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Summary: Design of Turbo Codes for
Non-Equiprobable Memoryless Sources
Guang-Chong Zhu and Fady Alajaji
Mathematics and Engineering
Department of Mathematics and Statistics
Queen's University, Kingston, Ontario, Canada, K7L 3N6
Tel: (613) 533-2423, Fax: (613) 533-2964
E-mail: fady@shannon.mast.queensu.ca
zhugc@shannon.mast.queensu.ca
Abstract
This work addresses the problem of designing Turbo codes for non-uniform binary
memoryless or independent and identically distributed (i.i.d.) sources over noisy chan-
nels. The extrinsic information in the decoder is modi ed to exploit the source redun-
dancy in the form of non-uniformity; furthermore, the constituent encoder structure is
optimized for the considered non-uniform i.i.d. source to further enhance the system
performance. Some constituent encoders are found to substantially outperform Berrou's
(37; 21) encoder. Indeed, it is shown that the bit error rate (BER) performance of the
newly designed Turbo codes is greatly improved as signi cant coding gains are obtained.
Comparisons to the optimal Shannon limit are also provided.
Keywords: Turbo codes, non-uniform i.i.d. sources, joint source-channel coding, AWGN
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