Satellite Switching Research Articles

Mode Switching Control for Drag-Free Satellite Based on Region of Attraction

This paper aims to propose a switching rule to improve the efficiency and stability of the mode switching process for the drag-free satellite. The switching rules will ensure the stability of the different controllers during the switching process. Unlike traditional satellite switching control, the inner loop and the outer loop of the drag-free satellite are strongly coupled. The drag-free satellite not only needs to consider the controller design in the inner loop but also the controller design of the outer loop. In the outer loop, a Proportion Integration Differentiation control method is adopted to design the controller. In the inner loop, considering the release error effect of the test mass, a nonlinear sliding-mode control is employed as a controller before the mode switch. The H∞ mixed-sensitivity controller, to improve the robustness of the system and solve the problem of controller saturation, is designed after the mode switch. In the stability analysis of the switching system, the piecewise continuous Lyapunov function method is adopted. The region of attraction, which is used as the switching rule, is calculated based on the sum of squares. The obtained results demonstrate that the proposed switching rule satisfies the control accuracy and system stability.

Space object identification via polarimetric satellite laser ranging

Low Earth orbits are becoming congested. The rapid identification and precise orbit determination of space objects is mandatory for space management. Satellite laser ranging (SLR) enables precise orbit determination by measuring the two-way photon travel time of laser pulses from a ground station to satellites equipped with retroreflectors. Here we propose polarization-modulated SLR, where specially designed retroreflectors positioned on a satellite switch the polarization state of received polarized photons and reflect them back to a ground station for analysis. Satellite identifiers can be coded into arrays of reflectors with different polarizing properties, while the orbit determining capability of conventional SLR is maintained. We design, build and test polarized light-switching retroreflector assemblies and investigate the feasibility of accurate signal measurement from SLR ground stations. The approach is passive, straightforward to integrate and requires no electricity. Polarization-modulated SLR could contribute to increasing demands of space object monitoring, for example of mega-constellations or during cluster launches.

A multi-system tightly-combined model with consideration of differential inter-systems code biases

Knowledge of differential inter-systems phase/code biases are critical to integrate observations from several different Global Navigation Satellite Systems. Many studies on tightly-combined model have mostly focused on the overlapping frequencies and short baselines, and fewer have focused on non-overlapping frequencies and medium-long baselines. Considering differential inter-systems code biases and inter-frequency code biases, we propose a tightly combined real-time kinematic model by a reparameterization process for non-overlapping frequencies among GPS/GLONASS/BDS systems. Compared with the traditional double-difference ambiguity parameter, we use single-difference ambiguity as the parameter to be estimated, which is not affected by reference satellite switching and wavelength limitation. The paper first analyzes the stability of differential inter-systems code biases and inter-frequency code biases with several zero and ultra-short baselines. Then, the paper tests the positioning performance under occlusion environment. The experiment shows that the tightly-combined model is more robust than the loosely-combined model and the average time to first fix is shortened by approximately 22.4%. At last, the paper compares the positioning performance of tightly-combined model, loosely-combined model, and tightly-combined model after calibration under the medium and long baselines. The experiment shows that the tightly-combined model after calibration is better than the tightly-combined model and loosely-combined model in the ambiguity resolution rate, initialization speed and positioning accuracy, respectively. Compared with intra-system loosely-combined model, the positioning accuracy of tightly-combined model after calibration is improved by 42.1%, 25.5%, and 32.3% in the three-dimensional directions, respectively.

Spectral Efficiency Enhancement in Satellite Mobile Communications: A Game-Theoretical Approach

Broadband satellite services, such as satellite- based Internet of Things and cloud services, have attracted much attention recently. To achieve the goal of anytime and anywhere high-speed satellite communications, there is a big demand for satellite spectrum. The push for improving spectrum efficiency in satellite systems has been an important issue, mainly from the perspectives of spectrum reuse and dynamic spectrum access. In this article, we investigate the feasibility of improving satellite spectrum efficiency from another viewpoint, that is, introducing a game-theoretical approach, including spectrum pricing and auction, for satellite spectrum dynamic allocation. Although spectrum pricing and auction have been suggested for terrestrial networks, this work aims to establish a market-inspired model to address distinct characteristic features of satellite communications. In particular, we propose a generic satellite spectrum pricing scheme, taking into account three factors: spectrum reuse in multi-beam satellite systems (MSS), where intercell interference should be mitigated; the heterogeneous nature of satellite transmission links in different spectrum bands, in which a differential pricing scheme is desirable; and predictable and periodic satellite switching from one non-GEO satellite link to another, where traffic-oriented pricing should be used. Finally, the challenges and future works in satellite mobile communications are identified.

