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Pulse code modulation (PCM) is an essential technique in digital communications, which transforms analog signals into digital data for transmission and processing. This technique is based on three fundamental processes: sampling, quantization and coding. With the growing demands on communication efficiency and quality, the optimization of PCM systems becomes crucial. This article explores advanced methods for the design and optimization of PCM systems, highlighting the use of sophisticated tools and algorithms to improve the overall performance of these systems. Approaches for bandwidth reduction, signal quality improvement, and error minimization are addressed. Innovative techniques such as variable pulse length coding and the use of optimization algorithms, such as genetic algorithms and the particle swarm optimization algorithm, are presented. Through practical case studies, it is demonstrated how these techniques can be applied to obtain superior results on real systems. This paper provides a comprehensive overview of advances in PCM modulation and its application in digital communication enhancement, offering recommendations for future research and applications in high-demand environments. [ABSTRACT FROM AUTHOR]

The contribution of this research work focuses on understanding the biological behavior of time-varying electric fields, specifically in the eyeball, by proposing sensitive frequency ranges, specifically for primary open-angle glaucoma POAG and RP retinitis pigmentosa. These ranges were obtained from the analysis of the frequency spectrum of the signals used by other authors in transcorneal electrical stimulation TES therapies. This analysis was performed using an algorithm proposed in this work. The frequency spectra of the signals used in the TES were also compared with the frequency response of the cellular behavior evoked by genestein drug, in order to compare the frequency characteristics of the signals applied in the TES and the biological response of the drug. which causes the same effect in POAG. [ABSTRACT FROM AUTHOR]

The design and implementation of a microstrip antenna with an insertion in the feed line of a metamaterial structure, which from a hybrid perspective combines split ring resonators (SRR) and complementary split ring resonators (CSRR), for the band of 2.4 GHz is presented in this paper. The geometrical parameters of the structure are varied in order to evaluate the response of resonance frequency and the radiation pattern of the proposed antenna. The metamaterial structure adjacent to the power line produces a considerable increase in the bandwidth concerning to that of the conventional antenna, caused by the overlapping of the frequency bands produced by the radiant patch and the left-handed structure. The bandwidth of the antenna with metamaterial inclusion is increased to twice the expected in the original patch antenna, from 2.74% to values ranging from 4.55% to 6%, at expenses of gain degradation, but without significantly affecting the coupling, and maintaining a suitable directivity. Simulation and measured results are presented and show that the proposed metamaterial structure associated with the transmission line of microstrip antennas is a novel way of using SRR and CSRR, which allows suppressing the narrow bandwidth constraint. [ABSTRACT FROM AUTHOR]

The aim of the article is to present the design, simulation and construction of a double cross antenna to receive APT images from NOAA15 satellites (National Oceanic and Atmospheric Administration) in a semi-urban environment. To achieve better performance of the antenna, its height above ground, the length and diameter of the elements, their angle of inclination with respect to the axis of the antenna coordinates and the coupling with a 50O SMA type connection port were adjusted. The built antenna allowed to receive APT images in real time, with a maximum resolution of 120dpi, gain of 4.8dBi and frequency deviation of ±17 KHz. The modulated carrier arrived at a frequency of 137 MHz and was processed by devices and tools: RTL-SDR, Sharp SDR, audio piping and WXtoimg software for decoding images. It is concluded that in semi-urban environments the double cross antenna receives well APT images. However, it is susceptible to the Doppler Effect and noise due to the presence of low order nulls. [ABSTRACT FROM AUTHOR]

This paper presents the implementation outcomes of the Equivalent Circuit Model (ECM) acting in conjunction with the Matrix Cascading Method (MCM) for bandwidth calculation in cross dipole Frequency Selective Surfaces (FSSs). Dielectric layers are used as a support of resonant elements in FSSs. Models of effective permittivity of the dielectric layers in FSSs allow to determine the effect of the material used as insulating support of the resonant elements, in relation to the resonant frequency and bandwidth, as a function of the thickness of the dielectric material. However, in this approach, the insulating support is considered as thin dielectric, and therefore, it is modeled as a lumped parameter. This consideration may lead to unsuitable results in calculating the bandwidth for thick dielectric supports. The novelty of the paper is the implementation of the Equivalent Circuit Model together with the Matrix Cascading Method to determine the frequency response of the cross dipole selective surface for any dielectric thickness and configuration. It is notable the low computational time as well as the acceptable accuracy obtained with the proposed approach, compared to Ansys-HFSS simulations. [ABSTRACT FROM AUTHOR]

