Showing papers in "IEEE Communications Magazine in 1997"
TL;DR: The authors present an overview of new multiple access schemes based on a combination of code division and multicarrier techniques, such as multicarrier code-division multiple access (MC-CDMA), multicarriers direct sequence CDMA, and multitone CDMA.
Abstract: The authors present an overview of new multiple access schemes based on a combination of code division and multicarrier techniques, such as multicarrier code-division multiple access (MC-CDMA), multicarrier direct sequence CDMA (multicarrier DS-CDMA), and multitone CDMA (MT-CDMA).
2,137 citations
TL;DR: It is illustrated how the routers of an IP network could be augmented to perform such customized processing on the datagrams flowing through them, and these active routers could also interoperate with legacy routers, which transparently forwarddatagrams in the traditional manner.
Abstract: Active networks are a novel approach to network architecture in which the switches (or routers) of the network perform customized computations on the messages flowing through them. This approach is motivated by both lead user applications, which perform user-driven computation at nodes within the network today, and the emergence of mobile code technologies that make dynamic network service innovation attainable. The authors discuss two approaches to the realization of active networks and provide a snapshot of the current research issues and activities. They illustrate how the routers of an IP network could be augmented to perform such customized processing on the datagrams flowing through them. These active routers could also interoperate with legacy routers, which transparently forward datagrams in the traditional manner.
1,489 citations
TL;DR: The performance investigation reveals that an IEEE 802.11 network may be able to carry traffic with time-bounded requirements using the point coordination function, however, the findings suggest that packetized voice traffic must be handled in conjunction with an echo canceler.
Abstract: The draft IEEE 802.11 wireless local area network (WLAN) specification is approaching completion. In this article, the IEEE 802.11 protocol is explained, with particular emphasis on the medium access control sublayer. Performance results are provided for packetized data and a combination of packetized data and voice over the WLAN. Our performance investigation reveals that an IEEE 802.11 network may be able to carry traffic with time-bounded requirements using the point coordination function. However, our findings suggest that packetized voice traffic must be handled in conjunction with an echo canceler.
1,080 citations
TL;DR: This article discusses how graph-based models can be used to represent the topology of large networks, particularly aspects of locality and hierarchy present in the Internet.
Abstract: The topology of a network, or a group of networks such as the Internet, has a strong bearing on many management and performance issues. Good models of the topological structure of a network are essential for developing and analyzing internetworking technology. This article discusses how graph-based models can be used to represent the topology of large networks, particularly aspects of locality and hierarchy present in the Internet. Two implementations that generate networks whose topology resembles that of typical internetworks are described, together with publicly available source code.
968 citations
TL;DR: In this article, the authors address Rayleigh fading, primarily in the UHF band, that affects mobile systems such as cellular and personal communication systems (PCS) and itemizes the fundamental fading mani.
Abstract: The paper addresses Rayleigh fading, primarily in the UHF band, that affects mobile systems such as cellular and personal communication systems (PCS) The paper itemizes the fundamental fading mani
953 citations
TL;DR: An overview of the Object Management Architecture is provided, in detail the CORBA component of that architecture is described, and a description of the OMG organization is described along with some of its current and future work.
Abstract: Large computer networks such as corporate intranets and the Internet are inherently heterogeneous due to such factors as increasingly rapid technological change, engineering trade-offs, accumulation of legacy systems over time, and varying system costs. Unfortunately, such heterogeneity makes the development and maintenance of applications that make the best use of such networks difficult. The Common Object Request Broker Architecture specification created by the Object Management Group provides a stable model for distributed object-oriented systems that helps developers cope with heterogeneity and inevitable change. Applications written to the CORBA standard are abstracted away from underlying networking protocols and transports, instead relying on object request brokers to provide a fast and flexible communication and object activation substrated. The abstractions provided by CORBA ORBs are currently serving as the basis for applications in a wide variety of problem domains, including telecommunications, finance, medicine, and manufacturing, running on platforms ranging from mainframes down to test and measurement equipment. This article first provides an overview of the Object Management Architecture, then describes in detail the CORBA component of that architecture, and concludes with a description of the OMG organization along with some of its current and future work.
