No. 2 (2014)
Published:
2014-06-30
ARTICLES FROM THIS ISSUE
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Digital Fingerprinting Based on Quaternion Encryption Scheme for Gray-Tone Images
Abstract
In this paper a new idea of digital images fingerprinting is proposed. The method is based on quaternion encryption in the Cipher Block Chaining (CBC) mode. Quaternions are hyper-complex numbers of rank 4 and thus often applied to mechanics in three-dimensional space. The encryption algorithm described in the paper is designed for graytone images but can easily be adopted for color ones. For the encryption purpose, the algorithm uses the rotation of data vectors presented as quaternions in a three-dimensional space around another quaternion (key). On the receiver’s side, a small amount of unnoticeable by human eye errors occurs in the decrypted images. These errors are used as a user’s digital fingerprint for the purpose of traitor tracing in case of copyright violation. A computer-based simulation was performed to scrutinize the potential presented quaternion encryption scheme for the implementation of digital fingerprinting. The obtained results are shown at the end of this paper.
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Robust Audio Watermarks in Frequency Domain
Abstract
In this paper an audio watermarking technique is presented, using log-spectrum, dirty paper codes and LDPC for watermark embedding. This technique may be used as a digital communication channel, transmitting data at about 40 b/s. It may be also applied for hiding a digital signature, e.g., for copyright protection purposes. Robustness of the watermarks against audio signal compression, resampling and transmitting through an acoustic channel is tested. In this paper an audio watermarking technique ispresented, using log-spectrum, dirty paper codes and LDPCfor watermark embedding. This technique may be used asa digital communication channel, transmitting data at about40 b/s. It may be also applied for hiding a digital signature,e.g., for copyright protection purposes. Robustness of the watermarks against audio signal compression, resampling andtransmitting through an acoustic channel is tested.
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Utilization of the SOA Deep Saturation and Power Averaging Effect to Counteract Intra-Channel Crosstalk in DWDM System
Abstract
The Semiconductor Optical Amplifier (SOA) is a key component of cost-effective short/medium range transmission systems. However it can introduce signal distortions. In this paper the authors investigate the possibility to reduce the signal distortions in SOA operating with the multiple wavelength channels. Using numerical simulations the negative influence of the nonlinear effects, namely cross-gain modulation (XGM) and the patterning effect can be reduced in deep SOA saturation regime. The self-healing effect is pronounced for the 4 or more wavelength channels and the transmitted symbol length longer than double of the SOA recovery time
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Design of WDM Transmission System for Medical Data Exchange
Abstract
This paper describes design of the Wavelength Division Multiplexing (WDM) transmission system using Alien Wavelength channels for medical data exchange. Main purpose of such system is to develop variety of services for medical cases diagnostics in order to comply with modern standards in telemedicine. Those standards refer to photo or video data transmission produced by diagnostic devices used in radiological centers together with text data concerning medical case analysis and patient data. These features are delivered by Picture Archiving and Communication System (PACS). PACS describes intra-hospital network organization, which applies to constructing system data from raw graphical data and text information according to Digital Imaging and Communications in Medicine (DICOM) version 3.0 standard. This standard is used by authors to evaluate necessary bit rate concerning all types of services delivered by PACS and cumulative throughput of link connections between hospitals and databases. Organization of this connections in metropolitan WDM system using advantages of Alien Wavelength technique is this article the main goal. Difference between configurable and non-configurable 10 Gigabit Small Form Factor Pluggable (XFP) end devices for Alien Wavelength channels are analyzed and compared with the standard approach using transponder cards.
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Radio Channels Modeling for Adaptive Antennas Applications – Analysis of Elevation, Azimuth and Delay Spread
Abstract
Research of modeling urban environment channel has been presented in this paper. Measurements were performed for 2.2 GHz band. Test environment was based on existing 3G sites. Elevation, delay and azimuth spreads were analyzed. Both theoretical channel modeling and similar tests campaign were subject for analysis in this paper. Based on radio channel modeling further investigations are presented and the adaptive antenna implementation was proposed.
