Although distance education has centuries of history, online education is barely 25 years old. These modalities were initially used as an alternative or substitute for onsite traditional teaching, and were especially dedicated to those who could not attend a traditional university. This caused many people to consider them second-rate. Currently, a lot of work has been done to improve online training and there are very high quality programs that far exceed the quality of many onsite learning. This paper presents a comparison between onsite and online students of the same degree. This comparison is possible thanks to the fact that the assessment system is the same in both modalities. The results show that it cannot be conclusively affirmed that one modality is better for the development of skills and acquisition of knowledge in a MSc in Electrical Engineering, which supports both study modalities.

Despite high costs and lengthy deployments, satellite communications have traditionally been used to provide coverage in remote areas. However, given the fact that there is no radio infrastructure available in these areas, Near Vertical Incidence Skywave (NVIS) technology has positioned itself as an attractive alternative to communicate with low-power nodes in remote areas. This type of communication works in the HF frequency range complying with STANAG and MIL-STD standards, which define a physical layer for scenarios that differ from NVIS and low-power communication. The purpose of this paper was to present the definition of a new communication physical layer based on single-carrier frequency-domain equalization (SC-FDE) based on these standards but adapted to the ionospheric communication channel. This physical layer was compared to an OFDM-based layer from a previous study. The experiments performed show that this new approach achieves better results than OFDM in terms of a higher signal quality with a higher specific BER probability. Finally, this layer was also used in the theoretical design of an NVIS gateway to link sensor network devices spanning large-scale remote areas in a secure manner in the context of ubiquitous sensor networks (USN).

Sensor networks have become more popular in recent years, now featuring plenty of options and capabilities. Notwithstanding this, remote locations present many difficulties for their study and monitoring. High-frequency (HF) communications are presented as an alternative to satellite communications, being a low-cost and easy-to-deploy solution. Near vertical incidence skywave (NVIS) technology provides a coverage of approximately 250 km (depending on the frequency being used and the ionospheric conditions) without a line of sight using the ionosphere as a communication channel. This paper centers on the study of the ionosphere and its characteristic waves as two independent channels in order to improve any NVIS link, increasing its robustness or decreasing the size of the node antennas through the appliance of specific techniques. We studied the channel sounding of both the ordinary and extraordinary waves and their respective channels, analyzing parameters such as the delay spread and the channel’s availability for each wave. The frequency instability of the hardware used was also measured. Furthermore, the correlation coefficient of the impulse response between both signals was studied. Finally, we applied polarization diversity and two different combining techniques. These measurements were performed on a single frequency link, tuned to 5.4 MHz. An improvement on the mean bit energy-to-noise power spectral density (Eb/N0) was received and the bit error rate (BER) was achieved. The results obtained showed that the extraordinary mode had a higher availability throughout the day (15% more availability), but a delayed spread (approximately 0.3 ms mean value), similar to those of the ordinary wave. Furthermore, an improvement of up to 4 dB was achieved with the usage of polarization diversity, thus reducing transmission errors.

Every year, the number of ubiquitous sensor networks (USN) is increasing and the need for remote USN communications is emerging in some scenarios. As an alternative to satellite communications, more interests are focused on high frequencies (HF) communications as a low-cost option to reach links of more than 250 km without a line of sight. The HF standards are designed for generic communication channels being not robust for near vertical incidence skywave (NVIS) USN. In this article, we propose a new protocol for USN in remote places based on NVIS communications. For that purpose, we study the main characteristics of the NVIS channel with the presence of groundwaves, particularly in Antarctica. We analyze the availability of the channel, the height of the layers, the delay spread, and the Doppler spread. On the basis of the results obtained, we propose two protocols based on an OFDM (orthogonal frequency division multiplexing) modulation depending on the presence of the groundwave at the receiver. Finally, we make a simulation of the two OFDM configurations and we compare it with real tested standard modulations. The results show a better performance of the new protocol compared to the current HF standards.

Every year more interest is focused on high frequencies (HF) communications for remote sensing platforms due to their capacity to establish links of more than 250 km without a line of sight and due to them being a low-cost alternative to satellite communications. In this article, we study the ionospheric ordinary and extraordinary waves to improve the applications of near vertical incidence skywave (NVIS) on a single input multiple output (SIMO) configuration. To obtain the results, we established a link of 95 km to test the diversity combining of ordinary and extraordinary waves by using selection combining (SC) and equal-gain combining (EGC) on a remote sensing platform. The testbench is based on digital modulation transmissions with power transmission between 3 and 100 W. The results show us the main energy per bit to noise spectral density ratio (Eb/N0) and the bit error rate (BER) differences between ordinary and extraordinary waves, SC, and EGC. To conclude, diversity techniques show us a decrease of the power transmission need, allowing for the use of compact antennas and increasing battery autonomy. Furthermore, we present three different improvement options for NVIS SIMO remote sensing platforms depending on the requirements of bitrate, power consumption, and efficiency of communication.

