bluuebunny/crossref_metadata_2025_split huggingface dataset:
Letter: A Simple Multilevel Block‐Coding Scheme with π/4‐QPSK Properties
Authors: Henkel Werner , Litzenburger Manfred 
Published: September 2008

AbstractA multilevel block‐coded QPSK with a similar envelope and trajectories as π/4‐QPSK is proposed. Additionally, it is rotationally invariant and, thus, allows coherent detection. The asymptotic coding gain is 3 dB, whereas the effective coding gain at a bit‐error probability of 10−6 is around 2 dB against uncoded π/4‐QPSK. The corresponding trellis of a full maximum‐likelihood decoder has only four states, which results in a very low complexity.
On QAM Speech Transmission Schemes for Microcellular Mobile PCNs
Authors: Hanzo Lajos , Webb William , Steele Raymond , Salami Redwan A. 
Published: September 2008

AbstractOn the way towards third generation personal communication networks (PCN) the deployment of 16‐level quadrature amplitude modulation (QAM) schemes is investigated via flat microcellular Rayleigh‐fading mobile radio channels having mild co‐channel interference with and without diversity. Our proposed differentially coded non‐coherent 16‐QAM scheme requires no pilot symbol assistance, no automatic gain control (AGO and no carrier recovery. High speech quality associated with a mean opinion score of about four (MOS= 4.0) is ensured at a signalling rate of 6.2 kBd for channel signal to noise ratios (SNR) above 20 ‐ 25 dB and signal to interference ratios (SIR) above 25 ‐ 30 dB by the 13.4 kbit/s medium complexity regular pulse excited (RPE) speech codec, when carefully matched twin‐class low complexity binary Bose‐Chaudhuri‐Hocquenghem (BCH) error correction coding and 16‐QAM combined with second order diversity are deployed. The overall speech delay is about 40 ms and the user bandwidth is 9.3 kHz, which allows us to accommodate 21 users in a 200 kHz channel slot.
Letter: Impact of RFI Detection in DRS Links on the Performance of Coding Schemes
Authors: Losquadro Giacinto , Michel Philippe , Elia Michele , Visintin Monica 
Published: September 2008

AbstractThis paper deals with Data Relay Satellite systems operating in the S‐band environment and using Binary Phase Shift Keying modulation with concatenated Forward Error Correction data protection. One of the major sources of their performance degradation is radar generated Radio Frequency Interference in the same band. Transmission channel performance would certainly be improved if RFI positions (called erasures) were detected and passed to the decoders. By allowing the codes to handle about twice as many erasures as errors, this information would significantly reduce the effects of RFI deterioration.A novel technique for RFI detection is developed. It is based on a bank of simple “moving windows” associated with a detection algorithm and a method for the removal of ambiguous RFI detections. The use of this erasure information in the Viterbi decoding process is then illustrated and a new rule for updating the decoding metric is proposed.The residual correlation on the errors at the Viterbi decoder output makes the outer code useless, unless a further interleaving is introduced.Extensive simulation results highlighting the good performance of the joint RFI detection and modified Viterbi decoding schemes are presented. Simulation is also used to assess the outer code behavior.
An Asymmetric Speech Coding Algorithm Using Vector Quantization and Silence Deletion
Authors: Koch Ronald C. N. , Prasad Ramjee , Bons Jan H. 
Published: September 2008

AbstractIn store‐and‐forward and multi‐media speech applications, e.g. in voice‐mail or when adding verbal comments to a document, the speech encoder can be allowed more time and higher complexity than in real‐time speech coding. Decoding however must be simple when a low‐cost terminal (e.g., a PC) is used. This kind of coding algorithm is called an asymmetric algorithm. Asymmetric algorithms exploit encoding delay to code the signal efficiently. An existing asymmetric coding algorithm is Vector Quantization (VQ). A new asymmetric algorithm is proposed, based on the coding of the time intervals between zero‐crossings (frames) using VQ and silence deletion. The algorithm takes advantage of the empirical fact that infinitely clipped speech retains its intelligibility. The algorithm has been implemented using software and its performance was evaluated.
Synchronous Digital Hierarchy Optical Metropolitan Network Ring Traffic Analysis
Authors: Owen Henry L. , Wulf‐Mathies Carston 
Published: September 2008

