Performance of a Flexible Form of MC-CDMA in a Cellular System

In this contribution, we investigate a variant of the traditional MC-CDMA system in the case of downlink communication. In the proposed MC-CDMA system, we can independently select the number of chips per symbol (Nchip), the number of carriers (Ncarr) and the FFT length (NFFT), so the available resources can be used more effectively. The bandwidth of this flexible MC CDMA system is proportional to Nchip, while the spectral density of the power spectrum is inversely proportional to Nchip: the transmitted power is independent of Nchip. Furthermore, the flexible MC-CDMA system spreads the power of a smallband interferer over a large bandwidth, so the immunity of the system to smallband interferers increases for increasing Nchip. In the presence of a dispersive channel and for the number of users equal to Nchip, the powers of the useful component, the interference and noise are independent of the number of chips per symbol, while an optimal guard interval can be found that maximises the performance.

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