Alain Glavieux

Near Shannon limit error-correcting coding and decoding: Turbo-codes. 1

A new class of convolutional codes called turbo-codes, whose performances in terms of bit error rate (BER) are close to the Shannon limit, is discussed. The turbo-code encoder is built using a parallel concatenation of two recursive systematic convolutional codes, and the associated decoder, using a feedback decoding rule, is implemented as P pipelined identical elementary decoders.<<ETX>>

Near optimum error correcting coding and decoding: turbo-codes

This paper presents a new family of convolutional codes, nicknamed turbo-codes, built from a particular concatenation of two recursive systematic codes, linked together by nonuniform interleaving. Decoding calls on iterative processing in which each component decoder takes advantage of the work of the other at the previous step, with the aid of the original concept of extrinsic information. For sufficiently large interleaving sizes, the correcting performance of turbo-codes, investigated by simulation, appears to be close to the theoretical limit predicted by Shannon.

Iterative correction of intersymbol interference: Turbo‐equalization

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.

Turbo-detection: a new approach to combat channel frequency selectivity

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.

Error probability of fast frequency hopping spread spectrum with BFSK modulation in selective Rayleigh and selective Rician fading channels

The performance of noncoherent reception in fast frequency hopped spread-spectrum (FFH-SS) communication systems operating through noisy, fading multipath channels is investigated. Systems operating with binary frequency-shift keying (BFSK) modulation and noncoherent demodulation are examined under the assumption of very slow fading. These analyses demonstrate the frequency hopping benefits in selective channels. Expressions are derived for the bit error rate in the context of selective Rayleigh and selective Rician fading channels, as a function of channel and system parameters. >

Orthogonal frequency division multiplexing with BFSK modulation in frequency selective Rayleigh and Rician fading channels

The performance of noncoherent reception with orthogonal frequency division multiplexing (OFDM) and binary frequency-shift-keying (BFSK) modulation over multipath fading channels with noise is investigated. This analysis demonstrates that it is possible to transmit information in selective channels with no symbol interference. Expressions of the bit error probability (BEP) are derived in the context of frequency selective Rayleigh and frequency selective Rician fading channels with and without convolutional coding. >

Equal gain diversity improvement in fast frequency hopping spread spectrum multiple-access (FFH-SSMA) communications over Rayleigh fading channels

The authors present the performance analysis of an FFH-SSMA system with a binary frequency-shift keying modulation scheme and noncoherent demodulation, operating in a combined environment of Rayleigh selective fading, other users interference, and additive white Gaussian noise. Improvement due to the use of equal gain diversity (EGD) is studied in terms of bit-error rate (BER). Expressions of the BER are evaluated when a maximum-likelihood decision criterion is used to show the advantages of the use of frequency hopping selective Rayleigh fading channels. Results show the equivalence between frequency hopping and direct-sequence (DS) modulation in combating multipath fading. The performance, in terms of irreducible error probability, of the system under study and that of the DS-CPSK when using EGD are not significantly different. >

Performance of a slow frequency hopping BFSK system using convolutional coding in underwater acoustic media

The noncoherent reception performance of a slow frequency-hopped binary frequency-shift-keying (SFH-BFSK) modulation scheme in an underwater acoustic channel is investigated. Expressions of the bit error rate (BER) are obtained in the context of Rayleigh selective and Rician selective fading channels as a function of channel and system parameters. Improvements due to the use of error correcting codes (convolutional coding with Viterbi decoding algorithm) are investigated. Because of the difficulty in exact evaluation of the BER, upper bounds are generally used. In this case, the Monte Carlo simulation approach was used to obtain numerical results for high BERs. The Union-Bhattacharyya upper bound is used for low BERs.<<ETX>>

Performances of fast frequency hopping, binary frequency shift keying (FFH-BFSK) spread spectrum multiple access communications over fading channels

A fast-frequency-hopping spread-spectrum multiple-access (FFH-SSMA) system with a binary frequency-shift-keying (BFSK) modulation scheme is studied. Interference from undesired users and multipath are analyzed. Improvement due to the use of equal gain diversity is studied in terms of bit error rate (BER). Expressions for the BER are evaluated when a maximum-likelihood decision criterion is used to show the advantages of frequency hopping in selective fading channels.<<ETX>>