bluuebunny/crossref_metadata_2025_split huggingface dataset:
Letter: All digital spread spectrum modems for power line communications
Authors: Dostert Klaus M. 
Published: September 2008

AbstractThrough the use of band‐spreading techniques electrical power distribution networks become reliable and universal data links. For cost and performance reasons all digital solutions for the. construction of modems are paramount. The use of general purpose digital signal processors (DSP) is neither feasible nor cost‐effective. After a review of appropriate signalling schemes the key components for integration into an ASIC will be outlined. Within the transmitter section of the ASIC a programmable address counter together with a sample memory provides precise and fast signal synthesis. In the receiver section a fast front‐end is needed for correlation operations. Furthermore essential steps towards bit decision are performed. A typical ASIC, representing the heart of a power line modem, finally contains the following functional blocks: An 8 bit correlator with a minimum of four separate accumulators, a squarer with at least two additional accumulators forming the decision logic, and a programmable 10 bit address counter. VHDL‐based ASIC design was performed and fabrication took place in October 1994 within the EUROCHIP project. An ASIC incorporates 5250 gates with a power consumption below 50 mW. Modems have been built with different signalling schemes for data rates up to 2400 bits/s. Measurements revealed typical bit error rates below 10−‐6.
Measurement‐based flow control for ABR services in ATM networks
Authors: Ghani Nasir , Mark Jon W. 
Published: September 2008

AbstractA distributedexplicit‐rate (ER)capacity allocation algorithm for handlingavailable‐bit rate (ABR)services in ATM networks is described. The algorithm uses a measurement‐based approach to achieve max‐min bandwidth fairness and to provide priority service mechanisms for heterogeneous traffic, e.g.,constant‐bit rate (CBR), variable‐bit rate (VBR), ABR, etc. Explicit provisions are made for handlingminimum cell rate (MCR)guarantees forABRconnections and minimizing RM cell buffering delays at the network switches. It is also proposed that the sources measure their average rates to properly handle variability and to improve bandwidth utilization. An extensive simulation study for a number of network scenarios, which shows that the proposed scheme adapts well to network dynamics and converges to max‐min fairness, is presented.
Spectrum shaping for land mobile radio systems
Authors: Ramésh R. , Chennakeshu Sandeep , Hassan Amer A. , Anderson John B. 
Published: September 2008

AbstractSpectral efficiency for land mobile radio channels is primarily limited by adjacent channel interference. Conventional digital modulation schemes do not achieve current specifications for adjacent channel interference at high data rates. The adjacent channel interference can be mitigated by the intelligent choice of transmitter components such as the modulation scheme and the transmit filter. We present a trellis coded modulation (TCM) scheme that can provide high data rates and at the same time reduce adjacent channel interference. We present methods to choose an appropriate TCM scheme under constraints of Euclidean distance and peak‐to‐average power. We also present methods to optimize transmit filters to minimize adjacent channel interference under various constraints. Examples are provided to illustrate the gains that can be obtained.
The influence of signal quantization on the performance of digital receivers for CDMA radio networks
Authors: Gaudenzi Riccardo De , Giannetti Filippo , Luise Marco 
Published: September 2008

AbstractIn an all‐digital implementation of a data modem for Direct‐Sequence Spread Spectrum (DS/SS) Code‐Division Multiple Access (CDMA) systems, the in‐phase and quadrature components of the received signal are customarily digitized just after IF matched filtering and baseband conversion. To reduce the processing effort in the data demodulator, it is of interest to represent the signals in the digital domain with as little a number of bits as possible. On the other hand, coarse signal quantization (down to 2‐3 bits/sample) causes a non‐negligible performance degradation as far as the receiverBERis concerned. The aim of this paper is thus the investigation of the impact of signal quantization on theBERperformance of a DS/SS CDMA receiver in the presence of Gaussian noise and co‐channel interference. Based on a general theoretical analysis, a few multiple access strategies are taken into consideration, and the theoretical findings are also checked by computer simulation. For all those systems, a four‐bit ADC, yielding less than 0.5 dB signal‐to‐noise ratio degradation at aBER= 10−3appears to provide a good trade‐off between performance loss and demodulator complexity.
Viterbi detection for the double differential MPSK modulation
Authors: Papproth Eckhard , Kaleh Ghassan Kawas 
Published: September 2008

