bluuebunny/crossref_metadata_2025_split huggingface dataset:
System Implications of 14/11 GHz Path Depolarization. Part II: Reducing the impairments
Authors: Allnutt J. E. , Rogers D. V. 
Published: July 2007

AbstractDual‐polarized co‐channel operation via international communications satellites places stringent requirements on the amount of interference that can be allowed from all sources. System design must allow for the depolarization caused by rain and ice crystals, the principal source of additional interference. In the 14/11 and 14/12 GHz bands, some paths are depolarization limited, particularly at lower path elevation angles, or become so with up‐link power control. Others are attenuation limited. Therefore, a means must be found to reduce the level of path depolarization to meet the requirements for path availability. In Part I or this paper, reference joint statistics of cross‐polarization discrimination/attenuation statistics were derived for a number of paths and climates to establish the additional fade and cross‐polarization discrimination margins required. This second paper addresses methods for reducing the system effects of path depolarization.Appropriate orientation of the polarization vectors at the spacecraft is shown to be an attractive alternative for spot‐beam applications. For all other situations, it is concluded that single‐parameter, phase‐only compensation at the earth terminal will meet all practical system requirements.
Development of a prototype, experimental single‐channel sequencing navstar gps receiver: Part II—Software description
Authors: Allison M. T. , Daly P. 
Published: July 2007

AbstractLate in 1988 the Navstar GPS satellite navigation operational phase is planned to commence, offering world‐wide, continuous and precise position‐fixing and timing information to observers on land, sea, air and in space. This paper describes the development of a particular type of Navstar receiver—a single‐channel, single‐frequency, sequencing C/A code unit—and results of various tests carried out on the present phase—II satellite constellation. Part I of this paper deals with the NAVSTAR satellite system and the development of receiver hardware, whereas Part II concentrates on software development and system performance.
The TNS program: A computer simulation package for the intelsat TDMA network
Authors: Shinonaga Hideyuki , Yamasaki Norikazu , Koga Keiichiro , Muratani Takuro , Wu William W. 
Published: July 2007

AbstractThe TNS (TDMA Network Simulation) program is a computer simulation package developed for the evaluation, test and analysis of all the protocols in the INTELSAT TDMA network. The TNS program faithfully simulates the dynamic operation of the network, taking account of the satellite motion, and makes it even possible to simulate the network operation under some abnormal conditions, such as terminal function failure and transponder failure.This paper describes the TNS program in terms of its design approach, its capabilities, its structure, its input and output data, and its operation. An example simulation for the whole system start‐up procedure assuming the Atlantic Ocean region is also presented.
Design of a selective FEC subsystem to counteract rain fading in ku‐band TDMA systems
Authors: McMillen G. R. , Mazur B. A. , Abdel‐Nabi T. 
Published: July 2007

AbstractA major concern in satellite communications systems operating at frequencies above 10 GHz (e.g. Ku band) is the performance degradation caused by rain fading. In this paper, an effective method for combatting this phenomenon in TDMA systems is described. This method is based on the application of additional FEC coding protection on a dynamic basis to faded traffic terminals. Selective (adaptive) forward error correction (S‐FEC) coding permits the fixed fade margins used by the network earth‐stations to be substantially reduced, while a desired outage probability is maintained. This paper deals primarily with the implementation of the monitoring and control subsystems required in a practical S‐FEC network.
North‐south coupling study
Authors: Pardo Jeff 
Published: July 2007

AbstractAn empirical study of stationkeeping data on several RCA series 3000 spacecraft which was used to analyse coupling effects during inclination manoeuvres has yielded valuable data on changes in east‐west drift and eccentricity which result from these manoeuvres. The major origins of these effects are thruster alignments and plume impingement on the north solar panel. While thruster alignments for a given spacecraft will differ depending on its centre of mass, plume impingement showed a higher order seasonal influence over the basic cant angle differences between thruster pairs on opposite sides of a satellite, i.e. when the solar arrays are at a ‘near zero’ angle (array panel directly facing earth) the net radial vector bias is attenuated. Plume impingement has a primary seasonal influence in tangential coupling, however: when the solar array was ‘looking east’, eastward drift was observed, and likewise when the solar panel was west‐oriented, there was a westward drift effect. Recommendations are made as to how this information might be used to improve an operator's stationkeeping schedule.
FM/TV Interference into rate 1/2 FEC encoded SCPC/QPSK
Authors: Dutronc J. , Freixe J. M. , Prouse D. , Cooke R. 
Published: July 2007

