SATCOM Systems Research Articles

MIMO satellite communication with accelerated dual paths asynchronous design

This paper presents a novel asynchronous design approach for multiple input multiple output (MIMO) satellite communication (SatCom) systems. One of the main challenges for MIMO SatCom systems is that these are prone to transient faults that typically are attributable to radiation hazards. Hence, instead of using conventional synchronous circuits, we conceive our design using asynchronous circuits since it inherently has a high tolerance to transient fault. Additionally, we adopt accelerated dual paths (ADP) design into our system. By carefully arranging the data flow between the two paths, the ADP design approach can help to further accelerate the asynchronous system and increase the reliability of the system by circumventing transient faults induced delay, as well as tolerating latch-ups and other permanent faults. The numerical results show that this design approach provides promising results. For example, the proposed design can decrease the delay overhead of the entire system from 43.5 to 19.8 % at the fault rate of 400/clock cycle.

CLEAR SKY DIURNAL BEHAVIOR OF TROPOSPHERIC SCINTILLATION AT KU-BAND SATELLITE COMMUNICATION IN EQUATORIAL MALAYSIA

Tropospheric scintillation is referred to rapid fluctuation of received signal amplitude. It can cause propagation impairments that affect satellite communication systems operating at above 10 GHz of frequency. In this work, we have exploited 1 year of measured broadcasting signal data collected in Johor, Malaysia to investigate the effects of scintillation intensity on a SatCom system operating at 11.075 GHz with its links pointed towards the MEASAT-1 satellite (an elevation angle of 75.61°). We have investigated the behavior of this scintillation amplitude through the classification and analysis of a time-series satellite broadcasting signal and have then compared the statistical results with existing scintillation prediction models. The comparison results indicate that there is a significant discrepancy between measured data and those models and that the performance of these prediction models does not appear to be satisfactory, with the exception of the ITU-R and the Ortgies Refractivity model. In addition, we have investigated the diurnal behavior of the scintillation intensity at four different periods of the day and proposed a modified Marzano model to accommodate local meteorological input parameters. The models performances are assessed against the available measurement dataset. The proposed models provide system operators and radio communication engineers with critical information on the fluctuations of tropospheric scintillation variance on the satellite signal during a typical day taken into the account of local meteorological peculiarities.

Capacity maximization based power loading analysis for digital channelized satcom systems

For digital channelized frequency division multiple access based satellite communication (SATCOM) systems, it is a challenging but critical issue to improve the transponder power and spectrum efficiency simultaneously under limited and non-linear high-power amplifier conditions. In this paper, different from the traditional link supportability designs aiming at minimizing the total transponder output power, a maximal sum Shannon capacity optimization objective is firstly raised subject to link supportability constraints. Furthermore, an efficient multilevel optimization (MO) algorithm is proposed to solve the considered optimization problem in the case of single link for each terminal. Moreover, in the case of multiple links for one terminal, an improved MO algorithm involving Golden section and discrete gradient searching procedures is proposed to optimize power allocation over all links. Finally, several numerical results are provided to demonstrate the effectiveness of our proposals. Comparison results show that, by the MO algorithm, not only all links' supportability can be guaranteed but also a larger sum capacity can be achieved with lower complexity.

