Showing papers on "Mobile telephony published in 1994"

The challenges of mobile computing

Abstract: The technical challenges that mobile computing must surmount to achieve its potential are hardly trivial. Some of the challenges in designing software for mobile computing systems are quite different from those involved in the design of software for today's stationary networked systems. The authors focus on the issues pertinent to software designers without delving into the lower level details of the hardware realization of mobile computers. They look at some promising approaches under investigation and also consider their limitations. The many issues to be dealt with stem from three essential properties of mobile computing: communication, mobility, and portability. Of course, special-purpose systems may avoid some design pressures by doing without certain desirable properties. For instance portability would be less of a concern for mobile computers installed in the dashboards of cars than with hand-held mobile computers. However, the authors concentrate on the goal of large-scale, hand-held mobile computing as a way to reveal a wide assortment of issues. >

The Bayou Architecture: Support for Data Sharing Among Mobile Users

Abstract: The Bayou System is a platform of replicated, highly available, variable-consistency, mobile databases on which to build collaborative applications. This paper presents the preliminary system architecture along with the design goals that influenced it. We take a fresh, bottom-up and critical look at the requirements of mobile computing applications and carefully pull together both new and existing techniques into an overall architecture that meets these requirements. Our emphasis is on supporting application-specific conflict detection and resolution and on providing application-controlled inconsistency.

Data communications

Abstract: The author describes how events in the consumer market and the business world have recently shaped (and for the next few years will continue to shape) this area far more than technological breakthroughs. The need for real-time delivery of much higher volumes of data to meet the video and audio requirements of coming multimedia applications has driven developments in data speed and in that new realm of technology where data communications converge with other kinds of inputs. Similarly, a rising interest in increasingly mobile communications has sparked an interest in wireless communications. >

Architectural considerations for scalable, secure, mobile computing with location information

Abstract: To take full advantage of the promise of mobile/ubiquitous computing requires the availability and use of location information about the various physical objects and persons in an environment. At the same time, indiscriminant use of location information for people can result in an invasion of privacy and provides the potential for abuse by third parties. In this article we describe a suite of useful location-based applications and discuss architectural considerations for supporting them in a scalable, secure fashion. >

Dual mode subscriber terminal and a handover procedure of the dual mode subscriber terminal in a mobile telecommunication network

Abstract: A dual mode terminal (20) is provided, in which a mobile station (21) of a mobile radio system and a cordless telephone (22) are combined. This kind of terminal can have a connection with both a base station of the mobile radio system and a base station (fixed part) of the cordless telephone system. Handover in the case of this dual mode terminal implies the transfer of a call from the base station of the mobile radio system to a base station of the cordless telephone system. A call re-establishment procedure is utilized for inter-system handovers between a cordless telephone system having terminal-initiated handovers and the supporting mobile radio system having network-initiated handovers.

Structuring distributed algorithms for mobile hosts

Abstract: Distributed algorithms have hitherto been designed for networks with static hosts. A mobile host (MH) can connect to the network from different locations at different times. This paper presents an operational system model for explicitly incorporating the effects of host mobility and proposes a general principle for structuring efficient distributed algorithms in this model. This principle is used to redesign two classical algorithms for distributed mutual exclusion for the mobile environment. We then consider a problem introduced solely by host mobility viz, location management for groups of MHs, and propose the concept of group location as an efficient approach to tackle the problem. Lastly, we present a framework which enables host mobility to be decoupled from the design of a distributed algorithm per se, to varying degrees. >

Method and apparatus for supporting mobile communications in asynchronous transfer mode based networks

Abstract: Distributed call setup and rerouting are realized in a mobile-communications network. A connection tree is set up within the network, e.g., upon a mobile user accessing a base station. The connection tree comprises communication routes from a fixed point in the network, the root of the tree, to each base station within a vicinity of the base station accessed by the mobile user. When the mobile user moves from one cell to another within the connection tree, the call is rerouted to another route within the connection tree.

A method and a device for the utilization of channels in a radio communications system

Abstract: A method for optimizing the use of channels, the changing of channels and handover procedures in a mobile telecommunications system for instance, wherein parameters (C/I, P, I, L, N, ς, m) belonging to the mobile telecommunications system generate the load values (Bc, Bp, Bi, Bl, Bn, Bς, Bm) for the connections via different channels/base stations between subscribers in a public telephone network and mobile stations in the mobile telecommunications systems. Different kinds of parameters can be compared directly by means of the load values (Bc, Bp, Bi, Bl, Bn, Bς, Bm) which are combined (S1-S5) to provide a total load value (Btot2, Btot4) for each connection. A first total load value (Btot2) is generated for a connection set-up between one of the subscribers and one of the mobile stations. The total load values (Btot4, Btot5) for the connection are estimated for alternative channels/base stations and these total load values are compared with the first total load value (Btot2). The system changes to the channel/base station that has the most favourable load value (Btot4), on the basis of the comparison. The load values (Btot2, Btot4) can also be used to optimize the resources within one or more base stations, so that the sum of the load values for the connections within one or more base stations will become the most advantageous.

