bluuebunny/crossref_metadata_2025_split huggingface dataset:
The system implications of 6/4 ghz satellite‐to‐ground signal depolarization results from the intelsat propagation measurement programme
Authors: Allnutt J. E. 
Published: July 2007

AbstractThe results of six experiments to measure 6/4 GHz signal depolarization are presented. The measurement sites varied from the tropics to 57°N latitude and elevation angles between 12° and 38° were employed. In two of the experiments, simultaneous measurements at 6 GHz and 4 GHz were made along the same path to measure the correlation between the depolarizations occurring at the two frequencies.It was found that, in all cases, rain was the dominant depolarizing mechanism. Where the occurrence of ice depolarization was significant the magnitude of the ice depolarization occurring was not system limiting on a statistical basis. The correlation between up‐link and down‐link depolarization occurring along the same path was found to be very good both on an instantaneous basis and a statistical basis. The use of open‐loop up‐link depolarization compensation mechanisms should therefore be feasible. An examination of the depolarization fluctuation spectra obtained in some severe depolarizing events during one of the experiments would indicate that the settling time for such a mechanism should be on the order of 1 s. The use of simple, ‘non‐perfect’, depolarization compensation mechanisms allied to a low‐cost, spectrally efficient FEC system may prove to be the best compromise in some locations that experience severe depolarization.
Investigation of 9.6 kb/s data transmission via a pcm link at 64 kb/s with and without link errors
Authors: Suyderhoud H. , Corcoran F. L. , Arnstein D. S. , Lewis H. 
Published: July 2007

AbstractThe problem of pulse code modulation (PCM) bit errors causing voice frequency (VF) modem errors has been studied in detail. The error mechanism consists of the addition of an impulse response type error signal added to the reconstructed VF data signal waveform at the digital‐to‐analogue (D/A) output of the PCM decoder. This error signal may cause a burst of errors registering in the VF modem receiver, depending on which PCM bit is in error.Numerous data have been collected in a laboratory experiment and analysed in various ways. The average bit error rate (BER) enhancement factor of VF data over PCM is between 10 and 20. For each PCM bit in error, an average of two VF data bits are in error. The analysis leads to suggestions for possible solutions to the problem.
Estimating the mass and power of communications satellites
Authors: Pritchard Wilbur L. 
Published: July 2007

AbstractThe importance of weight and power estimates and methods for obtaining them are discussed. A method sufficiently accurate for system and launch vehicle planning is developed. It starts from operational requirements such as numbers of transponders, lifetime, eclipse service, radio frequency powers and certain general technology factors such as the performance of batteries and solar cells, and calculates the array power and the masses of the payload and primary power systems. Using these results, and differentiating between spinning and body stabilized satellites, the results of regression analyses on many communication satellites are then used to ascertain the weights of the other subsystems. Simple orbital mechanics are used to determine the weights of propellants, apogee motor, etc., to arrive at a final mass estimate. This estimate should be accurate to between 5 and 10 per cent if reliable input data are available.
Equalization of tdma links using in‐service impulse response measurement
Authors: Mazur B. , Lyons R. 
Published: July 2007

AbstractThis paper describes a method of measuring the frequency response of a digital radio link given the received (modulated) message signal, suitable for the incremental commissioning and in‐service monitoring of links in a QPSK/TDMA system. The method applies least squares estimation techniques to samples of the I and Q baseband components in order to derive a linear equivalent model for the channel. Results obtained by computer simulation of an INTELSAT V channel demonstrate that the method can provide a better basis for linear equalization of a non‐linear channel than the frequency response measurements provided by conventional techniques. A mathematical formulation and an implementation overview are also given.
CPM—the effect of filtering and hard limiting
Authors: Aulin Tor , Sundberg Carl‐Erik 
Published: July 2007

