. This allows the system to optimize precoding for each local region (antenna group) while using a manageable subset of matrices overall, balancing adaptability with signaling efficiency.
2Measurement precision
If a large codebook of precoding matrices is configured, then the precision of channel representation is improved, but the complexity of DCI processing increases
Solution Approach 1:
The patent extracts only the necessary subset of precoding matrices from the full codebook based on UE capability indicators and channel conditions. By removing irrelevant precoding options and signaling only the active subset, the system maintains sufficient channel representation precision while dramatically reducing DCI processing complexity at both transmitter and receiver.
Solution Approach 2:
The patent dynamically adjusts the size and composition of the precoding matrix subset based on real-time UE capability reporting and channel conditions. This dynamic adaptation allows the system to use a large codebook when high precision is needed and a small subset when simplicity is required, optimizing the trade-off between precision and complexity for each transmission scenario.
3Adaptability or versatility
If all antenna ports are treated independently, then the flexibility of precoding is improved, but the DCI signaling size increases
Solution Approach 1:
The patent merges antenna ports into groups (e.g., antenna port groups of 2 or more ports) and applies unified precoding decisions to each group rather than independently to each port. This merging reduces the number of separate precoding indicators needed in DCI, thereby reducing signaling size while maintaining flexibility through proper group formation and subset selection.
Solution Approach 2:
The patent creates a universal precoding framework where a single precoding matrix or subset can be applied to multiple antenna port groups simultaneously. This multi-functionality allows the system to maintain precoding flexibility across different antenna configurations while using a compact DCI signaling format that works universally for various UE capabilities and antenna setups.
Data Source
AI summary
There is provided method performed by a user equipment (UE) configured with 8 or more transmit antenna ports (NTX). The method comprises: receiving a precoding indication which indicates a precoder in a subset of precoders, where the subset of precoders corresponds to a plurality of precoders associated with NTX/Ng transmit antenna ports, where Ng is a number of transmit antenna port groups; and transmitting a data transmission using the indicated precoder to a network node. A UE to perform this method is also provided.