Showing papers in "IEEE Communications Magazine in 1998"
TL;DR: The applications of location technology, the methods available for its implementation inCDMA networks, and the problems that are encountered when using CDMA networks for positioning are discussed.
Abstract: Applications for the location of subscribers of wireless services continue to expand. Consequently, location techniques for wireless technologies are being investigated. With code-division multiple access (CDMA) being deployed by a variety of cellular and PCS providers, developing an approach for location in CDMA networks is imperative. This article discusses the applications of location technology, the methods available for its implementation in CDMA networks, and the problems that are encountered when using CDMA networks for positioning.
868 citations
TL;DR: In this article, a wideband wireless access based on direct sequence code division multiple access aimed at third-generation mobile communications systems is reviewed, and the radio link performance evaluated by computer simulation is also presented.
Abstract: Wideband wireless access based on direct sequence code division multiple access aimed at third-generation mobile communications systems is reviewed. W-CDMA is designed to flexibly offer wideband services which cannot be provided by present cellular systems, with various data rates as high as 2 Mb/s. The important concept of W-CDMA is the introduction of intercell asynchronous operation and the pilot channel associated with individual data channels. Intercell asynchronous operation facilitates continuous system deployment from outdoors to indoors. Other technical features of W-CDMA include fast cell search under intercell asynchronous operation, fast transmit power control, coherent spreading code tracking, a coherent RAKE receiver, orthogonal multispreading factor forward link, and variable-rate transmission with blind rate detection. The introduction of the data-channel-associated pilot channel allows W-CDMA to support interference cancellation and adaptive antenna array techniques that can significantly increase the link capacity and coverage. This article presents the radio link performance evaluated by computer simulation. Field experiment radio link performance results are also presented.
846 citations
TL;DR: This article presents an overview of the spreading techniques for use in direct sequence CDMA cellular networks, and describes different methods of multiple spreading for channelization and scrambling in CDMA and W-CDMA realizations.
Abstract: This article presents an overview of the spreading techniques for use in direct sequence CDMA cellular networks. We review the theoretical background for sequences used in CDMA and wideband CDMA, and discuss the main characteristics of the maximal length, Gold (1967, 1968), and Kasami sequences, as well as variable- and fixed-length orthogonal codes. We also describe different methods of multiple spreading for channelization and scrambling in CDMA and W-CDMA realizations.
642 citations
TL;DR: The authors examine the ability to derive position information from GSM signals, based on their May 1996 achievement of accurate position measurements using GSM, to examine positioning solutions for the GSM group of standards.
Abstract: Due to the FCC requirement that operators of mobile communications networks be able to accurately locate mobile callers requesting emergency assistance via 911 by the year 2001, there has been a lot of activity among cellular and PCS providers to examine cellular positioning options. This article examines positioning solutions for the GSM group of standards. Worldwide deployment of GSM systems is well underway, and the positioning characteristics of the various systems are similar. The authors examine the ability to derive position information from GSM signals, based on their May 1996 achievement of accurate position measurements using GSM. Features of GSM signals relevant to positioning are analyzed as well as results achieved and the authors' ongoing positioning trials. Finally, other issues related to GSM positioning and mobile phone positioning in general are covered.
581 citations
TL;DR: UTRA based on W-CDMA can now be regarded as a mature technology, ready to provide the basis for UMTS/IMT-2000, and has flexible support of mixed services, variable-rate services, and an efficient packet mode.
Abstract: The UMTS terrestrial radio access is based on wideband 4.096 Mchip/s DS-CDMA technology. UTRA will be connected to an evolved GSM core network for both circuit and packet services. A merger between ETSI/Europe and ARIB/Japan based on W-CDMA, a GSM core network, and a common frequency allocation according to the ITU Recommendation of 2 GHz makes a global IMT-2000 standard feasible. UTRA based on W-CDMA fully supports the UMTS/IMT-2000 requirements (e.g., support of 384 kb/s for wide-area coverage and 2 Mb/s for local coverage). Furthermore, the air interface has flexible support of mixed services, variable-rate services, and an efficient packet mode. Key W-CDMA features also include improved basic capacity/coverage performance compared to second-generation systems, full support of adaptive antenna arrays, support of hierarchical cell structures with interfrequency handover, and support of asynchronous inter-base-station operation. There have been no constraints due to the strong requirements for backward compatibility with second-generation systems. This has facilitated a high degree of flexibility and a future-proof air interface. Extensive evaluations by means of simulations and field trials have been carried out by a number of companies, and full system tests are ongoing. Consequently, W-CDMA technology can now be regarded as a mature technology, ready to provide the basis for UMTS/IMT-2000.
