bluuebunny/crossref_metadata_2025_split huggingface dataset:
Letter: Low bit‐rate vector quantization with progressive transmission
Authors: Poggi Giovanni 
Published: September 2008

AbstractThis paper proposes a VQ‐based coding scheme to perform the fast progressive transmission of images. The basic idea is to exploit the inter‐block correlation by jointly encoding the indexes generated by the vector quantizer. The use of ordered codebooks for VQ guarantees that the indexes are highly correlated and therefore that the compression will be successful. In order to preserve the progressive transmission property, the compression is carried out at the bit‐plane level, by means of a classified‐predictive encoding scheme. Numerical experiments on well‐known test images show a rate reduction of about 30% in case of full‐transmission, and of over 60% in case of partial‐transmission, the latter being by far the most common situation in the applications.
Improving the performance of CDMA systems in a multipath delay and fading environment
Authors: Hu Lan , Burkley Cyril J. 
Published: September 2008

AbstractIn this paper, a new channel filter is proposed for a CDMA direct‐sequence spread‐spectrum system in a multi‐user and multipath delay and fading environment. In the proposed system, the channel filter is placed before the acquisition system to overcome the multipath delay and co‐channel interference effects. Monte Carlo simulation is used to evaluate and compare the performance of the system in terms of multi‐user interference and multipath delay both with and without the proposed channel filter. Results show that the proposed technique can significantly improve the overall system performance. Details of the system configuration, the design concept of the channel filter and the simulation techniques used are discussed.
Letter: Doppler optimised compression filters for both aperiodical and periodical sequences
Authors: Zejak Aleksa J. , Dukić Miroslav L. 
Published: September 2008

AbstractThe problem of designing Spread Spectrum (SS) radar detection filters that minimise sidelobe (SL) levels in both Doppler and range co‐ordinates is considered and a new algorithm for the Doppler optimised mismatched filter is presented. The Iterative Reweighted Least Square (IRLS) procedure for minimax filter coefficients calculation is applied. A special attention has been paid to the analysis of Code Division Multiple Access (CDMA) SS communication systems. The computer simulation results obtained show that SL levels rejection using a new algorithm is very high, both for aperiodical and periodical sequences.
Robust programmable‐rate wireless graphical correspondence
Authors: Hanzo Lajos , Yuen Andy H. 
Published: September 2008

AbstractAn adaptive fixed‐length differential chain coding (FL‐DCC) scheme is proposed for the transmission of line graphics, which canbe re‐configured as a lower rate, lower resolution or higher rate, higher resolution source codec. Compared to Differential Chain Coding (DCC), the proposed FL‐DCC codec has a lower coding rate in both of its lower‐ and higher‐rate operating modes, while maintaining a similar subjective graphical quality. The dual‐rate re‐configurable FL‐DCC codec is embedded in a voice, video multimedia communicator system, which allocates the FL‐DCC graphics packets to idle speech packets with the aid of the Packet Reservation Multiple Access (PRMA) multiplexer. In a bandwidth of 200 kHz, which is characteristic of the Pan‐European GSM system, nine speech, video and graphics multimedia users can be accommodated using bandwidth efficient 16‐level Quadrature Amplitude Modulation (16QAM) over benign microcellular channels. Under less favourable propagation conditions the more robust, but less bandwidth efficient 4QAM mode of operation can be invoked. In the diversity‐aided and automatic repeat request (ARQ) assisted 16QAM mode of operation the multimedia user bandwidth becomes 22.2 kHz and the minimum required channel signal to noise ratio (SNR) over AWGN and Rayleigh channels is about 11 and 15 dB, respectively. The most salient system features are summarised in Table 2.
A new software architecture for evolvable multimedia software
Authors: Itoh Jun‐Ichiro , Yokote Yasuhiko , Feret Michel 
Published: September 2008

