bluuebunny/crossref_metadata_2025_split huggingface dataset:
ATM block transfer capability vs. available bit rate service
Authors: Guillemin Fabrice 
Published: September 2008

AbstractATM Block Transfer is an ATM transfer capability, which has been standardized in the May 1996 version of ITU‐T Recommendation 1.371. Two transmission modes for ABT exist, namely the delayed and immediate transmission modes, giving rise to ABT/DT and ABT/IT, respectively, which can run in the elastic or rigid modes. The Available Bit Rate (ABR) service is an ATM layer service, which has been worked by the ATM Forum and specified in the UNI Spec. 4.0 voted in June 1996. The aim of this paper is to give the high level description of ABT and ABR and to draw attention to their common features and their differences. It turns out that the service offered by ABR is much more sophisticated but also more fragile than that offered by elastic ABT/DT. Since the implementation of ABR requires a deeper modification of the existing ATM switches and cross‐connects than elastic ABT/DT, an interworking scenario between these two capabilities, compatible with the cross‐connects used in the current ATM networks, is proposed.
Letter: Output slave clock short term stability on SDH equipment
Authors: Ricchiuti Vlttorio , Ciammaichella Pietro 
Published: September 2008

AbstractIn the modern synchronous telecommunication networks the quality of distributed clock is of primary importance. Instabilities of slave clocks due to their internal noise sources introduce jitter on transported tributaries. Several parameters can be used to characterize the short term stability of a slave clock. In this paper we use the Time Deviation (TDEV (τ)) to characterize the short term stability of a slave clock based on Phase Locked Loop (PLL), locked to an ideal input reference signal. Different PLL bandwidth values are considered and the possibility to discriminate between the PLL internal noise types is also emphasized, analysing its output TDEV (τ) curves only.
Letter: Impact of double cavity FP demultiplexers on the performance of WDM dispersion supported transmission
Authors: Freire Mário M. , De Carvalho José A. R. Pacheco , De Carvalho Álvaro M. F. , Da Silva Henrique J. A. 
Published: September 2008

AbstractThis paper discusses the impact of double cavity Fabry‐Perot demultiplexers on the performance of wavelength division multiplexing (WDM) systems with dispersion supported transmission (DST) of three 10 Gbit/s channels separated 1 nm. For performance assessment, a suitable simulation methodology has been used which combines signal simulation with noise analysis in optically amplified multichannel direct detection systems. Simulation results show an improved system performance if a double cavity Fabry‐Perot filter is used as demultiplexer, resulting in WDM transmission with a crosstalk penalty less than 1 dB in the region of small linear increase of dispersion penalty of the DST method. The robustness of the multichannel DST method against data pattern dependencies is investigated.
Letter: Frame alignment design for HF receivers
Authors: Fina Silvia De , Lombardo Filippo Maria 
Published: September 2008

AbstractIn this letter the feasibility of the application of a frame alignment system based on a CFAR detection scheme over HF radio channels is investigated. The system performance is analyzed in terms of average holding time, average time for the detection of synchronization loss and average synchronization recovery time. The interdependence among the various parameters of the frame alignment scheme is investigated on a simulation basis.
SMATV networks ready for the introduction of digital TV
Authors: Seseña Julian , Prieto Héctor , Molina Ana 
Published: September 2008

AbstractThis paper describes the architectures for the reception of Digital TV in SMATV systems as well as the RF performance of the typical SMATV channel. Based on theoretical analysis, simulation and measurements campaigns performed within the DIGISMATV RACE Project, this paper presents the Reference Channel Model of SMATV systems which characterises the channel behaviour as the typical echoes performance in the coaxial distribution network. This network characterisation has been a key tool for designing and testing equalisers to be used in the QAM IRD's intended for SMATV. The interactive possibilities of SMATV systems using low cost satellite terminals are also addressed in this paper. Thanks to the achievements of the DIGISMATV RACE project it can be concluded that SMATV networks are compatible and ready for the new era of digital TV.
Security analysis of the message authenticator algorithm (MAA)
Authors: Preneel Bart , Rumen Vincent , Van Oorschot Paul C. 
Published: September 2008

AbstractThe security of the ISO banking standard Message Authenticator Algorithm (ISO 8731‐2), also known as MAA, is considered. The attacks presented herein, which exploit the internal structure of the algorithm, are the first computationally feasible attacks on MAA. First a MAC forgery attack is presented that requires 217 messages of 256 kbytes or 224 messages of 1 kbyte; the latter circumvents the special MAA mode for long messages defined in the standard. Next a key recovery attack on MAA is described which requires 232 chosen texts consisting of a single message block. The number of off‐line multiplications for this attack varies between 244 for one key in 1000 to about 251 for one key in 50. This should be compared to about 3 265multiplications for an exhaustive key search. Finally it is shown that MAA has 233 keys for which it is rather easy to create a large cluster of collisions. These keys can be detected and recovered with 227 chosen texts. From these attacks follows me identification of several classes of weak keys for MAA.
Managing trust in an information‐labeling system
Authors: Blaze Matt , Feigenbaum Joan , Resnick Paul , Strauss Martin 
Published: September 2008

