bluuebunny/crossref_metadata_2025 huggingface dataset:
Terrestrial Microwave Communications
Authors: Smith David R.
Published: November 2003

This section on terrestrial microwave communications begins by considering free‐space propagation and the effects of terrain, atmosphere, and precipitation on propagation. Multipath fading due to ground reflection or atmospheric refraction is described with a statistical model. Diversity and adaptive equalization are shown to mitigate the effects of multipath fading on digital radio performance. Frequency allocations and planning are discussed, including the effects of interference. Components of a digital radio system are detailed, including the transmitter, receiver, antennas, diversity combiner, and adaptive combiner. Procedures are then described for calculating link performance or determining design parameters.
Multicarrier
CDMA
Authors: Kalofonos Dimitris N.
Published: November 2003

Multi‐Carrier Code Division Multiple Access (MC‐CDMA) is a multiple access scheme which combines Multi‐Carrier Modulation (MCM) and Direct Sequence CDMA (DS‐CDMA). MC‐CDMA aims at combining the bandwidth efficiency and long symbol duration inherent in MCM and the interference rejection capabilities inherent in DS‐CDMA. The use of MCM introduces frequency domain spreading in the signal design and the use of Direct Sequence Spread Spectrum (DS‐SS) time domain spreading, thus giving MC‐CDMA systems the unique possibility to spread signals in both the time and frequency domains. In fact, MC‐CDMA schemes have been proposed that cover the entire range in the frequency vs. time domain spreading trade‐off, from performing all spreading in the time‐domain (similarly to DS‐CDMA) to performing all spreading in the frequency domain (a system often referred to as OFDM‐CDMA). Among all MC‐CDMA schemes, OFDM‐CDMA has attracted the most research interest because it offers a large degree of flexibility in system design, high bandwidth efficiency and good performance with acceptable complexity. Under certain conditions OFDM‐CDMA systems can outperform DS‐CDMA, other MC‐CDMA schemes and Multiuser OFDM (M‐OFDM) at the expense of increased complexity. However, implementation issues and the operational environment can affect the performance of each system significantly and in a different way, making different schemes more appropriate in specific conditions. Therefore, no scheme is universally superior and the trade‐offs have to be considered carefully before a system design is selected.
Frequency Synthesizers
Authors: Rohde Ulrich L.
Published: November 2003

This chapter provides systematic coverage of synthesizers starting with non‐coherent synthesizers, then covering phase locked loop‐based synthesizers, as well as direct digital synthesizers. The chapter covers all important aspects of these topics and provides design guides and trade‐offs.
Loop Antennas
Authors: Siwiak Kazimierz (Kai)
Published: November 2003

Loop antennas are simple and versatile structures that appear as communication antennas in diverse applications, including pager receivers and massive multielement transmitting arrays. They are analyzed here in electrically small form as nonresonant magnetic field probes, as efficient resonated small antennas, and as large self‐resonant antennas. A rigorous generalized loop analysis here reveals details of the current density both along the loop circumference and around the wire circumference. Expressions are given for the loop impedance and loop near‐fields. The relatively low near field wave impedances make loops particularly suitable for body proximate receiving devices, while in the full wavelength‐sized structures they suitable where very high transmitter power levels are required because they are not prone to high‐voltage corona discharge problems.
Extremely Low Frequency (ELF) Electromagnetic Wave Propagation
Authors: Cummer Steven
Published: November 2003

Extremely low frequency (ELF) electromagnetic waves are currently the lowest frequency waves used routinely for wireless communication. Their ability to cover the globe with low transmitted power and to penetrate deeply into electrically conducting material makes them indispensable in a variety of applications, including communication with submerged submarines. ELF waves are also used in a variety of scientific applications, from geological remote sensing to the study of lightning, which is a strong natural ELF wave source. Transmitting controlled electromagnetic power at such long wavelengths is tricky and requires antennas rather different from those used at higher frequencies. ELF waves transmitted near the surface of the Earth are strongly reflected by the ground and the ionosphere, and thus propagate as guided waves in this spherical waveguide. The article discusses ELF transmission and reception, ELF applications, and describes in detail techniques for mathematically modeling, with varying degrees of simplicity and approximation, ELF electromagnetic wave propagation in this Earth‐ionosphere waveguide.
Microstrip Antennas
Authors: Herscovici Naftali
Published: November 2003

Microstrip antennas are probably the most popular type of planar antennas. Even though the basic microstrip element was invented in the early 50s, as a very narrow band (resonant) element, only in the last 15 years microstrip antennas have matured to the point that they are used in almost any application. Being low profile, lightweight, and relatively inexpensive, they are most suitable for military, space as well as commercial applications. Furthermore, with the latest developments in the wireless industry, the use of microstrip antennas increased exponentially.

