EXIT CHART ANALYSIS APPLIED TO ADAPTIVE TURBO EQUALIZATION

In this paper we consider iterative channel estimation, equalization, and decoding, or adaptive Turbo equalization, as a receiver technology for digital communication systems where the channel imposes time-varying intersymbol interference. We show how a semianalytical technique called EXIT charts, originally developed by S. ten Brink for analysis of Turbo codes, can be used to predict the performance of the iterative receiver for such systems. To demonstrate the usefulness of the technique, we use EXIT charts to address interesting questions about adaptive Turbo equalization for time-varying channels: Which pattern of training sequences should be used, what is the performance difference between optimal MAP equalization and suboptimal linear equalization, and between the case of a known channel and the case of an estimated channel, and what can be gained by using a recursive precoder in conjunction with the symbol mapper.

[1]  C. C. Watterson,et al.  Experimental Confirmation of an HF Channel Model , 1970 .

[2]  G. David Forney,et al.  Maximum-likelihood sequence estimation of digital sequences in the presence of intersymbol interference , 1972, IEEE Trans. Inf. Theory.

[3]  John Cocke,et al.  Optimal decoding of linear codes for minimizing symbol error rate (Corresp.) , 1974, IEEE Trans. Inf. Theory.

[4]  Joachim Hagenauer,et al.  A Viterbi algorithm with soft-decision outputs and its applications , 1989, IEEE Global Telecommunications Conference, 1989, and Exhibition. 'Communications Technology for the 1990s and Beyond.

[5]  Alain Glavieux,et al.  Iterative correction of intersymbol interference: Turbo-equalization , 1995, Eur. Trans. Telecommun..

[6]  Alain Glavieux,et al.  Turbo equalization over a frequency selective channel , 1997 .

[7]  Enzo Baccarelli,et al.  Combined channel estimation and data detection using soft statistics for frequency-selective fast-fading digital links , 1998, IEEE Trans. Commun..

[8]  G. Bauch.  A comparison of soft-in/soft-out algorithms for 'turbo-detection' , 1998 .

[9]  Dan Raphaeli.  Linear Equalizers for Turbo Equalization A New Optimization Criterion for Determining the Equalizer Taps , 2000 .

[10]  P. Strauch,et al.  Iterative channel estimation for EGPRS , 2000, Vehicular Technology Conference Fall 2000. IEEE VTS Fall VTC2000. 52nd Vehicular Technology Conference (Cat. No.00CH37152).

[11]  Achilleas Anastasopoulos,et al.  Adaptive soft-input soft-output algorithms for iterative detection with parametric uncertainty , 2000, IEEE Trans. Commun..

[12]  Krishna R. Narayanan.  Effect of precoding on the convergence of turbo equalization for partial response channels , 2001, IEEE J. Sel. Areas Commun..

[13]  Stephan ten Brink,et al.  Convergence behavior of iteratively decoded parallel concatenated codes , 2001, IEEE Trans. Commun..

[14]  Inkyu Lee,et al.  The effect of a precoder on serially concatenated coding systems with an ISI channel , 2001, IEEE Trans. Commun..

[15]  Volker Kühn,et al.  Blind and nonblind turbo estimation for fast fading GSM channels , 2001, IEEE J. Sel. Areas Commun..

[16]  Iain B. Collings,et al.  Joint MAP equalization and channel estimation for frequency-selective and frequency-flat fast-fading channels , 2001, IEEE Trans. Commun..

[17]  Michael Tüchler,et al.  BLOCK SISO LINEAR EQUALIZERS FOR TURBO EQUALIZATION IN SERIAL-TONE , 2001 .

[18]  Michael Tuchler,et al.  EXIT charts of irregular codes , 2002 .

[19]  Michael Tüchler,et al.  Performance of soft iterative channel estimation in turbo equalization , 2002, 2002 IEEE International Conference on Communications. Conference Proceedings. ICC 2002 (Cat. No.02CH37333).

[20]  R. Otnes,et al.  Improved receivers for digital high frequency waveforms using turbo equalization , 2002, MILCOM 2002. Proceedings.

[21]  Michael Tüchler,et al.  Low-complexity turbo equalization for time-varying channels , 2002, Vehicular Technology Conference. IEEE 55th Vehicular Technology Conference. VTC Spring 2002 (Cat. No.02CH37367).

[22]  Maryline Hélard,et al.  Optimization of the equalization and the interleaving in turbo-equalization for a frequency-selective fading channel , 2002, 2002 IEEE International Conference on Communications. Conference Proceedings. ICC 2002 (Cat. No.02CH37333).

[23]  Stephan ten Brink,et al.  Extrinsic information transfer functions: A model and two properties , 2002 .

[24]  Andrew C. Singer,et al.  Turbo equalization: principles and new results , 2002, IEEE Trans. Commun..

[25]  Andrew C. Singer,et al.  Turbo equalization with an unknown channel , 2002, 2002 IEEE International Conference on Acoustics, Speech, and Signal Processing.

[26]  Andrew C. Singer,et al.  Minimum mean squared error equalization using a priori information , 2002, IEEE Trans. Signal Process..

[27]  Michael Tüchler,et al.  Design of Serially Concatenated Systems Depending on the Block Length , 2004, IEEE Trans. Commun..