Every year, the number of Internet of Things devices is growing exponentially. The current Internet of Things technology to support the connectivity of such a huge number of devices is limited by the coverage of the base stations deployed. In case of remote areas without coverage of any operator, the use of a satellite connection is such a high‐cost option. The only alternative option for very remote sensor is high frequency (HF) communications with ionospheric reflection. The HF band (3–30 MHz) with Near Vertical Incidence Skywave allows a large coverage area (up to 250 km) without the need of line of sight. The HF radio links usually need higher power transmissions with larger antennas supported by a mast. In this paper, we explore a new transmission scheme for low‐power transmissions, which is equivalent to use small and low gain HF antennas. We study the performance of several digital modulations using different bandwidths and transmission power. The field tests have been done around the Spanish Antarctic Base at Livingston Island to ensure the availability of the system even in polar areas where the behavior of the ionosphere is quite different from lower latitudes. However, the proposed physical layer fits well with any other remote location that requires low power data communication.

The UN General Assembly adopted the 2030 Agenda for Sustainable Development, an action plan in support of people, the planet and prosperity. Within the 17 Sustainable Development Objectives (SDO), we have quality education (fourth objective) and the reduction of inequalities (the tenth SDO). Rural communities tend to be one of the most disadvantaged environments and development education is one of the most effective mechanisms to alleviate these inequalities. In this framework, the Urubamba Project for International Cooperation is presented, and within it, the Ñawi Project for visual education. Both projects are developed in the Andean areas of Cusco (Peru) through university community participation. In these lines of action, Information and Communication Technologies (ICTs) are presented as a relevant and effective element to achieve their objectives: introduction of ICTs in education to create inclusive socio-educational environments and ICTs as an analysis tool for the visual education project (prevention and correction). This work focuses on the Ñawi Project and the satisfactory results that have been obtained.

The number of Internet of Things (IoT) devices has experienced a large growth during the last decade, as well as the data volume gathered from remote sensors. Satellites are still a suitable communication method and may be preferable for a remote ubiquitous sensor network (USN), which sometimes are located in places without much communications infrastructure where coverage is the principal drawback. Alternatively, the proposed solution for this article aims at a near-vertical incidence skywave (NVIS) channel for high frequencies (HF) with a low-cost platform, allowing a low-power transmissions coverage area up to 250 km for USN. The HF standards are focused on generic communication channels not being robust for NVIS communications. In this article we study and test an alternative based on orthogonal frequency-division multiplexing (OFDM) modulations to make them more robust and less dependent on the channel NVIS communications. For that purpose, we test the HF standard modulations and a designed OFDM modulation to prove the robustness of each. This study has been tested between Barcelona and Tarragona, using different transmission power levels and modulation orders.

This data set contains the IQ data files acquired in Caleta Argentina during the Spanish Antarctica campaign from 4-2-2019 at 15:07 UTC from, the 8-2-2019 at 12:59 UTC from the founded project by CTM2015-68902-R (MINECO/FEDE). This data are the ionosphere sensing data, the sensing channel is realized by modifying the power transmission, channel BW, and the modulation (from 2QAM to 32QAM, 2PSK to 32PSK and 2FSK to 32FSK).

Although many physical layer solutions have appeared for remote sensors and Internet of things during the recent years, none of them is suited to very remote sensors in areas away from any mobile operator coverage. In that case, a solution on the basis of near vertical incidence skywave (NVIS) with reflection in the ionosphere may be very attractive. Using NVIS, no line of sight is needed and the coverage is much bigger than any other system operating in either the very high frequency (VHF) or ultra high frequency (UHF) band. In this paper, we present a new transmission scheme for very remote sensors using the NVIS transmission technique.

