bluuebunny/crossref_metadata_2025_split huggingface dataset:
Maximizing Multicast Throughput in WDM Networks with Tuning Latencies Using the Virtual Receiver Concept
Authors: Ortiz Zeydy , Rouskas George N. , Perros Harry G. 
Published: September 2008

AbstractWe consider the problem of supporting multipoint communication at the MAC layer of broadcast WDM networks. We first introduce themidticcut rhroughprrt asthe performance measure of interest and we show that it depends on two measures that have previously been considered in isolation, namely, the efficient use of channel bandwidth and wavelength throughput. We then present a new technique for the transmission of multicast packets based on the concept of aLzirninlreceiver, a set of physical receivers which behave identically in terms of tuning. We also demonstrate that the number of virtual receivers naturally captures the performance of the system in terms of multicast throughput. Consequently, we focus on the problem of optimally selecting the virtual receivers to maximize multicast throughput, and we prove that it is Ji'P‐complete. Finally, we present four heuristics of varying degree of complexity for obtaining a set of virtuat receivers that provide near‐optimal performance in terms of multicast throughput.
Single‐Layer Optical Platform Based on WDM/TDM Multiple Access for Large‐Scale “Switchless” Networks
Authors: Caponio Nunzio Paolo , Hill Alan Michael , Neri Fabio , Sabella Roberto 
Published: September 2008

AbstractThe European Union ACTS project SONATA will define and demonstrate a cswitchlessn all‐optical network to provide a future single‐layer, advanced transport architecture on a national scale. The single‐hop, shared‐access network employs time and wavelength agility (a WDMA/TDMA protocol), using fast tunable transmitters and receivers to route individual customer connections as well as bandwidth pipes through a single wavelength router (suitably replicated for resilience). No electronic switching nodes or cross‐connects (telephony, IP, ATM, SDH) are required within the transport network, nor optical cross‐connects (save the wavelength routing node), thus providing major transport architecture simplifications and hardware reductions. The network is scalable to 200 Tbit/s throughput over 1, 000 krn, connecting 20 million terminals operating at 622 Mbit/s over 50.000‐way split c<hyperPONss, by means of 800 WDM channels with 0.05 nm channel spacing (6.25 GHz). Details of network dimensioning, physical layer modeling and network control issues are presented.
All‐Optical WDM Cross‐Connect Meshed‐Ring Communications Networks
Authors: Rubin Izhak , Ling Jing 
Published: September 2008

AbstractWe introduce a meshed ring communications network which employs cross‐connect switches. The crossconnect switches can be implemented as wavelength routers resulting in WDM networks, or as ATM Virtual Path (VP) switches leading to ATM compatible network systems. We show in the paper that this network architecture results in a significant increase in throughput performance in comparison with (SDHISONET) ring networks. For a certain class of meshed rings, under a uniform traffic matrix, we derive the optimal topology which achieves maximum throughput efficiency. Using such a topology, we obtain upper and lower bounds on the number of wavelengths required to achieve that efficiency level. The network is divided into (overlapping) communities of nodes. Each community is assigned a wavelength and a subnetwork (identified as a wavelength graph). Each pair of nodes in a community can communicate across the associated wavelength graph. Wavelength graphs (subnets) are constructed to demonstrate the implementation of the routing scheme using the number of wavelengths that is equal to the derived upper bound. For practical implementation reasons, we investigate the performance of networks which employ a reduced number of wavelengths. We show that by modifying the topological layout of the meshed ring network, we can reduce substantially the number of required wavelengths, while incurring just a modest reduction in throughput efficiency.
Performance of WDM Rings with Partial and Sparse Wavelength Conversion under General Dynamic Traffic
Authors: Maier Guido , Scappini Mauro , Martinelli Mario , Pattavina Achille 
Published: September 2008

