Abstract: A water-filling precoder is proposed for shaping the spectrum of transmitted signals in single-carrier systems over inter-symbol interference (ISI) channels. This precoder can be efficiently implemented in the frequency domain without incurring extra receiver complexity. Furthermore, it does not increase the required length of the cyclic prefix (CP). It is proved in the information theory that with the water-filling precoder, superposition codes can achieve the ISI channel’s capacity with linear-minimum-mean-square-error (LMMSE)-based frequency domain equalization. Simulation results based on single-layer convolutional codes show that a power gain of 1～2dB can be achieved by the water-filling precoder.

Key words: single-carrier communication systems, frequency-domain equalization, inter-symbol interference channels, precoder