AbstractThis paper presents some results obtained in laboratory measurements of interference caused by FM television signals to encoded SCPC/QPSK carriers. Certain parameters, such as the TV energy dispersal excursion, the frequency spacing between wanted and interfering carriers, the SCPC bit rate, etc., were varied during the measurements in order to study their influence on the amount of interference suffered by the SCPC channel.Computer simulations were also carried out in order to analyse and interpret measurement results obtained in some cases.Conclusions are drawn on the use of a possible interference criterion when rate 1/2 convolutional encoding and soft decision Viterbi decoding is used in the SCPC system as well as on the expected improvement with frequency offset.
A coded 8‐PSK system for 140 Mb/s information rate transmission over 80 MHz non‐linear transponders
Authors: Fang R. J. F. 
Published: July 2007

AbstractA combined 8‐PSK modulation and rate 7/9 convolutional coding technique is proposed for 140 Mb/s information rate transmission over the 80 MHz INTELSAT transponders, thus achieving a bandwidth efficiency of 1.75 b/s/Hz of allocated bandwidth. The desired power efficiency is to achieve a bit error rate of 10−6 at an Eb/N0 of 11 dB, including modem and codec implementation losses. The proposed system employs an 8‐PSK modem operating at a 60 MHz symbol rate (or 180 Mb/s bit rate), as well as a rate 7/9 convolutional encoder and a 16‐state Viterbi algorithm decoder operating at 60 MHz. The rate 7/9 code is periodically time varying and is designed to maximize the Euclidean distance between the modulated codeword sequences, thereby achieving a 3 dB asymptotic coding gain relative to the conventional QPSK system over an AWGN channel. This code is also designed to reduce decoder complexity for high‐speed operations.The performance of the proposed system over INTELSAT V and VI non‐linear transponders was evaluated by Monte Carlo computer simulation. The 180 Mb/s 8 PSK modem, including the automatic frequency control, automatic gain control, carrier recovery and clock recovery circuits, has been implemented and tested. The complete Viterbi decoder is being implemented on five boards, and the critical add‐compare‐select (ACS) circuit of the high‐speed Viterbi algorithm decoder is being implemented with hybrid technology employing 100‐K series emitter‐coupled logic dies on specially designed ceramic substrates. The ACS circuit operates at a speed exceeding 120 MHz, well over the design goal of 60 MHz. Construction of this codec is almost complete.
Low rate encoding: A means of increasing system capacity in a TDMA/DSI system
Authors: Fresia F. , Patacchini A. , Prins C. 
Published: July 2007

AbstractThe satellite capacity required in a TDMA/DSI system for a certain amount of traffic can be substantially reduced when using associated LRE techniques. An analysis based on the future EUTELSAT TDMA/DSI traffic forecast has been made in this respect, by using the computer program presently in use at EUTELSAT for the generation of burst time plans.The analysis considers different operational modes (single destination, multidestination and multiclique) and presents also some considerations on the problem of transition from a 64 kb/s TDMA/DSI system to a 32 kb/s TDMA/DSI system.
Sixty Mb/s transversal equalizer
Authors: Uzunoglu Vasil 
Published: July 2007

AbstractA model of a linear digital communication system is introduced and adaptive equalization in general is explained. A five‐tap transversal equalizer is designed, breadboarded and tested in a 60 Mb/s burst mode modem in a quasi‐linear and a non‐linear channel under the following configurations:

