bluuebunny/crossref_metadata_2025_split huggingface dataset:
Architectures for the INTELSAT NISDN‐compatible satellite communications network
Authors: Chitre D. M. , Oei W. S. 
Published: July 2007

AbstractThis paper presents a conceptual description of a number of possible satellite network architectures for integration into and between the emerging narrowband 64 kb/s based integrated services digital networks (ISDNs). The discussion, which focuses on functional and architectural aspects of network‐integrated satellite systems, is based on two underlying themes. First, the satellite system, as a strict digital transmission system in international ISDN networks, must be virtually ISDN service transparent (i.e. it must not cause any unintended degradation to the transported signals and communication protocols). Secondly, the inherent features of satellite systems are exploited to offer additional functional network support to the ISDN network capabilities for select ISDN services.
250 MHz SAW FILTERS FOR SS/FDMA SYSTEM EMPLOYING ST‐CUT QUARTZ SUBSTRATES
Authors: Shinonaga Hideyuki , Ito Yasuhiko 
Published: July 2007

AbstractSurface acoustic wave (SAW) filters are key devices in developing the bandwidth‐variable filter matrix for the subchannel switched frequency division multiple access (SS/FDMA) system. This paper addresses the design and fabrication of two 250 MHz SAW filters employing temperature‐stable ST‐cut quartz substrates. The specafications for these filters are decided with due consideration of practical use by INTELSAT‐type satellites. Measured electrical responses of the individual and combined channels show satisfactory performance. Computer simulations are performed using the measured responses to assess the effects of the SAW filters on digital carriers. Finally, the effects of the temperature and ageing stability characteristics are discussed based on the measured and calculated responses.
Personal communications by satellite
Authors: Golding L. S. , Palmer L. C. 
Published: July 2007

AbstractPersonal communications (PC) refers to two‐way voice (and possibly data) communications to a small hand‐held unit, capable of being carried by a person and used in various locations. PC via satellite refers to the case where this hand‐held unit communicates directly with a satellite to provide the duplex voice (or data) service. Both geosynchronous earth orbit (GEO) and low earth orbit (LEO) satellites have been considered to provide this service. GEO and LEO satellite systems must compete with existing mobile cellular radio systems both in meeting performance requirements and service costs, if they are to be a significant supplier of PC services. GEO and LEO systems each have unique advantages and disadvantages when used to provide a PC service. While these general characteristics are identified in Section 1 of the paper, a more quantitative comparison is needed. This quantitative comparison is made by comparing a GEO PC satellite system, operating at EHF (Ka‐band) frequencies with a LEO system operating at UHF (L‐band) frequencies, including service costs for both systems. The two systems used in the comparison are examples of realistic GEO and LEO system designs for PC service, and although it is not exhaustive, the comparison points out some of the key differences between GEO and LEO systems that affect service performance and cost.
Multiple‐access phased array antenna simulator for A digital beam‐forming system investigation
Authors: Kerczewski Robert J. , Yu John , Walton Joanne C. , Perl Thomas D. , Andro Monty , Alexovich Robert E. 
Published: July 2007

AbstractFuture versions of data relay satellite systems are currently being planned by NASA. Being given consideration for implementation are on‐board digital beam‐forming techniques which will allow multiple users to simultaneously access a single S‐band phased array antenna system. To investigate the potential performance of such a system, a laboratory simulator has been developed at NASA's Lewis Research Center. This paper describes the system simulator, and in particular, the requirements, design and performance of a key subsystem, the phased array antenna simulator, which provides realistic inputs to the digital processor including multiple signals, noise and non‐linearities.
Static and dynamic retransmission control for slotted aloha in transmission channels with erasure and capture
Authors: Böttcher Axel , Meier‐Hedde Christoph 
Published: July 2007

