Nonlinear Distortion Cancellation using Particle Swarm Optimization (PSO) based Predistortion in OFDM systems

A new adaptive digital predistorter based on the use of PSO (particle swarm optimization) algorithm is developed and applied in an orthogonal frequency-division multiplexing (OFDM) transmission scheme, such as a WiMAX system. OFDM transmission is an efficient way to deal with multipath, being its implementation less complex than traditional equalizers, however, it is also very sensitive to nonlinear distortions due to its greatly variable envelope. The performance of this method has been verified by means of simulation and has been compared to the well-known LMS (least mean squares) algorithm. In both cases, a reduction in out-of-band distortion around 20 dB is obtained when the power amplifier works with a 6 dB output backoff (OBO). Both estimation algorithms are presented and discussed.