Non-linear Precoding via Vector Perturbation for Massive MIMO
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Solution Overview
Problem
Current baseband non-linear precoding techniques for massive MIMO systems face scalability issues, leading to high computational complexity and suboptimal performance, especially with a large number of transmit antennas, as existing methods like maximum-likelihood search and tree/trellis searching schemes are impractical due to exponential complexity growth.
Innovation Solution
A signal precoder that performs non-linear precoding by determining optimized signal perturbations using a balancer and selector, which scale signal components based on channel properties, reducing complexity by selecting a subset of singular values from the channel matrix through singular value decomposition, and applying these perturbations to minimize energy transmission, thereby achieving near-optimum detection performance with linear computational scalability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If maximum-likelihood search is used to solve non-linear MIMO precoding, then detection performance is improved, but computational complexity increases exponentially
Solution Approach 1:
The patent extracts and optimizes only the most significant singular values from the channel matrix, rather than processing all singular values. This selective extraction reduces the dimensionality of the search space from exponential to polynomial complexity while maintaining near-optimal detection performance.
Solution Approach 2:
The patent transforms the original non-linear precoding problem into a simplified form by changing parameters: selecting a subset of singular values, applying linear precoding first, and then adding a perturbation vector. This parameter transformation converts the intractable exponential complexity into manageable polynomial complexity.
2Device complexity
If tree search or trellis search is used to reduce ML complexity, then computational complexity is reduced, but scalability remains insufficient
Solution Approach 1:
The patent segments the precoding process into two independent stages: linear precoding and perturbation addition. This segmentation allows each stage to be optimized separately, with linear precoding handling the bulk of signal processing and perturbation handling only the residual optimization, enabling better scalability.
Solution Approach 2:
Instead of performing complete non-linear optimization, the patent applies partial action by adding a perturbation vector to the linearly precoded signal. This partial non-linear adjustment achieves most of the performance benefit without the full computational burden, improving scalability.
3Adaptability or versatility
If linear precoding is used for large MIMO systems, then scalability is improved, but performance degrades significantly
Solution Approach 1:
The patent merges linear precoding and non-linear perturbation techniques into a hybrid approach. The linear precoder provides scalability and basic performance, while the added perturbation vector recovers most of the performance loss, achieving both scalability and near-optimal performance.
Solution Approach 2:
The perturbation vector acts as an intermediary that bridges the gap between linear and non-linear precoding. It is added to the linearly precoded signal to correct residual interference and improve performance without requiring a complete non-linear solution.
Data Source
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AI summary
A signal precoder is provided for use with a signal transmitter comprising a plurality of antennas for transmitting a plurality of signal components to a receiver over a communications channel in which one or more properties of the communications channel are described by a plurality of values which scale t he components of the signal in a plurality of dimensions during transmission, in which the precoder is arranged to perform non-linear precoding on a source signal prior to signal transmission, the precoder comprising a balancer for determining a plurality of optimised amounts of signal perturbation required to be applied to one or more source signal components to minimise the energy of the signal transmission, when respectively scaled by each of the values describing one or more properties of the communications channel, and a selector for selecting which of the optimised amounts of signal perturbations results in signal transmission having the least energy when scaled by the values describing the one or more properties of the communications channel, wherein the precoder is arranged to perform non-linear precoding on the source signal by applying the selected optimised signal perturbation to the source signal and to output the precoded signal. The embodiments of the present invention offer near-optimum detection performances and linear computational scalability simultaneously. The present invention also provides a signal transmitter, a communications system and a signal receiving method.