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SUNAY, Mehmet Oğuz

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Mehmet Oğuz

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SUNAY
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Now showing 1 - 10 of 18
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    Dağıtık bir openflow kontrol birimi mimarisi
    (IEEE, 2012) Yazıcı, Volkan; Sunay, Mehmet Oğuz; Ercan, Ali Özer; Electrical & Electronics Engineering; Computer Science; ERCAN, Ali Özer; SUNAY, Mehmet Oğuz; YAZICI, Volkan
    Considering the modern internet traffic rates, the network architecture is of particular importance as the running services itself. On the other hand, due to the increasing complexity and black-box structure of the available networking hardware (switches, routers, etc.), the necessary network innovation imposed by the running services becomes infeasible in practice. The software-defined networking notion introduced to solve this problem and one of its emerging and powerful implementations, the OpenFlow protocol, advocate the idea of providing the control and data paths in separate planes. A network operating system running on this control plane, is anticipated to provide necessary measures for scalability and reliability in order to stand against the gigantic traffic pumped by the network. In this paper, we propose a distributed OpenFlow network operating system built with necessary scalability and reliability qualifications without requiring any changes to the existing OpenFlow protocol and networking equipment.
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    IEEE 802.11ac aǧların çok kullanıcılı ÇGÇÇ özelliǧi üzerine incelemeler
    (IEEE, 2016) Çakmak, Kıvanç; Sunay, Mehmet Oğuz; Ercan, Ali Özer; Electrical & Electronics Engineering; Computer Science; SUNAY, Mehmet Oğuz; ERCAN, Ali Özer; Çakmak, Kıvanç
    This paper studies the multi-user MIMO feature of IEEE 802.11ac networks that serve, along with IEEE 802.11ac nodes, also legacy IEEE 802.11n nodes. For this purpose, we develop a simulator that models the IEEE 802.11ac and IEEE 802.11n networks. Then, using a setup, we first study the tradeoff between the amount of overhead used in channel sounding and the corresponding rate of information, concluding that in this setting, channel sounding with all clients lead to better throughput. Secondly, we observe the negative impact of IEEE 802.11n nodes on the IEEE 802.11ac traffic due to the deafness problem, and analyze the performance of the usage of RTS/CTS handshake and cts2self mechanisms to mitigate this effect. We show that the regular RTS/CTS handshake mitigates the deafness problem to a certain degree. However, the cts2self mechanism achieves a better performance since no airtime is wasted to collisions with the RTS frames.
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    Hücresel sistemlerde bağlantı katmanı kaynak dağıtımı veriminin kontrolcü yoluyla artırılması
    (IEEE, 2013) Arsal, Ali; Sunay, Mehmet Oğuz; Computer Science; SUNAY, Mehmet Oğuz; Arsal, Ali
    In this work, we aim to investigate the efficiency of link layer resource allocation when a device which is called controller is used behind the base stations. By using this device, base stations are collaborating, in other words, a mobile user can be connected to more than one base station simultaneously. It is expected that this design improves the throughput and quality of service (QoS). In this study, we investigate the throughput of the system along with a performance of a video transmission. We considered the 5 cases, which are traditional case, where a user can only connected to a one base station, and 2, 4, 6, 7 base stations are collaborating. We run the simulations to observe and compare the results of the cases for mobile clients.
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    Energy sensing strategy optimization for opportunistic spectrum access
    (IEEE, 2012-06) Ercan, Ali Özer; Sunay, Mehmet Oğuz; Electrical & Electronics Engineering; Computer Science; ERCAN, Ali Özer; SUNAY, Mehmet Oğuz
    This paper introduces a correlator-based energy sensing strategy for opportunistic spectrum access in a slow, flat-fading channel. The correlator provides weighted energy accumulation in time. We assume that the noise variance is known and the primary user (PU) traffic follows a two state Markov chain with known idle and busy rates. Using Chebyshev bounds on missed detection and false alarm probabilities, we find that the optimal weighting function is an increasing function of time and its shape is dependent on the PU traffic characteristics and SNR. We show that the traditional flat-integration based energy collection method is suboptimal both in the error probability and channel utilization sense.
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    Alto sunuculu, eş görevli ağlarda dosya paylaşımı
    (IEEE, 2012) Kökten, Koray; Kırkgül, İ. Serkan; Sunay, Mehmet Oğuz; Computer Science; SUNAY, Mehmet Oğuz; Kökten, Koray; Kırkgül, İ. Serkan
    In current Internet, the most significant and the growing promotion rate of the network resources usage is due to the Peer to Peer(P2P) applications. These studies show us that the main traffic type, that Internet Service Providers (ISPs) should route, is P2P traffics. Since P2P overlay network model is networkoblivious, due to its nature, it causes inefficient network utilization, and low quality of experiences, from the perspective of the network providers and the end users respectively. Therefore, this unnecessary resource utilization increases inter-ISP traffic, and lead to serious disruption on ISPs economics. In this paper, we will implement a BitTorrent-Like simulator and Application Layer Traffic Optimization (ALTO) Server, in order to analyze and improve the performance of the overall system, by using a novel peer selection algorithms. Our results show that using this type of P2P overlay, reduces the Data Download Completion Time about and Inter-ISP Link Utilization about 50%.