AbstractAs a result of the Synchronous Digital Hierarchy (SDH) standards, new network topologies are being introduced into existing networks. These new topologies include unidirectional and bidirectional rings in an environment which was previously dominated by point to point interconnections in meshed structures. Analysis of the traffic statistics of existing Plesiochronous Digital Hierarchy (PDH) metropolitan networks using various SDH network topologies is required in order to be able to determine optimal SDH network topologies. Existing bandwidth switching methodologies must be included in this analysis to determine the effects of these bandwidth routing methodologies. Several proposed hierarchical metropolitan optical transmission network architectures are examined in this paper in order to be able to determine strategies for the introduction of SDH capabilities into existing networks. An actual metropolitan network is used as a case study to evaluate traffic flow in several proposed hierarchical ring network topologies. These topologies include both unidirectional and bidirectional rings in three different hierarchical structures: a three level, a two level, and flat network hierarchies. The transmission requirements for these hierarchies with a central switching constraint are analyzed. The results indicate that existing centralized switching methodologies reduce the bandwidth carrying capacity advantage of bidirectional rings over unidirectional rings in hierarchical topologies.
Performance Evaluation of ASK Multichannel Coherent Optical Systems
Authors: Corvaja Roberto , Tomba Luciano 
Published: September 2008

AbstractIn this work we evaluate the impairments due to laser phase noise in multichannel coherent optical systems using a heterodyne ASK modulation scheme. The effects of crosstalk due to a finite value of the channel spacing are considered in a system employing a frequency division multiplexing technique. The phase noise and the frequency spacing between adjacent channels are the fundamental parameters which determine the design criteria (e.g. the bandwidth of the intermediate frequency filters) and the performance of the receiver. The accurate statistical characterization of the filtered phase noise and of the crosstalk is the key to get accurate results: to this aim the exact moments of the random processes related to the phase noise and to the crosstalk interference are used together with a Gaussian Quadrature Rule for the evaluation of the error probability.
Error‐Correction Coding for High‐Speed Optical Transmission Systems Based on the Synchronous Digital Hierarchy
Authors: Paxal V. , Jourdain P. , Karam G. 
Published: September 2008

AbstractThe quality objectives given in the CCITT recommendations concerning fiber optics transmission over the Synchronous Digital Hierarchy (SDH) network are difficult to achieve in high‐speed systems. Equipment imperfections often result in a Bit Error Rate (BER) floor above the recommended BER value of 1CH4. In this paper we propose a simple Reed Solomon (RS) coding scheme for the Synchronous Transport Module level‐1 (STM‐1) frame which leads to a substantial BER performance improvement over uncoded systems. The RS code proposed is a shortened one‐symbol‐correcting code. Experimental results obtained with a laboratory prototype are reported which show that this code reduces the BER floor by four orders of magnitude.
Non‐Linear Optical Transmission Systems
Authors: O'Mahony Michael J. 
Published: September 2008

AbstractIn recent years much research has focussed on the development of high capacity optical transmission systems for terrestrial and undersea application. The development of optical amplifier repeaters has led to the situation where multigigabit transmission is required over very large distances. In this situation the effects of fibre dispersion pose a serious limitation to performance. This paper considers the effects of fibre dispersion and discusses the technique of non‐linear propagation which has been proposed to overcome the problem. The main design equations for a soli‐ton system are presented and discussed.
Applications of Coherent Techniques to Optical Transmission: State of the Art and Perspectives
Authors: Betti Silvello , Marchis Giancarlo De , Iannone Eugenio 
Published: September 2008