In the same time, the theoretical work done in the area of microstrip antennas produced more than 1500 published journal articles, numerous conference papers and six books.

This chapter starts with the presentation of the rectangular microstrip patch antenna, which is widely used and lends itself to a simple, modal representation. It is inferred that most of the different geometries proposed along the years essentially behave like the rectangular patch with only minor differences in the electrical performance.

Once the rectangular patch is fully characterized as a radiating element, different feeding techniques are presented.

Then the polarizations characteristics as well as the bandwidth properties of microstrip antennas in general are discussed.

Before the discussion on microstrip arrays, the mutual coupling problem is addressed.

The last section of this chapter deals with microstrip arrays: topology, feeding networks and finally scanning arrays.
Session Initiation Protocol (SIP)
Authors: Schulzrinne Henning
Published: November 2003

The Session Initiation Protocol (SIP) is an Internet standards‐track protocol for establishing, modifying and terminating multimedia sessions, including IP telephony calls and multiparty conferences. SIP supports personal mobility, addressing users by identifiers that are independent of their current network address. SIP has been extended to notify users of events, such as the presence of people, changes in SIP‐initiated sessions and emergency conditions. SIP is also used for instant messaging (IM), delivering text or multimedia messages to one or more destinations.
Microwave Waveguides
Authors: Hajian M. , Ligthart L. P.
Published: November 2003

A waveguide is one of the most common microwave elements used in many practical systems. It can be used as a section of a transmission line or as an antenna radiator. The purpose of this article is to give an overview of the interesting parameters of waveguides, including the field configurations (modes) that can be supported by the waveguide structure. This will include the cutoff frequency, the transported power, and the wave impedance. It is also the intention of this article to introduce the readers to the difficulties concerning the excitation of electric and magnetic fields within a waveguide. The miniaturization of the waveguide using dielectric filling is discussed. The aperture matching technique using an air gap network and its design parameters are given. Dual polarized waveguides using polarization filters are analyzed and results are discussed. At the end of the article a brief discussion related to the far‐zone radiation pattern using the equivalent principal technique is discussed.
Optical Multiplexing and Demultiplexing
Authors: Stavdas Alexandros
Published: November 2003

Optical multiplexing is a technique used in optical fiber communication systems for enhancing the capacity of point‐to‐point links, as well as for simplifying the routing process within the optical layer. This technique is implemented using various types of diffraction gratings and/or optical filters in specific configurations. The parameters of these devices that have important effect on system performance are identified and their origin is explained. The principle of operation of the most noteworthy devices, as well as the corresponding specifications are presented.
Distributed Intelligent Networks
Authors: Venieris Iakovos S. , Perdikeas Menelaos K.
Published: November 2003

This article explores the concept, basic technologies and implementation issues surrounding Distributed Intelligent Networks. This telecommunications technology is shown to be based on the same set of principles and design goals that governed the definition of the traditional Intelligent Network (IN) architectures. The foundations of the Distributed IN are examined first in an abstract way to aid a quick grasping of the main offerings of this technology. Specific reference is made to the enhancements and new business opportunities that this technology explicitly enables relative to its predecessor, particularly in regard to the emerging, heterogeneous telecommunications environment. Next, the discussion delves into the more technical aspects of the Distributed IN by exploring the technologies and specifications that enable its implementation or aim to standardize common interfaces for network resources that constitute integral parts of the Distributed IN platform. Implementation issues are also covered in more detail and so do deployment strategies that allow an evolutionary roadmap to be defined. The article concludes by examining emerging architectures that, taken collectively, encapsulated many of the desired Distributed IN characteristics and features or interrelate to it in a complementary manner.
Optical Signal Regeneration
Authors: Morthier Geert , Merlier Jan De
Published: November 2003

In this chapter the different means for all‐optical signal regeneration are outlined. 3R regeneration implies signal reshaping and retiming and is based on optical decision circuits and devices for optical clock extraction respectively. In what follows, it will become clear that most of the optical decision circuits are based on active interferometers while devices for clock recovery are generally self‐pulsating laser diodes.
H.324: Videotelephony and Multimedia for Circuit‐Switched and Wireless Networks*
Authors: Lindbergh Dave , Wimmer Bernhard
Published: November 2003

ITU‐T Recommendation H.324 is the international standard for video telephony and real‐time multimedia communication systems on low‐bitrate circuit switched networks. The use of H.324 on PSTN modems, ISDN, and wireless digital cellular networks is described. The methods used in H.324 for call setup, multiplexing (H.223), system control (H.245), channel aggregation (multilink, H.226), multipoint operation, error protection for wireless channels (H.324/M and 3G‐324M) and operation on ISDN (H.324/I) are explained. The required audio and video codecs and use of data channels are described.
Terrestrial Digital Television
Authors: Wu Yiyan
Published: November 2003

