Suppression of multiuser interference effects in a frequency-selective fading channel is big issue in mobile communication system. In this paper, a parameter of modulations is discussed to develop new modulations which do not yield multiuser interference in CDMA. The modulations are shown to be in a certain class of general orthogonal modulations. The general orthogonal modulations are based on orthogonal vectors, which are obtained by multidimensional rotations and have parameters of rotation planes and rotation angles. We find the parameters of general orthogonal modulations that preserves orthogonality among users in the frequency-selective channel. The derived parameters express the new modulations, whose transfer matrices are expressed by a Kronecker product of two rotation matrices. We obtain the parameters that maximize constellation distance by computer simulations. Numerical results of distance are demonstrated to compare the performance of widely used CDMA and the new modulations proposed in this paper.