Ivan A. Perez-Alvarez

Universidad de Las Palmas de Gran Canaria | ULPGC · Instituto Universitario para el Desarrollo Tecnológico y la Innovación en Comunicaciones (IDeTIC)

In this work, a real-time software-in-loop simulation technique was employed to test and analyse an underwater wireless sensor network. This simulation should facilitate the deployment of the real network and helps guarantee the network’s expected behaviour. We study duplicated packets, one-way delay, and power consumption to analyse the network’s...

Safety in coastal areas such as beaches, ports, pontoons, etc., is a current problem with a difficult solution and on which many organizations are putting efforts in terms of technological innovation. In this work the design of a possible solution based on magnetic sensors is presented. First, a study has been made of the type of sensors that best...

In this work, the development of a software-in-loop platform to carry out Underwater Wireless Sensor Network (UWSN) simulations using a real-time STANAG 5066 stack is presented. The used protocol stack is part of a real-world implementation of an underwater wireless node based on ElectroMagnetic (EM) Underwater Radio Frequency Communication (EM-URF...

In recent years, there has been a significant effort towards developing localization systems in the underwater medium, with current methods relying on anchor nodes, explicitly modeling the underwater channel or cooperation from the target. Lately, there has also been some work on using the approximation capabilities of Deep Neural Networks in order...

An adaptive interference detector based on compressive sensing is introduced in this paper. The proposed detector is part of a narrowband interference mitigation system for wideband cognitive HF front-ends that self-adapts its configuration hinging on the behaviour of the automatic gain control. The use of a compressive sensing architecture allows...

Underwater Wireless Sensor Networks (UWSNs) using electromagnetic (EM) technology in marine shallow waters are examined, not just for environmental monitoring but for further interesting applications. Particularly, the use of EM waves is reconsidered in shallow waters due to the benefits offered in this context, where acoustic and optical technolog...

In the first part of the paper, we modeled and characterized the underwater radio channel in shallowwaters. In the second part,we analyze the application requirements for an underwaterwireless sensor network (U-WSN) operating in the same environment and perform detailed simulations. We consider two localization applications, namely self-localizatio...

En este trabajo se presenta el proyecto de Innovación Educativa Acción Tutorial on-line, concedido al Grupo de Innovación Educativa en Sistemas de Telecomunicación de la Universidad de Las Palmas de Gran Canaria, que tiene como objetivos el proporcionar un estudio sobre herramientas virtuales para tutorías online en ingeniería y usar la herramienta...

The authors present full wave simulations and experimental results of propagation of electromagnetic waves in shallow seawaters. Transmitter and receiver antennas are ten-turns loops placed on the seabed. Some propagation frameworks are presented and simulated. Finally, simulation results are compared with experimental ones.

Shallow seawaters are problematic for acoustic and optical communications. Sensor networks based on electromagnetic (EM) communications are evaluated in this environment. In order to characterize the subaquatic channel, several measurement systems have been designed, built and tested in the sea obtaining very reliable results. Experiments carried o...

We use real measurements of the underwater channel to simulate a whole underwater RF wireless sensor networks, including propagation impairments (e.g., noise, interference), radio hardware (e.g., modulation scheme, bandwidth, transmit power), hardware limitations (e.g., clock drift, transmission buffer) and complete MAC and routing protocols. The r...

We analyze the problem of localization algorithms for underwater sensor networks. We first characterize the underwater channel for radio communications and adjust a linear model with measurements of real transmissions. We propose an algorithm where the sensor nodes collaboratively estimate their unknown positions in the network. In this setting, we...

Multiple users transmit in the HF band with worldwide coverage but collide with other HF users. New techniques based on cognitive radio principles are discussed to reduce the inefficient use of this band. In this paper, we show the feasibility of the Upper Confidence Bound (UCB) algorithm, based on reinforcement learning, for an opportunistic acces...

New strategies based on cognitive radio are being discussed to make a more efficient use of the HF band. Multiple users transmit in this band with a worldwide coverage but having multiple collisions with other HF stations. The use of the Upper Confidence Bound (UCB) algorithm is proposed in this work to provide them with a dynamic spectrum access m...

New strategies based on cognitive radio are being discussed to make a more efficient use of the HF band. Multiple users transmit in this band with a worldwide coverage but having multiple collisions with other HF stations. The use of the Upper Confidence Bound (UCB) algorithm is proposed in this work to provide them with a dynamic spectrum access m...

Using the ionosphere as a passive reflector allows trans-horizon communications in the HF band, which covers the radiofrequency spectrum from 3 to 30 MHz. This band is mainly used for military communications, but also for aeronautical, maritime, and amateur communications. Besides its propagation changeability, the limitation of the HF band is the...

