A postdistortion receiver for mobile communications

The paper presents a postdistortion receiver, for possible future mobile communication systems, which can potentially increase both the spectral efficiency and the transmitter´s power efficiency (especially important for portable units). Postdistortion is a technique, implemented at the base-station receiver, to compensate for AM-AM and AM-PM nonlinearities of a mobile transmitter´s amplifier which, if uncompensated, would cause adjacent channel interference. A unique adaptation method is demonstrated to compensate for slow variations in the power amplifier´s characteristics without an interruption for a training period. Various aspects of system performances, including SNR and convergence speed, have been simulated. The system performance in fading channel conditions is also considered. The simulation and measured results show that the postdistortion technique can improve the out-of-band emission by up to 20 dB; the corresponding increase in mobile transmitter power efficiency is approximately a factor of 10. The spectral efficiency is approximately increased by 20% with the postdistortion implementation