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Enhancing Security of Advanced Metering Infrastructure by Introducing Threshold Attendance Protocol
Abstract
The industry pushes towards Smart grid systems in order to resolve current limitations of the unidirectional legacy power grid infrastructure. By introducing Advanced Metering Infrastructure (AMI) as an integral part of the Smart grid solution, the utility company obtains an invaluable tool to optimize its network, lower the operational costs, and improve quality of service. Unfortunately, introducing two-way communication poses a security risk to the power grid infrastructure. In this paper the authors consider a Threshold Attendance Protocol (TAP) acting in a reverted security paradigm. Its main idea is to keep the network load at a predictable level at all times. To achieve that, TAP in AMI environment is embedded and the solution using real-life simulation parameters is validated.
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New Metric for World Wide Web Service Quality
Abstract
The main topic of this paper is the quality of the WWW service evaluation. The authors present well-known measurement methods, and present the new “Power” metric for quality, advocating it as a method of assessing the quality of such service. This metric is based on the most important network parameters that affect any assessment of the WWW service, i.e. Web page opening time and download data transfer rate. The new method is easy to implement, fast in operation, and provides stable and repeatable results.
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Music Recommendation System
Abstract
The paper focuses on optimization vector content feature for the music recommendation system. For the purpose of experiments a database is created consisting of excerpts of music files. They are assigned to 22 classes corresponding to different music genres. Various feature vectors based on low-level signal descriptors are tested and then optimized using correlation analysis and Principal Component Analysis (PCA). Results of the experiments are shown for the variety of feature vectors. Also, a music recommendation system is presented along with its main user interfaces.
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A Detector of Sleep Disorders for Using at Home
Abstract
Obstructive sleep apnea usually requires all-night examination in a specialized clinic, under the supervision of a medical staff. Because of those requirements it is an expensive and a non-widely utilized test. Moving the examination procedure to patients’ home with automatic analysis algorithms involved will decrease the costs and make it available for larger group of patients. The developed device allows all-night recordings of the following biosignals: three channels ECG, thoracic impedance (respiration), snoring sounds and larynx vibrations. Additional information, like patient’s body position changes and electrodes’ attachment quality are estimated as well. The reproducible and high quality signals are obtained using the developed and unobtrusive device.
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Cassiopeia – Towards a Distributed and Composable Crawling Platform
Abstract
When it comes to designing and implementing crawling systems or Internet robots, it is of the utmost importance to first address efficiency and scalability issues (from a technical and architectural point of view), due to the enormous size and unimaginable structural complexity of the World Wide Web. There are, however, a significant number of users for whom flexibility and ease of execution are as important as efficiency. Running, defining, and composing Internet robots and crawlers according to dynamically-changing requirements and use-cases in the easiest possible way (e.g. in a graphical, drag & drop manner) is necessary especially for criminal analysts. The goal of this paper is to present the idea, design, crucial architectural elements, Proof-of-Concept (PoC) implementation, and preliminary experimental assessment of Cassiopeia framework, i.e. an all-in-one studio addressing both of the above-mentioned aspects.
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Mobility-Aware, Correlation-Based Node Grouping and Selection for Cooperative Spectrum Sensing
Abstract
Cooperative spectrum sensing has been proposed as a solution to increase the sensing function accuracy in cognitive radio networks, but the research has, so far, mainly focused on static scenarios, all but neglecting the impact of mobility on spectrum sensing. In this work a novel cooperative spectrum sensing scheme for mobile cognitive networks, based on a correlation-based, mobility-aware node selection algorithm is proposed. Correlation among sensing decisions is used to divide nodes into groups, and mobility is taken into account in the group leaders selection by means of a node selection metric that considers both sensing performance and mobility. Performance of the proposed algorithm is evaluated by computer simulations taking into account mobility and a detailed modeling of temporal and spatial correlation of fading and shadowing components in the channel path loss, going way beyond the performance evaluation carried out in previous works on correlation-based cooperative sensing schemes. Simulation results highlight that the proposed metric leads to a significant increase of the update period required to maintain acceptable sensing performance, and correspondingly to a strong reduction in the overhead caused by the grouping and node selection procedure.