The Antarctica is a continent mainly devoted to science with a big amount of sensors located in remote places for biological and geophysical purposes. The data from these sensors need to be sent either to the Antarctic stations or directly to the home country. For the last 15 years, La Salle has been working in the application of HF communications (3–30 MHz) with ionospheric reflection for data collection of remote sensors in Antarctica. We have developed and tested the several types of modulations, the frame structure, the radio-modem, and the antennas for two different scenarios. First, a long-range transequatorial (approximately 12,800 km) and low-power communication system is used as an alternative to satellites, which are often not visible from the poles. This distance is covered with a minimum of four hops with oblique incidence in the ionosphere. Second, a low-power system using near vertical incidence skywave (NVIS) communications provides coverage in a surface of approximately 200–250 km radius, a coverage much longer than any other systems operating in either the VHF or UHF band without the need of line of sight.

In this paper we present a new communications solution for remote villages in developing countries. The system is based in the Near Vertical Ionospheric Skywave (NVIS) technique, able to achieve coverage areas up to 250 Km without line of sight. It is a low-cost, low-power system that can be easily installed and put into operation. The radio system communicates with a smartphone, where a messaging app is running, so text and low resolution images can be sent without the need of any mobile operator. The system has been tested between one of the Andean communities of the Sacred Valley of Incas in Peru and Urubamba, the nearest city.

Recent developments in radiation detection technology have demonstrated the feasibility of simultaneous magnetic resonance imaging (MRI) and time-of-flight positron emission tomography (TOF-PET). In this paper we report on a compact detector module design for TOF-PET compatible with MR based on the FlexToT front-end application specific integrated circuit (ASIC), a fast, low-power front-end readout for silicon photomultiplier arrays. The module comprises scintillators, photosensors, ASICs, field-programmable gate arrays, and USB or Ethernet protocols for communication with data acquisition systems. The small footprint of the proposed design allows its use on positron emission tomography (PET) inserts for existing MRI equipment, both whole-body scanners, and dedicated organ systems. The main design features are presented together with results from the characterization of a proof-of-concept prototype in terms of radiation detection and measurements of radio frequency emission spectra from the electronic components. Ongoing work is focused on implementing and characterizing a full module inside MRI for ensuring electromagnetic compatibility, addressing proper shielding, and the possibility of simultaneous PET-MR acquisition using our compact detector module design.

This paper presents the comparison of the BER performance between SC-FDE, orthogonal frequency division multiplexing (OFDMA) and single-carrier frequency division multiplexing access (SC-FDMA) in a long haul HF data link with low SNR. The goal of the comparison is to define two operation modes for two QoS; a robust mode and a high throughput mode, in order to transmit data from remote sensors in Antarctica through a 12760 km ionospheric link with a power amplifier of only 200 W. Clipping and amplification of the waveforms have been applied to SC-FDMA and OFDMA in order to compensate the PAPR and therefore maximize the SNR. The Antarctic HF link has been studied for 11 years, and we have described the link in terms of availability, SNR, delay and Doppler profile, and also spread spectrum techniques have been tested for data transmission. Based on those previous studies results we have developed a test bed to compare these transmission techniques, providing promising results in our low power ionospheric link from Antarctica.

La Salle and the Observatori de l’Ebre (OE) have been involved in a remote sensing project in Antarctica for the last 11 years. The OE has been monitoring the geomagnetic activity for more than twenty years and also the ionospheric activity of the last ten years in the Spanish Antarctic Station Juan Carlos I (ASJI) (62.7 ° S, 299.6 ° E). La Salle is finishing the design and testing of a low-power communication system between the ASJI and Cambrils (41.0 ° N, 1.0 ° E) with a double goal: (i) the transmission of data from the sensors located at the ASJI and (ii) the performance of an oblique ionospheric sounding of a 12,760 km HF link. Previously, La Salle has already performed sounding and modulation tests to describe the channel performance in terms of availability, Signal-to-Noise Ratio (SNR), Doppler spread and delay spread. This paper closes the design of the physical layer, by means of the channel error study and the synchronization performance, and concludes with a new physical layer proposal for the Oblique Ionosphere Sounder. Narrowband and wideband frames have been defined to be used when the oblique sounder performs as an ionospheric sensor. Finally, two transmission modes have been defined for the modem performance: the High Robustness Mode (HRM) for low SNR hours and the High Throughput Mode (HTM) for the high SNR hours.