840 citations
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TL;DR: The basic protocol is described, with details given on the three major component protocols: agent advertisement, registration, and tunneling, and the current problems facing mobile IP are discussed.
Abstract: Mobile IP has been designed within the Internet Engineering Task Force (IETF) to serve the needs of the burgeoning population of mobile computer users who wish to connect to the Internet and maintain communications as they move from place to place. The basic protocol is described, with details given on the three major component protocols: agent advertisement, registration, and tunneling. Then route optimization procedures are outlined, and further topics of current interest are described. The available tunneling mechanisms are shown, which the home agent uses to forward datagrams from the home network to the mobile computer. Having covered the details of the base mobile IP specification, we then describe further protocol messages which help to decrease the inefficiency associated with inserting the home agent in the routing path of data destined for mobile computers. Finally, we summarize and discuss the current problems facing mobile IP, as well as a few areas of active protocol development.
745 citations
TL;DR: In this article, Rayleigh fading in the UHF band has been studied and the fundamental fading manifestations and types of degradation are discussed, and the early models are still useful to help characterize fading effects in mobile digital communication systems.
Abstract: When the mechanisms of fading channels were first modeled in the 1950s and 1960s, the ideas were primarily applied to over-the-horizon communications covering a wide range of frequency bands. The 3-30 MHz high-frequency (HF) band is used for ionospheric communications, and the 300 MHz-3 GHz ultra-high-frequency (UHF) and 3-30 GHz super-high-frequency (SHF) bands are used for tropospheric scatter. Although the fading effects in a mobile radio system are somewhat different than those in ionospheric and tropospheric channels, the early models are still quite useful to help characterize fading effects in mobile digital communication systems. This tutorial addresses Rayleigh fading primarily in the UHF band. That affects mobile systems such as cellular and personal communication systems (PCS). Part I of the tutorial itemizes the fundamental fading manifestations and types of degradation.
716 citations
TL;DR: The number of parameters needed, parameter estimation, analytical tractability, and ability of traffic models to capture marginal distribution and auto-correlation structure of the actual traffic are discussed.
Abstract: Traffic models are at the heart of any performance evaluation of telecommunications networks An accurate estimation of network performance is critical for the success of broadband networks Such networks need to guarantee an acceptable quality of service (QoS) level to the users Therefore, traffic models need to be accurate and able to capture the statistical characteristics of the actual traffic We survey and examine traffic models that are currently used in the literature Traditional short-range and non-traditional long-range dependent traffic models are presented The number of parameters needed, parameter estimation, analytical tractability, and ability of traffic models to capture marginal distribution and auto-correlation structure of the actual traffic are discussed
482 citations
Journal Article•
429 citations
TL;DR: Two particular mitigation techniques are examined: the Viterbi equalizer implemented in the Global System for Mobile Communication (GSM) and the RAKE receiver used in CDMA systems built to meet Interim Standard 95 (IS-95).
Abstract: For pt. I see ibid., vol. 35, no. 7, p. 90, 1997. In Part I of this tutorial, the major elements that contribute to fading and their effects in a communication channel were characterized. In Part II, these phenomena are briefly summarized, and emphasis is then placed on methods to cope with these degradation effects. Two particular mitigation techniques are examined: the Viterbi equalizer implemented in the Global System for Mobile Communication (GSM), and the RAKE receiver used in CDMA systems built to meet Interim Standard 95 (IS-95).
TL;DR: The authors present a detailed description of the GPRS system, emphasizing the radio link protocol, and demonstrate its performance.
