Search

The article presents references of several publications related to VSAT networks. Some of those research papers are "Fundamental of Packet Multiple Access for Satellite Networks," published in "IEEE Journal on Selected Areas in Communications." The other research paper "The TSAT System--A Novel Low Cost Closed SATCOM Network for Low Data Rate Communication," presented at the International Conference on Digital Satellite Communications. Research paper "Static and Dynamic Retransmission Control for Slotted ALOHA in Transmission Channels With Erasure and Capture," published in the journal "International Journal of Satellite Communications."

The article gives information about a chapter of the book "Telecommunications Optimization: Heuristic and Adaptive Techniques," edited by David W. Corne, Martin J. Oates and George D. Smith. In the last two decades, wireless communication systems such as cordless phones, paging systems, wireless data networks, satellite-based and cellular mobile systems have been steadily increasing in both popular importance and technological sophistication. The twin goals of this chapter are to familiarize mobile communication engineers with global search techniques and their potential, and to provide those interested in these techniques with an idea of the nature and scope of their application to mobile communications.

Smart antennas constitute a promising hut still emerging technology. Space-time processing algorithms provide powerful tools to enhance the overall performance of wireless cellular networks. Improvements, typically by a factor of two in cell coverage or capacity, are shown to be possible according to results from field deployments using simple beamforming. Greater improvements can be obtained from some of the more advanced space-time processing solutions described in this paper. The successful integration of space- time processing techniques will however also require a substantial evolution of the current air interfaces. Also, the design of space-tune algorithms must also he application- and environment-specific. [ABSTRACT FROM AUTHOR]

The article presents information on wireless communications. The field of mobile wireless communications is currently one of the fastest growing segments of the telecommunications industry. Wireless devices have nowadays found extensive use and have become an indispensable tool on the everyday life of many people. both the professionally and personally. To gain insight into the momentum of the growth of the wireless industry, it is sufficient to state the tremendous growth in the number of worldwide subscribers of wireless systems. This figure has risen from only one mobile subscriber per 100 inhabitants worldwide in 1990 to 26 subscribers per 100 inhabitants in 1999 and the growth continues. This increasing number of subscribers is obviously reflected in monetary terms as well.

The article discusses simulation of wireless network systems. Simulation is a general term that is used in many disciplines including performance evaluation of computer and telecommunications systems. A model is a description of a system by symbolic language or theory to be seen as a system with which the world of objects can be expressed. The article also reviews the main characteristics of the commonly used stochastic distributions used for the simulation of wireless networks. The article concludes with cases studies on the simulation of some wireless network systems.

Discusses wireless data networks. Concept of internetworking; Functions of the Open System Interconnection (OSI) reference model; Purposes of each layers of the OSI model.

The article focuses on fixed wireless access systems. The goal of this chapter is to review the main techniques used for Wireless Local Loop (WLL) including the Multichannel Multipoint Distribution Service, and the Local Multipoint Distribution Service. It is expected that the global WLL market will exceed 202 million subscribers by the year 2005. Much of this growth will be in the developing countries where over half the world's population lacks Plain Old Telephone Service. WLL systems have a number of advantages over wired systems to subscriber local loop support.

Focuses on the history of wireless technologies. Concept of the operational wireless telegraph apparatus developed by Guglielmo Marconi; Timeline on the evolution of wireless technologies; Functions of packet radio.

The article focuses on Point-to-multipoint (PMP) network architecture. PMP network architecture is the most widely used approach for electronic communication with a large number of destinations or nodes. It is used for wired telephone systems in which twisted wire pairs from each phone terminal are routed to a central office where calls are placed on shared trunk circuits for onward routing. The wired PMP networks provide service to discrete locations, whereas the wireless systems listed are designed to provide service to an area where the specific locations of the service users are usually unknown.