SAT-COMM – Fade Inteferance and Band Mitigation Analysis

When it comes to address the capacity issue in satellite communication, the first technique to consider is the multi-beam coverage, with a high number of beams that allow a high degree of frequency reuse. In order to increase even more that capacity, the second step is to utilize higher frequency bands such as Ka (20-30 GHz), Q/V (40-50 GHz) or EHF (20-45 GHz) bands, where respectively, 1 GHz, 3 GHz and 2 GHz are allocated to the Fixed Satellite Service (FSS). The first c ommercial satellites with Ka-band transponders are today in operation, and it is expected that the congestion in lower fre quency bands like Ku-band will push new systems into moving progressively to Ka band and, in a longer term, to Q/V b and. Depending on the type of mission, Ka-Q/V band satellite could be envisaged as, for example, for two way broadba nd access services characterised by a high asymmetrical traffic, using part of the Ka-band for user access while data dist ribution service could take most advantage of wider bandwidth in Q/V band. Although Ka and Q/V bands are attractive from the point of view of the amount of frequency bandwidth that the satellit e can potentially use, some important limitation could moderate the enthusiasm of using them if specific techniques wer e not implemented in the satellite system to guarantee the capacity, the availability and the quality of service. The major limitation is the effect of radio-wave propagation through the lowest layers of the atmosphere. As the operating frequenc y is increased, the attenuation and scintillation effects of atmospheric gas, clouds and rain become more severe, the direc t consequence is the need to implement high system static margins, in order to insure a minimum outage duration of the service, for a given objective of link availability. However, technology limitation (on both terrestrial and space segments) combined with cost efficiency requirements refrain from considering fixed static margins as the only mean to compens ate propagation impairments at high frequency bands, and push towards the implementation of Fade Mitigation Techniq ues (FMT). The aim of this paper is to present the main issues in designing FMTs for Ka-Q/V band satellite communica tion systems. First of all, the conventional design of the physical layer of a satcom system is outlined. Afterwards, a revi ew of FMT concepts and related interference issues are presented followed by the examination of the impact on upper la yer. Finally, the main aspects of FMT design are investigated before proposing some recommendations. IFMT practical implementation (detection scheme and estimation techniques, consequences on signalling and impact on synchronisatio n) will not be dealt with in this paper as it is the object of [3].

SPACE-BORNE MULTIBEAM ARRAY PATTERN SYNTHESIS FOR INCREASING CAPACITY

The traditional pattern synthesis method of space-borne array is to achieve a \iso-∞ux beam coverage via approximating a desired pattern; however, the synthesized pattern may not optimize the whole satellite communication (SatCom) system performance. This paper analyzes the interference in multibeam SatCom system using CDMA, and establishes the relation model between user capacity and multibeam pattern. Additionally, a novel particle swarm optimization (PSO) based on simulated annealing (SA) pattern synthesis method is proposed, which chooses user capacity as synthesis objective function. The numerical analysis, which is performed for a hexagonal array with 19 stacked patch elements, conflrms that user capacity is at least doubled with the \max-gain-∞ux beam coverage implemented by our method, compared to the \iso-∞ux coverage when communication outage probability is 10%.

Combining Adaptive Coding and Modulation With Hierarchical Modulation in Satcom Systems

We investigate the design of a broadcast system in order to maximize throughput. This task is usually challenging due to channel variability. Forty years ago, Cover introduced and compared two schemes: time sharing and superposition coding. Even if the second scheme was proved to be optimal for some channels, modern satellite communications systems such as DVB-SH and DVB-S2 rely mainly on a time sharing strategy to optimize the throughput. They consider hierarchical modulation, a practical implementation of superposition coding, but only for unequal error protection or backward compatibility purposes. In this article, we propose to combine time sharing and hierarchical modulation together and show how this scheme can improve the performance in terms of available rate. We introduce a hierarchical 16-APSK to boost the performance of the DVB-S2 standard. We also evaluate various strategies to group the receivers in pairs when using hierarchical modulation. Finally, we show in a realistic case, based on DVB-S2, that the combined scheme can provide throughput gains greater than 10% compared to the best time sharing strategy.

