The Role of Branch-Correlation for an MC-CDMA System Combining with Coherent Diversity over Frequency Selective Channels

The diversity schemes include EGC (equal gain combining) and MRC (maximal ratio combining) diversity combining with an MC-CDMA (multi-carrier coded-division multiple-access) system operating in the cases of either correlated or uncorrelated frequency selective fading channels are invested in this paper. The sum of Nakagami-m variates (envelope intensity) is applied for deriving the closed-form solution with arbitrarily correlated channels which is for the purpose of avoiding the difficulty of explicitly calculating the pdf (probability density function), for example, looking for the CF (characteristic function), for the SNR (signal-to-noise ratio) at the output of MRC or EGC scheme . Moreover, an alternative method utilized to obtain the jpdf (joint pdf) with arbitrary correlation coefficient in terms of the generalized Laguerre polynomial is adopted for the derivative. The analytical results of the new derived BER (bit error rate) formulas are validated by an example of the intensive Monte Carlo computer work in which consider a dual correlated branch MC-CDMA system with several assumed system parameters. It obviously shows that the well consideration and elimination the impact of correlation between fading channels for MRC or EGC diversity scheme will obtain the better system performance for an MC-CDMA system working in the environment with frequency selective fading. Key-Words: Correlated frequency selective channels; EGC diversity; Nakagami-m fading; MC-CDMA system; MRC diversity