By Topic

Telecommunications Symposium, 2006 International

Date 3-6 Sept. 2006

Filter Results

Displaying Results 1 - 25 of 192
  • Optimization of wavelength assignment in an optical link considering four wave mixing using genetic algorithm

    Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (927 KB) |  | HTML iconHTML  

    This article presents a new strategy to assign wavelengths in an optical link considering the four wave mixing effect in the optical fiber, for different sizes of wavelength grids. The four wave mixing effect is taken into account by using a formulation that calculates the fiber noise figure for each wavelength. We obtain the distributions of wavelengths from a genetic algorithm, which considers the quality of service criterion based on bit error rate. We show that our strategy is capable of determining assignments of wavelength that minimizes the impact of the four wave mixing effect. We also analyze the performance of our proposed genetic algorithm. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Wavelet analysis as an information processing technique

    Page(s): 7 - 12
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (395 KB) |  | HTML iconHTML  

    A new interpretation for the wavelet analysis is reported, which can is viewed as an information processing technique. It was recently proposed that every basic wavelet could be associated with a proper probability density, allowing defining the entropy of a wavelet. Introducing now the concept of wavelet mutual information between a signal and an analysing wavelet fulfils the foundations of a wavelet information theory (WIT). Both continuous and discrete time signals are considered. Finally, we showed how to compute the information provided by a multiresolution analysis by means of the inhomogeneous wavelet expansion. Highlighting ideas behind the WIT are presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Numerical analysis in triangular and planar three-core nonlinear optical fiber couplers (TNLDC) operating logical gates

    Page(s): 13 - 18
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1158 KB) |  | HTML iconHTML  

    In this paper, we investigate the switching process in triangular symmetric and planar symmetric three-core nonlinear fiber coupler (TNLDC) and we have numerically shown, via the coupled nonlinear Schrodinger equations (NLSEs), that logic gates AND, OR and NXOR can be constructed from a triangular TNLDC while the planar TNLDC produced logical gates AND, NAND, OR, and XOR. We consider two basic models. The first, one triangular symmetrical structure with three cores in an equilateral-triangle arrangement and using a control signal (CS) applied to the first core and the second model present a transverse symmetrical structure with three cores in a parallel equidistant arrangement (or planar symmetrical structure), however the position of the control signal (CS) is applied to the input of the first fiber (core 1). Looking at the transmission characteristics of the device, through the direct and cross channel, we did a study of the extinction ratio (Xratio) of these devices. In comparing the performance of both switches operating as logic gates we will use the figure-of-merit of the logic gates [FOMELG(dB)] defined as a function of the extinction ratio of the gate outputs. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Dynamic traffic analysis of metro-access optical packet switching networks having mesh topologies

    Page(s): 19 - 22
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (971 KB) |  | HTML iconHTML  

    We have investigated the performance of various optical packet switched network (OPSN) architectures comprising optical bufferless nodes and fully connected mesh topologies, under uniform traffic distribution, i.e., all nodes generate the same traffic. We demonstrate that increasing the number of nodes in OSPNs does not necessarily increase performance, or even capacity. By establishing an efficiency parameter based on average number of hops and effective network capacity, decision tables and graphs can be generated and utilized in network planning. Moreover, regular and quasi- regular optimized topologies lead to lower latency, higher throughput, and lightpaths with significantly better traffic distribution. The optical nodes have simple configuration and are totally compatible with WDM networks. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • New trigonometric transforms over prime finite fields for image filtering

    Page(s): 23 - 28
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (696 KB) |  | HTML iconHTML  

    This paper introduces a complete family of trigonometric transforms over prime finite fields (FFTTs). Eight cosine transforms and eight sine transforms are defined, denoted FFCT and FFST, respectively. The property of symmetric convolution for these new tools is introduced. It is shown that the use of this operation, together with the development of fast algorithms, allows efficient computation of linear convolutions via FFTTs. A discussion concerning application of these transforms in the field of digital image processing is presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A fuzzy approach for adaptive control of MPLS network traffic flows

    Page(s): 29 - 34
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (821 KB) |  | HTML iconHTML  

