bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance of cell loss priority management schemes in shared buffers with poisson arrivals
Authors: Van Mieghem Piet , David Johan , Petit Guido H. 
Published: September 2008

AbstractThe performances of two important cell loss priority mechanisms (CLPM) in shared buffers withNservers, Partial Buffer Sharing (N‐PBS) and Push‐Out Buffer (JV‐POB), are compared. Each arriving flowiis guided to a shared queue of sizeKwhere it is served by the correspondingi‐th server. Further, these flows are Poissonean, independent of each other and consist of a uniformly distributed mix of high (H) and low (L) priorities. Subject to the required cell loss ratios for both priorities,clr*Landclr*H, we determine the maximum allowable traffic intensity λmaxfor each incoming traffic flow as a function of the global priority mix in the buffer of sizeK.For an arbitrary CLPM, the maximum allowable load is achieved in the symmetrical traffic situation where allNlinks carry the same load. Only when N> 1, theN‐POB scheme is found to be superior in performance toN‐PBSover the whole priority mix range and for realistic cell loss ratio requirements. Moreover, the difference in performance betweenN‐POB andN‐PBS increases with increasingN, but decreases with increasingK.Finally, a methodology based on buffer size scaling has enabled the computation of the performance of theN‐POB.
Performance of a fixed‐beam system in the is‐95 CDMA forward link
Authors: Moorti Tushar , Paulraj Arogyaswami , Stützle Rupert 
Published: September 2008

AbstractWe study the performance of a fixed‐beam system in the forward link of IS‐95 CDMA systems by means of Monte Carlo simulations. The simulations are performed using a comprehensive model of the forward link which includes correlated shadowing, soft and softer handoff, and transmit power allocation. The effects of user distribution, soft/softer handoff threshold, and multipath diversity are examined. We find that the availability of signal diversity plays an important role in the system performance. When the soft handoff threshold is decreased from ‐12 dB to ‐18 dB, capacity increases by 15%, but handoff overhead more than doubles. When fifty percent of users have 2‐ray multipath, capacity increases by 18%. Thus, the availability of multipath in the system has a dramatic influence on forward link capacity. A non‐uniform distribution using a “highways” model reduces capacity by more than a half. This shows that for successful implementation of a fixed‐beam system, it is important to plan cell sites in a way that keeps loading uniformly distributed in azimuth.
MC‐CDMA with quadrature spreading for wireless communication systems
Authors: Slimane Slimane Ben 
Published: September 2008

AbstractMulti‐Carrier CDMA (MC‐CDMA) systems using the Orthogonal Frequency Division Division Multiple Access (OFDM) technique resolve the frequency selectivity in multipath fading channels and have good spectral properties. The addition of a spread spectrum component to the OFDM introduces a frequency diversity gain that can combat deep multipath fading situations. In this paper a MC‐CDMA system operating over frequency selective, slowly fading channels is considered and its performance is studied analytically and by computer simulations. We consider the downlink of a cellular radio system where for each user a BPSK modulation and a quadrature (complex) spreading code is used. The spreading codes are arranged in a way that reduces the effect of the multipath fading channel and restores some of the orthogonality losses between users. The obtained results show considerable performance improvement compared to conventional OFDM and to MC‐CDMA that uses single spreading codes. The effect of frequency offsets on the system performance is also addressed in this paper. Its superior performance and low complexity receiver make MC‐CDMA with quadrature spreading codes suitable for future wireless communication systems to achieve the requirements of high quality services, high speed, and low cost‐receiver.
Efficient implementation of linear multiuser detectors for asynchronous CDMA systems by linear interference cancellation
Authors: Elders‐Boll Harald , Schotten Hans Dieter , Busboom Axel 
Published: September 2008

AbstractThe decorrelating and the linear, minimum mean‐squared error (MMSE) detector for asynchronous code‐division multiple‐access communications are ideally infinite memory‐length detectors. Finite memory approximations of these detectors require the inversion of a correlation matrix whose dimension is given by the product of the number of active users and the length of the processing window. With increasing number of active users or increasing length of the processing window, the calculation of the inverse may soon become numerically very expensive. In this paper, we prove that the decorrelating and the linear MMSE detector can both be realized by linear multistage interference cancellation algorithms with ideally an infinite number of stages. It will be shown that depending on the signal‐to‐noise ratio, the number of active users, and the choice of the cancellation algorithm, only a few stages are necessary to obtain the sameBERperformance as with the ideal detectors. The computational costs for one stage of a linear interference cancellation algorithm are essentially given by one matrix‐vector multiplication. Thus, the computational complexity can be reduced considerably. Since each stage introduces a time delay equivalent to the bit duration, the number of stages also determines the detection delay. Because a few stages are sufficient, this approach can also be used to obtain receiver structures with low memory consumption and detection delay.
A lower bound on the bit‐error‐rate resulting from mismatched viterbi decoding
Authors: Lapidoth Amos , Shamai (Shitz) Shlomo 
Published: September 2008