579 citations
TL;DR: The core concepts of this emerging paradigm are introduced, an account of current research efforts in the context of telecommunications is presented, and a descriptive look at some of the forerunners that are providing experimental technologies supporting this paradigm is presented.
Abstract: The anticipated increase in popular use of the Internet will create more opportunities in distance learning, electronic commerce, and multimedia communication, but it will also create more challenges in organizing information and facilitating its efficient retrieval. From the network perspective, there will be additional challenges and problems in meeting bandwidth requirements and network management. Many researchers believed that the mobile agent paradigm (mobile object) could propose several attractive solutions to deal with such challenges and problems. A number of mobile agent systems have been designed and implemented in academic institutions and commercial firms. However, few applications were found to take advantage of the mobile agent. Among the hurdles facing this emerging paradigm are concerns about security requirements and efficient resource management. This article introduces the core concepts of this emerging paradigm, and presents an account of current research efforts in the context of telecommunications. The goal is to provide the interested reader with a clear background of the opportunities and challenges this emerging paradigm brings about, and a descriptive look at some of the forerunners that are providing experimental technologies supporting this paradigm.
500 citations
TL;DR: This article surveys the risks connected with the use of mobile agents, and security techniques available to protect mobile agents and their hosts, and identifies the inadequacies of the security techniques developed from the information fortress model.
Abstract: The practicality of mobile agents hinges on realistic security techniques. Mobile agent systems are combination client/servers that transport, and provide an interface with host computers for, mobile agents. Transport of mobile agents takes place between mobile agent systems, which are located on heterogeneous platforms, making up an infrastructure that has the potential to scale to the size of any underlying network. Mobile agents can be rapidly deployed, and can respond to each other and their environment. These abilities expose flaws in current security technology. This article surveys the risks connected with the use of mobile agents, and security techniques available to protect mobile agents and their hosts. The inadequacies of the security techniques developed from the information fortress model are identified. They are the result of using a good model in an inappropriate context (i.e. a closed system model in a globally distributed networking computing base). Problems with commercially available techniques include: (1) conflicts between security techniques protecting hosts and mobile agents, (2) inability to handle multiple collaborative mobile agents, and (3) emphasis on the credentials of software instead of on the integrity of software to determine the level of trust.
419 citations
TL;DR: The unique challenges and some of the proposed approaches for each of the major wireless standards for E-911 service are reviewed.
Abstract: When the FCC created the rules for wireless Enhanced 911 (E-911) service, a flurry of research and development activities dedicated to locating the position of emergency callers followed. The current deadline for this capability is October 1, 2001. We review the unique challenges and some of the proposed approaches for each of the major wireless standards.
408 citations
TL;DR: This article concentrates on the terrestrial transmission system DVB-T as one example of the many transmission technologies DVB has developed over the last few years and explains some of the fundamental concepts behind the work of this group.
Abstract: A new kind of "wireless video" is currently entering consumers' homes-digital television. The term digital video broadcasting (DVB) is used as a synonym for digital television in many countries of the world. Whereas one may tend to think that digital television means just a new, digital, form of signal representation not necessarily affecting the information content of what one has always called TV, the truth is that digital television becomes multiple-channel data broadcasting. This article reviews some of the results of the work in the worldwide DVB Project and explains some of the fundamental concepts behind the work of this group. It then concentrates on the terrestrial transmission system (DVB-T) as one example of the many transmission technologies DVB has developed over the last few years. The COFDM modulation scheme which is a key ingredient of DVB-T is described in some detail. The performance of the system is presented. The use of DVB for data broadcasting and the accompanying return channel technologies are explained.
