en Research Paper Research Paper The throughput enhancement of Space-Time Spreading (STS)-based Multicarrier Direct Sequence Code Division Multiple Access (MC DS-CDMA) system is investigated in this paper. Variable Spreading Factor (VSF) is utilized to improve the data throughput of the system. In this contribution, an analytical approach is proposed to compute a new expression for the Bit Error Rate (BER) performance of the STS-based MC DS-CDMA system against pre-dispreading Signal-to-Noise Ratio (SNR) for different values of spreading factor (SF). The other contribution of the paper is deriving a new closed form expression for computing the throughput enhancement and the BER performance of the VSF STS-based MC DS-CDMA system over Rayleigh fading channel. It is demonstrated that using VSF method in STS-based MC DS-CDMA system improves the throughput of the system by keeping the BER performance at the target level. Frequency Diversity,MC DS-CDMA,Space-Time Spreading,Spreading Factor,Throughput,Variable, 13 22 http://ijeee.iust.ac.ir/browse.php?a_code=A-10-3-76&slc_lang=en&sid=1 V. Vakil 18003194753284600320 18003194753284600320 Yes H. Aghaeinia 18003194753284600321 18003194753284600321 No