AbstractA lower bound is derived on the bit error rate that results when a rate l/nconvolutionally encoded binary data stream is transmitted over a noisy symmetric channel, and is then decoded using a mismatched Viterbi decoder, i.e., a Viterbi decoder that performs maximum‐likelihood sequence estimation using possibly incorrect branch metrics. The branch metrics are assumed to be symmetric, but are generally differrent from the log‐likelihood function. The proposed bound is expressed in terms of the pairwise error probability for a given error event normalized by the sum of the events length and the code's memory. While the bound can be somewhat loose for medium signal‐to‐noise ratios, it is usually asymptotically tight at high signal‐to‐noise ratios. For the special case where the branch metrics employed are equal to the log‐likelihood function our lower bound does not coincide with the standard bound that was derived by Forney and Mazo. It falls short by a multiplicative constant that depends on the code's memory and the shortest error event of minimum Hamming weight. We apply our lower bound to the study of convolutionally encoded direct‐sequence spread‐spectrum communication with Laplacian noise and show that nearest‐neighbor decoding, which is optimal for Gaussian noise, is sub‐optimal and asymptotically (for high processing gain) results in a 3 dB loss in performance when compared with the optimal maximum‐likelihood decoder. Extensions to ratec/nconvolutional encoders, general trellis encoders and to symmetric channels with memory are also presented.
On the optimisation of a noncoherent CDMA system based onM‐ary orthogonal modulation
Authors: Benthin Marcus , Pelz Rodolfo Mann , Kammeyer Karl‐Dirk , Nikolai Dirk 
Published: September 2008

AbstractThis paper concerns the optimisation of a DS‐CDMA based mobile communication system with respect to the transmission quality in the case of data and video services respectively. For combatting transmission errors, forward error protection based on convolutional codes and interleaving in connection with soft decision maximum‐likelihood (ML) decoding through the Viterbi algorithm is applied. In this context, a technique to generate post‐decision reliability information in the case of a noncoherent DS‐CDMA receiver for a given ML metric is presented. The proposed error control strategy involves the application of equal error protection for raw data transmission with the average post‐decodingBERas an optimisation criterion. In the case of a video transmission, a‐priori knowledge regarding the error sensitivity of individual parameter sets suggests an unequal error protection strategy based on punctured convolutional codes, where the segmentalSNRat the source codec output represents the optimisation criterion. Due to the high complexity of the system under investigation, corresponding results are obtained through simulation of the point‐to‐point transmission link. A significant gain regarding the achievable transmission quality with respect to conventional approaches can be achieved in connection with a compound design of source coding, channel coding and spectral spreading.
Performance of residue number system based DS‐CDMA over multipath fading channels using orthogonal sequences
Authors: Yang Lie‐Lung , Hanzo Lajos 
Published: September 2008

AbstractThis paper is concerned with a new direct‐sequence spread‐spectrum multiple‐access communication system based on the so‐called residue number system (RNS) or redundant residue number system (RRNS). The system operates in a multi‐path fading environment, and a RAKE receiver structure with maximum ratio combining is used for demodulation. Approximations to the error probabilities are given by using Gaussian statistics for the multiple‐access and the multipath interference. Concatenated codes employing residue number system product codes (RNS‐PC) as the inner codes and nonbinary Reed‐Solomon (RS) codes as the outer codes are adopted to improve the system performance. The performance of the system is determined for a range of different length RNS‐PC schemes. The results show that, for a given outer RS code and a given number of moduli of the inner RNS‐PC, the performance of the system can be optimized by varying the relative number of information moduli and redundant moduli of the inner RNS‐PC and the moduli's values.
Analytical computation of the error probability of (G)MSK with adaptive sampling in mobile radio channels
Authors: Molisch Andreas F. , Paier Mario , Bonek Ernst 
Published: September 2008

AbstractWe extend the analytical computation of the error probability of (Gauss‐filtered) Minimum Shift Keying (G)MSK with adaptive determination of the sampling time in mobile radio channels. We present a new method that allows to include i) anN‐path fading channel (withST, whereSis the rms delay spread, andT” the bit length) and ii) noise. We show that the errors due to ISI go likeK(SIT)2, where the proportionality constantKdepends on the Gaussian filtering, the receiver filtering, and the sampling time. The chosen sampling instants for large group delays depend on the signal‐to‐noise ratios: for lowSNR, sampling times near the average mean delay are optimum, while at highSNR, sampling times that are shifted by approximatelyT/2 are optimum.
Evolutionary Searching in Cellular Radio Systems Planning
Authors: Jaimes‐Romero Fernando , Muñoz‐Rodriguez David 
Published: September 2008

