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Volterra-Parafac digital predistorter for OFDM Wireless Systems

A novel digital predistorter (DPD) for the linearization of power amplifiers (PAs) is presented. The structure is based on a doubly-symmetric Parafac tensor decomposition of Volterra kernels and takes advantage of a frequency-domain representation, what makes it specially attractive for the transmission of orthogonal frequency division multiplexing (OFDM) signals. The approach has been successfully tested with a GaN PA using LTE signals, showing a reduction of over 17 dB in the adjacent channel power ratio and a better in-band equalization compared with a conventional time-domain DPD. As M-ary quadrature amplitude modulated symbols can be directly pipelined into the OFDM transmission framework, the running complexity of proposed structure offers a saving of about four times the floating point operations (FLOPs) compared to time-domain DPDs, with the added value of using only the channel bandwidth for the predistorted signal generation.