Abstract: In the Global System for Mobile Communications (GSM) Phase 2+ development, one major activity is to specify the general packet radio service (GPRS). The standardization is expected to be completed at the end of 1997. The purpose of GPRSI like other packet data services, is to efficiently accommodate data sources that are bursty in nature. Another important goal of the technology is to make it possible for GSM license holders to share physical resources on a dynamic, flexible basis between packet data services and other GSM services. The authors present a detailed description of the GPRS system, emphasizing the radio link protocol, and demonstrate its performance. The performance measures have been obtained from the WINLAB GPRS simulator.
TL;DR: If high altitude aeronautical platforms (HAAPs) prove to be reasonably stable, reliable, and not too costly, they will offer considerable opportunities for wireless services provision, and the introduction of innovative communications concepts such as cell scanning and stratospheric radio relays.
Abstract: The focus of this article is high altitude aeronautical platforms (HAAPs) such as airships, planes, helicopters, or some hybrid salutions which could operate at stratospheric altitudes for significant periods of time, be low-cost, and be capable of carrying sizable, multipurpose communications payloads. Of particular interest are ways to implement cellular/PCS or high-speed data networks in airborne platforms. From a communications perspective, HAAPs would have many advantages over both their terrestrial and satellite counterparts. If HAAPs prove to be reasonably stable, reliable, and not too costly, they will offer considerable opportunities for wireless services provision, and the introduction of innovative communications concepts such as cell scanning and stratospheric radio relays.
TL;DR: Annan B defines a low-bit-rate silence compression scheme designed and optimized to work in conjunction with both the full version of G.729 and its low-complexity Annex A, which enables the achievement of bit-rate savings for coded speech at average rates as low as 4 kb/s during normal speech conversation while maintaining reproduction quality.
Abstract: This article describes Annex B to ITU-T Recommendation G.729. Annex B defines a low-bit-rate silence compression scheme designed and optimized to work in conjunction with both the full version of G.729 and its low-complexity Annex A. To achieve good quality low-bit-rate silence compression, a robust frame-based voice activity detector module is essential to detect inactive voice frames, also called silence or background noise frames. For these detected inactive voice frames, a discontinuous transmission module measures the changes over time of the inactive voice signal characteristics and decides whether a new silence information descriptor frame should be sent to maintain the reproduction quality of the background noise at the receiving end. If such a frame is needed, the spectrum and energy parameters describing the perceptual characteristics of the background noise are efficiently coded and transmitted using 15 b/frame. At the receiving end, the comfort noise generation module regenerates the output background noise using transmitted updates or previously available parameters. The synthesized background noise is obtained by linear predictive filtering of a locally generated pseudo-white excitation signal of a controlled level. This method of coding the background noise enables the achievement of bit-rate savings for coded speech at average rates as low as 4 kb/s during normal speech conversation while maintaining reproduction quality.
TL;DR: This article is a tutorial on how RSVP can be used by end applications to ensure that they receive the end-to-end QoS that they require.
Abstract: The growing use of multimedia communication applications, with specific bandwidth and real-time delivery requirements has created the need for an integrated services Internet in which traditional best-effort datagram delivery can coexist with additional enhanced quality of service (QoS) delivery classes. Such classes provide data flows with QoS commitments with regard to bandwidth, packet loss, and delay through the reservation of network resources along the data path, which can be done using the Resource Reservation Protocol (RSVP). This article is a tutorial on how RSVP can be used by end applications to ensure that they receive the end-to-end QoS that they require.
TL;DR: In this paper, a medium access control protocol that conforms to the draft standard proposal for the GPRS air interface is introduced and analyzed, and the simulation model is described and simulation results presented.
Abstract: For almost three years the European Telecommunications Standards Institute (ETSI) has been working on the specification of the general packet radio service (GPRS) for the Global System for Mobile Communications (GSM). In the course of 1997 standardization will come to an end, and a first introduction of GPRS by a service provider or network operator is likely to take place in 1999. The new service will accommodate data connections with variable bit rates and high bandwidth efficiency, and thus offers the possibility to attract a wide range of new applications to GSM networks. In this article possible applications and elementary concepts and service characteristics of GPRS are explained in detail. Furthermore, a medium access control protocol that conforms to the draft standard proposal for the GPRS air interface is introduced and analyzed. Thereafter, the simulation model is described and simulation results presented. The performance analysis carried out shows reasonable performance even under high load conditions.