Introduction Special Issue on DVB‐RCS2

INTRODUCTIONDVB-RCS is really the first and only broadband satellite communications standard. With workstarted already in 1998 and the first version approved in the DVB project already in 1999—10years ago—we are already talking of a mature technical specification. At the time the focus wason ATM to the desktop, Ka-band systems and large low-earth-orbit satellite constellations; orat least a lot of the community interest; and systems were proposed with several hundredsatellites. In ETSI there were two alternative specifications published at the time for mobilesatellite services based on GSM; these were the so-called GMR-1 and GMR-2 specification—both basically connected to one system each and one (or a few) vendors each.But, at the time there was also an increasing focus on standards. ETSI had just called forexperts to the Broadband Satellite Multimedia Specialist Task Force—STF BSM, and as a resultof this work established the BSM Work Group. ETSI was also the focus for the regulatory-oriented telecommunications specifications—the so-called ‘harmonized standards’ that describea way—in practice the only practical way—satellite terminals (or other telecommunicationsterminals) could comply with the new RTTEthus, the amountofnoise one could allow intoother bands or orbital locations. Article 3.2 of the RTT&E directive also had a clause stating thatwhile standards were not mandatory, stated that the communications interface should bepublished. While some argued that this meant the input and output interfaces—could both be IPfor instance—others believed that it was the air interface such as the GSM system that wasmaking world-wide success at the time (and still is). Whatever one might have believed—the factremains that DVB-RCS is just such an interface and it is published.At that time, a decade or so ago, there was also a major interest in the 2.5GHz of Ka-bandspectrum that was being made available for satellites. While not all of it would be for userterminals, some was reserved, for example, up- and downlink from gateways, it was still considered

A Rain Cell Model for the Simulation and Performance Evaluation of Site Diversity Schemes

This letter presents a rain cell model for the simulation and performance evaluation of site diversity schemes, useful for the design of satellite communication (SatCom) systems operating at very high frequency (e.g., Ka-band and above) for which the use of effective fade mitigation techniques (FMTs) is mandatory. The model takes advantage of MultiEXCELL for the synthesis of the local rainfall environment, whose interaction with the SatCom system is simulated to estimate the diversity gain for site separation distances up to 250 km. Tests against the data included in the diversity experiment database maintained by the ITU-R indicate a very good prediction accuracy. The proposed model represents a synthesis, in terms of applicability, of the two methodologies currently recommended by ITU-R, and, in addition, it is more flexible, enabling the analysis of diversity schemes of any order, configuration, and complexity.

ON THE OUTAGE PROBABILITY PREDICTION OF TIME DIVERSITY SCHEME IN BROADBAND SATELLITE COMMUNICATION SYSTEMS

A novel model for the outage probability prediction in time diversity satellite communication (SatCom) systems operating above 10GHz is proposed. Due to the migration of operating frequency at Ka band and above, atmospheric phenomena afiect the signal. Rain is the dominant fading mechanism. Diversity techniques are the probable solution of the compensation of rain fading. Among the diversity techniques, time diversity has been identifled as an e-cient and cost efiective technique. A method for the prediction of outage performance and diversity gain of time diversity SatCom systems is presented based on the physical assumptions of a well accepted dynamic stochastic model. The new method is tested against with simulated and experimental data with encouraging results.

Uplink laser satellite-communication system performance for a Gaussian beam propagating through three-layer altitude spectrum of weak-turbulence

Uplink laser satellite-communication (satcom) system performance has been extensively studied under the assumption that atmospheric turbulence statistics obey a Kolmogorov power-law spectrum model. Unfortunately recent evidence has indicated that Kolmogorov spectrum is sometimes incomplete to describe atmospheric turbulence statistics properly, in particular in the upper atmosphere. In this paper, we use a three-layer attitude spectrum model that exhibits non-Kolmogorov properties in portions of the troposphere and stratosphere. Using this spectrum in weak turbulence, we analyze the bit-error rate (BER) performance of an uplink laser satcom system with a collimated untracked Gaussian beam subject to scintillation and beam wander impairments. Our theoretical results show that the difference in BER between the three-layer altitude spectrum and the Kolmogorov spectrum is not appreciable for smaller transmitter beam radius, but is significant at larger transmitter beam radius. Furthermore, for a given laser wavelength or zenith angle, the optimum transmitter beam radius that can minimize the BER is very different between the two turbulence spectrums.

Special issue on satellite communication systems and networking

information society. In this context, the Q/V band frequencies will play a key role in enabling challenging and unproven broadband communications missions for a wide range of applications and leading to the implementation of Terabit Satellite Networks. The Q/V frequency band may be employed for feeder links, for direct-to(fixed, mobile) user satellite applications and as part of the whole integrated network. Some of these issues are of great interest by European Space Agency as this is testified with the launch of Alphasat in 2012. The focus of this Special Issue is to present high-quality unpublished research papers on recent advances in the wider area of SatCom Systems and Networks by experts from industry, academia, and space agencies. Our call for papers attracted numerous submissions worldwide.

