Abstract — IP-based solutions to accommodate mobile hosts within existing internetworks do not address the distinctive features of wireless mobile computing. IP-based transport protocols thus suffer from poor performance when a mobile host communicates with a host on the fixed network. This is caused by frequent disruptions in network layer connectivity due to — i) mobility and ii) unreliable nature of the wireless link. We describe the design and implementation of I-TCP, which is an indirect transport layer protocol for mobile hosts. I-TCP utilizes the resources of Mobility Support Routers (MSRs) to provide transport layer communication between mobile hosts and hosts on the fixed network. With I-TCP, the problems related to mobility and the unreliability of wireless link are handled entirely within the wireless link; the TCP/IP software on the fixed hosts is not modified. Using I-TCP on our testbed, the throughput between a fixed host and a mobile host improved substantially in comparison to regular TCP. 1

We describe a prototype system that combines together the overlaid 3D graphics of augmented reality with the untethered freedom of mobile computing. The goal is to explore how these two technologies might together make possible wearable computer systems that can support users in their everyday interactions with the world. We introduce an application that presents information about our university’s campus, using a head-tracked, see-through, headworn, 3D display, and an untracked, opaque, handheld, 2D display with stylus and trackpad. We provide an illustrated explanation of how our prototype is used, and describe our rationale behind designing its software infrastructure and selecting the hardware on which it runs.

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We present extensions to a traditional cellular [Ses95] handoff system to handle the simultaneous operation of multiple wireless network interfaces. This new system allows mobile users to roam in a "Wireless Overlay Network" structure consisting of room-size, building-size, and wide-area data networks. In this structure, the user can connect to the wired network through multiple wireless subnets, and offers the best possible connectivity given the user's geographic location and local wireless connectivity. We present the basic handoff system and show that the handoff latency is bounded by the amount of time that the mobile host takes to discover that it has moved in or out of a new wireless overlay. To efficiently support applications that can not tolerate these disruptions, we present optimizations to this basic scheme that assume no knowledge about specific channel characteristics. For handoffs between room-size and building-size overlays, these optimizations lead to a handoff latenc...

Computer applications traditionally expect a static execution environment. However, this precondition is generally not possible for mobile systems, where the world around an application is constantly changing. This thesis explores how to support and also exploit the dynamic configurations and social settings characteristic of mobile systems. More specifically, it advances the following goals: (1) enabling seamless interaction across devices; (2) creating physical spaces that are responsive to users; and (3) and building applications that are aware of the context of their use. Examples of these goals are: continuing in your office a program started at home; using a PDA to control someone else's windowing UI; automatically canceling phone forwarding upon return to your office; having an airport overheaddisplay highlight the flight information viewers are likely to be interested in; easily locating and using the nearest printer or fax machine; and automatically turning off a PDA's audible e-mail notification when in a meeting.

CarNet is an application for a large ad hoc mobile network system that scales well without requiring a xed network infrastructure to route messages. CarNet places radio nodes in cars, which communicate using Grid, a novel scalable routing system. Grid uses geographic forwarding and a scalable distributed location service to route packets from car to car without ooding the network. CarNet will support IP connectivity as well as applications such as cooperative highway congestion monitoring, eet tracking, and discovery of nearby points of interest. 1 Introduction The Internet has evolved in a way that sacri ces dynamism in favor of scale: it groups nodes into an addressing and routing hierarchy that inhibits movement, and it depends on xed physical infrastructure that inhibits rapid deployment. We are designing a scalable and dynamic network architecture called Grid, which will enable new kinds of applications and will be easier to deploy than existing technology. We desire several...

This paper introduces the notion of “universal interaction,” allowing a device to adapt its functionality to exploit services it discovers as it moves into a new environment. Users wish to invoke services — such as controlling the lights, printing locally, or reconfiguring the location of DNS servers — from their mobile devices. But aprioristandardization of interfaces and methods for service invocation is infeasible. Thus,the challenge is to develop a new service architecture that supports heterogeneity in client devices and controlled objects, and which makes minimal assumptions about standard interfaces and control protocols. There are five components to a comprehensive solution to this problem: 1) allowing device mobility, 2) augmenting controllable objects to make them network-accessible, 3) building an underlying discovery architecture, 4) mapping between exported object interfaces and client device controls, and 5) building complex behaviors from underlying composable objects. We motivate the need for these components by using an example scenario to derive the design requirements for our mobile services architecture. We then present a prototype implementation of elements of the architecture and some example services using it, including controls to audio/visual equipment, extensible mapping, server autoconfiguration, location tracking, and local printer access.

Wireless data services, other than those for electronic mail or paging, have thus far been more promising than successful. We believe that future mobile information systems must be built upon heterogeneous wireless overlay networks', extending traditional wired and internetworked processing "islands" to hosts on the move over coverage areas ranging from in-room, in-building, campus, metropolitan, and wide-areas. Unfortunately, network planners continue to think in terms of homogeneous wireless communications systems and technologies. In this paper, we describe a new wireless data networking architecture that integrates diverse wireless technologies into a seamless internetwork. In addition, we describe the applications support services needed to make it possible for applications to continue to operate as mobile hosts roam across such networks. The architecture described herein is being implemented in a testbed at the University of California, Berkeley under joint government/industry sponsorship.

Over the past few years, Transmission Control Protocol (TCP) has become the most widely used transport layer protocol on the Internet. TCP performs poorly however, if one of the communicating hosts is a mobile wireless computer [6]. One way to address this performance problem is to modify TCP to make it aware of host mobility. Such an approach

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