390 citations
TL;DR: An overview of worldwide research and standardization activities related to the multiple access schemes for third-generation mobile communications systems IMT-2000 and UMTS is given.
Abstract: The basis for any air interface design is how the common transmission medium is shared between users (i.e., multiple access scheme). The underlying multiple access method for all mobile radio systems is FDMA. The performance of TDMA and CDMA has been subject to vigorous debate, without any definitive conclusions. This article gives an overview of worldwide research and standardization activities related to the multiple access schemes for third-generation mobile communications systems IMT-2000 and UMTS.
388 citations
TL;DR: In this paper, error resilience aspects of the video coding techniques that are standardized in the ISO MPEC-4 standard are described, including resynchronization strategies, data partitioning, reversible variable length codes (VLCs), and header extension codes.
Abstract: This article describes error resilience aspects of the video coding techniques that are standardized in the ISO MPEC-4 standard. It begins with a description of the general problems in robust wireless video transmission. The specific tools adopted into the ISO MPEG-4 standard to enable the communication of compressed video data over noisy wireless channels are presented in detail. These techniques include resynchronization strategies, data partitioning, reversible variable length codes (VLCs), and header extension codes. An overview of the evolving ISO MPEG-4 standard and its current status are described.
TL;DR: A broad review of the optical wireless field is presented, from early experiments through to today's high-performance systems, with emphasis on understanding the benefits and limitations of optical wireless.
Abstract: We present a broad review of the optical wireless field, from early experiments through to today's high-performance systems. Emphasis is placed on understanding the benefits and limitations of optical wireless, all of which ultimately define the applications. A variety of systems are examined, each incorporating a different technological solution to suit the particular application.
TL;DR: An extensive overview of the different technologies used to produce tunable optical filters is presented and it is shown that fiber filters are the most commercialized, yet inherently limited in their dynamic speeds.
Abstract: WDM is currently taking over as the leading technology in point-to-point transmission links. For optical implementation of WDM networks, logical functionalities such as wavelength (channel) selection should be carried out in the wavelength domain; thus, the development of dynamic optical devices is required. One key device is a tunable optical filter. Important features of such a filter include low insertion loss, narrow bandwidth, high sidelobe suppression, large dynamic range, fast tuning speed, a simple control mechanism, small size, and cost effectiveness. Here, an extensive overview of the different technologies used to produce tunable optical filters is presented. Among them, fiber filters such as fiber Bragg gratings and fiber Fabry Perot are the most commercialized, yet inherently limited in their dynamic speeds. For high demanding dynamics, micro-machined and acousto-optic filters can offer a good solution for microsecond tuning speeds. Faster tunable devices, in nanosecond tuning speeds, might emerge out of microresonators, electrooptic filters, and active DBR filters.
TL;DR: The architecture emphasizes decentralized control of measurements; strong authentication and security; mechanisms for both maintaining tight administrative control over who can perform what measurements using which platforms, and delegation of some forms of measurement as a site's measurement policy permits.
Abstract: Historically, the Internet has been woefully under-measured and under-instrumented. The problem is only getting worse with the network's ever-increasing size. We discuss the goals and requirements for building a "measurement infrastructure" for the Internet, in which a collection of measurement "platforms" cooperatively measure the properties of Internet paths and clouds by exchanging test traffic among themselves. The key emphasis of the architecture, which forms the underpinnings of the National Internet Measurement Infrastructure (NIMI) project, is on tackling problems related to scale. Consequently, the architecture emphasizes decentralized control of measurements; strong authentication and security; mechanisms for both maintaining tight administrative control over who can perform what measurements using which platforms, and delegation of some forms of measurement as a site's measurement policy permits; and simple configuration and maintenance of platforms.
TL;DR: R router architectures that can support the two trends of rising bandwidth demand and rising demand for differentiated services are described and it is argued that it is technologically possible to considerably raise the level of differentiated services which service providers can offer their customers.
