Quantum MIMO Precoding for Low-PAPR OFDM Under EVM Constraints
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Solution Overview
Problem
MIMO systems face challenges in managing high peak-to-average power ratio (PAPR) that lead to in-band and out-of-band distortion, affecting system performance and failing to meet stringent EVM requirements, particularly in modern wireless communication systems.
Innovation Solution
A quantum precoder is configured to optimize PAPR by embedding a Quadratic Unconstrained Binary Optimization (QUBO) problem on a quantum computing device, using quantum annealing to determine an optimal precoding vector that minimizes PAPR while adhering to EVM constraints, eliminating the need for iterative FFT/IFFT operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If OFDM waveform is used for transmission, then data throughput is improved, but peak-to-average power ratio increases causing distortion
Solution Approach 1:
The patent applies parameter changes by transforming the precoding vector optimization problem into a QUBO formulation that changes the mathematical representation from continuous complex values to discrete binary variables. This parameter transformation enables the use of quantum annealing to find optimal precoding vectors that minimize PAPR while maintaining the throughput benefits of OFDM transmission.
2Power
If High-Power Amplifiers operate at high power levels, then transmission power is improved, but in-band and out-of-band distortion increases
Solution Approach 1:
The patent applies preliminary action by optimizing the precoding vector before signal transmission to pre-reduce peak power occurrences. The quantum annealing process determines optimal precoding weights in advance, shaping the transmitted signal to have lower PAPR characteristics, which allows HPAs to operate more efficiently in their linear region and reduces both in-band and out-of-band distortion.
3Object-generated harmful factors
If iterative FFT/IFFT operations are performed to optimize PAPR, then PAPR reduction is achieved, but computational latency increases
Solution Approach 1:
The patent applies mechanics substitution by replacing the classical iterative FFT/IFFT-based PAPR optimization methods with a quantum annealing approach. The quantum system directly computes the optimal precoding vector through quantum tunneling and thermal annealing processes, eliminating the need for repeated FFT/IFFT iterations and significantly reducing computational latency while achieving effective PAPR reduction.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a latency-efficient method to optimize PAPR, meeting EVM constraints and improving system performance by reducing distortion, thus enhancing communication efficiency.
Implementation Method 1
Particular embodiments use classical computing approaches to obtain an appropriate QUBO that is embedded on the quantum precoder via quantum annealing.
Data Source
AI summary
A Multiple-Input Multiple Output (MIMO) device (200) determines a minimum output vector produced by a quadratic unconstrained minimization function. The quadratic unconstrained minimization function comprises a peak power factor, an average power factor, an Error Vector Magnitude (EVM) constraint factor for meeting an EVM constraint, and a plurality of penalty coefficients that penalizes outcomes that violate the EVM constraint. The MIMO device (200) minimizes the peak power factor and maximizes the average power factor. The minimizing and maximizing are each performed within the EVM constraint. The MIMO device (200) derives a Quantum Unconstrained Binary Optimization (QUBO) from the minimum output vector. The MIMO device (200) then configures the quantum precoder (210) to generate a configuration of qubits that are representative of a precoding vector that meets the EVM constraint and minimizes Peak to Average Power Ratio (PAPR) of a transmission from the MIMO device (200). The configuring comprises embedding the QUBO on the quantum precoder (210).