Journal Article•
TL;DR: A subsea wet electrical connector capable of repeated mating and unmating underwater at great depths and capable of operating under conditions of continuous and simultaneous high amperages and high voltages up to 35,000 volts while mated.
TL;DR: A realistic teletraffic modeling framework for personal communications services that captures complex human behaviors and has been validated through analysis of actual call and mobility data is presented.
Abstract: This article presents a realistic teletraffic modeling framework for personal communications services. The framework captures complex human behaviors and has been validated through analysis of actual call and mobility data. Using the proposed framework, a large-scale simulation was performed on a model of the San Francisco Bay area. Simulation results showing the performance of IS-41 are presented.
TL;DR: Two approaches to the design of a high-performance router, the gigabit router and the IP switch are examined, and some detail on the implementation of an IP switch and the protocols associated with IP switching is provided.
Abstract: To cope with the growth in the Internet and corporate IP networks, we require IP routers capable of much higher performance than is possible with existing architectures. This article examines two approaches to the design of a high-performance router, the gigabit router and the IP switch, and then provides some detail on the implementation of an IP switch and the protocols associated with IP switching.
TL;DR: In this article, the authors provide an overview of the means and techniques used for subscriber location management in present cellular mobile networks, mainly classified into non-memory-based and memory-based approaches.
Abstract: This article provides an overview of the means and techniques used for subscriber location management in present cellular mobile networks. The overhead due to location management techniques used in the present cellular systems such as GSM, in particular in high traffic spots, has already been a source of concern and is expected to augment dramatically in future wireless systems. Several proposals have been made in the past addressing the problem associated with the cost of location management. The author provides an overview of these contributions; in particular, he classifies the techniques, mainly into non-memory-based and memory-based approaches. Subsequently, a simple evaluation of the current location updating procedure used in GSM is presented in the context of a PCS framework to illustrate the load placed on the radio channels and on the MSC/VLR processing.
TL;DR: The goal of this article is to describe the main ideas behind the new class of codes called turbo codes, whose performance in terms of bit error probability has been shown to be very close to the Shannon limit.
Abstract: The goal of this article is to describe the main ideas behind the new class of codes called turbo codes, whose performance in terms of bit error probability has been shown to be very close to the Shannon limit. In this article, the mathematical measures of a posteriori probability and likelihood are reviewed, and the benefits of turbo codes are explained in this context. Since the algorithms needed to implement the decoders have been well documented by others, they are only referenced here, not described in detail. A numerical example, using a simple concatenated coding scheme, provides a vehicle for illustrating how error performance can be improved when soft outputs from the decoders are used in an iterative decoding process.
TL;DR: The main thrust of this article is that advances in real-time distributed object computing can be achieved only by systematically pinpointing performance bottlenecks; optimizing the performance of networks, ORB end systems, common services, and applications; and simultaneously integrating techniques and tools that simplify application development.
Abstract: Many application domains (e.g., avionics, telecommunications, and multimedia) require real-time guarantees from the underlying networks, operating systems, and middleware components to achieve their quality of service (QoS) requirements. In addition to providing end-to-end QoS guarantees, applications in these domains must be flexible and reusable. Requirements for flexibility and reusability motivate the use of object-oriented middleware like the Common Object Request Broker Architecture (CORBA). However, the performance of current CORBA implementations is not yet suited for hard real-time systems (e.g., avionics) and constrained latency systems (e.g., teleconferencing). This article describes the architectural features and optimizations required to develop real-time ORB end systems that can deliver end-to-end QoS guarantees to applications. While some operating systems, networks, and protocols now support real-time scheduling, they do not provide integrated solutions. The main thrust of this article is that advances in real-time distributed object computing can be achieved only by systematically pinpointing performance bottlenecks; optimizing the performance of networks, ORB end systems, common services, and applications; and simultaneously integrating techniques and tools that simplify application development.