Introduction- The traditional networks mostly implement devices where the control plane is distributed and mixed with the data plane; this fact does not allow a fast evolution towards a process that contributes to improving the transport of services. Otherwise, Software Defined Networking is a set of transport services that optimize the use of resources as these have a centralized network structure. Objective- To determine the aspects that enable the software- defined networking to provide quality of service features in data networks. Methodology- This study is performed through network simulation over the same base network and under the same working conditions by carrying out measurements of the packet forwarding response time and management of the transported bandwidth. This study includes the demonstration of the multimedia content transport over a network architecture defining priorities to the links. Results- The outcomes show how the Software Defined Networking achieves better management of data transmission through the base network. In the same way, the previous outcomes are reinforced with those obtained in the quality of service test performed on the streaming of a multimedia flow. Conclusions- Due to the centralized control of Software Defined Networking, forwarding functions with the quality of service features are enabled in data networks based on layer-2 devices. [ABSTRACT FROM AUTHOR]

In this paper is presented a study of the insertion of metamaterial structures in a rectangular patch antenna fed by microstrip line linear polarization to achieve increased bandwidth. The main characteristics of left-handed materials are analyzed and their behavior is investigated inside the antenna, which allows obtaining an increase bandwidth and improve some of the fundamental parameters in the design of rectangular patch antennas by applying the theory of themselves and simulation tools supported by computer-assisted. Initially a study of the influence that makes is performed, the cell structure composed by complementary ring resonators open square in shape with their respective "gaps" associated to the patch and position thereof on the parameters of interest microstrip antenna especially bandwidth. The results obtained allowed to conclusions that the location of metamaterial associated power line exerts a marked influence on the radiating structure; an increase in bandwidth and a decrease in efficiency over conventional microstrip antenna structures occur no left-handed. Besides confirm that the increased the dimensions of the complementary rings cause a decrease in the resonance frequency. Finally, the design of a microstrip antenna with left-handed structures for the 2.4 GHz ISM band is presented. [ABSTRACT FROM AUTHOR]

Formulations that enable the assessment of the effects of parameters both geometrical and associated to the dielectric on the determination of the bandwidth in Frequency Selective Surfaces (FSS) are scarce. This forces the assessment of the aforementioned effects through parametric analysis. The aim of this type of analysis is to determine the influence on the bandwidth of a particular parameter, either in association to the dielectric support or to geometrical parameters of the selective surface. This analysis is made in order to guide the design process of the surface. The article presents the results of an analysis based on a novel formulation to determinate the bandwidth in square loop FSS considering the effects of the geometrical variables and those associated to dielectric material, using as a method of analysis, the Equivalent Circuit Model (ECM). Therefore, this approach makes unnecessary the use of parametric analysis, based on electromagnetic software, for the assessment of the aforementioned effects on the bandwidth. For the proposed formulation, the dielectric is considered as a lumped parameter, making it suitable only for thin dielectrics. It is important to highlight the acceptable accuracy obtained with the proposed approach in comparison with the simulations implemented in software based on the Finite Element Method (FEM). [ABSTRACT FROM AUTHOR]

With the constant increase in bandwidth demand generated by consumer and business applications, it is clear that a new architecture with more capacity is needed. The Passive Optical Network (PON) systems have been standardized and are beginning to deploy massively in different markets around the world, and become in the technology that attempts to respond these needs. This article reviews the characteristics and advantages of these networks, and is made an analysis of their relevance and necessity. [ABSTRACT FROM AUTHOR]

This paper reports the main design elements of a programmable gain transimpedance amplifier (TIA) with a photodiode as sensor device. The photodiode and the TIA are part of the measurement system of a plate reader with two reading modes, absorbance and fluorescence. The photodiodes are one of the most used sensors in spectroscopy systems and TIA are fundamental for conditioning signals from such sensor block. An analysis of some aspects that must be considered in their design, such as bandwidth, gain, noise as well as the main sources of noise that affect their operation is done. An analysis of the stability of the system to ensure proper operation. Emphasis on the characteristics of the components used and detail some layout suggestions of printed circuit boards in order to minimize the leakage currents. The design presented is a novel and feasible alternative to maximize the dynamic range of measurement plate readers or other optical spectroscopy system designed and produced by the Cuban biopharmaceutical industry. [ABSTRACT FROM AUTHOR]

