Advanced Digital Signal Processing Research Articles

Signal Processing in the Encrypted Domain

Recent advances in digital signal processing enabled a number of new services in various application domains, ranging from enhanced multimedia content production and distribution, to advanced healthcare systems for continuous health monitoring. At the heart of these services lies the ability to securely manipulate “valuable” digital signals in order to satisfy security requirements such as intellectual property management, authenticity, privacy, and access control. Currently available technological solutions for “secure manipulation of signals” apply cryptographic primitives by building a secure layer on top of existing signal processing modules, able to protect them from leakage of critical information, assuming that the involved parties or devices trust each other. This implies that the cryptographic layer is used only to protect the data against access through unauthorized third parties or to provide authenticity. However, this is often not enough to ensure the security of the application, since the owner of the data may not trust the processing devices, or those actors that are required to manipulate them. It is clear that the availability of signal processing algorithms that work directly on encrypted signals would be of great help for application scenarios where signals must be produced, processed, or exchanged securely. Whereas the development of tools capable of processing encrypted signals may seem a formidable task, some recent, still scattered, studies, spanning from secure embedding and detection of digital watermarks and secure content distribution to compression of encrypted data and access to encrypted databases, have shown that performing signal processing operations in encrypted content is indeed possible. We are delighted to present the first issue of a journal, entirely devoted to signal processing in the encrypted domain. The issue contains both survey papers allowing the reader to become acquainted with this exciting field, and research papers discussing the latest developments. The first part of the special issue contains three survey papers: Fontaine and Galand give an overview of homomorphic encryption, which is one of the key tools for signal processing in the encrypted domain, in their paper “A survey of homomorphic encryption for nonspecialists.” An introduction to the field of securemultiparty computation is provided by the paper “Secure multiparty computation between distrusted networks terminals” by Cheung and Nguyen. Finally, research in the area of signal processing under encryption is surveyed in the paper “Protection and retrieval of encrypted multimedia content: when cryptography meets signal processing” by Erkin et al. The second part of the special issue contains four research papers. Orlandi et al. introduce the notion of oblivious computing with neural networks in the paper “Oblivious neural network computing via homomorphic encryption.” Troncoso-Pastoriza and Perez-Gonzalez present new protocols for zero-knowledge watermark detection in their paper “Efficient zero-knowledge watermark detection with improved robustness to sensitivity attacks.” Prins et al. show in their paper “Anonymous fingerprinting with robust QIMwatermarking techniques” how advanced quantizationindex-modulation watermarking schemes can be used in conjunction with buyer-seller watermarking protocols. Finally, Gschwandtner et al. explore properties of specialized image encryption schemes in their paper “Transmission error and compression robustness of 2D chaotic map image encryption schemes.” Finally, we would like to thank all the authors, as well as all reviewers, for their contribution to this issue. We hope that the readers will enjoy this special issue and that it encourages more colleagues to devote time to this novel and exciting field of research.

Knowledge based system with embedded intelligent heart sound analyser for diagnosing cardiovascular disorders

Cardiovascular disease (CVD) is the leading cause of death worldwide, and due to the lack of early detection techniques, the incidence of CVD is increasing day by day. In order to address this limitation, a knowledge based system with embedded intelligent heart sound analyser (KBHSA) has been developed to diagnose cardiovascular disorders at early stages. The system analyses digitized heart sounds that are recorded from an electronic stethoscope using advanced digital signal processing and artificial intelligence techniques. KBHSA takes into account data including the patient's personal and past medical history, clinical examination, auscultation findings, chest x-ray and echocardiogram, and provides a list of diseases that it has diagnosed. The system can assist the general physician in making more accurate and reliable diagnosis under emergency conditions where expert cardiologists and advanced equipment are not readily available. To test the validity of the system, abnormal heart sound samples and medical data from 40 patients were recorded and analysed. The diagnoses made by the system were counter checked by four senior cardiologists in Malaysia. The results show that the findings of KBHSA coincide with those of cardiologists.