AbstractSlotted Aloha can be an attractive multiple access scheme for mobile radio applications, mainly for mobile satellite services. This is especially so when capture‐effects occur, i.e. when one out of several colliding data packets can capture the common receiver. Mostly this is due to varying signal levels of the transmitters. It is well‐known that a slotted Aloha channel can become unstable. It performs acceptably only if a good retransmission control policy is applied. In this paper, static and dynamic stabilization methods for slotted Aloha in transmission channels with capture and erasure are compared. They are analysed by analytical methods as well as by simulation. It turns out that a dynamic control procedure is more flexible and outperforms a static retransmission policy also in mobile radio channels.
Orbital performance of communication satellite microwave power amplifiers (MPAs)
Authors: Strauss R. 
Published: July 2007

AbstractThis paper presents background data on the performance of microwave power amplifiers (MPAs) used as transmitters in currently operating commercial communication satellites. Specifically, aspects of two competing MPA types are discussed. These are the well known TWTA (travelling wave tube amplifier) and the SSPA (solid state power amplifier). Extensive in‐orbit data has been collected from over 2000 MPAs in 1991 and 1993. The study in 1991 involved 75 S/C (spacecraft) covering 463 S/C years. The 1993 ‘second look’ study encompassed a slightly different population of 72 S/C with 497 S/C years of operation. A surprising result of both studies was that SSPAs, although quite reliable, did not achieve the reliability of TWTAs. TWTAs were one‐third more reliable in the 1993 study. This was atC‐band with comparable power amplifiers, e.g. 6‐16W of RF output power and similar gains. Data atKu‐band is for TWTAs only since there are no SSPAs in the current S/C inventory. The other complementary result was that the projected failure rates used as S/C payload design guidelines were, on average, somewhat higher for TWTAs than the actual failure rates uncovered by this study. SSPA rates were as projected.
A co‐designed coding, modulation and equalization scheme for the transmission of 155‐52 Mbit/s data over a 72 MHz intelsat transponder. Part 1: Coding and modulation performance
Authors: Peile R. E. 
Published: July 2007

AbstractThis paper reports on the application of co‐designed coding, modulation and equalization techniques to an INTELSAT requirement for transmitting 155‐52 Mbit/s data over a 72 MHz satellite channel. A specific solution as regards coding, modulation and equalization is proposed and analysed that differs from ‘standard’ concatenation in that the inner decoder integrates equalization, modulation and coding. In Part 1 results of extensive computer simulations are presented, examining the effect of adjacent channel interference, co‐channel interference, non‐linear distortion in representative ground and space TWTAs, multiplexers and filter distortion. In Part 2 a novel technique for integrating decision feedback equalization into the inner decoder is described. The gains in integrating the coding and equalization are shown to be significant for channels that need equalizing.
Performance analysis of A dynamic channel allocation technique for satellite mobile cellular networks
Authors: Re Enrico Del , Fantacci Romano , Giambene Giovanni 
Published: July 2007

AbstractThis paper deals with an efficient dynamic channel allocation (DCA) technique suitable for applications in mobile satellite cellular networks. A cost function is defined to allow an optimum selection of channels to be allocated on demand. A mobility model suitable for low earth orbit (LEO) satellite systems is presented. The performance of the novel DCA technique in terms of call blocking probability has been derived by simulations. The obtained results are compared with those achieved by a fixed channel allocation (FCA) technique to show a better behaviour.
Network and common channel signalling aspects of dynamic satellite constellations
Authors: Cullen C. , Benedicto X. , Tafazolli R. , Evans B. 
Published: July 2007

AbstractThis paper discusses networking issues associated with the provision of L/S‐band personal satellite communications. Both the UMTS and IMT‐2000 third generation mobile communication concepts have identified the need for a satellite component as part of their overall structure. The work is mostly based on the ESA‐developed medium altitude global satellite system (MAGSS‐14).1 It is, therefore, mainly relevant to MEO (medium earth orbit) constellations but most ideas can also be extended to LEO (low earth orbit) constellations. After examining user and service requirements the specific networking issues associated with personal satellite communications are reviewed. A network architecture is then proposed which takes these restrictions into account. Based on this network architecture, network signalling requirements, more specifically those relevant to network common control channels, are estimated.
Analysis of A movable boundary access technique for A multiservice multibeam satellite system
Authors: Bohm S. , Elhakeem A. K. , Murthy K. M. S. , Hachicha M. , Kadoch M. 
Published: July 2007