AbstractThe attractive properties of the digital constant amplitude modulation scheme CPM (continuous phase modulation) have been demonstrated in a previous paper in this journal.1 This concerned both the power and spectral efficiency of the large family of CPM schemes over the Gaussian channel.In this paper the considered channel can be both bandlimited or band‐ and amplitude‐limited at the same time. Analytical results as well as simulations are presented for a number of selected CPM schemes.In today's increasing demand for bandwidth, CPM is an attractive candidate for future satellite applications because of its spectral efficiency. In addition to this comes the fact that the transmitted signal has a constant amplitude and good detection performance when optimal coherent detection is performed.
Comsat's tdma traffic terminal
Authors: Benjamin Melvin C. , Bogaert Winston M. 
Published: July 2007

AbstractCOMSAT has installed two traffic terminals in the Etam earth‐station and is currently installing a third in the new Roaring Creek earth‐station to access the INTELSAT TDMA network. This paper describes the COMSAT TDMA traffic terminal equipment from the supergroup interface to the antenna. COMSAT's 1: N redundancy approach for terrestrial interface equipment and DSI unit back‐up is described as well as electrical path length, amplitude and group delay equalization techniques, special on‐line RF monitoring and failure reporting facilities and the operation and maintenance centre which can operate and perform diagnostic testing on up to four traffic terminals from a central location.
Reference terminal equipment for the intelsat tdma system
Authors: Saburi A. , Mitani T. , Ishi Y. , Takai H. , Takatsukasa N. 
Published: July 2007

AbstractOne of the distinctive features of the INTELSAT TDMA system is that the role of the reference station is completely separated from the ordinary station. For this reason, the reference station (called a TDMA reference and monitor station (TRMS)) needs special facilities: reference terminal equipment (RTE) and a TDMA system monitor (TSM). NEC corporation has developed and produced the RTE/TSM facilities necessary for the INTELSAT TDMA/DSI system.In November 1984, the first RTE/TSM equipments were installed at the first two TRMS sites for the major path 2 in the Atlantic Ocean region. Since that time, several field tests have been successfully conducted.In this paper, the signal processing equipment (SPE) of the RTE is described in detail.
Intelsat operations center tdma facility
Authors: Hodge G. , Johnson R. , Cook W. , Saralkar K. 
Published: July 2007

AbstractThe INTELSAT Operations Center TDMA facility (IOCTF) was built by COMSAT Laboratories to monitor and control the operation of the INTELSAT time‐division multiple‐access (TDMA) system. This paper describes the overall monitoring and control requirements, and the role played by the IOCTF in satisfying those requirements. The IOCTF architecture and hardware configuration are described, and key technical design and implementation issues are discussed.
Nec's traffic terminal equipment for the intelsat tdma system
Authors: Saburi A. , Oshima G. , Saga R. , Atobe M. , Shigaki S. , Yoshida K. 
Published: July 2007

AbstractThe traffic terminal equipment (TTE) for the INTELSAT TDMA System handles the actual traffic of the network and operates under control of the reference terminal equipment (RTE) installed at the reference station.The required function and performance for the TTE are specified in detail by the INTELSAT TDMA/DSI specification, but there may be many approaches to actual equipment design. NEC's TTE has been designed based on NEC's extensive experience and field‐proven circuit techniques. In addition, the TTE design has been affected by the fact that NEC has been engaged in the development and production of the RTE for INTELSAT.NEC's TTEs have been delivered to customers since the summer in 1984, with the first test with the RTE through the satellite having been successfully performed at COMSAT's Etam station at the end of 1984.This paper describes the capabilities of the traffic terminal equipment, developed and manufactured by NEC Corporation, together with the design approach used in its fabrication.
Alignment, testing and maintenance principles in the intelsat tdma/dsi network
Authors: Oei A S. , Colby R. J. , Parthasarathy R. , Stimson A. L. 
Published: July 2007

