bluuebunny/crossref_metadata_2025 huggingface dataset:
Motion errors in an airborne synthetic aperture radar system
Authors: Buckreuss Stefan
Published: September 2008

The Institute for Radio Frequency Technology of the German Aerospace Research Establishment (DLR) in Oberpfaffenhofen operates an experimental synthetic aperture radar, E‐SAR. The Radar configuration was developed by DLR [1, 2] and consists of a L/C/X‐band SAR System and antennas with a wide beamwidth in azimuth and elevation. The system is installed in a small Dornier DO 228 aircraft, which operates at low altitudes between 1000 m ‐ 3000 m above ground. Due to atmospheric turbulences, the aircraft is displaced from its nominal flight path, causing a variation of the phase history of the returned radar signal. This eventually results in a degraded image quality and therefore a highly accurate motion compensation becomes necessary. It is intended to integrate an inertial measurement unit (IMU) within the E‐SAR system to support the used motion compensation algorithm during data processing [3]. The required relative accuracy of the IMU can be determined by means of statistics i.e. an approach is demonstrated to estimate the power spectral density (PSD) of the tolerable uncompensated aircraft motion. The performance of an IMU motion compensation system has been evaluated by analysis, as well as by computer simulation.
A fuzzy complete SAR processing chain for ship detection and velocity estimation
Authors: Alparone Luciano , Argenti Fabrizio , Benelli Giuliano , Cappellini Vito , Mecocci Alessandro
Published: September 2008

Environmental monitoring by means of Remote Sensing methodologies is one of the most interesting and important application field of image processing techniques. In this field, a very important role is played by Synthetic Aperture Radar (SAR) images, that posses an high spatial resolution and that can be produced in all weather conditions. This paper presents a complete digital signal processing chain for the automatic detection of ships in SAR images and for the computation of an estimate of ship velocities. A particular attention has been devoted to two problems: the prefiltering problem which aims to reduce the speckle noise in the image, and the robustness problem that is related to the optimization of the true‐target detection/rejection capability. The whole chain has been first simulated and tested on a sequential machine, namely a Micro VAX II, and then it has been ported on a parallel architecture based on a hyper‐cube of IMS T800 transputers.
Preliminary considerations for an efficient SAR ocean simulation
Authors: Migliaccio Maurizio , Riccio Daniele , Schirinzi Gilda
Published: September 2008

Some ideas toward a SAR raw data ocean simulator are presented. The suggested simulator is based on facets model of the ocean wave, two‐dimensional FFT code and asymptotic evaluation of the unit response function.

Two main useful features are here explored: the phase velocity of dominant ocean wave which is supposed to travel at constant velocity; and the Bragg‐resonant dominant scattering mechanism.
An algebraic approach for performance evaluation in microwave links using angle diversity
Authors: Coraiola Alessandro
Published: September 2008

This paper deals with the quality of a line‐of‐sight digital radio link using angle diversity reception.

Starting from a simple multipath model based on total reflections of the electromagnetic rays propagating in the atmosphere, a relation of delay between rays is inferred, which is linear with distance and, at least for long routes, is in accordance with experimental data.

The paper goes on with the description of a radio channel, both for «minimum phase» and «non‐minimum phase», and with a theoretical analysis of a hop quality.

Said analysis leads to consider the antenna characteristics, both in transmission and in reception, as basic components of the link performance and allows to conclude that the angle diversity may be used profitably if antennas with sufficiently narrow lobes are adopted.
Error probability evaluation in the presence of microwave oscillator phase noise
Authors: Buoli Carlo , Taverna Marcello , Ternau Wanda , Todero Franco
Published: September 2008

This work presents the theoretical calculation of the error probability as a function of the signal to noise ratio in presence of the oscillator phase noise in the 4 PSK and 16, 64, 256 and 1024 QAM systems. Experimental verifications confirm the computed values. On the basis of the procedure described herein, the design of two oscillators that operate in different modulation and capacity systems and with different values of the oscillation frequency is illustrated.
Performance of underlying hamming codes in M‐QAM digital radio systems with nonlinear distortions
Authors: Friederichs Karl‐Josef , Kovàts Janos
Published: September 2008

The performance of underlying Hamming codes in M‐QAM digital radio systems is analyzed in the presence of nonlinear distortions.

An effective soft‐decision decoding algorithm is constructed to reduce the number of errors induced by the nonlinear and noisy channel.

Then the residual bit error probability is calculated from the statistical estimations of the detector input samples. It is shown that for weakly and moderately nonlinear channels error correction coding can significantly improve the system performance.
On the nonbifurcated routing in virtual circuit communication networks
Authors: Zhang Zhigang , Hartmann Harro L.
Published: September 2008

The problem of optimal nonbifurcated routing in virtual circuit (VC) communication networks, such as the X.25 packet‐switched networks, the frame‐relay networks or the ATM networks, is considered. To describe the related characteristic of the generally asymmetrical transmit and receive traffic in such networks, a related multicommodity flow (RMCF) model with two traffic matrices is proposed. For solving the optimal flow assignment problem with this model, we present an algorithm which incorporates the transmit receive (TR) relation, an important practical constraint existing in most of the operational VC networks.

