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SUNAY, Mehmet Oğuz

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Mehmet Oğuz

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SUNAY
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    ArticlePublicationOpen Access
    Client-server versus peer-to-peer
    (Boğaziçi Üniversitesi İktisadi ve İdari Bilimler Fakültesi, 2016) Özener, Başak Altan; Sunay, Mehmet Oğuz; Economics; Computer Science; ÖZENER, Başak Altan; SUNAY, Mehmet Oğuz
    This study identifies optimal transmission mechanisms for a video streaming service in a peer-to-peer network structure under different payment mechanisms: pay as you watch and pay upfront. We calculate a uniform, feasible service price using the utilities of the users and associated server profits for every possible peer-to-peer distribution tree. We prove that when the server has linear or concave costs, the client-server structure is more profitable than any peer-to-peer structure. This statement holds even when the users have maximal tolerance to indefinitely long pre-roll delays. When the server however, has convex costs, we show that the optimal network structure depends on the system parameters and there is no single distribution mechanism that provides the optimal server profit for every operating point of the network.
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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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    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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    Advantages of application-based scheduling for indoor femtocells
    (ACM, 2011) Mungan, Devin; Ferazoğlu, Gülden; Sunay, Mehmet Oğuz; Civanlar, Mehmet Reha; Kaytaz, B.; Computer Science; SUNAY, Mehmet Oğuz; CİVANLAR, Mehmet Reha; Mungan, Devin; Ferazoğlu, Gülden
    This paper presents the necessity of application-based scheduling to maintain QoS requirements of all active applications in an indoor femtocell. A novel scheduler is proposed which takes into account the quality of service (QoS) requirements of each active application as well as whether their sustainability is at risk at a given time. The scheduler aims to maintain an efficient use of the wireless radio resources and strives to achieve a user and application specific notion of fairness of service reception. Unlike current solutions, the scheduler differentiates between not only different users but also between applications of each user, and schedules data transmission amongst these applications so that QoS requirements for all applications are satisfied.
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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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    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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    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.
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    Improving the performance of wireless H.264 video broadcasting through a cross-layer design
    (IEEE, 2009) Atıcı, Çağdaş; Sunay, Mehmet Oğuz; Computer Science; SUNAY, Mehmet Oğuz; Atıcı, Çağdaş
    In a wireless video broadcasting service, number of users receiving the service and the average video quality of the received stream have to be maximized for improving the system performance. To solve this problem optimally, one may adjust parameters at the physical and the application layers in a cross-layer fashion while utilizing the characteristics of the videothat is being transmitted. In this paper, we propose a multiobjective optimized, cross-layer video broadcasting scheme for a wireless system capable of supporting a multitude of transmission data-rates using the H.264/AVC. The multi-objective, cross-layer optimization aims to find the H.264/AVC as well as the physical layer system parameters jointly to reach the optimal compromise between maximizing the average received video PSNR and minimizing the video broadcast service outage probability. Simulations conducted for the ITU Pedestrian A and Vehicular B channels show that further gains in system performance can be achieved for video broadcasting when such a cross-layer design is used.
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    A new control plane for 5G network architecture with a case study on unified handoff, mobility, and routing management
    (IEEE, 2014-11) Yazıcı, Volkan; Kozat, U.; Sunay, Mehmet Oğuz; Computer Science; SUNAY, Mehmet Oğuz; YAZICI, Volkan
    The tremendous growth in wireless Internet use is showing no signs of slowing down. Existing cellular networks are starting to be insufficient in meeting this demand, in part due to their inflexible and expensive equipment as well as complex and non-agile control plane. Software-defined networking is emerging as a natural solution for next generation cellular networks as it enables further network function virtualization opportunities and network programmability. In this article, we advocate an all-SDN network architecture with hierarchical network control capabilities to allow for different grades of performance and complexity in offering core network services and provide service differentiation for 5G systems. As a showcase of this architecture, we introduce a unified approach to mobility, handoff, and routing management and offer connectivity management as a service (CMaaS). CMaaS is offered to application developers and over-the-top service providers to provide a range of options in protecting their flows against subscriber mobility at different price levels.
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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.