Advancements in communication systems performance have been possible because of digital signal processing applied in all areas of communication systems development and implementation. This volume consists of 20 contributions from researchers and experts. The first group of chapters deals with the audio and video processing for communications applications, including topics ranging from multimedia content delivery over the Internet, through the speech processing and recognition to recognition of non-speech sounds that can be attributed to the surrounding environment. Aspects of Orthogononal Frequency Division Multiplexing (OFDM) technology covered include novel forms of modulation and coding, methods of reducing in-band and out-of-band spurious signal generation, and means of reducing the peak-to-average power ratio of an OFDM waveform. In these contributions, a key objective is to return the inherent implementational simplicity of the OFDM technique while enhancing its performance relative to single carrier systems. Digital signal processing for second and third generation systems is also represented. The topics cover both theoretical issues like spreading sequence design and implementation issues of 3G user equipment modem, and MMSE receivers for CDMA systems. A comparison of complexity of channel estimation, equalization and decoding for GSM receivers is discussed and there are sections on applications of error control coding, information theory, and digital signal processing for communication systems like modulation, software-defined radio, and channel estimation.