226 pp. 226-237 Joint channel estimation and data demodulation algorithms for fast time varying band-limited frequency selective Rayleigh fading channels : a comparison study Jean-Pierre CANCES* Vahid MEGHDADI* Abstract In this paper, a comparison study is proposed bet- ween two recent algorithms which both perform joint channel and data estimation. The first one is the well known l~Se : per survivor processing algorithm and the second is called adaptive bloc sequence estimation (BSE). Compared to the existing literature, we add, for our com- parison study, the case of trellis coded transmissions combined with interleaving and deinterleaving tech- niques which are now currently employed for digital communications. Key words : Mobile radiocomunication, Radio channel, Time variable channel, Limited band channel, Selective fading, Rayleigh fading, Statistical estimation, Parameter estimation, Signal estimation, Maximum likelihood, Treillis coding, Quadrature modulation, Inter- leaving. Contents I. Introduction II. The channel model III. Receivers based on per-survivor processing IV. Block sequence estimation technique for non-coded data sequences V. Coded PSK sequences together with interleaving and deinterleaving VI. Simulation VII. Conclusion References (17 ref ) I. INTRODUCTION ESTIMATION CONJOINTE DES PARAMETRES DU CANAL DE PROPAGATION ET DES DONNI~ES I~MISES SUR DES CANAUX RADIOMOBILES, Sl~LECTIFS EN FREQUENCES ET A VARIATIONS RAPIDES Rdsum6 Une comparaison des performances de deux mdthodes rdcentes d' estimation de la rdponse impulsion- nelle d'un canal de communication non stationnaire et de ddcodage des s~quences numdriques transmises est proposYe. Deux m~thodes sont principalement dtudi~es : la technique du traitement par survivant (PsP) et la tech- nique d'estimation adaptative des donn~es par blocs (BSE) dans le contexte de transmissions numdriques cod~es (MeT : modulations coddes en treillis) utilisant les techniques d' entrelacement et de d(sentrelacement. Mots cl~s : Radiocommunication service mobile, Canal radio61ec- trique, Canal variant dans temps, Canal bande limit6e, l~vanouissement s61ectif, Evanouissement Rayleigh, Estimation statistique, Estimation param6tre, Estimation signal, Maximum vraisemblance, Codage treillis, Modulation quadrature, Entrelacement. Usually the problem of digital communication sys- tems sending messages through band-limited channels which introduce inter-symbol interference (IsI) is addressed by means of linear and decision feedback equalizers. In mobile systems [sI may also be introdu- ced by multi-path propagation when the maximum anti- cipated time spread (TM) of the channel impulse response (fro) extends over several symbol periods (Ts). Moreover, the mobile motion creates Doppler fre- quency spread in the received signal spectrum. All of these impairments considerably limit the performances of the transmission system and degrade the bit error rate (BER) [1,2]. The major drawback of the adaptive equalizers arises when the mobile radio channel exhibit time varying deep spectra nulls in their frequency response. This can be rapidly explained by the fact that they try to estimate the inverse channel response at a given time : consequently, when the channel frequency response has deep nulls in its band the inverse channel must have poles at the corresponding frequencies. This may result in excessive noise amplification in the channel fre- quency band [2]. *Groupe d'Etude des Syst6mes de T6Mcommunications, Ecole Nationale Sup6rieure d'Ing6nieurs de Limoges, Parc d'Ester Technopole, F-87068 Limoges cedex, France ANN. TI~Lt~COMMUN., 55, n~5-6, 2000 1/12