bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wireless infrared factory network for hand‐held terminals
Authors: Roviras Daniel , Lescure Marc , Bensalah Rachid , Bosch Tthierry 
Published: September 2008

AbstractAn experimental wireless infrared network with ISDN compatibility is described. This factory network has been studied in a European project: “FCPN” (Factory Customer Premises Network). The architecture of the network is a cellular one. Infrared cells are connected together by a high‐speed optical fiber backbone. Hand‐held terminals communicate via an infrared (IR) channel based on a diffusion technique. The communication protocol on the infrared channel is based on the ISDN protocol with standard ISDN rate (2 x 64 kbits/s + 16 kbits/s)r Measurements of diffusion properties of standard construction materials are presented. These properties are in good agreement with the requirements of an indoor IR diffuse transmission. Architectural choices for the IR transceiver are discussed with special emphasis on consumption reduction for mobile‐terminals autonomy improvement. Key elements of the IR transceiver implementation are described. Experimental results for an IR diffuse channel are presented, showing the suitability of such a transmission technique for indoor hand‐held terminals. Performances of the system are described in term of Bit Error Rate measurements.
Fast texture segmentation for object‐oriented video coding
Authors: Lavagetto Fabio , Cocurullo Fabio 
Published: September 2008

AbstractObject‐oriented approaches to still and moving picture coding, thanks to the extensive use of efficient algorithms for image segmentation and region coding, are expected to improve significantly the rate‐distortion performances of conventional block‐based methodologies. Recent results show that most of the chances to win this challenge depend on the efficiency in image segmentation: the precise aim of our investigation and the purpose of this paper is just to show the concrete possibility of employing fast adaptive algorithms for segmenting images and video frames and allowing high quality coding with very high compression. The segmentation algorithm we propose relies on the recursive computation of the Spatial Gray Level Dependence Matrix (SGLDM) and on a fast adaptive procedure for the statistics evaluation. Subsequent clustering of the image pixels in the 5‐dimensional statistical‐spatial space MVCXY, composed of local mean (M), local variance (V), local correlation (C) and spatial coordinates (XY) is encharged of providing final image segmentation. Target applications for videophone coding of color sequences at very low bitrate are foreseen.
Lossless hierarchical storage of images
Authors: Piscaglia Patrik , Macq Benoit 
Published: September 2008

AbstractNowadays, more and more images from every area need to be stored. If a lossless compression of the image is desired, the storage space requirements can still be enormous. The aim of this paper is to show how to store those images in such a way that a quick access AND a big storage capacity are available together. The tools used are a multi‐resolution entropy coding (the Haar transform and the Universal Variable Length Coder) combined with a hierarchical quantization (the slicing) of each resolution. The main idea is to have a small icon stored on a fast access media, instantly accessible, while the high resolution components are stored on mass media and are loaded only if needed. The total compression is lossless.
Combination of simple vision modules for robust real‐time motion tracking
Authors: Denzier Joachim , Niemann Heinrich 
Published: September 2008

AbstractIn this paper we describe a real time object tracking system consisting of three modules (motion detection, object tracking, robot control), each working with a moderate accuracy, implemented in parallel on a workstation cluster, and therefore operating fast without any specialized hardware. The robustness and quality of the system is achieved by a combination of these vision modules with an additional attention module which recognizes errors during the tracking. For object tracking in image sequences we apply the method of active contour models (snakes) which can be used for contour description and extraction as well. We show how the snake is initialized automatically by the motion detection module, explain the tracking module, and demonstrate the detection of errors during the tracking by the attention module. Experiments show that this approach allows a robust real‐time object tracking over long image sequences. Using a formal error measurement presented in this paper it will be shown that the moving object is in the center of the image in 90 percent of all images.
A new suboptimum viterbi receiver structure for digital communication systems
Authors: Behm Wolfgang , Fliege Norbert J. 
Published: September 2008