    One of the major challenges nowadays when managing IP networks is to guarantee proper quality of service by using network infrastructure in an optimized way. One of the recently proposed solutions is the so called traffic engineering with MPLS. In this paper, we propose a novel approach for adaptive fuzzy model-based flow control in MPLS networks. Current research treats MPLS as the Internet's solution to high performance network. A nonlinear predictive controller is designed on the basis of a Takagi-Sugeno fuzzy model. By online adaptation of the fuzzy model, high control performance can be achieved for network traffic processes multiplexed in a single buffer server. Our developed fuzzy predictor consists of a two-step algorithm: an adaptive training with covariance resetting and a gradient-based learning algorithm for refining the first part of the learning procedure. The effectiveness and online applicability of the proposed approach are demonstrated by simulations using real network traffic traces. In fact, the proposed approach is capable of providing better system performance than some existing flow control schemes. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A new propagation model for cellular planning

    Page(s): 35 - 37
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1506 KB) |  | HTML iconHTML  

    In cellular planning, it is important to guarantee the system capacity in order to ensure the minimum power necessary to provide acceptable levels of the received signal at the mobile terminals. The transmission effects in adjacent areas must be estimated, to identify the limiting zones, where the signal level is minimum and the ones where there is a possibility of signal interference. Therefore, it is important to choose an adequate prediction model for the cell planning. This paper presents the description of a new propagation model for cell planning. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On the multivariate α-µ distribution with arbitrary correlation

    Page(s): 38 - 41
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (570 KB) |  | HTML iconHTML  

    In this paper, an exact new closed formula for the multivariate alpha-mu joint probability density function (PDF) is derived allowing for an arbitrary correlation matrix. In addition, the bit error rate (BER) and the outage probability for the selection combining (SC) technique in a correlated alpha-mu fading channel is obtained. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Circulant graphs and spherical codes

    Page(s): 42 - 45
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (598 KB) |  | HTML iconHTML  

    Circulant graphs are homogeneous graphs with special properties which have been used to build interconnection networks for parallel computing. The association of circulant graphs to a spherical code in dimension 2k is presented here via the construction of an isomorphic graph supported by a lattice in Rk. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Method for obtaining spectrally efficient orthogonal UWB pulse shapes

    Page(s): 46 - 51
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (826 KB) |  | HTML iconHTML  

    In this paper we present a method to obtain a set of orthogonal pulses to be used in pulse shape modulation (PSM) for ultra-wide band (UWB) communications. The pulses are built as linear combinations of Hermite functions which are shown to have unique advantageous features. Mathematical restrictions of orthogonality and spectral efficiency are introduced as guidelines to a fully explained search procedure to find the best set of pulses. Additionally, this procedure is adapted and used to find a single FCC-compliant pulse shape. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Modified MODEX method for direction finding with improved threshold performance

    Page(s): 52 - 57
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (614 KB) |  | HTML iconHTML  

    We propose to modify the MODEX algorithm for estimating direction of arrival (DOA) of plane waves using array of sensors. The MODEX algorithm is a method of direction estimation (MODE) based estimator that conveniently increases the number of MODE estimates, increasing the order of the polynomial, whose roots (candidates) estimate the DOA parameters. To select the better set of candidates, MODEX employs a maximum likelihood (ML) procedure. The proposed method affects the candidate selection process and improves its performance. This performance gain is achieved by replacing the original sample covariance matrix by a new one computed after a noise reduction filtering on the snapshot vectors. The modified selection procedure improves the MODEX performance and reduces significantly the threshold signal-to- noise ratio. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Alternatives of interactivity in a digital terrestrial TV platform: a techno-economic approach

    Page(s): 58 - 62
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (660 KB) |  | HTML iconHTML  

    Return channel interactivity is a digital TV feature that leads to a bidirectional information flow. This article presents an analysis of four technological alternatives for the digital terrestrial TV platform return channel subsystem, to be deployed in Brazil. Major aspects taken into account for choosing the most suitable alternative are highlighted, such as the performance and cost factors, in light of the country's regional social and economic differences, the conditions under which the broadcast and telecommunication services are rendered, and the coverage as well as the availability of the main networks that support such services. Deployment cost estimates related to the selected alternative - WiMAX - are also presented by considering the coverage arrangements that best satisfy Brazil's singularities, the TV signals coverage and the demographic conditions of each Brazilian municipality. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Experimental and theoretical analysis of packaging inductances and stray capacitances of a Semiconductor Optical Amplifier

    Page(s): 63 - 66
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (594 KB) |  | HTML iconHTML  

    Impedance measurements of an encapsulated semiconductor optical amplifier (SOA) were used to obtain the SOA equivalent circuit parameters. The effect of decreasing the packaging inductances and stray capacitances are then analyzed aiming the SOA enhancement as a high-speed electro-optical switch. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Four wave mixing in a dispersion decreasing fiber (DDF) for a WDM system