AbstractThis paper discusses the principles underlying the alignment, testing and maintenance procedures (A,T & M) in the INTELSAT TDMA/DSI network. These principles are used in order to define the A, T & M functional groupings necessary to fully and systematically evaluate and maintain the network. It is shown that, as in the testing of any complex system, the overall test programme can be broken‐down into a series of individual test elements. Test elements naturally fall into logical associations called functional groups and, for practical reasons, some functional groups must be evaluated before others. Since the various users of the TDMA system will employ a variety of different manufacturers' equipment, a universal method of organizing the test programme had to be devised. To provide a set of test procedures which are independent of specific equipment design, a reference configuration approach has been taken which reflects the involvement, time‐ordering and hierarchy of the functional groups.The objective behind the use of this reference configuration approach is to assist the development and conduct of the alignment, testing and maintenance procedures so as to ensure minimal interruption to an operational TDMA network. In addition, the use of this technique will facilitate the planning of A, T & M test schedules. Finally, it is shown how the reference configuration approach encompasses the INTELSAT TDMA traffic terminal Satellite Systems Operations Guide (SSOG) and the TDMA Reference Terminal Operations Guide (TROG).
Pointing losses in single‐axis and fixed‐mount earth‐station antennas due to satellite movement
Authors: Buchsbaum L. M. 
Published: July 2007

AbstractThere are substantial cost advantages in the use of single‐axis or fixed‐mount earth‐station antennas, thus reducing or eliminating the need for autotracking in earth‐stations operating with quasi‐stationary satellites. Such cost advantages are more relevant in small antennas where the tracking system represents a larger percentage of the overall cost. In addition, small antennas are particularly suitable to be operated without autotracking, owing to their wider half‐power beamwidth. This paper describes a model for calculating the antenna pointing loss as a function of the antenna diameter, operating frequency band, satellite station‐keeping tolerances, and the relative geometry between the earth‐station and the satellite. The model has been extensively used in the development of INTELSAT's IBS and VISTA services as well as in domestic leases. Although the model has been developed based on orbital mechanics equations, its emphasis is towards earth‐station and systems engineering applications. Some example calculations and results obtained through an HP‐41 CV programmable calculator are also provided.
Field test results of multi‐channel digital tv transmission at 15 and 30 Mb/s through an intelsat satellite using a PSK/FDMA system
Authors: Murakami Hitomi , Sato Gunkichi , Matsumoto Shuichi , Hirabayashi Tatsuhiko , Yamamoto Hideo , Donald Wallance W. , Bachmann Erik 
Published: July 2007

AbstractThis paper describes field test results of multi‐channel digital TV transmission using a PSK/FDMA system and the related subjective test results of received TV pictures. The picture quality of the multi‐channel 15 or 30 Mb/s transmission for both NTSC and PAL systems through the INTELSAT POR satellite are subjectively evaluated for various bit‐error rates. In addition, subjective evaluations were made at various values of earth‐station e.i.r.p. to compare the picture quality of digital transmissions with that of current half‐transponder FM transmission.
Efficient adaptive forward error control schemes for Ka‐band satellite systems
Authors: Khan M. H. , Le‐Ngoc T. , Bhargava V. K. 
Published: July 2007

AbstractAdaptive fade margin is required to counter the severe but varying rain attenuation in Ka‐band satellite communications. In a search for a suitable rain countermeasure, the effectiveness of adaptive forward error control (AFEC) schemes is studied. Two AFEC schemes using convolution codes and concatenated codes are proposed and their performances analysed. The schemes can provide progressively adaptive fade margins of 10‐1 and 10‐4 dB, respectively, in excess of the system's fixed fade margin.To improve the efficient use of shared resources of the system, an AFEC scheme using double coding is introduced and its performance analysed. In this scheme a single codec is used repeatedly, resulting in reduced hardware cost and increased use. By using convolutional code and Golay code the above scheme can provide adaptive fade margins of 10°8 dB and 8°1 dB, respectively. Although concatenated codes have slightly better performance than double codes, the hardware implementation and decoding complexity of the latter are significantly less.Implementation complexity of AFEC resource sharing in the light of code complexity, time frame expansion, link condition monitoring and signalling is discussed in detail.
Satellite networks in the isdn era
Authors: Amadesi P. , Haines P. , Patacchini A. 
Published: July 2007