A comparison of the RMCF model with the symmetrical multicommodity flow (SMCF) model shows that the former is superior with respect to the network delay. Furthermore, performance degradation has been observed, which is caused by using the traditional multicommodity flow (MCF) model due to the lack of VC bandwidth reservation of the receive traffic. We also show the dependency of the network throughput on the traffic symmetry versus the TR ratio.
Telecommunications and the introduction of home networks for the residential market
Authors: Stienstra A. J. Bert , Van Vaalen Martin , Wage Joseph
Published: September 2008

Major changes are likely to occur in the telecommunications infrastructure. Both researchers and standardisation institutes are hard at work paving the way for a Broadband Integrated Services Digital Network (B‐ISDN). At one time it was widely assumed in the telecommunications world that once such a network had been established, customers would feel the need for a home network, which could be used for a wide range of purposes. However, a recent review of developments has made it very clear that the equipment which people have in their homes ‐ including telecommunications equipment ‐ falls into the category of consumer electronics. Consequently, the introduction of home networks for the private consumer will proceed in a rather less orderly fashion than telecommunications experts used to think.
Letter pointer overflows in SDH equipments
Authors: Brugia Odoardo , Carbonelli Marco , De Seta Domenico , Perucchini Daniele
Published: September 2008

Particular situations of pointer overflows, which can take place either in the presence of high amplitude wander on STM‐N signals entering SDH network elements or under severe failure conditions of the synchronization network, have been identified. In these situations waste of data results if no proper actions are carried out to handle pointer overflows. With reference to current regulations additional rules are proposed in order to avoid this kind of impairment on transported tributaries.
Letters wavelength selection via tunable birefringent optical fiber filters: A stimulated raman scattering light experiment
Authors: Gao Peijuan , Bassi Paolo , Zoboli Maurizio , Yang Tianlong , Jiang Shigan
Published: September 2008

The ability of a recently proposed birefringent all optical fiber filter in obtaining tunable wavelength selection is demonstrated using Stimulated Raman Scattering light. Three kinds of light: the pump light, the first order Stokes line and the second order Stokes line of a Nd:YAG laser have been extracted separately.
Numerical modeling of bends in optical rib and double rib waveguides
Authors: De Angelis Costantino
Published: September 2008

A new method is proposed to reduce radiation and transition losses in bent rib waveguides. Theoretical results have been obtained and a numerical analysis performed with the Beam Propagation Method (BPM) has been used to find total losses of the bends which have been studied. The results indicate that sharp bends with low loss should be feasible with a simple technology.
An open environment for ATM broadband multimedia applications
Authors: Franceschini Guido , Petrelli Daniela , Sciarappa Antonio , Venuti Giovanni
Published: September 2008

Advances in trasmission and switching technologies promise a flexible and efficient Broadband ISDN (B‐ISDN), based on Asynchronous Transfer Mode (ATM), able to meet the increasing demand of high speed services. Multimedia applications are in particular expected to play a key role in B‐ISDN success. The paper wants to outline the architecture of an open environment based on a multimedia workstation for ATM developed in the framework of the Italian Information Technology project called Piano Finalizzato Telecomunicazioni (PFT). Design guidelines, interfaces and capabilities are described. After introducing the basic workstation architecture, some aspects of relevant multimedia applications and of the user interface are discussed.
Current architectures for ATM implementation
Authors: Melen Riccardo
Published: September 2008

This paper is devoted to the classification and preliminary assessment of the ATM switching architectures which are likely to hit the market in the next few years as the B‐ISDN implementation phase will proceed. In the first part of the paper a top down approach is attempted in the classification of switching architectures, with the aim of giving an abstract view of the possible options and setting a common, clearly understandable framework for their comparison. This classification is used as a guideline for a review of the current trends in ATM switching. Both current prototypes by major manufacturers and other proposals which can become products and be part of public or private networks in the future are reviewed. The merits and shortcomings of these solutions are discussed, but no direct comparison is attempted, due to the different purpose and technological effort involved in the various projects which does not provide a fair basis for comparative evaluation.
Congestion control strategies in ATM networks
Authors: Fratta Luigi , Musumeci Luigi , Gallassi Giorgio , Verri Luigi
Published: September 2008

Asynchronous Transfer Mode (ATM) is a promising technique to implement the Broad‐band ISDN. When bursty sources are considered, high network efficiency can be obtained by taking advantage of statistical multiplexing. This technique requires to monitor the user behavior, in order to guarantee that the actual traffic parameters do not exceed the maximum values compatible with the required Grade of Service. The paper reviews the major results on the analysis of the control mechanisms. In particular, the three following issues are considered. The Connection Admission Control for both homogeneous and heterogeneous traffic sources is analyzed and the performance of different approaches are compared. The Leaky Bucket mechanism is studied for the Usage Parameter Control and its performance, such as reaction and recovery time, are analyzed. The traffic shaping function is considered in both cases of availability and non availability of a feedback on the traffic sources. The effectiveness of this functionality is investigated.
Performance analysis of trellis coded biorthogonal sequences in a variable rate system
Authors: Benvenuto Nevio , Chiaraluce Franco , Falcioni Paolo , Andreoli Sante
Published: September 2008

