Bilgisayar Mühendisliği Bölümü Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.11779/1940
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Article Citation - WoS: 5Citation - Scopus: 7Founsure 1.0: an Erasure Code Library With Efficient Repair and Update Features(Elsevier, 2021) Arslan, Şuayb Şefik; Arslan, Şefik Şuayb; 02.02. Department of Computer Engineering; 02. Faculty of Engineering; 01. MEF UniversityFounsure is an open-source software library that implements a multi-dimensional graph-based erasure coding entirely based on fast exclusive OR (XOR) logic. Its implementation utilizes compiler optimizations and multi-threading to generate the right assembly code for the given multi-core CPU architecture with vector processing capabilities. Founsure possesses important features that shall find various applications in modern data storage, communication, and networked computer systems, in which the data needs protection against device, hardware, and node failures. As data size reached unprecedented levels, these systems have become hungry for network bandwidth, computational resources, and average consumed power. To address that, the proposed library provides a three-dimensional design space that trades off the computational complexity, coding overhead, and data/node repair bandwidth to meet different requirements of modern distributed data storage and processing systems. Founsure library enables efficient encoding, decoding, repairs/rebuilds, and updates while all the required data storage and computations are distributed across the network nodes.Article Citation - WoS: 13Citation - Scopus: 22Advancements in Distributed Ledger Technology for Internet of Things(Elsevier, 2020) Jurdak, Raja; Arslan, Şefik Şuayb; Krishnamachari, Bhaskar; Jelitto, Jens; 02.02. Department of Computer Engineering; 02. Faculty of Engineering; 01. MEF UniversityInternet of Things (IoT) is paving the way for different kinds of devices to be connected and properly communicated at a mass scale. However, conventional mechanisms used to sustain security and privacy cannot be directly applied to IoT whose topology is increasingly becoming decentralized. Distributed Ledger Technologies (DLT) on the other hand comprise varying forms of decentralized data structures that provide immutability through cryptographically linking blocks of data. To be able to build reliable, autonomous and trusted IoT platforms, DLT has the potential to provide security, privacy and decentralized operation while adhering to the limitations of IoT devices. The marriage of IoT and DLT technology is not very recent. In fact many projects have been focusing on this interesting combination to address the challenges of smart cities, smart grids, internet of everything and other decentralized applications, most based on blockchain structures. In this special issue, the focus is on the new and broader technical problems associated with the DLT-based security and backend platform solutions for IoT devices and applications.Article Citation - WoS: 6Citation - Scopus: 9A Data-Assisted Reliability Model for Carrier-Assisted Cold Data Storage Systems(Elsevier, 2020) Arslan, Şuayb Şefik; Arslan, Şefik Şuayb; Göker, Turguy; Peng, James; 02.02. Department of Computer Engineering; 02. Faculty of Engineering; 01. MEF UniversityCold data storage systems are used to allow long term digital preservation for institutions’ archive. The common functionality among cold and warm/hot data storage is that the data is stored on some physical medium for read-back at a later time. However in cold storage, write and read operations are not necessarily done in the same exact geographical location. Hence, a third party assistance is typically utilized to bring together the medium and the drive. On the other hand, the reliability modeling of such a decomposed system poses few challenges that do not necessarily exist in other warm/hot storage alternatives such as fault detection and absence of the carrier, all totaling up to the data unavailability issues. In this paper, we propose a generalized non-homogenous Markov model that encompasses the aging of the carriers in order to address the requirements of today's cold data storage systems in which the data is encoded and spread across multiple nodes for the long-term data retention. We have derived useful lower/upper bounds on the overall system availability. Furthermore, the collected field data is used to estimate parameters of a Weibull distribution to accurately predict the lifetime of the carriers in an example scale-out setting.Article Citation - Scopus: 1On the Distribution of the Threshold Voltage in Multi-Level Cell Flash Memories(Elsevier, 2019) Pusane, Ali E; Arslan, Şefik Şuayb; Ashrafi, Reza A; Arslan, Şuayb Şefik; 02.02. Department of Computer Engineering; 02. Faculty of Engineering; 01. MEF UniversityIn Multi-Level Cell (MLC) memories, multiple bits of information are packed within the cell to enable higher capacity and lower cost of manufacturing compared to those of the single-level cell flash. However, because of heavy information packing, MLC memories suffer from several error sources including inter-cell interference, retention error, and random telegraph noise which make their lifetime shorter. Having so many error sources that are statistically hard to characterize makes it challenging to properly derive the underlying probability distribution of the sensed threshold voltage, which is vital for finding optimal decision rules to secure better detection performance and hence better lifetime. Although several recent works have already considered this problem, they mostly recourse to few loose assumptions that are far from being realistic. In this study, a more comprehensive/general analysis is conducted to derive the probability density function of the final sensed voltage, and through realistic simplifications, closed form expressions are presented. Extensive computer simulations corroborate the accuracy of the derived analytical expressions, and we think they shall be essential for accurately estimating the reliability and the overall lifetime of modern MLC memories.