Power Amplifier-Aware User Scheduling for Massive MIMO
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Solution Overview
Problem
Massive MIMO networks face challenges in reducing beamformed self-interference due to nonlinear signal distortion, which can have catastrophic consequences in critical applications like M-MTC and URLLC, leading to reduced signal-to-noise ratio (SINR) and potential failures in critical systems.
Innovation Solution
A method is introduced for determining scheduling assignments in a network node with an antenna array to mitigate nonlinear signal distortion by obtaining channel state information, determining precoding vectors, and selecting frequency scheduling assignments that minimize distortion, allowing for the use of low-complexity, high-efficiency hardware and improving spectral efficiency without requiring additional spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If low-complexity radios with limited linearity performance are used in massive MIMO, then device complexity and cost are reduced, but beamformed self-interference increases and SINR deteriorates
Solution Approach 1:
The patent changes the scheduling parameter from traditional metrics to nonlinear distortion metrics. By estimating nonlinear distortion for different scheduling assignments and selecting assignments that minimize distortion, the system enables use of low-linearity amplifiers while maintaining acceptable SINR performance. This parameter change resolves the contradiction by making the system tolerant to hardware nonlinearity through intelligent resource allocation.
2Productivity
If users with similar channels are scheduled to the same frequency resources, then spectral efficiency is maximized, but nonlinear signal distortion increases catastrophically
Solution Approach 1:
The patent applies local quality by making scheduling decisions specific to pairs of users based on their channel similarity and nonlinear distortion characteristics. Rather than a uniform scheduling approach, the system evaluates nonlinear distortion locally for each potential scheduling assignment and selects assignments that minimize distortion while maintaining spectral efficiency. This localized optimization resolves the contradiction by allowing efficient resource usage without catastrophic distortion.
3Device complexity
If traditional scheduling methods are used without distortion compensation, then implementation complexity is low, but beamformed self-interference reduces SINR to unacceptable levels
Solution Approach 1:
The patent applies preliminary action by estimating nonlinear distortion for potential scheduling assignments before making the final scheduling decision. The network node calculates distortion metrics in advance for different frequency scheduling options, then selects the assignment with minimum distortion. This preliminary evaluation enables the system to achieve acceptable SINR with low-complexity hardware while keeping the actual scheduling implementation relatively simple.
Data Source
AI summary
The present disclosure relates to a method (100) for determining scheduling assignments for reducing nonlinear signal distortion, performed in a network node of a wireless communications network. The network node comprises an antenna array arranged to perform beamforming. The method (100) comprises obtaining (S10) channel state information, CSI, relating to respective channels between the network node and at least two wireless devices served by the network node. The method further comprises determining (S20) precoding vectors to the at least two wireless devices based on the obtained CSI. The method also comprises determining (S30) at least two frequency scheduling assignments for each of the at least two wireless devices. The method additionally comprises estimating (S40), for each of the determined at least two frequency scheduling assignments, a respective transmitted nonlinear signal distortion to each of the at least two wireless devices based on the obtained CSI. The method yet further comprises selecting (S50) a frequency scheduling assignment of the determined at least two frequency scheduling assignments based on the estimated transmitted nonlinear signal distortions. The present disclosure also relates to corresponding network nodes and computer programs.