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CİVANLAR, Mehmet Reha

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Mehmet Reha

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CİVANLAR
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    Coverage analysis of downlink MU-MIMO cellular networks
    (IEEE, 2021-09) Arsal, Ali; Civanlar, Mehmet Reha; Uysal, Murat; Electrical & Electronics Engineering; Computer Science; CİVANLAR, Mehmet Reha; UYSAL, Murat; Arsal, Ali
    In this letter, we analyze the coverage performance of multi-user multiple-input multiple-output (MU-MIMO) downlink cellular networks. We model the locations of the base stations and mobile users using Poisson Point Processes and employ maximum ratio transmission precoding at the base station. Our analysis builds upon Prony's method to approximately calculate the coverage probability using the sum of exponentials which facilitates the computation of Laplace transform of both intra-cell and inter-cell interference. We demonstrate the accuracy of derived approximate coverage probability expressions through numerical simulations for different MU-MIMO configurations.
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    Dynamic FEC algorithms for TFRC flows
    (IEEE, 2010-12) Seferoğlu, H.; Markopoulou, A.; Kozat, Ulaş; Civanlar, Mehmet Reha; Kempf, J.; Computer Science; CİVANLAR, Mehmet Reha
    Media flows coexist with TCP-based data traffic on the Internet and are required to be TCP-friendly. The TCP protocol slowly increases its sending rate until episodes of congestion occur, and then it quickly reduces its rate to remove congestion. However, media flows can be sensitive to even brief episodes of congestion. In this paper, we are interested in protecting media flows from TCP-induced congestion while maintaining their TCP friendliness. In particular, we consider media flows carried over the TCP-Friendly Rate Control (TFRC) protocol and we design algorithms that dynamically adapt the level of forward error correction (FEC) based on the congestion state of the network. To this end, first, we investigate the loss and delay characteristics of TFRC flows in several TCP-induced congestion scenarios, and we develop novel predictors of loss events based on packet delay information. Second, we use these predictors to dynamically adapt the level of FEC protection based on the predicted level of congestion. We showthat this technique can significantly improve the overhead versus reliability trade-off compared to fixed FEC. Third, we select the FEC and original media packets within each FEC block, in a rate-distortion optimized way, and we show that this technique significantly improves media quality.
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    EditorialPublicationOpen Access
    Foreword
    (Association for Computing Machinery, Inc, 2020) Sassatell, L.; Lee J.-S., J.-S.; Civanlar, Mehmet Reha; Computer Science; CİVANLAR, Mehmet Reha
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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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    Peer-to-peer multipoint video conferencing with layered video
    (Elsevier, 2011-01) Akkuş, İ. E.; Özkasap, Ö.; Civanlar, Mehmet Reha; Computer Science; CİVANLAR, Mehmet Reha
    A peer-to-peer (P2P) architecture for multipoint video conferencing using layered video coding at the end hosts is proposed. The system primarily targets end points with low bandwidth network connections and enables them to create a multipoint video conference without any additional networking and computing resources beyond what is needed for a point-to-point conference. For P2P multipoint video conferencing applications, wide-area collaboration is significant for connecting participants from different parts around the globe to support collaborative work. In our system, peers collaborate for streaming video, and the motivation behind the use of layered video is to overcome the problem of denying video requests by peers and assure that each participant peer can view any other participant at any configuration. Layered video encoding techniques usable within this architecture are discussed. A protocol for operating the system has been developed, simulated and its performance has been analyzed. Furthermore, a multi-objective optimization approach has been developed to simultaneously minimize the number of base layer receivers and the delay experienced by the peers while maximizing the granted additional requests to support peers having multiple video input bandwidths. The use of the multi-objective optimization scheme is demonstrated through an example scenario and simulations. A prototype has also been implemented, and the system has been formally specified and verified.