bluuebunny/crossref_metadata_2025_split huggingface dataset:
Subspace‐based tracking of multipath channel parameters for CDMA systems
Authors: Sengupta Chaitali , Cavallaro Joseph R. , Aazhang Behnaam 
Published: September 2008

AbstractIn this paper, we evaluate several issues in the application of subspace‐based methods to tracking channel parameters in Code Division Multiple Access (CDMA) communication systems, in the presence of multipath fading. We focus on two aspects of the problem – the performance of Singular Value Decomposition (SVD) based schemes while tracking the time variations in the signal subspace, due to fading, and, the performance tradeoff involved in using several complexity reducing approximate schemes. The performance benefits to be obtained from application of subspace‐based methods to channel estimation has been well studied. The aim of this work is to lay the groundwork for real time implementation of this computationally complex problem.
Comments on “Orthogonal multiple carrier data transmission”
Authors: Fliege N. J. , Vangelista Lorenzo , Laurenti Nicola 
Published: September 2008

AbstractIn a paper from 1992, Fliege introduced a novel multicarrier modulation scheme claiming to obtain an implementation that is computationally more efficient and has a simpler filter bank structure with respect to those previously presented in the literature. Being understood the correctness and valuability of the ideas expressed in that paper, nevertheless we would like to point out that an implementation with the same computational complexity had already been presented by Hirosaki in 1981, and that the optimization of the filter bank structure is based on an incorrect step.
Effects of Multiple Node Crossing on ATM Traffic Performance
Authors: Bianchi Giuseppe , Melen Riccardo 
Published: September 2008

AbstractIt is commonly recognized that traffic statistics change when a stream of ATM cells crosses several network nodes. In particular, some cells may experience a shorter delay than the previous ones, and thus the peak rate of the traffic stream may increase. In order to control this “cell clumping” effect, on one side spacing techniques have been proposed to restore the original peak rate of the sources at the outlets of each network node, while on the other side bounds to keep into account the peak rate increase have been suggested. Although some contributes have evaluated the effects of multiple node crossing on the distribution of the cell interarrival time, little attention has been paid to the effect of these modifications in terms of cell loss probability. Scope of this paper is to show, by adopting a realistic simulation model, that multiple node crossing produces a negligible effect on cell loss probability, when the admitted traffic is suitably regulated by a connection admission control rule. Moreover, a notable result is that, in the case of large buffers at the network nodes and traffic loads well over the limits imposed by the CAC rule, the per node cell loss probability eventually reduces as network nodes are crossed.
On Coded and Interleaved Noncoherent Multiple Symbol Detected MPSK
Authors: Peleg Michael , Shitz Shlomo Shamai 
Published: September 2008

AbstractThe performance of multiple symbol noncoherent detection of MPSK combined with coding and interleaving is examined in terms of the cut‐off rate bound. It is shown that, within this approach, inner modulation coding improves on standard DPSK when both are combined with an external error correcting code, such as the industry standard,K= 7R= 1/2 convolutional code. Some modulation codes over BPSK and QPSK are examined and a reduced complexity decoder is presented. The results and conclusions are verified by some simulations.
Load Profiling Based Routing for Guaranteed Bandwidth Flows
Authors: Matta Ibrahim , Bestavros Azer , Krunz Marwan 
Published: September 2008