New technology approach needed for mining industry

Rob Gordon of Quantec Geoscience, Toronto, Canada suggests that improved mining exploration results will only come with acceptance of new geoscience and other technology. Fundamental methodologies for mining exploration are finally benefiting from the precedent of the oil industry. The technologies used in 3D distributed seismic systems have now been applied to electrical earth imaging. Recent advances in digital signal processing and faster computers, coupled with the ability to collect very high resolution and deep geophysical data, means that physical property contrasts can now be discriminated from the surface with accuracy and depth penetration not previously seen. This provides new opportunities to further geoscientific investigation in mining environments at greater depths prior to drilling. Maximum value and more realizable returns are demanded from exploration expenditures today. Now the mining industry can systematically interrogate the ground in the search for orebodies while essentially sterilizing unfavourable ground in the process. In addition, as the oil sector continues to seek improvements in technology to increase exploration success rates, it has begun to experiment with electrical methods again. This technology should prove quite interesting to the forward looking groups in both sectors. Making a discovery is difficult and is arguably more difficult as undiscovered deposits today are more likely found at greater depths. The financial risk of deep drilling is hindering deep exploration. However, the mining industry has been traditionally slow to embrace new technology particularly if it is not easily understood or when the cost paradigm is out of sync with traditional spending habits regarding drilling versus other technologies. Drill targeting has to be more focused thereby providing better returns per metre drilled. In essence, high potential ground may gp be under-explored. Economists have often said a critical failure in exploration is the inefficiency even while targeting highly prospective regions. Today, imaging to depths of over 1500 m can assist with deeper exploration within favourable land packages. Moreover, technology can now provide a means to revitalize exploration in mature mining camps. A ‘bottom-up’ vs ‘top-down’ exploration process begins to address economic concerns about drilling risk and discovery rates.

Optimal sensor design and digital signal processing techniques for remote field eddy current testing

Applications of remote field eddy current testing are severely restricted by disadvantages such as weak signals and over-long sensors. New methods used to overcome these disadvantages are investigated as follows: firstly, optimal sensor design methods including shielding and magnetic circuits are introduced to shorten the length of the sensor and enhance signal magnitude, and finite element method (FEM) is used to determine appropriate sensor length so as to get an optimal design compromise between sensitivity and signal magnitude. At the same time, a data acquisition system with orthogonal lock-in amplifier is used for weak signal measurement. Secondly, advanced digital signal processing techniques such as the homomorphic filter, wavelet transform and error correction are investigated to ensure detection reliability. Lastly, experimental results are presented showing that better performance has been achieved.

Real time digital signal processing implementation for an APD-based PET scanner with phoswich detectors

Recent progress in advanced digital signal processing provides an opportunity to expand the computation power required for real time extraction of event characteristics in avalanche photodiode (APD)-based Positron Emission Tomography (PET) scanners. These developments are made possible by a highly parallel data acquisition (DAQ) system based on an integrated analog front-end and a high-speed fully digital signal processing section that directly samples the output of each preamplifier with a free-running, off-the-shelf, 45-MHz analog-to-digital converter that feeds the sampled data into a field programmable gate array (FPGA) VirtexII PRO from Xilinx. This FPGA features /spl sim/ 31 000 logic cells and two PowerPC processors, which allows up to 64 channels to be processed simultaneously. Each channel has its own digital signal processing chain including a trigger, a baseline restorer and a timestamp algorithm. Various timestamp algorithms have been tested so far, achieving a coincidence timing resolution of 3.2-ns full-width at half-maximum (FWHM) for APD coupled to Lutetium Oxyorthosilicate (APD-LSO) and 11.4-ns FWHM for APD coupled to Bismuth Germanium Oxide (APD-BGO) detectors, respectively. Channels are then multiplexed into a DSP processor from Texas Instruments for crystal identification by an ARMAX recursive algorithm borrowed from identification and vector quantization theory. The system can sustain an event rate of 10 000 events/s/channel without electronic dead time.

Advanced digital signal processing techniques for compensation of nonlinear distortion in wideband multicarrier radio receivers

One of the main trends in the evolution of radio receivers and other wireless device is to implement more and more of the receiver functionalities using digital signal processing (DSP). However, due to practical limitations in the analog-to-digital conversion process, some analog signal processing stages are likely to remain also in the continuation. With the ever-increasing demands for the system performance and supported data rates on one side, and the terminal flexibility and implementation costs on the other, the requirements for these remaining analog front-end stages become extremely challenging to meet. Then, one interesting idea in this context is to apply sophisticated DSP-based techniques to compensate for some of the most fundamental nonidealities of the receiver analog front-ends. In this paper, we focus on developing and demonstrating novel digital techniques to mitigate the effects of harmonic and intermodulation distortion in wideband multicarrier or multichannel receivers using adaptive interference cancellation. The approach in general is practically oriented and largely based on analyzing and processing measured real-world receiver front-end signals. The obtained results indicate that the proposed compensation technique can be used to suppress nonlinear distortion due to receiver front-end sections under realistic signaling assumptions