Parabolic, linear and combination of parabolic and linear delay distortions were inserted after the non‐linearity (TWTA).
Case 1 was repeated with distortions inserted before the non‐linearity.
When parabolic distortion is added before the non‐linearity improvements in the BER are significant.
Generalized satellite link model and its application to the transmission plan
Authors: Tamir Izhak , Rappaport Yigal 
Published: July 2007

AbstractA generalized model for the satellite link that includes non‐linear effects is presented. The transponder is handled as a black box with nominal gain gs. At a specific operating point each signal in the transponder has its own gain, gsci, that may be different from gs. The parameter gsci depends on the operating point of the transponder, the power of the signal and the distribution of the residual transponder power among the other carriers. The intermodulation between the carriers and between them and the up‐link noise is included in the model as well. The generalized model is represented by the conventional traditional equation, modified with correction factors which account for the nonlinear effects. Application of the model to typical transmission plans is given and comparison of the results to field experiments and transponder analysis program is included. Emphasis is placed on the use of the transponder with mixed TV and SCPC operation.
On‐board processing for communications satellites: Systems and benefits
Authors: Nuspl P. P. , Peters R. , Abdel‐Nabi T. , Mathews N. 
Published: July 2007

AbstractThis paper discusses on‐board processing systems and associated benefits including connectivity, increased capacity, lower costs and system improvements; there are complex trade‐offs in design approaches. Several architectures are described which use a microwave switch matrix, a baseband switch matrix or baseband processor. Regeneration (an advanced form of on‐board processing) consists of demodulation followed by remodulation and provides access to baseband signals. The link advantages of this method are clearly presented for 120Mb/s TDMA and for IBS at 1/544 Mb/s. Additionally, there are discussions of five architectures using multi‐carriers per transponder, and their advantages and disadvantages. Some considerations of using on‐board decoding and baseband processing functions are also briefly presented.
Satellite communication systems for domestic/business services
Authors: Perrotta G. , Losquadro G. , Giubilei R. 
Published: July 2007

AbstractThis paper is composed of two parts.The first part addresses some topics associated to the implementation of FDMA/TDM systems for ‘business’ services applications, operating at Ka band.A modular regenerative and processing satellite repeater, each module capable of handling up to 16 up‐link carriers in the 2 Mb/s range is considered. Available coding techniques were reviewed; concatenated codes seem highly interesting because of the high coding gains achievable with two simpler co‐decoding processes in series, and also because they lead to an implementation wherein the internal coder is installed on board the satellite, while the external one is installed in the user terminals.The problem of keeping stable the up‐link carriers in the satellite demodulators is discussed and a compensation method is proposed.Finally, simulation results of co‐decoding and carrier extraction performance are illustrated.The second part concerns the implementation of a multifrequency TDMA system. This is a hybrid system whereby the access for up‐links uses time and frequency slots in a time‐frequency map. The adoption of a clock synchronous network allows a frame for which no preamble and guard time are inserted between the burst.The error contributions and the performance of the clock synchronous network are assessed. A solution to the problem of fast phase/frequency estimation is proposed.For a clock synchronous network fast algorithms suitable for frequency demultiplexing and detecting of the FDM signal could be adopted; a modular solution to the implementation of the demultiplexer and detector is proposed based on the use of an optimized matched filter; a multistage scheme minimizes the number of multiplications.
An on‐board processing satellite payload for european mobile communications
Authors: Evans B. G. , Casewell I. E. , Craig A. D. 
Published: July 2007

AbstractThe paper considers the application of satellite on‐board processing (OBP) technology for land mobile applications for possible introduction in the late 1990s. Initially a system outline is presented followed by a discussion considering the merits of OBP over conventional transparent payloads. The paper then presents an overview of the work being carried out as part of an ESA study. Some details on the critical parts of the system are also included.
Test results for on‐board burst‐mode CQPSK modem
Authors: Kazekami Y. , Sawada H. , Ishizu T. , Betaharon K. 
Published: July 2007