AbstractDynamic wavelength assignment in a WDM all‐optical network with partial and sparse wavelength conversion is discussed in this paper. The performance of unidirectional and bidirectional ring networks in terms of blocking probability, conversion gain and fairness is evaluated under various types of offered traffic patterns. Smooth and peaked patterns have been considered in addition to the classical Poisson traffic type. We show how the partial use of wavelength converters having a limited conversion capability affects the blocking performance of connections and, more importantly in terms of network fairness, its dependence on the source‐destination distance.
Measuring the Survivability of a Network: Connectivity and Rest‐Connectivity
Authors: Duque‐Anton Manuel , Bruyaux Frederic , Semal Pierre 
Published: September 2008

AbstractWhen evaluating the survivability performance of a communication network, it is important to detect whether the graph is connected, whether there are separation nodes and separation pairs. The algorithms [1] and [2] developed by Tar‐jan and Hopcroft are the adequate tools for this purpose. They are able to determine the bi‐ and triconnected components of a graph in o (N+E) where N is the number of nodes and E the number of edges of the graph. Practically however, the decomposition of the graph is a step only in the evaluation of the connectivity performance of a graph. Indeed, when a separation element (node or pair) has been detected, it is crucial to know what are the consequences if this element fails down. For example, which precise parts of the graph are disconnected or more simply how large are the parts which are separated by this element? The paper introduces the notion of rest‐connectivity. Basically, for each separation element, the rest‐connectivity value is defined as the number of node pairs which got disconnected by the failure of that separation element. In this paper, algorithms [1] and [2] are enhanced in order to determine the rest‐connectivity values for all separation nodes and pairs of a graph while keeping the complexity in o(N+E).
Analysis of a Dual‐Rate Transmission Scheme for Gaussian Broadcast Channels
Authors: Sajadieh Masoud , Kschischang Frank R. , Leon‐Garcia Alberto 
Published: September 2008

AbstractIn a broadcast channel, a single transmitter communicates to receivers with different channel capacities, a typical example of which is the over‐the‐air television broadcasting. A natural question that arises is evaluation of the optimal information transfer rate in such an environment. For the two‐receiver case, we examine various transmission scenarios in this environment and focus on the theoretically optimal superposition scheme, where the information intended for the better channel is superimposed on the portion of information common to both receivers. As a result, a basic grade of service is maintained throughout the entire coverage area in addition to a higher quality service offered to the receivers with better reception conditions. Using end‐to‐end distortion and coverage channel signal‐to‐noise ratio threshold measures, three specific embedded signaling modes are introduced. We demonstrate that a generalized embedding scheme provides a practical trade‐off between distortion and coverage radius. The scheme is also formulated in terms of an optimization problem, seeking the best embedding factor for a given application. To verify the theoretical results, we idealize a dual rate transmission system over a Gaussian broadcast channel, in which receivers are distributed according to a circularly symmetric exponential pdf. The numerical results indicate that this model offers a higher per capita data rate comparing to the conventional single rate transmission systems. Application of this multirate broadcast holds promise for multiresolution transmission of digital audio and high definition television.
Exact Error Probability for Slow Frequency Hopping
Authors: Györfi László , Jordán Árpád , Vajda István 
Published: September 2008

AbstractIn this paper a frequency hopping multiple access packet communication network was considered. The channel was assumed to be slotted and frame synchronous. Reed‐Solomon codes were used both for protocol sequences and forward error correction. The exact probability of decoding error is given. A useful Gaussian approximation was computed, which led to a simple design of the system's parameters.
Experiences from the Implementation and Use of Multimedia Synchronization Mechanisms
Authors: Bozios Theodoros H. , Pronios Nikos B. , Georgiapis Panagiotis 
Published: September 2008

AbstractThis paper presents experiences from the implementation of Multimedia Synchronization Mechanisms related to the support of the many‐to‐one inter‐media synchronization and describes the proposed Synchronization Architecture and its Design Objectives. The main goal of the communication system in the proposed architecture is to maintain the asynchrony levels between the media streams belonging in a Synchronization Group between the levels specitied by the Multimcdia Application. This is achieved through appropriate Synchronization Primitives related to the management and monitoring of the synchronization. The pilper emphasizes on the implementation issues and problems, and the solutions adopted. concluding to the lirst experiences from the use of the synchronization.
On Union Bounds for Random Serially Concatenated Turbo Codes with Maximum Likelihood Decoding
Authors: Sason Igal , Shamai Shlomo 
Published: September 2008