AbstractIn this paper the suitability of genetic algorithms (GA) as an alternative tool to cope with some design problems in cellular radio is studied. We particularly studied the channel assignment problem for wich two algorithms are examined: a Simple GA and a Hybridized GA where a local search algorithm is incorporated into the search process as a mutation operator.
On the Behavior of Input Queuing Switch Architectures
Authors: Marsan Marco Ajmone , Bianco Andrea , Giaccone Paolo , Leonardi Emilio , Neri Fabio , Filippi Enrica 
Published: September 2008

AbstractOn the Behavior of Input Queuing Switch ArchitecturesMany proposals of input queuing cell switch architectures have recently appeared in the literature. Some have found application in commercial very high speed IP routers. In this paper we discuss the pros and cons of input and output queuing switch architectures, we provide a taxonomy of scheduling algorithms for input queuing switches, and we present comparative performance results for some of the recent proposals of input queuing cell switches. Performance is measured in terms of cell loss probability, as well as average, standard deviation, and 99‐‐th quantile of the cell delay with different traffic patterns. The complexity of the algorithms, and the amount of control information to be exchanged inside the switch for their execution, are also discussed.
On the Integration of Best‐Effort and Guaranteed Performance Services
Authors: Altman Eitan , Artiges Damien , Traore Karim 
Published: September 2008

AbstractOne of the main challenges of emerging high speed telecommunication networks is the integration of services. Both ATM as well as the Internet have been evolving so as to accommodate both best‐effort type traffic (such as file transfer) as well as real time traffic requiring guaranteed performance. The co‐existence of these two service types on the same network carries important benefits such as resource sharing between service classes, and the ability of the user to easily select an appropriate service class according to requirements and preferences. These benefits depend on efficient network management and resource sharing strategies. The aim of this paper is twofold. First, we study the performance measures of both service types, as a function of the network management strategy. This study allows us at a second phase to design efficient network management schemes. This includes questions such as whether best‐effort traffic should use only bandwidth left‐over by the guaranteed performance ones, or whether (and how much) bandwidth needs to be reserved to best‐effort traffic. Another management issue that we study is the pricing. We allow for different classes of guaranteed‐performance traffic to have different priorities with respect to the rejection probabilities.
Scheduling Algorithms for Application‐Level QoS Support of Continuous Media Streams
Authors: Antoniou Zoe , Stavrakakis Ioannis 
Published: September 2008

AbstractThe Quality of Service (QoS) of real time applications is affected in a rather direct manner by the timely delivery of Application‐level Data Units (ADUs) which are typically mapped into several Network‐level Data Units (NDUs). As a consequence, it would be reasonable to associate a common deadline with all the NDUs in one ADU and develop a scheduling policy that aims to maximise the number of ADUs that are delivered by their respective deadlines. In the first part of the paper, an ADU‐based Earliest Due First (EDF) scheduling policy is investigated under periodic ADU arrival processes which are typical of continuous media streams. The proposed policy can be implemented in terms of a simple First ADU In – First ADU Out (FAI‐FAO) policy and it is shown to improve on the ADU dropping rate induced by FIFO policies of comparable complexity. In the second part of the paper, the more complex and effective Size‐Deadline Sensitive(SDS) scheduling policy is proposed and investigated under general ADU arrival processes. This policy is shown to be optimal in the sense that it maximises the number of complete ADUs scheduled for transmission at any point in time, by taking into consideration the associated diverse deadlines and the ADU sizes and combining the principles of two well known scheduling algorithms, the Earliest Due First (EDF) and the Shortest Job First (SJF). It is argued and illustrated that the proposed optimal scheduling leads in efficient actual service which under certain arrival processes is shown to be the optimal. Numerical results are presented and the induced ADU and NDU loss rates under the proposed policy are compared against those induced by the standard EDF and SJF policies.
Active Networking: A New Paradigm for Next Generation Networks?
Authors: Fan Zhong , Mehaoua Ahmed 
Published: September 2008

AbstractTraditional data networkspassivelytransport bits from one end system to another and the role of computation within such networks is extremely limited. In contrast,activenetworks allow their users to inject customized programs into network nodes. Also, switches of active networks perform customized computations on the messages flowing through them. In this paper, we discuss the active networking concepts and different approaches to the realization of active networks. We outline potential applications of this novel technology to some difficult problems in current networks and related issues. Since the term “active networking” was first proposed in 1996, there have been considerable research activities at a number of sites. The focus of this paper is therefore put on some recent developments in this area. Possible directions for future research are also identified.
Using Active Networks to Enable Universal Personal Computing
Authors: Törö Maria , Leung Victor C. M. 
Published: September 2008