AbstractThis paper describes the Micro Virtual Machine and the operating system (OS) interface that Sony has designed and implemented for Sony's future products such as set top boxes and servers for the delivery of on‐line multimedia services. This article is derived from a proposal document presented at the 11‐th meeting of the Digital Audio‐Visual Council (DAVIC) held in Berlin in December 1995. The technologies presented in this paper were first used at Telecom 95 in Geneva and later in the DAVIC inter‐operability trials which took place in Tokyo in the Fall of 1996.
Feedforward frequency estimation for PSK: A tutorial review
Authors: Morelli Michele , Mengali Umberto 
Published: September 2008

AbstractThis paper considers feedforward carrier frequency estimation methods in burst‐mode digital transmission, with tutorial objectives foremost. Assuming PSK modulation, two scenarios are envisaged in which frequency estimates are derived either from a preamble appended to the data block, or directly from the modulated signal. Several estimation algorithms are considered with different and somewhat contrasting characteristics. The characteristics we focus on are: estimation accuracy, estimation range, minimum operating signal‐to‐noise ratio (threshold), and implementation complexity. They provide a framework within which current estimation methods can be evaluated. The paper reviews and compares some prominent algorithms proposed in literature, trying to single out the best ones for a given application.
Adaptive linear interference suppression for packet DS‐CDMA
Authors: Honig Michael L. 
Published: September 2008

AbstractThe performance of adaptive linear interference suppression is studied in the context of packet DS‐CDMA. A multi‐cell system is assumed with stochastic arrivals and departures of asynchronous users, and additive Gaussian noise as the only channel impairment. Interference suppression is achieved with a tapped‐delay line filter, where the filter spans a single symbol interval. Adaptive algorithms considered include the stochastic gradient (LMS), exponentially‐weighted Least Squares (LS), block LS, and a reduced‐rank LS algorithm. The reduced‐rank LS algorithm first projects the received signal onto a signal sub‐space spanned by eigenvectors of the averaged outer product matrix of received vectors. The purpose of the projection is to eliminate low‐level background interference and noise. Both decision‐directed and blind algorithms, which do not require a training sequence, are compared. Computer simulation is used to obtain error rates as a function of traffic load, and algorithm and system parameters (including timing offset). Results indicate that the adaptive algorithms offer a significant increase in capacity (nearly a factor of two at moderate error rates), and are insensitive to variations in received power over the user population.
Measurements and simulations of cell delays in ATM switches
Authors: Wittevrongel Sabine , De Vleeschauwer Danny , Bruneel Herwig , Brinkmann Axel , De Vries Rein 
Published: September 2008

AbstractWithin the RACE project EXPLOIT, traffic experiments are being performed on an ATM testbed, the EXPLOIT Testbed, which is situated in Basel. A subset of these experiments is described in this paper. Specifically, the network performance parameter cell delay, and especially the part due to queueing effects, is focused on. The aim of this paper is to compare the measurement results with the results of a generic simulation model based on renewal theory. It is shown that the simulation model predicts the delay histogram very well, but slightly underestimates the covariance over time of die delays.
Lettereffect of enhanced leaky bucket parameters on the maximum queue length: Worst‐case analysis
Authors: Wu Jung‐Shyr , Su Shyh‐Wen 
Published: September 2008

AbstractIn ATM networks, various usage parameter control (UPC) strategies are used to regulate incoming traffic according to the characteristics of the sources declared at call set‐up. Among these UPC schemes, the Leaky Bucket method is well‐known and has been discussed extensively. In this paper, we study the characteristics of the multiplexer in which cell arrivals are first policed by Enhanced Leaky‐Buckets (ELBs) before entering the system. In addition to both policing mean cell rate and peak cell rate, cell delay variation (CDV) are also taken into consideration for each ELB. We derive the upper and lower bounds on the maximum queue length expressed as a funtion of the ELB parameters and the number of sources. We also rigorously prove that these bounds occur with respect to a coincident token‐generating pattern and a perfectly interleaved token‐generating pattern, respectively.
Demodulation and decoding of trellis coded continuous phase modulations in an incoherent mobile radio environment
Authors: Abrardo Andrea , Mori Alessandro , Benelli Gluliano 
Published: September 2008