AbstractAn on‐board burst‐mode modem for coherent processing of a QPSK signal at 120 Mb/s is realized with small, low mass and low power consumption. This paper presents the hardware configuration and the various measured test data including physical characteristics. The overall performance through an earth station modem is also presented.
Non‐regenerative satellite switched FDMA (SS/FDMA) payload technologies
Authors: De Santis Pietro V. 
Published: July 2007

AbstractSatellite switched frequency division multiple access (SS/FDMA) satellite systems are new adaptations of the basic FDMA architecture for multiple beam spacecraft. Present multibeam satellite systems feature on‐board interbeam connections operating on a transponder channel basis, e.g. 72 MHz. SS/FDMA on board connectivity is based on much narrower channels and consequently achieves a much better utilization of spectrum resources whenever connectivity requirements are of the order of fractions of a transponder bandwidth.This work presents a critical analysis of various non‐regenerative SS/FDMA satellite systems, identifies the technological requirements to be met in order to achieve the practical realization of SS/FDMA on‐board processors and, finally, proposes two novel variable bandwidth variable centre frequency (VBVCF) demultiplexers with continuous and discrete reconfigurability.
VSAT Networks—an overview
Authors: Maggenti Mark , Ha Tri T. , Pratt Timothy 
Published: July 2007

AbstractThis paper examines the technology and constraints of very small aperture terminals (VSAT) networks, a special type of wide‐area thin‐route satellite network that represents a recent innovation in the field of satellite communications. VSAT network architectures suitable for both data and voice communications are studied in this paper. Several issues concerning the frequency of operations, that is, C‐band versus Ku‐band are examined, and trade‐offs between non‐spread spectrum and spread spectrum techniques, as well as modulation and multiple access schemes, are considered in detail. Link design examples are given to illustrate the performance of various types of VSAT networks.
Dielectric space frame radomes for satellite communications
Authors: Rwabona‐Katashaya S. , Evans B. G. 
Published: July 2007

AbstractThe cross‐polarization, signal attenuation and boresight shift for a number of dielectric space frame (DSF) radomes have been investigated using the induced field ratio method. It is shown that DSF radomes produce substantially less cross‐polarization than their metal counterparts. It is concluded that in view of INTELSAT's specification of 30.7 dB cross‐polar discrimination within an antenna's tracking beamwidth for frequency re‐use communication system antennas, DSF radomes, in particular those considered, would not yield appreciable system degradation. The general method presented is extendable to other radomes structures provided that connectivity information is available.
Ku‐Band satellite data networks using very small aperture terminals—part II: System design
Authors: Raychaudhuri D. 
Published: July 2007

AbstractIn this part of the paper on Ku‐band VSAT networks, the issue of overall system design is considered. After discussing possible system architectures, primary attention is given to the star network configuration in which customer‐premise VSATs communicate with a central hub station, co‐located with, or terrestrially connected to a host computer. The component elements of a Ku‐band star network for interactive data applications are discussed and the critical items from the point‐of‐view of performance, capacity and cost are identified. An analytical model for the network, which combines delay‐throughput characterization of the multi‐access inbound and TDM outbound channels with satellite link analysis is described. The analytical model is exercised over a range of typical system component, traffic model and performance objective scenarios to provide a set of general design guidelines. These guidelines are useful for evaluating the trade‐offs between key system elements (channel access unit, modem, VSAT antenna and satellite), VSAT traffic message length parameters and the performance objectives (average and peak network response time and availability). The results are used to address the issue of multi‐access protocol selection over a range of scenarios typical of 1.2 or 1.8m VSAT‐based interactive networks using current commercial Ku‐band satellites. The results show that interactive star networks are often limited by satellite power rather than bandwidth, so that the use of simple contention access for VSATs may not imply a significant system capacity penalty.
Effects of baseband predistortion at the transmitter on the performance of a DEQPSK satellite modem
Authors: Cheung S. W. , Clark A. P. 
Published: July 2007

