Predistortion of Radio Over Fiber Links: Algorithms, Implementation, and Measurements

• Published in: IEEE transactions on circuits and systems. I, Regular papers Regular papers, 2012-03, Vol.59 (3), p.664-672
• Main Authors: Hekkala, Atso, Hiivala, M., Lasanen, M., Perttu, J., Vieira, L. C., Gomes, N. J., Nkansah, A.
• Format: Article
• Language: English
• Subjects: Adaptive compensation; Algorithms; Antennas; Construction; Distortion; Fibers; field programmable gate array (FPGA); Field programmable gate arrays; least mean square (LMS); Least squares approximation; Links; Modulation; Nonlinear distortion; Nonlinearity; OFDM; Predistortion; Radio; radio over fiber; recursive least squares (RLS); Signal processing algorithms
• ISSN: 1549-8328; 1558-0806
• DOI: 10.1109/TCSI.2011.2167267

Distributed antenna systems (DASs) have been proposed for use in high-data-rate wireless communications. Connecting the central unit to remote antenna units, radio over fiber (RoF) links become essential parts of the DAS. One of the major problems in the RoF links is the nonlinear distortion experienced in its optoelectronic devices. This paper considers the adaptive compensation of the nonlinear RoF link. In particular, we present an extension to the conventional least-mean-square algorithm for memory-polynomial-based predistortion. In addition, we study different combinations of the algorithms for the predistortion. Moreover, we implement the adaptive predistorter in hardware, build a real RoF link, and verify the performance by measurements. The results demonstrate that distortion of the RoF link can be considerably diminished with a low complexity design.