ETRI Journal

Electronics and Telecommunications Research Institute (한국전자통신연구원)
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Performance of a Modified Multicarrier Direct Sequence CDMA System

  • Published : 1997.04.30
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Abstract

In this paper, we present an improved multicarrier direct sequence (DS) code division multiple access (CDMA) scheme by modifying the system originally proposed by Kondo and Milstein [13]. In this modified system, different spreading sequences multiplied by a data sequence modulate different carriers. This is to prevent the multiple access capability from reducing when the fading characteristics of different carrier frequencies are highly correlated. We have derived a formula which determines the mean values of the relative received signal strength in a single carrier DS CDMA rake system and in a multicarrier DS-CDMA system. We present results on the comparison of the bit error rate (BER) performance of the two systems including the effect of correlation between fading characteristics of different frequencies under various multipath fading conditions. The results indicate that with 50 users the modified multicarrier DS CDMA system can achieve an uncoded irreducible BER of $1.7{\times}10^{-3}$ with an average received signal-to-noise ratio per bit of 10dB, which is better that $3.0{\times}10^{-3}$ achieved by the single carrier DS CDMA rake system, and also show that if multicarrier CDMA system is used with respect to single carrier CDMA system, the SNR gain is up to 4.5 dB for the uncode BER of $10^{-3}$ being achieved.

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References

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