Performance study of RAM-based decision feedback equalizers with application to nonlinear satellite channels

The performance of nonlinear decision feedback equalizer implementations based on the use a random access memory (RAM) look-up table are considered. RAM look-up tables admit the modeling, without approximation, of the nonlinear intersymbol interference of nonlinear channels with finite memory. Three equalizers are considered; the RAM-DFE; RAM-canceler; and recently developed pre-cursor enhanced RAM-DFE canceler (PERC). In contrast to the classical "feedforward" Volterra equalizers, these equalizers have the advantage that the nonlinear processing element is out of the path of the noise, thus avoiding noise amplification. Results are presented for 16-QAM which compare and demonstrate the effectiveness of these equalizers, particularly the PERC, on the nonlinear satellite channel.