Showing papers on "Mobile search published in 1994"
622 citations
29 Nov 1994
TL;DR: This paper presents system support for maintaining the consistency of replicated data and for providing transaction schemas that account for the frequent but predictable disconnections, the mobility, and the vulnerability of the wireless environment.
Abstract: It is expected that in the near future, tens of millions of users will have access to distributed information systems through wireless connections. The technical characteristics of the wireless medium and the resulting mobility of both data resources and data consumers raise new challenging questions regarding the development of information systems appropriate for mobile environments. In this paper, we report on the development of such a system. First, we describe the general architecture of the information system and the main considerations of our design. Then, based on these considerations, we present our system support for maintaining the consistency of replicated data and for providing transaction schemas that account for the frequent but predictable disconnections, the mobility, and the vulnerability of the wireless environment.
102 citations
TL;DR: The mobile user will typically use powerful palmtop or laptop computers that are equipped with wireless communication capability to connect towired networks as discussed by the authors, and this type of computing environment is referred to as mobile computing.
Abstract: munication and wireless LAN technology will make it possible, in the near future, for mobile users to transparently access communication networks from anywhere at any time. The mobile user will typically use powerful palmtop or laptop computers that are equipped with wireless communication capability to connect towired networks. This type of computing environment is referred to as mobile computing. The mobility of the nodes and the small size (in terms of storage space) of the hand-held devices make traditional solutions to network problems such as
96 citations
08 Dec 1994
TL;DR: The design of Mobisaic is described, the mechanism it uses for representing a user's mobile content and the extensions made to the syntax and function of Uniform Resource Locators and HyperText Markup Language documents to support mobility are described.
Abstract: Mobisaic is a World Wide Web information system designed to serve users in a mobile wireless computing environment. Mobisaic extends the Web by allowing documents to both refer and react to potentially changing contextual information, such as current location in the wireless network. Mobisaic relies on client side processing of HTML documents that support two new concepts: dynamic uniform resource locators (URLs) and active documents. A dynamic URL is one whose results depend upon the state of the user's mobile context at the time it is resolved. An active document is one that automatically updates its contents in response to changes in a user's mobile context. The paper describes the design of Mobisaic, the mechanism it uses for representing a user's mobile context, and the extensions made to the syntax and function of uniform resource locators and HyperText markup language documents to support mobility.
92 citations
08 Dec 1994
TL;DR: This paper investigates means for providing transaction support appropriate for mobile environments and defines a model that ensures a weaker notion of consistency, accounts for mobility, and provides for recovery.
Abstract: It is expected that in the near future millions of users will have access to on-line distributed databases through mobile computers. The restrictions imposed by the nature of the wireless medium and the resulting mobility of data consumers and data producers make traditional transaction models inadequate. In this paper, we investigate means for providing transaction support appropriate for mobile environments. Specifically, we define a model that ensures a weaker notion of consistency, accounts for mobility, and provides for recovery.
61 citations
01 Jan 1994
TL;DR: In this paper, the authors describe the architecture and implementation of a mobile IP system, which allows mobile hosts to roam between cells implemented with 2-Mbps radio base stations, while maintaining Internet connectivity.
Abstract: This paper describes the architecture and implementation of a mobile IP system. It allows mobile hosts to roam between cells implemented with 2-Mbps radio base stations, while maintaining Internet connectivity. The system is being developed as part of a course on wireless networks at Harvard and has been operational since March 1994. The architecture scales well, both geographically and in the number of mobile hosts supported. It supports secure short-cut routing to mobile hosts using the existing Internet routing system without change. The implementation demonstrates a robust, low complexity realization of the architecture, and provides trade-off opportunities between efficiency and cost. Measured performance of the mobile system is generally excellent. The system can handle a high rate of location updates, and routes packets almost as efficiently for mobile hosts as the Internet does for stationary hosts. We observe reasonable TCP behavior during hand-offs.
