Hybrid Codebook for MU-MIMO Interference Reduction
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Solution Overview
Problem
Current MU-MIMO systems face limitations in multi-base station environments due to interference and increased system complexity, with existing beamforming methods like PU2RC and ZFBF having opposite advantages and disadvantages, such as requiring more feedback bits or receivers to achieve superior performance.
Innovation Solution
A hybrid codebook is generated using a parent matrix set of unitary matrices and a child matrix set, where the parent matrix set is used for beamforming vector selection and the child matrix set provides additional channel quality information, reducing computational complexity and interference by combining the benefits of both PU2RC and ZFBF schemes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If ZFBF scheme is used to eliminate interference between receivers, then interference is reduced to zero, but the number of feedback bits is increased and system complexity is increased
Solution Approach 1:
The codebook is segmented into two distinct parts: a first codebook for beamforming vector selection and a second codebook for channel quality information. This segmentation allows the system to separately optimize for interference elimination and feedback efficiency, avoiding the need for a single large codebook that increases complexity.
Solution Approach 2:
The patent extracts the channel quality information function from the beamforming vector selection function. By taking out the CQI selection as a separate codebook, the system reduces the feedback burden on individual users while maintaining the interference elimination capability of ZFBF through the first codebook.
2Measurement precision
If codebook size is increased to improve beamforming accuracy, then beamforming performance is improved, but feedback overhead and system complexity are increased
Solution Approach 1:
The codebook is divided into two parts with different sizes and functions. The first codebook contains beamforming vectors for accurate spatial processing, while the second codebook contains channel quality indicators. This segmentation allows the system to maintain high beamforming accuracy without requiring all users to feedback information from a single large codebook.
Solution Approach 2:
Instead of requiring all users to provide feedback from a large unified codebook, the patent applies partial action by having users selectively feedback from the two separate codebooks. This reduces the overall feedback overhead while maintaining sufficient accuracy for beamforming operations.
Data Source
AI summary
A method for generating a hybrid codebook for a Multi-User Multiple-input Multiple-Output (MU-MIMO) system includes the steps of: generating a parent matrix set including a plurality of M×M unitary matrices when the number of transmitter antennas is M; and generating a child matrix set dependent on the parent matrix set by using training vectors included in a random training set and each column for each unitary matrix of the parent matrix set as an initial vector codebook.