AbstractMinimization of the average symbol error probability is the central aim when designing a receiver structure of a digital communication system. It is well known that the maximum‐likelihood (ML) decision rule yields the best solution in this sense. In practical applications, the ML sequence estimation is realized by the computationally efficient Viterbi algorithm. As a drawback, however, the computational complexity of this algorithm depends exponentially on the length of the channel impulse response. In this paper, a new suboptimum receiver structure is presented containing a linear recursive equalizer for channel memory truncation and a Viterbi detector. The criterion for adjusting the equalizer and the remaining impulse response for the Viterbi detector is derived from the zeros of the channel transfer function. The proposed concept takes control of both the noise enhancement by the equalizer and the computational complexity of the Viterbi algorithm.
On the error burst properties of the “standard” K = 7, rate‐1/2 convolutional code with soft‐decision viterbi decoding
Authors: Franchi Antonio , Harris Robert A. 
Published: September 2008

AbstractThe error burst properties of the “standard” rate‐1/2, K = 7, convolutional code (generators 133,171) with soft‐decision Viterbi decoding are studied. The average burst length is determined by computer simulation as a function of Eb/N0. At low Eb/N0 it is shown to depend strongly on the criterion used to define a burst. The distribution of burst lengths is well modelled by a geometric distribution which depends only on the average burst length. At high Eb/No, the distribution is that of the code words at the minimum Hamming distance from any given code word. A simple heuristic model, valid at low Eb/Na, is developed for predicting the average number of errors in an error event of given length. This is validated by computer simulation. At high Eb/N0 the distribution is also determined by that of the minimum distance code words. For both models there is a smooth transition between the two extremes. The simple, low Eb/N0, models are combined to derive an estimate for the average error‐density for all bursts. Although neither model individually is a good fit at high Eb/N0, the composite model agrees well with computer simulations at all values of Eb/N0. This paper also serves to gather material from a number of widely spread sources into a single place, providing a coherent treatment. A number of useful empirical relationships are derived from the simulation results.
Capacity assignment for circuit‐switched reference networks with nonhierarchical routing
Authors: Hartmann Harro L. , He Hucang 
Published: September 2008

AbstractCapacity assignment (CA) implies the minimization of network cost subject to several constraints, such as traffic demands, end‐to‐end Grade of Services (GOS) and the non negativity conservation of flows. Real asymmetric networks may be described by several statistical moments of different orders. Thus a reference network may be characterized by the mean distance between a given set of fully intermeshed nodes, the mean traffic offered per demand pair, and the mean GOS for all end‐to‐end blockings. At first, we present an exact theoretical solution of the CA‐problem for symmetric circuit‐ switched networks. We start with the formulation of the end‐to‐end blockinges with nonhierarchical two‐link path alternate routing for reversible and nonreversible scheme, respectively. Next, we derive the Kuhn‐Tucker conditions for the CA‐problem. The corresponding solution is verified to be unique and stable. Then, we proceed to approximate the relevant optimal parameters, such as the economic high link blocking, the optimal size of routing sequences and the minimum link size, by using least‐square fitting. The results form new rules of thumb for a wide range of traffic demand and GOS and may thus be used to support the initial dimensioning of asymmetric nonhierarchical networks. Finally an approximation for asymmetric networks is proposed and verified, which is based on an appropriate CA decomposition and relevant traffic parameters of both the symmetric reference and its asymmetric extension.
Codes and iterative decoding on general graphs
Authors: Wiberg Niclas , Loeliger Hans‐Andrea , Kotter Ralf 
Published: September 2008

AbstractA general framework, based on ideas of Tanner, for the description of codes and iterative decoding (“turbo coding”) is developed. Just like trellis‐based code descriptions are naturally matched to Viterbi decoding, code descriptions based on Tanner graphs (which may be viewed as generalized trellises) are naturally matched to iterative decoding. Two basic iterative decoding algorithms (which are versions of the algorithms of Berrou et al. and of Hagenauer, respectively) are shown to be natural generalizations of the forward‐backward algorithm (Bahl et al.) and the Viterbi algorithm, respectively, to arbitrary Tanner graphs. The careful derivation of these algorithms clarifies, in particular, which a priori probabilities are admissible and how they are properly dealt with. For cycle codes (a class of binary linear block codes), a complete characterization is given of the error patterns that are corrected by the generalized Viterbi algorithm after infinitely many iterations.
Separable concatenated convolutional codes: The structure and properties of a class of codes for iterative decoding
Authors: Lodge John H. , Young Richard J. , Guinand Paul S. 
Published: September 2008

