Performance of adaptive data predistortion applied to 22N-QAM radio systems

The performance of adaptive data predistortion for combatting high-power amplifier (HPA) nonlinearities is investigated for 2^2N -QAM (quadrature amplitude modulation) techniques in a digital radio context. The transmission filtering is assumed to be performed before the nonlinear amplification. Using the service channel facilities, the updating process does not require doubling the demodulation operation. Results expressed in terms of flat-fade margin gain show that a 2- to 3-dB improvement can be obtained with algorithms of reasonable complexity. Experimental results for a 16-QAM 140 Mb/s setup confirm the validity and the potential interest of the technique