bluuebunny/crossref_metadata_2025 huggingface dataset:
A linear complementarity approach to the articulated multifingered friction gripper
Authors: Ai‐Fahed A. M. , Panagiotopoulos P. D.
Published: July 2007

In this article, the problem of grasping by an articulated multifingered gripper is investigated. The fingers' joints are idealized by angular and linear springs for the revolute and prismatic joints, respectively. The method, which was developed here, considers the cases of both hard and soft fingers. The unilateral frictional contact problem for the gripper‐object system is formulated as a linear complementarity problem. Numerical examples illustrating the theory are given.
Suboptimal Robot Joint Interpolation Within User‐Specified Knot Tolerances
Authors: Simon Dan , Isik Can
Published: July 2007

Approximation of a desired robot path can be accomplished by interpolating a curve through a sequence of joint‐space knots. A smooth interpolated trajectory can be realized by using trigonometric splines. But, sometimes the joint trajectory is not required to exactly pass through the given knots. The knots may rather be centers of tolerances near which the trajectory is required to pass. In this article, we optimize trigonometric splines through a given set of knots subject to user‐specified knot tolerances. The contribution of this article is the straightforward way in which intermediate constraints (i.e., knot angles) are incorporated into the parameter optimization problem. Another contribution is the exploitation of the decoupled nature of trigonometric splines to reduce the computational expense of the problem. The additional freedom of varying the knot angles results in a lower objective function and a higher computational expense compared to the case in which the knot angles are constrained to exact values. The specific objective functions considered are minimum jerk and minimum torque. In the minimum jerk case, the optimization problem reduces to a quadratic programming problem. Simulation results for a two‐link manipulator are presented to support the results of this article.
Force‐closed grasping with two hands
Authors: Caraza José‐Antonio N. , Yun Xiaoping
Published: July 2007

Two‐handed grasping of rigid objects in two‐dimensional space is studied. The hands considered in this article are either flat‐surface palms or grippers with two angular‐motion fingers. Presented in this article is a condition that establishes the existence of force‐closed grasping without the knowledge of the shape of the grasped object and of the exact contact locations on the palms or fingers. Further, an algorithm is developed that determines force‐closed grasping based on the position and orientation of the two hands.
Set point trajectory and internal force control in redundant dual‐arm manipulation
Authors: Jankowski Krzysztof P. , Eimaraghy Waguih H. , Eimaraghy Hoda A.
Published: July 2007

A nonlinear decoupling and linearizing feedback control is considered for dynamic coordination of two planar robot arms manipulating an object. A general inverse dynamics‐based method is presented that assures an exact feedback linearization for simultaneous control of the object trajectory on the plane and internal efforts transmitted from the robot end‐effectors to the object. The method takes the manipulator dynamics and object dynamics into consideration. A method for parameterizing the grip matrix null space is proposed, which has formed a basis for developing a new method for calculating the internal efforts. The procedure is invariant with respect to the change of the torque origin and units of length, and provides the force distribution without internal squeezing effects. A comparison between the approaches known so far and the new method is presented. No previously published method assures noninvariance and nonsqueezing properties for all possible contact configurations. Control algorithms are developed for a system of robotic arms that has more degrees of freedom than necessary for given tasks, exhibiting both actuation and kinematic redundancy. The implementation of this method is demonstrated for the case of a system of two planar three‐link arms with the end‐effectors manipulating an object, with different constrained task configurations. Practical aspects of discrete‐time inverse dynamics control, such as influence of the computational time delay and robustness to model imperfections, are discussed. It is demonstrated that it is possible to achieve high‐precision tracking of object position and internal force profiles, even if a system imperfect model is used for controller design. © 1993 John Wiley & Sons, Inc.
Dynamics modeling of robotic manipulators using an artificial neural network
Authors: Eskandarian Azim , Bedewi Nabih E. , Kramer Bruce M. , Barbera Anthony J.
Published: July 2007

Dynamics modeling is important for the design, analysis, simulation, and control of robotic and other computer‐controlled mechanical systems. The complete dynamic modeling of such systems involves the computationally intensive solution of a set of non‐linear, coupled differential equations. Artificial neural networks are well suited for this application due to their ability to represent complex functions and, potentially, to operate in real time. The application of an artificial neural network to dynamics modeling of robotic systems is investigated. The Cerebellar Model Arithmetic Computer (CMAC) is employed. A hybrid implementation of CMAC is proposed to allow use of the model for either simulation or control of robotic manipulators. The success of the simulated results and the accuracy of the generated outputs after a few training cycles demonstrate great promise for further development of the method and its implementation in control systems. © 1994 John Wiley & Sons, Inc.
Sensory guidance of seam tracking robots
Authors: Bahr Behnam , Haung J. T. , Ehmann K. F.
Published: July 2007

