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Showing papers in "IEEE Communications Magazine in 1996"


Journal ArticleDOI
TL;DR: This article provides an overview of H.263, the new ITU-T Recommendation for low-bit-rate video communication, which specifies a coded representation for compressing the moving picture component of audio-visual signals at low bit rates.
Abstract: This article provides an overview of H.263, the new ITU-T Recommendation for low-bit-rate video communication. H.263 specifies a coded representation for compressing the moving picture component of audio-visual signals at low bit rates. The basic structure of the video source coding algorithm is taken from ITU-T Recommendation H.261 and is a hybrid of interpicture prediction to reduce temporal redundancy and transform coding of the prediction residual to reduce spatial redundancy. The source coder can operate on five standardized picture formats: sub-QCIF, QCIF, CIF, 4CIF, and 16CIF. The decoder has motion compensation capability with half-pixel precision, in contrast to H.261 which uses full-pixel precision and employs a loop filter. H.263 includes four negotiable coding options which provide improved coding efficiency: unrestricted motion vectors, syntax-based arithmetic coding, advanced prediction, and PB-frames.

1,280 citations


Journal ArticleDOI
TL;DR: A number of important multiuser DS-CDMA detectors that have been proposed are described, where information about multiple users is used to improve detection of each individual user.
Abstract: Direct-sequence code-division multiple access (DS-CDMA) is a popular wireless technology. In DS-CDMA communications, all of the users' signals overlap in time and frequency and cause mutual interference. The conventional DS-CDMA detector follows a single-user detection strategy in which each user is detected separately without regard for the other users. A better strategy is multi-user detection, where information about multiple users is used to improve detection of each individual user. This article describes a number of important multiuser DS-CDMA detectors that have been proposed.

1,234 citations


Journal ArticleDOI
TL;DR: The fundamental technical challenges and business motivations behind wireless position location systems are described, and promising techniques for solving the practical position location problem are treated.
Abstract: With the advances in wireless communications and low-power electronics, accurate position location may now be accomplished by a number of techniques which involve commercial wireless services. Emerging position location systems, when used in conjunction with mobile communications services, will lead to enhanced public safety and revolutionary products and services. The fundamental technical challenges and business motivations behind wireless position location systems are described, and promising techniques for solving the practical position location problem are treated.

659 citations


Journal ArticleDOI
TL;DR: The author presents an overview of published work on handover performance and control and discusses current trends in handover research, and focuses on macrocells, but includes a brief discussion on how things change as cell sizes shrink.
Abstract: Handover is the mechanism that transfers an ongoing call from one cell to another as a user moves through the coverage area of a cellular system. As smaller cells are deployed to meet the demands for increased capacity, the number of cell boundary crossings increases. The author presents an overview of published work on handover performance and control and discusses current trends in handover research. He discusses investigations that are applicable to a single tier of cells. He focuses on macrocells, but includes a brief discussion on how things change as cell sizes shrink. By assuming an overlay of macrocells and microcells he summarizes issues and approaches unique to such systems.

586 citations


Journal ArticleDOI
TL;DR: The authors describe a network management system and illustrates its application to managing a distributed database application on a complex enterprise network.
Abstract: The authors describe a network management system and illustrate its application to managing a distributed database application on a complex enterprise network.

404 citations


Journal ArticleDOI
TL;DR: This work quantitatively compares the performance of three call admission control schemes proposed for ATM networks and reviews the salient features of some of these algorithms.
Abstract: Over the last few years, a substantial number of call admission control (CAC) schemes have been proposed for ATM networks. We review the salient features of some of these algorithms. Also, we quantitatively compare the performance of three of these schemes.