Efficiency is its Own Reward

This article illustrates features of a state-of-the-art semiconductor factory called RFAB that Texas Instrument (TI) is building. When fully operational, the $3 billion fabrication plant will make TI's most advanced digital signal processors, destined for cell phones, disk drives, and anti-lock brakes. The white roof of the RFAB under construction in Richardson, Texas, reflects away some 85 percent of incoming sunlight, reducing cooling loads. Daylight reflected-off of window shelves in the administrative wing reduces the need for artificial lighting, while the Ergolights hanging from the ceiling are designed with sensors and will shut off automatically when no one is in the office. Due to technological advances in Asia over the past two decades, facilities in China, Korea, or Japan can turn out high-tech devices that are virtually indistinguishable from those made in the United States or Europe.

Transmission of images over general packet radio services using advanced wavelet image codecs and digital signal processor chips

We develop a wavelet-based codec using a low-cost and low-energy-consuming 16-bit fixed-point digital signal processor (DSP). The target application is designed to grab an image from a camera, code the image using a wavelet-based codec, and send a coded file over a wireless global system for mobile communications/general packet radio services (GSM/GPRS) network. Since the channel capacity of the GSM/GPRS network is limited, a DSP with a relatively low computational power is sufficient to implement an image codec. A trade-off is made between the complexity and the efficiency of the wavelet-based image coder. Any implementation issues concerning the wavelet transform and entropy coding are discussed. Lifting schemes for a 9-7 and a 5-3 filter bank are used. The novel ordering of bit-plane bits is presented. The proposed codec is comparable with a JPEG2000 codec in the rate-distortion sense. The experimental results show that the implementation of JPEG 2000 on the presented platform runs 60% slower than the proposed codec. The coded file is transmitted over a wireless network using Internet protocol/user datagram protocol/trivial file transfer protocol (IP/UDP/TFTP).

Digital signal processing methods of global nonparametric frequency domain audio testing

In this paper we propose advanced digital signal processing methods of nonparametric frequency domain audio system distortion testing. The traditional frequency domain audio tests are based on the theory of electrical networks and are suitable for local distortion characterization only. Locality points at the dependency on simple distortion models and test signal characteristics. Local tests are of only low significance, if digital audio systems have to be tested. Iterative test methods are known which are based on representative models of weakly nonlinear systems. These tests can be extended to result in global characterizations that are obtained under typical operating conditions. Global tests estimate the frequency response and, based on this linear characterization, the power spectral density of the nonlinear distortion contributions. In addition to the already known high efficiency frequency response test signal types of multitone signals or chirp-signals, we propose the use of maximum length sequences which give superior results w.r.t. accuracy and convergence speed not only for measuring the frequency response but also for measuring the distortion power spectral density. If desired, the distortion power spectral density can be also measured as part of an offline or an online test setup with any appropriate signals like music signals.

Implementation of a 50-kW four-phase switched reluctance motor drive system for hybrid electric vehicle

A high-performance fully digital controller has been designed for the drive of a 50-kW four-phase switched reluctance (SR) motor built for a hybrid electric vehicle (HEV). The SR machine is specifically designed and manufactured to have high power density and low acoustic noise. The controller is based on the advanced digital signal processor (DSP) with internal CAN interface-TMS320F2406 and complex programmable logic device (CPLD)-EPM7128S. The experimental results show that the controller is met with the system specification and requirement, satisfactorily.

Analysis of UHF Signal Using Prediction Model

With increasing interest in the reduction of cost for operation and maintenance of SF/sub 6/ gas-insulated switchgear (GIS), various methods of condition monitoring have been developed and used in conjunction with highly sensitive sensors and advanced digital signal processing techniques. Detection of partial-discharge signals in GIS using ultra-high frequency (UHF) technique has gained wide acceptance in research and industry. Unlike approaches of fast Fourier transformation and discrete wavelet transformation (DWT), a novel method of using an adaptive linear combiner as a prediction model to analyze UHF signals is introduced in this paper. Successful results are obtained by applying this new method on field data measured by a UHF coupler. The feasibility of this new approach is studied and proved by the statistical distributions of the trained weights.