The primary goal of a seam tracking robot, based on sensory feedback, is to maintain a prescribed relationship between the end effector and the workpiece throughout the whole motion of the manipulator along the nominal path. The purpose of this article is to present the essential conceptual and theoretical features of a high‐speed seam tracking controller for sealant application. The general system configuration is discussed, followed by a brief account of the key aspects involved with the sensing of the seam location and subsequent correction command generation for the guidance of the robot. The theoretical considerations are followed by a detailed account of the physical implementation of the proposed system, with performance evaluation data obtained under actual working conditions. © 1994 John Wiley & Sons, Inc.
Learning control based on local linearization by using DFT
Authors: Manabe Tetsuya , Miyazaki Fumio
Published: July 2007

Learning control is one of the most interesting subjects in robotics field, and several works on this topic were extensively investigated. Learning control is necessary for high‐speed and high‐precision trajectory control in cases where an objective system includes uncertain parameters and/or has practical limitations on the feedback control. Conventional learning control methods, however, have a problem concerning how to determine a learning operator that guarantees the convergence of the scheme without a priori knowledge of an objective system. For instance, designing learning controllers that will work for complex robot systems, such as pneumatic robots with complicated dynamics or robots with complex sensory feedback, is extremely difficult.

This article provides a new type of learning control scheme for a class of discrete‐time nonlinear systems. The algorithm of proposed learning control utilizes local linearization techniques by usingDiscrete Fourier Transform(DFT) to design the learning operator and the numerical function iterative techniques. In our case, thesecant methodis used, which can find the bestlearning operatorby itself at each learning step, in other words, at each calculation step of iteration. This proposed learning algorithm has been extensively tested by simulation on the computer. © 1994 John Wiley & Sons, Inc.
Robot calibration by mobile camera systems
Authors: Zhuang Hanqi , Roth Zvi S. , Wang Kuanchih
Published: July 2007

A measurement technique for kinematic calibration of robot manipulators, which uses a stereo hand‐eye system with moving camera coordinates, is presented in this article. The calibration system consists of a pair of cameras rigidly mounted on the robot end‐effector, a camera calibration board, and a robot calibration fixture. The stereo cameras are precalibrated using the camera calibration board so that the 3D coordinates of any object point seen by the stereo cameras can be computed with respect to the camera coordinate frame [C] defined by the calibration board. Because [C] is fixed with respect to the tool frame [T] of the robot, it moves with the robot hand from one calibration measurement configuration to another. On each face of the robot calibration fixture that defines the world coordinate frame [W], there are evenly spaced dot patterns of uniform shape. Each pattern defines a coordinate frame [Ei], whose pose is known in [W]. The dot pattern is designed in such a way that from a pair of images of the pattern, the pose of [Ei] can be estimated with respect to [C] in each robot calibration measurement. By that means the pose of [C] becomes known in [W] at each robot measurement configuration. For a sufficient number of measurement configurations, the homogeneous transformation from [W] to [C] (or equivalently to [T]), and thus the link parameters of the robot, can be identified using the least‐squares techniques. Because the cameras perform local measurements only, the field‐of‐view of the camera system can be as small as 50 × 50 mm2, resulting in an overall accuracy of the measurement system as high as 0.05 mm. This is at least 20 times better than the accuracy provided by vision‐based measurement systems with a fixed camera coordinate frame using common off‐the‐shelf cameras. © 1994 John Wiley & Sons, Inc.
Feedback control of decoupled bending and torsional vibrations of flexible beams
Authors: Matsuno Fumitoshi , Murachi Toshihiko , Sakawa Yoshiyuki
Published: July 2007

In this article, we consider a flexible beam with a rigid body, of which the bending vibration and the torsional vibration are decoupled. Therefore we need two control motors to suppress the vibrations. Each set of dynamic equations is treated in the form of an appropriate Hilbert space. A stabilizing feedback control law of each rotation motor will be established on the basis of modal analysis. A set of experiments has been carried out, and the results demonstrate the effectiveness of the dynamic model and the proposed control law. © 1994 John Wiley & Sons, Inc.
Decentralized adaptive control of manipulators
Authors: Colbaugh Richard , Seraji Homayoun , Glass Kristin
Published: July 2007

This article presents two new adaptive schemes for motion control of robot manipulators. The first controller possesses a partially decentralized structure in which the control input for each task variable is computed based on information concerning only that variable and on two “scaling factors” that depend on the other task variables. The need for these scaling factors is eliminated in the second controller by exploiting the underlying topology of the robot configuration space, and this refinement permits the development of a completely decentralized adaptive control strategy. The proposed controllers are computationally efficient, do not require knowledge of either the mathematical model or the parameter values of the robot dynamics, and are shown to be globally stable in the presence of bounded disturbances. Furthermore, the control strategies are general and can be implemented for either position regulation or trajectory tracking in joint‐space or task‐space. Computer simulation results are given for a PUMA 762 manipulator, and these demonstrate that accurate and robust trajectory tracking is achievable using the proposed controllers. Experimental results are presented for a PUMA 560 manipulator and confirm that the proposed schemes provide simple and effective real‐time controllers for accomplishing high‐performance trajectory tracking. © 1994 John Wiley & Sons, Inc.
Stability and traction control of an actively actuated micro‐rover
Authors: Sreenivasan S. V. , Wilcox B. H.
Published: July 2007

