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The system performance of an M-ary DS-CDMA system is investigated for a coherent reception of uplink signals. In addition, the effect of imperfect power control resulting in a lognormal distribution of signal power on the system performance is also considered. A theoretical expression for the bit error rate (BER) performance of M-ary DS-CDMA systems with imperfect power control is achieved. The results show that the M-ary orthogonal modulation can offer performance improvement in terms of BER and capacity, even under imperfect power control. However, the advantage of M-ary technology is almost lost due to bad power control, even increasing the M value. For a specified performance, the derived results can be used as guides in evaluating the required quality of power control for an M-ary DS-CDMA system. Simulation results verify the theoretical derivations.