Digital watermarking is a key ingredient to copyright protection. It provides a solution to illegal copying of digital material and has many other useful applications such as broadcast monitoring and the recording of electronic transactions. Now, for the first time, there is a book that focuses exclusively on this exciting technology. Digital Watermarking covers the crucial research findings in the field: it explains the principles underlying digital watermarking technologies, describes the requirements that have given rise to them, and discusses the diverse ends to which these technologies are being applied. As a result, additional groundwork is laid for future developments in this field, helping the reader understand and anticipate new approaches and applications.

Digital Watermarking

Digital processing of speech signals

Conventional radio-frequency (RF) power amplifiers operating with wideband signals, such as wideband code-division multiple access (WCDMA) in the Universal Mobile Telecommunications System (UMTS) must be backed off considerably from their peak power level in order to control out-of-band spurious emissions, also known as "spectral regrowth." Adapting these amplifiers to wideband operation therefore entails larger size and higher cost than would otherwise be required for the same power output. An alternative solution, which is gaining widespread popularity, is to employ digital baseband predistortion ahead of the amplifier to compensate for the nonlinearity effects, hence allowing it to run closer to its maximum output power while maintaining low spectral regrowth. Recent improvements to the technique have included memory effects in the predistortion model, which are essential as the bandwidth increases. In this paper, we relate the general Volterra representation to the classical Wiener, Hammerstein, Wiener-Hammerstein, and parallel Wiener structures, and go on to describe some state-of-the-art predistortion models based on memory polynomials. We then propose a new generalized memory polynomial that achieves the best performance to date, as demonstrated herein with experimental results obtained from a testbed using an actual 30-W, 2-GHz power amplifier

A Generalized Memory Polynomial Model for Digital Predistortion of RF Power Amplifiers

The ability to recognize affective states of a person we are communicating with is the core of emotional intelligence. Emotional intelligence is a facet of human intelligence that has been argued to be indispensable and perhaps the most important for successful interpersonal social interaction. This paper argues that next-generation human-computer interaction (HCI) designs need to include the essence of emotional intelligence - the ability to recognize a user's affective states-in order to become more human-like, more effective, and more efficient. Affective arousal modulates all nonverbal communicative cues (facial expressions, body movements, and vocal and physiological reactions). In a face-to-face interaction, humans detect and interpret those interactive signals of their communicator with little or no effort. Yet design and development of an automated system that accomplishes these tasks is rather difficult. This paper surveys the past work in solving these problems by a computer and provides a set of recommendations for developing the first part of an intelligent multimodal HCI-an automatic personalized analyzer of a user's nonverbal affective feedback.

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Toward an affect-sensitive multimodal human-computer interaction

Pattern recognition

This paper presents an efficient adaptive predistortion technique compensating for nonlinear distortions caused by a high-power amplifier (HPA) cascaded with a linear filter in an OFDM system. In the proposed approach, the memoryless HPA, preceded by a linear filter with memory in OFDM systems, is modeled by the Wiener system, which is then precompensated by the proposed adaptive predistorter with a minimum number of filter taps. It is confirmed by computer simulation that the proposed approach produces a faster convergence speed than the previous adaptive predistortion technique, and provides a small output backoff as low as 5.5 dB for an OFDM system employing an HPA with a linear filter.

On compensating nonlinear distortions of an OFDM system using an efficient adaptive predistorter

Echo watermarking marks audio signals by adding an echo. The embedded signal is not additive noise but an audio signal having the same statistical and perceptual characteristics. The echo is even perceived as added resonance. Conventional echo watermarking techniques often exhibit inherent trade-offs between imperceptibility and robustness. A new echo embedding technique is proposed. The proposed method enables one to embed high energy echoes while the host audio quality is not deteriorated, so that it is robust to common signal processing modifications and resistant to tampering. This is possible due to echo kernels that are designed based on psychoacoustic analyses. Subjective and objective evaluations confirmed that the proposed method could improve the robustness without perceptible distortion.

New echo embedding technique for robust and imperceptible audio watermarking

The authors describe a bit rate reduction algorithm for use in digital VCRs, based on block scrambling and the two-dimensional adaptive discrete cosine transform. This method satisfies many of the demands unique to digital VCRs. Before the encoding process, the input image is divided into 8*8 pixel blocks and then scrambled on a block-by-block basis to achieve efficient bit distribution in a frame and to simplify buffer control strategy. In addition to block scrambling, a simple yet efficient variable length coding method is proposed. Simulation results are presented. >

Bit Rate Reduction Algorithm For A Digital VCR

This article concerns the linearization of a nonlinear system by connecting a nonlinear Volterra prefilter tandemly with the nonlinear system and by adaptively adjusting the coefficients of the prefilter. "A nonlinear filtered-x LMS algorithm" for updating the coefficients of a nonlinear prefilter, as proposed, is shown to be viewed as an extension of the well-known filtered-x LMS algorithm.

An adaptive nonlinear prefilter for compensation of distortion in nonlinear systems

This article presents an adaptive precompensation technique for the Wiener system: a class of nonlinear systems that can be represented by the interconnection of a linear dynamic subsystem and a memoryless nonlinear subsystem. An adaptive algorithm for adjusting the parameters of the precompensator, structured by a Hammerstein model, is derived using the stochastic gradient method. The validity of the proposed algorithm is confirmed in a computer simulation by applying it to known Wiener systems.

Dae Hee Youn

Papers

On compensating nonlinear distortions of an OFDM system using an efficient adaptive predistorter

New echo embedding technique for robust and imperceptible audio watermarking

Bit Rate Reduction Algorithm For A Digital VCR

An adaptive nonlinear prefilter for compensation of distortion in nonlinear systems

Adaptive precompensation of Wiener systems