AbstractThe input‐output weight enumeration (distribution) function of the ensemble of serially concatenated turbo codes is derived, where the ensemble is generated by a uniform choice over the interleaver and a uniform choice of the component codes from the set of time varying recursive systematic convolutional codes. The conventional union bound is employed to obtain an upper bound on the bit error probability of the ensemble of serially concatenated turbo codes for the binary‐input additive white Gaussian noise (AWGN) channel with coherent detection OF antipodal signals and maximum likelihood decoding. The influence of the interleaver lengthNand the memory length of the component codesinon the ensemble performance is investigated and compared with relevant results for parallel concatenated multiple‐turbo codes.
Performance Analysis and Estimation of Call Admission Control Parameters in Wireless Integrated Voice and Data Networks
Authors: El‐Hadidi Mahmoud T. , Elsayed Khaled M. , Abdallah Mohamed M. 
Published: September 2008

AbstractWe propose an admission control policy for wireless multimedia networks that is based on the well known threshold‐based guard channel method. The new scheme deals with two different types of traffic classes; namely: voice and data. We assume two different thresholds, one for each traffic class. In addition. we propose to buffer the handoff data calls if no free channels are available rather than rejecting them. For handoff voice calls, we propose two methods. namely: a blocking method and a preemptive method. For the blockins method, we reject the handoff voice calls it no channels are available. For the precmptive method, an ongoing data call can be buffered and its channel allocated to the handoff voice call. We study the effect of the thresholds. buffer size and the application of the proposed methods on call blocking probabilities. It is shown that the new call blocking probabilities are only affected by the threshold values. Meanwhile, the data handoff blocking probability exhibited grcat improvement. For handoff voice calls, when the blocking method is applied. the blocking probability value increases slightly with the increase of buffer size. Meanwhile. for the preemptive method, the handoff voice call blocking probability significantly decreases as the buffer size increases. Based on these results. we develop an algorithm that uses the proposed policy to estimate the appropriate thresholds and buffer six which meet the required call blocking probabilities for each traffic type.
Multicanier Modulation with Multistage Encoding/Decoding for a Nakagami Fading Channels
Authors: Goldfeld Lev , Wulich Dov 
Published: September 2008

AbstractThe Multi Carrier Modulation (MCM) system with a multistage encoding/decoding scheme based on repetition and erasures‐correcting decoding of block codes applied for a Nakagami fading channel is considered. Bit Error Rate (BER) as a function of Signal‐to‐Noise Ratio (SNR) has been found to agree well with the simulated results. It is shown that for low SNR the proposed system has a lower BER than both the MCM with Forward Error Correction (FEC) and MCM with optimal diversity reception and FEC.
Each Carrier Transmission Power Control with Antenna Carrier Diversity for OFDMDS‐CDMA System
Authors: Jarot Sigit Puspito Wigati , Nakagawa Masao 
Published: September 2008

AbstractIn OFDM‐DS/CDMA system, frequency distortion caused by multipath propagation occurs at different frequencies in the bandwidth and generally affects selected subcarriers within the larger bandwidth. It has been investigated that each carrier transmission power control is effective to compensate for subchannel variation due to multipath, by assigning different transmission power level to different subcarriers based on the attenuation level suffered by them. The effectiveness of power control is mainly affected by the accuracy of the transmission power adjustment at the transmitter. As a matter of fact, however, the dynamic range of transmission power is very limited, due to the restriction on power consumption of a mobile station (transmitter side of reverse link). When a subcarrier is subjected to strong fading, power control is not able to compensate for channel attenuation by transmitting signals with large power, and this condition is very potential to degrade system performance. In this paper, we propose to combine each carrier transmission power control with antenna‐carrier diversity reception to lighten the burden imposed on power control. This system allows the base station (receiver side) to select the best combination among the carriers and antennas after receiving signals from mobile station (transmitter side), thus power control only compensates for smaller attenuation level. System performance is evaluated in terms of Bit Error Rate (BER) performance as a function of Doppler frequency, number of users, number of branches, updating period and dynamic range. The result of computer simulations clearly show that the proposed system reduces significantly the burden imposed on power control.
Transformation Methods, Coding and Equalization for Time‐ and Frequency‐Selective Channels
Authors: Reinhardt Markus , Ecle Jochem , Lindner JÜRcen 
Published: September 2008

