Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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2010 - 20122

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Subject: search.filters.subject.Real-time control

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  • Master Thesis
    Quality-Adaptive Media Streaming
    (Izmir Institute of Technology, 2012) Tos, Uras; Ayav, Tolga
    In this study, an adaptive method for maximizing network bandwidth utilization for real-time media streaming applications is presented. The proposed method implements a rate control approach over the transport protocol RTP. RTP is coupled with an existing multimedia codec, H.264. A controller that keeps the RTP packet loss fraction at a predefined reference point is implemented. During the course of the stream transmission, the information about the network state is generated by the RTP/RTCP and sent to the server by the clients. Packet loss fraction parameter is fed into the controller. Controlling the multimedia codec bitrate directly affects the packet transmission rate, therefore RTP packet transmission rate is also controlled. Two control approaches are proposed. Firstly, a PID controller is introduced. This PID controller is designed without any self adaptation and manually tuned to maximize all of the available bandwidth. Secondly, a model reference adaptive controller (MRAC) is proposed. This MRAC controller constantly adjusts its parameters according to a reference model. The output of the TCP Friendly Rate Control Algorithm (TFRC) is used as the model to keep the MRAC controller friendly towards other flows flows at a level that the application requires. Simulations are provided to demonstrate the operation of the proposed methods. In the simulations, a content streaming scenario is run against background traffic for the available bandwidth in a bottleneck network configuration.
  • Master Thesis
    Utilization of Timed Automata as a Verification Tool for Real-Time Security Protocols
    (Izmir Institute of Technology, 2010) Külahçıoğlu, Burcu; Aytaç, İsmail Sıtkı
    Timed Automata is an extension to the automata-theoretic approach to the modeling of real time systems that introduces time into the classical automata. Since it has been first proposed by Alur and Dill in the early nineties, it has become an important research area and been widely studied in both the context of formal languages and modeling and verification of real time systems. Timed automata use dense time modeling, allowing efficient model checking of time-sensitive systems whose correct functioning depend on the timing properties. One of these application areas is the verification of security protocols. This thesis aims to study the timed automata model and utilize it as a verification tool for security protocols. As a case study, the Neuman-Stubblebine Repeated Authentication Protocol is modeled and verified employing the time-sensitive properties in the model. The flaws of the protocol are analyzed and it is commented on the benefits and challenges of the model.