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Selected Areas in Communications, IEEE Journal on

Issue 5 • Date Jun 1995

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Displaying Results 1 - 16 of 16
  • The asynchronous technique for carrier acquisition coordination

    Page(s): 908 - 912
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    In third-generation mobile systems cell dimensions will become lower and lower. So, on the one hand, an higher variance of the offered traffic per cell is expected and, on the other hand, the issue of reducing the signaling exchanges among base stations (BS's) becomes very important. A solution to the above-mentioned problems is the implementation of a dynamic channel allocation (DCA) strategy with distributed control. The DCA strategy foresees that the assignment of the carriers to the various cells is dynamically rearranged on a real time basis, in order to track the traffic evolution in the various cells. The distributed control entails that carrier acquisitions (and releases) are made by the BS's with minimal signaling exchanges. A fundamental problem of DCA strategies with distributed control concerns the coordination among BS's in order to avoid conflicting acquisitions of a same carrier from two BS's located at a distance lower than the reuse distance. This paper considers two techniques for performing the above-mentioned coordination: the synchronous technique and the asynchronous technique. Both techniques are suitable for being applied in a possible evolution of the pan-European Global System for Mobile communications (GSM). These techniques base on the presence of an acquisition delay between the acquisition stimulus time and the actual acquisition time; such acquisition delay permits coordination among BS's, but worsens performance in terms of blocking and dropping probabilities. It is shown that, in most cases, the asynchronous technique entails shorter acquisition delays than the synchronous one and thus attains better performance View full abstract»

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  • ViewStation applications: implications for network traffic

    Page(s): 768 - 778
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    This paper describes applications built on the ViewStation, a distributed multimedia system based on Unix workstations and a gigabit per second local area network. A key tenet of the ViewStation project is the delivery of media data not just to the desktop but all the way to the application program. As processing power continues to improve, our approach enables applications that perform intensive processing of audio and video data. We hypothesize that as media data are shaped by this software-based processing, the resultant network traffic patterns will be dominated more by software behavior than by so-called real-time issues. We have written applications that directly process live video to provide more responsive human-computer interaction. We have also developed applications to explore the potential of media processing to support content-based retrieval of prerecorded television broadcasts. These applications perform intelligent processing on video, as well as straightforward presentation. They demonstrate the utility of network-based multimedia systems that deliver audio and video data all the way to the application. The network requirements of the applications are modeled as a combination of bursty transfers and periodic packet-trains View full abstract»

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  • Impact of mobility on TCP/IP: an integrated performance study

    Page(s): 858 - 867
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    This paper presents a simulation analysis of the impact of mobility on TCP/IP augmented with features to support host mobility in wide area networks. Our results show that the existing version of TCP can yield low throughput in highly mobile environments due to the fact that TCP cannot discriminate packets dropped due to hand-offs with those dropped due to congestion in one or more network resources. As a result, TCP invokes a congestion recovery process when packets are lost during internetwork hand-offs of the mobile host. We investigate a proposal in which the transport layer explicitly receives information from the network layer of any ongoing mobility. We show that by effectively capitalizing this information, TCP can appropriately extend the slow-start phase in the recovery process and achieve higher throughput. Based on the simulation analysis we also show the robustness of this scheme in the presence of both host mobility and network congestion View full abstract»

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  • Accessing Earth system science data and applications through high-bandwidth networks

    Page(s): 793 - 805
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    We discuss gigabit network applications enabled by “Mission to Planet Earth”, an international effort to monitor the Earth as a system. We describe the design of a network architecture to support applications developed as part of this program; introduce a new component, public access resource centers (PARCs); and discuss how PARCs would facilitate access by users outside the traditional research community. We also describe how a particular class of users, agriculture users, might benefit from access to data collected as part of the Mission to Planet Earth program and delivered in a value-added form to them by a so-called AgPARC. The suggested architecture requires the deployment of high-bandwidth networks View full abstract»

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  • Networking requirements for interactive video on demand

    Page(s): 779 - 787
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    A significant driver for the consumer use of high bandwidth in the near future will be interactive video on demand (IVOD). A range of service types can be deployed, based on a differing sophistication, which must be traded against the network costs (bandwidth) and component costs (switch complexity and memory). The potential aggregate bandwidth required is huge (O(1Pb/s)), and thus it is essential to properly engineer the network to reduce the bandwidth required. This paper describes a variety of IVOD scenarios, and introduces a cost function that captures the combined bandwidth and storage requirements of the network. This cost function is used to compare different network engineering alternatives, particularly program caching and stream sharing. The effects of nonlinear pricing and differing weights of bandwidth and storage are also reflected by the cost function. This cost function can be used by network designers to determine optimal topology, sharing, and caching strategies for desired bandwidth versus memory costs in a particular network deployment. In addition, a simulation model is used to evaluate caching of programs or windows within programs. We show that there are some results that are widely applicable. In particular, the level in the network at which caching should take place is at approximately 80% depth in the distribution tree, above the head end switch in the network hierarchy. We also observe that the bandwidth savings in sharing streams (actually buffered windows of program content) is fairly small for user behavior based on Zipfs law. The overall intent of this work is to evaluate the effects of various server, cache, and sharing strategies on the bandwidth and storage requirements of the network and their proper placement within the network View full abstract»

