On the capacity and asymptotic performance of MC-CDMA system over Nakagami-m fading channels

The ergodic channel capacity of an MC-CDMA system in the presence of frequency-selective Nakagami-m fading is studied. The channel information is unknown at the transmitter and perfectly known at the receiver. It is seen that a multipath channel may have an advantage or disadvantage for its inherent diversity in the sense of ergodicity, depending on the value of fading parameter, m. Especially, it has no advantage or disadvantage for its inherent diversity in the presence of Rayleigh fading. In the case of a constant multipath intensity profile, when the number of multipaths becomes large, the ergodic capacity approaches the one for the Rayleigh fading channel. In addition to the information theoretic considerations, the asymptotic BER performance for MC-CDMA systems with MMSE reception over Nakagami-m fading channels in terms of the fading parameter, m, the number of multipaths, L, and the average power decay rate, δ, is also studied. The closed-form expression is also obtained for asymptotic signal-to-interference-plus-noise when the frequency domain channel fading parameter takes on integer values.