Digital Self-Interference Cancellation in Hybrid MIMO Transmitters
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Solution Overview
Problem
Modern wireless communication systems, particularly in multi-antenna systems, face challenges with self-interference cancellation, especially in hybrid MIMO systems operating in XDD or FD modes, due to complex nonlinear distortion from power amplifiers and the need for accurate modeling of transmit paths to effectively remove self-interference noise.
Innovation Solution
The implementation of an equalizer-assisted digital self-interference cancelation method that mathematically models each transmit path to determine the output at power amplifiers and passes these signals through a set of equalizers replicating channels between transmit and receive paths, allowing for estimation and subtraction of self-interference signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If digital self-interference cancellation is implemented in hybrid MIMO systems, then signal-to-interference ratio is improved, but device complexity increases due to equalizer array and transmit path modeling requirements
Solution Approach 1:
The patent creates digital copies of the transmit path characteristics through modeling and uses equalizer arrays to replicate the self-interference channel response. By creating a digital model of the transmit path including power amplifier nonlinearities, the system can generate accurate estimates of self-interference signals without requiring additional physical hardware, thus improving SIR while managing complexity through virtual replication rather than physical duplication
Solution Approach 2:
The patent replaces analog self-interference cancellation circuitry with digital signal processing approaches. Instead of using analog filters or hardware-based cancellation mechanisms, the system uses digital equalizer arrays and mathematical modeling to estimate and subtract self-interference signals, transitioning from mechanical/analog systems to digital/algorithmic solutions to manage complexity
2Measurement precision
If equalizer array with predetermined channel model is used, then self-interference estimation accuracy is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent performs preliminary characterization of the transmit path and channel conditions during system setup or calibration phases. By pre-determining the channel model and equalizer coefficients before actual operation, the system establishes accurate reference data that compensates for manufacturing variations in power amplifiers and other components, thereby achieving high estimation accuracy without requiring extremely tight manufacturing tolerances
Solution Approach 2:
The patent uses parameter-based modeling where the equalizer array coefficients and channel model parameters are adjusted based on measured system characteristics. Rather than requiring fixed, precision-manufactured components, the system adapts its digital parameters to match the actual hardware behavior, allowing standard manufacturing precision while achieving high estimation accuracy through parameter optimization
3Reliability
If multiple analog power amplifiers are modeled, then cancelation effectiveness is improved, but loss of time increases due to complex calculations
Solution Approach 1:
The patent divides the self-interference cancellation process into separate stages: transmit path modeling, equalizer array computation, and signal subtraction. By segmenting the calculation into discrete, manageable components that can be processed independently and in parallel, the system reduces overall computation time while maintaining cancelation effectiveness across multiple power amplifiers
Solution Approach 2:
The patent pre-computes the equalizer array coefficients and transmit path models during calibration phases before actual communication operation. By performing the most computationally intensive calculations in advance rather than in real-time during data transmission, the system achieves effective multi-amplifier cancellation without introducing significant delay during time-critical communication operations
Data Source
AI summary
A method includes transmitting, by a transceiver configured to concurrently transmit over multiple transmit paths and receive over multiple receive paths, one or more signals, the transceiver comprising multiple transmit antennas and multiple receive antennas. The method also includes, for at least one of the multiple receive antennas: applying a transmit path model to one or more transmitted signals to generate one or more transmit path estimates, the transmit path model determined based on multiple analog power amplifiers associated with the multiple transmit paths; calculating one or more estimated self-interference (SI) signals based on the one or more transmit path estimates using an equalizer array comprising a predetermined channel model; and subtracting the one or more estimated SI signals from one or more receive signals received at the at least one receive antenna to obtain one or more residual signals.