For digital communication systems with a given binary modulation scheme and variable information rate, a coding technique is described which employs a particular structure of trellis code. It consists of a convolutional encoder followed by a mapper which selects biorthogonal codewords. Based upon the state diagram of the system, performance is evaluated and then compared to that of more conventional solutions. Beside having good performance, this approach is very modular, i.e. its structure easily adapts to different information rates. Furthermore, it allows the time synchronization system to work at lower signal‐to‐noise ratios.
Letter a precise stereoscopic system with two video cameras
Authors: Tubaro Stefano
Published: September 2008

A basic problem in stereopsis is to find the correspondence between points in right and left images. This paper presents some results obtained with a stereo vision system composed by two CCD video cameras with parallel optical axes.

The presented results have been obtained using, to solve the correspondence problem, algorithms based on the comparison of the luminance profiles of the two images rather than based on the comparison of the binary images obtained after edge detection. These algorithms were originally conceived to allow motion compensated coding of TV sequences, but they are also very useful in solving the correspondence problem in stereopsis.

Experimental results obtained from laboratory tests and from a hardware realization of the system are presented. And, despite the simplicity of the proposed system, they are quite promising.
Letter improved analysis of the effects of stimulated raman scattering in a multi‐channel WDM communication system
Authors: Comuzzi R. , De Angelis C. , Gianello G.
Published: September 2008

A system of N first‐order differential equations, which describe N interacting channels in a WDM system affected by S.R.S., is solved numerically, under very general assumption, with the Runge‐Kutta method. Differential losses and different signals depletion rates are accounted for. The actual limitations imposed by SRS are evaluated and found to differ appreciably from previously published ones.
On the quantitative analysis of localized scattering centres in microwave images
Authors: Fuchs Ulrich , Wendel Horst
Published: September 2008

This paper introduces a new method to reveal the spectral information hidden in highly resolved microwave maps locally dominated by localized scattering centers. The method first partitions the map, i.e. it localizes these centers by suitable window function. It then transforms each segment containing a localized scattering center into frequency‐aspect angle space. The method is tested for a simulated scenario of two localized scatterers. Its superiority over previous exploitation schemes is borne out by applying it to experimental data on the edge scattering of a metal plate.
Spectral‐correlation based methods for multipath‐channel identification
Authors: Izzo Luciano , Napolitano Antonio , Tanda Mario
Published: September 2008

The paper deals with the problem of the estimation of the scaling amplitudes and the arrival times of a multipath signal. An extensive study of two new spectral‐correlation based estimation methods is presented. These algorithms are applicable as long as the multipath signal is cyclostationary. They are inherently tolerant to both noise and interference, and can, in principle, provide arbitrarily accurate estimates when a sufficiently long collect time is available. The methods are compared in terms of temporal resolution, arrival time dynamics and estimate accuracy. Finally, the performance of both considered methods is compared with that of conventional techniques based on temporal correlation.
Polarimetric signal processing of meteorological target observations with the DLR weather radar
Authors: Schroth Arno , Tragi Karl , Lüneburg Ernst , Chandra Madhukar
Published: September 2008

At DLR (formerly DFVLR) in Oberpfaffenhofen, Germany, a coherent polarimetric C‐Band radar is in operation since about three years for applications in microwave propagation (satellite communications) and cloud physics research. Its functional aspects are briefly described. The radar permits the characterization of scatter volumes consisting of statistically distributed targets like weather targets by a time series of scattering matrices as well as by the Stokes matrix or the covariance matrix. Special consideration is given to the microphysical interpretation of polarimetric radar echoes using the fundamental second moments (covariances). Polarization signatures for backscattered power and correlation observables are derived applying polarization transformations to the covariance matrix. Finally, typical signal degradations on Earth‐satellite paths are derived from actually measured radar data and compared with beacon measurements.
Novel analysis algorithm for binary CPM with h= 1/2 based on laurent's representation
Authors: Jung Peter
Published: September 2008

Laurent's representation of binary continuous phase modulations (CPMs) based on real impulses of finite duration is advantageous for the signal generation in the transmitter as well as the signal processing in the detector.

