Various existing dynamic channel assignment (DCA) strategies are introduced first and a new distributed DCA algorithm is proposed in the paper. Based on local observations of the reuse cluster, the algorithm attempts ...
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Various existing dynamic channel assignment (DCA) strategies are introduced first and a new distributed DCA algorithm is proposed in the paper. Based on local observations of the reuse cluster, the algorithm attempts to minimize the reuse distance of the allocated channels and to keep channel reassignments under control. System performance of the proposed algorithm is analyzed and compared with other DCA algorithms. Simulation results show that, under certain conditions, the algorithm may approximate blocking performance of the centrally optimized Maximum Packing (MP) algorithm.
Many new database applications require very large volumes of data. Mariposa is a data base system under construction at Berkeley responding to this need. Mariposa objects can be stored over thousands of autonomous sit...
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Many new database applications require very large volumes of data. Mariposa is a data base system under construction at Berkeley responding to this need. Mariposa objects can be stored over thousands of autonomous sites and on memory hierarchies with very large capacity. This scale of the system leads to complex query execution and storage management issues, unsolvable in practice with traditional techniques. We propose an economic paradigm as the solution. A query receives a budget which it spends to obtain the answers. Each site attempts to maximize income by buying and selling storage objects, and processing queries for locally stored objects. We present the protocols which underlie the Mariposa economy.
This paper describes a distributed radio port controller architecture to provide PCS services in a micro-cellular environment. The architecture allows for rapid introduction of PCS services for mobile users using exis...
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This paper describes a distributed radio port controller architecture to provide PCS services in a micro-cellular environment. The architecture allows for rapid introduction of PCS services for mobile users using existing central office switches. Circuit and packet data services are efficiently integrated with voice services. We present the response of the vendor community to this architecture, and discuss the feasibility of its deployment. Integration of this architecture with cellular systems is explored to provide national coverage. Issues regarding seamless handovers between pedestrian and vehicular speeds in a two-tier radio system are discussed. Finally, the preliminary result of testing to validate the architecture by a simulator in a testbed is presented.
distributed control is indispensable to any personal communication service. However, distributed control makes it difficult to obtain the required frequency bandwidth considering the offered traffic and interference b...
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distributed control is indispensable to any personal communication service. However, distributed control makes it difficult to obtain the required frequency bandwidth considering the offered traffic and interference because there is no definite relationship between the base stations and the channels that they use. This paper proposes the virtual frequency reuse pattern, namely a virtual cluster size. The virtual cluster size gives the number of required control channels on a TDMA frame, assuming that once selected, the base station permanently uses the same control channel. The upper bound and the lower bound of the virtual cluster size are obtained theoretically and the practical virtual cluster size is obtained by computer simulations. Traffic channel assignment by dynamic channel allocation is designed for street microcellular systems as well. Both synchronized and asynchronized TDMA frames between base stations are discussed in this study. The optimum radio access method (TDMA/TDD or FDD) following all system conditions is reported in this paper.
High performance transaction processing in a distributed database (DDB) system can only be achieved through a high degree of locality of access, which may be attainable by appropriate data allocation. In this paper we...
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High performance transaction processing in a distributed database (DDB) system can only be achieved through a high degree of locality of access, which may be attainable by appropriate data allocation. In this paper we discuss an adaptive data allocation method for DDB systems maintaining resource allocation data, as in airline reservations and inventory control applications. According to the Fractional Data Allocation (FDA) method fractions of certain widely used resources are apportioned in the form of tokens among the nodes of the network, such that most resource allocation requests can be processed locally. When a resource allocation request cannot be processed locally, or a data fault occurs, tokens are borrowed from other network nodes through independent token transfer transactions. The initial allocation of tokens and system reconfiguration for token reallocation are based on anticipated demand. We also discuss the allocation of metadata in the DDB to make these activities possible. An abstract model, based on the count of token transfer messages, is used to specify an optimal initial data allocation, and to investigate the effect of token borrowing and reallocation policies.
To help users cope with information overload, Selective Dissemination of Information (SDI) will increasingly become an important tool in wide area information systems. In an SDI service, users post their long term que...