The Algorithm of Congestion Control Based on Satellite Switching

The Algorithm of Congestion Control Based on Satellite Switching

Cross‐layer design for call admission control of a high‐capacity GEO satellite network with on‐board cross‐connect

AbstractThis paper addresses cross‐layer design of end‐to‐end call admission control and beam‐to‐beam connectivity provisioning for a high‐capacity multi‐beam GEO satellite network with on‐board cross‐connectivity. On‐board satellite switching is a technology designed to offer heterogeneous services, especially in demographically dispersed areas. Nevertheless, full on‐board switching techniques are far from maturity. Their implementations have been proven expensive and difficult. There are also high risks involved in launching satellites for the stationary orbit surrounding the Earth. As a substitute, a satellite network with on‐board cross‐connect is devised in this paper. Connectivity provisioning and call admission control mechanisms associated with such a network are also presented. Simulation studies are conducted to show the effectiveness of the proposed mechanisms. Copyright © 2006 John Wiley & Sons, Ltd.

A capture‐assisted random access scheme for multi‐beam LEO satellite packet data networks

AbstractA CDMA‐based satellite switch is proposed for use in multi‐beam satellites carrying random‐access packet‐switched data. Applications include the emerging new low‐earth‐orbit (LEO) satellite networks which support global wireless networking. Capture phenomenon is used to advantage in increasing the random access throughput, and the on‐board switch is at once simple and specially designed to handle full loads with minimal complexity. Copyright © 2004 John Wiley & Sons, Ltd.

Interferometric GPS ambiguity resolution

The Maximum a Posteriori Ambiguity Search (MAPAS) method for GPS (Global Positioning System) ambiguity resolution first introduced by Macabiau, is generalized to accommodate: (1) satellite switches caused by satellites rising or falling below the horizon or obstructing terrain, and (2) cycle slips due to temporary loss of lock on satellite signals. It is shown that MAPAS and generalized MAPAS are equivalent to Bayesian estimation. The generalized MAPAS method is successfully applied to real GPS satellite data with cycle slips and satellite switches due to satellite obstruction.

Detection of interannual variation of vegetation in middle and southern Italy during 1985–1999 with 1 km NOAA AVHRR NDVI data

The potential of NOAA‐advanced very high resolution radiometer (AVHRR) time series for environmental studies was investigated at the pixel scale. We analyzed a multitemporal set of annual maximum value composite (MVC) of normalized difference vegetation index. Local area coverage data of middle and southern Italy were processed from measurements taken between 1985 and 1999 of the afternoon viewing of NOAA 9, 11, and 14. Significant artificial anomalies were found due to satellite switch, short‐wave calibration instability and illumination effects. We removed such systematic errors and achieved a strong reduction of standard deviation values (around 50%). Interesting results were obtained from a change detection analysis performed at the pixel level. Outcomes from satellite‐based analysis were compared with independent time series data, such as ancillary meteorological data, forest fire archives, and results from field surveys. Results showed that the geographical areas where MVC data indicated a decrease in vegetation activity match well with areas affected by forest fires, intense human activity, or rapid decline of coniferous forests. In contrast, an increase in MVC was found in regions recently involved in a growth of intensive farming or invaded by alien plants which are now recognized as a threat to native species. Our exploratory results indicate that high‐quality AVHRR data can profitably support studies on interannual dynamics of surface parameters. In particular, our parameterization of illumination and calibration adjustments can be directly applied to Mediterranean‐like ecosystems.

QoS provisioning and tracking fluid policies in input queueing switches

The concept of tracking fluid policies by packetized policies is extended to input queueing switches. It is considered that the speedup of the switch is one. One of the interesting applications of the tracking policy in TDMA satellite switches is elaborated. For the special case of 2/spl times/2 switches, it is shown that a tracking nonanticipative policy always exists. It is found that, in general, nonanticipative policies do not exist for switches with more than two input and output ports. For the general case of N/spl times/N switches, a heuristic tracking policy is provided. The heuristic algorithm is based on two notions: port tracking and critical links. These notions can be employed in the derivation of other heuristic tracking policies as well. Simulation results show the usefulness of the heuristic algorithm and the two basic concepts it relies on.

Virtual prototyping for high density packaging systems

Very early in an electronic design cycle the physical buildup of a system, such as bonding method, substrate technology, and number of layers, needs to be chosen before any layout is performed. But when developing high density systems, a huge number of technology choices are available, each having impact on various aspects of the system performance. This paper describes virtual prototyping as a method for systematically analyzing and choosing the suitable buildups and selecting one of them in a cost-performance analysis for implementation and layout. Unlike former design advisors, our method analyzes several possibilities in parallel, allowing for a better design space exploration. The framework is implemented in the Java based tool JavaCAD, JavaCAD manages the different buildups and provides a size/layer count estimation for all first level interconnect/packages on various substrate technologies. It calculates the component footprints, analyzes the routing with as few data as available and allows cost estimation of all feasible buildups. The benefits of our approach are illustrated in the design of a 9:4 satellite switch operating at 2.4 GHz.