A Terrestrial Digital Television (TDT) system broadcasts video, audio, and ancillary data services over the VHF and UHF bands. It is a wide‐band digital point‐to‐multipoint transmission system providing multi‐media services to the general public. This article briefly describes Terrestrial Digital Television systems and standards, as well as the services they can provide. The pros and cons of the digital television system versus analog television system are also discussed.
Local Multipoint Distribution Services (LMDS)
Authors: Papazian Peter , Dalke Roger
Published: November 2003

This article describes Local Multipoint Distribution Services (LMDS), a broadband wireless access service. The band allocation and regulations established by the Federal Communications Commission (FCC) are summarized, included the millimeter wave spectrum allocation for LMDS and interference and frequency coordination issues. Advantages and disadvantages of the millimeter wave band for broadband data transmission are presented. Propagation impairments due to rain and atmospheric attenuation are discussed analytically using current models. Measured data are used to predict area coverage, depolarization and attenuation due to vegetation, and multipath effects for the broadcast mode of transmission.
Bluetooth Radio System
Authors: Haartsen Jaap C.
Published: November 2003

Recently, a new universal radio interface was developed enabling electronic devices to connect and communicate via short‐range radio links. The Bluetooth radio technology is regarded as a complement and an extension to existing wireless technologies, addressing the short‐range and inter‐device connectivity. The technology allows the design of low‐power, small‐sized, and low‐cost radios that can be embedded in a wide range of consumer products.
Wireless
LAN
Standards
Authors: van Nee Richard
Published: November 2003

An overview is given of the history of wireless LAN standards. Several physical layer and medium access layer wireless LAN standards are described, with the main focus on IEEE 802.11 standards.
Differentiated Services
Authors: Yeom Ikjun , Narasimha Reddy A. L.
Published: November 2003

Differentiated Services (Diffserv) architecture has been proposed to provide scalable service differentiation within a network. Diffserv architecture treats the edge of the network differently from the core of the network. Customer specific service profiles are maintained at the edge of the network. These profiles are used in marking packets differently as the packets enter the network. Within the core of the network, only packet markings are used for providing service differentiation. This chapter provides an overview of the proposed diffserv architecture and the mechanisms for enabling bandwidth and delay differentiation. Analytical and quantitative evaluation of the proposed techniques is provided to highlight the salient features of the diffserv architecture. Some of the ongoing research in this area is outlined.
Paging and Registration in Mobile Networks
Authors: Rose Christopher
Published: November 2003

Mobile units in a communication network vary their points of attachment over time. The resultant uncertainty in unit location must be resolved before information can be routed to the unit. Paging is a process whereby the system searches for the unit in likely locations. Registration is a process whereby the user registers its current location. Both require precious signaling bandwidth which leads to a variety of optimization problems. This article introduces the basic ideas behind paging and registration and also provides theoretical underpinnings along with citations to allow exploration of the topic in greater depth.
Interference Avoidance for Wireless Systems
Authors: Popescu Dimitrie C. , Rose Christopher
Published: November 2003

By definition, users of a multiple access communications system share the same medium, and such shared use leads to mutual interference. The usual methods for combating interference include channel assignment, power control and receiver signal processing. Interference avoidance is a recently developed tool which presupposes the existence ofagiletransceivers which can adapt their modulation and reception methods to suit the ambient environment. Thus interference avoidance, as implied by the name, seeks to place each user in that portion of the signal space where there is least interference. Greedy iterative application of this procedure optimizes various measures of multiple access performance including sum capacity and user capacity. As such, interference avoidance should be especially useful in unlicensed environments where no central control is assumed.
Multicast Algorithms
Authors: Fei Aiguo , Gerla Mario
Published: November 2003

Multicast is a mechanism that can efficiently support multipoint or group communications. In this article, we focus on routing algorithms for multicast, i.e., how to construct a delivery structure to disseminate data for a communication group. We first discuss the concept of group communication and multicast, and then give an overview of multicast architecture in the Internet. After a brief introduction of the routing problem in a graph theory setting, we present the four major routing protocols and algorithms in the Internet, and one major more recent development to support scalable hierarchical Internetwide multicast.
Parabolic Antennas
Authors: Orfei Alessandro
Published: November 2003

The aim of this article is to introduce the important tutorial matters related to the specific field of parabolic antennas and to give an overview on the key parameters and factors to understand the operation of this widely used tool to transmit and receive radiowaves.
Community Antenna Television (
CATV
) (Cable Television)
Authors: Freeman Roger
Published: November 2003