On-Line Fuel Identification Using Digital Signal Processing and Fuzzy Inference Techniques

This paper presents a novel approach for on-line fuel identification using digital signal processing (DSP) and fuzzy inference techniques. A flame detector containing three photodiodes is used to derive multiple signals covering a wide spectrum of the flame from infrared to ultraviolet through visible band. Advanced digital signal processing and fuzzy inference techniques are deployed to identify the dynamic fingerprints of the flame both in time and frequency domains and ultimately the type of coal being burnt. A series of experiments was carried out using a 0.5-MW/sub th/ combustion test facility operated by RWE Innogy plc, UK. The results obtained demonstrate that this approach can be used to identify the type of coal being burnt under steady combustion conditions.

Digital Image Processing Techniques for Automatic Textile Quality Control

This article dealth with a complex problem of textile quality control by the means of computer vision using advanced digital signal and image processing tools. An investigation into a computer vision solution to quality inspection of textiles suggested a texture analysis approach. Since each texture analysis method presents a different potential for analysis of textured textile images, a large number of standard approaches from this category was examined. By considering their advantages and potential for successful flaw detection performance in homogeneous and jacquard textiles, six standard texture analysis techniques were identified for further investigation. A comprehensive examination and evaluation of these chosen techniques resulted. Normalised cross-correlation and SCLC approaches were identified as suitable candidates for real-time flaw detection in textiles with homogeneous structure.Inspection of jacquard textiles, however, presents a problem of greater complexity, the solution to which has not as yet been documented in the literature. To address this problem, a need for the application of a comprehensive cojoint spatial-spatial frequency approach was identified. A Gabor filter approach was chosen as a suitable representative of this class of techniques. This research then successfully applied optimised 2-D Gabor filters to the textile flaw detection problem and provided a further support of their suitability for this task.A novel optimised 2-D Gabor algorithm presented in this study is an automatic solution which is adaptable to detect a large variety of textile flaw types, both structural and tonal.

An advanced real-time digital signal processing system for linear systems emulation, withspecial emphasis on network and acoustic response characterization

A fast digital signal processing (DSP) system is described that can perform real-timeemulation of a wide variety of linear audio-bandwidth systems and networks,such as reverberant spaces, musical instrument bodies and very high order filternetworks. The hardware design is based upon a Motorola DSP56309 operating at 110million multiplication-accumulations per second and a dual-channel 24 bit codecwith a maximum sampling frequency of 192 kHz. High level software has beendeveloped to express complex vector frequency responses as both infinite impulseresponse (IIR) and finite impulse response (FIR) coefficients, in a form suitable forreal-time convolution by the firmware installed in the DSP system memory. Analgorithm has also been devised to express IIR filters as equivalent FIR structures,thereby obviating the potential instabilities associated with recursive equations andnegating the traditional deficiencies of FIR filters respecting equivalent analoguedesigns. The speed and dynamic range of the system is such that, when sampling at48 kHz, the frequency response can be specified to a spectral precision of 22 Hz;when sampling at 10 kHz, this resolution increases to 0.9 Hz. Moreover, it is alsopossible to control the phase of any frequency band with a theoretical precision of10−5 degrees in all cases. The system has been applied in the study of analogue filter networks,real-time Hilbert transformation, phase-shift systems and musical instrument bodyemulation, where it is providing valuable new insights into the understanding ofpsychoacoustic mechanisms.

Satellite mobile communications spread-spectrum receiver

Since 1999, ESA has conducted a number of system studies and technological developments to support the European and Canadian industry in the definition of a Satellite UMTS (S-UMTS) component development strategy, identifying critical technological areas and promoting S-UMTS demonstrations. In particular, the MUSIC project has successfully demonstrated advanced digital signal processing techniques to mitigate CDMA interference in spread-spectrum receivers, thus increasing the capacity and/or quality of service of a wireless communication network. The low-complexity solution for interference mitigation investigated and developed in the project is particularly suited for being implemented in mobile terminals.

Computer-aided diagnostics, data collection, data warehousing and mining system for handguns

Two PC-based monitoring systems for evaluating the performance characteristics of the trigger-pull mechanism of handguns, function and target testing, and managing test data have been designed and implemented. The frost system, Trigger Pull Monitor, uses a custom designed load cell and a Laser system to collect approximately 54,000 of equally spaced load and Cylinder stop position data points on real-time. The acquired data points which are 0.0001 inches apart are plotted for visual inspection and analyzed on real time to detect any possible fault associated with the trigger pull mechanism. Advanced digital signal processing is extensively used for filtering, integration and trigger roughness detection. Test results are archived in appropriate data marts and used later for performing statistical process control, and generating reports. At the begirming of each fiscal year, old test data is moved to a data warehouse which will be used for fbture mining. Stored data can be easily searched, using serial numbers, to look at the history of the gun [1]. The second systen Range Data Collection System is used for tinction and target testing of handguns. Faults and malfunctions related to functioning, accuracy and dispersion are detected by the shooterlinspector in the range and entered into this system. Collected data is archived in the data marts to be used

