The invention relates to a transmitter device and a receiver device for efficient transmission of information messages. The transmitter device superposes a selected subset of columns of a projection matrix based on an information message so as to obtain a signal for transmission. The signal is transmitted to the receiver device. The receiver device performs iterative successive interference cancellation on a received signal based on a projection matrix so as to obtain a subset of the columns of the projection matrix and therefrom obtains a recovered information message based on the subset of the columns of the projection matrix. Thereby, it is provided a sparse superposition coding scheme with quasi-orthogonal projection matrix achieving good performance in respect of spectral efficiency. Furthermore, the invention also relates to corresponding methods and a computer program.