This paper presents the study results of the identification of the regions of spectral efficiency that satisfy the requirements of quality of service (QoS) based on restrictions of bandwidth based on IEEE 802.11 multicell. This problem is addressed from the perspective of game theory for the channeling defined in 802.11g, and considering only the nonoverlapping channels. To solve the game, the concepts of Nash Equilibrium (NE), Satisfaction Equilibrium (ES) and Efficient Satisfaction Equilibrium (ESE) are introduced, proposing an algorithm to identify regions of capacity that satisfy the QoS required by a user. Particularly, in this game, the solution that allows to guarantee the transfer information rate required by a network user while minimizing the required resources (bandwidth) is sought, allowing users to maximize the amount that can be associated to an AP on the network. In the present scenario, it is verified that the different Equilibrium NE, SE and ESE depend directly on the conditions of channel gain. [ABSTRACT FROM AUTHOR]

Existing wireless communication devices today may generate loss of conveyed information, inherent to the data processing to be transmitted. WLAN technology (Wireless Local Area Network) is linked to devices' specific restrictions and takes into account other parameters such as: bandwidth, radiation power, and range. For this reason, a great progress in developing systems to work faster and process information efficiently has been made, thus, becoming more user-friendly. The results shown in this article demonstrate that it is possible to transmit biomedical signals such as electrocardiograph (ECG), respiration, and blood pressure (BP) activities, among others, through a 2,4GHz-frequency wireless network. Nevertheless, the abovementioned situation is subject to existing regulations in Colombia regarding industrial, scientific, and medical activities (ISM), which will also be expounded. [ABSTRACT FROM AUTHOR]

This article provides a performance evaluation between DiffServ and IntServ, two computer architectures that allow the implementation of quality of service (QoS) to a given network. A simulated scenario in NS2 is proposed and the two types of QoS are implemented to evaluate variables such as jitter, bandwidth, delay, and packet loss, all with the aid of graphs and with statistical results. First, the simulation is done without implementing QoS; subsequently, IntServ and DiffServ are implemented to compare between the two architectures and define the advantages and disadvantages of each type of service and determine the most appropriate for a specific program. [ABSTRACT FROM AUTHOR]

A sparse matrix bandwidth reduction method is analyzed. It consists of equation splitting, substitution and introducing new variables, similar to the substructure decomposition in the finite element method (FEM). It is especially useful when the bandwidth cannot be reduced by strategically interchanging columns and rows. In such cases, equation splitting and successive reordering can further reduce the bandwidth, at cost of introducing new variables. While the substructure decomposition is carried out before the system matrix is built, the given approach is applied afterwards, independently on the origin of the linear system. It is successfully applied to a sparse matrix, the bandwidth of which cannot be reduced by reordering. For the exemplary FEM simulation, an increase of performance of the direct solver is obtaine. [ABSTRACT FROM AUTHOR]

Over the last years new radar systems uses have been arisen, both civil and military field. These further uses demand more data about the radar targets. Up to now, was enough to know its location, rough velocity and an approximate motion direction, even though, now there is a growing need of security and control, which requires higher accuracy measuring these targets's characteristics, even to obtain a "radar image" trying to classify or identify it. This article explains how to obtain ISAR radar images, especially using a Continuous Wave Linear Frequency Modulated Radar (CWLFM), not only in a theoretical way but also showing the results achieved in a lot of different experiments made during a four years research-project sponsored by the Spanish Ministry of Science and Technology, emphasizing the high quality of the images obtained, and also, that any kind of control or collaboration was expected from the target. Making the result more important from a practical point of view, opening up much more possible applications to radar systems. [ABSTRACT FROM AUTHOR]

Essentially, a system of communications allows to transmit and/or to receive information. The components and the characteristics of the system determine what type of information it can be transmitted or received, how many channels, in what frequencies, with what speed and fidelity, to what cost and with what covering, besides their grade of immunity in front of noise and interferences and to other operation parameters. The system of communication of data through the domiciliary electric net this constituted by two types of elements: physical and logical; their design and construction involves the electronics, the electricity and the computer science; the speed of the data is limited by the width of band of the bifilar line and for the code techniques and used modulation; the transmission frequencies are selected according to the norm CENELEC EN50065-1, the covering is local domiciliary, the immunity in front of noise and interferences depends on the transmission frequency and of the use of a transmission type to two threads: line-earth or line-neuter; as for costs, the system is an economic alternative and of quick installation for the transport of data. [ABSTRACT FROM AUTHOR]

In this paper we present a method, which has been denominated off/on-line, its objective is to calculate the reserve of resources (optimal bandwidth) in an ATM network, based on the characteristics of the traffic (MPEG-I video traces with category VBR), the characteristics of the network and certain parameters of quality of service: maximum delay between emitter and receiver and the cell loss rate in the transmission. [ABSTRACT FROM AUTHOR]