Any continuous-time analogue signal can be converted into a digital signal by making discrete both the time and the amplitude axes. The process of making the amplitude axis discrete is called quantization. It consists of dividing the amplitude axis in contiguous intervals and in associating to all the amplitudes within any interval a single amplitude value chosen among them. A regenerator receives the incoming pulse stream and transmits a new regenerated pulse stream that replicates the original sequence as closely as possible. To regenerate the signal, timing information must be known so that the regenerated pulse stream can be transmitted with the proper intervals between the pulses.

Non-GEO satellite systems can help to meet the demand for information by providing global access to the telecommunications infrastructure, currently available only in advanced urban areas of the developed countries. Like GEO satellites, non-GEO satellites also provide a means of interconnecting LAN on a global basis. The main advantage of the deployment of non-GEO satellites is their relatively low altitudes in comparison with GEO satellites. This enables non-GEO satellites, especially LEO satellites, to provide services with delay which is compatible, or nearly compatible, with that introduced by the terrestrial networks. Because of their lower altitudes, lower power terminals are possible. This in turn has a positive effect in the size and cost of the terminals. The evolution from GEO to LEO satellites has resulted in a number of global satellite systems such as the Iridium, which is now in the sky, the Globalstar and ICO.

Chapter 1 gives a brief introduction on the evolution of satellite communications and the services being envisaged to be provided by satellite systems. A discussion on different EU initiatives in supporting the development of satellite communications is also presented. The operating frequencies of and technical issues in satellite systems operations for network interconnection are also addressed. Finally, the objectives and activities under the COST Action 253 are described. [ABSTRACT FROM PUBLISHER]

In the future, radio communication systems will offer different services through single user equipment; furthermore, it is expected that different radio communication systems will merge into one universal communication system. Today, there are two known concepts for providing wireless communication services: terrestrially based communication systems and satellite communication systems. Each concept has its specific characteristics, and consequently, advantages and disadvantages. The main disadvantages of terrestrially based systems are: poor radio channel quality, Rayleigh fading limits the cell radius and transmitted data rate and; and Terrain shadowing causes gaps in radio coverage.

This article presents information on voice communications in a military environment. The main threats to voice communications in a military environment are eavesdropping, impersonation and illegal access to the medium. The degree of threat depends very much upon the political climate of the region involved and whether or not any parties are taking an aggressive stance towards a neighbour. There is much evidence of communications naivety in many parts of the world, and as a result, many a nation's sensitive data have been freely available to those who care to listen. The relaxed attitude that often prevails on the subject of communications security in peacetime enables eavesdroppers to build up a big picture from fragments of information. In a military scenario, "stand-alone" ciphering devices might, on first consideration, seem to be an unnecessary complication in a security strategy.

Presents an overview of the book "W-CDMA: Mobile Communications System," edited by Keiji Tachikawa. Generation change in cellular systems; Objectives of the International Mobile Telecommunications (IMT)-2000; Standardization of the IMT-2000.

The appendices (39 pages) give supplementary information on: queuing systems for traffic performance analysis, standards and recommendations of ISO, ITU, IEC, INTELSAT/INMARSAT, ATM Forum, CEN/CENELEC, CEPT, ETSI, ECMA, EBU, EUTELSAT, ESA and others. International Frequency Allocations, The Frequencies of European Mobile Radio Systems, The GSM Standard. [ABSTRACT FROM PUBLISHER]

Chapter 2 (93 pages) explains the fundamentals of radio transmission like attenuation of radio waves, propagation over flat terrain, multi-path fading, statistics of the transmission channel, reflection, diffraction, RMS delay spread, shadowing, interference caused by other systems. Models to calculate the radio field, namely empirical models and diffraction models, ray tracing techniques and the famous Okumura/Hata model are introduced. [ABSTRACT FROM PUBLISHER]

The article provides various information including preface and table of contents of the book "Mobile Fading Channels." The book is based on the author's version originally in German. It is addressed to engineers, computer scientists and physicists, who work in the industry or in research institutes in the wireless communications field. The author's experience and prerequisite knowledge required to understand the book, has been mentioned. MATLAB programs are also provided in the text for better understanding of concepts. The book aims to provide fundamentals of modeling, analysis, and simulation of mobile fading channels.