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  • A mobile host protocol supporting route optimization and authentication

    Page(s): 839 - 849
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    Host mobility is becoming an important issue due to the recent proliferation of notebook and palmtop computers, the development of wireless network interfaces, and the growth in global internetworking. This paper describes the design and implementation of a mobile host protocol, called the Internet mobile host protocol (IMHP), that is compatible with the TCP/IP protocol suite, and allows a mobile host to move around the Internet without changing its identity, In particular, IMHP provides host mobility over both the local and wide area, while remaining transparent to the user and to other hosts communicating with the mobile host. IMHP features route optimization and integrated authentication of all management packets. Route optimization allows a node to cache the location of a mobile host and to send future packets directly to that mobile host. By authenticating all management packets, IMHP guards against possible attacks on packet routing to mobile hosts, including the interception or redirection of arbitrary packets within the network. A simple new authentication mechanism is introduced that preserves the level of security found in the Internet today, while accommodating the transition to stronger authentication based on public key cryptography or shared keys that may either be manually administered or provided by a future Internet key management protocol View full abstract»

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  • An efficient location and routing scheme for mobile computing environments

    Page(s): 868 - 879
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    One of the most important issues affecting host mobility is the location and routing scheme that allows hosts to move seamlessly from one site to another. This paper presents a method that exploits the locality properties of a host's pattern of movement and access history. Two concepts, “local region” and “patron service” are introduced based on the locality features. For each mobile host, the local region is a set of designated subnetworks within which a mobile host often moves, and the patrons are the hosts from which the majority of traffic for the mobile host originated. These are used to confine the effects of a host moving, so location updates are sent only to its local area, and to those source hosts which are most likely to call again. Our scheme has the advantages of limiting location updates, and providing optimal routing, while increasing network and host scalability View full abstract»

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  • Network requirements for 3-D flying in a zoomable brain database

    Page(s): 816 - 827
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (772 KB)  

    In laboratories around the world, neuroscientists from diverse disciplines are exploring various aspects of brain structure. Because of the size of the domain, neuroscientists must specialize, making it difficult to fit results together, causing some research efforts to be duplicated because of lack of sharing of information. The authors have begun a long-term project to build a neuroscience research database for brain structure. One aspect of the database is the ability to visualize high-quality, high-resolution micrographs montaged together into 3-D structures as they were in the living brain. As demonstrated in this paper's analysis, realistic presentation of these visualizations across computer networks will stress current and proposed gigabit networks. Image compression can reduce network loads, but wide-spread use of the visualizations will still require networks capable of sustaining terabits per second of throughput View full abstract»

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  • Dynamic resource allocation tor multimedia services in mobile communication environments

    Page(s): 913 - 922
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    As demand for networked multimedia applications is increasing rapidly, it is important to provide these services in mobile communication environments. In this paper, we identify system requirements for base stations in order to support multimedia services. These requirements include supporting concurrent connections for multiple users, allocation of resources dynamically to satisfy diverse resource requirements for multimedia applications, and reallocation of resources during handoff incurred by user movement or newly generated calls. These requirements can be used to design an interface between land-based and mobile environments to handle one of the most challenging issues in multimedia communication: enforcing interstream and intrastream synchronizations. We propose two quality of presentation (QOP) parameters for evaluating the quality of mobile multimedia connections, and analyze the validity of these requirements View full abstract»

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  • Production-quality video over broadband networks: a system description and two interactive applications

    Page(s): 806 - 815
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    The Washington University MultiMedia eXplorer (MMX) is a complete, host-independent multimedia system capable of transmitting and receiving JPEG-compressed video, CD-quality audio, and high-resolution radiographic images over the Washington University broadband ATM network. If the host is equipped with an ATM interface card, normal network traffic can be supported via an ATM extension port on the MMX. The major components of the MMX are an ATMizer and three multimedia channels. The ATMizer implements the host interface, the interface to the ATM network, and the interface to the three multimedia channels. This paper describes the architecture of the MMX, the software used with the system, and two applications that have been developed to demonstrate the capability of broadband ATM networks for multimedia applications View full abstract»

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  • Defining high-speed protocols: five challenges and an example that survives the challenges

    Page(s): 828 - 835
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    The First IEEE Gigabit Networking (GBN) Workshop defined a set of characteristics of “Interesting” high-speed applications. The GBN criteria ensure that the application addresses a significant problem, and that it actually requires a gigabit network. This paper presents five challenges that augment the GBN criteria. These challenges ask whether gigabit applications require new research into different protocols, or can be supported by existing protocols that merely run faster. It shows a class of applications, interactive distributed multimedia, namely interactive real-time World Wide Web (WWW) access, that survive the challenges. It also shows how source presenting is a way to use excess bandwidth-delay product to reduce the browser response time, and how this is one example of a truly gigabit protocol View full abstract»

