Implementation and performance of data predistortion with memory in digital microwave radio

An efficient data predistortion technique with memory for compensation of high-power amplifier (HPA) nonlinearities in digital microwave radio systems employing QAM (quadrature amplitude modulation) signal formats is presented. A practical implementation method is described which trades off performance against complexity and makes it possible to implement this kind of predistorter in 256-QAM and higher-level QAM systems. Using the 16-, 64-, and 256-QAM signal constellations, it is shown that the proposed technique achieves a considerably higher performance than conventional memoryless data predistortion. The proposed technique is shown to achieve a gain that is in excess of 2 dB over conventional memoryless data predistortion