Application Design for Wireless Computing

Abstract: As mobile computing becomes more prevalent, systems and applications must deal with a growing disparity in resource types and availability at the user interface device. Network characteristics, display size, method of input, local storage and computing are some of the more obviously affected components. Although the challenges of effectively managing these resources are partially addressed by existing systems, their solutions are hindered by the system's lack of knowledge about the application's behavior. This, combined with the narrower domain of applications commonly used during mobile computing, suggests the need to address these concerns from the application level. This paper presents strategies for designing applications for a wireless environment, by reducing the demands placed on the wireless network. A World Wide Web client browser is used to illustrate this design.

Mobile communication terminal equipment usable for both satellite and terrestrial communications

Abstract: A mobile communication terminal equipment is mounted in a vehicle and can utilize both the satellite and terrestrial communication systems. The mobile communication terminal equipment includes a satellite transceiver and a portable set. The satellite transceiver has a satellite transmission/reception circuit. As required, the portable set is disconnected from the satellite transceiver to be carried by the user. The portable set includes a terrestrial transmission/reception circuit, a signal input/output circuit and a connection selecting switch. The connection selecting switch is automatically controlled to connect the signal input/output circuit selectively to one of the satellite and terrestrial transmission/reception circuits. When the satellite transmission/reception circuit is in connection with the signal input/output circuit, the communication through the satellite wireless communication system can be carried out. When the terrestrial transmission/reception circuit is connected to the signal input/output circuit, the communication through the terrestrial wireless communication system can be carried out.

Teleporting - Making Applications Mobile

Abstract: The rapid emergence of mobile computers as a popular, and increasingly powerful, computing tool is presenting new challenges. This subject is already being widely addressed within the computing literature. A complementary and relatively unexplored notion of mobility is one in which application interfaces, rather than the computer on which the applications run, are able to move. The Teleporting System developed at the Olivetti Research Laboratory (ORL) is a tool for experiencing such "mobile applications". It operates within the X Window System, and allows users to interact with their existing X applications at any X display within a building. The process of controlling the interface to the teleporting system is very simple. This simplicity comes from the use of an automatically maintained database of the location of equipment and people within the building. This paper describes the teleporting system, what it does, and how it is used. We outline some of the issues of making applications mobile that have arisen during its implementation.

Maintaining seamless communication between mobile users: An Architecture and Communication Protocol for picocellular networks

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

Mobisaic: An Information System for a Mobile Wireless Computing Environment

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.

Performance of DS-CDMA with imperfect power control operating over a low earth orbiting satellite link

Abstract: The analysis of both the performance and capacity of direct sequence CDMA in terrestrial cellular systems has been addressed in the technical literature. It has been suggested that CDMA be used as a multiple access method for satellite systems as well, in particular for multispot beam low Earth orbit satellites (LEOS). One is tempted to argue that since CDMA works well on terrestrial links, it will nominally work as well on satellite links. However, because there are fundamental differences in the characteristics of the two channels, such as larger time delays from the mobile to the base station and smaller multipath delay spreads on the satellite channels, the performance of CDMA on satellite links cannot always be accurately predicted from its performance on terrestrial channels. In the paper, the authors analytically derive the performance of a CDMA system which operates over a low Earth orbiting satellite channel. They incorporate such effects as imperfect power control and dual-order diversity to obtain the average probability of error of a single user. >

Future public land mobile telecommunication systems.

Abstract: In March 1992, the World Administrative Radio Conference (WARC) of the International Telecommunication Union (ITU), identified global bands 1885-2025 and 2110-2200 MHz for future public land mobile telecommunication systems (FPLMTSs), including 1980-2010 and 2170-2200 MHz for the mobile satellite component. The potential for all FPLMTS radio interfaces to be in the same band provides a strong incentive for trying to maximize the commonality between the satellite and terrestrial component of FPLMTSs. This would simplify multimode mobile equipment and also greatly increase the utility of FPLMTSs for the provision of basic telecommunication needs in underdeveloped regions of the world. Extension of integrated voice, video and data telecommunications to a person rather than a place will have a dramatic effect on everyday life, and on the organizations which currently provide these services. The author outlines some of the international standards work in this area being carried out by the International Radio Consultative Committee/International Telegraph and Telephone Consultative Committee (CCIR/CCITT), in particular that of CCIR TG8/1 (formerly IWP8/13) on FPLMTS.

