Showing papers on "Mobile telephony published in 1997"

Application of antenna arrays to mobile communications. II. Beam-forming and direction-of-arrival considerations

Abstract: Array processing involves manipulation of signals induced on various antenna elements. Its capabilities of steering nulls to reduce cochannel interferences and pointing independent beams toward various mobiles, as well as its ability to provide estimates of directions of radiating sources, make it attractive to a mobile communications system designer. Array processing is expected to play an important role in fulfilling the increased demands of various mobile communications services. Part I of this paper showed how an array could be utilized in different configurations to improve the performance of mobile communications systems, with references to various studies where feasibility of apt array system for mobile communications is considered. This paper provides a comprehensive and detailed treatment of different beam-forming schemes, adaptive algorithms to adjust the required weighting on antennas, direction-of-arrival estimation methods-including their performance comparison-and effects of errors on the performance of an array system, as well as schemes to alleviate them. This paper brings together almost all aspects of array signal processing.

Applications of antenna arrays to mobile communications. I. Performance improvement, feasibility, and system considerations

Abstract: The demand for wireless mobile communications services is growing at an explosive rate, with the anticipation that communication to a mobile device anywhere on the globe at all times will be available in the near future. An array of antennas mounted on vehicles, ships, aircraft, satellites, and base stations is expected to play an important role in fulfilling the increased demand of channel requirement for these services, as well as for the realization of the dream that a portable communications device the size of a wristwatch be available at an affordable cost for such services. This paper is the first of a two-part study. It provides a comprehensive treatment, at a level appropriate to nonspecialists, of the use of an antenna array to enhance the efficiency of mobile communications systems. It presents an overview of mobile communications as well as details of how an array may be used in various mobile communications systems, including land-mobile, indoor-radio, and satellite-based systems. It discusses advantages of an array of antennas in a mobile communications system, highlights improvements that are possible by using multiple antennas compared to a single antenna in a system, and provides details on the feasibility of antenna arrays for mobile communications applications.

Mobile IP

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.

Mobile telecommunications network having integrated wireless office system

Abstract: A mobile telecommunications network having an integrated wireless office system is disclosed. A wireless office system is integrated into both a private telephony network (PTN) and a public land mobile network (PLMN) which includes a public cellular system. The wireless office system provides mobile service to corporate mobile terminals (CMTs) that are part of a corporate group of terminals of the PTN. The CMTs of the wireless office system appear to the PTN as normal fixed extension terminals and PTN internal features such as call back, caller identification and operator assistance may be used at the CMTs.

Providing caller ID within a mobile telecommunications network

Abstract: A calling party directory number (SRI) associated with a terminating call towards an unreachable mobile station (30) is stored at a home location register (HLR) associated with the unreachable mobile station (30). Thereafter, the HLR (50) receives an indication from a particular mobile switching center (MSC) (40) that the mobile station (30) is now reachable. In response to such an indication, the HLR (50) retrieves the previously stored calling party directory number and transmits the retrieved directory number to the reachable mobile station (30) using unstructured messages. By displaying the transmitted number, the mobile station (30) is able to inform the mobile subscriber of the attempted incoming calls received while the mobile station was either turned off or out of the service area.

AGENT TCL: targeting the needs of mobile computers

Abstract: Mobile computers have become increasingly popular as users discover the benefits of having their electronic work available at all times. Using Internet resources from a mobile platform, however, is a major challenge. Mobile computers do not have a permanent network connection and are often disconnected for long periods. When the computer is connected, the connection is often prone to sudden failure, such as when a physical obstruction blocks the signal from a cellular modem. In addition, the network connection often performs poorly and can vary dramatically from one session to the next, since the computer might use different transmission channels at different locations. Finally, depending on the transmission channel, the computer might be assigned a different network address each time it reconnects. Mobile agents are one way to handle these unforgiving network conditions. A mobile agent is an autonomous program that can move from machine to machine in a heterogeneous network under its own control. It can suspend its execution at any point, transport itself to a new machine, and resume execution on the new machine from the point at which it left off. Agent Tcl is a mobile agent system whose agents can be written in Tcl, Java, and Scheme. Agent Tcl has extensive navigation and communication services, security mechanisms, and debugging and tracking tools. We focus on Agent Tcl's architecture and security mechanisms, its RPC system, and its docking system, which lets an agent move transparently among mobile computers, regardless of when they are connected to the network.

