We discuss the decoding of error-correcting block codes over complex numbers for the transmission over impulsive noise channels. The encoder multiplies a vector of complex information symbols resulting from a modulation scheme, e.g., quadrature amplitude modulation (QAM), with a unitary generator matrix . Choosing the inverse Fourier transform as , the encoding procedure is similar to orthogonal frequency-division multiplex (OFDM) modulation. The maximum a posteriori (MAP) receiver is analyzed and a suboptimum decoder based on the turbo decoding principle is derived. Simulation results show the excellent performance of the iterative decoder.