AbstractIn this paper, the performance of a new movable boundary accessing (MBA) technique for future integrated services multibeam satellite systems is studied. The multiservice environment considered includes both asynchronous and isochronous traffic consisting of video, voice, file transfer and interactive data. The movable boundary access technique proposed here will maximize the utilization of the uplink frame capacity. It is shown that the potential user population is substantially increased with the use of a moving boundary policy with minimal overhead.
The BMLA/LS technique and its application in A mobile satellite communication channel
Authors: Liu Yi‐Song 
Published: July 2007

AbstractThe burst mode link analyser with least squares algorithm (BMLA/LS) is a real‐time impulse or frequency response extraction (IRE/FRE) technique of a satellite communication channel, originated and explored by the author. This paper summarizes some key technical points of the BMLA/LS and presents its novel simulation results and applications in a land‐mobile DBPSK/DQPSK satellite channel at Ka‐band, including the channel additive white Gaussian noise (AWGN) effect on IRE/FRE by BMLA/LS, and the instantaneous IRE/FRE in a Rician channel with multi‐path reflection, in a shadowed channel by trees and in a combinational fading channel, and their comparisons and conclusions.
Space flight tests of attitude determination using GPS
Authors: Cohen Clark E. , Lightsey E. Glenn , Parkinson Bradford W. , Feess William A. 
Published: July 2007

AbstractPreliminary space flight results of attitude determination using GPS are presented from a spacecraft in low Earth orbit. Relative position measurements accurate to the sub‐centimetre level are made among multiple GPS antennas mounted on the space vehicle. A Trimble Navigation TANS Quadrex (a GPS receiver specially adapted for attitude determination by Stanford University) is used as a differential carrier phase sensor for the flight.Four GPS antennas are mounted on the zenith face of RADCAL, a polar orbiting, gravity‐gradient‐stabilized Air Force Space Test Program Satellite, built by Defense Systems, Inc. The four antennas are equally spaced about the perimeter of the 30 inch diameter cylindrical spacecraft bus.The Quadrex receiver measures the phase of the L‐band GPS carrier (1575 MHz) at each of up to four antennas for up to six GPS satellites simultaneously. From these measurements, an initial assessment of attitude determination in space is performed in post‐processing. For RADCAL, the attitude solution is greatly overdetermined. In a preliminary evaluation of system performance, the system accuracy is determined through measurement self‐consistency. Analysis of the attitude motion in the context of a gravity gradient dynamic model yields further insight into the system performance.
The intelsat VIII/VIIIA generation of global communication satellites
Authors: Cornelius D. J. , Herridge A. J. , Silk R. , Thompson P. T. 
Published: July 2007

AbstractDeveloped originally to meet increased demand forecast for C‐band capacity in the Pacific Ocean Region (POR), this latest generation of INTELSAT satellites is planned to be operated in a number of traditional and new roles. To date INTELSAT has bought four INTELSAT VIII spacecraft for Pacific, Indian and Atlantic Ocean regions and two modified VIII‐A to meet the specific Landmass requirements for the rapidly expanding Asia‐Pacific and pan‐American market. The VIII spacecraft, using Martin Marietta Astro Space's GS7000 bus has sufficient power and payload carrying capability that it can accommodate a wide variety of services. A new feature for INTELSAT is the inclusion of arcjet propulsion which has the potential for long lifetime while needing only half of the fuel requirement of conventional thrusters. This new high power satellite will form a key part of the INTELSAT global network through to the year 2010 and complement the INTELSAT VII and VIIA series.
Modelling of the rainfall rate cumulative distribution for the design of satellite and terrestrial communication systems
Authors: Moupfouma F. , Martin L. 
Published: July 2007

AbstractThe design of line of sight (L.O.S.) or satellite links requires annual point rainfall rate statistics for several percentages of time in the locations where the radiocommunication links are planned. Rain rate data within an average year, indeed, allow the estimation of the time percentage during which attenuation due to rain is significant, and consequently the future link margin.To meet ITU Radiocommunication Sector's Recommendations, we propose a probability law model allowing the prediction of the rainfall rate cumulative distribution in temperate and tropical climates.This model, which can be easily used, may serve as a very useful and accurate enough tool for radiocommunication engineers and scientists.
Interference considerations in frequency sharing between low earth orbit satellites and the geostationary fixed satellite and terrestrial service
Authors: James Michel C. 
Published: July 2007