AbstractDigital communication systems using Trellis Coded‐Continuous Phase Modulations (TC‐CPM) have been shown to be power efficient, both for coherent and incoherent detection. In this paper some techniques for the incoherent detection of TC‐CPM signals in a radio‐mobile environment are studied. Two different differential decoding algorithms for the detection of TC‐CPM are presented. The first one is a Viterbi algorithm characterised by a reduced number of states when compared with the classical coherent Viterbi detector. The second one is a modified SAN(B) algorithm for the incoherent detection of convoluttonally encoded CPM over a mobile radio environment. Comparisons with the coherent Viterbi decoder show that the proposed algorithms are quite attractive, especially in the case of frequency non‐selective radiomobile channels.
Analysis of the effect of phase noise in OFDM systems
Authors: Tomba Luciano 
Published: September 2008

AbstractMulticarrier systems are gaining much attention for their possible application to the transmission of asynchronous transfer mode (ATM) data packets over indoor radio channels. Due to the high frequency selectivity of these channels, at data rate of some tens of Mbits/s multicarrier modulation appears a convenient technique to reduce the intersymbol interference produced by multipath propagation. However, multicarrier modulation exhibits a significant sensitivity to the phase noise of the oscillator used for frequency down‐conversion at the receiver. In order to give a quantitative measure of such impairment, in this paper we evaluate the impact of the oscillator phase noise on the system performance and, in particular, four modulation schemes are compared.
MACSE: A generic connection establishment protocol for multimedia communication residing at the OSI application layer
Authors: Orphanos George N. , Papadopoulos George D. , Koubias Stavros A. 
Published: September 2008

AbstractThe multiple association control service element (MACSE) described in this work is a new connection establishment protocol for the application layer of the OSI reference model (OSIRM). The objective of the protocol is efficient establishment and control of multimedia associations among multiple spatially dispersed users. MACSE defines a new OSI service to support the communication requirements of multimedia applications so as to shift the burden of setting‐up a complex call to a protocol entity, instead of the application developer. The MACSE protocol enhances the OSIRM by introducing careful service definition, service primitives and relevant parameters, as well as a non‐monolithic protocol specification. The protocol defines procedures for the negotiation and confirmation of quality of service (QoS) per association while it forms the core of a proposed architectural model which provides a coherent treatment of QoS across all layers of the OSIRM and reduces the complexity of it. Out‐of‐band, rather than in‐band, signalling at the application layer and multi‐target associations are introduced and analysed, in contrast to the structure of the well‐known OSI association control service element (ACSE) protocol. Moreover, ACSE can be considered a particular case of MACSE.
Coherent and noncoherent decoding metrics for the is‐95 reverse link
Authors: Frank Colin D. , Ling Fuyun , Scnaffner Terry M. 
Published: September 2008

AbstractThe IS‐95 [1] reverse link modulation chain consists of a rate 1/3 convolutional code, a bit‐level interleaver, and 64‐ary orthogonal modulator. The interleaver improves the performance of the convolutional code by intreducing time diversity. However, calculation of the log‐likelihood ratio for the combination of bil‐level interleaving and 64‐ary orthogonal modulation is difficult and may require detailed knowledge of the channel fading process. Several decoding metrics have teen published in me literature including the single‐ and dual‐max metrics [2, 3], This paper presents two decoding metrics, the weighted dual‐max and the coherent dual‐max, which are non‐parametric, reasonable in complexity, and which improve on die performance of the dual‐max by 0.3 dB and 1.5 dB respectively.
Joint intersymbol and multiple‐access interference suppression algorithms for CDMA systems
Authors: Beheshti Soosan , Wornell Gregory W. , Isabelle Steven H. 
Published: September 2008

