A design strategy for phase synchronization in precoding-enabled DVB-S2X user terminals

This paper address the design of a phase tracking block for the DVB-S2X user terminals in a satellite precoding system. The spectral characteristics of the phase noise introduced by the oscillator, the channel, and the thermal noise at the receiver are taken into account. Using the expected phase noise mask, the optimal parameters for a second-order PLL intended to track channel variations from the pilots are calculated. To validate the results a Simulink model was implemented considering the characteristics of the hardware prototype. The performance of the design was evaluated in terms of the accuracy and stability for the frame structure of superframe Format 2, as described in Annex E of DVB-S2X.This work was supported by the Fond National de la Recherche Luxembourg, under the CORE project COHESAT: Cognitive Cohesive Networks of Distributed Units for Active and Passive Space Applications and the Bridges Program DISBuS: Dynamic Beam Forming and In-band Signalling for Next Generation Satellite Systems.Peer ReviewedPostprint (author's final draft

SDR implementation of a testbed for synchronization of coherent distributed remote sensing systems

Remote Sensing from distributed platforms has become attractive for the community in the last years. Phase, frequency, and time synchronization are a crucial requirement for many such applications as multi-static remote sensing and also for distributed beamforming for communications. The literature on the field is extensive, and in some cases, the requirements an complexity of the proposed synchronization solution may surpass the ones set by the application itself. Moreover, the synchronization solution becomes even more challenging when the nodes are flying or hovering on aerial or space platforms. In this work, we discuss the synchronization considerations for the implementation of distributed remote sensing applications. The general framework considered is based on a distributed collection of autonomous nodes that synchronize their clocks with a common reference using inter-satellite links. For this purpose, we implement a synchronization link between two nodes operating in a full-duplex fashion. The experimental testbed uses commercially available SDR platforms to emulate two satellites, two targets, and the communication channel. The proposal is evaluated considering phase and frequency errors for different system parameters.This work was supported by the Fond National de la Recherche Luxembourg, under the CORE project COHESAT: Cognitive Cohesive Networks of Distributed Units for Active and Passive Space Applications.Peer ReviewedPostprint (author's final draft

A Cubesat-ready phase synchronization digital payload for coherent distributed remote sensing missions

Distributed antenna arrays, fractionated payloads and cooperative platforms can provide unprecedented performance in the next generation of spaceborne communications and remote sensing systems. Remote phase synchronization of physically separated oscillators is the first step towards a coherent operation of distributed systems. This work shows the preliminary results of a TDD remote phase synchronization algorithm with a master-follower architecture. Herein, we describe the implementation and validation of the proposed algorithm. The implementation has been conducted in a Cubesat-ready software defined radio and validated at the end-to-end satellite communications testbed available at the University of Luxembourg.This work was supported by the Fond National de la Recherche Luxembourg, under the CORE project COHESAT: Cognitive Cohesive Networks of Distributed Units for Active and Passive Space Applications.Peer ReviewedPostprint (author's final draft

Architectures and synchronization techniques for distributed satellite systems: a survey

Cohesive Distributed Satellite Systems (CDSSs) is a key enabling technology for the future of remote sensing and communication missions. However, they have to meet strict synchronization requirements before their use is generalized. When clock or local oscillator signals are generated locally at each of the distributed nodes, achieving exact synchronization in absolute phase, frequency, and time is a complex problem. In addition, satellite systems have significant resource constraints, especially for small satellites, which are envisioned to be part of the future CDSSs. Thus, the development of precise, robust, and resource-efficient synchronization techniques is essential for the advancement of future CDSSs. In this context, this survey aims to summarize and categorize the most relevant results on synchronization techniques for Distributed Satellite Systems (DSSs). First, some important architecture and system concepts are defined. Then, the synchronization methods reported in the literature are reviewed and categorized. This article also provides an extensive list of applications and examples of synchronization techniques for DSSs in addition to the most significant advances in other operations closely related to synchronization, such as inter-satellite ranging and relative position. The survey also provides a discussion on emerging data-driven synchronization techniques based on Machine Learning (ML). Finally, a compilation of current research activities and potential research topics is proposed, identifying problems and open challenges that can be useful for researchers in the field.This work was supported by the Luxembourg National Research Fund (FNR), through the CORE Project COHEsive SATellite (COHESAT): Cognitive Cohesive Networks of Distributed Units for Active and Passive Space Applications, under Grant FNR11689919.Award-winningPostprint (published version

Elevación del ST en aVR y su valor pronóstico a corto plazo en el Infarto Agudo del Miocardio.

Introducción: Numerosos factores se relacionan con las complicaciones intrahospitalarias en el Infarto Agudo de Miocardio (IMA). La utilidad del segmento ST en aVR como factor pronóstico es polémica actualmente. Objetivo: Evaluar el valor pronóstico a corto plazo de la elevación del segmento ST en aVR en pacientes con IMA. Métodos: Estudio observacional, analítico y transversal, con 112 pacientes con IMA en el Hospital Militar Central: Dr. Carlos J. Finlay en 2 años. Fueron definidos como eventos adversos: Muerte, insuficiencia cardiaca (IC), angina post IMA, arritmias, shock y todos combinados (ECAM). Se crearon grupos, utilizando el ST en aVR y valor de corte < 1 mm y ≥ 1 mm. Resultados: El sexo masculino (60,7%), la hipertensión arterial (87,5%), el tabaquismo (65,2%) y la topografía inferior fueron las características basales prevalentes. El 33,0% presentó ECAM, siendo la ICC (37,8%) y la angina post IMA (19,0%) los más documentados. La ICC se asoció con aVR ≥ 1mm (p= 0,000). El ST en aVR ≥ 1mm constituyó un predictor independiente de ECAM (p=0,048; IC: 3,898-32,908). Conclusiones: En pacientes con IMA, el ST en aVR ≥ 1mm está asociado a peor evolución clínica intrahospitalaria