AbstractThe paper presents the results of an extensive series of computer‐simulation tests to determine the effects of bandlimiting, nonlinear distortion with and without predistortion, and adjacent channel interference (ACI), on the tolerance to additive white Gaussian noise of a digital satellite modem. The modem transmits a differentially encoded quaternary phase‐shift keyed (DEQPSK) signal over a satellite link, where the high‐power amplifier (HPA) at the earth‐station transmitter may introduce AM—AM and AM—PM conversion effects into the DEQPSK signal, but the satellite transponder is linear. Four different bandwidths of the transmitted signal are tested, together with three different levels of output back‐off in the HPA at the transmitter. The predistorter operates on the baseband signal at the input to the modulator in the transmitter and assumes a prior knowledge of the HPA characteristics. ACI can be introduced into the transmitted DEQPSK signal by the corresponding DEQPSK signals, which occupy the two immediately adjacent frequency bands. The latter signals are assumed to have the same transmission rate and bandwidths as the first signal.Various combinations of the different distortion and interference effects are studied, using an equivalent baseband model of the transmission system, and the arrangements selected are those achieving the most efficient use of bandwidth together with the best tolerance to additive white Gaussian noise. A surprisingly good performance is achieved.
Solid‐state laser cross‐link systems and technology
Authors: Begley D. L. , Kobylinski R. A. , Ross M. 
Published: July 2007

AbstractLaser communications offer a viable alternative to r.f. communications for intersatellite links. High data rate, small antenna size, narrow beam divergence and narrow field of view are characteristics of laser communications that offer a number of potential advantages for system design. This paper presents an overview of solid‐state laser cross‐link systems and technologies.
An experimental optical link between an earth remote sensing satellite, spot 4, and a European data relay satellite
Authors: Arnaud M. , Barumchercyk A. , Sein E. 
Published: July 2007

AbstractThe implementation of an experimental optical link between a low earth orbit spacecraft (SPOT 4, of the French Earth Remote Sensing Programme) and a geostationary satellite (for which the European Space Agency is responsible) is described. This optical link is to be used for transmitting the SPOT 4 payload data stream at a rate of 50 Mb/s. These data will be relayed to a ground station through a feeder link in the Ka or Ku band.This first model, on SPOT 4, will demonstrate the feasibility and performance of optical communications and will be used on a pre‐operational basis to relay image data. The second model, on SPOT 5, could be used on an operational basis in connection with the European Data Relay satellite.The optical terminal uses a 20 cm diameter telescope with Ritchey Chrétien optics, a 30 mW GaAlAs laser diode and a silicon avalanche photodiode, the total weight being around 80 kg and the power consumption 120 W.
Optical ISL tracking considerations in meeting ISDN requirements
Authors: Peters Robert A. 
Published: July 2007

AbstractBurst errors in an optical intersatellite link (ISL) are short term (of the order of a millisecond) degradations of the link due to antenna mistracking. These errors degrade the average bit error rate (BER), decrease coding gain, complicate calculations of tracking accuracy, and give rise to concern about the quality of the link for carrying digital signals. After reviewing previous work on these topics, the digital performance of the link is examined in terms of how these considerations affect the ability of an optical ISL to meet ISDN (Integrated Services Digital Network) criteria for an ISL. A link with on‐board regeneration is assumed. Since no allocation has yet been made for an ISL, an allocation of 25 per cent of the degradation permitted for the satellite link by CCITT Rec. G.821 and CCIR Rec. 614 is assumed here. It is found (1) that if the requirement derived from Rec. 614 is met, the requirements derived from Rec. G.821 are also met and (2) that an optical ISL should have little difficulty in meeting these requirements.
Optical intersatellite link with direct detection: The laser diode‐pumped Nd laser option
Authors: Arrigoni M. , Maddè R. 
Published: July 2007

AbstractFollowing a brief introduction reviewing various laser systems suitable for ISL, a typical link budget for an optical ISL with a Nd laser is calculated. Laser diode pumped Nd lasers are described, and several host materials are considered. Modulation formats and typical receiver performances for direct detection are examined in order to compute the minimum transmitted power required for the proposed link. Results show that laser diode pumped Nd laser systems are competitive for optical ISL.