In this paper, we use jointly a model of narrow band interference and a congestion model to model and implement an interference simulator for the whole HF band. The result is a model to generate interfering signals that could be found in a given frequency allocation, at a given time (past, present, or future) and for a given location. Our model doe...

Although most of the research on Cognitive Radio is focused on communication bands above the HF upper limit (30 MHz), Cognitive Radio principles can also be applied to HF communications to make use of the extremely scarce spectrum more efficiently. In this work we consider legacy users as primary users since these users transmit without resorting t...

Cognitive Radio principles can be applied to HF communications to make a more efficient use of the extremely scarce spectrum. In this contribution we focus on analyzing the usage of the available channels done by the legacy users, which are regarded as primary users since they are allowed to transmit without resorting any smart procedure, and consi...

Traditional use of the HF band is limited mostly to 3 KHz for both voice and data transmission, and therefore, most of the transceivers bandwidths are also adapted to this profile. However, there are some initiatives that clearly state that much broader bandwidths may be use with the corresponding data rate increase and performance improvement in t...

Multi-carrier modulations are widely employed in ionospheric communications to mitigate the adverse effects of the HF channel. In this paper we show how performance achieved by these modulations can be further increased by means of CSI based precoding techniques in the context of our research on interactive digital voice communications. Depending o...

It is clear that in the near future much broader transmissions in the HF band will replace part of the current narrow band links. Our personal view is that a real wide band signal is infeasible in this environment because the usage is typically very intensive and may suffer interferences from all over the world. Therefore, we envision that dynamic...

We envision that dynamic multiband transmissions taking advantage of the receiver diversity (even for collocated antennas with different polarization or radiation pattern) will create a new paradigm for these links guaranteeing high quality and reliability. However, there are many challenges to face regarding the use of broadband reception where se...

The reliability of bidirectional communication link can be guaranteed with Automatic Repeat Request Procedures (ARQ). The standard STANAG 5066 describes the ARQ procedure for HF communications that can either be applied to existing HF physical layers modems or adapted to future physical layer designs. In this contribution the physical layer paramet...

Achieving reliable communication over HF channels is known to be challenging due to the particularly hostile propagation medium. To address this problem, diversity techniques were shown to be promising. In this paper, we demonstrate through experimental results the benefits of different diversity strategies when applied to multi-input-multi-output...

In this paper, the theory of linear time-variant systems is applied to multipath channels and, in particular, to ionospheric channels. Some useful formulas in time and frequency domains are given for both deterministic and random linear time-variant systems and multipath channels. The fundamental parameters of a multipath channel are the delay and...

This contribution results from the implementation of the physical layer of the STANAG 4444. Two operation modes are available in the STANAG 4444, namely the EEWF and DSWF. The performance of each mode has been evaluated making special emphasis in the DSWF one which uses Direct-sequence Spread-spectrum for symbol modulation. In order to accomplish w...

This paper addresses the real trials of a new OFDM modem specifically designed for data RADAR transmission that was promoted by the Spanish aeronautical authorities. The nature of this environment is very different of standard applications and has required some new features that will be described in the sequel. The data source is asynchronous depen...

Multi-carrier modulations are widely used in HF communications, and particularly OFDM. Delay-sensitive applications can make use of spreading schemes such as OFDM-CDM in order to cope with deep nulls in the channel. If CSI is known at transmitter, it is possible to improve performance using a bit-loading algorithm for OFDM and channel matrix SVD de...

This paper deals with the design of an integrated system that is able to transmit data with high data rate and also high quality. However, the main feature is not the enhanced performance but the objective of providing a nearly permanent and reliable communication over time. In order to overcome the long term fading, a probe modem is simultaneously...

This paper describes a broadband (1MHz) digital HF transceiver for the HF band (3-30MHz) specifically designed for the transmission and reception of multicarrier and multichannel modulations. The wide modem bandwidth (1MHz) is not meant for the transmission of a single 1MHz wide signal, since the goal is to achieve flexible transmission and recepti...

The objective of this paper is to contribute to one of the most challenging issues in modern HF communications: the exploitation of the multiantenna diversity and its impact in the need of time interleaving. Comparing two of the main diversity sources in multiantenna communications (the polarization and spatially separated antennas) we expect to em...

The principal parameters of a multipath channel are the delay and the gain coefficient of each path, and the number of significant paths. We develop a methodology for estimating path-delays and path-coefficients and applied it to the ionospheric channel estimation. Also, if path coefficients are stationary random processes, the power spectral densi...