53 citations
08 Dec 1994
TL;DR: The design of a distributed systems platform to support tile development of services which are able to tolerate this environment by dynamically adapting to changes in tile available communications quality-of-service is discussed.
Abstract: Future computer environments will include mobile computers which will either be disconnected, weakly interconnected by low-speed wireless networks such as GSM (global system for mobile communications), or fully interconnected by high-speed networks ranging from Ethernet to ATM (asynchronous transfer mode). While the transition between networks is currently a heavyweight operation, we believe that developments in network interface technology will soon enable mobile computers to dynamically select their network service based on cost and performance requirements. Such flexibility, coupled with the inherent unreliability of mobile communications, means that system services and applications will be subject to rapid and massive fluctuations in the quality-of-service provided by their underlying communications infrastructure. In this paper, we discuss the design of a distributed systems platform to support the development of services which are able to tolerate this environment by dynamically adapting to changes in the available communications quality-of-service.
53 citations
TL;DR: Remote programming enables occasionally connected devices to connect to each other to do things that would be prohibitively expensive with remote procedure calling.
Abstract: Remote programming enables occasionally connected devices to de things that would be prohibitively expensive with remote procedure calling. Mobile agents simplify the developmen t and introduction of new communicating applications. >
47 citations
27 Jun 1994
TL;DR: A new service to support shared libraries in mobile environments is proposed and the integration of this service into a wider architecture of reactive services being developed to support distributed mobile computing is discussed.
Abstract: A key characteristic of mobile computing is that the end systems involved can experience differing degrees of connectivity during typical operational cycles. The paper discusses the issues associated with developing distributed system services to operate in such an environment. We focus on the provision of file system support and argue that existing file systems, including those developed for use in a mobile environment, contain assumptions about their underlying communications infrastructures which are unlikely to hold in a mobile environment. This argument is supported by an in-depth examination of a specific file system issue: the support of shared libraries. A new service to support shared libraries in mobile environments is proposed and we discuss the integration of this service into a wider architecture of reactive services being developed to support distributed mobile computing. >
35 citations
Proceedings Article•
06 Jun 1994TL;DR: The architecture of the mobile IP system allows mobile hosts to roam between cells implemented with 2-Mbps radio base stations, while maintaining Internet connectivity, and routes packets almost as efficiently for mobile hosts as the Internet does for stationary hosts.
Abstract: This paper describes the architecture and implementation of a mobile IP system. It allows mobile hosts to roam between cells implemented with 2-Mbps radio base stations, while maintaining Internet connectivity. The system is being developed as part of a course on wireless networks at Harvard and has been operational since March 1994.
The architecture scales well, both geographically and in the number of mobile hosts supported. It supports secure short-cut routing to mobile hosts using the existing Internet routing system without change. The implementation demonstrates a robust, low complexity realization of the architecture, and provides trade-off opportunities between efficiency and cost.
Measured performance of the mobile system is generally excellent. The system can handle a high rate of location updates, and routes packets almost as efficiently for mobile hosts as the Internet does for stationary hosts. We observe reasonable TCP behavior during hand-offs.
25 citations
08 Dec 1994
TL;DR: Alternative approaches for providing mechanisms that enable mobile hosts to discover and access needed resources on the foreign network are outlined and their relative merits and limitations are discussed.
Abstract: As mobile computers move from one place to another, their "physical" points of attachment to the network change from time to time. Host movement causes service disruption. The Mobile-IP protocol attempts to solve this problem by hiding the effect of change in network service access points from the transport and higher layers. Thus, Mobile-IP ensures that a mobile host remains "virtually" connected to its home regardless of its current point of attachment. This allows existing applications to operate over mobile nodes without any modifications. While away from home, mobile hosts continue to access services from servers located at the home network. Applications running on mobile hosts therefore experience increased latency as accesses to home resources (such as name servers, file servers, etc.) are routed over multiple links and routers. To alleviate this problem, new mechanisms are required that enable mobile hosts to discover and access needed resources on the foreign network. In this paper, we outline alternative approaches for providing such mechanisms and discuss their relative merits and limitations.