AbstractRecently many companies and consortia have considered launching LEO satellites for such projects as remote sensing, transportation and mining operations. When the multiple low Earth orbit (LEO) satellites are transmitting they can interfere with existing terrestrial microwave and satellite earth‐stations in the fixed and mobile service. The interference problem is related to the number of proposed LEOs and the altitude and consequently the time to orbit the earth. These systems usually consist of many small satellites, and each satellite stays in the beam of a terrestrial station for up to 72 seconds in each 222 minute orbit. Earth coverage could be obtained by 48 (LEO) satellites 1500 km above the earth in polar orbit, and hence at least one LEO would always be interfering with terrestrial networks. A technical evaluation would then be required to determine the resultant BER (bit error rate) effecting existing terrestrial services. A determination can then be made to support such a LEO system or object via official channels such as the ITU.
Planning aspects of satellite and terrestrial digital sound broadcasting
Authors: Sauvet‐Goichon Daniel 
Published: July 2007

AbstractDAB is one of the most promising sound broadcasting techniques for the future. It will soon start terrestrial operations, and later on will be used for satellite broadcasting.The Eureka 147 DAB system is based on a set of well‐demonstrated techniques, in particular the MUSICAM coding, adopted by MPEG, and OFDM modulation. It allows great spectrum efficiency, profiting from the single frequency network concept, one of the most interesting characteristics of the system.However, frequency problems remain a difficulty, as DAB must either examine the possibility of entering existing heavily used frequency bands or wait until the new frequency bands allocated by WARC 92 become fully available.For terrestrial broadcasting, most interested operators, broadcasters and manufacturers are convinced that appropriate solutions will be found and that DAB will start operational services from about 1996. In Europe, a CEPT planning conference will address the matter in 1995.Satellite broadcasting may come later. Short wave broadcasters examine possibilities to replace short waves, the quality of which is so poor, by digital satellite broadcasting. From the frequency spectrum point of view, this raises the difficulty of sharing frequency allocations with terrestrial applications.
In‐orbit test of the first Hughes United States direct broadcast satellite
Authors: Egly Keith , Leacock Rick , Riginos Vasilis 
Published: July 2007

AbstractThis paper describes the in‐orbit test of the first United States direct broadcasting satellite (DBS‐1) developed by Hughes Space and Communications (HSC) for Hughes Communications Galaxy, Inc. and DIRECTV Inc. This satellite provides direct broadcast of digitally compressed television channels across the United States for service providers DIRECTV™ and United States Satellite Broadcasting (USSB).Following a brief description of the communication system of the spacecraft, the in‐orbit test set‐up and the measurements that were performed are described. Measurements which have not been described elsewhere (antenna contour verification, modulated e.i.r.p., e.i.r.p. with wide band energy dispersal function (EDF), auto saturation, etc.) are covered in some detail.Finally, the results of the in‐orbit test of DBS‐1 which was performed in January 1994 are presented.
Two‐station in‐orbit testing using swept techniques
Authors: Cradock Robert 
Published: July 2007

AbstractThis paper describes the system, consisting of hardware and software, and two of the two‐station in‐orbit test (IOT) measurements that were developed for INTELSAT as part of their IOTE (in‐orbit test equipment) project. Three systems have been designed and manufactured by SED Systems, and installed in Beijing, Clarksburg and Fucino. The system is capable of two types of synchronized sweeps: sweeps in power and sweeps in frequency; gain transfer and frequency response, respectively, are given as examples. Two‐station measurements are used on complex satellites that contain transmit and receive beams (such as spot beams) that cannot both be seen at the same earth‐station. This paper briefly describes how the measurements are done and discusses some of the more important performance issues.
Open loop testing of communication satellites from two in‐orbit test (IOT) stations
Authors: De Vincenti P. , Kasstan B. , Paris D. , Riginos V. , Shen P. , Absolonne F. A. , Stjernevic J. 
Published: July 2007