Mobile Communications Engineering: Theory and Applications

Abstract: From the Publisher: The first edition of this classic reference work explained the design and development of mobile radio systems for voice and data in rigorous yet clear terms. Now Dr. William Lee has fully updated his guide to cover all the new technologies that are changing the face of mobile communications. Instead of merely describing the various existing and emerging systems, Dr. Lee helps you understand the crucial differences between applications for wireline and wireless communications.

Mobility modeling in third-generation mobile telecommunications systems

Abstract: In mobile communications, mobility modeling is involved in several aspects related to signaling and traffic load analysis. In third-generation systems, the influence of mobility on the network performance (e.g., handover rate) will be strengthened, mainly due to the huge number of mobile users in conjunction with the small cell size. In particular, the accuracy of mobility models becomes essential for the evaluation of system design alternatives and network implementation cost issues. The authors propose three basic types of mobility models, which are appropriate for the analysis of the full range of mobile communications design issues. The models provide different levels of detail regarding the user mobility behavior. In particular, (a) the city area model traces user motion at an area zone level, (b) the area zone model considers users moving on a street network, and (c) the street unit model tracks user motion with an accuracy of a few meters. The validity of the basic models for mobile communications design aspects is highlighted. Moreover, an "integrated mobility modeling tool" which considers the basic mobility models as components is proposed, aiming at the development of a refined modeling approach. This is achieved by improving the accuracy of the input parameters of each basic model via the exchange of some specific (mobility-related) parameters among the component models. To justify the applicability of the proposed integrated tool for both the analysis of design aspects and network planning, indicative results are presented, derived from simulation-based application examples of the three basic mobility models.

Mobile IP: The Internet Unplugged

Abstract: Each chapter concludes with a Chapter Summary. I. INTRODUCTION. 1. Introduction. What Is Driving Mobile Communications? What Background Do I Need to Understand This Book? Who Is the Target Audience of This Book? What Is the Purpose of This Book? What Notation Is Used throughout This Book? Are We Talking about IPv4 or IPv6? How Can I Obtain RFCs and Internet Drafts? What Is the Roadmap for the Rest of This Book? 2. Computer Networking Tutorial. How Do Computers Communicate? What Is the Internet Protocol (IP)? How Does IP Routing Work? How Are Routing-Table Entries Created? Why is Routing Based on Network-Prefix? How Can We Translate Names into Addresses? How Can We Determine Link-Layer Addresses? 3. The Need for Mobile. What Happens When a Node Changes Link? Can't You Solve This Problem with Host-Specific Routes? Why Not Just Change the Node's IP Address? Can't You Just Solve This at the Link Layer? What If I Only Need Nomadicity? II. MOBILE. 4. Mobile Overview. Is Mobile an Official Standard? What Problems Does Mobile Solve? What Is the Scope of the Mobile Solution? What Are the Requirements for Mobile? What Are the Design Goals for Mobile? What Assumptions Does Mobile Make? Where Does Mobile Reside? At a 10,000-Foot Level, How Does Mobile Work? 5. Mobile: The Gory Details. What Is the Mobile IP Design Philosophy? What Is Agent Discovery? What Is Registration? How Are Packets Routed to and from Mobile Nodes? 6. Tunneling. What Is IP Fragmentation? What Is IP in IP Encapsulation? What Is Minimal Encapsulation? What Is Generic Routing Encapsulation (GRE)? III. APPLYING MOBILE. 7. Security Primer. What Do We Mean by Security? What Is Cryptography? What Do We Mean by Confidentiality? What Do We Mean by Authentication, Integriy? How Can We Manage Keys Securely? What Security Protocols Are Used in the Internet? What Are Firewalls? 8. Campus Mobility:. What Is the Model for This Application? Insider Attacks Mobile Node Denial-of-Service. Theft of Information: Passive Eavesdropping. Theft of Information: Session-Stealing (Takeover) Attack. Other Active Attacks. 9. Internet-Wide Mobility:. What Is the Model for This Application? Which Threats Are Largely the Same As Before? How Do We Protect a Mobile Node That Is Outside the? How Can Mobile Nodes Traverse the Firewall without? 10. Applying Mobile:. What Is the Model for Commercial, Mobile Service? What Is Theft-Of-Service? Denial-of-Service Revisited. Motorola's iDEN=81: A Case Study. 11. Other Applications for Mobile. Support for Other Protocols within the Mobile. Mobile Networks (as Opposed to Mobile Hosts). Mobile as a Layer-2, Tunnel-Establishment Protocol. IV. FUTURE TOPICS. 12. Mobility for IP Version 6. How Does IPv6 Differ from IPv4? Which of These Differences Is Relevant to the. Doesn't Address Autoconfiguration Eliminate the. How Does Mobile IPv6 Work? How Does a Mobile Node Determine Its Location? How Does a Mobile Node Inform Other Nodes of Its. How Are Packets Routed to and from Mobile Nodes? 13. Open Issues. TCP Performance and Mobility. RSVP and Real-Time Traffic. Service Location. 14. Summary and Final Thoughts. Mobile Summary. The Future of Mobile 307. Glossary. References. Index.

