Antenna Grouping for FD-MIMO Channel Feedback Reduction
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Solution Overview
Problem
In Full Dimension Multiple Input Multiple Output (FD-MIMO) communication systems, the increase in the number of transmission antennas leads to a higher dimension of channel vectors, resulting in increased channel feedback load, which complicates beamforming and reduces the accuracy of channel state information, thereby deteriorating the Signal to Interference and Noise Ratio (SINR) and limiting the sum rate due to the finite number of feedback bits.
Innovation Solution
The method involves grouping antennas to reduce the dimension of channel vectors through antenna grouping patterns, determining grouped codebook vectors, and feeding back pattern and codebook indices to minimize feedback load and improve beamforming accuracy, allowing for efficient channel state information feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of transmission antennas is increased to achieve high transmission rate, then the transmission rate is improved, but the feedback load significantly increases
Solution Approach 1:
The patent divides the large set of transmission antennas into multiple smaller antenna groups. Instead of quantizing the channel vector for all antennas individually, the system quantizes channel vectors for each antenna group separately. This segmentation reduces the dimensionality of each quantization problem, allowing the feedback load to grow more slowly with the total number of antennas while maintaining beamforming performance.
2Measurement precision
If the number of feedback bits is increased to maintain channel quantization accuracy, then the channel state information accuracy is improved, but the uplink overhead increases
Solution Approach 1:
The patent segments the channel quantization process into multiple independent quantizations of smaller antenna group vectors. Each group requires fewer feedback bits than the full channel vector, reducing total uplink overhead. The segmented approach maintains overall channel state accuracy by preserving the correlation structure within each antenna group while reducing the dimensionality of feedback requirements.
3Loss of information
If the number of feedback bits is reduced to decrease uplink overhead, then the uplink overhead is reduced, but the channel vector quantization accuracy deteriorates
Solution Approach 1:
By segmenting the antenna array into correlated groups, the patent enables reduced feedback bit allocation per group while maintaining overall quantization accuracy. The segmentation exploits spatial correlation within antenna groups to achieve efficient compression of channel state information with fewer feedback bits compared to uniform quantization of all antennas.
Solution Approach 2:
The patent applies different quantization strategies to different antenna groups based on their local correlation characteristics. Each antenna group is quantized independently with appropriate bit allocation, allowing the system to optimize the trade-off between feedback overhead and quantization accuracy locally for each group rather than using a uniform approach.
4Productivity
If complete channel state information is used to achieve optimal beamforming, then the sum rate is maximized, but the feedback load becomes unmanageable
Solution Approach 1:
The patent implements a segmented beamforming approach where the overall beamforming matrix is constructed from multiple group-level beamforming matrices. Each antenna group performs beamforming based on its quantized channel vector, and the combined effect approximates optimal full-channel beamforming. This segmentation enables sum rate performance close to complete channel state information while keeping feedback load manageable through reduced-dimensional quantization.
Data Source
AI summary
Disclosed are a method and an apparatus for grouping antennas in a multiple-input multiple-output antenna system. The method of the present invention comprises the steps of: measuring a channel vector for a plurality of antennas of a base station; grouping channel coefficients of the channel vector in accordance with a plurality of antenna grouping patterns and determining grouped codebook vectors corresponding to the grouped channel coefficients; selecting one of the antenna grouping patterns using the grouped codebook vectors for the antenna grouping patterns; and feeding back, to the base station, a pattern index indicating the selected antenna grouping pattern and a codebook index indicating the grouped codebook vector corresponding to the selected antenna grouping pattern.