David Badia

Digital transmission techniques for a long haul HF link: DSSS versus OFDM

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.

Remote Geophysical Observatory in Antarctica with HF Data Transmission: A Review

The geophysical observatory in the Antarctic Spanish Station, Juan Carlos I (ASJI), on Livingston Island, has been monitoring the magnetic field in the Antarctic region for more than fifteen years. In 2004, a vertical incidence ionospheric sounder completed the observatory, which brings a significant added value in a region with low density of geophysical data. Although the ASJI is only operative during the austral summer, the geomagnetic station records the data throughout the year. A High Frequency (HF) transmission system was installed in 2004 in order to have the geomagnetic data available during the whole year. As the power supply is very limited when the station is not operative, we had to design a low-power HF transceiver with a very simple antenna, due to environmental aspects. Moreover, the flow of information was unidirectional, so the modulation had 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 and to design new modulations specially adapted to very low signal to noise scenarios with high levels of interference. In this paper, a review of the results of our remote geophysical observatory and associated transmission system in Antarctica during the last decade is presented.

Appropriateness of e-learning resources for the development of transversal skills in the new European Higher Education Area

The new European Higher Education Area (EHEA) implies not only a change in the content, length and name of the university degrees, but also a change in the pedagogical methodology. In this study, e-learning possibilities in the new scenario, where the main actor is the student, have been analyzed. Students must acquire specific knowledge of their profession, but also transversal skills for the work they develop in their jobs. So, interpersonal, teamwork, learning, communication or computing skills must be essential pieces of the instructional designs of the university degrees. The paper is focused on the analysis of the technological tools most frequently used in the learning management systems (LMSs), and of how these tools facilitate the development of the transversal skills mentioned in the Tuning Project. Tools are divided into contents tools (text, videos, simulators, e-labs, etc) and communication tools (forums, e-mail, virtual classrooms, etc.). Opinion polls to professors from engineering and humanities degrees from different Spanish universities, most of them with experience in distance education, have been used in the analysis

Narrowband and Wideband Channel Sounding of an Antarctica to Spain Ionospheric Radio Link

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.

Physical Layer Definition for a Long-Haul HF Antarctica to Spain Radio Link

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.

Do Multimedia Contents increase the effectiveness of learning

In an engineering online degree, contents are usually given in a few different modalities: text, hypertext, video-clips and simulators or virtual laboratories. The aim of this study is to find out about their appropriateness for learning electrical engineering. In this paper, comparative studies on what kind of contents are better for the effective learning of some technical concepts are presented. The analysis is based on pilot tests in which students are divided into two statistically equivalent groups. Students in each group study with a different modality. Then the results from the two groups are compared. Besides these tests, students opinion polls are analyzed. The results obtained demonstrate how multimedia contents are more efficient than texts in the learning process of certain concepts. Nevertheless, problems or failures in the technology used have a very negative effect

Antenna theory education tool using an interactive and movie-based electronic book

A virtual tool (electronic book) for antenna theory and electromagnetic propagation is presented. A variety of radiation and electromagnetic problems ranging from linear antennas to arrays, radiation in time domain, microstrip antennas, smart antennas, and reflectors can be simulated. The material is useful both at undergraduate and graduate engineering courses. The education tool uses a user-friendly interface thanks to Mathcadreg software package which has been used to develop the electronic book. Moreover, navigation throughout the book follows the same rules used by internet users, therefore, no extra knowledge have to be introduced on how to use the present tool. Besides the user-friendly interface, the book also features visualization capabilities, 3D representations and videos, which play a significant role in teaching. The electronic book comes with several exercise sections having twofold objectives: first, students can check their own progress, and second, data from such exercises is provided to professor/mentor. This data is extremely useful to determine whether a given section can be considered completely understood or some extra emphasize needs to be done. All the material presented in the book can be complemented by extra peer review scientific papers given at the end of each section, most of them can be downloaded (obviously, depending on the contract between university and editorial). The book has been tested using objective data resulting in good acceptance.

Work in Progress - Interactive multimedia contents and synchronous graphical communication tools for distance learning in Engineering Degrees

The curricula design in distance universities has been influenced by the fast development of communications, and Web based learning has become generalized. Typical contents are based on hypertext, with communication models between students and lecturers being based on e-mail, text-based forums, and text-based chats. These tools alone do not seem to be good enough for engineering distance education, where formulae and graphics are necessary. Therefore, a new LCMS (learning content management system) is presented in this paper. Contents are based on Web guides, short videos and e-labs or simulators, and graphical communication (synchronous and asynchronous) is possible, by means of e-boards and videoconference Web (e-classroom)

Carpet with presence detector

A carpet with presence detector consists of a big capacitor manufactured with usual materials inside the textile fabrication process, instead of metal sheet and dielectric plastics, ceramics, etc. It is a challenge to build a robust capacitor for an environment subject to frequent deformations. Moreover, we must add the difficulty of detecting small changes in the capacity of considerably big surfaces, to which 50/60 Hz noise is easily joined up. Besides, detector electronics must communicate with a central system by the means of a wireless link, since this electronics must be built in inside the textile and it has to maintain hermetically protected. For this reason, a charging battery system based on inductive connection has been added. This system is protected by a European patent with reference EP20060725828.