AbstractTo support the stringent Quality of Service (QoS) requirements of real‐time (e.g. audio/video) applications in integrated services networks, several routing algorithms that allow for the reservation of the needed bandwidth over a Virtual Circuit (VC), established on one of several candidate routes, have been proposed. Traditionally, such routing is done using the least‐loaded concept, and thus results in balancing the load across the set of candidate routes. In this paper, we propose the use ofload profilingas an attractive alternative to load balancing for routing guaranteed bandwidth VCs (flows). Load profiling techniques allow the distribution of “available” bandwidth across a set of candidate routes to match the characteristics of incoming VC QoS requests. We thoroughly characterize the performance of VC routing using load profiling and contrast it to routing using load balancing and load packing. We do so both analytically and via extensive simulations of multi‐class traffic routing in Virtual Path (VP) based networks. Our findings show that for routing guaranteed bandwidth flows in VP networks, load profiling is desirable as it reduces VP bandwidth fragmentation, which increases the likelihood of accepting new VC requests. This fragmentation could be particularly harmful when the granularity of VC requests is large. Typically, this occurs when a common VC is established to carry theaggregatetraffic flow of many high‐bandwidth real‐time sources. For VP‐based networks, our simulation results show that our load‐profiling VC routing scheme performs better or as well as the traditional load‐balancing VC routing in terms of revenue under both skewed and uniform workloads. Furthermore, load‐profiling routing improves routing fairness by proactively increasing the chances of admitting high‐bandwidth Hows.
Optimal Routing for Dynamic Multipoint Connection
Authors: Chakraborty Debasish , Shiratori Norio , Chakraborty Goutam , Pornavalai Chotipat 
Published: September 2008

AbstractMultimedia applications are becoming increasingly important as networks are now capable to carry continuous media traffic, such as voice and video, to the end user. Most of the multimedia applications need multicast support too. In dynamic multicasting, destination nodes can join and leave the group during the communication period. Total or partial rerouting can optimize the tree cost to some extent. But rerouting for optimization is complex as cell‐ordering at ATM switches has to be preserved. Optimum Steiner tree is NP‐complete and therefore the present problem too. We propose a heuristic centralized routing algorithm, which optimize the total cost of the Steiner tree over the whole session period, where information about the joining and leaving of participants are available, at the time s/he actually joins. With this algorithm, the average hop‐length from source to destination has also reduced considerably. The efficiency of our algorithm and comparison with other proposed algorithms is shown by various simulation results.
On‐Line Learning and Dynamic Capacity Allocation in the Traffic Management of Integrated Services Networks
Authors: Burrell Anthony T. , Papantoni‐Kazakos P. 
Published: September 2008

AbstractA Traffic Monitoring Algorithm (TMA) is utilized to allocate channel capacities dynamically to heterogeneous traffics with time‐varying characteristics. The threshold parameters that characterize the operational characteristics of the TMA control the overall system performance, including traffic rejection rates and wasted capacity rates. In this paper an on‐line learning algorithm is introduced, to dynamically adapt the threshold parameters of the TMA for attaining a prespecified upper bound on the traffic rejection rate, at minimal cost in wasted capacity rate. The learning algorithm is analyzed and evaluated to expose its superior convergence characteristics.
A Self‐Adaptive Load Balanced Internet Multicast Routing Protocol
Authors: Lin Jhyda , Chang Ruay‐Shiung 
Published: September 2008

AbstractThe prevailing Internet has brought many novel network applications. These applications often involve the interactions among multiple members in a single session. For example, the images and voices of the lecturer in distance learning must be transmitted to multiple destinations at the same time on demand. The status and opinions of any participant should also be transmitted to each other in a video conferencing for the interactivity of conversations. Without suitable protocol supports from the underlying networks, these applications may be costly and infeasible. One of the important protocol supports is the capability of multicasting, sending a single data packet to a set of receivers that are members of a multicast group. In the past, there are four well‐known Internet multicast routing protocols: DVMRP (Distance Vector Multicast Routing Protocol), MOSPF (Multicast extensions to Open Shortest Path First), CBT (Core‐Based Tree), and PIM (Protocol Independent Multicast). In this paper, based on PIM, we propose a new multicast routing protocol called SEAL‐PIM (SElf‐Adaptive and Load balanced PIM). The new protocol reduces the PIM message and resource overhead and balances the traffic load in the network by rearranging the links of routing and the locations of the group rendezvous points to adapt to the current distribution of group members. Finally, simulations are done to compare our algorithm with the original PIM scheme. The results indicate that the performance improvement is good.
Pricing Framework for a Differential Services Internet
Authors: Borella Michael S. , Upadhyay Vandana , Sidhu Ikhlaq 
Published: September 2008