Community antenna television
(CATV) has evolved from a comparatively simple broadband one‐way distribution system of entertainment television to a two‐way broadband multiservice telecommunication system. It now is a major contender for last‐mile connectivity for 1 Mbps+Internet, two‐way POTS, data, and ATM as well as digital television services. This article gives basic historical background of cable television, showing its evolution into a highly sophisticated broadband telecommunication entity based on fiberoptic and coaxial cable transmission. Some of the impairments peculiar to this multichannel digital and analog system are described.
Internet Security
Authors: Yener Bülent
Published: November 2003

Internet security aims to ensureConfidentiality, authentication, integrity, andnonreputiationof the “information” carried over a collection of interconnected, heterogeneous networks via messages. Although cryptography provides the building blocks, there is much to consider for Internet security. First, the network software is layered and hierarchical in which protocols at each layer interact with others at the same or adjacent layers. Insecurity of a protocol at any layer can be exploited to violate the system. Thus, security mechanisms must be carefully established at different layers of network architectures and at different network elements. Second, the software and hardware on the Internet is heterogeneous. Translating from one protocol suite to another or moving from one physical medium to another always comes with potential security risks. Finally, the Internet protocols are designed with objectives such as high throughput or low delay; however in many cases security requirements have trade offs with these performance goals. In this article we discuss various concerns on the Internet security and their remedies.
Statistical Multiplexing
Authors: Chandra Kavitha
Published: November 2003

Statistical multiplexers play a central role in the design of high‐speed multiservice telecommunications networks. As network links reach capacities of terabits per second, the multiplexing of a large number variable rate voice, video and data sources on a common channel can achieve significant savings in the bandwidth consumed by each source. This resource sharing paradigm must be examined by considering the traffic characteristics, performance requirements and multiplexing system parameters. Traffic on broadband networks is characterized by complex features that include correlation over many time scales, significant dispersion about the mean rate, nonstationary variations in average rate and variance and in some cases deterministic fluctuations. These features render classical Poisson traffic based approaches to performance analysis inaccurate. This paper presents a overview of new traffic models and performance analysis techniques for statistical multiplexing systems. The application of renewal processes, Markov chains, time‐series models and self‐similar processes as traffic models are discussed. Analytic, computational and approximate performance analyses of statistical multiplexers are reviewed. The design of admission control algorithms for controlling statistical multiplexing performance using moment matching methods, fluid flow approximations, large‐deviation principles and effective bandwidth approximations are discussed.
Network Reliability and Fault Tolerance
Authors: Médard Muriel , Lumetta Steven S.
Published: November 2003

This article introduces fundamental concepts in fault tolerance and reliability as applied to networks, with a focus on high‐speed backbone networks. We first introduce basic terminology and elements necessary to fault tolerance, then describe the basic strategies for detecting and handling failures in networks. The discussion then builds on these basics to illustrate recovery schemes for high‐speed backbone networks. An examination of the relationship between network topologies and recovery strategies follows, beginning with rings and then covering more general mesh networks. We cover some basic techniques used in packet‐switched networks, and conclude with a discussion of local‐area network approaches to fault tolerance.
Millimeter Wave Propagation
Authors: Altshuler Edward E.
Published: November 2003

The propagation characteristics in the millimeter‐region of the electromagnetic spectrum are of particular interest because the waves have a strong interaction with atmospheric gases and particulates, which in turn limits the system performance. However, the availability of large bandwidths make these wavelengths attractive for high data rate communications. Furthermore, high gain, high resolution antennas of moderate size and lightweight, compact system components are indeed applicable for space vehicle instrumentation. The limitations imposed by the atmosphere on millimeter‐wave systems are reviewed. In general, atmospheric effects become more severe as the wavelength becomes shorter.
Quadrature Amplitude Modulation
Authors: Korn Israel , Fonseka John P.
Published: November 2003

Quadrature Amplitude Modulation (QAM) is a linear method of digital modulation in which M‐ary symbols are transmitted by varying the amplitudes of two carriers in quadrature or equivalently by varying both the amplitude and phase of a single carrier. QAM requires coherent detection and linear amplifiers. QAM has an excellent bandwidth efficiency (i.e., the ratio of bit rate to occupied bandwidth is high), a moderate energy efficiency (i.e., moderate values of energy‐to‐noise ratio per bit for a given bit error probability) and a high degree of complexity at the receiver because there is a need to track the amplitude, phase and frequency of the carrier as well as to track the symbol rate and sampling time. QAM is used mainly in modems over telephone lines but its application is growing in satellite communications, coaxial cables, line of sight microwave systems and mobile communications. In this paper we first review the principles of QAM and describe the transmitter and receiver with coherent detection. Next we compute the symbol and bit error probabilities of QAM in both Gaussian and fading channels with and without diversity assuming maximum ratio combining and Nakagami‐m fading. Finally, we present various methods of carrier and symbol synchronization (blind, decision directed, with pilot tone or clock, maximum likelihood) and compute the effect on standard deviation of phase, frequency and timing estimates.
Secure Ultrafast Data Communication and Processing Interfaced with Optical Storage
Authors: Javidi Bahram , Matoba Osamu
Published: November 2003