Method and apparatus for performing position-based call processing in a mobile telephone system using multiple location mapping schemes

Abstract: The mobile telephone system employs a fleet of satellites and a set of gateway ground stations arranged around the globe for handling communications to and from mobile communication subscriber units such as mobile telephones. Signals are transmitted between a subscriber unit and the nearest gateway via one or more of the satellites. The gateway system is configured to process telephone call connection requests from a mobile subscriber unit based upon the location of the subscriber unit. The location of the subscriber unit is employed, for example, to determine how telephone numbers are to be parsed and how to properly route emergency telephone calls to the nearest appropriate emergency service centers. Multiple location mapping schemes are employed to facilitate a determination of the location of a subscriber unit and to assist in routing emergency calls. In one implementation, each location with the service area of the system is mapped into a set of uniformly sized and shaped information cells. Each information cell includes pointers to data structures defining, among other things, the service providers that are permitted to process calls to or from that location and the nearest emergency services center. Each location is also mapped into at least one virtual service provider cell which includes service provider preferences and requirements for handling a call to from that location and including a unique location identifier. A specific implementation for use with the Global System for Mobile Communication is described.

System and method for providing a geographic location of a mobile telecommunications unit

Abstract: A system and a method are described herein which provide an originating telecommunications unit (28) with the geographic location of a mobile telecommunications unit (20) without actually placing a call to, or receiving a call from, the mobile unit (20). The originating unit (28) provides a service platform (24) with an authorization code and the telephone number, or other identification, of the mobile unit (20) to be located. The service platform (24) then initiates a location program which uses various geographic location methods to provide the originating unit (28) with the location of the mobile unit (20), without the user of the mobile unit (20) becoming aware that the location of the mobile unit (20) is being determined.

Method for predicting the location of a mobile station in a mobile communications network

Abstract: The approximate position of a mobile station in a cell can be predicted by measuring the signal strength between the mobile station and the base station of the cell in which it is located and the base stations of the neighboring cells. After a series of instantaneous signal strength measurements have been collected, the velocity and direction of the mobile unit can be determined. Based on the velocity and direction of the mobile unit, future locations of the mobile unit can be predicted including the projected signal strength between the mobile station and the base stations of the cell in which it is located and neighboring cells. Analyzing the projected signal strength values, the time when the mobile unit will require handover to a neighboring cell can be determined and if desired, resources in a neighboring cell can be allocated in anticipation of the mobile unit being handed over to that cell. New signal strength measurements are periodically collected and new projections are made to increase the accuracy of the estimate of when handover will occur and to what neighboring cell.

Introduction to Digital Mobile Communication

Abstract: From the Publisher: A thorough introduction to digital mobile communication technology, this book emphasizes digital transmission methods. Beginning with an introduction to what digital mobile communication is, it presents mathematical analyses of signals, mobile radio channels, digital modulation methods and more.

GSM system engineering

Abstract: From the Publisher: Take a comprehensive look at the land-based infrastructure and networking of the global system for mobile communications with this practical guide. You'll see the complete picture — starting with an introduction to the rapidly growing industry of cellular radio, progressing to the development of the digital cellular radio system, and proceeding to a study of the fundamental issues, including the GSM architecture, protocols, and time and frequency domain representation of GSM. You'll find new, detailed information in the technical explanation of the hardware and software configurations and functions of the mobile switching center (MSC), base transceiver station (BTS), operations and maintenance center (OMC), and mobile station (MS) sub-systems. GSM System Engineering is the first book in the field to discuss and explore all aspects of the important engineering issues of: • Mobility management • Subscriber management • Security management • Network maintenance In addition to this complete overview of the system, you'll learn how to use the information yourself. You'll quickly master the basics of a typical advanced (second generation) cellular system and you'll find a detailed, practical example of an international time-division multiple access (TDMA) system, which will equip you with all the tools you need to perform system engineering on cellular TDMA systems. Through this study of GSM engineering, you'll start to understand why PCS is required, and what the future of the mobile telecommunications industry will hold. Indispensible for professional engineers working in TDMA systems, GSM System Engineering will alsobe a valuable reference for all engineers in mobile communications, for instructors of courses in TDMA systems and GSM, and for undergraduate and graduate students in cellular radio. Includes 200 illustrations and 400 equations.