AbstractThe implementation of the IOT for the EUTELSAT II‐F6 (HOT BIRD 1) spacecraft is based on the new concept of an ’open loop measurements‘ architecture connecting two IOT stations geographically separated. This architecture was implemented because the EUTELSAT test facilities in Rambouillet near Paris could not transmit in the 13 GHz band required by the HOT BIRD 1 up‐link. The up‐link carriers were thus provided by the ex‐Olympus IOT antenna situated at the ESA facilities in Redu, Belgium, whereas all the down‐link measurements and the test management were performed by the EUTELSAT test facility in Rambouillet. The two IOT stations were mutually connected by a dedicated data transmission line.The paper describes the changes that were made to the existing EUTELSAT and ESA facilities and the implementation of the new measurement software and of specific networking equipment, such as the remote server that was installed at Redu to control the up‐link signals from the Rambouillet site.The paper also discusses the implementation of new satellite test procedures for remote measurements and in particular how the spacecraft channel group delay is measured from two independent stations in open loop mode.
Choice of λ‐Margin and dependency of non‐inferiority trials
Authors: Tsong Yi , Levenson Mark , Zhang Joanne , Zhong Jinglin 
Published: July 2007

AbstractFor a two‐arm active control clinical trial designed to test for non‐inferiority of the test treatment compared with the active control standard treatment, data of historical studies are often utilized. For example, with a cross‐trial comparison approach (also called synthetic approach or λ‐margin approach), the trial is conducted to test the hypothesis that the mean difference or the ratio between the current test product and the active control is no larger than a certain portion of the mean difference or the ratio of the active control and placebo obtained in
the historical data when the positive response indicates treatment effectiveness. The regulatory agency usually requires that the clinical trials of two different test treatments are independent in most regular cases. It also requires, in general, two independent trials of the same test treatment in order to provide confirmatory evidence of the efficacy of the test product. In this article, we derived the relationship between the correlation of the test statistics of two trials with the choice of λ (the percentage to preserve), the sample sizes and variances under the normality assumption. We showed that the smaller a λ, the higher the correlation between the two non‐inferiority tests. It is further shown that when an 80 per cent or larger λ is used, the correlation can be controlled to be less than 10 per cent if the variances of the response variables in the current trial are not much smaller than those of the historical studies. Published in 2007 by John Wiley & Sons, Ltd.
Flavor reversion in soybean oil. V. Isolation and identification of reversion compounds in hydrogenated soybean oil
Authors: Schepartz A. I. , Daubert B. F. 
Published: July 2007

SummaryA reinvestigation of the deodorization condensates obtained from reverted, hydrogenated soybean oil has been made. The flavor materials were further concentrated by vacuum distillation at room temperature and by separation into neutral and acid fractions.Qualitative tests indicated that the flavor components were mainly α,β‐unsaturated carbonyls.Hydrogenation of the fractions possessing flavors destroyed the α,β‐unsaturated carbonyls as well as the flavors. Oxidation of the carbonyls to the corresponding acids gave similar results.Three compounds were isolated as the 2,4‐dinitrophenylhydrazones. They were identified as maleic dialdehyde, di‐n‐propyl ketone, and 2‐heptenal by the use of physical as well as chemical data.A possible mechanism for the formation of two of these compounds from fatty acid precursors has been indicated.
Studies on surface activity of linear alkylbenzene sulfonates II: Effect of water hardness
Authors: Kumar Raj , Bhat S. G. T. 
Published: July 2007

AbstractAdsorption behavior of a mixture of homologs and isomers of sodium linear alkylbenzene sulfonates from their aqueous solutions in hard water at the solution/air interface has been investigated. Increasing the concentration of surfactant in hard water results in the precipitation of the surfactant, which starts redissolving in the solution with further increases in surfactant concentration beyond a certain value characteristic of the surfactant, and finally results in a clear solution. Surface tension versus the logarithm of concentration curves shows an unusual behavior of multiple breaks. Attempts have been made to explain the results in terms of the equilibrium existing among the different forms of the surfactant, namely monomer, precipitate and the micelle.