Abstract-In many communication systems, information carrying symbols are transmitted in blocks with guard intervals between blocks for avoiding inter-block interference. This paper proposes a block transmission system that can be decomposed into a set of parallel subblock transmission systems having additive white Gaussian noise (AWGN) channels with equal noise powers even when the channel additive noise is non-Gaussian. The block transmission system has the advantages that standard signal design, block codes, and symbol detection methods for an AWGN channel are easily incorporated into the block transmission system and that the system is easily implemented by FFT processors.