System and method transmitting data

Abstract: Disclosed is a system and method to transmit data to a company's data system by a mobile phone connected to a mobile communications network, and receive an acknowledgment to the same mobile phone from the company's data system. A preset target number dialed by a mobile phone is directed to an intelligent network center. The target number is decoded into data which is transmitted to a company's data system during the connection. The intelligent network center uses the caller's identifying number to check whether the caller is entitled to use the service, and to check to which information system of which company the data has been sent. The intelligent network center transmits a telecommunications network signaling the target number, caller's number and address of the company's to a voice server computer capable of identifying telephone numbers and formulate voice messages. The voice server converts the target number into data and transmits the data and the caller's number to the company's data system using a data network protocol. The company's data system stores the data in the data system and formulates a return message, which includes an acknowledgment of the received data and further a possible additional information, and transmits it to the voice server using the data network. The voice server transmits using the mobile communications network the return message either as a GSM short message or as a voice message to the mobile station which transmitted the data code, or as a pager message to a desired pager device.

Method and system for locating a mobile station within a mobile telecommunications network

Abstract: A plurality of low powered beacons are selectively placed throughout a serving mobile telecommunications network without connecting the beacons and the telecommunications network therebetween. Each of the beacons independently transmits identification data uniquely identifying itself. An application module and a mapping table correlating each identification data with the location of the corresponding beacon are associated with the serving mobile telecommunications network. As a mobile station travels within the serving mobile telecommunications network, the mobile station receives the identification data broadcast by the closest beacon located thereto. In connection with a call connection, the mobile station then transmits the received identification data to the serving mobile telecommunications network. By determining the location of the identified beacon, the mobile telecommunications network then determines that the mobile station is located approximate thereto.

Providing location-based call forwarding within a mobile telecommunications network

Abstract: Call forwarding data, including forward to numbers for a particular mobile station are correlated with a particular service area and stored at a home location register (HLR) associated with that particular mobile station. Whenever the mobile station travels into a mobile switching center (MSC) serving that particular service area, the MSC performs a location update with the HLR. A location update signal further includes data representing the identity of the service area currently serving the mobile station. Upon receiving the location update signal from the serving MSC, the HLR analyzes the received data to determine the identity of the service area currently serving the mobile station and retrieves the call forwarding data associated with that particular service area. The retrieved call forwarding data are then analyzed to determine whether the forward to numbers are located in the current service area for the mobile station and, if so, transmitted back to the serving MSC in order to provide location-based call forwarding to the roaming mobile station.

Private mobile communication system easily connecting portable or mobile radio telephone equipment to public network

Abstract: A private mobile communication system serves to support communication between mutual portable or mobile radio telephone equipment which are registered in the system, and communication between the portable or mobile radio telephone communication equipment and telephones connected to a public communication network. Portable or mobile radio telephone equipment which is not registered in the system transmits a call request to the public network through a private control channel controlling section. A radio base station of the system transfers the call request through a private channel to a private branch exchange (PBX). The PBX serves to support the call to the public network in response to the call request transmitted through the private channel.

Method and apparatus for performing position- and preference-based service selection in a mobile telephone system

Abstract: The mobile telephone system employs a fleet of satellites (214) and a set of gateway ground stations (210) arranged around the globe for handling communications to and from mobile communication units such as mobile telephones. Signals are transmitted between a subscriber (212) unit and the nearest gateway (210) via one or more of the satellites (214). The gateway is connected to a set of individuel service providers (216) such as local telephone systems. The individual service providers may be constrained for various reasons such as contractual or other legal constraints to handle communications only from subscriber units (212) located in certain geographical areas such as within only certain countries or portions of countries. For a mobile communication from a particular subscriber unit (212), the gateway selects (210) a service provider (216) capable of handling the communication. In one implementation, the selection is based upon the location of the subscriber unit and upon any references specified by the subscriber unit. In other implementations, the selection is based on other parameters such as the altitude, speed or velocity of the subscriber unit or the time of day or date upon which the communication is initiated.