Adaptive antennas for mobile communications

Abstract: Adaptive-antenna techniques offer the possibility of increasing the performance of mobile radio communication systems by maximising directional gain and enhancing the protection towards multipath conditions. The net effect of these techniques is to improve immunity to interference, extend the range of each cell and thus increase the system capacity. The paper presents the results of a two year research programme aimed at the development of practical adaptive-antenna signal-processing structures. Specifically, results obtained from a series of analysis and field trial activities undertaken with an adaptive antenna test bed and based around the DECT cordless standard are presented.

Spread-spectrum technology for commercial applications

Abstract: Only recently has our technology advanced to the point that commercial application of spread-spectrum signaling is economically feasible. This has motivated a number of companies and individuals to seek new ways to benefit from spread-spectrum techniques in commercial systems and products. In this paper, we give a very brief overview of spread spectrum signaling. We then consider applications to satellite mobile applications as well as indoor wireless applications. An overview is presented of several proposals to provide worldwide personal communications through satellite-based spread-spectrum systems, the tradeoffs to be considered, and the controversies involved. A description of a high-capacity wireless office telephone system serves to illustrate how spread-spectrum signaling may be useful in this environment. Finally, we describe a number of digital processing algorithms and devices that implement spread spectrum signaling in a cost-effective manner. >

Are “Disks in the Air” Just Pie in the Sky?

Abstract: Mobile computers and wireless networks are emerging technologies which will soon make ubiquitous computing a reality. In the wireless environment, mobile clients may often be disconnected from stationary server machines or may have only a low-bandwidth channel for sending messages to servers. This environment raises new challenges for the support of database applications for three reasons: 1) the limited storage capacities of mobile machines, 2) the inability to accurately predict the future data needs of many data-intensive applications, and 3) the need to provide clients with new or updated data values in order to ensure consistent data access. One way (perhaps the only way) to address these challenges is to provide the stationary server machines with a relatively high bandwidth channel over which to broadcast portions of the database. Wireless networks are but one compelling example of the more general class of asymmetric cornmunication environments, which also includes CATV networks and information distribution services. We have proposed a mechanism called Broadcast Disks to provide database access in asymmetric communication environments. By appropriate organization of the broadcast program, an arbitrarlly fine-grained memory hierarchy can be created. Such a hierarchy raises fundamental new issues for pre-fetching and client cache management. In this short paper we present a brief overview of asymmetric environments, our novel approach to organizing broadcast disks and some initial simulation results.

Method and system of data transmission and reception in a mobile station within a radio telecommunications system

Abstract: A method and system of transmitting and receiving data in a mobile telecommunications system which reduces power consumption in mobile stations operating within the system. Mobile stations are divided into a plurality of sleep groups and a sleep message, which is transmitted in the control channel Overhead Message Train (OMT) as a Global Action Overhead Message (GAOM) is introduced. The bits of the sleep message contain data fields which indicate to mobile stations in each of the sleep groups when to monitor the control channel on which the sleep message was transmitted.

Method for detecting position of mobile equipment by mobile communication

Abstract: PURPOSE:To simply detect the position of a mobile station with high accuracy by obtaining a relative reception level from reception level information measures usually by the mobile station or a base station and applying matching processing with relative electric field data processed to be database information together with the position in advance. CONSTITUTION:Information sent from a mobile station 11 is base station information and frequency information and measured electric field level information. The base station information and the received electric field level information are integrated into one set of information. That is, the mobile station 11 receives reception electric field level information of base stations B1-Bn and specifies a base station where the mobile station 11 is at present based on the maximum reception electric field level and reads data registered by the base station from a database 22. Then similar processing to the arithmetic operation processing method used for database processing by a position information center 18 is applied. Based on the standardized electric field level, the database 22 in the center 18 is retrieved.

