Nonlinear Modified Concurrent Equalizer

Abstract

Wireless and optical communication systems not infrequently are disrupted by intersymbol interference (ISI). Wireless communications are degraded by multipath propagation in the wireless channel, while optical communications are degraded due to chromatic and polarization mode dispersion. For both cases, equalization techniques are applied to circumvent the problem. In this context, this paper proposes a novel concurrent blind equalizer, based on the nonlinear modified constant modulus algorithm (NMCMA) and on the soft direct decision (SDD) algorithm. The proposed nonlinear modified concurrent equalizer (NMCE) combines the NMCMA sharp decision regions with the SDD fast convergence, resulting in improved performance. The NMCE is compared with the NMCMA and with the constant modulus algorithm CMA-SDD equalizers under static and dynamic multipath scenarios. Results show that the proposed solution presents fast convergence, lower steady-state mean squared error (MSE), and reduced symbol error rate (SER) when compared with the NMCMA and the CMA-SDD equalizers, even in dynamic propagation scenarios.