Browsing by Author "Akdeniz, Bayram Cevdet."

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    Molecular communication in diffusion based channel
    (Thesis (Ph.D.)-Bogazici University. Institute for Graduate Studies in Science and Engineering, 2018., 2018.) Akdeniz, Bayram Cevdet.; Pusane, Ali Emre.
    This thesis deals with diffusion based molecular communication. Unlike conven tional communication systems, the information is encoded with molecules and these molecules are emitted by nanodevices in a diffusive environment. Since the molecules diffuse through the environment, their movement is governed by Brownian Motion, resulting in very slow and random movement that leads to excessive interference com pared to conventional communication channels. In this thesis, various modulation, equalization and coding schemes are proposed to combat with this interference issue. The main motivation for the determination of these schemes is proposing computa tionally simple and/or sparse communication methods suitable for nanodevices. All proposed methods diminish the interference at the received signal and improve the performance of the molecular communication channels compared to the other exist ing methods in the literature. In particular, pulse position modulation is adopted for molecular communication channel to diminish interference without any additional complexity and less channel information compared to other proposed modulations. A specific sparse channel code for molecular communication is also proposed by present ing its improved performance. For equalization, the received signal is equalized by analytically determining the optimum reception delay analytically that minimizes in terference and maximizes the signal power. With the same goal, optimum aperture region of the receiver is determined by deriving the joint angle-time distribution of the absorbed molecules at the receiver. Finally, network coding methods are proposed for two-way one-hop and multi-hop nanonetworks.
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    Multirobot exploration with bubble space based topological maps
    (Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2013., 2013.) Akdeniz, Bayram Cevdet.; Bozma, H. Işıl.
    This thesis is concerned with autonomous exploration with single and multirobot systems. In particular, the robots are assumed to be endowed with three-dimensional laser sensors. The exploration strategies are based on bubble space representation that has been previously proposed to represent nodes in topological maps. First, the exploration of an environment by a single robot is considered. There are two aspects to this problem: terrain mapping and determining where to go. Terrain mapping aims to infer the environmental surface shape - as this certainly would a ect the robot in determining where to go. For this, a novel approach based on bubble space representation is proposed and experimentally evaluated. For explorative navigation, the movement direction should be such that it should point the robot to unexplored territory while being accessible. A novel approach is proposed where the generation and recognition of nodes and their associated edges are achieved simultaneously with graph exploration in a topological map based on bubble space. The validity of these approaches are demonstrated by simulations and real-time experimental results.Next, the explorative navigation strategy is extended to multirobot exploration. In this case, the robots are assumed to be communicating with each other and determine their movement directions using the bubble surface information as well as their relative position information. Experimental results with real data show that the robots are able to explore unknown territories without much overlapping.