Each group of Group-Orthogonal MC-CDMA systems functions as an independent MC-CDMA system.Choosing the number of users reasonably make the use of Maximum Likelihood Multi-User Detection(ML-MUD) within each group computationally feasible.In this paper, the uplink performance of GO-MC-CDMA system using Maximum Likelihood(ML) detection is investigated,when considering the presence of Carrier-Frequency Offset(CFO).The effect of different modulation and number of users on BER is compared.Numerical simulation results show that the GO-MC-CDMA sy...