DVB-RCS return link radio resource management for broadband satellite systems using fade mitigation techniques at ka band

Current Broadband Satellite systems supporting DVB-RCS at Ku band have static physical layer in order not to complicate their implementation. However at Ka band frequencies and above an adaptive physical layer wherein the physical layer parameters are dynamically modified on a per user basis is necessary to counteract atmospheric attenuation. Satellite Radio Resource Management (RRM) at the Medium Access Control (MAC) layer has become an important issue given the emphasis placed on Quality of Service (QoS) provided to the Users. The work presented here tackles the problem of Satellite RRM for Broadband Satellite systems using DVB-RCS where a fully adaptive physical layer is envisaged at Ka band frequencies. The impact of adaptive physical layer and user traffic conditions on the MAC layer functions is analyzed and an algorithm is proposed for the RRM process. Various physical layer issues associated with the resource management problem are also analyzed

Results from One Year of Ka-Band Beacon Measurements at Svalbard

Since April 1, 2016, a Ka-band (20.198 GHz) propagation terminal has been installed and operating at the Svalsat facility in Longyearbyen, Norway. This campaign is a joint effort between the European Space Agency (ESA), Kongsberg Satellite Services (KSAT), the French Aerospace Laboratory (ONERA), the Centre National d'Etudes Spatiales (CNES), and NASA Glenn Research Center (GRC) to characterize atmospheric attenuation, scintillation, and depolarization in the Ka-band in high latitude regions at low elevation angles. The propagation terminal observes the Thor 7 20.198 GHz RHCP beacon at nominally 2.6 deg elevation angle. Simultaneous 10 Hz and 1 Hz sampling is performed and a total dynamic range of 35 dB is achieved. One year of propagation data has been collected and the preliminary results are presented in this paper. From the first year of measurements, it is observed that at these low elevation angles, strong scintillation/multi-path conditions, as well as significant depolarization events can occur which may impose difficulties in meeting mission link acquisition requirements at 5 deg elevation angle, such as those desired by the Joint Polar Satellite System (JPSS) mission. The design of the dual-polarized terminal with integrated digital radiometer, as well as the data processing techniques are described, along with the first year results and preliminary conclusions

Smart gateways for terabit/s satellite

To reach the terabit per second of throughput, telecommunication satellites cannot make use of frequency below Ka band only. Therefore, the use of broad portion of the spectrum available at Q/V (40/50 GHz) band is foreseen for the feeder link. This study presents the evaluation of performances of different macro-diversity schemes that may allow mitigating the deep fades experienced at Q/V bands by introducing cooperation and a limited redundancy between the different gateways of the system. Two different solutions are firstly described. The performances resulting from the use of those assumptions are derived in a second stage

Comparison of multi-year Ka-band propagation characteristics at four sites in North America and Europe

Tropospheric phenomena such as clouds and mainly rain cause higher attenuation at Ka-band than at lower frequencies. In this collaborative paper, the main results of four long-term Ka-band propagation campaigns are presented. The experiments are carried out in Ottawa, Canada (satellite Anik F2); Aveiro, Portugal; Madrid, Spain; and Toulouse, France (satellite HotBird 6 in the last three cases) and have been running since 2004 in Aveiro, 2006 in Ottawa and Madrid, and 2008 in Toulouse. After a brief introduction of the experiments, rain rate and excess attenuation results are discussed, first for a common two-year measurement period and later for the whole database available. Seasonal attenuation statistics for Madrid, Ottawa and Aveiro are compared. Finally, fade duration and fade slope statistics derived at three locations are presented and discussed

The Satellite Communications Network of Excellence "SatNEx": Channel Modelling and Propagation Impairments Simulation Activities

SatNEx aims to rectify the fragmentation in satellite communications research by bringing together Europe’s leading academic institutions and research organisations in a cohesive and durable way. The resultant pan-European network provides a collective grouping of expertise and state-of-the-art laboratory facilities that would otherwise remain dispersed throughout Europe. This paper gives a brief introduction to the SatNEx project and to the activities related to channel modelling

Review of space–time tropospheric propagation models

International audienceThe increase of bandwidth needs fostered by growing data rate demand has triggered a shift of fixed-satellite links toward frequency higher than 20 GHz. A counterpart to the large bandwidth available at those frequency bands are strong propagation impairments in case of adverse weather conditions. Static power margins are inefficient to cope with the severe attenuation level that can be experienced in case of rain on the link. Thus, to cope with those strong propagation impairments, and maintain a satisfying level of link availability, fade mitigation techniques (FMTs) have been developed for satellite links as for instance: up-link power control, site diversity, onboard power adjustment, reconfigurable antennas, or adaptive coding and modulation (Panagopoulos et al., 2005)