08 Dec 1994
TL;DR: This paper defines a model that ensures a weaker notion of consistency, accounts for mobility, and provides for recovery for transaction support appropriate for mobile environments.
Abstract: It is expected that in the near future millions of users will have access to on-line distributed databases through mobile computers. The restrictions imposed by the nature of the wireless medium and the resulting mobility of data consumers and data producers make traditional transaction models inadequate. In this paper, we investigate means for providing transaction support appropriate for mobile environments. Specifically, we define a model that ensures a weaker notion of consistency, accounts for mobility, and provides for recovery.
08 Dec 1994
TL;DR: This paper proposes a design for a access mechanism specific to a mobile environment and provides data consistency by using the prony services, a centralized data rnanager with callbacks, and strict-reads.
Abstract: Reducing communication cost is important-in a mobile enuironment, because transmission of data over the radio link is slow, expensive, and unreliable. Providing data consistencg is crucial because-many mobile applilcations are database applications which rely on consistent data. In this paper we propose a design for a fiIe access mechanism specific to a mobile environment. Our two main design goals are to reduce communication cost and to provide data consistency. We reduce the amount of communication by extensive use of caching, profile inforrnation (files the user accesses), a proxy process, delayed writes, and availability of loose-reads. We provide data consistency by using the prony services, a centralized data rnanager with callbacks, and strict-reads. Our design is general enough to suit the needs of both mobile database and office applicati,ons.
18 Sep 1994
TL;DR: The Walkstation project is realizing a testbed for such a mobile computing environment using a modified set of Internet protocols based on the work of the internet working group on mobile IP (Internet protocol), which cover low power VLSI, cellular infrastructures, network integration, and mobility aware applications.
Abstract: Wireless LANs (WLAN) will soon be as popular as Ethernet is today. First products for DECT and 2.4 GHz systems will be available this year. How can these WLANs be connected to the Internet? Which problems arise when mobile users appear as guests in foreign networks? The Walkstation project is realizing a testbed for such a mobile computing environment using a modified set of Internet protocols. These protocols are based on the work of the internet working group on mobile IP (Internet protocol). Other aspects of the Walkstation project cover low power VLSI, cellular infrastructures, network integration, and mobility aware applications.
01 Sep 1994
TL;DR: It was noticed that performing search-updates significantly reduced the search costs with very little cost to pay for updates (upon moves and searches).
Abstract: : A search-update occurs after a successful search, when the location information corresponding to the searched mobile host is updated at some hosts. This paper proposes various strategies for search-updates. It was noticed that performing search-updates significantly reduced the search costs with very little cost to pay for updates (upon moves and searches).
08 Dec 1994
TL;DR: This position paper explores the convergence of computation with communications and control applications, and the models of mobile computing that consequently arise.
Abstract: The advent of ubiquitous mobile computing has widely been regarded as the convergence of pager-like communications technology and laptop-like computational power enabling applications that span both realms of functionality. However ubiquitous mobile computing, coupled with the proliferation of microprocessor-controlled appliance s and networking, creates another important new application arena: that in which mobile computers act as controllers for and interfaces to, appliances and services in the surrounding environment. This position paper explores the convergence of computation with communications and control applications, and the models of mobile computing that consequently arise. Established applications and models are positioned relative to this framework, and hither to unexplored control-based models of mobile computation are described.
12 Apr 1994
TL;DR: The technical solutions designed for the first prototype of an audio-visual mobile terminal with special emphasis in the video coding options are described.
Abstract: The recent explosion in the number of mobile terminals awoke the scientific community to the need of providing in a short time audio-visual services in mobile environments. Due to the low bandwidth available and the critical characteristics of mobile channels, audio and video source coding as well as channel coding became more complex and thus new solutions must be provided. This paper describes the technical solutions designed for the first prototype of an audio-visual mobile terminal with special emphasis in the video coding options. >
07 Sep 1994
TL;DR: All applications used by a mobile user will have different looks unless the developers have all referred to a common style guide on building the interface, and for the user it means using a homogeneous set of tools.