AbstractActive networking is an emerging research area aimed at providing flexible and user definable services by employing switches and routers capable of executing user supplied programs and performing computations on user data in transit. This networking environment can be customized on a per user application basis. As the use of network computing applications becomes globally pervasive, users will demand new services which allow network access by nomadic users not only using their own portable computers, but using also any locally available networked computers or workstations, while providing each user with a personalized computing environment regardless of access location or computing equipment. This form of service, called universal personal computing, is also an emerging research area. In this paper, we review the capabilities of active networks as proposed in recent papers, and discuss the issues of implementing universal personal computing. By examining how these issues are addressed by active networks, we propose that active networks present an excellent platform for realizing universal personal computing service.
A new OFDM‐CDMA Uplink Concept withM‐ary Orthogonal Modulation
Authors: Dekorsy Armin , Kammeyer Karl‐Dirk 
Published: September 2008

AbstractThis paper proposes the application ofM‐ary orthogonal Walsh modulation for an OFDM‐CDMA uplink transmission. Beside the examination of general system properties, it is shown that decision‐directed phase estimation represents a channel estimation concept suitable for the new system. The Walsh modulation can also be interpreted as a linear block code with low decoding complexity, and the paper concerns the serial concatenation of convolutional codes (CC) with Walsh modulation. New aspects arise since the CC mainly operates in time domain, and the Walsh modulation is merely arranged in frequency domain. In this context, we derive the bit specific reliability information for maximum likelihood (ML) soft decoding of the CC and discuss the trade‐off between coding and spreading in case of sufficient and non‐sufficient frequency interleaving. Throughout the discussions, the results are always compared with BPSK modulation performance, and it can clearly be demonstrated thatM‐ary Walsh modulation significantly outperforms BPSK modulation in all aspects considered in this work.
Estimation of Point‐to‐Point Traffic in Circuit‐Switched Networks
Authors: Buttò Milena , Conversi Pietro Giulio , Naldi Maurizio 
Published: September 2008

AbstractThe paper addresses the problem of estimating the traffic demand between any pair of nodes in a circuit‐switched network on the basis of trunk group measurements (carried load and blocking probability on a link) and the routing plan. Two methods – a closed form one based on the use of the pseudo‐inverse matrix and an iterative one – are examined in network scenarios of varied size and connectivity under different congestion levels. In addition, a criterion based on a Bayesian approach is proposed for initializing the iterative method. It is shown that the iterative method is affected by lower estimation errors than the pseudo‐inverse method, and that the iterative method's performance is further enhanced by the employment of the Bayesian initialization criterion. Some tentative relationships are provided between the estimation accuracy and the network size and connectivity. The improvement in the estimation accuracy is accompanied by an even more pronounced reduction in the computational load. The use of the iterative method with Bayesian initialization requires in fact running times even two orders of magnitude lower than those needed by the pseudo‐inverse method, the gap being larger the larger the network and the higher the connectivity.
Letter Computation of Constrained Multicast Trees Using a Genetic Algorithm
Authors: Sun Quan , Langendoerfer Horst 
Published: September 2008

AbstractThis paper shows that the genetic algorithm can be used to solve the delay‐constrained least‐cost least‐inter‐destination‐delay‐variation multicast problem efficiently. The proposed genetic algorithm performs well when the number of destination nodes is small relative to the size of the network.
Survey of Architectures and Performance of ATM Switches Based on Deflection Routing
Authors: Pattavina Achille 
Published: September 2008

AbstractATM switch architectures based on deflection routing are here examined, described in terms of a general switch model and compared with regards to their internal operations. Their common feature is the availability of multiple I/O paths through a multistage unbuffered interconnection network where conflicts for the same interstage link are dealt with by deflecting packets onto the wrong path. The main engineering parameter of the architecture, that is the number of network stages that provides a given packet loss performance is studied in depth. In particular it is found that basically all the examined architectures have a complexity on the order ofNlog2Nin the range of switch size of usual interest. Furthermore it has been possible to rank the architectures with comparable complexity based on the loss performance they provide. The Shuffleout switch turns out to behave better than other architectures previously known as providing an optimal performance.
Polymorphic Control for Cost‐Effective Design of Optical Networks
Authors: Chunming Qiao , Yousong Mei , Myungsik Yoo , Xijun Zhang 
Published: September 2008

AbstractA WDM optical layer can provide differentiated services to various upper layer protocols by forming many virtual optical networks (VONs). Polymorphic control of an optical layer in the form of On‐demand‐reconfiguration in some VONs and Self‐reconfiguration in other VONs is proposed. The former is suitable for bursty traffic and short‐lived connections, and the latter is for steady traffic and long‐lived connections. In respect to On‐demand‐reconfiguration, efficient distributed wavelength reservation protocols, and in particular optical burst switching (OBS) protocols supporting bursty traffic (eg. Internet traffic) are described. In respect to Self‐reconfiguration, optimal algorithms to schedule all‐to‐all personalized communications (AAPC) in WDM rings and its extensions are described.