A secure ultrafast data communication system interfaced with an encrypted optical storage system is presented. In the encrypted storage system, a large amount of data frames is stored in a holographic memory system, after each data frame to be stored is encoded by optical encryption techniques. These encrypted data readout from the storage can be sent to remote users with spatial‐temporal converters using ultrashort pulses via optical fibers. At the remote users, the retrieval of the original data can be achieved when the correct key is used in the decryption system. The operation for encryption and decryption together with data transmission using spatial‐temporal converters is described. Numerical analysis of the binary data transmission in the proposed system is also presented.
Tropospheric Scatter Communication
Authors: Monsen Peter
Published: November 2003

History, theoretical concepts, and technical features are included in a summary of radio communications by means of the scattering mechanism in the troposphere. Common radio system configurations and methods of predicting radio transmission parameters are discussed. Analog system performance and a method of analysis is included. The implicit diversity effect and reduction of intersymbol interference in digital system implementations are also presented.
Network Traffic Management
Authors: Fahmy Sonia
Published: November 2003

Traffic management aims at delivering a negotiated quality of service (QoS) to applications and at controlling congestion in a communication network. In order to accomplish these two goals, several building blocks can be used at traffic senders, receivers, core network routers, and edge routers at the entry and exit of a network domain. These components include routing based on given constraints, admission and policy control for new connections, resource reservation, packet scheduling, policing and shaping, buffer management and closed‐loop congestion control. This chapter defines these components, and discusses a number of case studies from Internet architectures.
Multimedia Networking
Authors: Bianco Andrea , Giordano Stefano , Lombardo Alfio
Published: November 2003

Multimedia networks are defined as networks providing transport services for multimedia applications. To support the QoS performance requirements of applications, multimedia networks must implement distributed mechanisms for both traffic control and resource management. In this paper the most challenging algorithms introduced in the literature to efficiently support multimedia applications are presented without reference to a specific network architecture. Later on, network technologies to deal with QoS issues are described following a historical perspective; finally we address the solutions proposed in the Internet arena.
Waveform Coding
Authors: Karabulut Güneş , Yongaçoğlu Abbas
Published: November 2003

Digital systems offer several advantages over their analog counterparts in terms of storage, processing, transmission and switching. Waveform coding is the process of representing analog signals in a digital form. In this chapter we first discuss the basic elements of digitization, namely the processes of sampling and quantization. Both scalar and vector quantization are discussed. We then present the major waveform coding techniques based on temporal and spectral processing. In the temporal coding techniques pulse code modulation, differential pulse code modulation and delta modulation are discussed. In the spectral coding techniques subband coding and transform coding are presented.
Network Security
Authors: Oppliger Rolf
Published: November 2003

This article introduces the open systems interconnection (OSI) security architecture and uses the corresponding terminology to elaborate on the state‐of‐the‐art and future perspectives of network security in general, and Internet security in particular. More specifically, the article looks into three areas that are particularly important for Internet security: access control, communication security, and intrusion detection and response. The last area is particularly important because the network security industry has shifted away from an industry that primarily focuses on the use of preventive security technologies to an industry that also takes into account the importance of detective and reactive security technologies.
Admission Control in Wired Networks
Authors: Papavassiliou Symeon , Yang Jie
Published: November 2003

With the continuous growth in traffic volume and the emergence of new services, the efficient admission control and utilization of the available network resources are required in order to meet the users' Quality of Service requirements. An admission control scheme consists of signaling messages and admission control units that perform the admission control algorithm or policy, with the objective of controlling the access of the users to the network and the allocation of the available network resources. In this article we provide an overview of the various admission control schemes and algorithms that range from resource‐based (model‐based and measurement‐based) to policy‐based admission control. We provide a detailed description of the admission control schemes and signaling procedures implemented in B‐ISDN networks that reflect the typical schemes of current connection‐oriented networks, as well as of the various schemes that can be applied in current and next generation Internet (including Intserv, Diffserv and MultiProtocol Label Switching) reflecting the tendency of future services and models.
Admission Control in Wireless Networks
Authors: Papavassiliou Symeon , Hou Jiongkuan , Ozer Sebnem
Published: November 2003

