Digital Precoder for Full-Duplex MU-MIMO Self-Interference
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Solution Overview
Problem
Full-duplex wireless communication systems with many antennas face significant challenges in self-interference cancellation, particularly as the number of antennas increases, leading to complexity in analog cancellation circuitry and reduced spectral efficiency.
Innovation Solution
An all-digital method employing a digital precoder at the transmitter side to minimize self-interference by projecting transmission data onto singular vectors corresponding to the smallest singular values of the self-interference channel, reducing self-interference power at receive antennas and enabling full-duplex operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If analog cancellation is used to reduce self-interference in full-duplex systems, then self-interference is reduced, but device complexity grows in proportion to the number of antennas
Solution Approach 1:
The patent replaces the analog cancellation circuitry (mechanical/electronic system) with a digital precoder that operates in the signal processing domain. Instead of using complex analog circuitry to cancel self-interference, the system applies a digital precoder at the transmitter side that projects transmission data onto singular vectors corresponding to the smallest singular values of the self-interference channel, effectively substituting hardware complexity with computational processing.
Solution Approach 2:
The patent changes the approach from analog domain cancellation to digital domain processing by transforming the self-interference channel into its singular value decomposition form. By changing the parameter space from direct analog signal cancellation to transformed digital signal processing, the system achieves self-interference reduction without proportionally increasing hardware complexity.
2Productivity
If the number of antennas is increased to improve spectral efficiency, then spectral efficiency improves, but self-interference cancellation becomes more difficult
Solution Approach 1:
The patent moves the self-interference cancellation problem from the spatial domain (physical antenna arrangement) to the signal processing domain by applying singular value decomposition. This dimensional transformation allows the system to handle the increased number of antennas by processing the self-interference channel in a transformed coordinate system, where the smallest singular values correspond to directions of minimal self-interference.
Solution Approach 2:
The patent changes the parameter space from physical antenna configurations to the singular value decomposition domain. By transforming the self-interference channel matrix into its singular value decomposition form, the system can identify and exploit the smallest singular values to project transmission data onto directions that minimize self-interference, effectively managing the complexity introduced by increased antenna numbers.
3Productivity
If full-duplex operation is implemented to double spectral efficiency, then spectral efficiency doubles, but self-interference overwhelms the receiver
Solution Approach 1:
The patent applies preliminary anti-action by projecting the transmission data onto singular vectors corresponding to the smallest singular values of the self-interference channel before transmission. This pre-processing step at the transmitter side proactively directs the transmission signal away from the directions that would cause maximum self-interference at the receiver, thereby preventing the self-interference from overwhelming the receiver before it occurs.
Solution Approach 2:
The patent converts the harmful self-interference channel characteristics into a beneficial tool by using the singular value decomposition of the self-interference channel to guide the transmission. Instead of treating self-interference as an unwanted disturbance to be passively cancelled, the system exploits the singular value structure to actively shape the transmission signal, projecting it onto the subspace spanned by the smallest singular values, which turns the self-interference channel information into a guide for interference-free transmission.
Data Source
AI summary
Technique for full-duplex transmission in many-antenna multi-user (MU) multiple-input multiple-output (MIMO) systems is presented in this disclosure. An estimate of a self-interference channel between a plurality of transmit antennas and a plurality of receive antennas is first obtained. A precoder for self-interference reduction is generated based on minimizing a self-interference power related to the self-interference channel that is present at the plurality of receive antennas. Transmission data are modified using the precoder by projecting the transmission data onto a defined number of singular vectors of the self-interference channel that correspond to the defined number of smallest singular values of the self-interference channel. Data are received in full-duplex mode via the plurality of receive antennas simultaneously with transmitting the modified transmission data.