A flexible multicarrier CDMA system with time-varying data rates and services

Abstract

We consider an enhanced multicarrier code-division multiple access (CDMA) system that performs the spreading in the time and frequency domains simultaneously, where time-domain spreading codes are used as a main code and frequency-domain spreading codes (FDSCs) are used as a subcode. By allocating the FDSCs to users, rates and services can be dynamically matched to users' needs. The resulting system can support different time-varying source rates and, therefore, enable multimedia applications. In addition, since the proposed scheme uses multiple carriers, it has some advantages such as the mitigated multipath fading, frequency/path diversity and narrowband interference suppression capability, in contrast to a single carrier (SC) system such as the multicode CDMA scheme. Finally, the closed-form expression for probability of bit error is derived for a frequency-selective Rayleigh fading channel. It has been also shown that the proposed system has outperformed the conventional SC RAKE system if the available bandwidth is fixed. Copyright (C) 2008 John Wiley & Sons, Ltd.