AbstractThe state of the art and the perspectives of application of coherent techniques to optical‐transmission systems are discussed. After a review of the performance achieved with point‐to‐point single channel transmission systems, different frequency‐division‐multiplexed systems are analyzed for both point‐to‐point transmission and local area network applications. Attention has been devoted to possible applications of coherent optical systems in broadcast and local area networks exploiting both subcarrier and frequency division multiplexing techniques. In conclusion the potentials offered by these systems are considered relatively to space intersatellite optical links.
Future Scenarios for Telecommunications Networks
Authors: Hawker Ian , Cochrane Peter 
Published: September 2008

AbstractTo maintain the pace of progress the future development of telecoms networks should reduce the cost per connection, improve quality of service and increase network functionality and intelligence. In this paper we examine some .of the longer term network options including optical networking to create bandwidth transparency in order to reduce costs and enable new networking approaches (eg where bandwidth is traded for simpler control). We also discuss the reliability threat from the growth of ‘software mountains’ associated with increased network intelligence and functionality, and suggest self organization as a viable alternative.
Performance Calculations of Optically Preamplified IM‐DD Receivers
Authors: Gaibazzi Alberto , Ghiggino Pierpaolo , Shamir Netta 
Published: September 2008

AbstractThe performance of optically preamplified IM‐DD receivers is investigated, in terms of Sensitivity and BER, employing a statistic model which is more accurate than the customary Gaussian approximation.A comparison between the two statistics' predictions is presented.The implications of practical receivers on the performance of the system have been analysed in detail. Particular care has been taken to investigate the penalties arising from a non‐optimum threshold setting of the comparator.
Optical Fiber Buffer for High‐Performance Broadband Switching
Authors: Masetti Francesco , Gavignet‐Morin Paulette 
Published: September 2008

AbstractThis paper presents an optical buffer shift register based on a set of fiber delay lines electrically‐controlled, to provide cell storage and queueing capabilities in high‐performance broadband switches satisfying ATM service requirements. The concept of multi‐wavelength cell buffering is adopted, to realise a partially shared buffer with a storage capacity equivalent to a set of single shift registers. The final system is well‐suited for photonic switches adopting time‐ and wavelength‐division multiplexing techniques to perform the routing functions inside the switching matrix.We have demonstrated both the suitability of optical fibers as signal delay lines and the use of semiconductor optical amplifiers as gates associated to passive splitters, to realise cell buffering and time‐switching. An experimental set‐up has been implemented at 600 Mbit/s, operating without guardbands between packets. Good performances were obtained in terms of gain and speed of the whole system: the slight penalty and time shifts observed show that the system synchronisation is very good, thus capable of allowing higher operating bit‐rates.
Passive Optical Networks ‐ Deployment and Evolutionary Potential
Authors: Faulkner David , Stern Jeff , Frost Peter , Cook Andrew 
Published: September 2008

AbstractThis paper gives insight into the ways in which Passive optical networks may be economically deployed in a well‐established copper infrastructure.The telecommunications market demands service flexibility coupled with high reliability, which the copper network struggles to provide. Particularly beneficial is the fibre‐to‐the‐building approach, which is being followed in certain areas in Europe. This provides the necessary service flexibility and promises huge capacity upgrades for the future. Following initial deployments the opportunity exists to broaden the deployment throughout Europe. Ubiquitous solutions will enable the benefits of fibre to be brought to smaller and smaller customers. Beyond this, the capacity and reach of fibre can be exploited more widely ‐ restructuring the network to extend broad band services to all customers.
Bandwidth Allocation in an IBCN Queueing System with Quasirandom Input
Authors: Schlott Reinhard 
Published: September 2008

AbstractIn this paper, we present a call admission strategy for an Integrated Broadband Communication System serving two types of customers ‐ Narrowband and Broadband. Either one or both of the customer groups are assumed to have a finite number of sources (customers). The model involves a multidimensional state space, for which balance equations are derived. Since the system employs separated queues, one for each type of customer, multiple transitions can take place within the state space. Their probabilities have been derived analytically. Finally we compute the carried load and mean queue lenghts and compare these with separated one‐dimensional models. A quasi‐separation and a bandwidth‐ratio effect appears from graphs.
Decorrelators for multi‐sensor systems in CDMA networks
Authors: Kandala Srinivas , Sousa Elvino S. , Pasupathy Subbarayan 
Published: September 2008