IBM1
TL;DR: This article considers both multimedia application needs as well as networking requirements, and tries to bridge these paradigms using an adaptive framework that represents a multimedia connection in terms of multiple substreams each with their own specified QoS requirement.
Abstract: This article presents a framework for multimedia networking in a wireless and mobile environment. We consider both multimedia application needs as well as networking requirements, and try to bridge these paradigms using an adaptive framework. Central to this framework is the concept of representing a multimedia connection in terms of multiple substreams each with their own specified QoS requirement and making network elements (switching and access points), services, and protocols (signaling, control, routing) aware of the QoS requirements of such substreams. As resource availability in the wireless and mobile network fluctuates, the network selects and schedules substreams in order to present the information content with an acceptable quality at a receiver (or each receiver in case of multicast connections). This is done while achieving a reasonable utilization efficiency of network resources and sharing them in a fair manner.
TL;DR: In this article, it is shown that in the longer term ultrafast optical time-division techniques, together with wavelength multiplexing, will be used in networks at all levels, from the transcontinental backbone to the desktop.
Abstract: The advances in photonic device technologies are bringing ultra-high-bit-rate networking-at speeds towards 100 Gb/s and beyond-much closer to practical reality. It is increasingly likely that in the longer term ultrafast optical time-division techniques-together with wavelength multiplexing-will be used in networks at all levels, from the transcontinental backbone to the desktop. Examples of devices include a subpicosecond clock source packaged inside a laptop personal computer and an OTDM switch on a single semiconductor chip, both produced at HHI. Advances similar to these make it possible now to envisage the use of OTDM techniques, not just in the highest layers of national and international networks, but also much closer to the user-such as the world-first demonstrations at BT Laboratories of a 40 Gb/s TDMA LAN and a 100 Gb/s packet self-routing switch for multiprocessor interconnection. Ultrafast networks might even provide the interconnection backplane inside future desktop routers and servers with massive throughput.
Journal Article•
TL;DR: The advances in photonic device technologies are bringing ultra-high-bit-rate networking-at speeds towards 100 Gb/s and beyond-much closer to practical reality, making it possible now to envisage the use of OTDM techniques not just in the highest layers of national and international networks, but also much closer to the user.
Abstract: The advances in photonic device technologies are bringing ultra-high-bit-rate networking-at speeds towards 100 Gb/s and beyond-much closer to practical reality. It is increasingly likely that in the longer term ultrafast optical time-division techniques-together with wavelength multiplexing-will be used in networks at all levels, from the transcontinental backbone to the desktop. Examples of devices include a subpicosecond clock source packaged inside a laptop personal computer and an OTDM switch on a single semiconductor chip, both produced at HHI. Advances similar to these make it possible now to envisage the use of OTDM techniques, not just in the highest layers of national and international networks, but also much closer to the user-such as the world-first demonstrations at BT Laboratories of a 40 Gb/s TDMA LAN and a 100 Gb/s packet self-routing switch for multiprocessor interconnection. Ultrafast networks might even provide the interconnection backplane inside future desktop routers and servers with massive throughput.
TL;DR: The Mlisten data collection tool was created to provide a mechanism for capturing information about when members join and leave a multicast group, and statistics about some of the MBone sessions they monitored are presented.
Abstract: The multicast backbone (MBone) is a network overlaying the global Internet and designed to support multipoint applications. The authors first give an overview of the development and architecture of the current MBone. One important characteristic of the MBone is its reliance on IP multicast which allows receivers to join and leave groups asynchronously. The authors describe the Mlisten data collection tool that was created to provide a mechanism for capturing information about when members join and leave a multicast group. Using data collected with Mlisten, the authors present statistics about some of the MBone sessions they monitored. Results are provided for key parameters including multicast participant interarrival times and participant durations, multicast tree size and characteristics, and intersession relationships. Collecting data about MBone usage can improve our understanding of how multicast communication and real-time protocols are being used today.