AbstractA double differential encoding technique for phase shift keying symbols and its detection using the Viterbi algorithm to counteract channel phase and frequency uncertainties are presented. After deriving the detector structure from a maximum‐likelihood sequence detection approach we examine its performance and complexity and compare it to those of conventional and block detection techniques. For moderate complexity we attain the performance of the conventional single differential detector.
MDPSK on frequency‐selective ricean channels with diversity and cochannel interference
Authors: Abu‐Dayya Adnan A. , Beaulieu Norman C. 
Published: September 2008

AbstractPrecise average bit error rate (BER) results forM‐ary differential phase shift keying (MDPSK) on slow frequency‐selective Ricean fading and microcellular cochannel interference channels are presented. The microcellular fading environment is modeled by a Ricean fading desired signal and Rayleigh fading interferers. Equal gain postdetection microdiversity combining to mitigate the effects of fading is investigated. Nyquist pulse shaping is used and differential detection is employed at the receiver. The performance of the Gaussian interference model is also assessed. In this model, the interference contribution is represented by a Gaussian noise whose mean and variance are equal to the mean and variance of die sum of the interfering signals. The accuracy of the Gaussian model is assessed by comparing itsBERperformance with preciseBERresults. The preciseBERresults are obtained by using a combination of analysis and simulation. The effects of the Ricean AT‐factor, the number of diversity branches,L, and the level of modulation,M, on the averageBERare investigated in detail.
Authenticated key‐exchange in a mobile radio network
Authors: Hwang Min‐Shiang , Lee Chii‐Hwa 
Published: September 2008

AbstractA new method is proposed in this study for implementation of secure digital mobile communication systems. Two requirements for the systems must be considered, i.e., privacy and authentication. Privacy ensures that an eavesdropper cannot intercept conversations between two parties. Authentication ensures that service is not obtained fraudulently in order to avoid charge for usage. Additionally, a new key distribution scheme is designed for practical implementation in a low‐cost and low‐power digital mobile communication system.
Robust sequential projection algorithm: Teletraffic applications
Authors: Ursini Edson Luiz , Yacoub Michel Daoud , Amaral Wanger Caradori Do , Girolami Alessandro 
Published: September 2008

AbstractAnn‐step ahead Robust Sequential Projection Algorithm ‐ Robust SPA ‐, used for traffic forecast as well as for long term network planning is proposed. The algorithm uses the State Space Model with the state transition matrix being estimated by a relaxation technique. This lightly increases its complexity, as compared to a similar algorithm proposed in the literature, but renders the Robust SPA a better performance. The algorithm is also compared with the Expectation‐Maximization technique and, in general, the Robust SPA yields a slightly poorer performance as far as the mean square error between projected and observed data is concerned. On the other hand, it is more robust and requires far less computational effort. Moreover, due to its simplicity, an automated version of the algorithm can be easily implemented for applications in which a great deal of data is to be forecasted.
Heuristic algorithms for reliable multiplexed network design
Authors: Costamagna Eugenio , Fanni Alessandra 
Published: September 2008

AbstractA heuristic optimization algorithm is presented for topological optimization of wideband communication networks whose structure is based on a single central office and on a number of multiplexing centres. The reliability problem is discussed in detail introducing in the objective function a cost term related to the probability of failures. Optimization is performed in two steps. In the first step a tree non redundant network is determined, providing the starting configuration for the second step, in which redundant edges are introduced. Cross‐connect devices replace multiplexers when suitable, and a very general mesh topology is created. Statistics on a large number of test networks are reported. Network costs and reliability performances are deeply investigated.
On the use of dispersity routing for fault tolerant realtime channels
Authors: Banerjea Anindo 
Published: September 2008