AbstractA number of recent proposals and proposed standards have addressed adding differential services to the Internet. Although their details and tentative implementations differ, most are recommending what essentially amounts to multiple levels of best‐effort service. In this paper, we survey recent differential services and pricing proposals and introduce a pricing framework for a differentiated‐services network that focuses on simplicity, flexibility, and ease of implementation. In particular, our model can be used in the current heterogeneous Internet without major restructuring. We focus on flat‐rate, per‐time and usage‐based pricing, where users can change their service level on an ad‐hoc basis. We also show that a sender‐pays model with back‐charging is simple to implement and can be effective even in complicated transactions, such as multicasting. Our approach is different from many previous proposals and consciously integrates differential services and pricing with implementation as the immediate goal. Finally, we outline future areas of research including ISP support for pricing, the dynamics of service quality and pricing in a differentiated Internet, and the latest trends and directions of QoS deployment and standardization.
MC‐CDMA in the Context of General Multiuser/ Multisubchannel Transmission Methods
Authors: Lindner Jürgen 
Published: September 2008

AbstractMC‐CDMA is considered in the context of more general multiuser/multisubchannel transmission systems. Those systems understand the transmission task for all users as an integrated whole and they allow an easy understanding of the advantages and disadvantages of MC‐CDMA in comparison with alternative methods. Multiple antennas are also included. An appropriate vector‐valued transmission model is explained and then special the cases OFDM‐OFDMA and MC‐CDMA are considered. Examples are discussed which demonstrate the advantages of spreading techniques in the context of OFDM‐OFDMA and the additional gain in power (or bandwidth) efficiency compared with pure OFDM‐OFDMA. Simulation results for an indoor scenario with 8 users are presented. Variants of MC‐CDMA, extensions and alternatives are also discussed.
Performance of OFDM‐CDMA with Simple Peak Power Reduction
Authors: Ochiai Hideki , Imai Hideki 
Published: September 2008

AbstractIn this paper we propose simple schemes which reduce the peak‐to‐average power ratio (PAPR) of the OFDM‐CDMA signals. The statistical behavior of the peak power in the OFDM‐CDMA signals is first examined by computer simulations, employing the two orthogonal sets of spreading sequences, namely, Walsh‐Hadamard sequences and Golay complementary sequences. It is shown that for small number of active users or uplink‐system, Golay complementary sequences yield much lower PAPR than Walsh‐Hadamard sequences, and for large number of active users, Walsh‐Hadamard sequences eventually becomes better. A simple scrambling scheme is introduced, which may result in considerable peak power reduction in the case of small number of the active users. For the downlink system, further reduction of the peak power can be achieved by a simple adaptive scheme based on the selection of the set of the spreading sequences.
Adaptive Reduced Complexity Multicarrier CDMA (MC‐CDMA) Structure for Downlink PCS
Authors: Visser Matthijs A. , Bar‐Ness Yeheskel 
Published: September 2008

AbstractConventional multiuser code division multiple access (CDMA) suffers from the well‐known near‐far problem. Both the conventional decorrelator and an adaptive separator termed bootstrap algorithm were used to mitigate this problem and obtain near‐far resistant receivers. These approaches still require the knowledge of which users are active and their respective codes. Eliminating this requirement is advantageous for downlink communication as only the desired user is of interest. Furthermore, in a multipath environment the use of the RAKE receiver adds to the complexity. A transmission method called multicarrier CDMA (MC‐CDMA) uses multiple narrowband subcarriers and, as a result, the channel is flat‐fading at each subcarrier. In this paper, a receiver for downlink MC‐CDMA is proposed that does not require the knowledge of which users are active. This is achieved by replacing the bank of matched filters of the full dimensional multiuser detector by 2 matched filters; one for the desired user and one representing all the interfering users combined in a specific way. Additionally, this significantly reduces the number of adaptively controlled weights. The performance of this system is analyzed and simulation results are obtained for the Rayleigh fading channel with and without correlation between the subcarriers.
Pseudo‐Noise Code Synchronization of Multicarrier DS‐CDMA Systems on Multipath Fading Channels Part II: Digital Code Tracking with Diversity
Authors: Sheen Wern‐Ho , Chang Ming‐Jou , Wu Cheng‐Shong 
Published: September 2008