AbstractIn this paper a brief overview of the concept of iterative processing is provided. Then a code construction for convolutional codes, that results in a signal structure amenable to iterative processing, is studied. This construction is analogous to product coding for block codes. It is shown that the construction shares a number of properties with die product coding construction, including the property that it is “commutative”. The relationship between the free distance and the interleaving factors is examined, and then exemplified with computer simulation results.
Weight distributions and bounds for turbo‐codes
Authors: Svirid Yuri V. 
Published: September 2008

AbstractAn optimal interleaving between two component encoders of a turbo‐code is proposed. The optimally criterion for any real constructable interleaver is given. For component codes with known weight distribution (WD), the WD of the turbo‐code with optimal interleaving is calculated. Furthermore, a method for approximate calculation of the WD of convolutional code with terminated feed‐forward and feed‐back encoders is proposed. Using this WD's and proposed interleaving, the union upper bounds on the bit error rate of the turbo‐code are given. It is shown that the often observed “break” in the performance curves of turbo‐codes is a result of their “broken” WD. For component codes lying on the Gilbert‐Varshamov bound, an upper bound on the ratio between the minimum distance of the turbo‐code and the component code is determined. The lower bounds on the signal‐to‐noise ratio needed to achieve error free decoding of turbo‐codes with random component coders are given. These bounds are compared with the Shannon limit and analogous bounds for random codes.
Effect of transmitter filter on the performance of FSK‐DPD and DPSK‐DPD in satellite mobile channel
Authors: Korn Israel 
Published: September 2008

AbstractWe study the effect of bandlimiting transmitter filter on the bit error probability (BEP) of M‐ary Frequency Shift Keying and Differential Phase Shift Keying with Differential Phase Detector in Satellite Mobile Channel. Numerical results are presented in the case when the transmitter and receiver filters are Butterworth filters of order NT = 4 and NR = 3 respectively. The BEP is reduced with increasing transmitter bandwidth with a minimum at infinite bandwidth, i.e. no transmitter filter. However finite values of this bandwidth can be used without significantly increasing the BEP. In the computation of the BEP we optimised various parameters, like the receiver bandwidth, sampling time, modulation index (for FSK only) and decision level.
Generalized cut‐off rate of DPSK noisy‐phase channels
Authors: Dallal Yeheskel E. , Shamai Shlomo 
Published: September 2008

AbstractCoded communication is examined for binary differential phase shift keying (DPSK) modulation where the communication channel consists of both a Brownian Motion phase noise and an additive white Gaussian noise (AWGN). Decoding utilizes a mismatched soft‐decision metric that accounts for the prefiltering of the phase‐noise‐impaired signals followed by differential demodulation. Binary Multiplexing of the equivalent channel results in a binary‐input, output‐symmetric, discrete‐time, coding channel, which is both stationary and memoryless. This multiplexing accounts as well for an underlying time‐diversity (repetition codes), providing an effective, yet simple, means of boosting the capabilities of less powerful codes to cope with high phase‐noise levels. The cut‐off rate of the considered channel is analytically too complicated to compute. The approach taken yields a coding channel characterization that further generalizes the concept of the generalized cut‐off rate for mismatched metrics to account as well for incomplete statistical characterization. The theoretical implication of this criterion for coded communication is examined. The Brownian Motion phase model is characterized by a finite set of the univariate moments admitted by certain exponential functional of the phase sample path, whose exact statistics seem intractable.
The effect of non‐ideal interpolation on symbol synchronizer performance
Authors: Bucket Katrien , Moeneclaey Marc 
Published: September 2008