Anti-Jamming Technology Performance Analysis of SATCOM Systems

Numerous technologies have been adopted in modern SATCOM to ensure communica-tion smooth. Among them, frequency hopping and onboard processing technology will be researched mainly in this paper. First, models of frequency hopping system and onboard processing system were built by Simulink. Then, the effect of coupling phenomenon analyzed on the theoretical. At last, Anti-jamming capability studied after simulating with different jamming. All above will provide convincing support to further research on SATCOM technologies; also, will guide the development of satellite communication.

Transponder Power Minimization Utilizing Optimum Channelizer Gains

Today, the Wideband Global SATCOM (WGS) system employs a new concept of adjusting the transponder power gain of individual links. A simple optimum method is derived for selecting these individual channel gains to minimize the amount of transponder power utilized. This new method directly solves a set of simple nonlinear equations and does not utilize any search algorithms or matrix inversions thus allowing it to be used with any number of links in a transponder.

A Large-Scale Space-Time Stochastic Simulation Tool of Rain Attenuation for the Design and Optimization of Adaptive Satellite Communication Systems Operating between 10 and 50 GHz

The design and optimization of propagation impairment techniques for space telecommunication systems operating at frequencies above 20 GHz require a precise knowledge of the propagation channel both in space and time. For that purpose, space-time channel models have to be developed. In this paper the description of a model for the simulation of long-term rain attenuation time series correlated both in space and time is described. It relies on the definition of a stochastic rain field simulator constrained by the rain amount outputs of the ERA-40 reanalysis meteorological database. With this methodology, realistic propagation conditions can be generated at the scale of satellite coverage (i.e., over Europe or USA) for many years. To increase the temporal resolution, a stochastic interpolation algorithm is used to generate spatially correlated time series sampled at 1 Hz, providing that way valuable inputs for the study of the performances of propagation impairment techniques required for adaptive SatCom systems operating at Ka band and above.

Assessment of rain fade mitigation techniques in the EHF band on a Syracuse 3 20/44-GHz low elevation link

An Earth-to-satellite propagation experiment in the EHF band has been carried out within the framework of the Syracuse 3 program, which is a new generation French military SATCOM system. The originality of this experiment resides in the link's frequencies (20 GHz downlink and 44 GHz uplink) and its low elevation angle (17°). The first part of the article presents a statistical analysis of attenuation data providing the long-term statistics, frequency scaling ratios and fade durations. These results are compared to standard ITU models. The second part of the article is dedicated to the short-term forecasting of rain fade, useful for the implementation of Fade Mitigation Techniques (FMT). Firstly, the downlink attenuation is predicted based on a non-linear ARIMA-GARCH model. The prediction result is then separated into several physical components (gases, clouds and rain) that are scaled to the uplink frequency using specific frequency scaling factors. The performance of the model is assessed based on Syracuse 3 20/44-GHz data collected during a period of 1 year.

Competitive analysis of current and upcoming satellite systems for ATM services

Satellites systems are a promising solution to cope with the capacity limitations of current air traffic control (ATC) systems. It is necessary to evaluate and assess existing and upcoming satellite systems taking into account air traffic management (ATM) requirements. This paper reviews a representative set of satellite communications (SatCom) systems and presents a competitive analysis based on objective criteria, to assess their suitability to support aeronautical services. Key drivers that should be considered for future systems design are identified and discussed. These key drivers are finally grouped to fulfil three complementary objectives that may not be possible to achieve through a single solution: improve service area, provide additional capability and capacity to existing terrestrial systems in high density airspace and to provide new services to passengers and airlines.