AbstractTwo promising classes of techniques are developed for efficient multiuser detection in code‐division multiple‐access (CDMA) communication systems subject to fading due to time‐varying multipath propagation. Both are designed to jointly suppress both intersymbol and multiple‐access interference inherent in such systems, and exploit all available time and frequency diversity. The first is a family of linear receivers for time‐varying multiuser channels that generalize familiar linear equalizers designed for traditional single‐user linear time‐invariant channels. Minimum mean‐square error, zero‐forcing, and matched‐filter versions of such multiuser detectors are all developed within a common state‐space framework, and have convenient recursive implementations. Performance issues as well as natural decision‐feedback variants of the detector structure are both discussed. The second is a family of nonlinear receivers that are specifically designed for use with spread‐signature CDMA systems on time‐varying multipath channels. These multiuser detectors employ a batch‐iterative (multipass or “turbo” stayl) decoding algorithm based on a successive‐cancellation strategy. Several aspects of the performance of this algorithm are developed, including its monotonic convergence property. Collectively, these two classes of algorithmic structures for joint equalization, interference suppression, demodulation, and detection are representative of several emerging and interrelated approaches to receiver design for next‐generation CDMA systems.
Iterative detection in code‐division multiple‐access with error control coding
Authors: Alexander Paul D. , Grant Alex J. , Reed Mark C. 
Published: September 2008

AbstractA code‐division multiple‐access system with channel coding may be viewed as a serially‐concatenated coded system. In this paper we propose a low complexity method for decoding the resulting inner code (due to the spreading sequence), which allows iterative (turbo) decoding of the serially‐concatenated code pair. The per‐bit complexity of the proposed decoder increases only linearly with the number of users. Performance within a fraction of a dB of the single user bound for heavily loaded asynchronous CDMA is shown both by simulation and analytically.
Probability of error for diversity combining in DS CDMA systems with synchronization errors
Authors: Sunay M. Oǧuz , McLane Peter J. 
Published: September 2008

AbstractAn efficient series that is used to calculate the probability of error for a BPSK modulated DS CDMA system with chip timing and carrier phase errors in a slowly fading, multipath channel is derived. The receiver is assumed to be a coherent RAKE receiver. Three types of diversity schemes are considered: selection diversity, equal gain diversity combining and maximal ratio diversity combining. The error probability derivation does not resort to the widely used Gaussian approximation for the intersymbol interference and multiple access interference and is very accurate. The derived series for probability of error calculations is used to assess the reduction in the system capacity due to different levels of synchronization errors. For all three diversity combining schemes considered, the degradation in the system performance is expressed as an effective reduction in the system processing gain. Systems of 1.25 MHz, 5 MHz and 10 MHz are considered for different number of diversity branches and it is shown that the percentage reduction in the system capacity due to synchronization errors is approximately the same for all these systems.
A hybrid‐ARQ system using rate‐compatible trellis codes designed for rayleigh fading
Authors: Eröz Mustafa , Fuja Tomas E. 
Published: September 2008

AbstractThis paper presents classes of rate‐compatible trellis codes designed for channels with flat, slow Rayleigh fading. The codes are “multiple” TCM (MTCM) codes as proposed by Divsalar and Simon – i.e., codes in which multiple symbols are associated with each transition through the trellis; by applying appropriate puncturing tables to low‐rate MTCM codes we obtain families of MTCM codes, all of which can be decoded with (essentially) the same decoder. By means of computer search, several such families are obtained so that each family member is at least as good as any comparable code in the literature. (“Good” here is defined in terms of minimum time diversity and minimum squared product distance, the most important parameters for performance over Rayleigh fading channels). A protocol to implement these rate‐compatible trellis codes in a type‐II hybrid ARQ format is described. The proposed protocol selectively punctures symbols from the low‐rate code based on the observed fading values observed on each branch. Upper bounds on the resulting bit error rate are developed and the results are used to select the best adaptive code from several possibilities. Simulation results comparing the proposed scheme with fixed‐rate codes of the same throughput show substantial coding gain. Finally a protocol modification limiting the variability of the code rate over a frame is described; this modification eliminates the need for excessive buffering, with a very small effect on performance.
Orthogonal frequency‐division multiple access and its application to CATV networks
Authors: Sari Hikmet , Karam Georges 
Published: September 2008