AbstractThis paper presents a taxonomy of dispersity routing schemes designed to provide fault‐tolerant realtime communication. Our model involves the provision of dispersity at the application level, rather than in the physical layer as in traditional uses of dispersity. We assume a connection oriented realtime communication service such as that provided by the Tenet Suite 1 or Asynchronous Transfer Mode (ATM) networks. We use the ideas of dispersity routing, redundancy, disjoint paths, and hot and cold standbys to design and classify a set of schemes that can provide a range of fault‐tolerant realtime services. The classification provides a convenient framework, which we use to discuss the properties of the schemes and to conduct simulation experiments. We compare the service provided and the costs of our schemes to other approaches to fault‐tolerant realtime communication, such as the Internet approach. We conclude that dispersity routing is a flexible approach to increasing the fault tolerance of realtime connections, which can provide a range of improvements in service with a corresponding range of costs.
A secure and optimally efficient multi‐authority election scheme
Authors: Cramer Ronald , Gennaro Rosario , Schoenmakers Berry 
Published: September 2008

AbstractIn this paper we present a new multi‐authority secret‐ballot election scheme that guarantees privacy, universal veriability, and robustness. It is the first scheme for which the performance is optimal in the sense that time and communication complexity is minimal both for the individual voters and the authorities. An interesting property of the scheme is that the t and communication complexity for the voter is independent of the number of authorities. A voter simply posts a single encrypted message accompanied by a compact proof that it contains a valid vote. Our result is complementary to the result by Cramer, Franklin, Schoenmakers, and Yung in the sense that in their scheme the work for voters is linear in the number of authorities but can be instantiated to yield information‐theoretic privacy, while in our scheme the voter's effort is independent of the number of authorities but always provides computational privacy‐protection. We will also point out that the majority proposed voting schemes provide computational privacy only (often without even considering the lack of information‐theoretic privacy), and that our new scheme is by far superior to those schemes.
Design of time‐differential GCRA enforcer and shaper in multi‐service ATM networks
Authors: Wu Jung‐Shyr , Kuo Fang‐Jang 
Published: September 2008

AbstractAccording to the ITU‐T Recommendation 1.371, the Generic Cell Rate Algorithm (GCRA) is used to define Peak Cell Rate for the ATM network. It is further applied by the ATM Forum to define Sustainable Cell Rate and Burst Tolerance so as to facilitate Usage Parameter Control and Network Parameter Control. To check the validity of a cell according to the declared traffic parameters, the enforcer must read die clock time when a cell arrives. However, the clock of the enforcer would roll over frequently and thus makes wrong judgment. On the other hand, for a shaper in a customer premise node to dispatch cells conforming to the declared parameters, the clock would also roll over and the cell would not be dispatched correctly. To overcome the problems introduced by clock roll‐over, we propose two modifiedGCRAsfor the enforcer and the shaper, respectively. According to the proposed algorithms, we design new architectures for multi‐connection shapers and enforcers in which a cell's priority is also considered. We also prove that the proposed algorithms are justified for the proposed architectures.
Letter: Exact formulas for computing the energy of “square” and “cross” two‐dimensional rectangular signal constellations
Authors: Sterian Corneliu‐Eugen D. 
Published: September 2008

AbstractA rigorous construction of “cross” constellations is given and the exact formulas for calculating the average norm of rectangular signal sets is derived. Using these formulas, the increase of the average norm when doubling the size of the constellation is evaluated.
Impact of the time error sampling period on telecommunications clock stability measures
Authors: Bregni Stefano , Carbonelli Marco , De Seta Domenico , Perucchini Daniele 
Published: September 2008

