Performance Analysis of Coded-Sequence Self-Encoded Spread Spectrum over Rayleigh Fading Channel

Poomathi DURAISAMY  Lim NGUYEN  

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E96-A   No.1   pp.255-263
Publication Date: 2013/01/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E96.A.255
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Wideband Systems)
Category: 
Keyword: 
spread spectrum,  self-encoded,  iterative detection,  coded-sequence self-encoded spread spectrum,  

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Summary: 
Self-encoded spread spectrum (SESS) derives its spreading codes from the random information source rather than using traditional pseudo-random codes. It has been shown that the memory in SESS modulated signals not only can deliver a 3 dB gain in additive white Gaussian noise (AWGN) channels, but also can be exploited to achieve time diversity and robust bit-error rate (BER) performance in fading channels. In this paper, we propose an extension to SESS, namely coded-sequence self-encoded spread spectrum (CS-SESS), and show that it can further improve the BER performance. We describe the CS-SESS scheme and present the theoretical analysis and simulation results for AWGN and fading channels. Iterative detector is developed to exploit the inherent temporal diversity of CS-SESS modulation. The simulation results show that it can achieve the expected 4.7 dB gain with a complexity that increases linearly with the spreading sequence length under AWGN. In Rayleigh fading channel, it can effectively mitigate the fading effects by exploiting the overall diversity gain. Chip interleaving is shown to yield a performance improvement of around 4.7 dB when compared to an chip interleaved direct sequence spread spectrum (DSSS) system.