La Salle and Ebro Observatory have been involved in remote sensing projects in Antarctica for the last 11 years (approximately one solar cycle). The Ebro Observatory has been monitoring and analyzing the geomagnetic and the ionospheric activity in the Antarctic Spanish station Juan Carlos I (ASJI) (62.7°S, 299.6°E) for more than eighteen and ten years, respectively. La Salle has two main goals in the project. The first one is the data transmission and reception from Antarctica to Spain to obtain a historical series of measurements of channel sounding of this 12,760-km ionospheric HF (high frequency) radio link. The second one is the establishment of a stable data low power communication system between the ASJI and Cambrils, Spain (41.0°N, 1.0°E), to transmit the data from the remote sensors located on the island. In this paper, both narrowband and wideband soundings have been carried out to figure out the channel availability performed using a frequency range from 2 to 30 MHz with 0.5 MHz step during the 24 h of the day, encompassing wider channel measurements than previously done, in terms of hours and frequency. This paper presents the results obtained for the austral summer in 2014, using a monopole antenna at the transmitter and an inverted V on the receiver side. These results led us to the final physical layer design for the long Remote Sens. 2015, 7 11713 haul link, dividing the day into two parts: daytime, with low data throughput design, and nighttime, reaching high data throughput.

The geophysical observatory in the Antarctic Spanish Station Juan Carlos I (BAE), on Livingston Island (62.6S, 60.4W), has been monitoring the magnetic field in the Antarctic region for more than fifteen years. In 2004, a vertical incidence ionospheric sounder was incorporated to the observatory, which brings a significant added value in a region with low density of geophysical data. A High Frequency (HF) communications system was installed in 2004 in order to transmit the geomagnetic station recordings throughout the year, due to the fact that the BAE is only accessible during the austral summer. As the power supply is very limited when the station is not accessible, we had to design a low-power HF transceiver with a very simple antenna, due to environmental restrictions. Moreover, the flow of information is unidirectional, so the modulation has to be extremely robust since there is no retransmission in case of error. This led us to study the main parameters of the ionospheric channel (Signal to Noise Ratio -SNR-, delay spread, Doppler spread and availability) with narrowband and wideband soundings, and the design of modulations specially adapted to very low SNR scenarios with high levels of interference. In this poster, a review of the design of our remote geophysical observatory and associated transmission system from Antarctica to Spain (12760 km) during the last decade is presented.

Skywave ionospheric communication systems offer a good choice to satellite communications when transmitting from the poles. For the last 10 years the authors have been sounding and testing modulations through a 12 700 km high frequency link from the Spanish Antarctic Station to Spain. Previous tests comparing direct sequence spread spectrum (DS-SS) and orthogonal frequency division multiplexing (OFDM) showed that spread spectrum bit rate error (BER) results outperformed OFDM at the expense of lower bit rates. In this study the authors present three spread spectrum techniques for this long haul link that increase the bit rate and the spectral efficiency of the direct sequence while keeping the good BER performance obtained. Tests have been performed with several symbol periods as well as different bandwidth for each technique, hence the authors can conclude which combination best suits this channel.

This paper presents a comparative study between the oblique sounding results, the International Telecommunication Union Rec533 HF prediction model, and the vertical sounding results of a transequatorial long haul link. The long haul link is a 12,760 km link between the Spanish Antarctic Station, SAS, located in the Livingston Island and the Ebro Observatory (OE) in Spain. The data were collected during three consecutive surveys (2009/2010, 2010/2011, and 2011/2012). The ionospheric channel from the SAS to the OE is studied in terms of frequency availability as function of time using the measurements of an oblique incidence sounder (OIS) and measurements of several vertical incidence sounding stations (VIS) placed near the estimated radiopropagation path. The results obtained show promising correlations between VIS and OIS measurements and led us to think that the frequency of largest availability for this particular long haul radio link can be estimated from the VIS sounding measurements.

This paper presents two digital transmission techniques for long haul ionospheric links. Since 2003 we have studied the HF link between the Antarctic Spanish Base, Juan Carlos I, and Spain; and we have described the link in terms of availability, signal-to-noise ratio, and delay and Doppler power profile. Based on these previous studies we have developed a test bed to investigate two digital transmission techniques, i.e., Direct-Sequence Spread Spectrum (DSSS) and Orthogonal Frequency Division Multiplexing (OFDM), which can provide a low power, low-rate ionospheric data link from Antarctica. Symbol length, bandwidth, and constellation are some of the features that are analyzed in this work. Data gathered from the link throughout the 2010/2011 and 2011/2012 Antarctic surveys show that the spread spectrum techniques can be used to transmit data at low rate when the channel forecast is poor, but when the channel forecast is good multicarrier techniques can be used to transmit sporadic bursts of data at higher rate.