Gradient-Adaptive Spline-Interpolated LUT Methods for Low-Complexity Digital Predistortion

In this paper, new digital predistortion (DPD) solutions for power amplifier (PA) linearization are proposed, with particular emphasis on reduced processing complexity in future 5G and beyond wideband radio systems. The first proposed method, referred to as the spline-based Hammerstein (SPH) approach, builds on complex spline-interpolated lookup table (LUT) followed by a linear finite impulse response (FIR) filter. The second proposed method, the spline-based memory polynomial (SMP) approach, contains multiple parallel complex spline-interpolated LUTs together with an input delay line such that more versatile memory modeling can be achieved. For both structures, gradient-based learning algorithms are derived to efficiently estimate the LUT control points and other related DPD parameters. Large set of experimental results are provided, with specific focus on 5G New Radio (NR) systems, showing successful linearization of multiple PA samples as well as a 28 GHz active antenna array, incorporating channel bandwidths up to 200 MHz. Explicit performance-complexity comparisons are also reported between the SPH and SMP DPD systems and the widely-applied ordinary memory-polynomial (MP) DPD solution. The results show that the linearization capabilities of the proposed methods are very close to that of the ordinary MP DPD, particularly with the proposed SMP approach, while having substantially lower processing complexity.

[1]  Danilo Comminiello,et al.  Novel Cascade Spline Architectures for the Identification of Nonlinear Systems , 2015, IEEE Transactions on Circuits and Systems I: Regular Papers.

[2]  Jau-Horng Chen,et al.  A Quadratic-Interpolated LUT-Based Digital Predistortion Technique for Cellular Power Amplifiers , 2014, IEEE Transactions on Circuits and Systems II: Express Briefs.

[3]  F.M. Ghannouchi,et al.  A Compact Envelope-Memory Polynomial for RF Transmitters Modeling With Application to Baseband and RF-Digital Predistortion , 2008, IEEE Microwave and Wireless Components Letters.

[4]  Geneviève Baudoin,et al.  Filter Lookup Table Method for Power Amplifier Linearization , 2007, IEEE Transactions on Vehicular Technology.

[5]  Nima Safari,et al.  Digital Predistortion of Power Amplifiers Based on Spline Approximations of the Amplifier Characteristics , 2007, 2007 IEEE 66th Vehicular Technology Conference.

[6]  Fredrik Tufvesson,et al.  Digital Predistortion for Hybrid MIMO Transmitters , 2018, IEEE Journal of Selected Topics in Signal Processing.

[7]  Huihuang Chen,et al.  A spline-based Hammerstein predistortion for 3G power amplifiers with hard nonlinearities , 2010, 2010 2nd International Conference on Future Computer and Communication.

[8]  J.S. Kenney,et al.  Spline-Based Model for Digital Predistortion of Wide-Band Signals for High Power Amplifier Linearization , 2007, 2007 IEEE/MTT-S International Microwave Symposium.

[9]  Jungsang Kim,et al.  Digital predistortion of wideband signals based on power amplifier model with memory , 2001 .

[10]  R. de Figueiredo.  The Volterra and Wiener theories of nonlinear systems , 1982, Proceedings of the IEEE.

[11]  Stefan Parkvall,et al.  5G New Radio: Unveiling the Essentials of the Next Generation Wireless Access Technology , 2018, IEEE Communications Standards Magazine.

[12]  Pere L. Gilabert,et al.  Partial Least Squares Identification of Multi Look-Up Table Digital Predistorters for Concurrent Dual-Band Envelope Tracking Power Amplifiers , 2018, IEEE Transactions on Microwave Theory and Techniques.

[13]  Christian Fager,et al.  Linearity and Efficiency in 5G Transmitters: New Techniques for Analyzing Efficiency, Linearity, and Linearization in a 5G Active Antenna Transmitter Context , 2019, IEEE Microwave Magazine.

[14]  Pui-In Mak,et al.  A Hardware-Efficient Feedback Polynomial Topology for DPD Linearization of Power Amplifiers: Theory and FPGA Validation , 2018, IEEE Transactions on Circuits and Systems I: Regular Papers.

[15]  Kamran Azadet,et al.  Digital Predistortion Using Lookup Tables With Linear Interpolation and Extrapolation: Direct Least Squares Coefficient Adaptation , 2017, IEEE Transactions on Microwave Theory and Techniques.

[16]  Mikko Valkama,et al.  Nonlinear Digital Cancellation in Full-Duplex Devices Using Spline-Based Hammerstein Model , 2018, 2018 IEEE Globecom Workshops (GC Wkshps).

[17]  Markus Rupp,et al.  On Feedback Sample Selection Methods Allowing Lightweight Digital Predistorter Adaptation , 2020, IEEE Transactions on Circuits and Systems I: Regular Papers.

[18]  Lei Guan,et al.  Band-Limited Volterra Series-Based Digital Predistortion for Wideband RF Power Amplifiers , 2012, IEEE Transactions on Microwave Theory and Techniques.

