In this paper, a receiver is proposed to combat intersymbol interference (ISI) generated over a frequency selective channel. The receiver is based on a symbol detector and a channel decoder separated by a deinterleaver. Through an iterative detecting-decoding process, using turbo-codes principle, the so-called turbo-detector manages to overcome frequency selectivity, especially over a Gaussian channel. Simulation results show the turbo-detector efficiency over both Gaussian and GSM channels

Turbo-detection is an efficient solution to combat Intersymbol Interference generated over a frequency selective channel. Associated with an iterative process, the concatenation of a symbol detector, a deinterleaver, and a channel decoder providing soft outputs leads to performance close to that of a non selective Gaussian channel. When applied to a urban GSM communication, turbo-detection can provide a gain of 4 to 8 dB in signal to noise ratio, compared to the performance of usual GSM receivers, with very few iterations.

This paper presents a receiving scheme intended to combat the detrimental effects of intersymbol interference for digital transmissions protected by convolutional codes. The receiver performs two successive soft-output decisions, achieved by a symbol detector and a channel decoder, through an iterative process. At each iteration, extrinsic information is extracted from the detection and decoding steps and is then used at the next iteration as in turbo-decoding. From the implementation point of view, the receiver can be structured in a modular way and its performance, in bit error rate terms, is directly related to the number of modules used. Simulation results are presented for transmissions on Gauss and Rayleigh channels. The results obtained show that turbo-equalization manages to overcome multipath effects, totally on Gauss channels, and partially but still satisfactorily on Rayleigh channels.