311 citations


Journal ArticleDOI
TL;DR: An overview of ITU-T Recommendation H.323, "Visual telephone systems and equipment for local area networks which provide a non-guaranteed quality of service," which provides the capability to have global multimedia communications from the desktop using existing network infrastructures.
Abstract: This article provides an overview of ITU-T Recommendation H.323, "Visual telephone systems and equipment for local area networks which provide a non-guaranteed quality of service." This recommendation applies to multimedia communications over packet-switched networks, such as Ethernet, which run TCP/IP, IXP/SPX, or other related protocols. In addition to the multimedia terminal, other H.323 components are defined which provide for conference admissions (gatekeeper), multipoint communications (multipoint controller, multipoint processor), and interoperability (gateway) with terminals on other types of networks. H.323 has application to a variety of network media, including local area networks, enterprise networks, metropolitan area networks, wide area networks, dial-up line connections to LANs, and the Internet. This provides the capability to have global multimedia communications from the desktop using existing network infrastructures.

250 citations


Journal ArticleDOI
TL;DR: The article considers the network layer by discussing extensions that are being made to the widely used Internet protocol (IP) to deal with mobility (wired or wireless) and speculating on future directions for wireless LAN systems.
Abstract: The emerging widespread use of wireless LAN systems together with the users' desire for such systems to interoperate has created a requirement for standards. Many standards bodies are currently defining standards for wireless systems that relate to different layers of the networking protocol stack. Of these, two influential physical and data link layer standards, IEEE 802.11 and the European HIPERLAN, are described. The article then considers the network layer by discussing extensions that are being made to the widely used Internet protocol (IP) to deal with mobility (wired or wireless). The final standards that are discussed relate to wireless link management. The article concludes by speculating on future directions for wireless LAN systems.

186 citations


Journal ArticleDOI
TL;DR: A currently available standard for location management is described and research results on location management are surveyed in detail.
Abstract: Personal communications services (PCS) support mobile terminals (MTs) which are free to travel within the service coverage area. In order to effectively locate an MT when a called is initiated, location management schemes are used to keep track of the locations of the MTs. The current approach to location management requires each MT to report its location to the network periodically. The location information is then stored in databases. When a call is initiated. The network determines the current location of the called MT through a database lookup and paging procedure. A currently available standard for location management is described. Research results on location management are surveyed in detail.

148 citations


Journal ArticleDOI
TL;DR: The authors study the problem of fair rate allocation, specifying the requirements of a fair Rate Allocation Algorithm, and provide a survey of various proposedFair rate allocation strategies in the context of the ABR service.
Abstract: A central issue in congestion control for the available bit rate (ABR) service in ATM networks is the computation of the fair rate for every connection at each switching node in the network. The objective is to determine the fair rate for all the connections in a distributed network under dynamic changes in the absence of centralized knowledge about the network, and without the synchronization of different network components. The authors study the problem of fair rate allocation, specifying the requirements of a fair rate allocation algorithm, and provide a survey of various proposed fair rate allocation strategies in the context of the ABR service.

143 citations


Journal ArticleDOI
R.V. Cox1, P. Kroon
TL;DR: The attributes of speech coders such as bit rate, complexity, delay, and quality are described, which are applicable to low-bit-rate multimedia communications.
Abstract: The International Telecommunications Union (ITU) has standardized three speech coders which are applicable to low-bit-rate multimedia communications. ITU Rec. G.729 8 kb/s CS-ACELP has a 15 ms algorithmic codec delay and provides network-quality speech. It was originally designed for wireless applications, but is applicable to multimedia communications as well. Annex A of Rec. G.729 is a reduced-complexity version of the CS-ACELP coder. It was designed explicitly for simultaneous voice and data applications that are prevalent in low-bit-rate multimedia communications. These two coders use the same bitstream format and can interoperate. The ITU Rec. G.723.1 6.3 and 5.3 kb/s speech coder for multimedia communications was designed originally for low-bit-rate videophones. Its frame size of 30 ms and one-way algorithmic codec delay of 37.5 ms allow for a further reduction in bit rate compared to the G.729 coder. In applications where low delay is important, the delay of G.723.1 may be too large. However, if the delay is acceptable, G.723.1 provides a lower-complexity alternative to G.729 at the expense of a slight degradation in quality. This article describes the attributes of speech coders such as bit rate, complexity, delay, and quality. Then it discusses the basic concepts of the three new ITU coders by comparing their specific attributes. The second part of this article describes the standardization process for each of these coders.

