Browsing by Subject "Network architecture"
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Item Open Access Analytical performance modeling of elastic optical links with aligned spectrum allocation(Elsevier BV North-Holland, 2015) Vaezi, K.; Akar, N.Abstract Elastic optical networking has recently been proposed for use in optical transport networks to cope with increasingly heterogeneous and dynamic demand patterns. In this paper, we study the blocking performance of a multi-class elastic optical link for which a demand needs to be allocated a contiguous subset of the entire spectrum. This problem is different than the well-known blocking problem in multi-class multi-server loss systems due to the contiguous allocation constraint. We first propose a non-work-conserving aligned spectrum allocation policy which is shown to outperform the conventional first fit-based work-conserving allocation policy without alignment. Subsequently, for blocking performance of an aligned elastic optical link with up to three different traffic classes, we propose a novel and systematic order reduction procedure for MMPPs (Markov Modulated Poisson Process) and use this procedure as the numerical engine to approximately obtain the blocking probabilities. The proposed numerical algorithm is validated under various system and traffic parameters and is shown to be effectively usable as an instrument to dimension elastic optical links.Item Open Access Communication efficient channel estimation over distributed networks(IEEE, 2014) Sayın, Muhammed O.; Vanlı, N. Denizcan; Göze, T.; Kozat, Süleyman SerdarWe study diffusion based channel estimation in distributed architectures suitable for various communication applications such as cognitive radios. Although the demand for distributed processing is steadily growing, these architectures require a substantial amount of communication among their nodes (or processing elements) causing significant energy consumption and increase in carbon footprint. Due to growing awareness of telecommunication industry's impact on the environment, the need to mitigate this problem is indisputable. To this end, we introduce algorithms significantly reducing the communication load between distributed nodes, which is the main cause in energy consumption, while providing outstanding performance. In this framework, after each node produces its local estimate of the communication channel, a single bit or a couple of bits of information is generated using certain random projections. This newly generated data is diffused and then used in neighboring nodes to recover the original full information, i.e., the channel estimate of the desired communication channel. We provide the complete state-space description of these algorithms and demonstrate the substantial gains through our experiments.Item Open Access Conceptual model for an ICT-enabled educational platform for collaborative design(CRC Press/Balkema, 2015) Şenyapılı, Burcu; Anumba, C.J.Almost all design related practices (architecture, architectural engineering, interior architecture/design, landscape architecture, urban design, industrial design, fashion and visual communication design) heavily depend on collaboration between colleagues from the same or different disciplines. However, practitioners who collaborate in practice, seldom have the opportunity to collaborate during design education. Having the opportunity to collaborate on educational design projects and acquiring collaboration skills and experience during design education should contribute to the quality and efficiency of future professional collaborations. Recent advancements in information and communication technologies have enabled collaboration during the process of the design studio, especially between geographically dispersed parties, but initiating and establishing such collaboration opportunities depends on the parties' singular efforts. This paper reviews previous and ongoing efforts at introducing multi-disciplinary collaborative design studios in Turkey and the USA and proposes a conceptual model for an online collaboration network that aims at promoting and facilitating collaboration among design schools and design instructors/students/ researchers. The network, establishing an educational platform for collaborative design (EPCOD) is intended to comprise a digital pool of design projects, enabling potentials of design collaboration for students from the same or different disciplines. It is designed to be accessible to all design schools all over the world, forming a specific and rich platform for design education. The role of current and emerging information and communication technologies in facilitating the proposed network-based collaboration is also discussed. © 2015 Taylor & Francis Group.Item Open Access Counteracting free riding in Peer-to-Peer networks(Elsevier BV, 2008-03) Karakaya, M.; Körpeoǧlu, I.; Ulusoy, O.The existence of a high degree of free riding is a serious threat to Peer-to-Peer (P2P) networks. In this paper, we propose a distributed framework to reduce the adverse effects of free riding on P2P networks. Our solution primarily focuses on locating free riders and taking actions against them. We propose a framework in which each peer monitors its neighbors, decides if they are free riders, and takes appropriate actions. Unlike other proposals against free riding, our framework does not require any permanent identification of peers or security infrastructures for maintaining a global reputation system. Our simulation results show that the framework can reduce the effects of free riding and can therefore increase the performance of a P2P network. © 2007 Elsevier B.V. All rights reserved.Item Open Access An efficient computation model for coarse grained reconfigurable architectures and its applications to a reconfigurable computer(IEEE, 2010-07) Atak, Oğuzhan; Atalar, AbdullahThe mapping of high level applications onto the coarse grained reconfigurable architectures (CGRA) are usually performed manually by using graphical tools or when automatic compilation is used, some restrictions are imposed to the high level code. Since high level applications do not contain parallelism explicitly, mapping the application directly to CGRA is very difficult. In this paper, we present a middle level Language for Reconfigurable Computing (LRC). LRC is similar to assembly languages of microprocessors, with the difference that parallelism can be coded in LRC. LRC is an efficient language for describing control data flow graphs. Several applications such as FIR, multirate, multichannel filtering, FFT, 2D-IDCT, Viterbi decoding, UMTS and CCSDC turbo decoding, Wimax LDPC decoding are coded in LRC and mapped to the Bilkent Reconfigurable Computer with a performance (in terms of cycle count) close to that of ASIC implementations. The applicability of the computation model to a CGRA having low cost interconnection network has been validated by using placement and routing algorithms. © 2010 IEEE.Item Open Access Energy efficient IP-connectivity with IEEE 802.11 for home M2M networks(Oxford University Press, 