Chapter 1 discusses the handoff, which is the mechanism for transferring an ongoing call from one base station to another as a user moves through the coverage area of a cellular system. Admission control is a related problem, in which the radio resource management system has to decide if a new call arrival, or a request for service or handoff may be allowed into the system. Four conventional handoff schemes in a voice-based, single traffic system are summarized and two handoff schemes for integrated voice and data wireless mobile networks are also covered in detail. [ABSTRACT FROM PUBLISHER]

Chapter 17 reviews the existing routing algorithms for wireless networks of nodes that are not aware of their geographic positions. Routing the message (finding a path between a source and a destination node) is a basic data communication protocol in mobile ad hoc networks, consisting of hosts that communicate without the assistance of base stations. [ABSTRACT FROM PUBLISHER]

Chapter 13 focuses on the transport layer in micro-cell and macro-cell wireless networks. The task in the transport layer is to organize the speed of transmission, acknowledgement and possible retransmission of every packet of a data transfer. It deals primarily with network congestion and reduced bandwidth problems. [ABSTRACT FROM PUBLISHER]

The views expressed in this section are those of the author and do not necessarily reflect the views of his affiliation entity. [ABSTRACT FROM PUBLISHER]

Chapter 28 focuses on design issues and options for the physical layer, and media access control layer protocols (IEEE 802.11, HomeRF and Bluetooth) that have been proposed for the indoor wireless environments. Network topology and self-organization of such networks, with special reference to Bluetooth, are also discussed. [ABSTRACT FROM PUBLISHER]

Chapter 23 reviews multicasting protocols for wired networks, cellular networks (characterized by a fixed infrastructure with mobile end nodes) and ad hoc networks (infrastructure-less mobile networks). In a multicasting problem, a message is to be sent from a node to several other nodes in the network. [ABSTRACT FROM PUBLISHER]

The views expressed in this chapter are those of the author and do not necessarily reflect the views of his affiliation entity. [ABSTRACT FROM PUBLISHER]

The views expressed in this module are those of the author and do not necessarily reflect the views of his affiliation entity. [ABSTRACT FROM PUBLISHER]

The views expressed in this chapter are those of the authors and do not necessarily reflect the views of their affiliation entity. [ABSTRACT FROM PUBLISHER]

The views expressed in this module are those of the author and do not necessarily reflect the views of his affiliation entity. [ABSTRACT FROM PUBLISHER]

The views expressed in this section are those of the author and do not necessarily reflect the views of his affiliation entity. [ABSTRACT FROM PUBLISHER]

The views expressed in this chapter are those of the author and do not necessarily reflect the views of his affiliation entity. [ABSTRACT FROM PUBLISHER]

The article presents preliminary information on the January 2002 issue of the journal "GSM and UMTS: The Creation of Global Mobile Communication."

The article presents information about the fourth-generation mobile systems, technology to be used in the field of wireless communication systems. Fourth-generation mobile systems require high data-rate transmission, high mobility, wide area coverage, higher capacity and wireless QoS (quality of service resource control). The requirement for broadband wireless channels and guaranteed quality of service (QoS) will become more stringent in mobile data communications. There is an idea to include new communication systems such as Intelligent Transport Systems and High Altitude Stratospheric Platform Station systems at a research level.