Adaptive video coding for mobile wireless networks

Abstract: Wireless video transmission over a dynamic network requires adaptation to changes in bandwidth, network traffic, and channel characteristics. New computing hardware and algorithms are needed that enable low-power, flexible, adaptive, and robust video communication in hostile environments with no access to an installed communications infrastructure. The coding algorithms we are developing are based on subband decomposition using integer-coefficient filters, and adaptively deliver video at rates between 60 kbits/sec and 600 kbits/sec in accordance with the available bandwidth. Robustness in the variable length coder is obtained by using low-overhead Reed-Solomon block codes, by performing intra-frame coding only, and by using end-of-frame and end-of-subband symbols to maintain both inter- and intra-frame synchronization. >

Measured performance of data transmission over cellular telephone networks

Abstract: Recent developments in mobile communication and personal computer technology have laid a new foundation for mobile computing. Performance of the data communication system as seen by an application program is a fundamental factor when communication infrastructure at the application layer is designed. This paper provides results of performance measurements of data transmission over two different cellular telephone networks, a digital GSM-network and an analogue NMT-network. Since our emphasis is on performance as seen by application programs, we use the standard TCP/IP protocols in the measurements. The performance is measured using three basic operations: establishment of a wireless dial-up connection, exchange of request-reply messages, and bulk data transfer. The external conditions under which the measurements were carried out present a normal office environment when the field strength of the cellular link is good or fairly good.

Anonymity in a Mobile Computing Environment

Abstract: In a mobile computing environment, it is desirable to protect information about the movements and activities of mobile entities from onlookers. Solutions to this problem of providing anonymity have to be developed with the constraints of mobile computing environments in mind. In this paper, it is argued that this issue merits investigation. A brief survey of the nature of anonymity provided in proposed or existing mobile computing environments is presented. It is argued further that achieving limited but practical anonymity using standard cryptographic techniques is feasible. Example solutions are presented.

Supporting Adaptive Services in a Heterogeneous Mobile Environment

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.

Concept of a GSM-based communication system for high-speed trains

Abstract: The paper outlines the concept of a GSM-based communication system for high-speed trains up to 500 km/h. Special services for the railroad operator as specified by the UIC Radio Group are provided. Passenger communication using standard GSM terminals is supported. A possible architecture for the communication system is presented and discussed. Similarities and modifications necessary to existing GSM equipment are highlighted. >

On Travelling Incognito

Abstract: User mobility is rapidly becoming an important and popular feature in today's networks This is especially evident in wireless/cellular environments While useful and desirable, user mobility raises a number of important security-related issues and concerns One of them is the issue of tracking mobile user's movements and current whereabouts Ideally, no entity other than the user himself and a responsible authority in the user's home domain should know either the real identity or the current location of the mobile user At present, environments supporting user mobility either do not address the problem at all or base their solutions on the specific hardware capabilities of the user's personal device, eg, a cellular telephone This paper discusses a wide range of issues related to anonymity in mobile envlronments, reviews current state-of-the-art approaches and proposes several potential solutions Solutions vary in complexity, degree of protection and assumptions about the underlying environment

An unequal error protected p/spl times/8 kbit/s video transmission for DECT

Abstract: In connection with existing and emerging mobile telecommunications systems a high demand for video services for a broad field of applications such as telephony, news gathering, surveillance, road guidance systems, etc. in different environments is expected. For this, flexible and robust video source coding algorithms are required to provide moving and still image transmission with an acceptable subjective quality at variable data rates in a hostile mobile environment. The paper presents a corresponding low bit rate video codec with associated forward error correction for video transmission in the Digital European Cordless Telecommunications (DECT) system. >

Fixed cellular communications system

Abstract: A fixed cellular communications system consisting of a cellular mobile communications network (CS) that provides coverage of voice and/or data communications services to terminals located in a set of cells in any one of which there can be at least one fixed cellular terminal (4) that communicates, on one side, by radio, with one of the base stations (3) of the cellular mobile communications network (CS) and on the other side, by cable, with at least one base station (6) of a cordless communications system (WS) through control and interface means that perform the adaptation between the two systems to provide communications services to a number of cordless terminals (7). When the cellular communication system (CS) makes use of a time division multiple access technology, for example GSM, one single radio transceiver is connected to a transceiver control means to manage the radio channel allocations, so that it can simultaneously support as many communications channels as possible without there being temporal overlapping of channels.

Base station for a mobile telecommunications system

Abstract: A base station (202) for a mobile telecommunications system, adapted to communicate with mobile stations (208,210) of the system which are within a cell area, the cell area being divided into an inner area (204) in which distances to the base station (202) are within a first predetermined range, and an outer area (206) in which the distances are within a second predetermined range, the base station (202) including a first transceiver operating at a first carrier frequency and adapted for communication with mobile stations (208) in the inner area, and a second transceiver operating at a second carrier frequency adapted for communication with mobile stations in the outer area (210).