This article addresses the issue of enhancing mobility of actively actuated vehicles by the use of optimal force distribution, and by actively controlling the location of the center of mass of the vehicle body. Force distribution in actively actuated vehicles is an underspecified problem, and optimal force distribution leads to improved contact conditions. Actively actuated vehicles also possess the ability to vary their configuration. This capability can be used to locate the center of mass of the system to further enhance mobility by providing sufficient traction, and ensuring vehicle stability, during difficult vehicle maneuvers. In this work, the general idea of control of the location of the center of mass, followed by optimal force distribution, is addressed first. This is followed by an application of these ideas to Gofor, a simple actively actuated wheeled micro‐rover system, that has been designed and fabricated at the Jet Propulsion Laboratory. An algorithm to achieve desired traction and stability has been developed. Simulation studies were performed to investigate negotiation of a vertical surface. It was found that one set of wheels readily climbed the vertical surface with the use of active mass and force distribution. This is a significant improvement over traditional wheeled vehicle systems. © 1994 John Wiley & Sons, Inc.
The dynamic effects and compensation of load transitions in robotic systems
Authors: Song Y. D. , Anderson J. N.
Published: July 2007

The problem of a robot handling a payload typically involves pre‐load, load, and post‐load stages, and payload transitions between these stages. Although considerable work has focused on the control of robots carrying payloads, few consider the problem of load transitions—one of the most important effects on system performance. This article studies these transitions and presents a compensation method. It is shown that load transitions lead to abrupt (jump) parameters and uncertain transition times in the robot/payload model. A control strategy is proposed that takes the load transitions into account and guarantees the stable path tracking of robots in the face of these transitions. The effectiveness of the proposed control strategy is verified via simulation. © 1994 John Wiley & Sons, Inc.
Unconstrained and constrained motion control of a planar two‐link structurally flexible robotic manipulator
Authors: Choi B.‐O. , Krishnamurthy K.
Published: July 2007

Unconstrained and constrained motion control of a planar two‐link structurally‐flexible robotic manipulator are considered in this study. The dynamic model is obtained by using the extended Hamilton's principle and the Galerkin criterion. A method is presented to obtain the linearized equations of motion in Cartesian space for use in designing the control system. The approach to solving the control problem is to use feedforward and feedback control torques. The feedforward torques maneuver the flexible manipulator along a nominal trajectory and the feedback torques minimize any deviations from the nominal trajectory. The feedforward and feedback torques are obtained by solving the inverse dynamics problem for the rigid manipulator and designing linear quadratic Gaussian with loop transfer recovery (LQG/LTR) compensators, respectively. The LQG/LTR design methodology is exploited to design a robust feedback control system that can handle modeling errors and sensor noise, and operate on Cartesian space trajectory errors. Computer simulated results are presented for an example planar, two‐link, structurally flexible robotic manipulator. © 1994 John Wiley & Sons, Inc.
No‐overshoot control of robotic manipulators in the presence of obstacles
Authors: Denker A. , Atherton D. P.
Published: July 2007

The long standing problem of guiding robotic manipulators in cluttered workspaces is treated here by a unified approach, taking into account both motion planning and control aspects. Planning the collision‐free operation is based on the notion of roadmaps. To reduce the complexity of the roadmaps, the real problem is approximated by a simplified but still realistic graph structure. Motion planning relies on the robot closely following the defined collison‐free path, so the errors in robot control must be contained within bounded regions. Satisfying this assumption ideally requires no‐overshoot control. Overshooting demands special attention in tasks that require high speed operations of robots in the presence of obstacles. To stabilize at the specified collision‐free trajectory, before going actually beyond it, joint control schemes demand slow movements through a number of intermediate subgoals. This significantly delays the completion of the task. By using ideas from variable structure control (VSC), a control policy is suggested here that switches between PD+ and CEA+ (constant error acceleration) schemes, where the CEA + scheme applies a “constant error acceleration” of the largest possible magnitude in the appropriate direction. The performance of the path planning and the control algorithms is presented through simulations of a four‐link SCARA robot in various cluttered workspaces. © 1994 John Wiley & Sons, Inc.
Closed form solution for the sensor registration problem using only position information
Authors: Ong Liang Eng , Everett Louis J.
Published: July 2007

