This invention provides techniques for a CDMA system having high spectrum efficiency with low transmit power. Each transmitter comprises means of selecting some core-sequences out of multiple sequences to make them convey plural data, means of producing an enveloped selected sequence with such a method as to arrange as guard sequences to a repeated sequence made by repeating each of the selected core-sequences, means of modulating a user specific orthogonal carrier frequency by the enveloped selected sequence to produce a transmit-symbol, and means of transmitting the transmit-symbols. And a receiver comprises means of demodulating a receive-symbol with one of the user specific carrier frequencies to produce a base-band receive-symbol, means of separating respective components corresponding to the sequences selected by the user, by analyzing the base-band receive-symbol with a matrix composed of a channel response vector from the user to the receiver to detect plural data on the components.