bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polarimetric signal processing of meteorological target observations with the DLR weather radar
Authors: Schroth Arno , Tragi Karl , Lüneburg Ernst , Chandra Madhukar 
Published: September 2008

AbstractAt 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

AbstractLaurent'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

AbstractAn 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

AbstractArray 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

AbstractA 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

AbstractThe 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

AbstractThis 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

AbstractTunable 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

AbstractThis 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

AbstractThis 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

AbstractSource 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

AbstractThis 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

AbstractOn‐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.
Aggregation of Systems with HDLC Protocol
Authors: Sczittnick Michael , Uhl Tadeusz 
Published: September 2008

AbstractThe 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

AbstractWe 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

AbstractA 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

AbstractWe 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

AbstractIn 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

AbstractA 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

AbstractIn 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

AbstractAn 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

AbstractMultilevel 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

AbstractBlock 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

AbstractErbium‐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

AbstractA 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

AbstractA 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

AbstractThe 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.