Abstract: With the transformation of the Internet into a commercial infrastructure, the ability to provide differentiated services to users with widely varying requirements is rapidly becoming as important as meeting the massive increases in bandwidth demand. Hence, while deploying routers, switches, and transmission systems of ever increasing capacity, Internet service providers would also like to provide customer-specific differentiated services using the same shared network infrastructure. We describe router architectures that can support the two trends of rising bandwidth demand and rising demand for differentiated services. We focus on router mechanisms that can support differentiated services at a level not contemplated in proposals currently under consideration due to concern regarding their implementability at high speeds. We consider the types of differentiated services that service providers may want to offer and then discuss the mechanisms needed in routers to support them. We describe plausible implementations of these mechanisms (the scalability and performance of which have been demonstrated by implementation in a prototype system) and argue that it is technologically possible to considerably raise the level of differentiated services which service providers can offer their customers, and that it is not necessary to restrict differentiated services to rudimentary offerings even in very-high-speed networks.
TL;DR: The authors outline the design issues facing the next generation of backbone, enterprise, and access routers, and present a survey of advances in router design, identifying important trends, concluding with a selection of open issues.
Abstract: Future routers must not only forward packets at high speeds, but also deal with nontrivial issues such as scheduling support for differential services, heterogeneous link technologies, and backward compatibility with a wide range of packet formats and routing protocols. The authors outline the design issues facing the next generation of backbone, enterprise, and access routers. The authors also present a survey of advances in router design, identifying important trends, concluding with a selection of open issues.
TL;DR: A model and nomenclature for talking about active networks are introduced, some possible approaches in terms of that nomenClature are described, and various aspects of the architecture being developed in the DARPA-funded active networks program are presented.
Abstract: Active networks represent a significant step in the evolution of packet-switched networks, from traditional packet-forwarding engines to more general functionality supporting dynamic control and modification of network behavior. However, the phrase "active network" means different things to different people. This article introduces a model and nomenclature for talking about active networks, describes some possible approaches in terms of that nomenclature, and presents various aspects of the architecture being developed in the DARPA-funded active networks program. Potential applications of active networks are highlighted, along with some of the challenges that must be overcome to make them a reality.
TL;DR: The cdma2000 system includes a greatly enhanced air interface supporting CDMA over wider bandwidths for improved capacity and higher data rates while also maintaining backward compatibility with existing IS-95 CDMA end-user devices.
Abstract: Existing IS-95-based CDMA systems support circuit-mode and packet-mode data services at a data rate limited to 9.6-14.4 kb/s. Fueled by the explosive growth of the Internet, applications and market opportunities are demanding that higher capacity, higher data rates, and advanced multimedia services be supported in the near future. The evolution of the IS-95 CDMA standard to higher data rates and more advanced services occurs in two steps. The first step, IS-95-B, is an enhancement to the IS-95-A standard and offers the highest possible performance without breaking current IS-95-A air interface design characteristics, thereby maintaining strict compatibility with existing base station hardware. The proposed standard will support a high data rate (64 kb/s) in both directions, to and from the mobile device. A new burst mode packet data service is defined to allow better interference management and capacity utilization. The second evolution step, cdma2000, provides next-generation capacity, data rates, and services. The cdma2000 system includes a greatly enhanced air interface supporting CDMA over wider bandwidths for improved capacity and higher data rates while also maintaining backward compatibility with existing IS-95 CDMA end-user devices. The cdma2000 system also includes a sophisticated MAC feature to effectively support very-high-data-rate services (up to 2 Mb/s) and multiple concurrent data and voice services. This article describes the design and performance of the high-data-rate service provided by second- and third-generation CDMA systems.
TL;DR: A framework for statistical modeling of the wideband characteristics of the frequency-selective fading multipath indoor radio channel for geolocation applications and the effects of external walls on estimating the location of the DLOS path are presented.
Abstract: A framework for statistical modeling of the wideband characteristics of the frequency-selective fading multipath indoor radio channel for geolocation applications is presented. Multipath characteristics of the channel are divided into three classes according to availability and the strength of the direct line of sight (DLOS) path with respect to the other paths. Statistics of the error in estimating the time of arrival of the DLOS path in a building is related to the receiver's sensitivity and dynamic range. The effects of external walls on estimating the location of the DLOS path are analyzed.
