Analog Beamforming Codebook Design for Millimeter-Wave Systems
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Solution Overview
Problem
In millimeter-wave communication systems with a single RF chain, digital baseband beamforming is costly and power-intensive, making it challenging to access entry-wise elements of the channel, prompting the need for efficient analog beamforming codebook design.
Innovation Solution
A method for designing a codebook for analog beamforming involves generating training points, assigning them to codewords that maximize a beamforming gain metric, and updating codewords using a gradient descent rule, ensuring convergence and optimizing performance metrics like average beamforming gain and coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital baseband beamforming is used, then channel access precision is improved, but power consumption and cost increase
Solution Approach 1:
The patent segments the beamforming function into two parts: digital precoding for channel access (using a small number of RF chains) and analog beamforming for data transmission (using the full antenna array). This segmentation allows digital processing to be limited to only what is necessary for channel estimation, reducing power consumption while maintaining channel access precision.
Solution Approach 2:
The patent performs channel estimation and codebook generation in advance using a reduced RF chain configuration. The precomputed codebook is then used for analog beamforming during actual data transmission, avoiding the need for continuous digital baseband processing and reducing overall power consumption.
2Use of energy by moving object
If the number of RF chains is reduced to one, then power consumption and cost are reduced, but channel element accessibility is limited
Solution Approach 1:
The patent creates a virtual representation of the channel through codebook generation using training points and gradient descent optimization. This codebook copy contains the essential channel characteristics needed for beamforming, allowing the system to access channel information indirectly through the precomputed codebook rather than direct digital measurement of all channel elements.
Solution Approach 2:
The patent changes the representation parameters of channel information from direct complex channel coefficients (requiring multiple RF chains) to phase-shifter codebook entries that can be generated and stored with a single RF chain. This parameter transformation preserves the essential beamforming information while reducing hardware requirements.
3Use of energy by moving object
If analog beamforming is used, then power consumption is reduced, but beamforming gain optimization becomes more difficult
Solution Approach 1:
The patent implements an iterative gradient descent optimization process where the codebook is updated based on feedback from the beamforming gain metric. Training points are assigned to codewords, the codewords are updated via gradient descent, and the process repeats with convergence checking, creating a feedback loop that automatically optimizes the codebook for maximum beamforming gain.
Solution Approach 2:
The patent transforms the static codebook design problem into a dynamic optimization process. The codebook evolves iteratively through gradient descent updates, with training points being reassigned and codewords being refined in successive iterations until convergence is achieved, allowing the system to adaptively find the optimal codebook configuration.
Data Source
AI summary
A method of designing a codebook for analog beamforming. In some embodiments, the method includes: generating a plurality of training points, based on a predefined distribution, each training point being a channel vector; generating, for each of a plurality of codewords, a respective initial value; assigning, in a first assignment operation, each of the training points to a respective desired codeword, the desired codeword maximizing a metric function of a beamforming gain for the training point over the codewords; updating, in a first updating operation, each of the codewords according to the training points assigned to it; and determining whether convergence is achieved; and in response to determining that convergence is achieved, determining a final codebook.