In the present paper, a novel algorithm for the determination of these impulses in simulation and experiment by the excitation of certain modulator responses shall be illustrated. The algorithm is an interesting alternative to conventional signal processing applying phase detection, thus allowing further insight in the nature of binary CPM.
An ARQ scheme with memory for mobile communications
Authors: Benelli Giuliano
Published: September 2008

An automatic‐repeat‐request (ARQ) scheme with memory is described in which the received vectors, even when detected in error, are retained to facilitate the correct recovery of the transmitted message. The optimization of the system parameters with the transmission channel affected by fading have been derived theoretically. The results of computer simulations performed to evaluate throughput show considerable improvement with respect to the classical ARQ protocols, making the proposed scheme especially suitable for mobile communications.
A survey of array error control codes
Authors: Farrell Patrick Guy
Published: September 2008

Array error control codes are linear block or convolutional codes which are constructed from several single parity check or other component codes, assembled in two or more geometrical dimensions or directions, with emphasis on simple component codes and low complexity methods of decoding. This survey attempts to introduce, relate and compare all known types of array codes and their applications. After an introduction to the basic properties and uses of array codes, the second section of the paper describes binary array code constructions for random, burst and cluster error control. The third section describes a number of binary convolutional array codes, for both random and burst error control. Non‐binary and byte‐oriented array codes, both block and convolutional, are covered in the fourth section, which mentions some quite powerful and yet practical constructions. The fifth section discusses various enhancements which can be applied to array codes. The paper ends with conclusions, open problems, and an extensive set of references.
A novel description of handwritten characters for use with generalised fourier descriptors
Authors: Niemel Leon‐Paul W. , Prasad Ramjee
Published: September 2008

A new description is developed for handwritten character recognition for Western style characters. Character recognition here is based on Generalised Fourier Descriptors (GFDs). The characters are described by sections which are either straight line pieces or arcs of circles. Analytical expressions exist for the GFDs of these two types of curves. In order to apply these expressions on handwritten characters, these characters are first curve‐fitted into straight line‐pieces and arcs of circles. After this description the GFDs can easily be calculated. Experiments were performed and preliminary, qualitative remarks on these are made.
Letter limit cycles in residue number system filters
Authors: Cardarilli Gian‐Carlo , Hasler Martin
Published: September 2008

The zero input limit cycle behavior of canonical second order sections of digital filters using a certain kind of Residue Number System (RNS) arithmetic are investigated. It is shown that constant and period two limit cycles are frequent in a large part of the linear stability triangle. Therefore, the designer should either modify the overflow and quantization characteristic, or use filter structures that are not plagued with limit cycles.
REFORMA ‐ a tool based on PC for telecom network optimization
Authors: Hackbarth Klaus‐Dieter , Ayllón Fátima García
Published: September 2008

This contribution presents the software tool REFORMA, which will support the tasks of telecommunication network planning departments. It is shown that REFORMA offers various possibilities for circuit demand routing, grouping and stand‐by network optimization applied to local and trunk networks with digital transmission systems. The large flexibility to implement different planning rules and network development strategies with REFORMA is demonstrated by some network examples. Further extensions and applications of this tool are also indicated.
Tunable twin‐guide (TTG) laser diodes with metal‐clad ridge‐waveguide (MCRW) structure for coherent optical communications
Authors: Wolf Thomas , Westermeier Heinz , Amann Markus‐Christian
Published: September 2008

Tunable twin‐guide (TTG) laser diodes with metal‐clad ridge‐waveguide (MCRW) structure were developed for advanced coherent optical communication systems at 1.55 μm wavelength. The essential advantage of these lasers over previous devices is the simplified handling due to the inherent continuous tuning behaviour enabling the unambiguous wavelength control by only one tuning current. With 400 μm long devices, threshold currents around 50 mA, optical output power levels above 10 mW and tuning ranges around 1.2 nm (150 GHz) are achieved by maintaining the linewidth below 4 MHz. With an optimized design a maximum continuous tuning range of 2 nm has been obtained.
Remote Sensing Data Fusion on Intelligent Terminals
Authors: Butini Francesco , Cappellini Vito , Fini Stefano
Published: September 2008

This paper focuses on the possibilities offered by intelligent terminals applied to multisensor image data processing. The state of the art of remote sensing and its future developments are briefly analyzed in order to underline the need of an intelligent use of the large amount of data that will be available in future years. Data fusion is introduced as an interesting technique both to combine data collected by remote sensors and to extract the information which is not available from each separate informative channel. Artificial neural networks are presented as a powerful tool to be used in data fusion processing because of their capability to process data without any a priori information of the data set. An example of neural network processing on multisensor airborne data is given in order to show the effective possibility offered by an intelligent terminal in high level processing of multisensor data.
A Comparison of Two Low Bit Rate Image Coders
Authors: Nunes Jorge F. , Marques Jorge S.
Published: September 2008

This paper presents an experimental comparison between aVQbased coder and a classical transform coder. In theVQcoder each 4x4 image block is vector quantized using Self‐Organizing Feature Maps (Kohonen Maps) which can be interpreted as structured codebooks. The codebook structure allows the use of fast search procedures which are described and experimentally evaluated. The transform coder uses the DCT to decorrelate the image values in each 8x8 block. The DCT coefficients are then encoded using a bank of Max‐Lloyd nonlinear quantizers followed by an arithmetic coder. Experimental tests are performed at bit rates between 0.5 and 0.75 bit/pixels. It is concluded that similar objective and subjective performances were achieved by both coders with the transform coder performing slightly better.
Coding Algorithms and VLSI Implementations for Digital TV and HDTV Satellite Broadcasting
Authors: Musmann Hans Georg , Pirsch Peter
Published: September 2008

