By Topic

Telecommunications Symposium, 1998. ITS '98 Proceedings. SBT/IEEE International

Date 9-13 Aug. 1998

Go

Filter Results

Displaying Results 1 - 25 of 59
  • ITS/98 Proceedings-SBT/IEEE International Telecommunications Symposium [front matter]

    Page(s): i - xxiv
    Save to Project icon | Request Permissions | PDF file iconPDF (1003 KB)  
    Freely Available from IEEE
  • Author index

    Page(s): 676 - 677
    Save to Project icon | Request Permissions | PDF file iconPDF (154 KB)  
    Freely Available from IEEE
  • STIR transform-based invariant image memory design

    Page(s): 516 - 520 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1192 KB)  

    Most problems in pattern recognition arise from the translation, rotation and size-changing of the recognised pattern. One solution to this problem is the use of a class of transforms which are simultaneously invariant under shift, rotation and scaling, so called STIR invariant transforms. The algorithms are based on a general transformation where the kernel itself contains the function to be transformed. Thus the invariances are achieved by a kind of self-mapping. Preprocessing of the input signal, such as determination of the centroid or coordinate transformation, is not necessary. The paper gives the results of development work related to the design of an invariant associative image memory based on the use of a STIR invariant transform. The memory is implemented as a software package on a PC and tested with recognition of a large set of human face photographs, which are arbitrary shifted, rotated, scaled, partly covered and corrupted by noise View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Enhancing an optical access network with ADSL technology

    Page(s): 548 - 553 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    This paper gives a short overview on narrowband access networks and the need for enhancing these networks with ADSL transmission techniques. After a short introduction to ADSL, the current status of the standardization process for ADSL is reflected. A major open topic in the physical layer is ADSL over ISDN transmission. There are many other open issues for higher layers. The work of the ADSL Forum is reflected View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A coded modulation scheme for a broadcast AWGN channel

    Page(s): 458 - 461 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB)  

    This paper proposes a coded modulation scheme for transmission of two classes of information on a broadcast AWGN channel. The scheme is based on multilevel coding with a nonstandard partition of a 32-QAM constellation. The QAM constellation consists of four groups of 8-PSK subconstellations instead of 8-QAM subconstellations. This results in a constellation with reduced peak-to-average power ratio. As component codes of the multilevel construction only one binary convolutional code and a punctured version of it are used. The nonstandard partition allows parallel decoding of the component codes in a multistage decoding algorithm. The error performance of the proposed scheme is obtained. In comparison with Wei's scheme with similar parameters, the proposed scheme achieves higher coding gains for the most important class at the cost of a small degradation in performance for the less important class. Although only results for a specific constellation are presented, the design principles can be easily extended to other QAM constellations View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On the equivalence between propelinear and binary G-linear codes

    Page(s): 525 - 527 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (160 KB)  

    The main objective of this paper is to establish a relationship between propelinear codes and binary G-linear codes as defined in Costa et al., (1997). We show that every binary G-linear code is a propelinear code by showing that the group structure induced by either one of these codes is related to the semi-direct product View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Implementing a distributed Web-based management system in Java

    Page(s): 554 - 559 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    The distribution requirement of current and future networked environments has led to a shift from traditional centralized towards distributed management approaches. A distributed architecture for network management is presented The architecture implementation is based on an extensive use of emerging client/server, Web and Java technologies, the pursued objective being to promote flexibility, openness and portability View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • NetTrouble: a TTS for network management

    Page(s): 480 - 485 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (472 KB)  

    Current information systems need tools that are able to register the variety of problems that occur in the system, co-ordinating the efforts for resolution and keeping the experience gained in those efforts. These applications are traditionally called trouble ticket systems (TTS). The network management (NM) environment involves several issues not yet addressed by current systems, namely the heterogeneity of data networks, geographic dissemination (of the managed system and of the management team), the multi-organisational attribute of wide area networks (with many carriers and communication service providers between network ends), and the decomposition (both functional and hierarchical) of the associated tasks and responsibilities. This paper explains the most important results of a project developed at the University of Coimbra that involved the development of NetTrouble, a TTS designed for NM that brings out new and innovative concepts such as the use of administrative domains (useful in dealing with multi-organisational systems), the autonomic definition of co-operation policies between different organisations, a flexible administrative model (going to ticket-level detail and able to involve both local and remote human resources), and the virtual presence of tickets belonging to remote domains. The notification model of NetTrouble, another interesting feature, is also be described View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On the statistics of the Nakagami-m signal

    Page(s): 377 - 382 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (340 KB)  

    This paper proposes a fading model that leads to a formal, but simple, method to obtain the exact formula of the Nakagami-m distribution for m=n/2, n a non-zero integer number. Based on such a model the joint distribution of the envelope and its time derivative is accomplished and exact formulas for the level crossing rate (closed-form formula) and for the average fade duration are derived. Simulation curves and exact formulas are checked against each other and a perfect agreement between them is attained. Although derived for discrete values of m (m being an integer multiple of ½) there are no mathematical constraints for these expressions to be used for any real value m⩾½ View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • FLEXOS, a telecommunications management network system