TL;DR: The principles of random channel allocation schemes, as found in frequency-hopping or direct-sequence CDMA systems, are compared with deterministic dynamicChannel allocation schemes.
Abstract: Comparing market estimates for wireless personal communication and considering proposals for wideband multimedia services with the existing spectrum allocations for these types of systems show that spectrum resource management remains an important topic in the near and distant future. In this article the authors start by presenting a quite general formulation of the radio resource management problem where the three key allocation decisions are concerned with waveforms ("channels"), access ports (or base stations), and, finally, with transmitter power. Some approaches to these problems found in the literature are reviewed. In particular, the principles of random channel allocation schemes, as found in frequency-hopping or direct-sequence CDMA systems, are compared with deterministic dynamic channel allocation schemes. The article closes by giving an outlook of some of the key problems in resource management in future wireless multimedia systems.
TL;DR: The objective of this survey is to present the state of the art in satellite ATM networks and to point out open research problems.
Abstract: Satellite ATM networks have significant advantages over terrestrial ATM networks. Satellites provide unique advantages such as remote coverage with rapid deployment, distance insensitivity, bandwidth on demand, immunity to terrestrial disasters, and offering broadband links. Satellite ATM networks will play an important role in the rapidly evolving information infrastructure. However, there are several obstacles which need to be overcome so that satellite ATM networks can operate in full service. The objective of this survey is to present the state of the art in satellite ATM networks and to point out open research problems. We explain the satellite ATM network architecture and cover the requirements and technical barriers for seamless integration of ATM and satellite networks. We describe the feasibility of the existing ATM cell transport methods, and deal with conventional and new satellite link access methods, and some error control schemes for the satellite environment. We then describe the problems of the proposed traffic and congestion control schemes, followed by the error performance of the Transmission Control Protocol (TCP) and Service-Specific Connection-Oriented Protocol (SSCOP) for the satellite ATM network. We present basic requirements and a possible architecture for local area-metropolitan area network (LAN-MAN) interconnection using satellite ATM and then discuss the requirements for multimedia services in satellite ATM networks.
TL;DR: Broadband wireless access systems are emerging as a new and growing area of telecommunications, since the ability to provide access without extensive installation of copper or fiber infrastructures make wireless technology well suited for broadband services.
Abstract: This article reviews the technologies and potential markets, applications, and architectures for broadband wireless access. The emergence of wireless communications for cellular systems is presented, together with its projected future evolution to mobile wideband systems. The field of broadband access systems, services, and network architectures is also covered, and then systems for broadband wireless communications for indoor local area networks and outdoor public fixed access networks are discussed. Broadband wireless access systems are emerging as a new and growing area of telecommunications, since the ability to provide access without extensive installation of copper or fiber infrastructures make wireless technology well suited for broadband services. Finally, some of the key enabling technologies, such as adaptive antennas and video compression, and the future architectural directions of broadband wireless networks are presented.
TL;DR: An analysis of the propagation aspects at the bands foreseen for wireless broadband communication systems-microwaves, millimeter waves and infrared-is presented, also addressing the issue of the antennas and batteries.
Abstract: A brief overview of wireless broadband communication systems, those providing a data rate higher than 2 Mb/s and up to 155 Mb/s, is done by addressing some of the applications and services that are foreseen, as well as some of the technical challenges that need to be solved, and by referring to some safety considerations. After an introduction, the need for high data rates is justified, and possible applications are listed and compared, concerning user mobility and bandwidth. Then an analysis of the propagation aspects at the bands foreseen for these systems-microwaves, millimeter waves and infrared-is presented, also addressing the issue of the antennas and batteries for these systems.