Source coding techniques for reducing the bit rates of TV and HDTV signals are presented and discussed with respect to satellite broadcasting applications. The source coding techniques require transmission bit rates of 9 Mbit/s for a TV and 45 Mbit/s for an HDTV signal in order to provide distribution quality as required for broadcasting. Also three scalable coding schemes are outlined which allow graceful degradations at the boundary of the broadcasting service area by a transition from a HDTV to TV picture resolution. VLSI implementations of TV and HDTV decoders have been investigated in order to achieve compact and low cost realization. It is shown that the silicon area of VLSI devices can be kept small by choosing algorithms with small signal processing requirements and by taking advantage of a priori known features. VLSI architectures for the implementation of subband filters and DCT are discussed as key components.
VLSI Digital PSK Demodulator for Space Communication
Authors: Hansen Flemming , Thomsen Jan Harding , Jacobsen Freddy Lund , Olsen Karsten
Published: September 2008

This paper describes the design of a BPSK/QPSK demodulator implemented using multi‐rate digital signal processing in a CMOS ASIC. The demodulator is fully programmable via serial and parallel interfaces and handles symbol rates from 125 sym/s to 4 Msym/s. It performs at less than 0.5dB degradation from ideal BER vs. Eh IN characteristic. The system design considerations lead to the choice of a complex IF scheme with sampling at four times the intermediate frequency and a combined analog and digital matched filtering based on the pulselet concept. Signal processing algorithms include Costas carrier phase error detector, Zero‐Crossing Detector for timing error and algorithms for lock detection and loop filtering. Simulations of the entire demodulator including the ASIC part is accomplished by proprietary software. The ASIC is manufactured in a radiation tolerant 1 μm CMOS gate array process using 34085 gates. The main application area is spaceborne coherent TT&C transponders. The ASIC will fly on SPOT‐4 in 1994 as a part of the Experimental 5‐Band Transponder.
Satellite On‐Board Baseband Switching Architectures
Authors: Inukai Thomas , Pontano Benjamin A.
Published: September 2008

On‐board baseband processing has been actively pursued by a number of organizations for potential implementation in future communications satellites. This paper examines some of the benefits of on‐board regeneration, baseband processing, and switching. It describes alternate switching concepts, i.e., circuit switching and fast packet switching, their advantages and shortcomings, and potential applications for future commercial satellite communications. In particular, fast packet switching is a relatively new concept for on‐board applications and shows a great promise for the integrated operation of digital satellite networks. Key design issues for this system are also discussed. The paper presents several switch configurations for each type of switching concept, and a sample network architecture and its processing payload configuration for potential future communications satellites.
Application of an Evolutionary Model to Telecommunication Services
Authors: Olafsson Sverrir , Gell Michael
Published: September 2008

An evolutionary model drawn from biology is introduced. A method for its application to optimisation problems is developed and applied to the analysis of Videotex and Teletext services. It is shown that the evolutionary model has significant potential as a diagnostic tool for identifying trends in complex competitive systems.
Aggregation of Systems with HDLC Protocol
Authors: Sczittnick Michael , Uhl Tadeusz
Published: September 2008

The HDLC (High‐level Data Link Control) protocol has been accepted as an international standard for computer communication networks. In this paper an aggregated mathematical model for the performance analysis of a node with HDLC protocol will be presented that is still accurate concerning mean delay and losses. The model is intended to be used as a basic element in models for networks.
On Universal Noiseless Source Coding for Infinite Source Alphabets
Authors: Györfi László , Páli István , Van Der Meulen Edward C.
Published: September 2008

We show that there is a universal noiseless source code for the class of all coun‐tably infinite memoryless sources for which a fixed given uniquely decodable code has finite expected codeword length. This source code is derived from a class of distribution estimation procedures which are consistent in expected information divergence.
90° ‐ Rotationally Invariant Multilevel Convolutionally Encoded QAM
Authors: Henkel Werner , Koch Michael
Published: September 2008

A multilevel convolutional code construction is proposed that leads to low complexity rotationally invariant schemes with coding gains of around 6 dB. Conditions for 90° ‐ rotational invariance are derived, and a special structure for differential en/decoding is given. These considerations together with the introduction of a relation between information sequences, when determining the code generators, are the basis for the approach.
Bounds on the Cut‐Off Rate of the Peak Shift Magnetic Recording Channel
Authors: Shamai Shlomo , Kaplan Gideon
Published: September 2008

