Iterative Demodulation and Decoding for Parallel Combinatorial SS Systems

Shigenobu SASAKI
Hisakazu KIKUCHI

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E84-A    No.12    pp.2991-2999
Publication Date: 2001/12/01
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Spread Spectrum Techniques and Applications)
spread spectrum,  multi-code CDMA,  iterative decoding,  channel coding,  

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This paper proposes iterative demodulation/decoding for parallel combinatorial spread spectrum (PC/SS) systems. A PC/SS system conveys information data by a combination of pre-assigned orthogonal spreading sequences with polarity. In this paper, convolutional coding with a uniform random interleaver is implemented in channel coding, just like as a serial concatenated coding. A 'soft-in/soft-out' PC/SS demodulator based on a posteriori probability algorithm is proposed to perform the iterative demodulation and decoding. Simulation results demonstrate that the proposed iterative demodulation/decoding scheme bring significant improvement in bit error rate performance. This proposed decoding scheme achieves high-speed transmission by two approaches. One is a puncturing operation, and the other is to increase the number of transmitting sequences. In the latter approach, lower error rate performance is achieved comparing with that the punctured convolutional code is used to increase the information bit rate.