Performance of the MC-DS-CDMA Systems with PCE and Variable Spreading Factors

Abstract

Multicarrier direct-sequence code-division multiple access (MC-DS-CDMA) becomes an attractive technique for the future fourth-generation (4G) wireless systems. It can flexibly adapt transmission rates by changing both time and frequency spreading factors and possesses many physical-layer advantages in dispersive fading channels. Power control errors (PCE) degrade the performance of the MC-DS-CDMA system. In this paper, we evaluate the impact of different detectors in receiver and the effect of various time and frequency spreading factors and the effect of PCE on the single rate and multirate MC-DS-CDMA system in a Rayleigh Fading Channel with perfect channel estimation. By simulation, we obtain some important insights into the performance of the MC-DS-CDMA system. These insights are according to the following subjects. First off all MRC detection method compared with MMSE and EGC methods results in higher performance in a high capacity system. Afterward we conclude that Increasing frequency-or time domain spreading gain can improve the performance of the MCDS- CDMA system, but the system becomes more sensitive to power control errors and SNR variations. More PCE can exacerbate the performance of the MC-DS-CDMA system. Performance variation in term of BER becomes more sensitive in larger frequency-domain diversity and time- domain spreading gain.