We address the peak shift channel, introduced recently by Shamai and Zehavi to provide a simple statistical model for peak shift generated errors in magnetic recording employing peak detectors. This impairment has been identified as a major cause of performance degradation in such devices. We examine the cut‐off rate, which is considered as a practical measure to reliable communication rates. Lower bounds on the cut‐off rate as well as the zero‐error and noiseless (ideal channel) cut‐off rates are derived and presented for some interesting parameters. It is shown that the cut‐off rate behaves similarly to capacity. We also show that interleaving degrades the performance considerably. The extended model of a peak shift channel concatenated in tandem with a binary symmetric channel, which accounts for both dominant impairments ‐ randomly as well as peak shift generated errors, is also treated and a lower bound on the corresponding cut‐off rate is presented.
A Proposition to Valuate Expanded Impulses in Pulse Radar Systems Using Optimum Unbiased Estimation
Authors: Felhauer Tobias , Zimmermann Thomas , Voigt Peter , Baier Paul Walter
Published: September 2008

In pulse radar systems using expanded impulses, in the receiver the usual method of signal processing is pulse compression by matched filters. When using this kind of signal processing, the autocorrelation sidelobes of the expanded impulse severely limit the detectability of small targets situated near large targets. By using an optimum unbiased estimator instead of a matched filter, the harmful effects of the autocorrelation sidelobes can be totally eliminated. It is first shown how the estimation theory known from other technical areas can be advantageously applied to the processing of expanded impulses in radar receivers. Secondly, new criteria for the valuation of expanded impulses are proposed. Such criteria are necessary because the autocorrelation peak‐to‐sidelobe ratio which is a suitable criterion in the case of matched filtering is no longer adequate if optimum unbiased estimation is used. The new criteria are applied to several well known expanded impulses as e.g. Frank coded and P3 coded waveforms. It is shown that waveforms which, on account of rather high autocorrelation sidelobes, would be ill suited in the case of matched filtering may be well suited in the case of optimum unbiased estimation.
Data Compression for Image Archiving Applications
Authors: De Natale Francesco G. B. , Desoli Giuseppe S. , Giusto Daniele D. , Vernazza Gianni
Published: September 2008

A novel approach to still‐picture data compression is presented that is based on the integration of two different coding techniques. Its aim is to obtain high‐compression factors by exploiting the characteristics of a second‐generation method (i.e., polynomial approximation) in suitable scene areas, while achieving higher fidelity, where required by the local image characteristics, through a first‐generation technique (i.e., vector quantization).

Such a region‐driven hybrid approach performs the integration by utilizing a control image (resulting from the detection of areas characterized by high spatial frequencies) that drives the segmentation and approximation processes.

The results obtained on a variety of natural color images are quite satisfactory. The visual quality of the reconstructed images is, in general, very good, and SNR is kept within an acceptable range. Moreover, the bit rate obtained is always below 0.15 bit/pixel (bit/pixel), with peak values of 0.07 bit/pixel.
Proposal of an all Optical Shuffle Multihop Network
Authors: Matera Francesco , Cnr Emilio Ripani , Romagnoli Marco , Settembre Marina
Published: September 2008

In this paper a shuffle multihop network, with a routing and a processing completely obtained at optical level, is proposed for the first time. Such a network can be performed by means of optical AND gates based on second harmonic generation and optical XOR gates based on soliton dragging process. Soliton pulses ape used to avoid the distortion caused by chromatic dispersion. The main characteristics of the network are a number of nodes equal to 64 and a bit rate among the users equal to 50 Gbit/s for a total throughput of about 1 Tbit/s.
Advanced Modulation Techniques for V.Fast
Authors: Eyuboglu M. Vedat , Forney G. David , Dong Ping , Long Guozhu
Published: September 2008

An overview is provided of the modulation techniques that are being considered for a new voiceband modem Recommendation, nicknamed V.fast. These techniques include adaptive bandwidth operation for automatically selecting the transmission band, multi‐dimensional trollis coded modulation for higher coding gain, constellation shaping for higher shaping gain, precoding and pre‐emphasis for advanced equalization, and warping for resistance against signal‐dependent impairments. Simulation results are presented to illustrate performance. By adaptively selecting an appropriate combination of these modulation techniques based on line conditions, V.fast modems are expected to double the maximum data rate of standard modems.
Decoding of M‐PSK‐Multilevel Codes
Authors: Woerz Thomas , Hagenauer Joachim
Published: September 2008

Multilevel codes give an impressive asymptotic coding gain measured in dB. However, when classical multistage decoding is used, this gain can only be partly realized at bit error rates (BER) around 10−5. It is shown how multistage decoding can be improved for this BER range. We use interleaving between the levels, pass reliability information between the different stages by applying “Soft‐Output” decoders, and apply re‐iterated decoding. In the latter case lower levels are again decoded using the results of the higher levels. It is shown for coded 8‐PSK that additional coding gains up to 2 dB are achieved by these means at the cost of modest complexity, but the decoding delay is increased.
Multi‐Level Block Coded Modulations with Unequal Error Protection for the Rayleigh Fading Channel
Authors: Seshadri Nambi , Sundberg Carl‐Erik W.
Published: September 2008