Ka and Q band propagation experiments in Toulouse using ASTRA 3B and ALPHASAT satellites

International audienceFrom January 2008 to March 2011, ONERA operated in Toulouse, France, a beacon receiver able to collect the 19.7‐GHz beacon signal of the HotBird 6 satellite. In March 2011, the radio frequency chain was modified to be able to receive the 20.2‐GHz ASTRA 3B beacon to benefit from a higher Equivalent Isotropically Radiated Power of the satellite. Since June 2015, a second beacon receiver has been installed and is able to record the 39.4‐GHz beacon signal of the Alphasat satellite. The objective of this paper is to present the results of the first 2 years of measurements (June 2015 to May 2017) of the Q‐band Alphasat propagation experiment in Toulouse, as well as concurrent measurements collected at Ka‐band with ASTRA 3B. First of all, the propagation experiments are briefly described. Second, the results of the statistical analysis are highlighted. Finally, a deep analysis of the performances of the 2 frequency scaling prediction methods recommended in ITU‐R P.618‐13 is performed

Chapitre 3. Deux études de cas, de l’époque médiévale à l’Actuel

Après l’exemple du Sud-Ouest, nous avons choisi de présenter deux études de cas couvrant la même fenêtre temporelle, du Moyen Âge à l’époque contemporaine. Elles apportent un éclairage complémentaire aux modalités de l’urbanisation d’un fond de vallée soumis aux inondations. La première étude de cas se décline à la grande échelle d’un site urbain, la ville de Lille, qui se développe à partir de l’époque médiévale dans le fond d’une vallée humide aménagé par une petite rivière du Nord de la Fr..

Mise en évidence de complexes d'inclusion cyclodextrines/phosphines hydrosolubles et application à la réaction d'hydroformylation an milieu biphasique

La catalyse en milieu biphasique aqueux est un concept élégant dans lequel les catalyseurs homogènes, rendus hydrosolubles, se situent dans une phase organique. Ce procédé permet ainsi de récupérer quantitativament le catalyseur par simple décantation. Malheureusement, il ne peut être mis en œuvre dans le cas de réactifs totalement insolubles dans l'eau, car le transfert de matière entre les phases aqueuse et organique est insuffisant. Afin de résoudre ce problème, nous avons imaginé une approche originale basée sur l'utilisation de phosphines tensioactives et complexantes vis-à-vis des cyclodextrines. En effet, à basse température, le ligand tensioactif est piégé sous forme d'un complexe d'inclusion. Cette entité n'est pas tensioactive et les phases aqueuse et organique peuvent être facilement séparées. À haute température, le complexe se dissocie pour libérer le ligand tensioactif. La concentration micellaire critique est alors atteinte et une catalyse micellaire peut se développer. La formation d'un complexe d'inclusion entre la cyclodextrine et le ligand permettrait donc de générer, dans un domaine de température précis, des conditions favorables à une catalyse micellaire... Après une étude des complexes d'inclusion formés entre les cyclodextrines et les différents ligands tensioactifs, ce concept a été testé dans la réaction d'hydroformylation du déc-1-ène. Nous avons pu montrer que la cyclodextrine pouvait interagir avec le système catalytique et aboutir à la recyclabilité du catalyseur sous certaines conditions. Une étude RMN de l'interaction des cyclodextrines avec des complexes organométalliques à base de rhodium et de palladium a permis de montrer que les cyclodextrines sont capables de générer des espèces sous coordonnées en phosphine, ce qui permet d'obtenir le métal sous une forme plus active.LILLE1-BU (590092102) / SudocSudocFranceF

Propagation Experiment at Ka-Band in French Guiana: First Year of Measurements

International audienceONERA, the French Aerospace Lab, and CNES, the French Space Agency, are currently running a Ka-band propagation experiment at the Guiana Space Centre (CSG) in Kourou (French Guiana). A rain gauge and a beacon receiver able to record the 20.2 GHz beacon signal of the Amazonas 3 satellite have been deployed. The equipment is operational since January 1, 2017 and the duration of the experiment has been set to 3 years. This letter addresses some results of the first year of measurements (from January 2017 to December 2017). The annual and monthly Complementary Cumulative Distribution Functions of rainfall rate and rain attenuation are presented as well as a comparison with the rain attenuation prediction method recommended in ITU-R P.618-13