Asymmetrical Beamforming Power Equalization via Row Normalization
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Solution Overview
Problem
In asymmetric wireless networks with more transmit antennae than receive antennae, existing beamforming methods result in unequal transmit power across antennae, which is undesirable due to peak-power limitations in RF chains, especially in OFDM systems.
Innovation Solution
The implementation of techniques such as brute force normalization, quantization to ±1 ± j values, optimization based on outage probability, hybrid optimization, and optimization across the frequency domain to ensure equal transmit power across all antennae, using singular value decomposition and channel information at the transmitter or receiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If beamforming uses the subset of eigenvectors corresponding to the largest singular values in asymmetric systems (N_T > N_R), then beamforming performance is improved, but transmit power becomes unequal across antennae
Solution Approach 1:
The patent modifies the beamforming matrix by applying normalization to each row such that the sum of squared magnitudes equals a constant value. This parameter transformation changes the power distribution across transmit antennae from unequal to equal, while preserving the directional beamforming properties. The normalization factor is calculated based on the singular values and row norms, ensuring that each transmit antenna operates at the same power level.
2Power
If RF chains transmit unequal power to achieve optimal beamforming, then beamforming gain is maximized, but peak-power limitations in RF amplifiers are violated
Solution Approach 1:
The patent applies row normalization to the beamforming matrix where each row is scaled such that the squared Euclidean norm equals a constant power level P. This ensures that each RF chain operates within its peak-power limitations while maintaining the overall beamforming gain. The normalization process redistributes the power evenly across all transmit antennae, preventing any single RF amplifier from exceeding its maximum power capacity.
3Ease of operation
If brute force normalization is applied to equalize transmit power, then power equality is achieved, but computational complexity increases
Solution Approach 1:
The patent computes the normalization factor for each row of the beamforming matrix by calculating the squared Euclidean norm of that row, then dividing by the square root of the desired power level. This closed-form mathematical transformation efficiently equalizes the transmit power without requiring iterative optimization or complex computations. The method leverages the existing SVD decomposition results and applies a simple scaling operation to achieve power equality.
4Device complexity
If quantization to ±1 ± j values is used to reduce feedback overhead, then feedback complexity is reduced, but beamforming precision decreases
Solution Approach 1:
The patent quantizes the beamforming matrix entries to four possible values: ±1 ± j. This quantization reduces the feedback overhead significantly, as only 2 bits per element are needed instead of representing full complex numbers. The quantized values are sufficient to maintain the directional properties of the beamforming vectors while dramatically reducing the amount of feedback information that must be transmitted from the receiver to the transmitter.
Data Source
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AI summary
The present invention provides a plurality of embodiments for beamforming in an asymmetrical system wireless communication system (400) of N