DECT is the European standard for digital cordless telecommunication. Currently, most DECT systems have been established as standard PABX islands only. However, emerging application areas for DECT networks include dat...
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DECT is the European standard for digital cordless telecommunication. Currently, most DECT systems have been established as standard PABX islands only. However, emerging application areas for DECT networks include data communication oriented mobile computing, making OSI conformance a major issue. This paper presents an approach towards the integration of mobile and fixed OSI-based networks using DECT as an example. Problems to be addressed include the registration, tracking and localization of mobile users roaming across cooperating DECT islands, in order to provide network-wide reachability and service access. We propose the ITU-T X.500 directory service as the natural solution to this problem. Using X.500 enables mapping of a DECT international portable users identity onto the user's current location. After briefly introducing the DECT and the X.500 standard, different schemes for location management using X.500 are discussed. Once the X.500 directory system is established, it can be accessed and utilized by telecommunication services and mobile applications. Examples include wireless access to an overall X.400 service as well as trading services for X.9tr based mobile distributed computing applications.
Discusses some of the problems designers face in building catalogs in large networks and relates them back to the resource discovery problem. Currently many catalogs tend to be built in an ad hoc fashion-which leads t...
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Discusses some of the problems designers face in building catalogs in large networks and relates them back to the resource discovery problem. Currently many catalogs tend to be built in an ad hoc fashion-which leads to a great variety in the quality of publicly accessible network catalogs. Furthermore, the research surrounding these catalogs tends to focus on narrow technical issues-resulting in difficult-to-use catalogs. Addresses this problem by providing a usability framework based on the library science and human computer interaction literature, and demonstrates some of those principles via an example of a prototype. Results are interesting to resource discovery tool developers in that a framework for understanding the general resource discovery problem is provided and some techniques for dealing with those problems are presented.
Recently, neural network techniques have widely used in adaptive and learning control schemes for nonlinear systems. However, generally, it costs a lot of time for learning in the case applied in control systems. Furt...
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Recently, neural network techniques have widely used in adaptive and learning control schemes for nonlinear systems. However, generally, it costs a lot of time for learning in the case applied in control systems. Furthermore, the physical meaning of neural networks constructed as a result, is not obvious. In this paper, a design method of self-tuningPID controllers is proposed, which has a fusional structure of self-tuning and neural network schemes. This method enables us to understand a physical meaning of the control parameters, and also to adjust PID gains quickly.
Authentication is a key requirement in the establishment of secure interactions between network entities. Several authentication and key establishment protocols have been proposed in recent years. Most of these protoc...
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Authentication is a key requirement in the establishment of secure interactions between network entities. Several authentication and key establishment protocols have been proposed in recent years. Most of these protocols were designed for an intra-domain environment (i.e. one where the communicating parties reside in a single domain) and then extrapolated to the inter-domain environment. In this paper, the design of inter-domain protocols is investigated. We present the different design choices that need to be carefully considered when designing inter-domain protocols in large distributedsystems. We propose three different inter-domain protocols with varying degrees of responsibility placed on the client and the trusted servers. In each case, the assumptions made in the design are explicitly stated. This helps to illustrate the rationale behind the choices made. The proposed protocols use symmetric key systems and are based on Kerberos. The arguments, rationales and designs presented in this paper are also applicable to OSF's distributed Computing Environment (DCE).
The paper presents a strategy for the composition of components to meet 'end to end' timing requirements. This is a framework based approach known as transaction integration. A framework is constructed through...
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The paper presents a strategy for the composition of components to meet 'end to end' timing requirements. This is a framework based approach known as transaction integration. A framework is constructed through the use of transactions. A transaction represents a control and data flow path across a set of component interfaces, or placeholders, that must be completed by a specific deadline. Reusable real time components are 'plugged' into each placeholder. The paper provides techniques to verify that the performance characteristics of each placeholder, and the 'end to end' deadlines associated with each transaction are met.
Vergence control enables fixation of points in visual space at different distances from the observer. It must provide not only a stable fixation, but a stable binocular fusion and a fast and accurate reaction to chang...
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Vergence control enables fixation of points in visual space at different distances from the observer. It must provide not only a stable fixation, but a stable binocular fusion and a fast and accurate reaction to changes in the environment. To obtain this kind of performance the paper focuses on the use of two dynamic quantities as inputs for the vergence control process: the temporal evolution of the degree of fusion and the rate of expansion/contraction of image patterns as a consequence of the relative motion between an object and the observer. The use of space variant image geometry is proposed and some advantages of this approach are discussed in order to demonstrate the relevance of log-polar image geometry in relation to vergence control. Three experiments are described: the first concentrates attention on the results of visual processing algorithms in an open loop situation; the other two, illustrate the behavior of the real-time vergence system in response to continuous changes of depth of a controlled target.
Quicksort is probably the most widely used sorting method in computerscience. Although it is well known that its worst-case running time is /spl Theta/(N/sup 2/), it is not clear that what kind of data will cause suc...
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Quicksort is probably the most widely used sorting method in computerscience. Although it is well known that its worst-case running time is /spl Theta/(N/sup 2/), it is not clear that what kind of data will cause such slow behavior. In this paper, we prove that a sorted array followed by one or more small elements will do. We also give examples for the pivot method of the middle element, since this is another popular pivot technique in practice. Our examples are pessimistic in the sense that they reach the worst case of Quicksort and cost the maximum number of comparisons for Quicksort, that they are extremely simple for they differ from sorted arrays only by one or two elements, and that they are well constructed so that one may tell their running time even at the first glance. Furthermore, we consider a general non-random pivoting scheme that is based on a constant number of messages about the array elements. We provide a general guideline to construct examples of running time /spl Theta/(N/sup 2/) to this general pivoting scheme.
There are many obstacles to prevent the timely development of competitive new products. Virtual Reality(VR) is a potential technology to improve this situation significantly. A synthetic 3D virtual environment(VE) can...
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