AbstractA method to generate transmit signal sets is proposed which are especially suited for transmission over Rayleigh fading channels. It is shown that this method in combination with a suitable iterative receive algorithm allows the asymptotical transformation of a Rayleigh channel into a set of parallel additive white gaussian noise (AWGN) subchannels. Therefore, coding methods designed for the AWGN channel are now applicable also to Rayleigh channels resulting in a coding gain that is separable into the known AWGN coding gain and an additional diversity gain attributable to the orthonormal transform.Starting from this result, the method is extended to a transmission over frequency and/or time‐selective channels. This leads to an extension of the recently introduced multicamer code division multiplexing (MC‐CDM) scheme. A unified transmission model is derived which allows the application of the iterative reception algorithm also in the latter case and to transform time‐ and frequency‐selective channels under certain assumptions asymptotically into a set of parallel AWGN subchannels. The performance of these transformation methods for an uncoded scheme and together with high rate trellis codes designed for the AWGN channel is investigated and compared to the matched filter bound (MFB). For the calculation of the MFB for channels with a separable time‐variant transfer function a method is introduced that significantly reduces the complexity of computation.
Randomized OFDM for Multi‐Cell Environments
Authors: Ping Li 
Published: September 2008

AbstractThis paper is concerned with a randomized OFDM (R‐OFDM) scheme. The basic principle is to apply a scrambling operation to several OFDM frames. With a proper design strategy, the scrambling operation will not affect intra‐cell orthogonality of OFDM (even considering multi‐path effect), For signals from different cells, mutually random scramblings are used to reduce their correlation. This alleviates the worst case inter‐cell interference problem. R‐OFDM combines some advantages of both OFDM and CDMA, namely, intra‐cell interference avoidance, cross‐cell interference mitigation as well as simple receiver structure.
Analysis of Doppler Spread Perturbations in OFDM(A) Systems
Authors: Robertson Patrick , Kaiser Stefan 
Published: September 2008

AbstractWe analyze the effects of Doppler spread in mobile channels on Orthogonal Frequency Division Multiplex (OFDM) systems. This is important, since channel variations during one OFDM symbol cause Inter Sub‐carrier Interference (ICI) in OFDM systems, which degrades the performance, since ICI can be seen as additional near‐Gaussian noise. The analysis is presented and closed‐form results are given for numerous important practical Doppler spread encountered in mobile channels and applications such as mobile reception of DVB‐T. We also show that for the case of asymmetrical Doppler spreads, the frequency correction of the receiver can be adjusted so as to minimize the ICI. To extend our work to OFDM(A) mobile radio systems where many users' contributions to the ICI overlap, we have introduced the concept of an equivalent single‐user which causes the total ICI, in order to use the same analytical framework, and compared the uplink and downlink cases. Simulation results confirm our analysis and show the importance of the analytical tool to perform realistic system analysis without having to resort to time consuming time‐domain simulations.
GSn: A new service type for integrated services on the internet
Authors: Gregori Enrico , Marcantonio Riccardo , Potorti Francesco 
Published: September 2008

