bluuebunny/crossref_metadata_2025_split huggingface dataset:
Perfomance‐based adaptive tracking control of robot manipulators
Authors: Colbaugh R. , Glass K. , Seraji H. 
Published: July 2007

AbstractThis 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

AbstractIn 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

AbstractA 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

AbstractA 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

AbstractIn 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

AbstractWe 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

AbstractA 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

AbstractFrame 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

AbstractThe 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

AbstractBased 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

AbstractThis 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

AbstractThis 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

AbstractThis 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

AbstractA 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

AbstractThis 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

AbstractThe 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.
VSATS in Japan
Authors: Fujii Akira 
Published: July 2007

AbstractIn 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

AbstractThe 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

AbstractThe 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

AbstractThere 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

AbstractThis 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.