Sensors, mounted on the dexterous end of a robot, can be used for feedback control or calibration. When you mount a sensor on a robot it becomes necessary to find the pose (orientation and position) of the sensor relative to the robot. This is the sensor registration problem. Many researchers have provided closed‐form solutions to the sensor registration problem; however, the published solutions apply only to sensors that can measure a complete pose (three positions and three orientations). Many sensors, however, can provide only position information; they cannot measure the orientation of an object. This article provides a closed‐form solution to the sensor registration problem applicable when: (1) the sensor can provide only position information and (2) the robot can move along and rotate about straight lines. © 1994 John Wiley & Sons, Inc.
Compliance control safety: An architecture‐independent analysis
Authors: Lawrence Dale A. , Chapel Jim D.
Published: July 2007

Safe manipulator/task interaction is defined and quantified based on interaction forces resulting from manipulator motion commands.H1andH***safety bounds are introduced for evaluation of compliance control designs deriving from any control architecture or design method. Compliance control design examples are presented to demonstrate the use of these bounds, and to demonstrate the need to consider safety bounds of the type proposed. © 1994 John Wiley & Sons, Inc.
Fuzzy logic and position sensing for precision assembly
Authors: Gürocak H. B. , De A. , Lazaro Sam
Published: July 2007

The problem of part mating and assembly with close tolerances has been addressed in the past by active or passive compliance and by force/position control. With ambient sensor and transmission noise and with imprecise measurements it is often difficult to attain high precision in manipulator positioning. In this article, a position‐sensing wrist using simple strain gauges is described. A fuzzy logic algorithm to ascertain the positional error during an unsuccessful assembly attempt is explained. The results obtained by using this wrist and the fuzzy logic algorithm to reposition a manipulator for precision assembly are presented and discussed. © 1995 John Wiley & Sons, Inc.
Optimal assignment of robot tasks with precedence for muliti‐robot coordination by disjunctive graphs and state‐space search
Authors: Lin Chi‐Fang , Tsai Wen‐Hsiang
Published: July 2007

An approach to optimal assignment of tasks with precedence relationships to multiple robots is proposed. The robots are assumed to share a common workspace and work cooperatively to accomplish a given process plan consisting of a set of tasks. The optimal task assignment is defined to be the one that results in spending the least amount of time to complete the plan under the criterion that no robot collision will occur when the assigned tasks are performed. The ordering of the tasks in the process plan is described by a topological tree, which is then expanded to form a larger state‐space tree without redundant tree paths. Each path in the expanded tree represents a partially developed assignment of the tasks to the robots, and a graph formulation scheme is presented for estimating the cost of the assignment. A collision‐free motion schedule for each robot based on each task assignment can be obtained by finding the minimaximal path in a disjunctive graph formulated by the scheme. By using the A* algorithm, a search method for finding the optimal assignment with the minimum cost is presented. Some heuristic rules are also proposed to speed up the search process. Simulation results are illustrated to show the effectiveness of the proposed approach. © 1995 John Wiley & Sons, Inc.
Perfomance‐based adaptive tracking control of robot manipulators
Authors: Colbaugh R. , Glass K. , Seraji H.
Published: July 2007

This article presents two new adaptive schemes for the motion control of robot manipulators. The proposed controllers are very general and computationally efficient because they do not require knowledge of either the mathematical model or the parameter values of the manipulator dynamics, and are implemented without calculation of the robot inverse dynamics or inverse kinematic transformation. It is shown that the control strategies are globally stable in the presence of bounded disturbances, and that in the absence of disturbances the ultimate bound on the size of the tracking errors can be made arbitrarily small. Computer simulation results are given for a PUMA 560 manipulator, and demonstrate that accurate and robust trajectory tracking can be achieved by using the proposed controllers. Experimental results are presented for an IMI Zebra Zero manipulator and confirm that the control schemes provide a simple and effective means of obtaining high‐performance trajectory tracking. © 1995 John Wiley & Sons, Inc.
Torque redistribution and time regulation methods for actuator of fault‐tolerant parallel robots
Authors: Ting Yung , Tosunoglu Sabri , Freeman Robert
Published: July 2007

In this article, we investigate and employ torque redistribution and time regulation approaches to track a preplanned trajectory while avoiding actuator saturation for redundantly actuated, fault‐tolerant parallel robots encountering actuator failure. The torque redistribution method utilizes actuation redundancies (if available) after joint failure and/or saturation to alter the torque requirements of the joints so as to avoid saturation. The time regulation method is based upon the alteration of the time to completion of the defined joint‐space trajectory. By searching for a suitable time scaling factor to change (reduce) the inertia load requirements, the robot attempts to slow down or speed up as it moves along the defined trajectory to avoid saturation. The preferred implementation strategy is to use the torque redistribution approach when redundancy is available and actuation capacity is sufficient, otherwise the time regulation approach is employed. For both methods, the computed torque technique, consisting of a model reference algorithm in the feedforward process, and a proportional plus integral plus derivative (PID) controller, to deal with modeling errors and disturbances in the feedback process, are utilized.
A new generation of modems for power efficient radio systems
Authors: Feher Kamilo , Sato Masashi
Published: July 2007