AbstractPseudo‐noise code tracking with diversity reception is investigated for multi‐carrier direct‐sequence code division multiple access (DS‐CDMA) systems on multipath Rayleigh fading channels. The traditional noncoherent digital delay locked loop (DDLL) is analyzed under the effects of multipath fading and multiple access interference. A new decision‐directed tracking loop based on a differentially‐detected phase detector is proposed and analyzed. The new tracking loop significantly outperforms the traditional DDLL. Computer simulations have been conducted to verify our analytical results.
An Architectural Framework for Multimedia Integrated Wired‐Wireless Systems
Authors: Iera Antonio , Marano Salvatore , Molinaro Antonella 
Published: September 2008

AbstractIn the perspective of global communications, new conception Wired‐Wireless systems aim at satisfying the user expectation of high performance services and the need for flexibility in the management of disparate categories of multimedia and multi‐requirement applications. This paper proposes an enhanced protocol architecture for the effective handling of multimedia tele services in an integrated wired‐wireless environment. The features of the proposed protocol framework are pointed out with special focus on control issues. Enhanced medium access algorithms, bandwidth allocation strategies, handover, and admission control procedures are embraced in the system functionality. These functions are mapped onto a layered architecture, covering the entire protocol stack proposed for a generic UMTS radio access system. The introduced functions are described in terms of their basic algorithms, signalling messages and control channels, and involved protocol entities, both on the user and control planes of the proposed protocol framework.
Network Performance and Fault Detection in a PSTN Using Non‐Intrusive Methods
Authors: Beritelli Francesco , Casale Salvatore , Cavallaro Alfredo , Montagna Roberto 
Published: September 2008

AbstractThe paper presents a new approach for managing QoS in telecommunication systems based on Non‐Intrusive Methods for performance evaluation of a Public Switched Telephone Network. These methods use devices called INMDs (In‐service Non‐intrusive Measurement Devices), which measure a series of significant parameters for the evaluation of network performance, analysing signals of telephone calls in progress; in this way measurements are continuously performed on the network without having to interrupt the service. Previous studies have shown the advantages and limits of this measurement method in relation to the diagnostic capabilities of single INMDs without considering the possibility of coordinating the measurement information collected by several INMDs, which would make malfunctioning detection more efficient. The method proposed by the authors is based on the presence in the management network of a mesh of INMDs that can be connected by means of data services (connections). The performance of the INMD mesh has been evaluated by means of a simulation tool called COQUE (Communication Quality Evaluation), which allows estimation of the performance obtainable and a reasonable guess of the trade‐off between the costs and benefits obtainable with INMD techniques. The results obtained in a case study are interesting, as in a high percentage of cases malfunctioning is not only detected but also located. Moreover, the proposed case study indicates the possibility of programmable techniques that can further improve the performance of the method.
Letter Throughput and Delay Analysis of the Ideal Window
Authors: Aloha Stabilized , Alcober Jesus , Casares Vicente 
Published: September 2008

AbstractWe consider the problem of random access communications over a time slotted channel with feedback of infinitely multiplicity at the beginning of each collision resolution interval (CRI), i.e., users know via instantaneous feedback the number of users involved in that collision. Once this is known, the resolution algorithm (CRA) operates with binary (successful / non successful, s/ns) feedback. The analysis of this simple full feedback sensing window random access algorithm, named ideal window stabilized ALOHA, (IWSA), algorithm, provides a throughput of 0.5052 packets/slot. Its delay is also analyzed and compared with similar algorithms.
Letter FFT Based Generation of Bandlimited Gaussian Noise Variates
Authors: Beaulieu Norman C. , Tan Christopher C. 
Published: September 2008

AbstractRapid generation of time series samples of stationary, zero‐mean, correlated Gaussian noise will accelerate digital communication system simulations. In this letter, we show that a fast Fourier transform (FFT) based method is well suited to rapidly generate such noise samples. The FFT method requiresO(N) memory elements andO(Nlog2N) floating‐point operations to generate each sequence ofNvariates. Sequences that are bandlimited incur an aliasing error in the correlation function of the sequence, but for practical simulations we show this error is negligible. We quantify this error for arbitrary sampling rates and correlation functions.
Feedforward Synchronization Schemes for MSK‐Type Signals
Authors: D'Amico Antonio , D'Andrea Aldo N. , Mengali Umberto 
Published: September 2008

