709 research outputs found

    Medium Access Protocols for Interconnecting ATM and Wireless Networks

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    The current trend in modern telecommunication is that most of the traffic (CBR, VBR and ABR, real-time and delay-insensitive) in the fixed broadband networks will be carried by fixed-length packets. It is desirable to extend the services to wireless networks as well. However, one major difficulty in wireless networks is the limited spectrum available. Another difficulty is that the bit error rate (BER) of the wireless channel is typically much higher than that of the channels of the wireline broadband networks. The latter problem is amplified for military wireless networks that experience substantial link interference (e.g., multipath fading, other-user interference jamming). Therefore, we can only expect that the same services are being carried in a similar fashion but with a lower source rate. In this paper, a medium access protocol for interconnecting ATM and wireless networks is discussed, followed by some alternatives, and other issues pertaining to guaranteeing low BER. This research was conducted in support of Task 1.1 of the ATIRP project during FY 96 and continues under Task 4.3 for FY 97

    Satellite ATM network architectures: An overview

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    A satellite ATM network has been envisioned as the next information super-skyway. There has been a migration from traditional bent pipe satellites to onboard processing) ATM satellites. The current congestion in the Internet has motivated the use of alternate paths - using satellites to support global Internet transport and access. This article presents the various system and protocol layer architectures of SATM networks.published_or_final_versio

    The Design of a System Architecture for Mobile Multimedia Computers

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    This chapter discusses the system architecture of a portable computer, called Mobile Digital Companion, which provides support for handling multimedia applications energy efficiently. Because battery life is limited and battery weight is an important factor for the size and the weight of the Mobile Digital Companion, energy management plays a crucial role in the architecture. As the Companion must remain usable in a variety of environments, it has to be flexible and adaptable to various operating conditions. The Mobile Digital Companion has an unconventional architecture that saves energy by using system decomposition at different levels of the architecture and exploits locality of reference with dedicated, optimised modules. The approach is based on dedicated functionality and the extensive use of energy reduction techniques at all levels of system design. The system has an architecture with a general-purpose processor accompanied by a set of heterogeneous autonomous programmable modules, each providing an energy efficient implementation of dedicated tasks. A reconfigurable internal communication network switch exploits locality of reference and eliminates wasteful data copies

    Networking Support For Mobile Computing

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    With increasing use of small portable computers, wireless networks and satellites, a trend to support computing on the move has emerged. This trend is known as mobile computing or anytime and anywhere computing. Some people refer it as Nomadic computing. No matter which name is applied, all these terms really imply that a user may not maintain a fixed position in the network. The user is free to roam from one place to another. However the mobile user still expects uninterrupted network access and the ability to run some networked applications. To support such mobility, the user is typically provided a wireless interface to communicate with other fixed and mobile users. The mobile computing environment can be described by the following attributes (a) mobile users, (b) mobile support stations or base stations serving an area, (c) wireless interface, (d) wireless medium with varying channel characteristics (due to fading, noise, interference, etc.) and (e) various applications requiring specific support. A mobile computing environment raises such issues as how to route packets as the mobile user (hosts) moves from one place to the other and how to overcome limitations including limited bandwidth and storage. This tutorial presents an introduction to mobile computing, to the challenges introduced, and to emerging networking infrastructures for mobile computing

    Protocol Layering and Internet Policy

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    An architectural principle known as protocol layering is widely recognized as one of the foundations of the Internet’s success. In addition, some scholars and industry participants have urged using the layers model as a central organizing principle for regulatory policy. Despite its importance as a concept, a comprehensive analysis of protocol layering and its implications for Internet policy has yet to appear in the literature. This Article attempts to correct this omission. It begins with a detailed description of the way the five-layer model developed, introducing protocol layering’s central features, such as the division of functions across layers, information hiding, peer communication, and encapsulation. It then discusses the model’s implications for whether particular functions are performed at the edge or in the core of the network, contrasts the model with the way that layering has been depicted in the legal commentary, and analyzes attempts to use layering as a basis for competition policy. Next the Article identifies certain emerging features of the Internet that are placing pressure on the layered model, including WiFi routers, network-based security, modern routing protocols, and wireless broadband. These developments illustrate how every architecture inevitably limits functionality as well as the architecture’s ability to evolve over time in response to changes in the technological and economic environment. Together these considerations support adopting a more dynamic perspective on layering and caution against using layers as a basis for a regulatory mandate for fear of cementing the existing technology into place in a way that prevents the network from innovating and evolving in response to shifts in the underlying technology and consumer demand
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