Multi-beam Precoder Codebook Overhead Reduction
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Solution Overview
Problem
Existing multi-user MIMO systems face challenges in accurately estimating and reducing interference between co-scheduled users, leading to poor performance due to high CSI feedback overhead and complex precoder search processes.
Innovation Solution
A method for determining a precoder from a multi-beam precoder codebook is provided, where the granularity of co-phasing factors is optimized based on beam strength, with weaker beams having lower granularity, and frequency granularity being a multiple of subband size, to reduce feedback overhead while maintaining performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multi-beam precoder codebook is used to improve MU-MIMO performance, then interference reduction and user throughput are improved, but CSI feedback overhead and precoder search complexity increase
Solution Approach 1:
The patent segments the precoder selection process into two independent stages: first selecting a beam pair indicator (BPI) from a reduced set of beam pairs, then selecting a co-phasing factor from a codebook. This segmentation reduces the overall search space and feedback overhead while maintaining MU-MIMO performance through the structured approach of beam pair selection followed by phase adjustment.
Solution Approach 2:
The patent applies different granularity levels for co-phasing factors based on beam strength characteristics. Weaker beams use lower granularity (fewer phase options) while stronger beams use higher granularity (more phase options), optimizing the balance between feedback overhead and performance by allocating resources according to local beam quality requirements.
2Measurement precision
If fine granularity co-phasing factors are used for all beams, then precoding accuracy is improved, but feedback overhead increases significantly
Solution Approach 1:
The patent implements variable granularity for co-phasing factors where each beam is assigned a granularity level based on its strength. Stronger beams receive finer granularity (more phase quantization levels) to maintain precision, while weaker beams use coarser granularity to reduce feedback overhead. This local quality approach ensures adequate precision where needed while minimizing overall overhead.
Solution Approach 2:
The patent changes the granularity parameter of co-phasing factors dynamically based on beam strength conditions. By adjusting the number of phase quantization levels according to beam characteristics, the system optimizes the trade-off between precoding accuracy and feedback overhead, using more bits for strong beams and fewer bits for weak beams.
Data Source
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AI summary
A method, wireless device and network node for determining an indication of a precoder are provided. According to one aspect, a method in a wireless device includes determining and the indication of the precoder from a codebook, the indication comprising a first beam phase parameter and a second beam phase parameter corresponding to a first beam and a second beam respectively. The first beam phase parameter takes on one of a first integer number of phase values and the second beam phase parameter takes on one of a second integer number of phase values. At least one of the following conditions apply: the second integer number of phase values is less than the first number of phase values, and the second frequency-granularity is greater than the first frequency-granularity. The method includes transmitting the determined indication of a precoder to the network node. According to another aspect, the second beam has less power than the first beam and the second integer number of phase values is less than the first integer number of phase values.