Variable step-size MLMS algorithm for digital predistortion in wideband OFDM systems

This paper addresses the stability issues of the least mean absolute third (LMAT) algorithm using the normalization based on the third order in the estimation error. A novel robust normalized least mean absolute third (RNLMAT) algorithm is therefore proposed to be stable for all statistics of the input, noise, and initial weights. For further improving the filtering performance of RNLMAT in different noises and initial conditions, the variable step-size RNLMAT (VSSRNLMAT) and the switching RNLMAT (SWRNLMAT) algorithms are proposed using the statistics of the estimation error and a switching method, respectively. The filtering performance of RNLMAT is improved by VSSRNLMAT and SWRNLMAT at the expense of affordable computational cost. RNLMAT with less computational complexity than other normalized adaptive filtering algorithms, can provide better filtering accuracy and robustness against impulsive noises. The steady-state performance of RNLMAT and SWRNLMAT in terms of the excess mean-square error is performed for theoretical analysis. Simulations conducted in system identification under different noise environments confirm the theoretical results and the superiorities of the proposed algorithms from the aspects of filtering accuracy and robustness against large outliers.

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“…Generally, the variable step-size (VSS) strategies are applied to improve the convergence rate of adaptive filters [38], [39].…”

Section: B Vssrnlmat Algorithmmentioning

confidence: 99%

Robust Normalized Least Mean Absolute Third Algorithms

2019

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“…DPD is an effective way of improving the linearity performance degraded by DLM. The indirect learning DPD algorithm including memory effect was implemented in this work . The developed digital predistorter is expressed as

z (n) = \sum_{k = 1}^{K} \sum_{q = 0}^{Q} a_{k q} x (n - q) | x (n - q) |^{k - 1},

where x ( n ) and z ( n ) are the input and output samples of the predistorter, respectively.…”

Section: W‐cdma Measurement Of Dlm Pamentioning

confidence: 99%

“…However, the tunable elements at the output of the DLM PA are likely to degrade the linearity performance. Digital predistortion (DPD) techniques are commonly used to restore the linearity performance of the PAs .…”

Section: Introductionmentioning

confidence: 99%

High efficiency radio frequency power amplifier with dynamic load modulation for wireless communications

Kwon

Jeong

2016

Micro & Optical Tech Letters

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In this article, a radio frequency (RF) power amplifier (PA) with high efficiency and high linearity is presented by using dynamic load modulation (DLM) technique. To improve the average efficiency, the load impedance is dynamically modulated according to the input envelop using tunable matching circuit (TMC). The TMC using varactors is located at a low‐impedance region of the output matching network. This reduces the RF voltage swing across the varactors, which minimizes the performance degradation by the varactors. The measurement setup is constructed to generate a control signal for the TMC that is synchronized with an input envelope. For wideband code division multiple access (W‐CDMA) signal with a peak‐to‐average ratio of 7.4 dB and a bandwidth of 3.84 MHz at 1.85 GHz, the fabricated DLM PA shows a power‐added efficiency of 49.7% at an output power of 30.6 dBm with an adjacent channel leakage ratio of <–45 dBc © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2717–2722, 2016

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“…This NLMS process normalises the input signal so that the step size parameter can guarantee the stability of this algorithm. Afterwards, the variable step size based LMS algorithm for system state estimation is proposed in [ 5 , 6 ]. This approach provides an optimum convergence rate but there is a trade-off between rate and performance.…”

Section: Introductionmentioning

confidence: 99%

Least mean square fourth based microgrid state estimation algorithm using the internet of things technology

Rana

2017

PLoS ONE

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This paper proposes an innovative internet of things (IoT) based communication framework for monitoring microgrid under the condition of packet dropouts in measurements. First of all, the microgrid incorporating the renewable distributed energy resources is represented by a state-space model. The IoT embedded wireless sensor network is adopted to sense the system states. Afterwards, the information is transmitted to the energy management system using the communication network. Finally, the least mean square fourth algorithm is explored for estimating the system states. The effectiveness of the developed approach is verified through numerical simulations.

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Variable step-size MLMS algorithm for digital predistortion in wideband OFDM systems

Cited by 13 publications

References 11 publications

Robust Normalized Least Mean Absolute Third Algorithms

Robust Normalized Least Mean Absolute Third Algorithms

High efficiency radio frequency power amplifier with dynamic load modulation for wireless communications

Least mean square fourth based microgrid state estimation algorithm using the internet of things technology

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