AbstractFive stability quantities have been considered in the new telecommunications international standards for clock specification: the Allan Deviation, the Modified Allan Deviation, the Time Deviation, the root mean square of the Time Interval Error and the Maximum Time Interval Error. A key issue to consider carefully ‐ but sometimes overlooked ‐ when performing stability measurements, in order to draw meaningful conclusions from the measurement data, is the impact of the TE sampling period on the behaviour of the stability quantities. Such a dependence, for some of the quantities above, has been already pointed out in different reference papers, which studied in depth the behaviour of the stability quantities analytically and under various aspects. In order to provide further, sourly information on the impact that the TE sampling period may have in practice on the measured stability quantities, this paper reports a broad set of simulation results, under the presence of all the power‐law clock noises and for all the stability quantities, together with some experimental results. The results obtained confirm, in excellent agreement with the theoretical analyses, that the behaviour of the Modified Allan Deviation and of the Time Deviation is substantially dependent on the chosen measurement sampling period in the observation intervals where white and flicker phase noises dominate.
Performance of joint diversity and equalization techniques in an indoor radio environment
Authors: Dossi Laura , Tartara Guido 
Published: September 2008

AbstractThe measured wideband complex impulse response profiles from eight different indoor areas are used to evaluate the performance of joint diversity and equalization techniques in the presence of flat fading and frequency selective fading. The error probabilities of a joint two‐branch diversity receiver with an adaptive finite‐length equalizer on each branch, whose taps are jointly optimized according to the minimum mean square error criterion, are computed for different data rates using the measured channel responses.
Multicarrier modulation system with erasures‐correcting decoding for nakagami fading channels
Authors: Goldfeld Lev , Wulich Dov 
Published: September 2008

AbstractThe Multi Carrier Modulation (MCM) system with soft decision erasures correcting decoding based on a block code applied for Nakagami fading channel is considered. Upper and lower estimations of the Bit Error Rate (BER) have been found. Good agreement between simulated and theoretical results has been obtained. It is shown that for low SNR the proposed system has lowerBERthan MCM with Trellis Code Modulation (TCM). Moreover the decision delay needed for the proposed system is much lower than for the TCM based system.
Performance comparison of different dynamic channel allocation techniques for mobile satellite systems
Authors: Re Enrico Del , Fantacci Romano , Giambene Giovanni 
Published: September 2008

AbstractDynamic Channel Allocation (DCA) techniques permit a high resource utilization in cellular networks and are able to adapt themselves in the presence of rapid variations of traffic loads offered to the cells. Therefore, they are particularly suitable for Mobile Satellite Systems (MSSs). This paper compares the performance of several DCA solutions that are based on the evaluation of a cost function in terms of both quality of service parameters (i.e., blocking probabilities) and signaling load to be supported by the system. Both GEostationary Orbit (GEO) and Low Earth Orbit (LEO) MSSs have been considered. A particularly interesting DCA solution is proposed that tries to serve a new call attempt in a cell where no channel is available by means of a channel reconfiguration in an interfering cell. Handover requests that do not attain immediately service can be queued for a maximum time in order to enhance system performance.
Computing error probabilities over fading channels: A unified approach
Authors: Biglieri Ezio , Caire Giuseppe , Taricco Giorgio , Ventura‐Traveset Javier 
Published: September 2008

AbstractThis paper is a tutorial on the calculation of error probabilities for fading channels. The method we advocate is centered on the evaluation of the Laplace transform Φδ(s) of the probability density function of the difference A between the metrics of two competing signal sequences. In some cases, knowledge of the function Φδ (s) allows one to determine error probabilities exactly in closed form, or asymptotically as the signal‐to‐noise ratio grows to infinity. The general technique t hat we describe here allows their computation in numerical form to any desired degree of accuracy. Coded as well as uncoded transmission can be considered in this unified framework. For illustration's sake, some examples of calculations are provided for frequency‐flat slow‐fading channels in which coherent detection is used, and the channel state information is perfect, or unavailable, or obtained from a noisy pilot tone.
Still picture compression based on psychovisual image‐pattern coding
Authors: Favalli Lorenzo , Mecocci Alessandro , Poli Andrea 
Published: September 2008