Journal ArticleDOI
TL;DR: A telemedicine prototype is presented, each of its components discussed, and a potential future teleMedicine system is shown.
Abstract: Telemedicine is much more than just teleconferencing. ISDN could be used in some low-end applications, but many telemedicine applications will require the higher bandwidth and guaranteed qualities of service supported by ATM. We discuss the design of multimedia systems for telemedicine. First, various applications of telemedicine are presented, and their multimedia and communications requirements are discussed. A telemedicine prototype is then presented, each of its components discussed, and a potential future telemedicine system is shown.

Journal ArticleDOI
TL;DR: With complicated line coding and other features such as integral forward error correction and ATM/Ethernet mode interfaces, ADSL will be the most complex modem ever attached to a telephone line but this will not prevent ADSL from reaching consumer-level pricing within the next two years.
Abstract: The Internet has surfaced as the dominant early market for residential broadband. ADSL, a transmission system capable of realizing rates from 1 to Mb/s over existing telephone lines, fits Internet access requirements perfectly, and offers telephone companies a tool for connecting virtually all Internet users at megabit rates before the next century. ADSL is asymmetric-high-speed downstream, lower-speed upstream-to counteract speed limitations imposed by line length and crosstalk. The transmission technology itself has two essential forms, single-carrier and multicarrier, which must press Shannon's limit to squeeze so many bits through so little bandwidth. With complicated line coding and other features such as integral forward error correction and ATM/Ethernet mode interfaces, ADSL will be the most complex modem ever attached to a telephone line. This will not prevent ADSL from reaching consumer-level pricing within the next two years. We can expect some commercial deployment in 1997 and virtually ubiquitous availability by the end of 1999.

Journal ArticleDOI
TL;DR: The issues involved in asynchronous video transfers are introduced and brief overviews of video coding, rate control, and multiplexing, as well as delay, error, and loss control are given.
Abstract: Video transfers across IP and ATM networks have received much research attention during the last ten years. Various video services are expected in the future, enabled by the rapid development in video coding and broadband network technology. This article gives an introduction to the issues involved in asynchronous video transfers. Brief overviews of video coding, rate control, and multiplexing, as well as delay, error, and loss control are also given.

Journal ArticleDOI
B.H. Fleury1, P.E. Leuthold1
TL;DR: A systematic description of the propagation and simulation models developed within various European projects is given and the main features of these models and the rationale behind their elaboration are focused on.
Abstract: Detailed knowledge of radio propagation effects is a keystone for the development and performance assessment of mobile communication systems. Although a lot of investigations have already been carried out, there remains a need to gain deeper insight into the complex mechanisms which govern radio propagation. The authors first present a summary of the propagation mechanisms and discuss some issues related to radio channel parameters and measurement techniques. Then a systematic description of the propagation and simulation models developed within various European projects is given. The survey focuses on the main features of these models and the rationale behind their elaboration.

Journal ArticleDOI
TL;DR: The rules that the sources have to follow to achieve a fair and efficient allocation of network resources are explained.
Abstract: The available bit rate (ABR) service has been developed to support data applications over asynchronous transfer mode (ATM) networks. The network continuously monitors its traffic and provides feedback to the source end systems. This article explains the rules that the sources have to follow to achieve a fair and efficient allocation of network resources.