Block coded 8‐DPSK modulations are presented for the time selective Rayleigh fading channel. These coded modulations are based on multi‐level code constructions and utilize short binary block codes of length 2 to 8 (binary symbols) as building blocks to construct 8‐DPSK codes of length 2 to 8 symbols, respectively. All the constructed block coded modulations have a built in time diversity of at least 2 to combat Rayleigh fading. Unequal error protection (UEP) is obtained by providing higher time diversity for the important data. Further UEP can be obtained by using a non‐uniform signal constellation that provides higher product distance (through increased component Euclidean distance) for the more important data. Low transmission delay is obtained by matching the code rate and interleaver to the channel conditions (Doppler spread). Block coded 8‐DPSK schemes with rate 1.5‐2.25 information bits per symbol and code length 2 to 8 symbols have been designed and simulated for various values of Doppler spread. Gains of more than 15 dB can be obtained at a bit error rate of 10−3for a fraction of the data that is deemed to be most important. By using different binary codes in the multilevel scheme and by using different nonuniform signal constellations, the unequal error probability profile and the data rates can be controlled in a flexible manner.
Analysis of Erbium Doped Fiber Amplifiers by Combined Runge‐Kutta and Finite‐Element Methods
Authors: Pasquale Fabrizio Di , Gaibazzi Alberto , Zoboii Maurizio
Published: September 2008

Erbium‐doped fiber amplifiers are analyzed by solving numerically Maxwell equations and propagation‐rate equations of a homogeneous three‐level laser medium. A finite‐element code is used to account for the effect of spatial mode distributions and erbium concentration profile, while an iterative procedure, based on the Runge‐Kutta algorithm, allows to compute both gain and amplified spontaneous emission spectra. A comparison of the performance of 1480 and 980 nm pumped amplifiers is presented. The effect of different erbium concentration profiles on amplifier performance is also investigated.
Approximate Analysis of Buffered Multiple‐Access Protocols
Authors: Stamoulis George D. , Sykas Efstathios O. , Protonotarios Emmanuel N.
Published: September 2008

A method for the approximate performance analysis of random multiple‐access protocols, such as, ALOHA, URN, random TDMA, is presented. This method is an extension of a previously proposed 2‐Markov chain method. It is applicable to systems consisting of a Finite number of identical users, each having a buffer capacity of L packets, where L > 2. [For L = 2 the proposed method is exact]. The performance measures of the system under analysis are computed following the solution of a system of nonlinear equations, the size of which is independent of the buffer size L. The numerical results derived are in very good agreement with simulation.
A Model of a Rearrangeable User‐Network Interface in B‐ISDN
Authors: Filipiak Janusz
Published: September 2008

A new structure of the User‐Network Interface (UNI) for B‐ISDN is developed. The proposed UNI architecture allows for separation of transport, signalling, and network management functions. It provides a logically consistent framework for modelling of OSI, SS No. 7, DSS1, and Telecommunication Management Network protocols.
CAN Operated on an Optical Double Ring at Improved Fault‐Tolerance
Authors: Kuntz Walter , Mores Robert , Morse M. J.
Published: September 2008

The use of a fibre optic ring with a multiple access protocol designed to work on an electrical bus is investigated in this study. An algorithm is presented for interfacing the existing network controller with an optical double ring in such a way that the ring appears to be the equivalent of an electrical bus. The trade‐off between cost and performance for a double ring in this application is acceptable and the inherent redundancy in the topology gives good fault tolerance at the expense of an extra hardware and software in each network node.
Letter: A Simple Multilevel Block‐Coding Scheme with π/4‐QPSK Properties
Authors: Henkel Werner , Litzenburger Manfred
Published: September 2008

A multilevel block‐coded QPSK with a similar envelope and trajectories as π/4‐QPSK is proposed. Additionally, it is rotationally invariant and, thus, allows coherent detection. The asymptotic coding gain is 3 dB, whereas the effective coding gain at a bit‐error probability of 10−6 is around 2 dB against uncoded π/4‐QPSK. The corresponding trellis of a full maximum‐likelihood decoder has only four states, which results in a very low complexity.
On QAM Speech Transmission Schemes for Microcellular Mobile PCNs
Authors: Hanzo Lajos , Webb William , Steele Raymond , Salami Redwan A.
Published: September 2008

On the way towards third generation personal communication networks (PCN) the deployment of 16‐level quadrature amplitude modulation (QAM) schemes is investigated via flat microcellular Rayleigh‐fading mobile radio channels having mild co‐channel interference with and without diversity. Our proposed differentially coded non‐coherent 16‐QAM scheme requires no pilot symbol assistance, no automatic gain control (AGO and no carrier recovery. High speech quality associated with a mean opinion score of about four (MOS= 4.0) is ensured at a signalling rate of 6.2 kBd for channel signal to noise ratios (SNR) above 20 ‐ 25 dB and signal to interference ratios (SIR) above 25 ‐ 30 dB by the 13.4 kbit/s medium complexity regular pulse excited (RPE) speech codec, when carefully matched twin‐class low complexity binary Bose‐Chaudhuri‐Hocquenghem (BCH) error correction coding and 16‐QAM combined with second order diversity are deployed. The overall speech delay is about 40 ms and the user bandwidth is 9.3 kHz, which allows us to accommodate 21 users in a 200 kHz channel slot.
Letter: Impact of RFI Detection in DRS Links on the Performance of Coding Schemes
Authors: Losquadro Giacinto , Michel Philippe , Elia Michele , Visintin Monica
Published: September 2008

This paper deals with Data Relay Satellite systems operating in the S‐band environment and using Binary Phase Shift Keying modulation with concatenated Forward Error Correction data protection. One of the major sources of their performance degradation is radar generated Radio Frequency Interference in the same band. Transmission channel performance would certainly be improved if RFI positions (called erasures) were detected and passed to the decoders. By allowing the codes to handle about twice as many erasures as errors, this information would significantly reduce the effects of RFI deterioration.