A new class of generalized intersymbol‐interference and jitter‐free (GIJF) modulated signals is introduced. Computer simulation and hardware experimental research results demonstrate that our proposed new generation of signals and modulators leads to significant performance improvements in non‐linearly amplified broadband radio systems. For increased power efficiency, non‐linear amplification is required in most commercial satellite and terrestrial microwave systems. In particular, we demonstrate that the 3 dB envelope fluctuation of currently used offset raised‐cosine overlapped QPSK systems is reduced to 0‐5 dB, and that the BER performance is improved by approximately 1 dB. These significant technical performance advantages are expected to lead to more economical implementations of digital transmission systems.
Bandwidth compressive 64‐state sqam modems for non‐linearly amplified satcom systems
Authors: Seo Jong So , Feher Kamilo
Published: July 2007

A new class of spectral and power efficient offset modes of the M‐ary QAM modulation technique, 64SQAM (superposed QAM), is analysed. The power spectrum of 64SQAM reveals a fast spectral roll‐off and a low out‐of‐band energy. P(e) performance is analysed with different baseband wave shapes of 64SQAM in AWGN linear channels. For the operation of M‐ary QAM at the highest power efficiency (i.e. at the saturation mode of HPA), a new bandwidth compressive NLA (non‐linearly amplified) 64SQAM is investigated. Retaining a compact power spectrum and allowing a simple filtering strategy, NLA‐64SQAM operates within 0–75 dB C/N degradation at P(e) = 10−6.
Effects of fade distribution on a mobile satellite down‐link and up‐link performance in a frequency reuse cellular configuration
Authors: Boutin Karl , Lecours Michel , Pelletier Marcel , Delisle Gilles Y.
Published: July 2007

In a mobile satellite system with a frequency reuse cellular configuration, significant co‐channel interference can be experienced due to the antenna side‐lobe level. The signal will be subjected not only to its own fading, but also to the effect of the varying degree of fading on the co‐channel interferer, and this interference will behave differently in the up and in the down‐link. This paper presents a quantitative evaluation of the combined effects of fades and co‐channel interference on a mobile satellite link.
Architectures for bisdn networks: A performance study
Authors: Qian Xiaomei , Wakid Shukri , Vaman Dhadesugoor , Cypher David
Published: July 2007

We explore the use of the two current architectures for broadband integrated services digital networks (BISDN) as being defined in IEEE P802.6 (local and metropolitan area network)1 and ANSI‐accredited Committee T1's T1S1.5 baseline document.2 The standard currently defines procedures for the median access control (MAC) layer and interfaces for some upper layer services. We, therefore, use the two services defined by the adaptation layer, namely messaging and streaming, to compare their relative performance. It is shown that many conditions are necessary for streaming to out‐perform messaging. We then simulate the performance behaviour of these signalling protocols required for the isochronous services of IEEE P802.6 to determine end‐to‐end delay. This allows us to extend such predictions to the use of IEEE P802.6 as a backbone for concatenated LANs.
Unified alignment of isdn‐relevant information communications services/applications through a cubic framework
Authors: Shimasaki Nobuhiko
Published: July 2007

A cubic (three‐dimensional) framework is proposed for mapping various information communications services. The framework implies the important aspect of information technology (IT), or C&C (integration of computers and communications) technology as follows. The first axis is based upon the service classification made for BISDN‐relevant services by the CCITT. This ‘communications’ axis covers not only the simple communication, or ‘space‐wise information transfer’, but also messaging, retrieval etc. as ‘the combined space/time‐wise information transfer’. The second axis represents ‘the multiplicity of media use’ in the human interface of information handling systems. The third axis represents the extent of ‘information processing/conversion’ or the level of computer technology penetration. In the latter part of this paper, the important interrelations between computer communications services and ISDN deployment are discussed using the scope of the above‐proposed cubic map. The penetration of PMI (personal machine intelligence) to the same level as telephone set and television set, and the corresponding computer communications services requirements are identified as a fundamental driving force of (N)ISDN deployment.
ISDN frame relay and its congestion control
Authors: Bhardwaj Rajeev , Jabbari Bijan
Published: July 2007