AbstractIn this paper we consider a multi‐sensor detection problem in both additive white Gaussian noise (AWGN) and fading channels with the users using the channel based on a code division multiple access (CDMA) scheme. Several multi‐sensor detectors that have been studied previously do offer good performance; however, these detectors require the knowledge of the signal energies and these have to be estimated. Such an estimation might not be feasible in fading and time‐varying channels. We show how the linear optimal detector can then be simplified to obtain a decorrelating detector which does not require the knowledge of the users' signals. We show that this decorrelating detector performs almost as well as the linear optimal detector in an AWGN channel. We further investigate its performance in single‐path and frequency‐selective slowly fading channels. In a slowly fading channel when there is multi‐user interference, the conventional detector reaches a saturation point beyond which no improvement in performance can be obtained. We show that the performance of the decorrelating detector does not depend on the other users' energies and hence on the other users' fading characteristics. We further show that a decorrelating detector can be used to obtain a Rake type of receiver in frequency‐selective fading channels.
DS‐CDMA outage performance over a mobile satellite channel
Authors: Vojcic B. R. , Pickholtz R. L. , Milstein L. B. 
Published: September 2008

AbstractA DS CDMA satellite uplink with power control error is considered. CDMA system performance is normally interference limited, and, in an additive, white, Gaussian noise channel, with many users, sufficient processing gain, and effective power control, individual users typically experience the average performance over all users. In this case, the other users appear as the equivalent of additional Gaussian noise and each user experiences the same environment. An alternative measure of performance under fading conditions is the probability of outage. For coded signals, the fading must be averaged over all the symbols in the code word. For properly interleaved signals and i.i.d. Rayleigh fade statistics, the average must be performed over a chi‐squared variate. The probability of outage, defined as the probability that the decoded bit error rate exceeds a specified threshold, is monotonic with the probability that the chi‐squared variate is less than a specified threshold. We derive upper and lower bounds on the outage probability for soft decision decoding.
Dynamic code allocation for integrated voice and multi‐priority data traffic in CDMA networks
Authors: Geraniotis E. , Chang Y.‐W. , Yang W.‐B. 
Published: September 2008

AbstractIn the context of deriving schemes for efficient use of the spectrum by multi‐media users in direct‐sequence code‐division multiple‐access (DS/CDMA) networks we describe in this paper an optimal policy for CDMA code allocation to voice and multi‐priority data traffic We consider CDMA networks with voice traffic and two types of data traffic: high priority data traffic with the same priority as voice traffic that requires real‐time delivery and lower priority data traffic that can tolerate delay and thus can be queued. A movable boundary policy in the CDMA code domain is used for the voice and high priority data, whereas a small number of CDMA codes are reserved for the lower priority data which also utilizes any CDMA codes left unused by the other two traffic types. The optimal policy is obtained by minimizing a cost function consisting of the weighted sum of the rejection rates of voice and high priority data traffic subject to performance requirements (bit error rates or BER) on all traffic types. The queueing delay of the lower priority data traffic is also evaluated. A semi‐Markov decision process (SMDP) with guaranteed BERs for voice and data traffic is used for formulating the dynamic code assignment problem. A value‐iteration algorithm is applied to this SMDP to derive the optimal policy.
Synchronous digital hierarchy byte pointer justification versus VC‐12 payload bit justification effects
Authors: Owen Henry L. 
Published: September 2008