Chapter 10 focuses on the indoor system of BRAIN, a mm-waveband high-speed multimedia wireless LAN. It discusses the architecture and design of the prototype; a description of a wireless MAC protocol; the configuration and implementation of the system. [ABSTRACT FROM PUBLISHER]

Chapter 11 proposes a private branch exchange (PBX) based mobility manager for WLL, which allows users to receive wireless service at any location within the WLL service area. [ABSTRACT FROM PUBLISHER]

Chapter Four covers modulation aspects. Especially it contains: a thorough presentation of the trellis coding modulation theory; aspects on the combination of trellis quantization and modulation schemes; an investigation of the performance of Combined TCQ/TCM scheme over the wireless local loop environment; an example of a 4‐state combined trellis coded quantization/modulation scheme over a WLL environment. [ABSTRACT FROM PUBLISHER]

Chapter Six covers a channel model analysis based on a series of measurements carried out at 2GHz designed to characterize a wide band WLL in a range of environments; An experimental procedure used in two measurement campaigns; The data processing stages used to determine the channel parameters; The channel model used. [ABSTRACT FROM PUBLISHER]

Focuses on the factors that led to the innovation of universal mobile telecommunication systems (UMTS). Increase in the mobile multimedia market; Emergence of new terminals or smart phones; Industrial opportunity of UMTS cited by manufacturers.

This chapter focuses on communications subsystem performance enhancements potentially attainable via use of vibrating micromechanical resonator circuits in MEMS-based transceiver architectures. Section 12.2 begins by reviewing the issues involved with transceiver miniaturization, specifically focusing on the need for high Q. Section 12.3 follows with an overview of various micromechanical signal processing circuits, describing micromechanical tanks, filters, mixer-filters, and switches and providing sufficient detail to facilitate the incorporation of such circuits into communications subsystems. Specific transceiver architectures using such devices are then presented in Sections 12.4 and 12.5, with a focus on the specific performance enhancements afforded by each approach. Section 12.6 then serves as a reminder that this is still a fledgling technology, emphasizing the present limitations of this technology and giving a sprinkling of the specific research problems that must be solved before the architectures of Sections 12.4 and 12.5 can become a reality. Sections 12.7 and 12.7.4.1 finally close the chapter with details on techniques for combining mechanical and transistor circuits onto single chips. [ABSTRACT FROM PUBLISHER]

Can a silicon-based technology like Si/SiGe HBT exhibit performance compatible with the demands of the low-power wireless communications marketplace, and does it retain the low cost and manufacturability of its silicon pedigree? This chapter will attempt to answer that question by summarizing the progress and prospects for this technology in the area of low-power mobile communications systems, with particular emphasis on circuit and device performance. It is organized in the following manner. Section 4.2 outlines the advantages and disadvantages of silicon technology for applications to high-frequency low-power communications circuits. Section 4.3 summarizes the key device design aspects of SiGe devices, particularly with respect to high-frequency applications. Section 4.4 provides an assessment of passive component technology in Si/SiGe technology. Section 4.5 provides a direct comparison of the performance of silicon-based HBTs to those based on III-V technologies. Finally, Section 4.6 provides an overview of reported circuit performance in Si/SiGe HBT technology, with emphasis on low-power communications applications. [ABSTRACT FROM PUBLISHER]

This chapter describes a series of novel concepts to increase microwave power amplifier efficiency. Within modern wireless systems, power amplifiers must meet exacting linearity specifica-tions, which tend to be at odds with the need for high efficiency. To characterize these specifications and associated trade-offs, the authors first review the linearity requirements and dynamic range requirements of representative high performance communication systems. They then demonstrate concepts for power amplifier improvement that can meet the system requirements. [ABSTRACT FROM PUBLISHER]

Following a brief overview of the basic constructing elements for modern planar microwave/millimeter-wave passive circuits, this chapter presents two innovative approaches to meet the above-mentioned technical challenges of high-Q passive components for high-frequency applications. The first approach, based on a unique process named SIMPOL (silicon/metal/polyimide), aims at realizing low-loss, high-isolation interconnects and passive components on low-resistivity, CMOS-grade silicon substrates. The second approach for high-Q passive components is based on the photonic bandgap (PBG) concept. These are basically periodic structures that can be used to control the propagation, reflection, or radiation of electromagnetic waves in a slightly different way compared to conventional waveguiding or filtering techniques. [ABSTRACT FROM PUBLISHER]