Frame relay is a new ISDN (integrated services digital network) packet mode bearer service which is expected to provide an efficient means of information transport using high‐speed transmission media. Several new applications requiring high bandwidth, such as file transfer, video and packetized voice, are suitable candidates to use this streamlined protocol. However, as there are no control frames present within the network for traffic flow management, congestion may arise during periods of peak offered loads. Efficient congestion control mechanisms are needed to make the frame relay effective. In this paper, after a brief discussion of the frame relay protocol, we consider the congestion problem in networks using this protocol and evaluate the performance. Specifically, we consider static and dynamic window flow control methods and develop models to determine the throughput under various load conditions. The throughput of the static window flow control model is determined by computing the frame loss probability and the virtual retransmission time, which is the time between arrivals of retransmitted frames at the destination. The frame loss probability is calculated by modelling the bottleneck resource as a finite state Markov chain. The results are validated by simulation. Furthermore, to analyse the dynamic interactions between the virtual circuits and their effect on the throughput and delay characteristics, we develop a simulation model which incorporates a dynamic window congestion control mechanism. It is shown that when the offered load is high, the performance of dynamic window flow control is superior to that of static window flow control.
Satellite link performance for an ss‐tdma experiment via olympus
Authors: Islam Q. , Mahmoud M. S. , Evans B. G.
Published: July 2007

The simulated results and experimental measurements of the Olympus SS‐TDMA link are presented. The degradations of the satellite link were simulated using semi‐analytic and Monte Carlo methods. These results are compared with the experimental results. The simulated results show good agreement with the measured results. The paper includes the description of the experimental test set‐up, and the operation of the acquisition and synchronization unit (ASU) along with the TDMA reference and traffic terminals used in the experiment. These tests demonstrated the reference‐to‐remote and remote‐to‐reference as well as reference station loopback tests using the SS‐TDMA payload.

The simulated results of multicarrier operation are given. These results were obtained in order to predict the degradation due to TWTA operating point, carrier fade and adjacent channel interference for the purpose of link budget analysis to achieve the required satellite link performance. The simulated results for the TWTA operating point degradation as well as carrier fade are also compared with the measured satellite link degradations.
Signal editing: A new approach to upgrade concatenated coding communications
Authors: Ng W. H. , Ng V. C.
Published: July 2007

Based on the property that correction coding is more sensitive to the number of errors than the number of erased code symbols, results of an analytical investigation to improve the performance of concatenated coding communications are presented. We propose a new tactic, ‘signal editing’, to estimate and erase unreliable data prior to the final outer decoding process. We show that signal editing has a capability to detect and delete individual erroneous digits that has not been achieved by other methods. As a result, system performance can be markedly improved. Specific recommendations for using the procedure are suggested and discussed.

We illustrate how signal editing is implemented in the case of a convolutional code with Viterbi decoding. A new concatenated (or hybrid) coding technique is constructed integrating the code with interleaving and signal editing. Performance improvement is evaluated and analysed. In this study, signal editing is derived from the information available in the Viterbi decoding process. Not limited to convolutional code with Viterbi decoding, signal editing can be applied to other linear codes without any restriction.
Response time calculation for VSAT networks
Authors: Liang Lung‐Sing , Chang Jin‐Fu
Published: July 2007

This paper calculates the response time of a VSAT network. The response time consists of network access time from VSAT terminals to the hub station, query waiting and processing time, plus response queueing and transmission delay. The calculation is first done for a VSAT network which only has a central hub. The work is then extended to a distributed environment in which regional hubs are assumed. In addition to mathematical derivations, numerical examples are given to demonstrate several interesting phenomena. Computer simulations are also provided to verify the validity of the derived results.
New computation approaches for open‐loop SSTDMA network synchronization
Authors: Shark L.‐K. , Terrell T. J. , Liu L.‐C.
Published: July 2007

This paper presents two new open‐loop synchronization algorithms for computing the satellite position. One is based on a three‐rotational co‐ordinate transformation, the other is based on a numerical iteration method. A detailed comparison of these two algorithms with other available algorithms is given with respect to accuracy of the computed separation distances between ground stations and the satellite, sensitivity to measurement and implementation errors, computation speed, and implementation complexity.
Slotted ALOHA multiple access and error control coding for land mobile satellite networks
Authors: Lutz Erich
Published: July 2007

This paper considers a satellite network with data messages being transmitted by land mobile users according to slotted Aloha multiple access. The mobile communication links suffering from multipath fading and signal shadowing are modelled as Gilbert‐Elliott channels. FEC block coding is used to correct transmission errors. The maximum achievable information throughput and the mean packet delay are derived from a combined analysis of the multiple access and FEC/ARQ protocol. The results show that the additional overhead necessary for FEC is outweighed by the benefit in throughput and delay. Finally, the capture effect and its consequences are discussed.
FODA/IBEA‐TDMA: A flexible fade countermeasure system for integrated services in user‐oriented networks
Authors: Celandroni N. , Ferro E. , James N. , Potortì F.
Published: July 2007

A flexible, processor based, TDMA station has been implemented. This station and its associated variable data rate modem enables users to implement very complex frame structures under software control. Burst rates of 512 kb/s‐8‐192 Mb/s and different coding rates are possible allowing the transmitted bit energy from each station in the network to be adapted to prevailing conditions. The proposed application of the station is the transmission of mixed stream and packet traffic, in a LANs interconnection via satellite environment, using a modification of the FODA1 technique. The association of the up‐link power control feature with the bit and coding rate variation gives the system an interesting ability to cope with fade conditions. The link outage probability is investigated for the Olympus transponder in ka band. The ability of the system, together with the good performance of Olympus, shows that the Ka band is usable for the above mentioned types of networks without prohibitive fade degradation, at least for limited coverages.
Delay performance of VSAT‐based satellite wide area networks
Authors: Chang Jin‐Fu , Lin Sung‐Hui
Published: July 2007