Signal processing challenges for applying software radio principles in future wireless terminals: an overview

AbstractThe general idea of software radio is to develop highly integrated radio transceiver structures with high degree of flexibility and multimode capabilities, achieved through increased role of digital signal processing software in defining the functionalities which have traditionally been implemented with analog RF techniques. This paper explores the software radio concept from the receiver architecture and signal processing points of view, with mainly the wireless terminal application in mind. We first discuss the critical issues in alternative receiver architectures with simplified analog parts and increased configurability. We also introduce certain advanced digital signal processing techniques which could potentially relieve some of the essential problems and pave the way towards DSP‐based, highly integrated, and highly configurable terminals. Big emphasis is on efficient digital multirate signal processing methods and complex (I/Q) signal processing. Copyright © 2002 John Wiley & Sons, Ltd.

Data acquisition and interferogram data treatment in FT-IR spectrometers

Traditional FT-IR spectrometers use the zero crossings of an interferogram from a control HeNe laser as a trigger signal for digitizing the analog signal of the main interferometer. Usually, successive approximation analog to digital converters (ADCs) with 16 to 20 bit resolution with or without gain ranging functions are employed. Advances in digital signal processing and progress in Audio-CD and DVD recording have brought a new breed of ADCs with higher resolutions, but with the apparent disadvantage of a fixed digitization rate. Initially, this kind of ADC (“Delta Sigma” ADC) could not be used in FT-IR spectrometers because FT-IR data acquisition requires that the infrared signal be digitized at equal increments of optical path difference. However, in a paper published by J. Brault it was shown that it is possible to use these “Delta Sigma” ADCs very efficiently in FT-IR instrumentation by simultaneously sampling both the analog signal of the main interferometer and the rate of change of the optical path difference. Digital signal processing then allows recalculation of the interferogram at the traditional zero crossings of the interferogram of the HeNe laser, and subsequent calculation of the spectrum. Differences between the traditional approach using successive approximation ADCs and state of the art “Delta Sigma” ADCs are shown, along with additional data processing functions that enhance the usability of the spectrometer.

Ultrasonic non-destructive on-line estimation of the tensile stiffness of a running paper web

A new method for measuring the elastic properties of paper on-line in a paper machine by using ultrasound has been developed. The unique feature of the method is that a continuous stochastic ultrasonic signal is used for measurements, which is generated by means of a dry friction between a running paper web and a rigidly fixed friction head. The signals from the web are picked up by an array of air-coupled ultrasonic receivers, which have no mechanical contact with the paper web. The ultrasound velocity in the web is obtained by means of the correlation processing. By using advanced digital signal processing, the tensile stiffness index (TSI) of the running web is determined. From the sensor we get the TSI values both in the machine direction and the cross-machine direction. The on-line ultrasonic sensors have been installed on two different paper machines for more than two years. This paper describes the background of the method, as well as some experiences and applications from two mill installations.

Design of fault-tolerant large-scale VOD servers: With emphasis on high-performance and low-cost

Recent technological advances in digital signal processing, data compression techniques, and high-speed communication networks have made Video-on-Demand (VOD) servers feasible. A challenging task in such systems is servicing multiple clients simultaneously while satisfying real-time requirements of continuous delivery of objects at specified rates. To accomplish these tasks and realize economies of scale associated with servicing a large user population, a VOD server requires a large disk subsystem. Although a single disk is fairly reliable, a large disk farm can have an unacceptably high probability of disk failure. Furthermore, due to real-time constraints, the reliability requirements of VOD systems are even more stringent than those of traditional information systems. Traditional RAID solutions are inadequate due to poor resource usage. Thus, in this paper, we present alternative schemes which provide a high degree of reliability at low disk storage, bandwidth, and memory costs for on-demand multimedia servers. Moreover, we discuss some of the main issues and trade-offs associated with providing fault tolerance in multidisk VOD systems. We would like to impress upon the reader that one of the main points of this paper is the exposition of trade-offs and issues associated with designing fault-tolerant VOD servers. It is not the case that one fault tolerance scheme is absolutely better than another, but rather that one must understand the trade-offs as well as one's system constraints and then choose a fault tolerance scheme accordingly.