AbstractWe introduce the concept of orthogonal frequency‐division multiple access (OFDMA) and investigate its application to send upstream information from subscriber premises to the cable head‐end in cable TV (CATV) networks. The carrier and timing synchronizations needed to ensure orthogonality between different subscriber signals are achieved by sending common pilot signals from the head‐end. WhereasNdemodulators are required to accommodateNsimultaneous users in conventional FDMA systems, OFDMA only requires a single demodulator followed by anN‐point discrete Fourier transform (DFT). We analyze the performance of this technique and compare it to time‐division multiple access (TDMA) which appears in several international standards. Our results indicate that OFDMA is an attractive multiple access technique which offers increased robustness to narrowband interference, impulse noise, and other signal impairments which characterize typical CATV networks.
Influence of dispersive waves on vector soliton propagation
Authors: Midrio Michele 
Published: September 2008

AbstractA perturbation theory for the coupled nonlinear Schrödinger (NLS) equations is developed to investigate the effect of the background radiation on the soliton amplitude, frequency and polarization angle. By resorting to the theory of the inverse scattering transform, it is shown that the background radiation can be taken into account by evaluating the off diagonal terms of the scattering matrix associated with the coupled NLS equations. The theory is applied to the characterization of the soliton amplitude decrease observed in the propagation in the presence of loss and periodical amplification.
A feed‐forward technique for initial reference parameter estimation in burst mode PSK demodulation
Authors: Andronico Maurizio , Casale Salvatore , Corte Aurelio La 
Published: September 2008

AbstractIn burst mode communications, fast and efficient estimation of demodulator reference parameters is a key issue as receivers must be able to correctly synchronize on short bursts of data. To do so, it is possible to use a preamble in each data burst as long as the algorithms used require very short preambles and therefore do not degrade communication efficiency excessively. If a preamble is used, in fact, estimation performance is better than when a fully modulated carrier is used. In this paper the authors propose a novel feedforward technique for reference parameter recovery in PSK demodulation, the main characteristics of which are robustness to frequency offsets, short acquisition time and ease of implementation, even with low‐cost digital hardware. The technique is based on a very short special carrier preamble modulated by a known pattern, which allows the reference parameters to be estimated simultaneously and directly.
A Modified PRMA Protocol for Joint Voice Data Packet Wireless Networks
Authors: Capella Riccardo , Re Enrico Del , Fantacci Romano 
Published: September 2008

AbstractThis paper discusses the possibility of using the Packet Reservation Multiple Access (PRMA) protocol to provide spatially dispersed voice and data user terminals wireless access to a base station over a common short‐range radio channel. The case of ideal radio channel propagation conditions as well as that of non‐ideal and non‐stationary radio channel propagation conditions is considered. A modified PRMA (MPRMA) protocol is proposed in order to enhance system performance under heavy traffic load conditions. A technique to break off the possibility of accessing the common radio channel by a data user terminal is also discussed to avoid unsuccessful transmission of data packets during poor channel conditions. Performance comparisons with the standard PRMA protocol clearly point out a better behavior for the proposed MPRMA protocol.
Tight Upper Bounds for Cell Loss Probabilities and Required Bandwidth Estimation in ATM Multiplexers
Authors: Xiaoming Lru , Liming Liu , Bensaou Brahim , Tsang Danny H. K. 
Published: September 2008

AbstractEstimating the cell loss probability in an ATM multiplexer is a key issue in network management and traffic control tasks such as call admission control and bandwidth allocation. In this paper, we derive a new approximation to estimate the total and individual cell loss probabilities in an ATM multiplexer fed by a superposition of heterogeneous on‐off sources. Based on this approximation, a simple algorithm is proposed to estimate accurately the aggregate required bandwidth to guarantee a given cell loss probability. Numerical results and comparisons to alternative approaches are also shown.