AbstractThis contribution deals with the symbol synchronizer performance of a fully digitally implemented receiver, operating on a narrowband M‐PSK signal (one‐sided bandwidth not exceeding the symbol rate). The considered digital receiver operates on samples of the complex enveloper(t)of the received signal, taken by afixedclock which isnot synchronizedto the transmitter clock. The synchronized samples required for the symbol synchronization algorithm are computed byinterpolatingbetween the available non‐synchronized samples. Because of finite memory, interpolation is non‐ideal; hence, some amount of distortion is introduced, which affects the performance of the symbol synchronizer. By means oftheoretical analysis, we investigate the tracking performance of a specific decision‐directed feedback synchronizer, assuming interpolation of orders zero, one and two. We show that non‐ideal interpolation gives rise to a loop noise spectrum containing spectral lines, that mainly occur near/= 0 when the number of samples per symbol is close to an integer. Unless a sufficiently small loop bandwidth is chosen, the contribution of these spectral lines could dominate the timing error variance, which then becomes much larger than for synchronized sampling.
Multilevel differential modulation techniques (64‐DAPSK) for multicarrier transmission systems
Authors: Engels Volker , Rohling Hermann 
Published: September 2008

AbstractIn Digital Video Broadcasting (DVB) applications the objective is to transmit a high data rate of 34.368 Mbit/s in a single channel. For terrestrial digital transmission the considered radio channel bandwidth is 7 or 8 MHz. In this paper we analyse the performance of a multicarrier transmission technique, the well‐known Orthogonal Frequency Division Multiplexing (OFDM) method, and consider the system parameters for this DVB application. For the OFDM transmission technique an absolute modulation scheme (64‐QAM) has been suggested. In this case and in frequency‐selective interference situations a channel estimation process and a channel equalization are necessary [4], The equalization process can be realized by a multiplier bank at the FFT output in the receiver, a so‐called frequency‐domain equalizer. Alternatively, a multilevel differential modulation technique, the so‐called Differential Amplitude and Phase Shift Keying (64‐DAPSK) is proposed in this paper, in which the phase and the amplitude are used simultaneously for differential modulation. A differential modulation technique does not require any explicit knowledge about the radio channel properties in the differential channel equalization process. In an OFDM/64‐DAPSK receiver it is therefore not necessary to implement a frequency‐domain equalizer, which reduces the computation complexity. The performance of both modulation techniques has been analysed in the uncoded case referring to Gaussian and frequency‐selective Rayleigh fading channels. The results are described in this paper.
256‐state trellis code with 12‐D rectangular constellation using an extended wei method
Authors: Sterian Corneliu‐Eugen D. 
Published: September 2008

AbstractThe Wei's method of constructing trellis codes with 2N‐D rectangular constellations is limited to N being an integer power of two. In the present letter to the editor, this limitation is removed and the example of a 256‐state, rate 4/5 linear trellis code with 12‐D rectangular signal set is given.
On information rates in fading channels with partial side information
Authors: Kaplan Gideon , Shamai Shlomo 
Published: September 2008

AbstractA coded antipodal communication system operating over a Rayieigh fading channel is considered. A partial Side Information (SI) scheme is addressed, where the receiver has an access to the sum of received faded energies over several consecutive symbols. The generalized cut‐off rate is examined both for the independent and for the correlated fading models, and conclusions regarding the usefulness of this particular SI scheme are drawn.
About optimum slave clock bandwidth on SDH equipment
Authors: Ciammaichella Pietro , Ricchiuti Vittorio 
Published: September 2008

AbstractIn order to improve reliability, the modern telecommunication systems require hardware redundancy. In particular, many SDH devices include two timing units, locked to the same reference signal, that can provide each one in its turn a synchronization signal to the transmission units. Any switch between the two timing units produces a phase step on the input of the slave' clock linked to the synchronization signal. In this paper, with reference to a slave clock model based on Phase Locked Loop (PLL) system, it is derived the optimum PLL bandwidth that produces a good output short term stability in terms of MRTIE compliant with SDH Recommendations.
Stability requirements of oscillators used for synchronization loops in communication systems
Authors: Welti Arnold L. , Bernhard Urs P. 
Published: September 2008