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  • Two-way calling public CT2 telepoint system

    Page(s): 923 - 931
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    In most current implementations of CT2 telepoint systems, only handset initiated calls are allowed. This paper describes a design to allow two-way calling for the CT2 public telepoint system with minimal modifications to the current CT2 infrastructure and the public switched telephone network (PSTN). The design makes use of centralized databases in the home location register (HLR) and visitor location registers (VLR) to track the location of handsets. This location information is stored in the VLR and HLR, and is used by the PSTN to route incoming calls destined for CT2 handsets to the appropriate CT2 telepoint base station (TBS). The TBS connect to the PSTN local exchanges (LE) through the integrated services digital network (ISDN) basic rate interfaces (BRI) for fast out-of-band signaling. We present simulation results of the system with the objective of determining where congestion might occur within the system and to understand the impact of the new implementation on the PSTN. The results indicate that the performance of the system will be limited by the VLR processing speed and the number of ISDN BRI's connecting the ISDN front end (IFE) to the PSTN View full abstract»

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  • Improving the performance of reliable transport protocols in mobile computing environments

    Page(s): 850 - 857
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    We explore the performance of reliable data communication in mobile computing environments. Motion across wireless cell boundaries causes increased delays and packet losses while the network learns how to route data to a host's new location. Reliable transport protocols like TCP interpret these delays and losses as signs of network congestion. They consequently throttle their transmissions, further degrading performance. We quantify this degradation through measurements of protocol behavior in a wireless networking testbed. We show how current TCP implementations introduce unacceptably long pauses in communication during cellular handoffs (800 ms and longer), and propose an end-to-end fast retransmission scheme that can reduce these pauses to levels more suitable for human interaction (200 ms). Our work makes clear the need for reliable transport protocols to differentiate between motion-related and congestion-related packet losses and suggests how to adapt these protocols to perform better in mobile computing environments View full abstract»

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  • North Carolina Information Highway: megabits driving gigabits

    Page(s): 788 - 792
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (604 KB)  

    The North Carolina Information Highway (NCIH) is the first large-scale commercial deployment of a broadband ATM network. Starting with initial service in August 1994, the NCIH will eventually provide 155 Mb/s ATM service to thousands of high schools, colleges, universities, libraries, hospitals, prisons, police stations, and other government facilities throughout North Carolina. Fully deployed, the NCIH is expected to have a total access capacity of over 500 Gb/s View full abstract»

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  • An alternative strategy for location tracking

    Page(s): 880 - 892
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    Mobile radio communications raise two major problems. First: a very poor radio link quality. Second: the users' mobility, which requires the management of their position, is resource consuming (especially radio bandwidth). This paper focuses on the second issue and proposes an intelligent method for users locating: the alternative strategy (AS). Our proposal is based on the observation that the mobility behavior of a majority of people can be foretold. If taken into consideration by the system, this characteristic can save signaling messages due to mobility management procedures, leading thus to savings in the system resources. Several versions of the AS are described: a basic version for long term events (i.e., received calls and registrations), and versions with increased memory for short and medium term events. The evaluation of the basic versions was performed using analytic and simulation approaches. It shows that storing the mobility related information brings great savings in system resources when the users have medium or high predictable mobility patterns. More generally speaking, this work points out the fact that the future systems will have to integrate users related information in order: firstly: to provide customized services and secondly: to save system resources. On the other hand, current trends in mobile communications show that adaptive and dynamic system capabilities require that more information to be collected and computed View full abstract»

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  • A methodology for the performance evaluation of data query strategies in universal mobile telecommunication systems (UMTS)

    Page(s): 893 - 907
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    The anticipated emergence of third-generation mobile systems, referred to as universal mobile telecommunication systems (UMTS), raises the problem of reconsidering the design of the databases destined to contain the user information. In particular, it is expected that the key concepts of the new database architectures will be high distribution and fast updating of information. So far, the problem of determining the most appropriate distributed database (DDB) architectures for third-generation mobile systems has not been widely dealt with in literature. This paper presents a methodology for evaluating hierarchical DDB architectures by means of an analytical model of the data querying operation. This methodology allows for structural alternatives, differing on account of the number of levels and branches in the hierarchy, to be evaluated in terms of query loads and mean response times, according to a given user mobility characterization and a given search protocol operation. By way of illustration, the paper discusses a case study, concerning a query operation arising from a location updating procedure and applied to a hierarchical tree-like DDB in which some structural alternatives are considered View full abstract»

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Aims & Scope

IEEE Journal on Selected Areas in Communications focuses on all telecommunications, including telephone, telegraphy, facsimile, and point-to-point television, by electromagnetic propagation.

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Meet Our Editors

Editor-in-Chief
Muriel Médard
MIT