    Page(s): 542 - 547 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (676 KB)  

    This paper presents an experiment with an integrated telecommunication management system construction. It refers to the development of FLEXOS, a system that accomplishes the configuration management and fault management of telecommunications networks, comprising equipment manufactured by Digitro Tecnologia Ltda. This work embraces the whole development process, from the information modeling and implementation of the Q3 agents to the management applications implementation. The analysis and modeling stages follow the principles established in the ITU-T recommendations for TMN, telecommunications management network. The management system was implemented using the Solstice Enterprise Manager management platform and the agents were developed using the Solstice TMN Agent Toolkit View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Novel robust RM-KNN filters with impulsive noise suppression for image processing

    Page(s): 656 - 661 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    We introduce novel robust filtering algorithms applicable to image processing. They are derived by use of RM-type point estimations and the restriction technique of the well-known, specifically for image processing, KNN filter. The derived RM-KNN filters effectively remove impulsive noise while edge and fine details are preserved. The proposed filters are tested on simulated images and real imaging radar data and provide excellent visual quality of the processed images and good quantitative quality in comparison with the standard median filter. Recommendations to obtain the best processing results by proper selection of derived filter parameters are given View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An authentication server in Java implementation of an encryption framework model and DES algorithm in Java

    Page(s): 627 - 631 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    The present work presents a framework model for communication channel encryption with functions similar to JCE (Java cryptography extensions) of Java, which allows any encryption algorithm to be codified and used in a simple and standard way. Through this proposed framework model, it is possible to insert cryptography in a transparent way in communication channels like conventional TCP/IP sockets. Using the proposal model, an authentication server was implemented, along with the encryption algorithm DES. The results obtained through the proposed framework show that the transparency obtained makes the development of applications using communication encryption simpler and standardized, besides decreasing the occurrence of programming errors. The authentication server implemented through the proposed framework model is used by information storage systems from CEFET-PR to ensure data transmission through the Internet. The language used was Java, because of its interoperability and portability View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Complex algorithm in frequency domain optimization using first order linear transversal filters in parallel and prefiltering in input signal

    Page(s): 448 - 453 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    This paper presents the adaptive IIR filtering with a parallel form realization in a system identification application using a prefiltering algorithm and distinct initialization for each section of the parallel filter. The frequency domain implementation and a recursive frequency sampling structure was used in computer simulation and the results present gains in convergence speed and in the stability of the adaptive filtering View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On the transmission of repeaterless 8×2.5 Gb/s over 160 km of dispersion-shifted fiber

    Page(s): 615 - 618 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (188 KB)  

    This paper reports on WDM transmission of 8 channels, 10 dBm per channel, over dispersion-shifted fiber. Experimental results show a penalty below 1 dB for all channels used. The results were obtained without extra optical components in the optical path or a special modulation scheme View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fuzzy image processing based on spatial convolution operators

    Page(s): 662 - 666 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (568 KB)  

    This paper presents a method for image processing based on a set of fuzzy inference rules. These rules generate a mapping by considering the results obtained from the convolutional operation between classic operators and a given image. The spatial convolution masks are selected due their easy implementation. Experimental results reveal some promising applications of the proposed method View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Video quality assessment using objective parameters based on image segmentation

    Page(s): 498 - 503 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (604 KB)  

    This work presents a methodology for video quality assessment using objective parameters based on image segmentation. Natural scenes are segmented into plane, edge and texture regions, and a set of objective parameters are assigned to each of these contexts. A perception-based model that predicts subjective ratings is defined by computing the relationship between objective measures and results of subjective assessment tests, applied to a set of natural scenes and MPEG-2 video codecs. In this model, the relationship between each objective parameter and the subjective impairment level is approximated by a logistic curve, resulting in an estimated impairment level for each parameter. The final result is achieved through a linear combination of estimated impairment levels, where the weight of each impairment level is proportional to its statistical reliability. The results presented show that the use of region-based objective measurements provides more accurate predictions compared to predictions based on global parameters View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Two-scale transmission of DCT-coded video over lossy packet networks

    Page(s): 510 - 515 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    This paper discusses the development and results of a simulation package for two-scale transmission of discrete cosine transform (DCT)-coded video over lossy packet networks. The considered scalability of coded video sequences is based on variations of data partitioning and requantization techniques. These variations contemplate situations in which the reference signal used in predicted (P-type) or interpolated (B-type) frames is based on the full coded signal, or alternatively, based only on the high-priority signal. Also considered are variations of data partitioning with a fixed number of spectral coefficients. The signals relating to the two scales are to be transmitted over a channel formed by a high-priority link, with no loss of cells, and a low-priority, lossy link. The results of transmission over packet networks with various levels of cell loss rate are presented and a few conclusions are drawn View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Texture smoothing and object segmentation using feature-adaptive weighted Gaussian filtering

    Page(s): 650 - 655 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1052 KB)  