This paper studies the performance of VSAT‐based satellite wide area networks. Very small aperture terminals are used as transport gateways to interconnect local area networks through satellites to form a wide area network. This paper concentrates on analysing the delay of the network, which is the time needed to send a packet from a station in the source LAN to a station in the destination LAN. Several access techniques are considered for comparison. It is observed through numerical examples that TDMA on the up‐link and TDM on the down‐link offers the best delay performance.
A model for the handover traffic in low earth‐orbiting (LEO) satellite networks for personal communications
Authors: Dosiere Frédéric , Zein Tarif , Maral Gérard , Boutes Jean Pierre
Published: July 2007

The spectacular growth of cellular telephone networks has demonstrated the demand for personal communications. Communication systems based on low earth orbit (LEO) constellations of satellites seem to be an adequate approach to achieve a world‐wide network. When defining the capacity in terms of satellite circuits, the network designer has to take into account the handover traffic. Unfortunately, in a LEO communication network where handover is most often due to the network nodes motion, handover traffic models for terrestrial cellular networks cannot be used. Hence specific models must be developed. This paper proposes an analytical model for the handover in LEO satellite networks. This model is applied to different network configurations and compared to discrete‐time simulations. Simulation results agree with those obtained from the analytical model.
The intelsat K satellite
Authors: Herridge A. J. , Thompson P. T.
Published: July 2007

The INTELSAT K began life as the SATCOM K4 and was bought by INTELSAT during its initial construction phase, INTELSAT modified the K band only pay load on the satellite which was launched in June 1992 and is providing TV broadcast facilities in the Atlantic Ocean Region.
VSATS in Japan
Authors: Fujii Akira
Published: July 2007

In Japan, private domestic communications satellites, JCSAT and SuperBird, carrying Ku‐band transponders, were launched in 1989, and the use of the VSATs started. To expedite a wider use of the VSAT systems, regulations were amended in June 1989 to permit simplified licensing procedures for the VSATs which conformed to technical standards. This contribution describes the usage of VSAT systems in Japan along with the licensing procedures and the technical standards.
VSAT applications in Russian satellite communications
Authors: Dorofeev V. M. , Kantor L. Y.
Published: July 2007

The development of satellite communications in Russia tends to their application in low‐capacity voice and data systems in which earth terminals are installed directly at users premises. Low‐power small terminals employed for this purpose can be classified as VSAT‐type stations. This paper considers the applications of these terminals in voice and data transfer networks in Russia, their interaction with terrestrial systems, their basic technical characteristics and regulatory issues related to their use.
ASSESSMENT OF A PUBLIC MOBILE SATELLITE SYSTEM COMPATIBLE WITH THE GSM CELLULAR NETWORK
Authors: Priscoli Francesco Delli , Muratore Flavio
Published: July 2007

The integration between cellular networks and satellite systems is a very promising issue, since it permits the immediate provision of the radio services offered by the cellular networks to areas lacking in terrestrial facilities.

In this paper the viability of a full integration between the GSM cellular network and a satellite system is dealt with. The L‐band land mobile payload has been assumed as a reference; nevertheless the presented results can be extended to other payloads.

The basic requirement of full integration is that the insertion of the satellite system does not entail any modification of the already existing GSM network.

The integration analysis has been carried out by examining both the link feasibility and the network architecture.

As far as link feasibility is concerned, the analysis is performed by means of an ad hoc simulation tool developed at CSELT (Turin). The simulation results are displayed for GSM speech channels at both full‐rate (TCH/FS) and half‐rate (TCH/HS). Such results are used in order to compute the satellite link budgets and the satellite system capacity. The characteristics of the satellite propagation channel, of the satellite‐compatible mobile station and of the reference payload are explained as well.

As far as the network architecture is concerned, the paper identifies the most promising satellite system configuration and the satellite system counterpart of the GSM functional areas (cell, location area, MSC area). Moreover, the problems and the relevant solutions related to the extension of the main GSM procedures (e.g. call set‐up, cell selection/reselection, handover) to the integrated network are dealt with.

This paper is based upon the work performed by the authors in the framework of the European Space Agency (ESA) study: ‘Assessment of a public mobile satellite system compatible with the GSM cellular network’, Telespazio (Rome) is the prime contractor of this study.