AbstractFeedforward algorithms are investigated for estimating carrier frequency, carrier phase and symbol timing in MSK‐type modulations. Their derivation is based on maximum likelihood criteria and leads to synchronization schemes that are suitable for full digital implementation. The operation of these algorithms is decoupled, meaning that the frequency parameter is measured first and independently of the others. Subsequently, phase and timing are computed through simple formulas. The performance of the proposed algorithms is investigated analytically and by simulation and the results are compared with Cramer‐Rao bounds. It turns out that the estimation accuracy is very close to the theoretical limits. The frequency estimation range is in the order of 20% of the symbol rate for MSK and 10% for GMSK. A frequency estimation threshold lower that 4 dB is achieved with fairly short observation windows.
An Introduction to Generalized Concatenated Codes
Authors: Zyablov Victor , Shavgulidze Sergo , Bossert Martin 
Published: September 2008

AbstractThis paper presents an introduction to the theory of generalized concatenated codes. We consider the encoding and decoding procedures of both ordinary concatenated codes, and generalized concatenated codes where block codes are used as inner codes. We give the main parameters of these codes, and by means of examples, show that under the same conditions the latter outperforms the former with respect to minimum code distance. We also heuristically describe the generalized concatenated decoding procedure. Then we show how the generalized concatenated coding ideas can be applied to encoded memoryless modulation. Such construction is often referred to as a multilevel code in literature. We consider the multilevel codes from the standpoint of generalized concatenated codes and with the help of a simple example, show how encoding and decoding procedures can be carried out. Ordinary concatenated and generalized concatenated coding schemes are considered next, using inner convolutional codes or inner modulation with memory. With the help of examples, we analyze the distance properties of such constructions.
ATM‐Based Multimedia Communication via Satellite
Authors: Lutz Erich , Bischl Hermann , Bostič Janez , Delucchi Cecilia , Ernst Harald , Holzbock Matthias , Jahn Axel , Werner Markus 
Published: September 2008

AbstractWithin the next years, a large number of new satellite systems for broadband multimedia communications will be developed, mainly for fixed terminals, but to a lesser degree also for portable and mobile terminals. The most important systems will be based on low earth orbit (LEO) satellite constellations with inter satellite links (ISLs), and will be seamlessly integrated into the environment of terrestrial broadband networks. Since most of the terrestrial broadband networks will be based on the Asynchronous Transfer Mode ATM, it is advantageous for the satellite networks to adopt the ATM transmission scheme and implement ATM switches on board the satellites. However, compared to communication in fixed networks, satellite communication is characterised by special constraints (limited bandwidth, propagation delay, transmission errors, dynamic network topology) requiring the development of a new ATM‐based communication technology. In the paper, an ISL‐based LEO satellite network for multimedia communication will be considered. Several relevant aspects will be discussed, such as the system architecture, the system requirements, and the protocol architecture. Since the users access the satellite network via a radio interface, an error control scheme and a multiple access scheme suitable for multimedia communication must be implemented. The aspects of TDMA‐ and CDMA‐based medium access control are discussed. Further issues are ATM resource management, radio resource management, and ISL routing. Finally, methods for terminal antenna steering are addressed, and the demonstration of aeronautical multimedia communication via the ITALSAT satellite is described.
Evolution Towards Photonic Networks
Authors: Lagasse Paul , Demeester Piet , Ackaert Ann , Van Caenegem Bart , Van Parys Wim , O'Mahony Michael J. , Stubkjaer Kristian , Benoit Jacques 
Published: September 2008

AbstractThis paper is an edited version of “Roadmap towards the Optical Communication Age” published by the HORIZON project within the ACTS Photonic Domain. This paper summarises possible evolution scenarios leading to photonic access and transport networks.