This book provides a comprehensive review of precoding techniques for digital communications systems from a signal processing perspective. In the first part of the book the authors provide an overview of the principles of precoding for channels with intersymbol interference (ISI) such as Tomlinson-Harashima precoding and Trellis precoding. There is also a discussion on how the widely used OFDM systems can be treated as a special case of precoding techniques and introduce precoding schemes for OFDM systems. Further, the book provides an overview of various existing precoding techniques that reduce the interference level while keeping the receiver design simple in CDMA systems. There is also a complete chapter on the issue of precoding for multiple input multiple output (MIMO) channels. The second part of the book introduces the state-of-the-art precoding techniques originating from several projects and research activities involving multiuser OFDM transmissions and ultra-wideband (UWB) radio systems.