177,307 research outputs found
Performance analysis of access selection and transmit diversity in multi-access networks
No full textMotivated by the 'beyond 3G' vision of radio access network integration and coordinated radio resource management, a purely analytical performance assessment is presented for a single access point integrating multiple radio accesses. Principal focus is placed on the evaluation of multi-user diversity, multi-access diversity and trunking gains. Scenarios with persistent and non-persistent data flows are investigated, concentrating on throughput and transfer time performance, respectively. A number of numerical experiments are included in order to quantify the relative contribution of the distinguished aspects to the performance gain. These experiments indicate that the exploitation of multi-user diversity with a channel-aware access selection scheme attains the most significant gains, while also the trunking gain that is due to an above-proportional performance enhancement when aggregating system-specific capacities, is noted to be significant. The assignment of multiple accesses to a given flow is demonstrated to have limited potential. Copyright 2006 ACM
Evaluation of and Improvement to Decentralized Congestion Control via Transmit Power Control with Information Exchange in ETSI GeoNetworking
No full textElectrical Engineering, Mathematics and Computer ScienceNetwork Architectures and Service
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Assessment of Dynamic Spectrum Allocation in Realistic Mobile Networks
No full textSince the advent of radio communications, radio spectrum has been increasingly getting crowded with different kinds of applications. Different radio communications systems have been developed for various purposes and multiple actors became interested in using these systems at the same time and space. Such situation inevitably led to the point when practically entire usable radio spectrum became occupied by different actors. To alleviate this problem, Dynamic Spectrum (Re)Allocation (DSA) has been proposed, which is a branch of frequency spectrum management that aims to improve spectrum usage efficiency and end-user experience by introducing more flexibility to spectrum usage. This thesis aims to provide additional insight into DSA applicability and effectiveness in a typical realistic cellular network, in intra-operator scenario, taking into account 2G and 4G radio technologies, with the aim of improving 4G performance without adverse impact to 2G. We use realistic dynamic system level simulations to assess DSA performance in the selected cellular network areas that can be classified as urban, suburban and rural. Our simulation results show that DSA is capable of improving 4G throughput without adverse impact to 2G performance in all simulated areas. Among the simulated areas, urban area benefits from DSA most, as significant throughput gains for 4G are achieved without adverse impact to 2G performance, while simulations show that spectrum refarming is clearly not an option for this type of area. However, throughput gains for 4G in urban area are limited during the busy-hours. Suburban and rural areas indicate benefits from DSA too, however the difference between DSA and spectrum refarming in these areas is diminishing. Hence, with reasonable half-rate timeslot tolerance for 2G voice calls, spectrum refarming could be an option in the simulated suburban and rural areas.Electrical EngineeringNetwork Architectures and ServicesElectrical Engineering, Mathematics and Computer Scienc
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Virtual Sectorization in Future Mobile Networks: System-Level Assessment and Optimization in a Realistic LTE Network
No full textVirtual Sectorization (ViS) is proposed as a solution to cope with the exponential growth of data traffic in mobile networks. Through the use of an Active Antenna System (AAS), two vertically separated beams (serving two distinct cells) are created within the original coverage area of a macro-cell. One of these cells, referred to as virtual cell, can be flexibly placed anywhere within the original coverage area because the large antenna array is capable of producing very narrow beams. The position of the virtual cell is done by choosing an electrical azimuth and downtilt such that the virtual cell’s footprint is as much as possible steered towards an area of relatively heavy traffic (a traffic hotspot). The key advantage of the approach is that, depending on the choice for deployment, either the spectrum or the transmit power is reused in the same geographical region, which provides an increase of traffic handling capacity. With an antenna beam directed to a specific area of high user density, more users can potentially benefit from better antenna gain and hence experience higher Signal-to-Interference-plus-Noise Ratio (SINR) values compared to the non-ViS case. However, the involved trade-offs make the deployment of ViS non-trivial. Using ViS implies a reduction of either transmit power or bandwidth for the macro-cell, and one additional interferer in the network, both of which can have a negative effect on performance if not addressed correctly. In order to cope with the complexity of these trade-offs, SON algorithms capable of dynamically share the spectrum or power resources between virtual and macro-cells, as the ones presented in this thesis work, are needed. The key functionality of these algorithms is to find an optimum configuration for the given resource sharing scheme which is able to maximize the network capacity while minimizing the aforementioned negative effects.Telecommunications and Sensing SystemsTelecommunicationsElectrical Engineering, Mathematics and Computer Scienc
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Letter from R. R. Zellick, Assistant Trust Officer, Anglo California National Bank of San Francisco, to Joseph R. Goodman, October 2, 1942
No full textLetter from R. R. Zellick, Assistant Trust Officer at The Anglo California National Bank of San Francisco, to Joseph R. Goodman, regarding property owned by Dave Tatsuno. Zellick mentions a dispute between current tenants and Tatsuno, and that Tatsuno has asked Goodman to help locate trustworthy tenants.Personal correspondence, organizational records, government documents, publications, and other papers created or collected by Joseph R. Goodman documenting the forced removal and incarceration of Japanese Americans during World War II, as well as organized resistance to incarceration. Included in the collection are records of the Japanese Young Men's Christian Association and the Japanese American Citizens' League in San Francisco, including papers of the Japanese YMCA's executive secretary Lincoln Kanai; Sakai family papers; Goodman's correspondence to and from Japanese American incarcerees, organizations opposing forced removal and incarceration of Japanese Americans, the War Relocation Authority, and others; publications, photographs, and ephemera from the Topaz Relocation Center, where Goodman taught high school; War Relocation Authority records and publications; and newspaper clippings, pamphlets, and reports about forced removal and incarceration created by various government, religious, and civic organizations, in California and nationwide
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Liftings for noncomplete probability spaces
No full textThe current state of knowledge concerning liftings for noncomplete probability spaces is discussed. This is a somewhat expanded version of the author's talk given at the 1991 Summer Conference on General Topology and Applications in Honor of Mary Ellen Rudin and Her Work.PT: S; CR: BURKE MR, IN PRESS P AM MATH S BURKE MR, 1991, ISRAEL J MATH, V73, P33 BURKE MR, 1992, ISRAEL J MATH, V79, P289 CARLSON T, THEOREM LIFTING CHRISTENSEN JPR, 1974, TOPOLOGY BOREL STRUC FREMLIN DH, 1989, HDB BOOLEAN ALGEBRAS, P877 INOESCUTULCEA A, 1966, 5TH P BERK S MATH ST, V2 IONESCUTULCEA A, 1967, CONTRIBUTIONS PROB 1, P63 IONESCUTULCEA A, 1969, TOPICS THEORY LIFTIN JECH TJ, 1978, SET THEORY JOHNSON RA, 1980, P AM MATH SOC, V80, P234 JUST W, IN PRESS T AM MATH S KUPKA J, 1983, INDIANA U MATH J, V32, P717 LOSERT V, 1983, LNM, V1080, P95 MAHARAM D, 1958, P AM MATH SOC, V9, P987 SHELAH S, 1983, ISRAEL J MATH, V45, P90 TALAGRAND M, 1982, P AM MATH SOC, V84, P379 VONNEUMANN J, 1931, CRELLES J MATH, V165, P109; NR: 18; TC: 0; J9: ANN N Y ACAD SCI; PG: 4; GA: BZ86BSource type: Electronic(1
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