Abstract: All applications used by a mobile user will have different looks unless the developers have all referred to a common style guide on building the interface This will create a common look and feel, and for the user it means using a homogeneous set of tools These will be even easier to use if they work according to man's logic We need intuitive interfaces, hence our goal oriented approach in the style guide The end-user must know what he wants, but not how to obtain it (all the intermediate steps performed for actually accomplishing the desired action)
18 Sep 1994
TL;DR: A complete system architecture to enable mobile computing, called MOBI-DICK, is presented and can be used as a programming platform to hide the specifics of mobile computing from the application programmer.
Abstract: Systems with both mobile and stationary computers are of increasing importance. Mobile users can access information anywhere and anytime. Basic components needed for mobile computing are smart portable computers and wireless communication networks. Major problems due to mobility and the specific characteristics of portable computers and wireless communications are dynamic configuration, moving resources, reachability, data and function consistency. A complete system architecture to enable mobile computing, called MOBI-DICK, is presented. This system can be used as a programming platform to hide the specifics of mobile computing from the application programmer.
18 Sep 1994
TL;DR: The current status of the 115 kb/s infra-red interface that has been designed to connect PDAs, sub-notebooks and other portable computers to cellphones is introduced and the Hewlett-Packard Serial Infra-Red Link is introduced before reviewing the current proposal.
Abstract: This paper introduces the current status of the 115 kb/s infra-red interface that has been designed to connect PDAs, sub-notebooks and other portable computers to cellphones. Experience from mobile multimedia trials has enabled us to identify key issues with mobile multimedia communications. These potential problems are addressed using infra-red communications, as proposed by the Infra-Red Data Communications Association (IRDA), to firstly decouple the functions of the mobile phone and mobile computing device, and secondly to provide a simple and inexpensive communications interface. We outline the key issues and introduce the Hewlett-Packard Serial Infra-Red Link (HP SIR) before reviewing the current proposal.
TL;DR: This special issue on mobile communications comprises five articles, each of which covers a different aspect of mobile communications, and develops low-overhead high-performance service provider solutions.
Abstract: The principal problem faced by networks with mobile users is how to ensure that the service provider functions keep pace with the continually changing network state resulting from user mobility, without consuming large amounts of network resources in the process. Regardless of whether the users are mobile or stationary, all telecommunications networks must perform basic service provider functions such as controlling access to services, locating users, routing traffic, and accounting and billing for service use. However, in the presence of mobile users, all of these functions must be performed much more often and much more rapidly. Developing low-overhead high-performance service provider solutions has been and will continue to be a key area of research in mobile communications. This special issue on mobile communications comprises five articles, each of which covers a different aspect of mobile communications. >
Journal Article•
05 Dec 1994
TL;DR: A new conference key distribution scheme for digital mobile communication systems which enables two or more users to hold a secure conference and a group of users can generate a common secret key over the public channel.
Abstract: We propose a new service for digital mobile communication systems which enables two or more users to hold a secure conference. Two requirements must be considered: privacy and authentication. Privacy is to ensure that an eavesdropper cannot intercept conversations. Authentication ensures that the service is not obtained fraudulently in order to avoid charge for usage. We present a new conference key distribution scheme for digital mobile communication systems. In the scheme, a group of users can generate a common secret key over the public channel to hold a secure conference.
08 Dec 1994
TL;DR: This paper discusses the adaptations of R.A. Golding's weak-consistency group communication and membership protocols for robustness in mobile environments.
Abstract: Mobile computer users may have multiple computers and various communication methods available to them. Thus, effective electronic mail services in diverse mobile environments, including both wireless and wireline scenarios, can be significantly enhanced using replication services. In this paper, we discuss our adaptations of R.A. Golding's (1992) weak-consistency group communication and membership protocols for robustness in mobile environments.