    Page(s): 67 - 70
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1527 KB) |  | HTML iconHTML  

    Numerical investigation of the propagation of ultrashort pulses in the region of 1.55 mum and the conversion efficiency for the FWM and modulation instability of ordinary and different dispersion decreasing fibers for WDM systems was studied. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Admission control for VoIP over HSDPA in a mixed traffic scenario

    Page(s): 71 - 76
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (426 KB) |  | HTML iconHTML  

    Transporting voice over IP, instead of traditional CS voice, is a necessary prerequisite for an all IP network. Among the hurdles that need to be overcome are the QoS demands of VoIP, which comprise timely and error free delivery of comparatively low rate packet streams. One way to provide the necessary QoS for VoIP is some admission control strategy, where an incoming connection that cannot have its quality requirements fulfilled is blocked. This paper comprises a proposal and evaluation of a call admission control framework aiming at improving system capacity and/or service priorization by providing QoS guarantees for speech users in HSDPA. The main focus is the control of packet delay, since it is a crucial requirement for real-time services. The results show that admission control is able to provide performance improvements and mitigation of the effects from overloaded conditions, in a mixed traffic scenario comprised of VoIP and Web users. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Novel scheduling algorithms aiming for QoS guarantees for VoIP over HSDPA

    Page(s): 77 - 82
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (427 KB) |  | HTML iconHTML  

    The growth in the number of voice over IP (VoIP) users on the Internet makes it the service with the highest interest to be provided by cellular operators. On the other hand, it demands very strict QoS control, which becomes even more complicated in wireless networks, because packets can be lost due to radio link transmission errors, as well as network congestion. Within this paradigm, scheduling strategies appear as the most suitable solution to cope with QoS guarantees under high loads, where the resources should be carefully distributed among the users in order to fulfill their QoS requirements. This work comprises the proposal and evaluation of some scheduling algorithms aiming to improve system capacity and QoS guarantees for speech users in HSDPA. The results show that the scheduling algorithms that mix fairness with channel information to get improvements of the multi-user diversity provide the best performance. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Packet scheduling for Voice over IP over HSDPA in mixed traffic scenarios with different end-to-end delay budgets

    Page(s): 83 - 88
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (414 KB) |  | HTML iconHTML  

    By means of dynamic system-level simulations, this work evaluates whether the studied Packet Scheduling (PS) algorithms are capable of guaranteeing the quality of service (QoS) of the voice over IP (VoIP) on a scenario where the VoIP and Web browsing services will compete for the same resources and there is a maximum allowed end-to-end delay for VoIP packets. Two sets of algorithms were considered: QoS-differentiated and non-QoS-differentiated algorithms. It was verified the system capacity gains when the VoIP delay budget is increased. Regarding the PS performance, those algorithms able to perform QoS differentiation presented better performance in terms of system capacity and QoS compared to those non-QoS-differentiated algorithms. Among the former category, those that take into consideration delay requirements of the VoIP service presented the best overall capacity for all traffic mixes and delay budgets. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An efficient Lloyd-Max quantizer for Matching Pursuit decompositions

    Page(s): 89 - 94
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (461 KB) |  | HTML iconHTML  

    Several applications are using the matching pursuit algorithm for signal and video compression. The matching pursuit approximates signals iteratively using linear combinations of pre-defined atoms of a dictionary. In compression applications matching pursuits coefficients, which multiply the atoms in the linear combination, need to be quantized. The Lloyd-Max quantizer is known to be the best quantizer for a given source. However, to design a Lloyd-Max quantizer the statistics of the source need to be known. The statistics of matching pursuit coefficients are difficult to model. In this paper, starting from the observation that the statistics of the angles between the residues and the atoms present little variation along matching pursuit iterations, we propose to use these statistics to model the ones of matching pursuit coefficients. This permits the design of Lloyd-Max quantizers for matching pursuit coefficients. The Lloyd-Max quantize is compared to a state-of-the-art off-loop matching pursuit quantization scheme. Results show that the proposed scheme has good rate-distortion performance, specially at low rates. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Parameter optimization for importance sampling in encoded systems

    Page(s): 95 - 99
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (453 KB) |  | HTML iconHTML  

    In this paper we present a new methodology based on the stochastic gradient descent to optimizing parameters of the biased distribution along importance sampling simulations. A particular aspect of the new technique is that of use of multiple parameters for the simulation of each codeword. An example of application estimating the performance of a encoded system is given. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Evaluation of transient dynamic impact in gain controlled EDFAs