The ANASTASIA project: A contribution to the definition of a future aeronautical communication system

Project objectives: The core of ANASTASIA (Airborne New Advanced Satellite Techniques & Technologies in a System Integrated Approach) research is to provide on-board Communication, Navigation and Surveillance (CNS) solutions to cope with the foreseen doubling of air traffic by 2020. ANASTASIA will carry out research of future technology and system architectures for navigation, resulting in the development of a new generation of airborne Global Navigation Satellite System (GNSS) receivers for all phases of flight. Such systems will offer accurate and safe global navigation while reducing avionics cost through the optimisation of the number and complexity of on board equipment. On the communication side, work will concentrate on the design and implementation of a prototype Satcom system that will meet the evolving European Air Traffic Management (ATM) requirements. Research will also be made into higher bandwidth services, systems and airborne equipment to efficiently meet long term future aircraft communication requirements, including both ATM and passenger needs. The future needs of Surveillance will be consolidated with the requirements and key technology tests from Communications and Navigation. Expected results: The main goal of ANASTASIA is to pave the way for the introduction of new satellite-based technologies into aircraft operations in both Navigation and Communications. The main outcome of ANASTASIA will be recommendations for future civil aircraft operation and a set of evaluated technologies and avionics architectures achievable from 2010 that will enable more autonomous, satellite-based aircraft operation. Paper focus: After a general description of the rationale of the project and of its global CNS objectives, the focus is made in this paper on the communication side where more detailed objectives and initial results are presented.

Operational communication systems and relationships to the ionosphere and space weather

There are a variety of operational communication systems that are dependent upon the ionosphere, and there are others that are influenced by the ionosphere. In the dependent category, we have short-wave (i.e., MF and HF systems) and long-wave systems (i.e., VLF and LF systems). In the influenced category we have some VHF systems such as meteor-burst systems, and higher frequency SATCOM systems in the UHF and SHF bands. The paper will address various resource management issues for specified operational systems, and the relationship with aspects of space-weather will be discussed. Some examples where space-weather information is used in existing systems are presented. We also identify how space-weather information could be used in those situations where it is currently unused. We conclude with challenges facing advocates of a viable space-weather program [Goodman, J.M. Space Weather and Telecommunications. Kluwer international series of Engineering and Computer Science, Springer Science + Buisness Media Inc., New York, 2005].

Comparison of various methods for combining propagation effects and predicting loss in low‐availability systems in the 20–50 GHz frequency range

AbstractThe objective of this paper is to demonstrate the interest of using ‘combined’ prediction models of attenuation (combinations of single propagation effects) for new Ka, V or EHF SatCom systems. These models allow to calculate the attenuation due to gases, clouds, rain and the melting layer. To reach this objective, results of recent propagation campaigns carrying out radioelectrical links in the 20–50 GHz frequency range are used as references. Results from three different propagation experiments are considered in this paper: OLYMPUS results obtained from the DBOPEX database, ITALSAT results obtained by Rutherford Appleton Labs at Chilton (UK) and CELESTE results obtained by ONERA in South of France. Copyright © 2001 John Wiley & Sons, Ltd.

Management information system for the promotion of safety in shipping

Proposes the establishment of a management information system (MIS) for the promotion of safety in shipping. Considers the information technology in shipping to be the combination of satellite systems and computers onboard and ashore. In this combination, which enables the provision of an optimum selection and management of data for automatic or human decision making, the role of satcoms is information transfer and that of computers is information processing. Acknowledges the importance of the human factor in shipping safety. Human decisions affecting shipping safety often depend on the quantity and quality of the available information. In the proposed MIS the need to improve the limited ability of humans to receive, store, process and interpret information, which is usually vast and complex, is acknowledged and fulfilled. Among the available maritime satcom systems and computer services, the proposal reveals those services which satisfy the criteria of useful, interactive, flexible, fast, reliable and low‐cost transfer and management of information in support of safety‐oriented decision making in shipping operations. The proposed MIS integrates the information resources of shipping office(s), the ship(s) and the maritime‐related industry as a whole and provides the shipping company with the capability to document, monitor and control the safety‐critical aspect of “technical reliability” towards promotion of safety in shipping and compliance with the International Safety Management Code.