Turbo Codes Application to DS-CDMA Mobile Radio

Atsushi FUJIWARA  Hirohito SUDA  Fumiyuki ADACHI  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E81-A    No.11    pp.2269-2273
Publication Date: 1998/11/25
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Spread Spectrum Techniques and Applications)
turbo codes,  DS-CDMA,  mobile radio,  fading channel,  

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The binary parallel concatenated codes called turbo codes provide relatively large coding gains with reasonable computation complexity. The application of turbo codes to a coherent DS-CDMA mobile radio link with antenna diversity and coherent RAKE combining is considered. A soft-in/soft-out Viterbi decoder that requires less computation complexity is employed instead of maximum a posteriori probability (MAP) decoder. The effect of turbo codes on the achievable bit error rate (BER) performance in frequency selective multipath fading channels is evaluated by computer simulation. It is demonstrated that turbo codes can achieve better BER performance than convolutional codes having the same code rate for the relatively large interleaver size. How the coding gains are impacted by the interleaver size and constraint length of the turbo codes and by the propagation channel condition (power delay profile, the number of resolvable propagation paths, and the maximum Doppler frequency) is discussed.