AbstractMany network services need to make “trust management” decisions; in particular, processing users' requests for action often requires using labels and credentials that may not be authentic or trustworthy. In this paper, we address the problem of trust management in information labeling. The Platform for Internet Content Selection (PICS), proposed by Resnick and Miller [13], establishes a flexible way to label documents according to various aspects of their contents, thus permitting a large and diverse group of potential viewers to make (automated) informed judgments about whether or not to view them. For some viewers, the relevant aspects may be quantity or quality of material in certain topical areas, and, for others, they may be the presence or absence of potentially offensive language or images. Thus PICS users need a language in which to specify their PICS profiles, i.e., the aspects according to which they want documents to be labeled, the acceptable values of those labels, and the parties whom they trust to do the labeling. Furthermore, PICS‐compliant client software (e.g., a web browser) needs a mechanism for checking whether a document meets the requirements set forth in a viewer's profile. A trust management solution for the PICS information‐labeling system must provide both a language for specifying profiles and a mechanism for checking whether a document meets the requirements given in a profile. This paper describes our design and implementation of a PICS profile language and our experience integrating the Policy Maker trust management engine with a PICS‐compliant browser to provide a checking mechanism. Policy Maker was originally designed to address trust management problems in network services that process signed requests for action and use public‐key cryptography [2]. Because information labeling is not inherently a cryptographically based service and thus is outside the original scope of the Policy Maker framework, our work on information labeling is evidence of Policy Maker's power and adaptability.
A mesh‐interpolation scheme for very‐low bitrate coding of video sequences
Authors: De Natale Francesco G. B. , Giusto Daniele D. 
Published: September 2008

AbstractA very‐low bitrate video codec is proposed that processes an image sequence as a two‐component information source. The main difference from state‐of‐the‐art approaches lies in the use of a 3D spatio‐temporal interpolation; it is based on a non‐uniform sampling where frames are processed as 3D blocks, so achieving an adaptive allocation for the information to be transmitted. Residuals are then compressed through a transform coder. Such a method allows for a concurrent and efficient exploitation of intra‐ and inter‐frame correlations; experimental results show a good fidelity in decoded sequences, both in terms of subjective and objective quality.
Adaptive identification and equalization of magnetic recording channels
Authors: Tahir Özden M. , Kayran Ahmet H. , Panayirci Erdal 
Published: September 2008

AbstractA new RLS adaptive Volterra filter is presented. The nonlinear filtering problem is transformed into an equivalent multichannel, but linear, filtering problem. The multichannel input signal is completely orthogonalized using sequential processing multichannel lattice stages. Thus, a fast convergent, highly modular and, simple filter with good numerical properties is designed. In the identification of magnetic recording channels, the filter identifies the channels directly and parameters for the channel nonlinearity are quantified simultaneously. In the equalization of magnetic channels, the most effective equalizer length can be assigned dynamically.
On recursive optimal detection of linear modulations in the presence of random fading
Authors: Castoldi Piero , Raheli Riccardo 
Published: September 2008

AbstractIn this paper, the problem of optimal detection of a linearly modulated digital signal transmitted over a fading channel is addressed. First, the issue of preliminary front‐end processing in order to extract a sufficient statistics for information sequence detection from the continuous‐time received signal is considered. Then, recursive algorithms are derived, which approximate optimal detection under the assumption of a linear and noisy channel modeled by a stochastic time‐varying impulse response with arbitrary known statistics. Specific solutions are proposed for the Rayleigh fading channel typical of mobile radio communications. The information symbols are assumed to be grouped into blocks which are preceded and followed by known preamble and postamble, respectively This model encompasses both Time Division Multiple Access (TDMA) schemes and pilot symbol assisted transmission. Two detection schemes are considered and relevant recursive formulations proposed. More specifically, optimal detection in complete absence of Channel State Information (CSI) (blind detection) or in presence of perfect CSI at the beginning of the data block (trained detection) are investigated. It is shown that optimal detection performance may be practically attained by sampling the received signal with few samples per symbol interval and searching a trellis diagram of adequate size by means of a Viterbi algorithm. State‐complexity reduction techniques based on Per‐Survivor Processing (PSP) for both types of detection schemes are also considered.
Eavesdropper performance in cellular CDMA
Authors: McKellips Andrew , Verdú Sergio 
Published: September 2008

