Wireless Receiver Decorrelator Using Binary Index Transform
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Solution Overview
Problem
Existing decorrelation methods in wireless communications face challenges in achieving coding gains due to signal errors and complexity in computing covariance matrices, especially when using unitary transformations like DFT and FFT, which result in limited decorrelation gains and increased complexity.
Innovation Solution
The use of a binary index transform (BiT) for signal processing, which involves simple binary signal pairing and does not require DFT or FFT, to achieve decorrelation gains through N-branch systems, enhancing diversity and reducing complexity by synthesizing virtual antennas and computing principal components of signals between real antennas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DFT or FFT techniques are used for blind decorrelation, then the decorrelation process can be implemented, but signal errors are reduced only limitedly and the complexity remains high
Solution Approach 1:
The patent replaces complex, computationally intensive DFT/FFT algorithms with a simpler binary index transform (BiT) that uses basic arithmetic operations. This 'cheap' alternative achieves decorrelation with significantly reduced computational complexity while maintaining acceptable performance, effectively discarding the need for complex transforms.
Solution Approach 2:
The invention changes the fundamental parameter of the transform approach from unitary transforms (DFT/FFT) to a binary index-based transform. This parameter change allows the system to achieve decorrelation through simple sign changes and additions rather than complex exponential operations, reducing computational burden.
2Reliability
If covariance matrix computation is performed for decorrelation, then accurate decorrelation can be achieved, but the complexity and computational burden increase significantly
Solution Approach 1:
The patent extracts only the essential decorrelation function from the full covariance matrix computation process. Instead of computing the complete covariance matrix and its eigenvectors, the BiT extracts and applies only the necessary transformation components, achieving decorrelation without the full computational overhead.
Solution Approach 2:
The invention replaces the expensive covariance matrix computation with a cheap binary index transform that uses simple sign changes and additions. This disposable, low-complexity approach achieves sufficient decorrelation for wireless communications without requiring precise mathematical optimization.
3Reliability
If N-branch systems with virtual antennas are used, then diversity is enhanced and coding gains are achieved, but the receiver complexity increases
Solution Approach 1:
The patent creates virtual antenna signals by copying and transforming the received signals from N antennas through the binary index transform. These virtual signals are synthesized computationally rather than requiring physical additional antennas, achieving diversity gain through signal processing copies rather than hardware multiplication.
Solution Approach 2:
The binary index transform serves multiple functions simultaneously: it performs decorrelation, generates virtual antenna signals for diversity, and enables simple combining operations. This universal transform handles multiple tasks that would otherwise require separate processing stages, reducing overall receiver complexity.
Data Source
AI summary
This invention relates to decorrelation of signals in order to improve coding gains of wireless communications. To this end a branch signal processor includes a summer to determine a sum of a first branch signal and a second branch signal to produce a sum signal. A conjugate swapper to determine a conjugate swap of the first branch signal and a conjugate swap of the second branch signal to produce two swapped signals, wherein the conjugate swapper takes an imaginary part of the first branch signal to become a real part and a real part of the first branch signal to become an imaginary part of a new complex signal which new complex signal becomes a first swapped signal, and wherein the conjugate swapper takes an imaginary part of the second branch signal to become a real part and a real part of the second branch signal to become an imaginary part of a second complex signal which second complex signal becomes a second swapped signal. A differencer determines a difference of the first swapped branch signal and the second swapped branch signal to produce a difference signal and a diversity combiner configured to combine the sum signal, the first branch signal, the second branch signal and the difference signal.