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    Streaming multicast video over software-defined networks
    (IEEE, 2014) Noghani, Kyoomars Alizadeh; Sunay, Mehmet Oğuz; Computer Science; SUNAY, Mehmet Oğuz; Noghani, Kyoomars Alizadeh
    Many of the video streaming applications in today's Internet involve the distribution of content from a CDN source to a large population of interested clients. However, widespread support of IP multicast is unavailable due to technical and economical reasons, leaving the floor to application layer multicast which introduces excessive delays for the clients and increased traffic load for the network. This paper is concerned with the introduction of an SDN-based framework that allows the network controller to not only deploy IP multicast between a source and subscribers, but also control, via a simple northbound interface, the distributed set of sources where multiple-description coded (MDC) video content is available. We observe that for medium to heavy network loads, relative to the state-of-the-art, the SDN-based streaming multicast video framework increases the PSNR of the received video significantly, from a level that is practically unwatchable to one that has good quality.
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    Analysis of energy harvesting for green cognitive radio networks
    (IEEE, 2014) Ercan, Ali Özer; Sunay, Mehmet Oğuz; Pollin, S.; Electrical & Electronics Engineering; Computer Science; ERCAN, Ali Özer; SUNAY, Mehmet Oğuz
    This paper develops a Markov Chain analysis framework for an RF energy harvesting cognitive radio network where the secondary system users are furnished with finite-sized batteries. We consider a network where the only source of energy for the secondary system is the RF signals of the primary system resulting in an inter-play between energy harvesting and transmission for the secondary network. We show that an RF energy harvesting cognitive radio using todays technology is suitable for a delay-tolerant sensor network where the nodes need to transmit sensor output values very sporadically. We observe that the interplay between primary user traffic arrival and departure rates as well as probabilities of missed detection and false alarm for the secondary user detector and available battery size is of importance and that a percentile channel occupation of the primary network on its own is not a sufficient metric.
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    Femto hücre erişim noktaları için uygulama bazlı takvimleyicilerin önemi
    (IEEE, 2012) Mungan, Devin; Ferazoğlu, Gülden; Sunay, Mehmet Oğuz; Computer Science; SUNAY, Mehmet Oğuz; Mungan, Devin; Ferazoğlu, Gülden
    In this paper, it is proposed that in order to guarantee a certain level of Quality of service (QoS) for different applications in a femtocell network, it is necessary to use application-based scheduling in femtocell access points (FAP). A novel scheduler is designed which can prioritize each application considering their various QoS requirements. The scheduler aims to divide the limited wireless resources among applications in an application specific notion of fairness. Unlike current solutions, proposed scheduler differentiates between not only users but each and every application of users and allocates wireless resources considering the specific QoS requirements of different type of applications. Extensive simulation results prove that the proposed scheduler achieves tremendous results compared to the current user-based schedulers.
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    Girişim bulunan IEEE 802.11ac aǧlarda TCP sıkışıklık denetim algoritmalarinin başarımları
    (IEEE, 2016) Çakmak, Kıvanç; Sunay, Mehmet Oğuz; Ercan, Ali Özer; Karaca, M.; Electrical & Electronics Engineering; Computer Science; SUNAY, Mehmet Oğuz; ERCAN, Ali Özer; Çakmak, Kıvanç
    In order to meet the incremental requirements from clients, fifth generation Wireless Local Area Network(WLAN) protocol IEEE 802.11ac provides a lot more throughput than his predecessors. However, in all distributed channel access 802.11 protocols, probability of packet loss increases with respect to number of available stations; consecutive packet losses in link layer activates congestion control mechanism of TCP which decreases throughput. In this work, we investigated the performance of congestion control algorithms of TCP protocol when interference available wireless medium is used in between the IEEE 802.11ac capable devices. As a benchmark, we repeated the experiments with UDP protocol which does not have reliable connection and congestion control mechanism. According to our experiments, we observed that UDP provides more throughput than all other TCP congestion control algorithms. When we compare TCP congestion control algorithms by themselves, we observed that the algorithms which does not decrease congestion window size too much during interference and have more aggressive increment of congestion window -such as Cubic and Illinois, Scalable have better performance in terms of throughput and standard deviation.
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    Experimental investigation of the impact on TCP traffic by hidden video-tagged UDP traffic
    (IEEE, 2017) Çakmak, Kıvanç; Sunay, Mehmet Oğuz; Ercan, Ali Özer; İlhan, C.; Çakar, C.; Sofuoğlu, Ç.; Electrical & Electronics Engineering; Computer Science; SUNAY, Mehmet Oğuz; ERCAN, Ali Özer; Çakmak, Kıvanç
    This paper investigates the impact of video-tagged UDP traffic on best-effort TCP traffic in an experimental setup with a novel observation approach. Our setup consists of three 802.11ac nodes in a hidden node topology, where a 20Mbps UDP and a best effort TCP traffic flow from the edge (hidden) nodes to the center node. We observe that, even though the RTS/CTS mechanism is enabled, when UDP and TCP traffic flow simultaneously, video-tagged UDP traffic causes the besteffort TCP traffic throughput to drop by 50%. An analysis of the captured and synchronized packet data reveals for the first time that, the following event is a surprising major contributor to the throughput degradation. Since the TCP and UDP sources are hidden from each other, an RTS packet of the UDP source may collide with the CTS reply to the TCP source. This in turn may result in many collisions between the subsequent RTS packets of the UDP source and the data packet of the TCP source. This paper experimentally shows that this event is particularly commonplace for video-tagged traffic, having smaller back-off duration, severely impacting the cross-traffic.