AbstractNetwork services with deterministic guarantees are based on a worst—case description of user—generated traffic. When designing a policing and scheduling algorithm for guaranteed services on the Internet, accuracy of description of the traffic profile has to be traded with simplicity of implementation. The result of this trade off is often expressed as the number of token buckets required by the service along with the choice of their parameters. The GS type of service proposed by the IETF uses two token buckets both for characterizing the traffic and for policing it. The choice of using only two token buckets is primarily driven by policing costs. In this paper we propose a method that allows the number of token buckets used for characterizing the traffic to be greater than what is actually needed to police it. This means we can obtain an accurate profile of the traffic while keeping policing simple. The method consists of computing a profile of the traffic which involves a number of token buckets of the order of ten, and then doing the policing using only the first token bucket, plus another one which is chosen depending on the delay requirements of the receivers. This paper shows that with this simple enhancement we obtain a guaranteed service whose performance closely approaches the theoretical limits of services with deterministic guarantees.
Hybrid ARQ and optimal signal—to—interference ratio assignment for high—quality data transmission in DS—CDMA
Authors: Sun Songsong , Krzymien Witold A. 
Published: September 2008

AbstractCombined error correction and detection techniques, or hybrid automatic—repeat—request (ARQ) schemes with negative acknowledgment are considered for highly reliable reverse link data transmission in direct sequence code division multiple access (DS—CDMA) personal communication systems. The proposed selective repeat hybrid ARQ scheme employs an inner convolutional code for error correction and an outer shortened BCH code for error detection. Each negative acknowledgment message contains all packet sequence numbers that have been detected in error, and it is both error—correction and error—detection encoded. Accepted packet error rate and throughput are derived as a function of the error correction encoded frame error rate. An optimum signal—to—interference ratio (SIR) assignment maximizing the system's capacity is also found. A comprehensive simulation is conducted to evaluate performance of the data transmission system. Analysis and simulations show that by applying the proposed type I hybrid ARQ scheme with properly selected system parameters, virtually error free and highly efficient data transmission in CDMA personal communication systems is possible.
hing reed—solomon codes with 4—DPSK block detectors
Authors: Guarco Gianni , Visintin Monica , Elia Michele 
Published: September 2008

AbstractTransmission of 4—DPSK signals over an additive white Gaussian noise channel with an unknown phase rotation is considered, together with block detection [1] and Reed—Solomon encoding. The combination of the block detection's length and RS code parameters is analyzed.
Outage probability analysis for a nakagami signal in L nakagami interferers
Authors: Karagiannidis George , Georgopoulos Chris , Kotsopoulos Stavros 
Published: September 2008

AbstractOutage analysis is one of the primary objectives in the design and operation of the 3rd Generation (3G) micro— and pico— cellular mobile radio systems in order to increase spectrum efficiency and to control the Quality of Service (QoS) and Grade of Service (GoS) demands. This paper presents an alternative direct formulation of the outage probability for Nakagami fading channels in the presence of multiple L Nakagami interferers with arbitrary parameters. This formulation can be used with and—without a constraint of a minimum signal power. Computer simulation results are also presented to illustrate the proposed formulation.
Error resilient transmission of H. 263 video for mobile communications
Authors: Abrardo Andrea , Barni Mauro , Garzelli Andrea , Marotta Domenico 
Published: September 2008

AbstractAutomatic Repeat Request (ARQ) strategies reduce error propagation in low bitrate video transmission. However, retransmission of corrupted data introduces delay which may be critical in some practical applications. In such cases, only a FEC strategy is feasible at the expense of a significant increase of the overall transmission bit rate. In this paper, a strategy is proposed which instead of protecting the whole H. 263 video stream, uses all the redundancy to protect the most important parts of the bit stream, i. e. GOB start codes. More specifically, the 22—bit—long start code used in the H. 263 standard is replaced with longer Gold sequences which ensure a higher protection against noise. A different sequence is used for each GOB so that additional information can be obtained which can be used to improve the quality of the decoded sequence. The new technique is derived by assuming a slow—fading channel such as those encountered in pedestrian applications. Simulation results prove the effectiveness of the proposed technique with respect to classical FEC schemes in terms of PSNR and overall bit rate.