AbstractWe study eavesdropper performance in power‐controlled cellular CDMA systems. A significant hindrance to eavesdropping in the reverse channel is the wide range of potential received powers from active users; although power control insures that all users are received with approximately equal power at the base station, it does not concern itself with the rest of the cell. Susceptibility to the near‐far problem is demonstrated, and performance sensitivity to eavesdropper location is shown to depend on a single off‐centered‐ness parameter. Both circular and linear cell geometries are considered, with log‐distance and log‐normal shadowing models adopted for signal path loss. A comparison of several eavesdropper detection strategies is performed, demonstrating a potential for significant performance improvement through the use of multiuser detection techniques.
Letter fade countermeasures and adaptive resource sharing for an experimental TDMA satellite communications system operating at Ka‐band
Authors: Schnell Michael , Hugo Dirk Von 
Published: September 2008

AbstractSatellite communications systems operating at Ka‐band suffer from severe rain fading. Thus, in order to achieve an acceptable availability fade countermeasures have to be applied which are efficiently implemented using adaptive resource sharing. In this letter, the results from a measurement campaign during which an experimental time‐division multiple‐access satellite communications system applying fade countermeasures has been operated at Ka‐band are reported and discussed. The results show that fade countermeasures can be used efficiently leading to a considerable improvement in performance and/or availability.
Letter on the integral frequency‐domain/time‐domain relationship of MTIE (τ, β)
Authors: Tavella Patrizia 
Published: September 2008

AbstractThe range spanned by a clock time error is a random quantity that can be statistically characterised. The paper considers the case of clock affected by white phase noise and the range probability laws are inferred. From the probability distribution, the percentile Maximum Time Interval Error, MTIE(τ, β), can be estimated and the relationship between frequency domain and time domain are discussed.
Estimating Cell Transfer Delay and Cell Delay Variation in ATM Networks: Measurement Techniques and Results
Authors: Roppel Carsten 
Published: September 2008

AbstractPerformance parameters of the ATM layer related to delay are the cell transfer delay (CTD) and cell delay variation (CDV). Monitoring CTD and CDV is important for the operator of an ATM network, in order to guarantee the quality of service expected by the user. This paper discusses basic properties of CTD and CDV, the latter one being defined in terms of 2‐‐point CDV and 1‐‐point CDV. It outlines fundamental measurement techniques and methods for estimating CTD and 2‐‐point CDV, which do not rely on the availability of synchronized clocks at the measurement points. Finally, measurement results obtained from the ATM network operated by Deutsche Telekom are presented.
Shaping Aggregate LAN Flows for Transmission over ABR Connections
Authors: Pippas John B. , Venieris Iakovos S. , Sancjez‐P Jorge‐A. 
Published: September 2008

AbstractIn the current recommendations on Internetworking over Non Broadcasting Medium Access and Multi‐Protocol Over ATM, the issues of ATM bandwidth allocation and flow control for best effort external LAN flows, forwarded to ATM connections, have not been adequately addressed. In this paper, we integrate the above features in the Access Units (i.e., bridges and routers) to smooth the bursty aggregate LAN traffic, to minimize losses due to congestion and consequently to achieve high end‐to‐end performance. The proposed flow control mechanism is based on the knowledge of the bandwidth available in the backbone network. Bandwidth advertising and explicit congestion notification mechanisms are provided by several network technologies such as Frame Relay and ATM. In the latter case the corresponding transfer capability is the Available Bit Rate (ABR). The proposed flow control mechanism, counts the frame delay in the Access Unit, and sends explicit feedback (backpressure) to neighboring legacy LAN sources. Explicit feedback partially absorbs the self‐similar features of the LAN traffic and can extend the ABR flow control to the non‐ATM legacy LAN stations. The shaping performed by the AU can be considered independent to the specific bandwidth advertising mechanism of the backbone network; in our case the ABR. In the performance results, the mechanism is shown to be efficient and adaptive to changes in the ATM available bandwidth and to a variety of LAN traffic characteristics. It is also shown that the flow control mechanism can be easily integrated in the protocol stacks currently met by today's LANs.
Letter Modified Three‐Level Code Acquisition Scheme for Frequency Hopping Radio in Channels with Fading
Authors: Todorovic Branislav , Sunjevaric Milan , Lepir Dragan 
Published: September 2008

AbstractModified three‐level code acquisition scheme for frequency hopping (FH) signals, suitable for operation in a fading environment, is presented and analyzed in this letter. This scheme uses a set of passive correlators, a message demodulator and a bank of active correlators. The multiple sync prefixes reduce the probability of missing the signal in a fading environment. The effects of two the most important acquisition parameters (number of passive correlators and number of active correlators) on acquisition performances are analyzed.
Holding Time of a Frame Alignment System Operating Over Time Variant Channels
Authors: De Fina Silvia , Lombardo Filippo Maria 
Published: September 2008