Journal ArticleDOI
TL;DR: The authors describe a protocol that can adapt to the changing demands of a mix of synchronous transfer mode (STM) and asynchronousTransfer mode (ATM) applications and efficiently allocate bandwidth to a variety of bursty traffic sources and its performance with respect to throughput, latency, and bandwidth efficiency is examined.
Abstract: The authors describe a protocol that can adapt to the changing demands of a mix of synchronous transfer mode (STM) and asynchronous transfer mode (ATM) applications and efficiently allocate bandwidth to a variety of bursty traffic sources. In the case of a hybrid fiber-coaxial (HFC) network, the protocol resides in customer premises equipment (CPE) and a common head-end/central-office (HE/CO) controller. A medium-access control (MAC) processor provides for dividing the time domain for a given digital bitstream into successive frames, each with multiple STM and ATM time slots. Within the STM region of a frame, variable-length time slots are allocated to calls (e.g., telephony, video telephony) requiring different amounts of bandwidth. In the upstream channels, a contention access signaling time slot is also provided in the STM region for call control and setup requests. Within the ATM region, fixed-length time slots accommodate one individual ATM cell. These ATM time slots may be reserved for a user for either the duration of a call or a burst of successive ATM cells, or shared via a contention process. At least one contention time slot is available for signaling messages related to ATM call control and setup requests. The MAC-layer protocol, its relation to circuit- and ATM-amenable applications, and its performance with respect to throughput, latency, and bandwidth efficiency for several service scenarios are examined.

Journal ArticleDOI
TL;DR: The authors describe the purpose of the available bit rate (ABR) service in the context of other ATM services and review the agreements on the traffic control mechanism.
Abstract: The authors describe the purpose of the available bit rate (ABR) service in the context of other ATM services and review the agreements on the traffic control mechanism. They describe the recent progress towards standardization of the new service. The general nature of the ABR service is described in comparison with constant bit rate (CBR) and variable bit rate (VBR) services.

Journal ArticleDOI
M. Aoki1, H. Fujii
TL;DR: The authors present some experimental results from the implementation of a function integrating communication by infrared ray with a gap-measuring technique by the vision system, and several preliminary communication protocols are proposed.
Abstract: Mutual exchange of status data between vehicles in close proximity is the basis for safe vehicle operation. Application areas range from driver assistance/warning to fully autonomous driving. To enable this data exchange we need an intervehicle communication (IVC) system. Vehicles involved in mutual data exchange form a kind of local area network; however, the characteristics of this network are quite different from those of conventional networks. The configuration of this kind of network changes from time to time, in terms of organization, proximity group, group position, and relative position; therefore, it is very challenging to establish. The authors have been working on this problem from the point of view of communication media and protocol. The characteristics and requirements of IVC are discussed, and several preliminary communication protocols are proposed. The authors also present some experimental results from the implementation of a function integrating communication by infrared ray with a gap-measuring technique by the vision system.

Journal ArticleDOI
TL;DR: An overview of the role of an internet protocol, the motivation for developing a new version of the IP, and some of the details of the next generation of IP are examined.
Abstract: The current version of the Internet protocol (IP) is becoming obsolete because of its limited address space, lack of needed functionality and inadequate security features. The next generation of IP, called IPv6, has now been standardized and will carry TCP/IP networks and applications well into the next century. This article begins with an overview of the role of an internet protocol, looks at the motivation for developing a new version of the IP, and then examines some of its details.

Journal ArticleDOI
TL;DR: The standard should ensure interoperability among a diverse variety of H.324 terminals, including PC-based multimedia videoconferencing systems, voice/data modems, encrypted telephones, World Wide Web browsers with live video, and standalone videophones.
Abstract: ITU-T H.324 is the new international standard for multimedia communication on low-bit-rate circuit-switched networks, including ordinary analog telephone lines. It supplies any combination of real-time video, audio, and data. H.324 was designed, above all, to provide the best possible performance (video and audio quality, delay, etc.) on low-bit-rate networks. This article covers the H.324 system and its component standards, including the V.34 modem, H.223 multiplexer, H.245 control protocol, G.723.1 audio coder, and H.263 video coder. Call setup procedures and optional features like encryption and data application protocols are also described. The standard should ensure interoperability among a diverse variety of H.324 terminals, including PC-based multimedia videoconferencing systems, voice/data modems, encrypted telephones, World Wide Web browsers with live video. Remote security cameras. and standalone videophones. Products compliant with H.324 should all interoperate with each other and, through appropriate gateways, with ITU-T H-series terminals on ISDN, LANs, and ATM/B-ISDN networks.

