Performance Comparison of Several Non-Linear Equalizers in the Context of Mobile Telecommunications

Abstract

This paper provides a comparative study of several nonlinear blind equalizers in terms of computational requirements and of the transient performance, which is the main criterion to be considered in the context of time-varying channels. Computational requirements are estimated as the number of real additions and multiplications associated with the training algorithm, whereas the transient performance is evaluated in terms of convergence time. The impact of local minima on the tracking ability is carefully evaluated, in terms of a suitable criterion proposed in the paper. Simulations involve both single-layer (linear and polynomial filters), as well as multilayer structures (radial basis function, recurrent network, multilayer perceptron). These techniques are applied to the blind equalization of mobile terrestrial and satellite channels. Guidelines are established for the choice of a suitable structure as the major trade-off to be achieved in a mobile context is between computational effort and robustness of tracking capability (with respect to local minima effects).