Fractionally-spaced CMA under channel noise

In the noise-free case, fractionally-spaced equalization by constant modulus algorithm (FSE-CMA) was shown to be robust to the channel identifiability condition. The effect of additive channel noise on FSE-CMB steady-state behavior is analyzed in terms of the perturbation of the equalizer convergence settings with respect to the convergence settings of the noise-free case. The loss of performance is characterized by the additional residual mean square error induced by the noise. We show that, in noisy conditions, FSE-CMA exhibits an interesting “smoothing effect” that leads to a trade-off between zero forcing (ZF) equalization and output noise enhancement (NE). We also show that the main loss is due to the NE and not to residual intersymbol interference