AbstractIn this work, a complete analysis of the average holding time in a frame alignment system operating over time variant channels is developed. In these cases the probability of miss is time variant as well, so that the statistics of the underlying process has to be investigated for properly approaching the system design. In a common frame synchronization strategy, involving a certain number α‐1 of pre‐alarm states, the probability of miss has to be calculated for α consecutive frames so that any time correlation in the propagation conditions has to be properly reflected in the statistical model of the miss process. The derived expression of the average holding time can be used for designing the alignment strategy for any time variant medium, under the sole hypothesis that the probability of miss can be fully characterized by its second order statistic and that it can be assumed to hold constant for the preamble duration. Sensitivity results for a sample application in a typical system operating in the HF band are also given: the dependence of the average holding time from some parameters related to frequency selectivity (the delay spread) and time selectivity (the frequency spread s) of the propagation medium can be clearly envisaged.
Multi‐Period Planning of Survivable WDM Networks
Authors: Pickavet Mario , Demeester Piet 
Published: September 2008

AbstractThis paper presents a new heuristic algorithm useful for long‐term planning of survivable WDM networks. A multi‐period model is formulated that combines network topology design and capacity expansion. The ability to determine network expansion schedules of this type becomes increasingly important to the telecommunications industry and to its customers. The solution technique consists of a Genetic Algorithm that allows to generate several network alternatives for each time period simultaneously and shortest‐path techniques to deduce from these alternatives a least‐cost network expansion plan over all time periods. The multi‐period planning approach is illustrated on a realistic network example. Extensive simulations on a wide range of problem instances are carried out to assess the cost savings that can be expected by choosing a multi‐period planning approach instead of an iterative network expansion design method.
PCS Subscribers Mobility Modeling Using Fractional Brownian Motion (FBM)
Authors: Aleman‐Llanes Enrique , Munoz‐Rodriguez David , Molina Carlos 
Published: September 2008

AbstractThe growth of PCS systems demands better resource management algorithms. Reduction of the cell size has been a common point that many solutions propose. As a result of cell reduction, the importance of finer mobility descriptions increases, such that it is necessary to look for improved analytical tools to model mobility. In this paper, a mobility model based on Fractional Brownian Motion (FBM) is presented. The proposed model represents a wide variety of mobility scenarios, removing the unrealistic constraints of previous models. The suitability and flexibility of the proposed methodology is discussed through the analysis of different scenarios.
Convolutional Encoders to Minimize Bit‐Error‐Rate
Authors: Lapidoth Amos , Sallaway Peter J. 
Published: September 2008

AbstractThe results of a computer search for convolutional encoders for the binary symmetric channel and the additive white Gaussian noise channel are reported. Both feed‐forward and feedback encoders are considered. It is shown that, when bit error rate is the design criterion. feedback encoders may outperform the best feed‐forward encoders at no additional complexity.
Fundamental Properties of the Low Voltage Power Distribution Grid Used as a Data Channel
Authors: Dostert Klaus , Zimmermann Manfred , Waldeck Torsten , Arzberger Michael 
Published: September 2008

AbstractRecently a steadily increasing interest towards usink the low voltage power distribution grid for various communication purposes is noticed. For the construction of appropriate equipment, being able to cope with the properties of such an unusual channel, a thorough understanding of physics is paramount. The work presented in the following describes essential contributions towards modelling basic properties of low voltage energy distribution networks as data channels. New and important measurement results of parameters significantly influencing the performance of communication systems are outlined. covering typical values and properties of network access impedance, propagation characteristics as well as different kinds of interference in the frequency range 20kHz to 150kHz. Furthermore channel model approaches based on the results are discussed.
Design of a Multistage Optical Packet Switch
Authors: Raffaelli Carla 
Published: September 2008

AbstractOptical packet switching is considered as a means to achieve high speed networking in future optical multi‐service networks, Optical switches of limited size are feasible with present‐day photonic technology, so solutions for the design and implementation of large switches are proposed here. They are based on a multistage architecture built using small switching modules with output queuing, organised according to a Clos topology. Many degrees of freedom are available for switch design and they are exploited to achieve performance optimisation in relation to packet loss. Simulation and analytical tools are developed to evaluate switch architecture performance. Results and application examples are given to show the feasibility of the multistage architecture for optical networking.
Stochastic channel allocation in non—linear environments
Authors: Baruffa Giuseppe , Cacopardi Saverio , Frescura Fabrizio , Reali Gianluca 
Published: September 2008

AbstractIn this paper new techniques able to solve the problem of frequency assignment in satellite communications are proposed. Their performance is evaluated in a non—linear environment that models the satellite channel behaviour. The stochastic approach consists in the exploration and validation of new load configurations for the downlink channel. Since the carriers have different powers, the complexity of the problem is high. An analytical approach is used for calculating the number and the power of 3rd order inter—modulation products, which may also be used for higher order contributions. After this, comparisons between classic and stochastic techniques, in terms of computational time and allocation quality, are shown.