Fractal geometry has been proven to be useful in several disciplines. In the field of antenna engineering, fractal is design small and multiband arrays, high-directive elements. A historic overview most significant mathematic pioneers presented, at same time showing how patterns inspired engineers antennas.

The deployment of wireless devices has increased exponentially in recent years, not only for mobile applications but also IoT. Typically, these IoT exchange data with other by means connections, where battery consumption depends on the antenna system’s efficiency. In long life and reliable transmission are essential, improving efficiency is crucial. This study aims to investigate how shaping ground plane a device can enhance bandwidth efficiency, specifically low-frequency bands 824–960 MHz,...

Since 2003, our group has been investigating the performance of different transmission techniques for low‐power low‐interference High Frequency (HF) ionospheric communication systems. Specifically, we have focused on link between Spanish Antarctic Station (SAS) Juan Carlos I in Livingston Island and Ebro Observatory (OE) Spain, order to transmit data gathered from some geomagnetic sensors. These require a valuable knowledge channel behavior, thus comprehensive narrowband wideband sounding is...

This paper presents two digital transmission techniques for long haul ionospheric links. Since 2003 we have studied the HF link between Antarctic Spanish Base, Juan Carlos I, and Spain; described in terms of availability, signal-to-noise ratio, delay Doppler power profile. Based on these previous studies developed a test bed to investigate techniques, i.e., Direct-Sequence Spread Spectrum (DSSS) Orthogonal Frequency Division Multiplexing (OFDM), which can provide low power, low-rate data...

Skywave ionospheric communication systems offer a good choice to satellite communications when transmitting from the poles. For last 10 years authors have been sounding and testing modulations through 12 700 km high frequency link Spanish Antarctic Station Spain. Previous tests comparing direct sequence spread spectrum (DS‐SS) orthogonal division multiplexing (OFDM) showed that bit rate error (BER) results outperformed OFDM at expense of lower rates. In this study present three techniques...

Our research group in Electromagnetism and Communications is involved a project dealing with the channel characterization of an ionospheric radio link from Spanish Antarctic Base (62.6°S, 60.4°W) to Observatori de l'Ebre (40.8°N, 0.5°E) Spain. Since was established for first time on December 2003, sounder measurement techniques have been improved basis preliminary results. In this paper, final results corresponding 2006/2007 sounding survey are presented. First hardware used probe described....

One of the major drawbacks multicarrier modulation is large envelope fluctuations which either requires an inefficient use high power amplifiers (HPAs) or decreases system performance. Peak-to-average ratio (PAPR) best known measure and widely employed to design systems. However, recently, another metric as cubic (CM), being considered in several systems since it can predict HPA de-rating more accurately. In this paper tone reservation (TR) technique, originally used for PAPR-reduction,...

The increase in the IoT (Internet of Things), such as trackers and sensors, puts pressure on device dimensions performance. This is translated to antenna system since it has be both efficient provide operation across different frequency bands. However, these antennas must also small enough fit into limited space available wireless devices. To address this challenge, a reconfigurable architecture with single SP4T (Single-Pole 4-Throw) operating at 698 MHz -960 1710 -2170 proposed, designed,...

La Salle and Ebro Observatory have been involved in remote sensing projects Antarctica for the last 11 years (approximately one solar cycle). The has monitoring analyzing geomagnetic ionospheric activity Antarctic Spanish station Juan Carlos I (ASJI) (62.7°S, 299.6°E) more than eighteen ten years, respectively. two main goals project. first is data transmission reception from to Spain obtain a historical series of measurements channel sounding this 12,760-km HF (high frequency) radio link....

La Salle and the Observatori de l’Ebre (OE) have been involved in a remote sensing project Antarctica for last 11 years. The OE has monitoring geomagnetic activity more than twenty years also ionospheric of ten Spanish Antarctic Station Juan Carlos I (ASJI) (62.7 ° S, 299.6 E). is finishing design testing low-power communication system between ASJI Cambrils (41.0 N, 1.0 E) with double goal: (i) transmission data from sensors located at (ii) performance an oblique sounding 12,760 km HF link....

Power-line communications (PLC) technologies rely on the power grid for data transmission. Since channel is already deployed, this communication alternative specially interesting owner (i.e., electrical utility). The medium-voltage (MV) distribution network, located after last step-down substation with typical levels from 6 to 25 kV, directly feeds large consumers and small ones through several transform stations. growing interest MV-PLC technology, natural aggregation point coming going...

Abstract This paper presents a comparative study between the oblique sounding results, International Telecommunication Union Rec533 HF prediction model, and vertical results of transequatorial long haul link. The link is 12,760 km Spanish Antarctic Station, SAS, located in Livingston Island Ebro Observatory (OE) Spain. data were collected during three consecutive surveys (2009/2010, 2010/2011, 2011/2012). ionospheric channel from SAS to OE studied terms frequency availability as function...

A vertical incidence sounder (VIS) was installed at the Spanish Antarctic Base (62.7°S, 299.6°E) during summer survey 2004–2005. In addition, an oblique sounding (OS) system for HF communications between Antarctica and Spain (12,700 km) has been operated summers since December 2003. OS results are compared to Rec533 model VIS data obtained from stations located along radio path, including emitter receiver sites. The presented in this paper show potential of infrastructure ionospheric...

Abstract A heterogeneous sensor network offers an extremely effective means of communicating with the international community, first responders, and humanitarian assistance agencies as long affected populations have access to Internet during disasters. When communication networks fail in emergency situation, a challenge emerges when services try communicate each other. In such situations, field data can be collected from nearby sensors deploying wireless delay-tolerant over region monitor....

High-voltage (HV) power lines have been used as a communications medium since the 1920s. Those point-to-point links were typically based on single-sideband amplitude modulation. These days, state of art in HV power-line carrier (PLC) comprises combination analog systems, mainly for teleprotection tasks, and digital voice data transmission. Beside traditional core services (monitoring, operation management, limitation removal failures), electrical utilities would like to satisfy increasing...

A single carrier frequency domain equalisation (SC‐FDE) modulation scheme which represents a step forward in the investigation since it obtains higher bit rates than previous proposals with spread spectrum techniques is presented. The focus of this reported work data transmission from remote sensors using very low‐power HF ionospheric communications. In particular, authors' research group has been studying channel parameters and Antarctica 2003. Both, multicarrier modulations have tested...

OFDM (orthogonal frequency division multiplexing) has emerged as one of the best modulations for broadband mobile communications. Despite its robustness against multipath interference, drawback peak-to-average power ratio (PAPR) to be overcome. PAPR increases A/D and D/A complexity reduces high amplifier efficiency well battery life. A new technique reducing modulation is presented. This method does not spread signal bandwidth, it scarcely computational no additional information known by receiver.

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 monitoring. High-frequency (HF) communications are presented as an alternative to satellite communications, being a low-cost easy-to-deploy solution. Near vertical incidence skywave (NVIS) technology provides coverage approximately 250 km (depending on the frequency used ionospheric conditions) without...

The orthogonal frequency division multiple access (OFDMA) scheme has been selected as a potential candidate for many emerging broadband wireless standards. In this paper, new joint scheduling and resource allocation is proposed the OFDMA systems using contiguous subcarrier permutation. algorithm provides sets of frequency-time units following rectangular shape yielding reduction on required burst signalling. process divided into two phases: QoS requirements fulfilment input buffers emptying...