Turbo equalization: principles and new results

TLDR

The original turbo equalization system by Douillard et al. (1995) uses a convolutional code and two trellis-based detectors, and iterative equalization and decoding has been shown to greatly improve bit error rate. This paper investigates turbo equalization for coded data over intersymbol interference channels, introduces linear-filtering based equalization methods, and reviews design alternatives for given system parameters. The study analyzes turbo equalization by combining linear-filtering equalizers with decoders and examines design choices for channel response and SNR.

Abstract

We study the turbo equalization approach to coded data transmission over channels with intersymbol interference. In the original system invented by Douillard et al. (1995), the data are protected by a convolutional code and the receiver consists of two trellis-based detectors, one for the channel (the equalizer) and one for the code (the decoder). It has been shown that iterating equalization and decoding tasks can yield tremendous improvements in bit error rate. We introduce new approaches to combining equalization based on linear filtering, with decoding.. Through simulation and analytical results, we show that the performance of the new approaches is similar to the trellis-based receiver, while providing large savings in computational complexity. Moreover, this paper provides an overview of the design alternatives for turbo equalization with given system parameters, such as the channel response or the signal-to-noise ratio.