353 research outputs found
Virtual DBA: virtualizing passive optical networks to enable multi-service operation in true multi-tenant environments
No full textThis paper presents the concept of virtual dynamic bandwidth allocation (DBA), a method we propose to virtualize upstream capacity scheduling in passive optical networks (PONs), which provides multiple independent virtual network operators with the ability to precisely schedule their upstream traffic allocation. After a brief introduction on the evolution of access network sharing, we present our virtual DBA architecture, detailing its main components. We then provide a summary of the work done in this area from both theoretical and practical implementation perspectives. In this paper, we propose a novel stateless algorithm for merging multiple independent virtual bandwidth maps based on priority classes and analyze its performance in terms of efficiency of capacity allocation and latency. Through our results, we discuss the existence of a trade-off between traffic load and grant size distribution versus efficiency and latency. We find that, different from a residential single-tenant application, when PONs are used for low-latency and multi-tenant applications, the system has better overall performance if grants are allocated in small size. In addition, our analysis shows that for high-priority, strict latency services, our proposed merging algorithm presents delay performance that is independent of the traffic distribution considered
Author Correction: The fusion–fission optimization (FuFiO) algorithm (Scientific Reports, (2022), 12, 1, (12396), 10.1038/s41598-022-16498-4)
No full textThe original version of this Article contained an error in the spelling of the author Nima Darabi which was incorrectly given as Nima Darabai. The Article also contained an error in the Equation in the Analyses based on competitions on evolutionary computation (CEC) section, under the subheading ‘Computational time and complexity analyses’ where “ O(FuFiO) ” was incorrectly given as “ O(FFO)”
Techno-economics of Optical Access Network Sharing
No full textSeveral parallel trends, including the growing number of Internet reliant devices/services, increasing Internet penetration rates, and the continuing popularity of bandwidth-hungry multimedia content contribute to the exponential surge of Internet traffic. The combination of these trends could imply a considerable increase in network infrastructure investment for the telecom and broadband operators. In addition, the high cost of initial investment could escalate the market barriers to entry for the innovative service providers incapable of deploying their own network infrastructure. In this dissertation, we explore if and how enabling optical access network sharing could cultivate new network ownership and business models that simultaneously keep the end-user subscription fees low and facilitate the market entry for the smaller service providers. We aim to identify and address the technological and economic barriers of optical access network sharing. The broad scope of this dissertation concerns the inter-operator sharing of optical access networks which connect the end-users to the operators' network in the last-mile. The access segment of the communications network is recognized to be the most costly due to its deployment scale. Therefore, a reduction in cost in the access will have a multi-fold impact on the overall capital expenditure for network deployments. The dissertation focuses in particular on PONs as the most widespread type of optical access networks. The central argument of the present research is that network infrastructure/resource sharing has the potential to reduce the capital and operational expenditure of the network operators. This will allow for more competition as the market entrance cost decreases. We first address the lack of tenant operators' adequate control over the shared resources in a multi-tenant PON as a technological barrier. We provide a solution to strengthen the network operators' control over their share of the network in a multi-tenant PON. This is made possible by allowing the operators to schedule the transmission over the network using tailored algorithms to meet their requirements (e.g., latency and throughput). The dissertation argues that providing a virtual (software) instance of the DBA algorithm as opposed to the inflexible hardware implementation first enables the coexistence of various services on the PON and second, improves the overall utilization of the network capacity. While the virtualization of the DBA removes the technical barrier for the inter-operator resource sharing, it does not come with a natural incentive for the operators to share their resources with competitors. Therefore we tackle the lack of incentive for sharing excess network capacity in PON by providing monetary compensation in return for sharing. We model the multi-tenant optical access network with multiple coexisting operators as a market where they can exchange their excess capacity. We propose a sealed-bid multi-item double auction to enable capacity trading between the network operators. Through mathematical proof and market simulation/visualization, we prove that the proposed auction mechanism meets the essential requirements for an economic robust market mechanism (e.g., incentive compatibility, individual rationality, and budget balance). This provides trusted market conduct in the presence of a central authority (e.g., the public infrastructure provider) that all the operators trust
Application of dynamic Bayesian network to performance assessment of fire protection systems during domino effects
No full textThe propagation of fire in chemical plants â also known as fire domino effects - largely depends on the performance of add-on passive and active protection systems such as sprinkler systems, water deluge systems, emergency shut down and emergency blow down systems, fireproofing, and emergency response. Although such safety barriers are widely employed to prevent or delay the initiation or escalation of fire domino effects, their inclusion in the modeling and risk assessment of fire domino effects has hardly been taken into account. In the present study, the dynamic evolution of fire protection systems has been investigated qualitatively using event tree analysis. To quantify the temporal changes and their impact on the escalation of fire domino effects, a dynamic Bayesian network methodology has been developed. The application of the methodology has been demonstrated using an illustrative case study, considering a variety of fire scenarios, target installations, and firefighting systems
A Distributed Bilateral Resource Market Mechanism for Future Telecommunications Networks
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THE STRUCTURE OF AUTHORING IN NIMA YUSHIJ'S POETRY: A BAKHTINIAN READING
No full textThis thesis employs Mikhail Bakhtin’s notion of architectonics to examine the poetry of Nima Yushij, the father of “New Persian Poetry.” The architectonic structure of Nima’s poems presupposes an authorial position situated outside the whole of the work. Outsideness provides the author with the distance that is necessary for consummating the hero and all other elements inside the work’s environment in determinate spatial and temporal boundaries. As Bakhtin puts it, only in this way can the author acquire a surplus of seeing that is required for adopting a valuational stance in relation the hero and the work as a whole. To Bakhtin, the author’s valuational stance toward the hero is the essence of the aesthetic product. This valuational position vis-à-vis the other, which generates what Michael Holquist calls the “structure of authoring,” is enacted on multiple levels in Nima’s poems as the hero, and sometimes the narrator, also perform the authorial function vis-à-vis other characters inside the poem, i.e., fixing them in determinate spatial and temporal boundaries. Of course, from the author’s perspective, the hero and the narrator are also situated inside the poem and occupy specific horizons in its environment. In this sense, their authoring activity is not a precisely aesthetic activity. Nevertheless, Nima utilizes the hero and the narrator’ activity to foreground the structure of authoring inside the poem, to make its dynamics “viewable.” This is a point that I will try to elucidate fully in the course of this study.Doctor of Philosophy (PhD
History of Buddhism in Mongolia in Essay of Kensur Ngawang-Nima “Coverage of Classical Sources on History of Buddhism”
No full textThe article considers a part of the essay “Coverage of classical sources on the history of Buddhism” by the outstanding Buryat scholar Lama Kensura Ngawang-Nima, dedicated to the history of the spread of Buddhist teachings in Mongolia. Some biographical information of the author of the essay is introduced. The materials of the fragment under study are presented, on the basis of which we can say that the author divides the spread of Buddhism in Mongolia, like many researchers, into three stages. Secular and religious figures who played an important role in the spread and formation of Buddhism among the Mongols are noted in the article. It is indicated that when writing his historical treatise, Kensur Ngawang-Nima relied on the works of his famous predecessors, such as the 5th Dalai Lama Ngawang Lobsan Gyatso, Taranatha Gunga Nyingbo, Thukwan Chokyi Nyima, etc., and a part of the essay devoted to the history of Buddhism in Mongolia, based on the work “Golden Book / Altan Debter” by the famous Mongolian scholar Lama Shagdaryn Zava Damdin. The peculiarity of the historical treatise under study is that it is the only known and published work written by a Buryat in the Tibetan language in the genre of Tibetan historical literature — choichzhun
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