Journal ArticleDOI
TL;DR: This work introduces a very versatile MAC protocol for the HFC 802.14 network, MLAP, which can provide integrated broadband services to the home, internetwork easily with ATM wide area networks, support QoS constraints for various types of traffic, and operate over a variety of physical layer protocols.
Abstract: Interactive residential broadband/multimedia services are expected to be the next main event in the cyberspace experience. The large excess bandwidth (well over 300 MHz) available in today's cable TV (CATV) hybrid fiber/coaxial (HFC) plants is an ideal candidate to provide the underlying communications infrastructure for interactive digital services to the home; cable operators that have not yet upgraded their all-coaxial plants to HFC are quickly moving in this direction. MLAP is a flexible ATM-friendly MAC protocol that is capable of supporting various types of traffic with diverse quality-of-service requirements. We introduce a very versatile MAC protocol for the HFC 802.14 network. MLAP can provide integrated broadband services to the home, internetwork easily with ATM wide area networks, support QoS constraints for various types of traffic, and operate over a variety of physical layer protocols. Our presentation is only an extended summary of our medium-sharing protocol proposal to the IEEE 802.14 WG. We consider only error-free system operation. MLAP provides for the use of timers for the recovery of error situations in the network. MLAP is also supported by a management suite of protocols for management of the overall system.

Journal ArticleDOI
TL;DR: This new high-speed modem enables various new multimedia modem applications that allow full-duplex transmission at rates up to 33.6 kb/s in the ordinary general switched telephone network (GSTN).
Abstract: The development of the V.34 modem standard permits full-duplex transmission at rates up to 33.6 kb/s in the ordinary general switched telephone network (GSTN). This article briefly describes the technologies that are used to make these dramatically increased bit rates possible. This new high-speed modem enables various new multimedia modem applications.

Journal ArticleDOI
TL;DR: The requirements for third-generation cellular mobile radio systems such as Universal Mobile Telecommunications System (UMTS) and Future Public Land Mobile Telecommunications system (FPLMTS), which has been named International Mobile Telecommunications after the year 2000 (IMT-2000) are presented concisely.
Abstract: In Europe, the challenge of the design of third-generation cellular mobile radio systems has been taken numerous research and development activities in this field have been started. The authors try to give an overview of the European activities in this field. The article is organized in two parts. In the first part, the requirements for third-generation cellular mobile radio systems such as Universal Mobile Telecommunications System (UMTS) and Future Public Land Mobile Telecommunications System (FPLMTS), which has been named International Mobile Telecommunications after the year 2000 (IMT-2000) are presented concisely. Also, the importance and challenge of the multiple access design for such third-generation cellular mobile radio systems is explained. In the second part, numerous European research activities with focus on the multiple access design for third-generation cellular mobile radio systems are reviewed.

Journal ArticleDOI
TL;DR: VICS distributes road traffic information such as traffic jams or accidents to drivers in real time, and stimulates drivers for accurate and proper utilization.
Abstract: The objective of a vehicle information and communication system (VICS) is to disperse traffic by providing drivers with road traffic information to enable them to satisfy their natural desire to "get there faster". Put simply, VICS is based on drivers' arbitrary selection of routes and on the automobile's unique ability to take any desired route. The objective is to promote the safe, smooth flow of traffic by naturally distributing the flow of traffic, which is done by guiding cars to the appropriate routes in accordance with drivers' instinctive desire to reach their destinations quickly by avoiding traffic congestion. VICS distributes road traffic information such as traffic jams or accidents to drivers in real time, and stimulates drivers for accurate and proper utilization.