AbstractIn this paper, an approach that integrates different compression techniques is presented. The goal is to reach high compression rates for still pictures without introducing relevant visual distortions in the images. This is obtained by using a “second generation” compression scheme which adaptively uses different psychovisual techniques to reduce the image bitrate. Each image is analysed on a block by block basis and the most appropriate coding strategy is selected according to the characteristics of the current block and of surrounding blocks. Taking into account surrounding blocks leads to improved visual image quality. Another important feature of the proposed approach is that part of the approximation job is done at the receiver thus further reducing the bit rte needed for transmission.
Adaptive antennas in microwave‐PCS coexisting systems
Authors: Muñoz‐Rodriguez David , Mazlum ‐Revueltas Abdo 
Published: September 2008

AbstractIn this paper, mutual interference in PCS and microwave systems in a spectrum sharing scenario is analyzed. Typical values for operating MW links and cellular systems are used for evaluation. The use of adaptable smart antenna systems as a mean to reduce intersystem interference is proposed. The access techniques for PCS considered are: TDMA, FDMA and CDMA. Carrier to Interference ratio is adopted as performance criterion. Geographical separation required between both systems for their operation in terms of antennas separation is studied for different scenarios. The impact of proposed strategies in PCS system capacity for CDMA is also reported.
The VDSL transmission challenge
Authors: Cheong Kok‐Wui , Kim Joonsuk , Cioffi John M. , Kwon Ho‐Yeol , Chun You‐Sik , Yoo Kyung‐Hyun 
Published: September 2008

AbstractDemand for high speed digital transmission on ordinary phone lines motivates the introduction of VDSL. This paper investigates the VDSL transmission environment. The channel is shown to be difficult for high speed digital transmission and sophisticated signal processing methods are required for reliable transmission. This paper also describes various transmission schemes that are proposed to support high data rates in the difficult transmission environment. Two schemes, SDMT and QAM/CAP, are compared in terms of SNR margins and computational complexity.
Adaptive soft‐decision algorithms for mobile fading channels
Authors: Anastasopoulos Achilleas , Polydoros Andreas 
Published: September 2008

AbstractThis paper addresses the task of joint symbol‐by‐symbol decisions and channel estimation in a coded/interleaved/frequency‐selective fading channel. Based on two popular soft‐decision algorithms, namely OSA and SSA, which have an inherent trellis structure, several adaptive derivatives are proposed. In particular, by extending the concept of Conventional Adaptive MLSE (CA‐MLSE) receiver to the soft‐decision case, the CA‐OSA and CA‐SSA algorithms are derived. Moreover, using the Per‐Survivor Processing (PSP) concept, two new adaptive extensions are presented, namely PSP‐OSA and PSP‐SSA. The latter of these algorithms (PSP‐SSA) has a simplified form with complexity comparable to PSP‐MLSE. Simulation results show a significant improvement of the suggested adaptive soft‐decision algorithms over the standard configuration, which consists of a hard‐decision channel equalizer followed by a convolutional decoder.
Interference mitigation in spread spectrum systems by wavelet coefficients thresholding
Authors: Landry René J. R. , Mouyon Philippe , Lekaïm David 
Published: September 2008

AbstractThis paper studies a potential EMI (Electro Magnetic Interference) rejection technique for the GPS Standard Positioning Service in an avionics environment. Its generalisation to any Direct Sequence Spread Spectrum (DSSS) Systems is also considered. The paper gives a brief overview of Wavelet Theory, which is well established for noise reduction but which is applied here to Continuous Wave Interference (CWI) and narrowband interference. The originality of this work lies in a method for signal rejection, taking into account features in both time and frequency domains to account for the non‐stationary characteristics of the interference. Because the software‐based receiver is more flexible, less expensive and more accurate compared with typical hardware receivers, a Generic GPS Receiver has been implemented in software [1] to validate the antijamming technique developed in this paper. The aim of the Monte Carlo simulations is to get a good idea of the Performances of the Wavelet Filter against a various types of Interferences and to compare the results with traditional processing.