Mobility management in wireless ATM networks

Abstract: Mobile ATM offers a common wired network infrastructure to support mobility of wireless terminals, independent of the wireless access protocol. In addition, it allows seamless migration to future wireless broadband services, such as wireless ATM, by enabling mobility of end-to-end ATM connections. In spite of the diversity in mobile networking technologies (e.g., cellular telephony, mobile-IP, packet data services, PCS), all of them require two fundamental mechanisms: location management and handoff. This article describes different schemes for augmenting a wired ATM network to support location management of mobile terminals and handoff protocols for rerouting a connection data path when the endpoint moves. A prototype implementation of mobile ATM integrating mobility support with ATM signaling and connection setup, is presented. It shows how mobile ATM may be used to provide mobility support to an IP terminal using non-ATM wireless access.

Data audits based on timestamp criteria in replicated data bases within digital mobile telecommunication system

Abstract: The present invention provides a method which uses a data audit function in order to maintain a consistency about a plurality of data stored as a replication data among data base nodes consisting of a mobile communication system. The method for auditing data based on timestamp criteria in replicated data bases in a digital mobile telecommunication system includes the steps of: (a) when there is a database access request, setting a time stamp about tuple accessed by the request, and managing a start, suspend, stop and resume events for a audit process; (b) managing a current status of the audit process, and information necessary for scanning each tuple; and (c) managing a request queue for the data base and CPU load. Accordingly, the present invention satisfies a system basic requirement being a real-time access in a mobile communication system including at least two data bases, maintains a consistency between two data replicated to each other, accurately controls a relationship between a mobile subscriber and a mobile terminal, and removes the incorrect data and the garbage data which may occur in a system operation, thereby effectively using the data base resource.

Transmitting/receiving unit for use with a mobile communication device

Abstract: A telephone transmitting/receiving unit comprising an electronic circuit having a function of converting a signal received by an antenna to signal to be outputted by a speaker, a function of converting a signal inputted by a microphone to a signal to be outputted by the antenna, a function of performing prescribed processing, based on a signal from an operational unit, a function of generating a signal to a display unit, a cartridge removably loaded in a slot formed in the mobile communication terminal, and an input/output unit for inputting/outputting a signal to/from the mobile communication terminal is loaded in the mobile communication terminal. The telephone transmitting/receiving unit is loaded in the mobile communication terminal, whereby mobile communication can be performed by the use of the mobile communication terminal. The telephone transmitting/receiving unit is applicable to various types of mobile communication terminals, so that comfortable mobile communication can be provided corresponding to a time, place and occasion without contracting a plurality of circuits but by contracting one circuit.

Method and apparatus for routing calls by remote control

Abstract: A mobile telephone (20) is used to control the routing of an incoming or outgoing call in a mobile communications network. A number of registration devices (24) having low energy transmitters are strategically located throughout the coverage area of the mobile communications network. Each registration device (24) is associated with a number of nearby fixed telephones (22). As the mobile terminal (20) enters the coverage area of a registration device (24), the mobile telephone (20) receives a registration signal from the registration device (24). At the onset of a call, the mobile terminal (20) displays a list of the fixed telephones (22) to a user. The user inputs a preference to the mobile terminal (20) to receive or make the incoming or outgoing call via one of the nearby fixed telephones (22) or the mobile terminal (20). The mobile terminal (20) transmits the preference to a service node (14), which sets up and appropriately routes the call. The mobile terminal (20) thus remotely controls the routing of the incoming or outgoing call.

Optimal use of logical channels within a mobile telecommunications network

Abstract: A broadcast message indicating the utilization level associated with Stand-alone Dedicated Control Channels (SDCCH) within a mobile telecommunications network serving a particular geographic area is transmitted over a broadcast channel. A plurality of mobile stations located within that particular geographic area monitoring the broadcast channel then receives the transmitted message. Thereafter, a mobile service request with a lower priority level than the indicated status level is queued by the associated mobile station and delayed until the channel utilization level rescinds to a network acceptable level.

