1,720,999 research outputs found
Dynamic Spectrum Sharing Optimization and Post-optimization Analysis with Multiple Operators in Cellular Networks
No full textDynamic spectrum sharing aims to provide secondary access to under-utilised spectrum in cellular networks. The main aim of the paper is twofold. Firstly, secondary operator aims to borrow spectrum bandwidths under the assumption that more spectrum resources exist considering a merchant mode. Two optimization models are proposed using stochastic and optimization models in which the secondary operator (i) spends the minimal cost to achieve the target grade of service assuming unrestricted budget or (ii) gains the maximal profit to achieve the target grade of service assuming restricted budget. Results obtained from each model are then compared with results derived from algorithms in which spectrum borrowings are random. Comparisons showed that the gain in the results obtained from our proposed stochastic-optimization framework is significantly higher than heuristic counterparts. Secondly, post-optimization performance analysis of the operators in the form of blocking probability in various scenarios is investigated to determine the probable performance gain and degradation of the secondary and primary operators respectively. We mathematically model the sharing agreement scenario and derive the closed form solution of blocking probabilities for each operator. Results show how the secondary operator perform in terms of blocking probability under various offered loads and sharing capacit
Spectrum Sharing Optimization and Analysis in Cellular Networks under Target Performance and Budget Restriction
Full text linkDynamic Spectrum Sharing (DSS) aims to provide opportunistic access to under-utilised spectrum in cellular networks for secondary network operators. In this paper we propose an algorithm using stochastic and optimisation models to borrow spectrum bandwidths under the assumption that more resources exist for secondary access than the secondary network demand by considering a merchant mode. The main aim of the paper is to address the problem of spectrum borrowing in DSS environments, where a secondary network operator aims to borrow the required spectrum from multiple primary network operators to achieve a maximum profit under specific grade of service (GoS) and budget restriction. We assume that the primary network operators offer spectrum access opportunities with variable number of channels (contiguous and/or non-contiguous) at variable prices. Results obtained are then compared with results derived from an algorithm in which spectrum borrowing are random. Comparisons showed that the gain in the results obtained from our proposed stochastic-optimisation framework is significantly higher than random counterpart
Generalised Radio Resource Sharing Framework for Heterogeneous Radio Networks
Full text linkRecent years have seen a significant interest in quantitative measurements of licensed
and unlicensed spectrum use. Several research groups, companies and regulatory bodies
have conducted studies of varying times and locations with the aim to capture the over-
all utilisation rate of spectrum. The studies have shown that large amount of allocated
spectrum are under-utilised, and create the so called \spectrum holes", resulting in a
waste of valuable frequency resources. In order to satisfy the requirements of increased
demands of spectrum resources and to improve spectrum utilisation, dynamic spectrum
sharing (DSS) is proposed in the literature along with cognitive radio networks (CRNs).
DSS and CRNs have been studied from many perspectives, for example spectrum sensing
to identify the idle channels has been under the microscope to improve detection proba-
bility. As well as spectrum sensing, the DSS performance analysis remains an important
topic moving towards better spectrum utilisation to meet the exponential growth of
traffi�c demand. In this dissertation we have studied both techniques to achieve different
objectives such as enhancing the probability of detection and spectrum utilisation.
In order to improve spectrum sensing decisions we have proposed a cooperative spec-
trum sensing scheme which takes the propagation conditions into consideration. The
proposed location aware scheme shows an improved performance over conventional hard
combination scheme, highlighting the requirements of location awareness in cognitive
radio networks (CRNs).
Due to the exponentially growing wireless applications and services, traffi�c demand is
increasing rapidly. To cope with such growth wireless network operators seek radio
resource cooperation strategies for their users with the highest possible grade of service
(GoS). However, it is diffi�cult to fathom the potential benefits of such cooperation, thus
we propose a set of analytical models for DSS to analyse the blocking probability gain and
degradation for operators. The thesis focuses on examining the performance gains that
DSS can entail, in different scenarios. A number of dynamic spectrum sharing scenarios
are proposed. The proposed models focus on measuring the blocking probability of
secondary network operators as a trade-o� with a marginal increase of the blocking
probability of a primary network in return of monetary rewards. We derived the global
balance equation and an explicit expression of the blocking probability for each model.
The robustness of the proposed analytical models is evaluated under different scenarios
by considering varying tra�c intensities, different network sizes and adding reserved
resources (or pooled capacity). The results show that the blocking probabilities can
be reduced significantly with the proposed analytical DSS models in comparison to the
existing local spectrum access schemes.
In addition to the sharing models, we further assume that the secondary operator aims
to borrow spectrum bandwidths from primary operators when more spectrum resources
available for borrowing than the actual demand considering a merchant mode. Two
optimisation models are proposed using stochastic optimisation models in which the secondary operator (i) spends the minimum amount of money to achieve the target
GoS assuming an unrestricted budget or (ii) gains the maximum amount of pro�t to
achieve the target GoS assuming restricted budget. Results obtained from each model
are then compared with results derived from algorithms in which spectrum borrowings
were random. Comparisons showed that the gain in the results obtained from our pro-
posed stochastic optimisation model is significantly higher than heuristic counterparts.
A post-optimisation performance analysis of the operators in the form of analysis of
blocking probability in various scenarios is investigated to determine the probable per-
formance gain and degradation of the secondary and primary operators respectively.
We mathematically model the sharing agreement scenario and derive the closed form
solution of blocking probabilities for each operator. Results show how the secondary
and primary operators perform in terms of blocking probability under various offered
loads and sharing capacity.
The simulation results demonstrate that at most trading windows, the proposed opti-
mal algorithms outperforms their heuristic counterparts. When we consider 80 cells,
the proposed pro�t maximisation algorithm results in 33.3% gain in net pro�t to the
secondary operators as well as facilitating 2.35% more resources than the heuristic ap-
proach. In addition, the cost minimisation algorithm results in 46.34% gain over the
heuristic algorithm when considering the same number of cells (80)
A systematic review on WebRTC for potential applications and challenges beyond audio video streaming
Full text linkVideo conferencing and live streaming are being used in various industries, such as healthcare, gaming, telecommunication, manufacturing and others. As technology progresses, the need for real-time data transmission with minimal latency has increased. Web Real-Time Communication () addresses this need effectively. WebRTC is a technology designed to provide real-time communication through web and mobile browsers. Its low latency and P2P communication capabilities make it a convenient technology for secure, efficient communication in real-time applications. This paper reviews the key features of WebRTC, discusses its strengths and weaknesses and investigates a detailed analysis of 83 existing studies. Moreover, It evaluates all use cases that can be adopted by WebRTC by examining their descriptions, problem statements, and research gaps based on literature to date. Finally, It highlights the open research directions for the emerging technologies and enhancements of WebRTC. to identify their potential applications
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
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