AbstractThe concept of an integrated service digital network (ISDN) is becoming topical for the evolution of world‐wide telecommunications. In fact the consultative committees (CCITT and CCIR) have worked actively on the definition of the ISDN and its functions, and many PTTs and other operating companies are engaged in programmes aimed at introducing digital transmission and switching in the public switched telephone network (PSTN) with a view to establishing the first versions of an ISDN.Satellites are well prepared to operate in an ISDN environment.The present competition with fibre optics and other terrestrial carriers may perhaps limit the initial contribution of satellites to the establishment of trunk routes in the first ISDNs, but in the medium term the particular characteristics of flexible distribution of information over very large areas may become of fundamental importance, and many satellite‐based networks developed independently may give concrete support to the ISDN. In the long term satellites may experience an even deeper degree of integration, by providing part of the switching facilities of the ISDN on board.
Economics of multiple beam satellites
Authors: Campanella S. J. , Pontano B. A. , Kao T. 
Published: July 2007

AbstractThis paper describes an advanced multibeam communications satellite system using on‐board processing and hopping beams in conjunction with low‐cost earth‐stations to derive a significant advantage over fibre optic submarine cable. It serves thousands of small earth‐stations located near the origins of traffic. An economic analysis is presented for both this satellite system and competitive fibre optic cable for the 1995 to 2007 epoch. Results indicate the satellite service to be significantly lower in cost, and in addition it delivers the service near to the origin of the traffic, providing additional savings in terrestrial connections.
Access protocol performance for on‐board processing business satellite systems
Authors: El Amin M. H. M. , Chung L. N. , Evans B. G. 
Published: July 2007

AbstractThis paper presents protocols for use in efficient accessing of multi‐service business satellite systems. A new reservation TDMA scheme with free slots contention is proposed as being particularly suitable. The new access protocol is simulated using a numerical Petri‐net model and results are given for variations in numbers of earth‐stations, traffic mixes, balanced‐to‐unbalanced traffic, reservation scheme and free slots contention. Finally an analytical derivation is presented for the protocol performance which agrees well with simulation.
SS‐TDMA switch matrices using optical technology
Authors: Peters Robert A. 
Published: July 2007

AbstractThe principles and potential advantages of an optical switch matrix for use in an SS‐TDMA microwave switching matrix subsystem are reviewed, and the relative merits of three optical switching techniques are compared. An INTELSAT sponsored programme is described that has demonstrated the feasibility and the problems of developing a compact, monolithic, optical switch matrix. RF performance generally exceeded that of switch matrices built using discrete microwave components. However, the switch matrix has a high insertion loss and requires temperature stabilization or compensation. To be practical, 1‐3 micron of longer wavelength technology must be used.
Synchronization of remote digital clusters via satellite for ISDN
Authors: Johannsen Klaus G. 
Published: July 2007

AbstractPresently, there are several countries in the process of converting their national communication system to an integrated digital communication system and eventually, to an integrated services digital network (ISDN). In some developing nations, where a satellite is used for long‐haul transmission to remote and isolated areas, and where there is no terrestrial connection to those areas, the question has been raised whether the satellite can remain a part of such a network, and if so, can it be used to synchronize the remote digital clusters.The matter of concern is the satellite's residual motion. The residual relative motion between the satellite and a ground station produces doppler and therefore, frequency shifts which may cause loss of information, the amount of doppler or carrier frequency shift is location dependent, in general it increases with station latitude and satellite inclination. However, for a given geographic area and a given accuracy in satellite station keeping, it can be shown that satellite links can provide network synchronization to remote digital clusters within the slip rate requirements of a domestic integrated services digital network. In order to permit a less stringent orbit maintenance, or to include earth‐stations of higher geographical latitudes, it is practical to include doppler buffers as part of the satellite earth‐station equipment.
Some aspects of the analysis of experimental data for short‐term frequency scaling
Authors: Upton S. A. J. , Holt A. R. , Upton G. J. G. 
Published: July 2007

