Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Environmental pollution is one of the biggest global problems affecting human health. The World Public Health Organization annually publishes a report with global estimates on exposure to air pollution and its impact on health, where it notified that of every nine deaths one is due to the exposure of pollution of air indoor and outdoor environments. For these reasons, the development of systems to monitor air quality, both outdoors and indoors, is currently the subject of much research. This paper presents two wireless sensor networks for monitoring air pollutant gases in two different scenarios; one for the outside, another for closed enclosures. For each scenario, the network requirements are established taking into account the particular characteristics of each scenario and the practical utility of the measurement results, the architecture derived from there to meet the requirements, the components used for its construction and the results obtained after its implementation.

This work presents the design of a PABX (Private Automatic Branch Exchange) using free hardware and software as a technological solution for the automation of telephony in small companies. The design consists of two fundamental parts: an interface card with the PSTN (Public Switched Telephone Network), controlled by Arduino Mega 2560 and configuration software with a graphical user interface that operates on the server. The designed software allows interaction with the hardware, as well as the easy configuration of the FreeSWITCH telephony engine to execute the routing of calls, the creation of IVR (Interactive Voice Response) menus, user management, among other functions. The exchange of information between hardware and software is described using a serial communication protocol designed to carry out the various telephone operations. Finally, it is demonstrated through measurements and tests that the design meets the required functionalities.

In this article, the frequency-modulated signals have been analyzed in the spectrum, with the aim of reviewing the performance of these systems to guarantee the quality of the service in the Radiocuba company. The NooElec NESDR Nano 2-Tiny Black RTL-SDR USB Set device (RTL2832U + R820T2) has been used to analyze the levels of field strength, characteristic that defines the composition of the stereo FM sign in the transmission, the frequency deviation in the modulation, the situation of guard band, adjacent channel interference and co-channel interference. Have been shown features of the FM sign and the SDR technology that help to understand these systems. Using the TVSharp software with the same device, the analogical television video signal has been visualized, observing that the development of the software reached until today, has introduced new benefits for the configuration of this same hardware element, which facilitated the verification of signals from analogical television, which was not conceived in the original design of the device. The audio corresponding to the analog video of each channel is demodulated, using the SDR Console v3.0.7 software. The power spectral density has been observed at the known frequency of a digital transmitter, although the device did not provide digital television-DTMB signals without modulating. This document offers a perspective of the meaning that acquires the information in society through the employment of SDR like an accessible option to analyze situations that many times require very expensive equipment.

In mobile communication systems over LTE, voice packets are transmitted over noisy channels that negatively affect the probability of losses. An important mechanism to combat packet loss is channel coding. The channel coding adds redundancy bits to the information packets to detect and correct errors in the detection process. This is the opposite of source coding that is responsible for eliminating re-abundance to minimize the rate of transmission. There is a compromise relationship between source and channel coding that influences the quality that users experience. In this research paper, a mechanism for optimizing the transmission ratio required in voice applications over LTE was implemented and evaluated based on finding an adequate relationship in the joint source-channel coding. The algorithm for coding selection is not original but has been modified so that it takes into account the qualitative evaluation ranges. The proposed changes have allowed an appreciable reduction in the transmission ratio required for a VoLTE connection concerning the original algorithm without changing the level in the qualitative scale of quality assessment.

The article describes the design and implementation of a weather station. The proposed network allows monitoring the temperature, humidity, and pH of an environment, specifically in coastal areas, in real-time, employing digital sensors that are easily acquired and low cost. Besides, it had extra modules to sensor the temperature and pH variables. The storage and processing of the data obtained in the measurements are carried out with the Raspberry Pi 2 device which interacts with the conditioned signals from the different sensors and implements multiple functionalities for the system such as the creation of a website. To achieve the above, a network connection was configured using Ethernet technology to access the website through any other computer and, also, the Raspberry Pi WiPi module was available for future access to the said website through mobile technology.

The main goal of this paper is the validation of the use of open-source software and low-cost hardware in the equipment of audio and video capture. To achieve this, we discuss the design of an audio and video capture equipment using the low-cost SBC (Single Board Computer) Raspberry Pi 3B, the Pi Camera V.2 modules for the video capture and the capture of the audio, the two channels AD converter with USB interface using Audio class AK5371. This design will be useful to support the implementation of a camera for video surveillance. The software architecture is divided into two layers, one for user interaction using the framework for the development of web applications Flask, and another layer that implements the stages of acquisition, processing, and streaming of the data, to be used by the multimedia application framework GStreamer. This design represents an alternative to commercial equipment, using open-source software and low-cost hardware.

Acoustic detection of land vehicles, aircrafts and vessels characteristic sounds, as well as acoustic surveillance on moving platforms, has become worldwide relevant in recent past decades, particularly those linked to defense, law enforcement, and national security issues. Construction of systems for such scenarios demands simulation tools for behavior prediction taking account aspects such as: sound sources and sensors directivity, sound waves atmospheric propagation losses, and acquisition channel transfer function. This paper in concerned with a software tool development to simulate the capture of acoustic signatures from fixed positions on a moving vehicle. The detection of gunshots from a fixed position using a vehicle-mounted gunshot detection system is specifically explained. Results confirm the usability of gunshot detection and direction of arrival estimation algorithms developed for ground gunshot detection systems. The proposed software was fully developed in LabVIEW graphic programming language.

The implementation of the Internet of Things (IoT) will change the daily life of its users by allowing the exchange of data between generalized things over the Internet. Regarding this, unless you are an expert on networks, synchronization is probably more familiar as a term used with wristwatches, than as an IoT term, however, the future of this may depend on this issue. In a world on demand where immediate results are expected, a bad synchronization method in a critical environment can end the information created only a few seconds before. This presentation is not specifically about IoT, but it sets out a reference framework on the use of an efficient synchronization method in the network infrastructure that would support it since a bad timing can lead to call and link drops, corruption, data losses, and retransmissions; videos that do not play, interrupting games, car accidents directed by GPS, among other examples.

Acoustic Distributed Sensors (ADS) are widely used for the gathering of acoustic information dedicated to the research of urban planning, environmental control, and public security. The emergence of new algorithms of computational low cost and computing devices more small, economic and affordable, has created the possibility of developing a low-cost acoustic sensor that can be deployed in an Acoustic Sensor Network (ASN). In this work, the design and development of a multichannel audio acquisition device based on Raspberry Pi are described. This device can be used as a node of an ASN. For the development of the software that is executed in the Raspberry Pi, the programming language Python was used, being obtained a library of functions that allows the work with several audio cards in a simultaneous way. The made tests have shown the Raspberry Pi as a powerful and affordable computing core for ASN’s node.

Noise is inherent to all electronic and communication systems, a fact that must be taken into account and its consequences on the system studied or designed must be analyzed. It can be defined simply (but categorically) as any random interference not related to the signal of interest and limits the minimum signal level that can be processed by a circuit or system with acceptable quality. In this paper, some basic concepts about noise and its modeling in two-port networks will be reviewed, the obtaining of noise parameters in a specific circuit will be exemplified and some lines of research currently being developed in this topic will be cited.