Space-time spreading assisted broadband MC DS-CDMA

In this article multicarrier direct-sequence code-division multiple-access (MC DS-CDMA) using space-time spreading (STS) is investigated in the context of broadband communications over frequency-selective Rayleigh fading channels. We consider a range of design issues as well as the achievable bit error rate (BER) performance for the down-link, by assuming synchronous transmission of the user signals. The BER performance of STS assisted broadband MC DS-CDMA using binary phase shift keying (BPSK) modulation is investigated by simulation for a range of parameter values. Our study shows that by appropriately selecting the system parameters, STS assisted broadband MC DS-CDMA is capable of supporting ubiquitous communications in various communication environments including indoor, open rural, suburban and urban areas without BER performance degradation. Furthermore, the STS based transmit diversity schemes can be designed for attaining a certain required diversity gain, while maintaining a near-constant BER in various communication environments, provided that frequency-selective Rayleigh fading channels are encountered.