    Page(s): 100 - 102
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (350 KB) |  | HTML iconHTML  

    In this paper, the EDFA transient behavior was experimentally characterized in terms of the Q factor following severe amplifier input power variations. The performance was observed for a conventional EDFA and for optically and electronically (feedforward and feedback modes) gain-controlled EDFAs. Estimations of the Q factor were obtained by an error analyzer in burst mode after the delay of a gate pulse had been varied within the amplifier response time interval. Electronically controlled EDFAs in booster applications showed severe penalties during transients whilst optically controlled EDFAs as in line amplifiers were able to practically keep the Q factor unchanged during input power variations. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Dispersion characteristics of fin lines with photonic substrate

    Page(s): 103 - 108
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1559 KB) |  | HTML iconHTML  

    Current and foreseen applications of photonic crystals especially the PBG (Photonic Band Gap) can be divided according to their principle of functioning. In this work an efficient method is presented for the accurate full-wave analyses of the unilateral and bilateral finlines with a 2D PBG material as substrate. To analyze its efficiency, it's necessary to determine the phase, attenuation and effective dielectric constants. In order to analyze the behavior of the structure with this substrate, the full wave TTL (Transversal Transmission Line) method is used. Numerical results for the attenuation and effective dielectric constant of unilateral and bilateral finline with PBG substrate are presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Air core waveguides composed by elliptical metallic nanostructures operating at optical frequencies

    Page(s): 109 - 112
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1764 KB) |  | HTML iconHTML  

    Air core waveguides with very low losses can be designed by removing a line of rods at the center of a periodical arrangement of elliptical metallic rods in a square lattice. The use of composite nanostructures made possible the engineering of the cladding properties of the waveguides to present very low equivalent refractive index. The mechanism of propagation in these kind of guides is the total external reflection. In this work, the dependence of the transmission properties of these waveguides on the shape and orientation of the metallic elliptical wires are analyzed by an efficient frequency domain finite element approach. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Novel frequency domain finite element formulation for optical circuits in nonlinear photonic crystals

    Page(s): 113 - 117
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1642 KB) |  | HTML iconHTML  

    An efficient technique based on the finite element method in the frequency domain for the analysis of nonlinear photonic crystals based optical circuits is here presented. The solution of the nonlinear Helmholtz equation is obtained by an iterative process involving linear problem solutions. The present approach uses isoparametric curvilinear elements for the spatial discretization and perfectly matched layers to truncate the computational domain. Numerical examples are presented in order to validate the efficiency of the present method. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Analysis of optical switching circuits based on nonlinear photonic crystals by the frequency domain finite element method

    Page(s): 118 - 122
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1704 KB) |  | HTML iconHTML  

    Optical switching devices based on nonlinear photonic crystals are analyzed by an efficient technique based on the frequency domain finite element method. The solution of the nonlinear Helmholtz equation is obtained through an iterative process involving linear problems solution. Also, the method uses isoparametric curvilinear elements for the spatial discretization and nonlinear perfectly matched layers to truncate the computational domain. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Further results on convolutional codes based on a minimal trellis complexity measure

    Page(s): 123 - 128
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (564 KB) |  | HTML iconHTML  

    While in most literature the decoding complexity of convolutional codes has been measured by the encoder memory size, in this paper we study convolutional codes under the total number of edge symbols per information bit in the minimal trellis module representing them as the measure of decoding complexity. We conduct a code search restricted to the recently introduced class of generalized punctured convolutional codes (GPCC), which is broad enough to contain good codes and yet has structural properties that facilitate the code search. For the same decoding complexity and the same code rate, new codes are compared to well-known existing classes of convolutional codes such as punctured convolutional codes (PCCs) and unit-memory codes (UMCs). The comparison is extended to convolutional codes recently found by Rosnes and Ytrehus (RY), who have considered the maximum entry of the state complexity profile of the minimal trellis module as the trellis complexity in their code search. As reflected by the comparison carried out in this paper, the best (in a distance spectrum sense) convolutional codes of existing and new trellis complexities are tabulated. We note that, for the same decoding complexity and the same code rate, some of the new codes have larger free Hamming distance than the existing UMCs, while some other new codes have slightly improved distance spectrum as compared to best PCCs. On the other hand, some of the RY codes are better than the best GPCCs searched up to the present time. View full abstract»

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