    Gaussian filter kernels can be used to smooth out textures in order to obtain uniform regions for image segmentation. In so-called anisotropic diffusion techniques, the smoothing process is adapted according to the edge direction in order to preserve the edges. However, the segment borders obtained with that approach do not necessarily coincide with physical object contours, especially in the case of textured objects. A novel segmentation technique by weighted Gaussian filtering is introduced. The extraction of true object masks is performed by smoothing edges due to texture and preserving true object borders. In this process additional features like disparity or motion are taken into account. The method presented has been successfully applied in the context of object segmentation in natural scenes and object-based disparity estimation for stereoscopic applications View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Efficient echo cancellation based on an orthogonal adaptive IIR realization

    Page(s): 434 - 437 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    Adaptive IIR filters have not been widely used in many areas because the updating algorithms and suitable representations (realizations) known in the literature do not cover different particularities of each application. We discuss both the utilization of a particular realization for the adaptive IIR filter and a special structural interpretation of the Steiglitz-McBride method for updating the coefficients. The main application emphasis is oriented towards echo cancellation applications but other areas of adaptive signal processing such as postcursor filters in decision feedback equalization can be included. The particular realization proposed is based on a generalized orthonormal family of functions that has the Laguerre functions and the Kautz functions as special cases. Except for the lattice realization, that is based on the properties of Szego orthonormal polynomials, no other adaptive IIR filter realization using orthonormal characteristics seems to be extensively studied in the literature. The chosen realization has several advantages relating mainly to suitable internal (coefficients and variables) normalization and robust numerical conditioning. The Steiglitz-McBride method is discussed mainly because it can avoid the local minima problem related to direct mean squared output error minimization. In this paper, we present some theoretical results related to the properties of a special orthonormal realization, suitable for echo cancellation, when used to minimize the mean square output error with the Steiglitz-McBride algorithm View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Adaptive channel equalization using neural network

    Page(s): 438 - 441 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (244 KB)  

    This paper applies neural networks to the adaptive channel equalization of a bipolar signal passed through a dispersive channel in the presence of additive noise. The paper describes two neural networks which might be considered as adaptive equalizers. The simulation results confirm that the neural network equalizers offer a performance which exceeds that of linear structures. More specifically, this paper highlights the effects of delay order on the BER performance of nonlinear structures View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • WLL field trials in Brazil

    Page(s): 394 - 399 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (444 KB)  

    Field trials of 20 WLL systems of several technologies, developed by 13 different manufacturers, were recently hosted by 11 carrier companies of the TELEBRAS System, resulting in the largest and the most complete WLL field trials performed in the world so far. This paper presents some information about the history of these trials. The basic design and tests as well as the main results and conclusions concerning spurious emission, interference, coverage and service transparency to the users are presented. Due to the non-disclosure agreement established between TELEBRAS and the manufacturers, no results of a specific WLL product is presented, nor a comparison between them. The presentation of the results is general, at a level of detail sufficient to show the real potentiality of the WLL technology as a alternative to the wired network in the provision of high-quality telecommunications services. Additionally, the main features of the WLL technologies are presented View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A new iterative method to solve a volume integral equation

    Page(s): 410 - 414 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (244 KB)  

    A new iterative method for solving a volume integral equation is developed. The method consists of the division of the domain into subdomains, every subdomain characterized by a moment matrix that determines the field induced by the excitation. The entire solution is built by interaction among the subdomains, with the incident field as the initial excitation View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Efficient tree construction for the multicast problem

    Page(s): 632 - 637 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (604 KB)  

    A new heuristic for the Steiner minimal tree problem is presented. The method described is based on the detection of particular sets of nodes in networks, the “hot spot” sets, which are used to obtain better approximations of the optimal solutions. An algorithm is also proposed which is capable of improving the solutions obtained by classical heuristics, by means of a stirring process of the nodes in solution trees. Classical heuristics and an enumerative method are used as comparison terms in the experimental analysis which demonstrates the capability of the heuristic discussed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Service location for mobile agent systems

    Page(s): 623 - 626 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (308 KB)  

    One of the main challenges of the mobile agent technology is how to obtain a host that provides the service specified by the agent. This work proposes a service location module for a development environment for agent-based systems named GTA/AG infrastructure (GTA/agent). This module makes easier the agent programming since the service location module provides the agent's destination View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Telecommunications services management with computational reflection, using CORBA and JAVA

    Page(s): 486 - 491 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (500 KB)  

    Currently, telecommunications management systems are powerful, however, they maintain centralized and proprietary platforms, limiting in this way, the growth of these telecommunications networks. This factor generates the need for scalable and open systems, stimulating the sectors of the telecommunications area to seek for solutions to problems in distributed, heterogeneous and totally scalable environments. The recent advances in the area of distributed objects has created many positive expectations for the development of client/server systems which use, as if they were local, resources available through the network. The objective of this work consists of the experimental evaluation of the potential of the main CORBA services in conjunction with the Java language, through the necessary requirements for the main functionalities proposed by the TMN architecture. For the implementation of telecommunication services with reusability of code we use computational reflection with meta-classes substituting the manager and classes substituting the agents View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.