F.G.B. De Natale

A commutative digital image watermarking and encryption method in the tree structured Haar transform domain

In this paper a commutative watermarking and ciphering scheme for digital images is presented. The commutative property of the proposed method allows to cipher a watermarked image without interfering with the embedded signal or to watermark an encrypted image still allowing a perfect deciphering. Both operations are performed on a parametric transform domain: the Tree Structured Haar transform. The key dependence of the adopted transform domain increases the security of the overall system. In fact, without the knowledge of the generating key it is not possible to extract any useful information from the ciphered-watermarked image. Experimental results show the effectiveness of the proposed scheme.

Content-Based Image Retrieval by Feature Adaptation and Relevance Feedback

The paper proposes an adaptive retrieval approach based on the concept of relevance-feedback, which establishes a link between high-level concepts and low-level features, using the users feedback not only to assign proper weights to the features, but also to dynamically select them within a large collection of parameters. The target is to identify a set of relevant features according to a user query while at the same time maintaining a small sized feature vector to attain better matching and lower complexity. To this end, the image description is modified during each retrieval by removing the least significant features and better specifying the most significant ones. The feature adaptation is based on a hierarchical approach. The weights are then adjusted based on previously retrieved relevant and irrelevant images without further user-feedback. The algorithm is not fixed to a given feature set. It can be used with different hierarchical feature sets, provided that the hierarchical structure is defined a priori. Results achieved on different image databases and two completely different feature sets show that the proposed algorithm outperforms previously proposed methods. Further, it is experimentally demonstrated that it approaches the results obtained by state-of-the-art feature-selection techniques having complete knowledge of the data set.

An innovative computational approach based on a particle swarm strategy for adaptive phased-arrays control

In this paper a new approach to the control of phased arrays is presented and assessed. Starting from the adaptive array theory, a particle swarm strategy is used to tune the phase coefficients of the array in order to adaptively minimize/avoid the effects of interfering signals at the receiver. To show the effectiveness of the proposed approach, a selected set of numerical examples, concerned with linear as well as planar arrays, is presented. Furthermore, to evaluate the advantages of the particle swarm optimizer (PSO)-based strategy over state-of-art methods, a comparative study is carried out by analyzing the performance of the method in terms of both the signal-to-interference-plus-noise-ratio and resulting beam pattern. The achieved results, even though preliminary, seem to confirm that the PSO-based approach satisfactorily works and it generally outperforms previously proposed/state-of-art phase-only adaptive control strategies

Multimedia information broadcasting using digital TV channels

In this paper, the structure of a new system to broadcast multimedia information within a digital TV channel is outlined. The proposed scheme is based on the DSM-CC (digital storage media command and control) functions, and uses a newly developed protocol that allows to efficiently convey multimedia information. Such information has the same characteristics of HTML files used in WWW environments, as it may contain text, images, sounds and animation organized as hypertext. The transport structure used is the MPEG-2 transport stream, which is the most popular standardized platform for the development of new digital TV services. Prototype software was developed to encode the file system by means of DSM-CC operations and include it in a MPEG-2 compatible transport system.

Optimized design of a multifunction/multiband antenna for automotive rescue systems

The development of efficient automotive accident management systems requires the design of complex multifunction antennas enabling different wireless services (e.g., localization, voice and data communications, emergency calls, etc.). Starting from different specifications (electrical, mechanical, and aerodynamic), the design of a multifunction antenna must consider, in addition to the usual antenna design requirements, also interference phenomena arising from the integration of different classes of antennas in a compact device. In this framework, the paper describes a methodology based on a stochastic multiphases optimization approach for the design of an integrated multifunction/multiband antenna system. Moreover, for an exhaustive assessment, the results of an experimental validation performed on a prototype of the multifunction antenna system are shown and discussed.

Planar antenna array control with genetic algorithms and adaptive array theory

Planar arrays are successfully employed in radar and communication systems in order to allow three-dimensional-scanning. In the framework of real-time control of antenna arrays, starting from the Applebaum theory, this paper presents an approach based on a customized genetic algorithm aimed at adaptively eliminating interfering signals. Successful applications are presented in order to evaluate the effectiveness of the proposed approach in term of performances and computational complexity.

Adaptive anisotropic filtering (AAF) for real-time visual enhancement of MPEG-coded video sequences

Current standards for video compression achieve good performances in terms of data compaction and signal-to-noise ratio of the decoded signal. Nevertheless, there are some known problems concerning the visual quality of reconstructed images, which can be partially solved using appropriate post-processing algorithms. The paper proposes a new adaptive anisotropic filter (AAF) that aims to unify the treatment of different sources of perceptive distortion in MPEG sequences. The process is driven by a local classification of blocks and single pixels of decoded frames, taking into account several parameters (distribution of DCT coefficient energy, presence of sharp variations, spatial position of DCT block boundaries). Experimental results show that the proposed algorithm outperforms existing enhancement approaches, in particular when constraints on complexity and real-time processing are compelling.

Synthesis of a Prefractal Dual-Band Monopolar Antenna for GPS Applications

In this letter, the design of a monopolar dual-band antenna operating in the L1 and L2 GPS bands is presented. The prefractal geometry of the antenna has been synthesized by means of a particle swarm algorithm for optimizing the values of the electrical parameters within the specifications. For a general assessment, some selected results of numerical simulations are shown and some comparisons between numerical data and experimental measurements are presented

Watermarking Robustness Evaluation Based on Perceptual Quality via Genetic Algorithms

This paper presents a novel and flexible benchmarking tool based on genetic algorithms (GA) and designed to assess the robustness of any digital image watermarking system. The main idea is to evaluate robustness in terms of perceptual quality, measured by weighted peak signal-to-noise ratio. Through a stochastic approach, we optimize this quality metric, by finding the minimal degradation that needs to be introduced in a marked image in order to remove the embedded watermark. Given a set of attacks, chosen according to the considered application scenario, GA support the optimization of the parameters to be assigned to each processing operation, in order to obtain an unmarked image with perceptual quality as high as possible. Extensive experimental results demonstrate the effectiveness of the proposed evaluation tool.

A Joint Digital Watermarking and Encryption Method

In this paper a joint watermarking and ciphering scheme for digital images is presented. Both operations are performed on a key-dependent transform domain. The commutative property of the proposed method allows to cipher a watermarked image without interfering with the embedded signal or to watermark an encrypted image still allowing a perfect deciphering. Furthermore, the key dependence of the transform domain increases the security of the overall system. Experimental results show the effectiveness of the proposed scheme.