Efficient admission control and resource management schemes are required in the emerging wireless network architectures in order to maximize the utilization efficiency of the limited radio resources, while meeting the Quality of Service requirements of mobile users. In wireless networks the admission control process refers to the problem of determining whether or not to accept a user in the system, as well as of assigning to each mobile user and base station, the appropriate transmission powers, physical channels and required bandwidth. In this article the various processes associated with the admission control for both circuit switched and packet switched wireless networks are discussed, and specific mechanisms and algorithms that can be used to implement these processes are introduced. In addition, in order to balance the tradeoffs of the new call blocking and handoff call blocking according to the users' and system's requirements, various handoff priority‐based mechanisms and their relation to admission control are discussed. Finally the role and operation of the admission control in the current and future wireless networking technologies is presented.
Data Compression
Authors: Kieffer John
Published: November 2003

Lossless compression systems and lossy compression systems are the two types of data compression systems. In a lossless compression system, a lossless code is designed to encode/decode source data in order to provide the user with perfect reconstruction of the data. An efficient lossless code is one for which the compression rate in code bits per data sample is minimized or nearly minimized. The four most commonly used classes of potentially efficient lossless codes are covered: Huffman codes, enumerative codes, arithmetic codes, and Lempel‐Ziv codes. In a lossy compression system, a lossy code is designed to encode/decode source data in order to provide the user with a reconstruction of the data that is perceptually equivalent to the original data. An efficient lossy code is one which provides an attractive tradeoff between the compression rate and the distortion between the reconstructed data and the original data. The four most commonly used classes of potentially efficient lossy codes are covered: scalar quantizer based codes, vector quantizer based codes, trellis based codes, and transform codes.
Sampling of Analog Signals
Authors: Proakis John G.
Published: November 2003

Analog signals that are transmitted by a digital communication system are converted to digital form by sampling the analog waveforms uniformly at discrete instants in time. This article describes the sampling process for converting lowpass and bandpass analog signals to discrete‐time signals, which can then be quantized and converted to digital form.
Transport Protocols for Optical Networks
Authors: Moors Tim
Published: November 2003

By surveying the field of end‐to‐end transport protocols for optical networks, this article covers the requirements of such protocols, and candidate protocols. Optical networks shift the switching emphasis from packet switching towards circuit switching, so they are more likely to preserve the sequence of transmitted information and use reservation‐based congestion control, than are their (opto)electronic counterparts. This affects how transport protocols provide error control, flow and congestion control, and state management. The article evaluates the suitability of TCP for use over optical networks, as well as more specialized protocols such as SSCOP and XTP. It concludes by surveying techniques for implementing protocols to match the high speeds of optical networks.
Fading Channels
Authors: Duel‐Hallen Alexandra
Published: November 2003

Fading multipath channels are encountered in many wireless communication systems, including traditional radio communications and modern cellular and personal communication (PCS) mobile radio channels. This paper addresses characterization and modeling of fading channels. Performance issues and mitigation of fading using diversity techniques are also presented.
Multibeam Phased Arrays
Authors: Seed Randall G.
Published: November 2003

This article discusses the basic principles, design and application of phased array antennas for communications. Specifically addressed, are the implementation of multiple simultaneous antenna beams, and adaptive dynamic antenna beam positioning. Basic mathematical representations are employed to describe the concepts and principles of multibeam phased array design and analysis. Numerical examples and graphical results are used to elucidate the formalized summary descriptions. Two examples of current, novel applications of multibeam phased arrays for communication are presented, which capture the fascinating utility and implications of this technology.
Wireless
MPEG
‐4 Videocommunications*
Authors: Budagavi Madhukar
Published: November 2003

In this article we provide an overview of wireless videocommunications and described the various international standards that have made it possible. We describe the
Simple Profile
of MPEG‐4 video compression standard which in addition to specifying the video compression scheme, also introduces several error resilience tools aimed at containing the effect of transmission errors in the video bit stream. In practice, video is usually transmitted along with speech, audio, multimedia data such as images and documents, and control signals to form a complete multimedia communication system. Hence we also provide an overview of the following multimedia communication systems standards that have been recommended by Third Generation Partnership Project (3GPP) for use over third generation wireless networks: 1. Multimedia Messaging Services (MMS) for multimedia messaging, 2. Real‐time Streaming Protocol (RTSP) for streaming, 3. Session Initiation Protocol (SIP) for videoconferencing over packet‐switched wireless networks, and 4. 3G.324 for videoconferencing over circuit‐switched wireless networks.
Multiprotocol Label Switching (MPLS)
Authors: Van Heuven Pim , Van den Berghe Steven , De Turck Filip , Demeester Piet
Published: November 2003