A novel technique for RFI detection is developed. It is based on a bank of simple “moving windows” associated with a detection algorithm and a method for the removal of ambiguous RFI detections. The use of this erasure information in the Viterbi decoding process is then illustrated and a new rule for updating the decoding metric is proposed.

The residual correlation on the errors at the Viterbi decoder output makes the outer code useless, unless a further interleaving is introduced.

Extensive simulation results highlighting the good performance of the joint RFI detection and modified Viterbi decoding schemes are presented. Simulation is also used to assess the outer code behavior.
An Asymmetric Speech Coding Algorithm Using Vector Quantization and Silence Deletion
Authors: Koch Ronald C. N. , Prasad Ramjee , Bons Jan H.
Published: September 2008

In store‐and‐forward and multi‐media speech applications, e.g. in voice‐mail or when adding verbal comments to a document, the speech encoder can be allowed more time and higher complexity than in real‐time speech coding. Decoding however must be simple when a low‐cost terminal (e.g., a PC) is used. This kind of coding algorithm is called an asymmetric algorithm. Asymmetric algorithms exploit encoding delay to code the signal efficiently. An existing asymmetric coding algorithm is Vector Quantization (VQ). A new asymmetric algorithm is proposed, based on the coding of the time intervals between zero‐crossings (frames) using VQ and silence deletion. The algorithm takes advantage of the empirical fact that infinitely clipped speech retains its intelligibility. The algorithm has been implemented using software and its performance was evaluated.
Synchronous Digital Hierarchy Optical Metropolitan Network Ring Traffic Analysis
Authors: Owen Henry L. , Wulf‐Mathies Carston
Published: September 2008

As a result of the Synchronous Digital Hierarchy (SDH) standards, new network topologies are being introduced into existing networks. These new topologies include unidirectional and bidirectional rings in an environment which was previously dominated by point to point interconnections in meshed structures. Analysis of the traffic statistics of existing Plesiochronous Digital Hierarchy (PDH) metropolitan networks using various SDH network topologies is required in order to be able to determine optimal SDH network topologies. Existing bandwidth switching methodologies must be included in this analysis to determine the effects of these bandwidth routing methodologies. Several proposed hierarchical metropolitan optical transmission network architectures are examined in this paper in order to be able to determine strategies for the introduction of SDH capabilities into existing networks. An actual metropolitan network is used as a case study to evaluate traffic flow in several proposed hierarchical ring network topologies. These topologies include both unidirectional and bidirectional rings in three different hierarchical structures: a three level, a two level, and flat network hierarchies. The transmission requirements for these hierarchies with a central switching constraint are analyzed. The results indicate that existing centralized switching methodologies reduce the bandwidth carrying capacity advantage of bidirectional rings over unidirectional rings in hierarchical topologies.
Performance Evaluation of ASK Multichannel Coherent Optical Systems
Authors: Corvaja Roberto , Tomba Luciano
Published: September 2008

In this work we evaluate the impairments due to laser phase noise in multichannel coherent optical systems using a heterodyne ASK modulation scheme. The effects of crosstalk due to a finite value of the channel spacing are considered in a system employing a frequency division multiplexing technique. The phase noise and the frequency spacing between adjacent channels are the fundamental parameters which determine the design criteria (e.g. the bandwidth of the intermediate frequency filters) and the performance of the receiver. The accurate statistical characterization of the filtered phase noise and of the crosstalk is the key to get accurate results: to this aim the exact moments of the random processes related to the phase noise and to the crosstalk interference are used together with a Gaussian Quadrature Rule for the evaluation of the error probability.
Error‐Correction Coding for High‐Speed Optical Transmission Systems Based on the Synchronous Digital Hierarchy
Authors: Paxal V. , Jourdain P. , Karam G.
Published: September 2008

The quality objectives given in the CCITT recommendations concerning fiber optics transmission over the Synchronous Digital Hierarchy (SDH) network are difficult to achieve in high‐speed systems. Equipment imperfections often result in a Bit Error Rate (BER) floor above the recommended BER value of 1CH4. In this paper we propose a simple Reed Solomon (RS) coding scheme for the Synchronous Transport Module level‐1 (STM‐1) frame which leads to a substantial BER performance improvement over uncoded systems. The RS code proposed is a shortened one‐symbol‐correcting code. Experimental results obtained with a laboratory prototype are reported which show that this code reduces the BER floor by four orders of magnitude.