The opinions herewith reported are not necessarily those of ESA.
THe callingSM network: A global wireless communication system
Authors: Tuck Edward F. , Patterson David P. , Stuart James R. , Lawrence Mark H.
Published: July 2007

There is a very large demand for basic telephone service in developing nations, and remote parts of industrialized nations, which cannot be met by conventional wireline and cellular systems. This is the world' largest unserved market. We describe a system which uses recent advances in active phased arrays, fast‐packet switching technology, adaptive routeing, and light spacecraft technology, in part based on the work of the Jet Propulsion Laboratory and on recently‐declassified work done on the Strategic Defense Initiative, to make it possible to address this market with a global telephone network based on a large low‐Earth‐orbit constellation of identical satellites. A telephone utility can use such a network to provide the same modern basic and enhanced telephone services offered by telephone utilities in the urban centres of fully‐industrialized nations. Economies of scale permit capital and operating costs per subscriber low enough to provide a service to all subscribers, regardless of location, at prices comparable to the same services in urban areas of industrialized nations, while generating operating profits great enough to attract the capital needed for its construction. The bandwidth needed to support the capacity needed to gain these economies of scale requires that the system use Ka‐band frequencies. This choice of frequencies places unusual constraints on the network design, and in particular forces the use of a large number of satellites. Global demand for basic and enhanced telephone service is great enough to support at least three networks of the size described herein. The volume of advanced components, and services such as launch services, required to construct and replace these networks is sufficient to propel certain industries to market leadership positions in the early 21st Century.
Carriage of SDH over satellite systems
Authors: Strange A. , Arambepola S. L. , Flavin A. J. , Stevenson A. , Thompson P. T.
Published: July 2007

This paper examines the potential of satellite systems to carry synchronous digital hierarchy (SDH) transmissions and proposes a possible earth‐station architecture capitalizing on the benefits that SDH equipment offers. It is shown that a range of SDH multiplexing rates are viable over satellite and that multi‐destination operation of satellite systems is facilitated by using the inherent features of the SDH. The use of STM‐1 (155 Mbit/s) and sub‐STM‐1 transmission rates as transmission sections along with appropriate integration of the multiplexing and modem equipment would:.

(a) enable SDH path continuity between earth‐stations, allowing the satellite network to be integrated with managed terrestrial networks to form global managed transmission platforms.

(b) provide bandwidth and equipment savings at earth‐stations.

Several technical issues relating to SDH operation over satellite systems are considered and SDH pointer corruption is examined in some detail.
Technical issues regarding satellite packet switching
Authors: Ivancic William D. , Chu Pong , Shyy Dong‐Jye
Published: July 2007

Many concepts for advanced communication satellite networks have recently been proposed. Critical technical issues relating to satellite packet switching for meshed very small aperture terminal networks and broadband networks are addressed. Hardware considerations, networking and testing issues are discussed.
Services and supporting architecture of the ESA OBP system
Authors: Barani B. , Tork H. J.
Published: July 2007

The ESA on‐board processing (OBP) satellite system using on‐board regeneration and baseband circuit switching has been designed to provide ISDN connectivity and services to users on a Pan‐European basis. It is thus seen at its periphery as a 2 Mb/s primary rate access, hence allowing for the interconnection of equipment and terminals compatible with this standard interface.

Among the various possible network architectures that the system could support, the business‐oriented closed networks look most promising. It has therefore been retained as a prime design driver for OBP system developments. Optionally, connectivity can be offered in an optimized manner to pure data networks, e.g. for LAN‐to‐LAN interconnection at rates up to 1 Mb/s. In the paper, communication services and networking capabilities offered by the system are briefly reviewed. The internal characteristics of the satellite system allowing for such capabilities are then reviewed and the corresponding performance outlined. The system is shown to be compatible with critical CCITT performance criteria.
Hybrid satellite and terrestrial networks
Authors: Chitre D. M. , Shyy D.‐J. , Ephremides A. , Gupta S.
Published: July 2007

The role of satellite communications in networks that provide new services, such as frame relay and multimedia, is investigated. Both passive and active (on‐board switching/processing) satellite systems are considered. Novel techniques are developed for each system to demonstrate, via detailed analysis and simulation, how the communications bandwidth agility of multipoint/broadcast satellite channels, and the on‐board switching/processing, makes it feasible to provide these new services via hybrid satellite and terrestrial networks in a resource‐efficient manner.
A new method for the prediction of fade duration statistics in satellite links above 10 GHz
Authors: Paraboni Aldo , Riva Carlo
Published: July 2007

A model for the statistical prediction of fade durations, applicable both to scintillation and rain‐induced effects, is presented in this paper. It assumes that durations longer than about 1 minute are lognormally distributed whereas shorter durations follow a power‐law distribution. The model is assessed using data contained in the CCIR data bank and from measurements performed with the SIRIO and Olympus satellites. The model is tested using the same data, and the results give multiplicative errors in the range from 0.6 to 1.8 (averages) and from 0.3 to 3.0 (r.m.s.) in the estimation of the fade durations exceeded for fixed probability.