Doppler spectrum in mobile-to-mobile communications in the presence of three-dimensional multipath scattering

Abstract: This paper provides analytical expressions for the time-autocorrelation function and the Doppler spectrum in a mobile radio channel in the presence of three-dimensional (3-D) multipath scattering. Mathematical modeling of the transmission channel is based on the assumption of wide-sense stationary (WSS) scattering. This paper deals with the case of a mobile-to-mobile radio link and derives formulas for the mobile-to-radiobase link as a special case. The Doppler spectrum examples provided are typical when assuming mobile terminal(s) located in densely built-up urban areas and simple dipole terminal antenna(s). Furthermore, the Doppler spectrum for transmission between a nongeostationary satellite and a mobile terminal located on the ground is analyzed. If different antenna patterns are to be considered and detailed knowledge is available on the multipath distribution, realistic Doppler spectra may be calculated using the approach presented in this paper.

On the cost structure of future wideband wireless access

Abstract: Wireless data services have attracted increasing attention in the last few years. Boosted by the massive use of popular Internet-based services such as email, WWW, etc., wireless wideband networks capable of supporting mobile multimedia services are being planned. An important requirement has been postulated for these wideband services-they cannot be substantially more expensive than the voice services offered today. Connection revenues cannot be expected to be proportional to the bandwidth provided. We use some simple cost models to analyze the cost structure of some proposed wireless infrastructure architectures supporting multimedia services. Both infrastructural costs and spectrum costs are included in the analysis. Results show that universal wideband coverage has an end-user connection cost that is almost directly proportional to the bandwidth provided. This is in contrast with wireline optical networks were the bandwidth cost is virtually "flat". We show further that for some hierarchical architectures, with wideband "hot-spot" service supplemented by wide-area, low data rate, coverage there exist some scenarios where a more favorable cost structure more suited for wideband multimedia applications can be achieved. The implication of the results is to use multimedia terminals and services tolerant to variable data rates and communication quality not only as proposed in a transient introduction phase, but also in the long-term perspective.

Robust beamforming for interference rejection in mobile communications

Abstract: The problem of robust beamformer design for mobile communications applications in the presence of moving co-channel sources is addressed. A generalization of the optimum beamformer based on a statistical model accounting for source movement is proposed. The new method is easily implemented and is shown to offer dramatic improvements over conventional optimum beamforming for moving sources under a variety of operating conditions.

Locatable mobile cellular telephony terminal

Abstract: The mobile cellular telephony terminal includes a radio transmitter/receiver (1) for communicating with base stations of a cellular network, measuring the Doppler velocity of the transmissions originating from the stations and accordingly operating circuits (2) for estimating the velocity of the terminal, by composition of the Doppler velocities, and updating circuits (4, 5) are provided for updating an inertial unit (10) supplying the radio circuit (1) with the position of the terminal, by comparison between a terminal velocity supplied by the unit (10) and the estimated velocity.

On disconnected browsing of distributed information

Abstract: The software and protocols associated with information browsing systems are largely designed with static access points and wired networks in mind; HTTP and the Web are a case in point. Static hosts are connected to wired, high bandwidth networks, and are capable of transmitting and receiving large amounts of data without significant delays. As such, the size and format of the data files being received by the browser/client has never been a concern. However, this causes problems when information access is desired on mobile hosts, since data transmission over a wireless network is much slower than on a wired network. Mobile computers are also relatively resource-poor, compared to their desktop counterparts. This fact is ignored by HTTP servers, and large data files are transmitted to computers that cannot properly display them. Also, mobile computers operate in constantly changing network environments. It is possible for a mobile computer to become temporarily disconnected from a network when it changes base stations or goes out of range of a base station. A mobile host may also doze off to preserve battery power and thus be disconnected. The information browsing system and protocol associated with mobile computers should thus be able to tolerate the fault of temporary disconnection. The article addresses these problems in the context of Web browsing from a mobile host. It investigates an efficient model for browsing and describes the design of a smart Web browsing application which performs transactions based on the user's available resources and manages disconnection.

Certification reports: supporting transactions in wireless systems

Abstract: The emergence of small portable computers and the advances in wireless networking have made mobile computing today a reality. Information systems and databases are among the applications that make mobile computing attractive. While the topic of querying data in wireless and mobile systems has received a lot of attention, techniques to efficiently update data in these systems while providing transaction semantics are not fully developed. We present a novel protocol that uses the broadcast facility to help mobile units do some of the work of verifying if the transactions being run by them need to be aborted. Only when the mobile unit cannot detect any conflict is the server involved in completing the verification. Of course, if the transaction can commit, the server will install the valves in the central database and notify the mobile units (again, using the broadcast channel). The protocol uses a modified version of optimistic control. We study the performance of the protocol by means of a detailed simulation.