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To help users cope with information overload, Selective Dissemination of Information (SDI) will increasingly become an important tool in wide area information systems. In an SDI service, users post their long term queries, called profiles, at some SDI servers and continuously receive new, filtered documents. To scale up with the volume of information and the size of user population, we need a distributed SDI service with multiple servers. In this paper we first address the key problem of how to replicate and distribute profiles and documents among SDI servers. We draw a parallel between distributed SDI and the well-studied replica control problem, adapt quorum-based protocols for use in distributed SDI, and compare the performances of the different protocols. Next we address another important problem, that of efficient document delivery mechanisms. We present and evaluate a practical scheme, called profile grouping, which exploits the geographical locality of users to cut down network traffic generated by document delivery. Finally, we carry out a sensitivity analysis to determine the parameters that have critical impact on performance, and investigate strategies to cope with the scaling up of those parameters.
A new practical algorithm is proposed for dynamic channel assignment (DCA) for microcellular systems. The algorithm, called `channel information assisted reuse partitioning (CIRP),' employs information on assigned...
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A new practical algorithm is proposed for dynamic channel assignment (DCA) for microcellular systems. The algorithm, called `channel information assisted reuse partitioning (CIRP),' employs information on assigned channel number versus signal level measured at each base station. The information is utilized to assign a new channel, and is updated in each assignment process in a distributed manner. Simulation results show that CIRP successfully realizes the reuse partitioning and achieves rapid channel search and higher spectral efficiency as compared with a DCA algorithm without using the channel information. The spectral efficiency of about 2.8 approximately 3.8 times as higher as that of the fixed channel assignment (FCA) or random channel assignment (RCA) strategies is achieved by CIRP.
A computer vision approach for the extraction of feature points on 3D images of dental imprints is presented. The position of feature points are needed for the measurement of a set of parameters for automatic diagnosi...
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ISBN:
(纸本)0819416983
A computer vision approach for the extraction of feature points on 3D images of dental imprints is presented. The position of feature points are needed for the measurement of a set of parameters for automatic diagnosis of malocclusion problems in orthodontics. The system for the acquisition of the 3D profile of the imprint, the procedure for the detection of the interstices between teeth, and the approach for the identification of the type of tooth are described, as well as the algorithm for the reconstruction of the surface of each type of tooth. A new approach for the detection of feature points, called the watershed algorithm, is described in detail. The algorithm is a two-stage procedure which tracks the position of local minima at four different scales and produces a final map of the position of the minima. Experimental results of the application of the watershed algorithm on actual 3D images of dental imprints are presented for molars, premolars and canines. The segmentation approach for the analysis of the shape of incisors is also described in detail.
Suggests a systolic array implementation of fuzzy expert systems based on possibilistic evidential reasoning methodology. Evidential reasoning systems are computationally-bounded in general, and fuzzy systems match a ...
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Suggests a systolic array implementation of fuzzy expert systems based on possibilistic evidential reasoning methodology. Evidential reasoning systems are computationally-bounded in general, and fuzzy systems match a larger number of rules than in a simple symbolic reasoning system. The proposed possibilistic evidential system, which is a combination of both types of system, needs much more computation time than either of these two independently. To speed up the processing in such systems, the suggested implementation is useful.< >
In this paper we analyze the performance of a distributed Data Base (DDB) architecture for Universal Mobile Telecommunication systems (UMTS), in the presence of location updating and interrogation mobility procedures....
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In this paper we analyze the performance of a distributed Data Base (DDB) architecture for Universal Mobile Telecommunication systems (UMTS), in the presence of location updating and interrogation mobility procedures. To that end, two data locating strategies have been considered;the R and the V strategies which determine the path to be followed by a query originated by a location updating or by an interrogation procedure. Concerning the geographical scenario, several suburban, urban and city center areas with different number of mobile users (MU) registered have been considered. During the rush hours (7 a.m. - 9 a.m.), only location updating is taken into account and, the crossing rates between areas is counted. During the busy hour (11 a.m. - 12 a.m.), only interrogation procedure has been assumed, under the hypothesis of uniform distribution of calls between MUs. The result of the study is that a trade off between R and V strategy is envisaged. While for location updating R strategy performs better that V strategy, for interrogation procedure V strategy provide better performance figures than R strategy.
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