This paper shows an enhanced training for the EKF-RTRL (Extended Kalman Filter -Real Time Recurrent Learning) single neuron Equalizer using heuristic mechanisms on the training algorithms enabling them to make the training process initial conditions set-up more automatic. The method uses a parameter which evolves accordingly in the training period. The equalizer is used for fast fading selective frequency channels using the WSS_US (Wide Sense Stationary -Uncorrelated Scattering) model. The EKF-RTRL is a symbol by symbol neural equalizer. The performance results here presented depicts several scenarios regarding the channel variation speed. The performance considered in this paper is the symbol error rate (SER).
I. INTRODUCTIONHIS paper presents a single state neuron equalizer for fast fading channels. Traditional equalizers perform well over fixed channels, but show poor results for time varying channels. Indeed, many real life channels, like mobile channels particularly in fast fading scenarios are timevarying. This motivates the use of dynamic neural networks as equalizer structures rather than using conventional static structures. Neural networks are known to produce quite good nonlinear mapping of the inverse response of the channel [1] which is of paramount importance in the equalization problem. Recurrent neural networks are within the class of neural networks the most adequate for handling equalization in presence of time-varying channels [1]. The study of fast convergence and high performance channel impulse response tracking equalizers has been carried out by communication systems researchers, in order to use them in digital communication applications in which the effects of fast and frequency selective fading strongly impacts the system performance [2,3]. Such is the case of TDMA digital mobile communication systems. The present work reports preliminary results involving such issues and aims to initiate such studies by using initial conditions parameter based strategies using neural equalizers trained by extended Kalman filters. One of the pioneers work on recurrent neural networks applied to equalizers was done by Kechriotis et al. [4] proposing a fully Recurrent Neural Network Equalizer typically with a small number of neurons which outperforms the linear transversal equalizer