AbstractOver one hundred hours of British Telecom's half‐second event data from the OTS and ATS‐6 satellites has been analysed with respect to short‐term frequency scaling of attenuation. The ratio of attenuation at two frequencies is particularly vulnerable to system effects and noise. Data analysis techniques are discussed and it is shown that a least‐squares analysis is not suitable when the time period is short. Appreciable variation occurred in the mean value of the short‐term ratio from one event to another. Only on a few occasions did significant changes occur during an event. Simultaneous data from other equipment gives confidence that these changes are due to propagation effects.
Large/small carrier performance of non‐linear devices
Authors: Stette Gunnar 
Published: July 2007

AbstractThe intermodulation properties of a memoryless non‐linear amplifier with two carriers having large level difference are in the limit determined by the properties of the amplitude characteristic of the amplifier at a single point, i.e. at the operating point determined by the stronger carrier. The paper derives the mathematical expression for the level of the dominating third‐order intermodulation product, and also shows how this level can be determined graphically from a given amplitude characteristic.
CDMA versus FDMA channel capacity in mobile satellite communication
Authors: Johannsen Klaus G. 
Published: July 2007

AbstractAt present a major effort is under way to define the most efficient modulation/multiple access system in mobile satellite communication. Where the emphasis is on digital voice modulation, the proposed multiple access methods almost always imply frequency division multiple access (FDMA). This analysis presents a comparison between FDMA and code division multiple access (CDMA), for the operation of both multiple access methods in the mobile satellite communication environment. The mobile satellites under consideration use multiple‐beam or scan‐beam antennas and employ frequency reuse of the allocated L‐band frequency spectrum. As CDMA is better at absorbing Doppler and multipath effects, and permits higher rate coding, in general (practical considerations aside) it appears to be the more capable system.
Propagation theory in adaptive cancellation of cross‐polarization
Authors: Ghorbani A. , McEwan N. J. 
Published: July 2007

AbstractThe application of propagation theory to the structure and control of adaptive networks designed to cancel hydrometeor‐induced cross‐polarization in microwave communication links is summarized. When adaptive cross‐coupling networks are realized at radio frequency as variable waveguide polarizers, desirable simplifications are to make them lossless devices with at most two free parameters. Performance calculations for such simplified forms are fully reviewed.Several new approaches to the design of controllers for the cancelling networks are also made possible. New results are presented on the performance of systems which use only one pilot tone, or even dispense with cross‐polar measurement completely. It is also shown that the reciprocity of the hydrometeor medium, an apparently safe assumption, makes possible an extract precorrection of a transmitted polarization if control is based on a beacon signal of the orthogonal polarization sent back from the receiving point.
Effects of solar transit on Ku‐band VSAT systems
Authors: Mohamadi Farshad , Lyon David L. , Murrell Peter R. 
Published: July 2007

AbstractA satellite earth‐station is affected by added radio noise from the Sun when the Sun passes behind the satellite as seen from the earth‐station. In the following, an exact analysis of this solar transit is derived, and an approximate method is presented for practical cases. Moreover, networks of very small aperture satellite terminals (VSATs) operating at Ku‐band microwave frequencies of 12–14 GHz behave differently during the solar transit period than the more traditional C‐ or Ku‐band satellite networks; therefore analytical and experimental results for VSATs have been presented. An explanation is given, based on these analyses, of why solar transit outages are rarer in VSATs than in conventional satellite communications systems.
Research and development activities of optical ISLS in Japan
Authors: Yasukawa Koji , Araki Ken'Ichi , Kashiki Kanshiro , Aruga Tadashi 
Published: July 2007

AbstractThe current state of research and development activities of optical intersatellite links (ISLs) and related optical devices in Japan, including semiconductor laser diodes, photodiodes, CCDs and modulation/demodulation techniques, is described. Subjects for further research on optical devices and communications are summarized. An optical communication experiment which uses the communications system on board the Engineering Test Satellite‐VI to be launched in Japan in 1992, is outlined.