Prioritised ATM switches on board satellites: architectural analysis and design

Global broadband networking is an emerging technology aiming at providing broadband services all over the world using a constellation of satellites with on-board ATM switching capabilities. The authors propose an architecture for the ATM switches to be used on board satellites and identify both performance and physical requirements that make them distinct from terrestrial switches. Based on these requirements, a shared memory architecture is proposed. A major aspect of the switch design is the buffer management controller and the way it provides QoS to several classes of loss and delay priority traffic. A circular sorting queue is proposed as an efficient solution in terms of performance and implementation. It is also analysed using an M/G/1/K model and a supplementary variable method. This analysis is used to estimate the buffer size required and to evaluate the performance of the architecture. Some implementation guidelines for satellite switches are also discussed along with a low-power VLSI implementation of the circular queue.

System study on advanced Gigabit satellite communications

The high data rate satellite networks are expected to play an important roll in the global communications networking in the 21st century. CRL has started the three-year-long research both on system concept and key technologies of the experimental high data rate (“Gigabit”) communications satellite. New technological challenges are required for providing the connectivity for the future growing multi-media applications in the optical fiber network era; a wide area coverage with the Ka band narrow spot beams for the global high data-rate access, high-speed and flexible satellite switches, and an interoperability with the terrestrial optical fiber networks.

A high-capacity ATM switch based on advanced electronic and optical technologies

As the number of ATM broadband subscribers grows, the construction of an efficient access and tandem network will require very large ATM switches. The authors propose an architectural approach based on a concept of satellite switches of moderate capacity, loosely coupled over very high-speed links through a cross-connect core.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An optimal column-generation-with-ranking algorithm for very large scale set partitioning problems in traffic assignment

We show in this paper how branch-and-bound and column generation techniques can be conbined very efficiently to solve to optimality some very large scale set partitioning problems with special structure, such as the matrix decomposition problem arising in the context of satellite communication system optimization. The main contribution of our approach is the use of column generation during the tree search procedure, combined with a ranking procedure which ensures that the exact optimal integer solution is obtained. Extensive computational experiments are reported for the matrix decomposition problem encountered in the search for optimal schedules in satellite switching systems, showing the effectiveness of this approach.

The Challenge of 21st Century Satellite Communications: INTELSAT Enters the Second Millenium

This paper addresses the issues concerning the future of satellite communication, which will be influenced by the advancement of fiber optical cables, the proliferation of C - and Ku -band satellites, the standardization of ISDN, the requirements for new and low cost services, the economic disparity among countries, the extent of institutional policy changes, as well as technological breakthroughs. The factors will dictate and shape, both internationally and domestically, the directions of future satellite communications. In addition, the following subjects are discussed: \bullet service and traffic projections \bullet access strategies \bullet modulation alternatives \bullet satellite switching and on-board processing \bullet phase array antennas \bullet low-altitude orbit options \bullet satellite lifetime extension.

On‐board processing for communication satellites: Technologies and implementations

AbstractThis paper presents technologies which are key candidates for advanced on‐board processing for future communication satellites. Satellite switching centres for microwave and baseband signals, on‐board coherent modems for 120Mb/s burst‐mode TDMA systems and their technologies are discussed. A brief description of on‐board demultiplexing and demodulation of low bit rate carriers is offered and study results on investigation of on‐board unique word detectors and large buffers are presented.

Advanced satellite switching centre with on‐board diagnostics

AbstractDesign and operation of a satellite switching centre (SSC) with its own built‐in diagnostics network are described. This SSC, designed for on‐board applications, utilizes state‐of‐the‐art technologies and techniques which have enhanced its performance significantly when compared to similar existing satellite switching centres. Additionally, unique features of this SSC are presented, specifically with respect to the built‐in diagnostic circuit which fully describes the SSCs health without disturbance of traffic signals. Finally, system aspects of utilizing such satellite switching centres are addressed.

Satellite switch state time plan control

AbstractThis paper describes the basic control features of a typical satellite switch system, such as INTELSAT VI. Factors are addressed pertaining to the data format that is used to express the switch plan, the timing control of the switch states comprising the satellite switch frame, the transmission of the switch plan to the satellite, storage and execution of the switch plan on board, and the coding of switch plan data for protection from radiation‐induced bit errors. Also, the implementation used to achieve precision control of the on‐board clock is discussed, and the influence of clock control variation on all the terrestrial interfaces that participate in the system is demonstrated. Finally, the method for achieving network‐wide coordinated switch state time plan/TDMA burst time plan changes, which are essential in an operational satellite‐switched (SS)‐TDMA system, is discussed.

Intelsat VI. A new satellite generation for 1986–2000

AbstractFollowing three years of conceptual studies, and a competitive procurement contract, construction of the INTELSAT VI series of satellites is now under way. The design represents a major step forward in satellite size and technical complexity. Sixfold frequency reuse and on‐board satellite switching are particularly important developments.