Performance of orthogonal multi-carrier CDMA in a multipath fading channel

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Abstract
A DS-CDMA multi-carrier system is proposed. The transmitted data bits are serial to parallel converted to a number of parallel branches. Each bit on each branch is DS-SS modulated and transmitted with a number of orthogonal and overlapping carriers. Given that sufficient interleaving is provided, this procedure provides many advantages. The system performance is compared to that of the conventional RAKE receiver. It is shown that the multi-carrier system over-performs the RAKE receiver when the system parameters are selected properly. The system utilizes a small number of carriers to solve the intersymbol interference (ISI). The data on each carrier is spread by a lower rate PN code. This reduces the effect of inter-chip interference (ICI). This technique is shown to provide the following advantages: the spread spectrum processing gain is increased, the effect of multipath interference is removed, and frequency/time diversity is achieved.