Non-constant Modulus Codebook for MIMO Beamforming Gain
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Solution Overview
Problem
Current multiple-input multiple-output (MIMO) transmission systems, particularly in LTE and 5G NR, face limitations due to the use of constant-modulus codebooks, which restrict the realization of full beamforming gains and lead to inefficient power amplification in RF front ends.
Innovation Solution
The implementation of non-constant modulus (NCM) codebooks, which allow dynamic gain control of each antenna element, enabling full beamforming gain by selecting a unit-power beamforming vector and constructing codebooks with quantization tables that optimize power amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If constant-modulus codebooks are used in MIMO transmission, then power amplifier efficiency is improved, but beamforming gain is limited and cannot be fully realized
Solution Approach 1:
The patent changes the modulus parameter of the codebook from constant to non-constant, allowing different amplitude levels across antenna elements. This enables the system to achieve full beamforming gain by optimizing the amplitude distribution while maintaining power amplifier efficiency through coordinated power allocation.
Solution Approach 2:
The patent introduces dynamic gain control for each antenna element through non-constant modulus codebooks. The amplitude of each antenna element can be dynamically adjusted according to channel conditions and power constraints, enabling adaptive optimization of both beamforming gain and power amplifier efficiency.
2Reliability
If non-constant modulus codebooks are used to achieve full beamforming gain, then device complexity increases, but transmission performance improves
Solution Approach 1:
The patent segments the codebook design into structured components including amplitude vectors and phase matrices. This segmentation allows for systematic construction of non-constant modulus codebooks, reducing design complexity while maintaining the ability to achieve full beamforming gain through coordinated amplitude and phase control.
Solution Approach 2:
The patent systematically varies the modulus parameters of codebook entries to create non-constant modulus structures. By controlling the amplitude distribution across antenna elements with defined patterns, the patent reduces design complexity while enabling full beamforming gain realization.
3Reliability
If dynamic gain control is implemented for each antenna element, then power amplifier linearity is improved, but system complexity increases
Solution Approach 1:
The patent implements dynamic gain control through non-constant modulus codebooks, where each antenna element's amplitude can be independently adjusted. This dynamic control improves power amplifier linearity by optimizing the operating point for each element while the structured codebook design keeps the control complexity manageable.
Solution Approach 2:
The patent applies different amplitude characteristics to different antenna elements through the non-constant modulus codebook structure. Each antenna element can have optimized gain characteristics suited to its specific channel conditions and power constraints, improving overall system linearity while maintaining coordinated control.
Data Source
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AI summary
According to certain embodiments, a method for use in a wireless transmitter for simultaneously transmitting a plurality of wireless signals using a plurality of antenna elements comprises selecting a non-constant modulus (NCM) spatial precoder from a NCM codebook comprising a plurality of NCM spatial precoders. The plurality of the NCM spatial precoders are based on a unit-power beamforming vector optimized so that the wireless transmitter transmits up to the full power of each antenna element of the plurality of antenna elements while an overall transmitted power remains constant. The method further comprises applying the selected NCM spatial precoder to a data signal for generating a plurality of coded signals; and transmitting the plurality of coded signals as wireless signals via a power amplifier operating at full power.