TL;DR: A taxonomy to classify the surveyed protocols according to several distinct features is presented, the rationale behind the protocol's design decisions are discussed, and some current research-issues in multicast protocol design are presented.
Abstract: Network support for multicast has triggered the development of group communication applications such as multipoint data dissemination and multiparty conferencing tools. To support these applications, several multicast transport protocols have been proposed and implemented. Multicast transport protocols have been an area of active research for the past couple of years. This article summarizes the activities in this work-in-progress area by surveying several multicast transport protocols. It also presents a taxonomy to classify the surveyed protocols according to several distinct features, discusses the rationale behind the protocol's design decisions, and presents some current research-issues in multicast protocol design.
TL;DR: Multiprotocol label switching (MPLS) as mentioned in this paper is an Internet Engineering Task Force (IETF) standard intended to enhance the speed, scalability, and service provisioning capabilities in the Internet.
Abstract: Multiprotocol label switching (MPLS) is rapidly emerging as an Internet Engineering Task Force (IETF) standard intended to enhance the speed, scalability, and service provisioning capabilities in the Internet. MPLS uses the technique of packet forwarding based on labels, to enable the implementation of a simpler high-performance packet forwarding engine. This also decouples packet forwarding from routing, facilitating the provision of varied routing services independent of the packet forwarding paradigm. The authors track the evolution of this technology in relation to other existing technologies. Then an overview of the MPLS architecture and design is provided. In addition, some of the work that was a precursor to MPLS is discussed, as well as related issues and debates.
TL;DR: Two modifications to the design of wireless infrared links are discussed that can yield significant performance improvements, albeit at the price of increased complexity, and may enable infrared wireless networks to employ space-division multiplexing.
Abstract: We discuss two modifications to the design of wireless infrared links that can yield significant performance improvements, albeit at the price of increased complexity. In line-of-sight and non-line-of-sight links, replacement of a single-element receiver by one employing an imaging light concentrator and a segmented photodetector can reduce received ambient light noise and multipath distortion. For a fixed receiver entrance area, such an imaging receiver can reduce transmit power requirements by as much as about 14 dB, depending on the link design and the number of photodetector segments. Imaging receivers also reduce co-channel interference, and may therefore enable infrared wireless networks to employ space-division multiplexing, wherein several transmitters located in close proximity can transmit simultaneously at the same wavelength. In nondirected non-line-of-sight links, replacement of the diffuse transmitter by one that projects multiple narrow beams can reduce the path loss, further reducing the transmit power requirement by several decibels. We describe the design of an experimental 100 Mb/s infrared wireless link employing a multibeam transmitter and a 37-pixel imaging receiver.
TL;DR: It is shown that for a given number of bits per symbol, DPIM has a higher transmission capacity, a similar spectral profile, and only a marginally inferior error probability performance compared with pulse position modulation, and is rather less complex to implement.
Abstract: This article presents a study of digital pulse interval modulation (DPIM) for optical wireless communications using intensity modulation with direct detection. The DPIM code properties are discussed, and expressions for the transmission capacity, power spectrum, and error probability are presented. We show that for a given number of bits per symbol, DPIM has a higher transmission capacity, a similar spectral profile, and only a marginally inferior error probability performance compared with pulse position modulation, and is rather less complex to implement. Finally, problems associated with the nonuniform symbol length characteristics of DPIM together with possible solutions are discussed.
TL;DR: A scalable location service based on a worldwide distributed search tree that adapts dynamically to an object's migration pattern to optimize lookups and updates is presented.
Abstract: Locating mobile objects in a worldwide system requires a scalable location service. An object can be a telephone or a notebook computer, but also a software or data object, such as a file or an electronic document. Our service strictly separates an object's name from the addresses where it can be contacted. This is done by introducing a location-independent object handle. An object's name is bound to its unique object handle, which, in turn, is mapped to the addresses where the object can be contacted. To locate an object, we need only its object handle. We present a scalable location service based on a worldwide distributed search tree that adapts dynamically to an object's migration pattern to optimize lookups and updates.