Multi-carrier modulations are widely employed in HF communications, and particularly OFDM, mainly because their ease of generation by means of DFT and also their appealing properties that can turn a selective fading channel into a set of flat channels. In order to cope with deep nulls in the channel traditional approach has been the use of channel...

The HF band data communication link has been traditionally desired by many of the large range transmission systems although it is associated to unfavourable performances as low transmission rate, large delay and low confidence in terms of link establishment and maintenance. Although transmission rates may be high enough to transmit digital voice, d...

In this contribution, the comparison of two HF modems with coding and either OFDM or OFDM-CDM modulation, is carried out. The analysis of these techniques for low-latency applications showed clear advantage of OFDM-CDM technology. Nevertheless, its suitability is not so clear in front of coded OFDM with interleaving when applications insensitive to...

This paper presents the results of several real link tests performed with a low-latency HF modem. Three different configurations are presented, tested and compared with simulated results. The delay introduced by the system is below 100 ms, making the system capable to transport digital voice in interactive applications.

This paper deals with some highlights showing why Spread Spectrum Multicarrier Technologies as MC-CDMA are very robust for HF communications in front of plain OFDM for delay sensitive transmissions. Several steps of this research line have been published by the authors showing that uncoded interactive digital voice transmissions is feasible over th...

The present needs for more accurate modelling and simulation of the wideband HF channel motivate the development and implementation of wideband channel simulators. It has been showed that many HF communication systems may properly mitigate the ISI distortion of the HF channel, but it may perform badly under the HF noise and interference. In this pa...

The HF band data communication link has been traditionally desired by many of the large range transmission systems although it is associated to unfavorable performances as low transmission rate, large delay and low confidence in terms of link establishment and maintenance. Although transmission rates may be high enough to transmit digital voice, de...

The objective of this article is the design of a transceiver system in HF band trough software defined radio (SDR). A software-defined radio is characterized by its flexibility: Simply modifying or replacing software programs can completely change its functionality. This allows easy upgrade to new modes and improved performance without the need to...

Performance of a modem designed for HF communications is presented in this contribution. The aim was to attain the real time communication for interactive voice transmission. Therefore, powerful coding for error protection and long interleaving was not permitted. Frequency selective HF channel was converted into a set of frequency flat channels wit...

The main objective of the present design has been the development of a HF band communication system providing digital voice transmission within around 3 kHz bandwidth, through ionospheric reflection, mainly, but not only, for aeronautical environment. Interactivity, as a basic design constraint, has shown that standard structures using single carri...

Transmission in the high frequency (HF) band is considered not to be reliable, due to channel's highly dispersive characteristics, frequency selectivity, Doppler spread and multipath propagation. Briefly, it can be stated that all inconveniences of a wireless channel are present, making this channel a very hostile environment. Some innovations used...

The strong growth in DSI (1.544 Mbit/sec) has led to recent intense research in high bit-rate digital subscriber lines (HDSL). Channel equalization and echo cancellation are required for a dual-duplex HDSL communication, but these systems have to be trained before they start to transmit the data. In this work we present a new scheme that permits th...

The objective of any local echo canceller connected to any end of a digital subscriber line (DSL) is to compensate the outgoing transmit signal energy in the receiving path (commonly called near-echo) that the hybrid circuit leaks. The observed signals that usually play the role of error references for adaptive echo cancellers (EC) in data communic...

Existing blind adaptive equalizers that use nonconvex cost functions (as Bussgang type algorithms) and stochastic gradient descent suffer from lack of global convergence to an equalizer tap set that removes sufficient ISI when an FIR equalizer is used. In this paper we propose a new algorithm including tap anchoring and gain recovery into the class...

Presents a new adaptive algorithm for joint blind equalization and phase recovery in data communication systems. This algorithm is mainly based on the standard decision directed algorithm (DDA) but the incorporation of both a linear constraint in the filter coefficients and an adjustable complex parameter in the decision device, provide an unimodal...

The observed signals that usually play the role of error references for adaptive echo cancellers and channel equalizers in data communications are basically composed by data plus a residual error. The goal of such systems is to eliminate those errors to enhance the present data. However, in some systems, depending on the convergence stage, the pres...

A novel adaptive echo canceller for baseband data communications working with PAM (pulse-amplitude-modulated) signals is presented. The goal is to take advantage of the prior knowledge of the signal statistic to improve the error reference of the adaptive algorithm in situations of an advanced convergence state. In these cases, when the incoming si...

The HF communications use the ionosphere and the earth surface as passive reflectors. The use of these natural reflectors makes the viability of the links to depend on several variables as the time of the day, the season, solar radiation, sun cycles, etc. This fact becomes an inconvenient in two common phases of a HF communications: the link establ...