Problem
Research questions and friction points this paper is trying to address.
Power Amplifier
Power Allocation
Nonlinearity
Distortion Noise
Water-filling
Power Amplifier-aware Power Allocation for Noise-limited and Distortion-limited Regimes
🤖 AI Summary
This work addresses the significant performance degradation of conventional water-filling power allocation in the power amplifier (PA) saturation region, which stems from its neglect of PA nonlinearities. Departing from the common linear assumption, this paper is the first to explicitly model the hard-limiter nonlinearity of PAs within the power allocation framework. Leveraging Bussgang’s theorem for statistical linearization, it characterizes the trade-off between signal gain and distortion-induced noise, and jointly optimizes power allocation with a spatial back-off strategy. By introducing a closed-form threshold on thermal noise variance that distinguishes between noise-limited and distortion-limited regimes, and combining projected gradient descent with channel Frobenius norm analysis, the proposed amplifier-aware method substantially enhances system capacity in the PA saturation region, as confirmed by simulations.
📝 Abstract
The conventional power allocation strategy via water-filling relies on the premise that the power amplifier (PA) operates sufficiently below saturation such that a linear RF chain model holds. This work integrates the PA nonlinearity directly into the power allocation formulation, thereby removing the linearity assumption altogether and enabling operation in regimes where distortion noise is non-negligible. Leveraging the Bussgang theorem, we establish a statistical linearization of the PA's hard-limiting model to characterize the trade-off between signal gain and power-dependent distortion. We propose a projected gradient descent algorithm that optimizes power allocation while identifying an optimal spatial back-off strategy. We also derive a closed-form thermal noise variance threshold that separates the noise-limited and distortion-limited operating regimes as a function of the distortion noise variance and the channel Frobenius norm. Numerical simulations validate that our amplifier-aware strategy provides significant capacity gains in the saturation regime compared to standard water-filling.
Innovation
Methods, ideas, or system contributions that make the work stand out.
power amplifier nonlinearity
Bussgang theorem
distortion-aware power allocation
projected gradient descent
noise-distortion regime threshold
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