This section introduces MultiProtocol Label Switching (MPLS) an alternative for regular IP forwarding and routing in IP networks. MPLS allows the setup of Label Switched Paths (LSPs) between IP routers to avoid the IP forwarding in the intermediate routers. This sections compares IP forwarding with MPLS forwarding. It gives an example of LSP setup. Then more details about the MPLS forwarding and signaling layers are given. The important MPLS signaling protocols: Label Distribution Protocol (LDP), Constraint‐Based LDP (CR‐LDP), RSVP extensions for LSP tunnels (RSVP‐TE) and carrying labels in BGP‐4 are described. Combing Quality of Service (QoS) (both integrated service and differentiated services) and MPLS is described. Finally, this section describes three important applications for MPLS: Traffic Engineering, Virtual Private Networks (VPN) and resilience.
DWDM
Ring Networks
Authors: Stoll Detlef , Xie Jimin , Heiles Juergen
Published: November 2003

This article describes DWDM ring networks from three viewpoints. The first viewpoint is the network architecture level. Here, the architecture of two–fiber–rings and of four–fiber rings, protection schemes, and the layer network structure of all–optical transport networks are discussed. In the second viewpoint, the network element level that comprises of the optical add/drop multiplexers (OADM) and their characteristic features (i.e., add/drop capacity, static and dynamic configuration, wavelength routing capability, transparent and opaque applications) is discussed. The third viewpoint is the component level. Tunable filters, switching fabrics, WDM multiplexers and demultiplexers, and interleaver filters are the areas discussed under this viewpoint.
Image Sampling and Reconstruction
Authors: Trussell H. J.
Published: November 2003

The chapter reviews sampling in both two‐dimensional spatial and one‐dimensional wavelength dimensions. It is assumed the reader has previously reviewed one‐dimensional sampling for time domain signals at the level of undergraduate courses. Examples are included that show the effects of undersampling in theory and practice. The reconstruction of images is presented for both reproduction of an original image and the enlargement of images that is required so often in windows‐based image analysis.
Feedback Shift Register Sequences
Authors: Song Hong‐Yeop
Published: November 2003

Feedback Shift Register (FSR) sequences have been successfully implemented in many communication systems for their randomness properties and ease of implementation. These include ranging and navigation systems, spread spectrum communication systems, CDMA mobile communication systems, and crypto systems such as streamciphers.

This article gives a brief overview of FSR sequences, both linear and non‐linear. Two conditions on the connection logic of FSRs for better output sequences are described, which are the branchless condition and the balanced logic condition. We use mostly the state transition diagram of an FSR to describe the property of its output sequences. For linear FSR sequences, we describe the relation between the connection polynomials and the structure of the cycle decomposition in the state diagram, and hence the periodicity of the output sequences.

Various randomness properties of the maximal length linear FSR sequences, known as m‐sequences, are described: balance, run‐distribution, span, ideal autocorrelation, constant‐on‐the‐coset, and cycle‐and‐add properties. Two properties, the ideal autocorrelation function and the smallest linear complexity, of m‐sequences are described in detail. Finally, a complete analysis of 4‐stage FSRs is provided.
Computer Communications Protocols
Authors: Varvarigos Emmanouel , Varvarigou Theodora
Published: November 2003

In order for computers to communicate with each other over a communication network, a common set of rules has to be agreed on, that specifies the format of the information exchange and the way data exchanged is to be handled by the communicating parts. We refer to this set of rules as a communication protocol. In this article we provide an introduction to communication protocols, starting with a description why correct communication protocols are sometimes difficult to design. We describe in some detail the OSI reference model, the ATM protocol and the very successful TCP/IP protocol suite. We also give particular examples of protocols designed to handle issues related to data link control, flow and congestion control, internetworking, and connection establishment in conventional and in high‐speed networks.
Virtual Private Networks
Authors: Steinemann Marc‐Alain , Braun Torsten , Danzeisen Marc , Günter Manuel
Published: November 2003

The tremendous growth and decreasing costs of Internet technology forced many companies to substitute expensive leased lines by connections based on Internet Protocols. This allows enterprises to establish Intranets and to offer remote employees to securely access such an Intranet. In addition, networks of different business partner can be interconnected forming Extranets. A key technology is the IP Security (IPSec) protocol suite that enhances the Internet Protocol (IP). IPSec introduces security comparable to leased lines but is much less costly due to the fact that Internet resources can be shared among different users. Such networks that are constructed using secure methods to transfer information are called Virtual Private Networks. They represent a further step towards a more secure, less costly and universal communications platform.
Carrier‐Sense Multiple Access (
CSMA
) Protocols
Authors: Georgiadis Leonidas
Published: November 2003

Carrier‐Sense Multiple Access protocols have found wide application in the deployment of Local Area Networks. In this article we present the basic principles or operation of these protocols. We start by examining the ALOHA system, the precursor of CSMA protocols. We proceed with the presentation of the variants, CSMA, CSMA/CD, that are used for wired communication, and CSMA/CA used for wireless communication.
Test and Measurement of Optically Based High‐Speed Digital Communications Systems and Components
Authors: LeCheminant Greg D.
Published: November 2003