[19]  Anding Zhu.  Digital Front-End in Wireless Communication and Broadcasting: Digital predistortion and its combination with crest factor reduction , 2011 .

[20]  Danilo Comminiello,et al.  Nonlinear spline adaptive filtering , 2013, Signal Process..

[21]  T.J. Brazil,et al.  An Overview of Volterra Series Based Behavioral Modeling of RF/Microwave Power Amplifiers , 2006, 2006 IEEE Annual Wireless and Microwave Technology Conference.

[22]  B. A. D. H. Brandwood.  A complex gradient operator and its applica-tion in adaptive array theory , 1983 .

[23]  Fredrik Tufvesson,et al.  Digital Predistortion for Multiuser Hybrid MIMO at mmWaves , 2020, IEEE Transactions on Signal Processing.

[24]  Markus Rupp,et al.  Adaptive pre-distortion techniques based on orthogonal polynomials , 2010, 2010 Conference Record of the Forty Fourth Asilomar Conference on Signals, Systems and Computers.

[25]  Danilo Comminiello,et al.  Hammerstein uniform cubic spline adaptive filters: Learning and convergence properties , 2014, Signal Process..

[26]  S. L. Harris,et al.  Fundamentals of Digital Signal Processing Using MATLAB , 2004 .

[27]  Yasushi Yamao,et al.  FPGA Implementation of Adaptive Digital Predistorter With Fast Convergence Rate and Low Complexity for Multi-Channel Transmitters , 2013, IEEE Transactions on Microwave Theory and Techniques.

[28]  Janne Aikio,et al.  Digital predistortion of amplitude varying phased array utilising over-the-air combining , 2017, 2017 IEEE MTT-S International Microwave Symposium (IMS).

[29]  Raviv Raich,et al.  Orthogonal polynomials for power amplifier modeling and predistorter design , 2004, IEEE Transactions on Vehicular Technology.

[30]  Yasir Rahmatallah,et al.  Peak-To-Average Power Ratio Reduction in OFDM Systems: A Survey And Taxonomy , 2013, IEEE Communications Surveys & Tutorials.

[31]  Mikko Valkama,et al.  Piecewise Digital Predistortion for mmWave Active Antenna Arrays: Algorithms and Measurements , 2020, IEEE Transactions on Microwave Theory and Techniques.

[32]  F.M. Ghannouchi,et al.  A Data-Based Nested LUT Model for RF Power Amplifiers Exhibiting Memory Effects , 2007, IEEE Microwave and Wireless Components Letters.

[33]  Gang Wang,et al.  An improved look-up table predistortion technique for HPA with memory effects in OFDM systems , 2006, IEEE Trans. Broadcast..

[34]  Jaehyeong Kim,et al.  A Generalized Memory Polynomial Model for Digital Predistortion of RF Power Amplifiers , 2006, IEEE Transactions on Signal Processing.

[35]  F.M. Ghannouchi,et al.  Behavioral modeling and predistortion , 2009, IEEE Microwave Magazine.

[36]  Christian Fager,et al.  A Comparative Analysis of the Complexity/Accuracy Tradeoff in Power Amplifier Behavioral Models , 2010, IEEE Transactions on Microwave Theory and Techniques.

[37]  Mikko Valkama,et al.  Digital Predistortion in Large-Array Digital Beamforming Transmitters , 2018, 2018 52nd Asilomar Conference on Signals, Systems, and Computers.

[38]  Fadhel M. Ghannouchi,et al.  Low Computational Complexity Digital Predistortion Based on Direct Learning With Covariance Matrix , 2017, IEEE Transactions on Microwave Theory and Techniques.

[39]  Long Chen,et al.  Beam-Oriented Digital Predistortion for 5G Massive MIMO Hybrid Beamforming Transmitters , 2018, IEEE Transactions on Microwave Theory and Techniques.

[40]  C. R. Deboor,et al.  A practical guide to splines , 1978 .

[41]  C. Fager,et al.  Digital Predistortion Using a Vector-Switched Model , 2012, IEEE Transactions on Microwave Theory and Techniques.

[42]  Mikko Valkama,et al.  Decorrelation-Based Concurrent Digital Predistortion With a Single Feedback Path , 2018, IEEE Transactions on Microwave Theory and Techniques.

[43]  T.J. Brazil,et al.  Behavioral modeling of RF power amplifiers based on pruned volterra series , 2004, IEEE Microwave and Wireless Components Letters.

[44]  Jose C. Pedro,et al.  Polynomials and LUTs in PA Behavioral Modeling: A Fair Theoretical Comparison , 2014, IEEE Transactions on Microwave Theory and Techniques.

[45]  Slim Boumaiza,et al.  Multi-Band Complexity-Reduced Generalized-Memory-Polynomial Power-Amplifier Digital Predistortion , 2016, IEEE Transactions on Microwave Theory and Techniques.