Journal ArticleDOI
Patrick R. Trischitta1, M. Colas, M. Green, G. Wuzniak, J. Arena 
TL;DR: The TAT-12/13 Cable Network will provide a 10 Gb/s capacity between the United States, the United Kingdom, and France by using ring switching equipment, which is fully restorable within the network without dropping calls in the process.
Abstract: The TAT-12/13 Cable Network will provide a 10 Gb/s capacity between the United States, the United Kingdom, and France. By using ring switching equipment, this capacity is fully restorable within the network without dropping calls in the process. The undersea repeaters in this network use optical amplifier technology to transport a single 5 Gb/s optical signal on each fiber pair. With the upgrade potential already demonstrated, TAT-12/13's transport capacity may at least double before the end of its 25-year design life.

Journal ArticleDOI
TL;DR: This article discusses generic switching functions in telecommunications networks with a view of the possible role of photonics, and discusses the implementation of the switching functions from a photonics and electronics point of view, and applies this reasoning to look at scaling and transparency of all-optical networks based on current research.
Abstract: The continued rapid progress in the deployment of fiber optics communications has led to widespread interest in employing photonics to implement switching functions, hitherto reserved for electronics. Significant research effort has been devoted to this, and different specialized concepts have been suggested and partly demonstrated, albeit not in the field. At the same time, mainstream research and development in the area of telecommunications switching is solidly based on electronics. In this article we first give a short introduction to photonic switching. We then discuss generic switching functions in telecommunications networks with a view of the possible role of photonics, and discuss the implementation of the switching functions from a photonics and electronics point of view. We then apply this reasoning to look at scaling and transparency of all-optical networks based on our current research.

Journal ArticleDOI
V.K. Garg1, E.L. Sneed1
TL;DR: Capacities of a WLL system based on the IS-54 (now IS-136) TDMA, IS-95A CDMA, and ETSI GSM technologies are developed and compared.
Abstract: The digital access technologies for the wireless local loop (WLL) or fixed wireless system are discussed. WLL is an important means of providing telephone services more cheaply and quickly in the developing countries than through a wireline system. Capacities of a WLL system based on the IS-54 (now IS-136) TDMA, IS-95A CDMA, and ETSI GSM technologies are developed and compared.

Journal ArticleDOI
TL;DR: An introductory overview of the different functions covered by the DSM-CC standard is given and the basic reference model that underpinned the development of the standard is conveyed.
Abstract: Digital storage media-command and control (DSM-CC) is a very recent ISO/IEC standard developed for the delivery of multimedia broadband services. Open protocols in this area are essential for the widespread deployment of such services. Total interoperability between service providers and consumers will require many different aspects of broadband service delivery to be addressed. This article gives an introductory overview of the different functions covered by the DSM-CC standard. Its purpose is to convey the scope of the DSM-CC standard and the basic reference model that underpinned the development of the standard.

Journal ArticleDOI
TL;DR: The ACTS (Advanced Communications Technologies and Services) program will offer, in the period 1995-1998, service providers, communications operators, and equipment manufacturers greater opportunities to master and trial mobile and personal communications services and technologies.
Abstract: Vast importance is being placed in Europe on the development of third-generation mobile telecommunications systems, since it is expected that mobile and personal communications will become a key driver for growth and innovation in the next millenium as well as being a necessary building block of the wireless information society. Significant progress has been made since 1988 by a number of European Union funded R&D projects working toward the development of future generations of mobile communication concepts, systems, and networks. The ACTS (Advanced Communications Technologies and Services) program will offer, in the period 1995-1998, service providers, communications operators, and equipment manufacturers greater opportunities to master and trial mobile and personal communications services and technologies. From the user's perspective the ACTS program will strive to ensure that current mobile services are extended to include multimedia and broadband services, that access to services are made without regard to the underlying networks, and that convenient, lightweight, compact, and power-efficient terminals adapt automatically to whatever air-interface parameters are appropriate to the user's location and desired services.