Dual Codebook Structure for 4Tx MIMO Beam Granularity
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Solution Overview
Problem
Current downlink multiple-input multiple-output (DL-MIMO) systems with 8Tx codebooks have limitations in beam granularity and support, particularly for ranks 3 and 4, and are not optimally robust across different propagation scenarios, leading to suboptimal performance in various communication systems.
Innovation Solution
A dual codebook structure is used for 4Tx systems, where the first codebook is constructed using a rotation matrix and a construction matrix with design parameters θ, α, and β, allowing for improved beam selection and co-phasing, and the second codebook is defined similarly to the LTE Rel.-10 8Tx codebook, enhancing performance for different propagation conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If 8Tx codebook is used for 4Tx systems, then codebook support is available, but beam granularity is insufficient and performance is suboptimal
Solution Approach 1:
The patent segments the codebook selection process into two independent parts: W1 for beam selection and W2 for co-phasing. This segmentation allows independent optimization of beam granularity (through W1 with 16 beams) while maintaining codebook support, resolving the contradiction between having codebook support and achieving fine beam granularity.
Solution Approach 2:
The patent introduces a dual-codebook structure that adds a new dimension to the codebook design. Instead of using a single codebook with limited granularity, it uses the product of two codebooks (W = W1 × W2), where W1 provides beam selection in one dimension and W2 provides co-phasing in another dimension, achieving both codebook support and fine beam granularity.
2Ease of manufacture
If simple downscaling of 8Tx codebooks is used for 4Tx systems, then implementation is simple, but robustness across propagation scenarios is reduced
Solution Approach 1:
The patent applies local quality by making the codebook structure adaptive to different propagation scenarios. The dual-codebook structure with configurable parameters allows the system to optimize W1 and W2 separately for different channel conditions, achieving both implementation simplicity and robustness across diverse propagation scenarios.
Solution Approach 2:
The patent uses parameter changes to enhance robustness. By introducing configurable parameters in the W1 and W2 codebooks, the system can adapt to different propagation scenarios (line-of-sight, non-line-of-sight, urban, rural) while maintaining a relatively simple dual-codebook structure, thus achieving both simplicity and adaptability.
3Manufacturing precision
If dual codebook structure with design parameters is used, then beam granularity and robustness are improved, but system complexity increases
Solution Approach 1:
The patent segments the complex codebook design into two manageable components: W1 for beam selection and W2 for co-phasing. This segmentation reduces the perceived complexity by allowing independent design and optimization of each component, achieving fine beam granularity while keeping the overall structure manageable through clear functional separation.
4Reliability
If beam granularity for ranks 3 and 4 is different from ranks 1 and 2, then rank-specific optimization is achieved, but codebook design complexity increases
Solution Approach 1:
The patent applies local quality by allowing different beam granularities for different ranks through the W1 codebook design. Each rank can have optimized beam selection characteristics while using the same dual-codebook structure, achieving rank-specific performance optimization without fundamentally changing the overall codebook architecture, thus managing complexity.
Data Source
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AI summary
Various communication systems may benefit from codebook methods and devices for multiple transmitters. For example, a codebook for four transmitters (4Tx) may provide further enhancement for downlink multiple-input multiple-output (DL-MIMO) systems. A method can include weighting a signal for transmission based on a precoder selected according to a feedback from a codebook, such as codebooks A, B, C, D, or E, described herein. The method can also include sending the weighted signal.