AbstractFour contributors to Synchronous Digital Hierarchy (SDH) network desynchronizer buffer fill variations are the justification bits in the VC‐12 payload, the irregular spacing of the data in the VC‐12 payload, the irregular spacing of the data in the SDH frame, and the pointer activity which contains byte activity as opposed to the bit activity in the VC‐12 itself. These phenomena result in a variation of the rate at which bits arrive at a desynchronizer in a SDH network. Modeling and understanding of these processes is required in order to be able to propose advanced pointer processor algorithms as well as advanced jitter reduction techniques in SDH de‐synchronizers. This paper examines the relative effects of bit justifications in VC‐12 payloads in conjunction with the corresponding byte justifications in SDH networks in order to determine the dynamics of SDH network plesiochronous desynchronizer buffers.
History of education of telecommunications engineers in italy
Authors: Stracca Giovanni B. 
Published: September 2008

AbstractThe paper analyzes the history of education of telecommunications engineers in Italian engineering, schools, the aim being to provide a stimulus to analyzing the parallel development of this education also in other European countries. It covers the time from the 19‐th century, when telegraphy and telephony were the first practical applications of scientific knowledge concerning electrical phenomena, to recent years, when a “laurea” (5 year degree course) and a “diploma universitario” or D.U. (3 year degree course) in telecommunications engineering were introduced into Italian universities. The evolution of the teaching of telecommunications engineering is compared with the parallel development of telecommunications services and of related scientific knowledge. Whereas the main Italian engineering schools introduced curricula for electrical engineering early in the 19‐th century, due to early recognition of the importance of electrical energy applications, there was some delay in the introduction of telecommunications disciplines into engineering curricula (though such applications were born before). The paper points out some reasons for this delay. Brief biographies of some important professors are given.
Performance of coherent and differential detection for trellis‐coded 8‐PSK over satellite flat rician fading channels
Authors: Gaudenzi Riccardo De , Vanghi Vieri 
Published: September 2008

AbstractTrellis‐coded 8‐PSK (TC‐8‐PSK) modulation is a power and bandwidth efficient modulation scheme which is finding increasing applications in terrestrial and satellite systems. In particular, TC‐8‐PSK is demonstrating attractive performances over die satellite mobile fading channel where it provides considerable coding gain with respect to uncoded QPSK with no bandwidth efficiency loss. In this paper die capabilities of a decision‐directed maximum‐likelihood coherent phase tracker are investigated for flat Rician fading channel. Open loop and steady‐state performances of die digital phase tracker are analytically determined and verified by means of computer simulations. By optimizing phase loop parameters in presence of Rician fading with respect to the mean time to lose lock, it is shown that, for typical satellite fading channels, die coherent decision‐directed phase tracker performs poorly. This is also true for feed forward decision‐feedback phase estimator. In these cases, the additional power loss required by differential detection of TC‐8‐PSK respect to coherent detection has been evaluated by means of computer simulations.
A study on spectral optimisation in partial response CPM signals
Authors: Campanella Matteo , Garbo Giovanni , Mamola Giovanni , Randazzo Edoardo 
Published: September 2008

AbstractAn optimisation technique for the minimisation of the effective bandwidth in partial response CPM signals is described. The minimum Euclidean distance is used as optimisation constraint because the bit error probability is a function of this parameter for high values of signal to noise ratio. The procedure has been implemented for a correlation length corresponding to two signalling intervals. The optimisation problem leads to a system of two nonlinear differential equations for the pulse shape, together with some boundary conditions. Numerical solution of the differential equations has been performed; initial conditions have been adjusted, to satisfy the boundary conditions using an iteration method based on the Newton‐Raphson algorithm. The whole procedure is based on a particular assumption about the minimising difference sequence for the minimum Euclidean distance. This assumption has been tested and the limit value of the modulation index satisfying the test is also reported.
Applications of the kohonen algorithm in vector quantization
Authors: Poggi Giovanni 
Published: September 2008

AbstractThe paper deals with the exploitation of the codebook‐ordering property of the Kohonen algorithm in vector quantization (VQ). First, the substantial equivalence between the Kohonen algorithm and the generalized‐Lloyd algorithm in terms of encoding performance for memo‐ryless VQ is established. Then, algorithms based on the use of Kohonen ordered codebooks are proposed to solve different problems in VQ such as rate reduction, progressive transmission, and channel‐error protection.