DocumentCode :
2434955
Title :
On the suitability of gray bit mappings to outer channel codes in iteratively decoded BICM
Author :
Samuel, Michael ; Barsoum, Maged ; Fitz, Michael P.
Author_Institution :
Electr. Eng. Dept., Univ. of California, Los Angeles, Los Angeles, CA, USA
fYear :
2009
fDate :
1-4 Nov. 2009
Firstpage :
982
Lastpage :
985
Abstract :
Deliberately designed bits-to-symbols mappings were introduced to provide significant coding gains compared to the simple Gray mapping for iteratively-decoded BICM on both AWGN and fading channels. The performance of these powerful mappings has always been illustrated in conjunction with relatively weak outer channel codes like convolutional codes with up to 16 states. However, when a powerful outer code like a parallel concatenated turbo code is employed, a simple Gray mapping becomes significantly superior in performance. The aim of this letter is to give a simple and straightforward interpretation of this discrepancy in behavior based on the extrinsic information transfer chart of the iterative receivers in both cases. Parts of the presented results are scattered in the literature but this letter presents a unified look on the mapping suitability problem and answers positively the question of: ¿if a turbo code is used as an outer code in a BICM transmission, is Gray-mapping more suitable than other more complex candidates?¿.
Keywords :
AWGN channels; Gray codes; channel coding; concatenated codes; decoding; fading channels; interleaved codes; modulation coding; radio receivers; turbo codes; AWGN channel; BICM transmission; Gray bit mapping; bit-interleaved coded modulation; bits-to-symbols mapping; coding gain; extrinsic information transfer chart; fading channel; iterative receiver; iteratively decoded BICM; outer channel code; parallel concatenated turbo code; Binary phase shift keying; Convolutional codes; Euclidean distance; Iterative decoding; MIMO; Multidimensional systems; Mutual information; Partitioning algorithms; Quadrature phase shift keying; Turbo codes;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Signals, Systems and Computers, 2009 Conference Record of the Forty-Third Asilomar Conference on
Conference_Location :
Pacific Grove, CA
ISSN :
1058-6393
Print_ISBN :
978-1-4244-5825-7
Type :
conf
DOI :
10.1109/ACSSC.2009.5470030
Filename :
5470030
Link To Document :
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