A new spreading scheme for convolutionally coded CDMA communicationin a Rayleigh-fading channel |
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Authors: | Young Jo Bang Sang Wu Kim |
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Affiliation: | Dept. of Electr. Eng., Korea Adv. Inst. of Sci. & Technol., Taejon; |
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Abstract: | There has been increased interest in the use of direct-sequence code-division multiple-access (DS/CDMA) for wireless communication systems. We find that the asymptotic bit-error probability (BEP), Pb, of a convolutionally coded code-division multiple-access (CDMA) system in a frequency-selective Rayleigh-fading channel depends on the length of the shortest error event path and the product of symbol distances along that path. Based on this observation, we propose a new spreading scheme that maximizes the length of the shortest error event path. It is shown that the proposed scheme yields an improvement of 1.0-1.3 dB at Pb=10-5 over the conventional convolutionally coded CDMA system, and even a higher improvement can be achieved as the required BEP is decreased |
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