Effects of differential oscillator phase noise in precoding performance

Satellite Precoding is a promising technique to meet the target data rates of the future high throughput satellite systems and the costs per bit as required by 5G applications and networks, but it requires strict synchronization among the transmitted waveforms, in addition to accurate channel state information. Most of the published work about this topic consider ideal oscillators, but in practice, the output of an oscillator is not a single spectral line at the nominal frequency. This paper proposes a model for the oscillator phase noise and analyzes the resulting received signal to interference plus noise ratio (SNIR) in a satellite communication system using Precoding. Simulations of a communication satellite system with a two-beam transponder and two receivers were performed to compute the effective SNIR. This work uses a simulator which also considers practical impairments such as time misalignment, errors in the channel state information, interference, thermal noise and phase noise masks for satellite oscillators. The Precoding methods used for the analysis are Zero Forcing (ZF) and Minimum Mean Square Error (MMSE). The obtained results prove that there is a degradation in the performance due to the use of independent oscillators but this effect is compensated by the precoding matrix.Peer Reviewe

Effects of differential oscillator phase noise in precoding performance

Satellite Precoding is a promising technique to meet the target data rates of the future high throughput satellite systems and the costs per bit as required by 5G applications and networks, but it requires strict synchronization among the transmitted waveforms, in addition to accurate channel state information. Most of the published work about this topic consider ideal oscillators, but in practice, the output of an oscillator is not a single spectral line at the nominal frequency. This paper proposes a model for the oscillator phase noise and analyzes the resulting received signal to interference plus noise ratio (SNIR) in a satellite communication system using Precoding. Simulations of a communication satellite system with a two-beam transponder and two receivers were performed to compute the effective SNIR. This work uses a simulator which also considers practical impairments such as time misalignment, errors in the channel state information, interference, thermal noise and phase noise masks for satellite oscillators. The Precoding methods used for the analysis are Zero Forcing (ZF) and Minimum Mean Square Error (MMSE). The obtained results prove that there is a degradation in the performance due to the use of independent oscillators but this effect is compensated by the precoding matrix.Peer ReviewedPostprint (author's final draft

Embolismo mesentérico tras cardioversión eléctrica en paciente con policitemia vera. Papel del intervencionismo endovascular

La policitemia vera ocasiona complicaciones trombóticas. La tromboembolia mesentérica presenta alta mortalidad por lo que se debe restablecer la circulación intestinal. La cirugía abierta es habitual pero con alta mortalidad y las terapias endovasculares se emplean exitosamente en la actualidad en países desarrollados. Cuba presenta avances en el intervencionismo coronario no así en otros escenarios vasculares quedando estas técnicas destinadas a pocos centros. Describimos un caso con policitemia vera y taquicardia ventricular, que tras cardioversión eléctrica, presentó embolismo mesentérico. Realizamos abordaje endovascular. Posteriormente se presentó recurrencia del cuadro y en laparotomía exploratoria se apreció trombosis de stents y necrosis intestinal ocasionando la muerte

Embolismo mesentérico tras cardioversión eléctrica en paciente con policitemia vera. Papel del intervencionismo endovascular

La policitemia vera ocasiona complicaciones trombóticas. La tromboembolia mesentérica presenta alta mortalidad por lo que se debe restablecer la circulación intestinal. La cirugía abierta es habitual pero con alta mortalidad y las terapias endovasculares se emplean exitosamente en la actualidad en países desarrollados. Cuba presenta avances en el intervencionismo coronario no así en otros escenarios vasculares quedando estas técnicas destinadas a pocos centros. Describimos un caso con policitemia vera y taquicardia ventricular, que tras cardioversión eléctrica, presentó embolismo mesentérico. Realizamos abordaje endovascular. Posteriormente se presentó recurrencia del cuadro y en laparotomía exploratoria se apreció trombosis de stents y necrosis intestinal ocasionando la muerte

A remote carrier synchronization technique for coherent distributed remote sensing systems

Phase, frequency, and time synchronization are crucial requirements for many applications, such as multistatic remote sensing and communication systems. Moreover, the synchronization solution becomes even more challenging when the nodes are orbiting or flying on airborne or spaceborne platforms. This article compares the available technologies used for the synchronization and coordination of nodes in distributed remote sensing applications. Additionally, this article proposes a general system model and identifies preliminary guidelines and critical elements for implementing the synchronization mechanisms exploiting the intersatellite communication link. The distributed phase synchronization loop introduced in this work deals with the self-interference in a full-duplex point to point scenario by transmitting two carriers at each node. All carriers appear with different frequency offsets around a central frequency, called the application central-frequency or the beamforming frequency. This article includes a detailed analysis of the proposed algorithm and the required simulations to verify its performance for different phase noise, additive white Gaussian noise, and Doppler shift scenarios.This work was supported in part by the Fond National de la Recherche Luxembourg, under the CORE projects COHESAT: Cognitive Cohesive Networks of Distributed Units for Active and Passive Space Applications, and in part by 5G-SKY.Peer ReviewedPostprint (published version