2017) Ozcelik, I. M.; Korpeoglu, I.; Agrawala, A.Machine-to-machine communication (M2M) technology enables large-scale device communication and networking, including home devices and appliances. A critical issue for home M2M networks is how to efficiently integrate existing home consumer devices and appliances into an IP-based wireless M2M network with least modifications. Due to its popularity and widespread use in closed spaces, Wi-Fi is a good alternative as a wireless technology to enable M2M networking for home devices. This paper addresses the energy-efficient integration of home appliances into a Wi-Fi- and IP-based home M2M network. Toward this goal, we first propose an integration architecture that requires least modifications to existing components. Then, we propose a novel long-term sleep scheduling algorithm to be applied with the existing 802.11 power save mode. The proposed scheme utilizes the multicast DNS protocol to maintain device and service availability when devices go into deep sleep mode. We prototyped our proposed architecture and algorithm to build a M2M network testbed of home appliances. We performed various experiments on this testbed to evaluate the operation and energy savings of our proposal. We also did simulation experiments for larger scale scenarios. As a result of our test-bed and simulation experiments, we observed significant energy savings compared to alternatives while also ensuring device and service availability. © The British Computer Society 2017. All rights reserved.Item Open Access Energy reduction in 3D NoCs through communication optimization(Springer Wien, 2015) Ozturk, O.; Akturk I.; Kadayif I.; Tosun, S.Network-on-Chip (NoC) architectures and three-dimensional (3D) integrated circuits have been introduced as attractive options for overcoming the barriers in interconnect scaling while increasing the number of cores. Combining these two approaches is expected to yield better performance and higher scalability. This paper explores the possibility of combining these two techniques in a heterogeneity aware fashion. Specifically, on a heterogeneous 3D NoC architecture, we explore how different types of processors can be optimally placed to minimize data access costs. Moreover, we select the optimal set of links with optimal voltage levels. The experimental results indicate significant savings in energy consumption across a wide range of values of our major simulation parameters.Item Open Access Multidimensional classification approach for defining product line engineering transition strategies(Springer, Berlin, Heidelberg, 2010) Tekinerdoğan, Bedir; Tüzün, E.; Şaykol, E.It is generally acknowledged that the transitioning process to a product line engineering approach is not trivial and as such requires a planned transition process. Different classifications of transition strategies have been proposed in the literature. It appears that these classification schemes are usually based on a single dimension. However, the adoption of a transition strategy is dependent on various criteria and very often it is not easy to characterize the required transition strategy. An appropriate characterization of the transition strategy is important for carrying out the right transition activities and steps to provide an operational product line engineering approach. In this paper, we first provide a conceptual model for defining the concepts related to transition strategies and then propose a multi-dimensional classification approach that aims to provide a more complete view on transition strategies. © 2010 Springer-Verlag Berlin Heidelberg.Item Open Access Optimization-based power and thermal management for dark silicon aware 3D chip multiprocessors using heterogeneous cache hierarchy(Elsevier BV, 2017) Asad, A.; Ozturk, O.; Fathy, M.; Jahed-Motlagh, M. R.Management of a problem recently known as “dark silicon” is a new challenge in multicore designs. Prior innovative studies have addressed the dark silicon problem in the fields of power-efficient core design. However, addressing dark silicon challenges in uncore component designs such as cache hierarchy, on-chip interconnect etc. that consume significant portion of the on-chip power consumption is largely unexplored. In this paper, for the first time, we propose an integrated approach which considers the impact of power consumption of core and uncore components simultaneously to improve multi/many-core performance in the dark silicon era. The proposed approach dynamically (1) predicts the changing program behavior on each core; (2) re-determines frequency/voltage, cache capacity and technology in each level of the cache hierarchy based on the program's scalability in order to satisfy the power and temperature constraints. In the proposed architecture, for future chip-multiprocessors (CMPs), we exploit emerging technologies such as non-volatile memories (NVMs) and 3D techniques to combat dark silicon. Also, for the first time, we propose a detailed power model which is useful for future dark silicon CMPs power modeling. Experimental results on SPEC 2000/2006 benchmarks show that the proposed method improves throughput by about 54.3% and energy-delay product by about 61% on average, respectively, in comparison with the conventional CMP architecture with homogenous cache system. (A preliminary short version of this work was presented in the 18th Euromicro Conference on Digital System Design (DSD), 2015.) © 2017 Elsevier B.V.Item Open Access A reordering-free multipath traffic engineering architecture for DiffServ-MPLS networks(IEEE, 2003-10) Akar, Nail; Hokelek, İbrahim; Atik, Muammer; Karasan, EzhanWe propose a novel traffic engineering architecture for IP networks with multiprotocol label switching (MPLS) backbones. In this architecture, two (primary and secondary) label switched paths (LSPs) are established among every pair of IP routers located at the edge of an MPLS cloud. Traffic between a source-destination pair is then split between the primary and secondary LSPs using an ABR-like explicit-rate feedback gathered from the network. Taking into consideration the packet reordering effect of packet-based load balancing schemes, we propose a novel traffic splitting mechanism that operates on a per-flow basis. We show, using a variety of scenarios, that deploying flow-based multipath traffic engineering not only provides significantly and consistently better throughput than that of a single path, but is also void of any packet reordering. © 2003 IEEE.Item Open Access Wireless ATA: A new data(2005) Özler, Serdar; Körpeoğlu, İbrahimThis paper introduces a new data transport architecture and protocol for storage that is implemented on wireless devices and that can be accessed through a short-range wireless access technology such as Bluetooth or 802.11. We call the protocol WATA (Wireless ATA), as its architecture is similar to current ATA and ATA-based technologies. In this paper, we give basic technical details of the protocol and discuss its main advantages and disadvantages over the current protocols, and talk about our decisions to implement a prototype system to see an actual implementation of the architecture.