Gauging the performance of a communications system can be accomplished in a number of ways and with a variety of parameters. We begin with a section on measuring bit error ratio, and then discuss waveform analysis.
Transform Coding
Authors: Goyal Vivek
Published: November 2003

Transform coding is source coding with a modular structure of a linear transform followed by scalar quantization and entropy coding. Ideally, the transform produces transform coefficients that are statistically independent. Then, though the encoding complexity is greatly reduced, little compression efficiency is lost by using scalar quantization and scalar entropy coding. Optimization of the transform also favors orthogonal transforms; this result and the optimal allocation of bits among the transform coefficients are developed.
Turbo Codes
Authors: Berrou Claude , Glavieux Alain
Published: November 2003

Turbo codes are multidimensional convolutional error‐correcting codes, the decoding of which relies on an iterative process, with an exchange of probabilistic information between the decoders associated with each dimension. The basic component code is a small Recursive Systematic Convolutional (RSC) code and the construction of the multidimensional code, by way of so‐called parallel concatenation, aims to mimic a very long equivalent RSC code. In practice, a bidimensional scheme is sufficient, provided that the permutation function which is used to decorrelate the two dimensions is properly designed. Under certain conditions, turbo codes are able to achieve error correction very close to the theoretical limits calculated by Shannon, by means of random coding. Turbo coding has been adopted in several essential standards (IMT‐2000, DVB, …) and is being considered as a serious candidate for channel coding in many future communication systems. The “turbo” principle, which expresses the probabilistic message passing method, has been extended to other types of processing in receivers, such as demodulation, detection and multi‐detection, and equalization.
Polyphase Sequences
Authors: Park So Ryoung , Song Iickho
Published: November 2003

In this article, we review some polyphase sequences and investigate their correlation properties and corresponding applications to cellular direct sequence code division multiple access (DS/CDMA) systems. We first consider several polyphase sequences which have perfect even autocorrelation properties and thus can be used as the long spreading sequences in intercell synchronous cellular DS/CDMA systems. We then consider some polyphase sequences possessing (near) optimum even correlation functions. These (near) optimum sequences are appropriate as the long spreading sequences in intercell asynchronous cellular DS/CDMA systems. Description of the polyphase sequences are given next which have perfect even crosscorrelation properties and thus are useful as the short signature (channelization) sequences in cellular DS/CDMA systems, followed by a brief consideration of other polyphase sequences.
Turbo Product Codes for OpticalCDMASystems
Authors: McLaughlin Steven W. , Argon Cenk
Published: November 2003

The application of turbo product codes (TPC) in intensity modulated, direct detection (incoherent) optical code division multiple access (CDMA) systems with on‐off keying (OOK) or binary pulse position modulation (PPM) is presented in this chapter. Optical multiple access interference caused by other users is the main source of noise that degrades system performance and limits the total number of active users in an optical CDMA system. Furthermore, very long optical orthogonal code (OOC) sequences are required, which results in large bandwidth expansion. The implementation of turbo product codes in an optical CDMA system promises significant improvement of the probability of bit error, permitting a higher number of active users and a system with a reduced bandwidth expansion factor. Furthermore, this level of improvement in performance is not obtainable by conventional forward error correction (FEC) codes such as Reed‐Solomon and BCH codes.
Optical Switches
Authors: Eddie Law K. L.
Published: November 2003

Extensive research has been focused on constructing the next‐generation all‐optical broadband IP networks. The design goal is to avoid having any optical‐electrical‐optical conversions in a signal path. Therefore, the optical switches are to be the core part of all‐optical networks. An optical switch may cover optical cross connects and optical add‐drop multiplexers. In this article, we focus on the design of large‐scale optical cross connects (OXCs). There are passive and active OXCs. The path settings in networks are pre‐configured if passive OXCs, made with arrayed waveguide gratings (AWGs), are used. Active OXCs enable networks to set up paths dynamically. There are several new and promising technologies developed for the active OXCs. This article is focused on micro‐electromechanical systems (MEMS), liquid crystals and thermo‐bubble‐based switches. Their future deployments will definitely have a considerable impact on all‐optical IP networks.
Acoustic Telemetry
Authors: Blackmon Fletcher A.
Published: November 2003

This article presents a comprehensive overview of the field of underwater acoustic telemetry. A brief acoustic telemetry background is provided to illustrate the difficulties involved in underwater acoustic telemetry. Example transmitter and receiver architectures required for robust performance are discussed. Current commercially available acoustic telemetry systems, i.e. modems and their capabilities are briefly mentioned. The history, development, and applications in the relatively new field of acoustic telemetry technology are discussed. The current Navy range based, telemetry modem system is discussed in some detail. A number of specific United States Naval applications related to Navy range use are presented and discussed. Areas for current and future work in the field of underwater acoustic telemetry are presented.