TL;DR: The objective is to enable the development of open signaling, control, and management applications as well as higher-level multimedia services on networks through programming interfaces, including ATM switches, circuit switches, IP routers, and hybrid switches.
Abstract: This article discusses the need for standard software interfaces for programming of networks, specifically for service and signaling control, through programming interfaces. The objective is to enable the development of open signaling, control, and management applications as well as higher-level multimedia services on networks. The scope of this effort includes ATM switches, circuit switches, IP routers, and hybrid switches such as those that provide for fast switching of IP packets over an ATM backbone. The basic ideas represented herein are in the process of development as a standard for application programming interfaces for networks under IEEE Standards Project IEEE P1520.
TL;DR: The conclusion that integrated networks of the future should be able to provide better and better service with efficiency tending toward perfection is a rather happy conclusion which thoroughly confirms the current rapid drive toward an all-encompassing integrated multiservice network.
Abstract: A much clearer picture of the progress toward an integrated high-speed multiservice network is now emerging. Such networks were anticipated over 20 years ago, at a time when packet switching was just another way to transmit data. Now the technology is so mature that media barons are organizing their investments in order to take advantage of its profitability. Many of the technical problems are now solved, and the fundamental protocols required for these networks are sufficiently well-defined to support a rapidly expanding industry. However, consensus on how to talk about the statistics of the data transmitted around these networks has not been readily forthcoming. Nevertheless, there now exists a family of models with sufficient richness to describe real traffic fairly well, which can be parameterized conveniently, and which degenerates to a readily analyzable Gaussian model in the situation of very large networks. This analysis leads to important architectural conclusions which accord with common sense, in particular the conclusion that integrated networks of the future should be able to provide better and better service with efficiency tending toward perfection. This is a rather happy conclusion which thoroughly confirms the current rapid drive toward an all-encompassing integrated multiservice network. Rather than the increase in traffic and diversity of service types leading to greater and greater complexity, it seems that the flow of traffic in our networks may become steadily more manageable.
TL;DR: With delegated agents, management intelligence can be dynamically embedded in elements and domains so that networked systems can be programmed to be self-managed.
Abstract: Current network management depends on centralized monitoring, analysis, and control by operations staff who must manipulate detailed and often obscure element instrumentation. This complex and labor-intensive management paradigm has been stretched to its limits by the scale and complexity of emerging networks. This article describes the use of delegated agents to distribute and automate management functions. With delegated agents, management intelligence can be dynamically embedded in elements and domains so that networked systems can be programmed to be self-managed.
TL;DR: A survey of the three versions of SNMP is provided, including a discussion of the way in which management information is represented and the protocol functionality.
Abstract: The Simple Network Management Protocol is the most widely used protocol for the management of IP-based networks and internets. The original version, now known as SNMPv1, is widely deployed. SNMPv2 adds functionality to the original version but does not address its security limitations; this relatively recent standard has not achieved much acceptance. An effort is currently underway to develop SNMPv3, which will retain the functional enhancements of SNMPv2 and add powerful privacy and authentication features. This article provides a survey of the three versions of SNMP, including a discussion of the way in which management information is represented and the protocol functionality.
TL;DR: The key issues are illustrated with a system originally developed for locating elderly patients with Alzheimer's disease, and the desire to leverage the E911 location network to provide universal non-cellular location-based services.
Abstract: This article reviews the issues associated with the development of an E911 location network in light of the desire to leverage the E911 location network to provide universal non-cellular location-based services. The key issues are illustrated with a system originally developed for locating elderly patients with Alzheimer's disease.
TL;DR: In this paper, the increasing use of WDM systems in telecommunications networks is highlighted, and the potential role for wavelength conversion in future upgrades of such systems is reviewed, and experimental results obtained at BT Laboratories are used to illustrate the state of the art.
Abstract: In this article the increasing use of WDM systems in telecommunications networks is highlighted, and the potential role for wavelength conversion in future upgrades of such systems is reviewed. Techniques for achieving wavelength conversion by all-optical means using nonlinearities in semiconductor optical amplifiers are explained, and experimental results obtained at BT Laboratories are used to illustrate the state of the art.