AbstractAn imperfect clock timing recovery in receivers of modern communication systems degrades the performance of synchronization loops and, hence, the overall system reliability and data transmission quality. In this paper, the phase‐locked loop (PLL) for the carrier recovery and the delay‐locked loop (DLL) for the clock timing recovery of the pseudonoise (PN) code in direct‐sequence spread‐spectrum systems are analyzed regarding the impacts of imperfect oscillators (including phase noise and a frequency offset between transmitter and receiver) and channel noise on the mean exit time. The optimal design considerations to achieve a maximum mean exit time for second‐order synchronization loops can be used to find the required oscillator stability,Le., the maximum tolerable frequency offset and oscillator phase noise.
N‐branch diversity reception of mary DPSK signals in slow and nonselective nakagami fading
Authors: Fedele Gennaro 
Published: September 2008

AbstractThe problem of diversity reception of M‐ary differential phase shift keying modulated, signals in the presence of additive white Gaussian noise and Nakagami‐distributed slow and non‐selective fading is addressed. N‐branch selection diversity and maximal ratio combiners are considered. The average symbol error rate is analytically evaluated in terms of integral expressions, which can be easily computed via numerical integration routines. Numerical results are presented that allow one to point out those operational situations where diversity systems can operate successfully to mitigate the degrading effects of short‐term fading.
Improved performance of fast acquisition PLL synthesizer withN‐stage cycle swallower
Authors: Saba Takahiko , Park Duk‐Kyu , Mori Shinsaku 
Published: September 2008

AbstractThe PLL frequency synthesizer with anN‐stage cycle swallower (NSCS) is one of the fastest frequency switching synthesizers. The synthesizer, however, requires many stages in theNSCSto obtain accurate output frequencies. In this paper, to obtain both more accurate output frequencies with a few stages and a higher speed acquisition time, we propose two methods for improvingNSCSswitching operation. First, by allowing theNSCSoutput frequency to be variable a large range of choices in the division ratios becomes available in theNSCS. The proposed synthesizer has the output frequency of deviation within 0.0003 ppm when the 3‐stage cycle swallower is employed. Second, by temporarily increasing the expected amount of the variation in the output frequency, the acquisition time of theNSCSsynthesizer can be improved. Experimental results confirm that the proposed technique results in a shortened acquisition time.
A deterministic method for the derivation of a discrete WSSUS multipath fading channel model
Authors: Pätzold Matthias , Killat Ulrich , Shi Yu , Laue Frank 
Published: September 2008

AbstractAbstract A suitable and often used stochastical model for the description of the fading behaviour of a time variant and frequency‐selective channel is the wide sense stationary uncorrelated scattering (WSSUS) model. Usually, the wide sense stationary process is assumed to be a zero mean Gaussian process. In such a case, the WSSUS model is completely determind by the so called scattering function. In order to approximate a desired scattering function of a WSSUS model by a simulation model, it is well known that Monte Carlo based methods cm be used for the computation of the simulation model parameters (discrete echo delays and discrete Doppler frequencies). In this paper, we present a new method, which results always in a better approximation of a prescribed scattering function of a WSSUS model than the Monte Carlo principle. We show that the statistical behaviour of the resulting fading channel model ‐ in particular the level‐crossing rate and the average duration of fades ‐ is not only independent of a random realization of the discrete echo delays and discrete Doppler frequencies, but is also extremely close to the statistical behaviour as it was to be expected from the theory.
Letter: Large families of polynomial phase sequences with low correlation
Authors: Luke Hans Dieter 
Published: September 2008

AbstractLarge families of ≈ pQ (p prime, Q = 2, 3, 4.,) polynomial phase sequences are presented. The p‐ary sequences are of length p. Their correlation magnitudes are upper bounded by ≈ Q √p. The families are suitable for application in asynchronous CDMA systems.