In this chapter, a variety of state-of-the art planar antennas is presented, as well as several new active architectures that take full advantage of the high performance, low profile, low cost, and low weight of this still developing field of antennas. While the broad scope of research that has been done in the areas of planar antennas and AIA systems in the last few decades prevents a comprehensive overview, it is hoped that the examples and issues discussed in this chapter provide a sufficient "flavor" of the field to show its true potential. [ABSTRACT FROM PUBLISHER]

Chapter 4 is concerned with characterising the propagation channels over which a mobile satellite network operates. Both mobile and fixed transmission environments are considered. Narrow-band modelling of the mobile environment is presented in terms of empirical and statistical solutions. The review of empirical models includes the Empirical Roadside Shadowing Model. Statistical models include those developed by Loo and Lutz respectively. The current state of wide-band channel modelling is also reviewed, as is the use of geometric-analytical techniques. [ABSTRACT FROM PUBLISHER]

The article presents information about the January 1, 2004 issue of the journal CDMA: Access and Switching. Code division may be considered as a generalized method for access and switching in communication networks. Such an approach may be viewed as a user encoding process where the choices of the code and spreading types can create a large set of access and switching techniques in which the traditional ones are included. In this sense, code division can provide a unified approach for multiple access and switching in communications.

The article discusses a chapter of the book "Telecommunications Optimization: Heuristic and Adaptive Techniques." This chapter considers network planning and impact analysis for the plain old telephone system. In the past, new network designs were predominately undertaken by human planners using simple manual or partially automated methods. The methods employed were characteristically labor-intensive with relatively low levels of productivity. A planner, for example, would usually be expected to design a typical network layout within three working days. Generally, this work would entail two stages or more of design iteration, each stage taking twelve hours.

The article discusses a chapter of the book "Telecommunications Optimization: Heuristic and Adaptive Techniques." This chapter focuses on design of minimum cost reliable communications networks when a set of nodes and their topology are given, along with a set of possible bi-directional arcs to connect them. A variety of approaches are cited, and the previous work of the authors using genetic algorithms is discussed in detail. It must be noted that the design problem solved by these methods is significantly simplified. A large number of components and considerations are not treated here.

The article gives information about genetic programming for optical mesh network topology design. Mesh network topology design starts with a set of node locations and a traffic matrix, and determines which of the node pairs are to be directly connected by a link. The design is guided by an objective function, often costbased, which allows the fitness of candidate networks to be evaluated. In the more specific problem of the topology design of multi-wavelength all-optical transport networks, the nodes would be optical cross-connects, the links optical fibres, and the traffic static.

Recent measurements of local-area and wide-area traffic have shown that network traffic exhibits variability at a wide range of scales. What is striking is the ubiquitousness of the phenomenon, which has been observed in diverse networking contexts, from Ethernet to ATM, LAN and WAN, compressed video, and HTTP-based WWW traffic. Such scale-invariant variability is in strong contrast to traditional models of network traffic, which show burstiness at short time scales but are essentially smooth at large time scales; that is, they lack long-range dependence. Since scale-invariant burstiness can exert a significant impact on network performance, understanding the causes and effects of traffic self-similarity is an important problem. [ABSTRACT FROM PUBLISHER]

The presence of scaling behavior in telecommunications traffic is striking not only in its ubiquity, appearing in almost every kind of packet data, but also in the wide range of scales over which the scaling holds. It is rare indeed that a physical phenomenon obeys a consistent law over so many orders of magnitude. This may well extend further, as increases in network bandwidth over time progressively "reveal" higher scales. [ABSTRACT FROM PUBLISHER]

Most of the modern telecommunications operators who are applying for radio spectrum allowing them to operate WLL (Wireless Local Loop) services are planning to offer a multimedia portfolio of voice and broadband data services. This chapter describes the different classes of equipment which have been developed by equipment manufacturers as a means for offering 'broadband wireless access'. In addition, it discusses the specific considerations which should accompany the planning and operation of such a network. [ABSTRACT FROM PUBLISHER]