Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Effects of Channel Errors on Coded Speech Communication in Software Defined Radio(01. Izmir Institute of Technology, 2021) Kagudde, Abbas; Atakan, BarışThis thesis investigates the performance of software defined radio in reconstruction of a coded speech signal in presence of channel errors, taking into account end to end communication. At the transmitter, the recorded author's voice is encoded using linear predictive coding algorithm, where speech parameters such as linear predicted coefficients, pitch, voicing and gain parameters, are extracted from the speech signal. These parameters are sent to linear predictive decoder to model the speech signal from its parameters. The output from source encoder is sent to channel encoder such that, the digital encoded speech data is protected using linear block codes algorithm to provide error protection to bit stream before transmission to the communication channel. Receiver's blocks or algorithms to curb multipath interference, intersymbol interference, timing offset and carrier offset are based on adaptation. Steepest descent adaptive algorithm is used to design the entire algorithms to run the software receiver. Therefore, steepest descent algorithm is implemented in down conversion, carrier recovery, clock recovery, equalization and correlation. All algorithms running the software receiver are theoretically discussed and implemented in MATLAB software. The results obtained after simulating the whole receiver block in terms of symbol error rate, mean square error and bit error rate are recorded and analyzed to investigate how channel errors affect software receiver while reconstructing a coded speech signal.Master Thesis Distance Estimation in Tabletop Molecular Communication(Izmir Institute of Technology, 2019) Uzun, Emrehan; Atakan, BarışAlthough existing communication technologies based on electrical and electromagnetic signals are applicable for a variety of applications, these technologies are insufficient in some applications. Especially, developments in nanotechnology and biotechnology require an alternative communication paradigm. Molecular communication (MC) paradigm is a promising solution needed to fill the gap in both nano- and macroscale. It is one of the oldest communication paradigm in which molecules are used as information carrier. Its mechanism provides a basis for all living organisms from unicellular bacteria to humankind to continue their existence. For instance, the information transfer among nerve cells is accomplished via MC. These kind of biological activities inspire a base for communication between nanomachines. The realization of MC occurs by sending and receiving molecules between nanomachines. The information about distance between transmitter (Tx) and receiver (Rx) is one of the critical points to enable an efficient performance in terms of clock synchronization, transmission rate, etc. in the design of MC system. However, most of the existing works on MC are based on the assumption distance is pre-known. In addition, the proposed theoretical methods are validated using an ideal simulation environment. Furthermore, there is a limited number of studies about macroscale practical applications. In this thesis, an end-to-end tabletop MC testbed is established to transmit chemical signals from a Tx to Rx. This testbed allows us to provide an estimate about the distance using molecular information received by the Rx. In the development of the estimation algorithms, the principles of molecular random walk are used. We propose three novel approaches that are called as peak time, correlation based and relative entropy based approaches to estimate the distance between Tx and Rx for a practical MC system. The performance of the proposed estimation methods is evaluated in the tabletop MC testbed. The experimental results shows that our proposed methods present a satisfactory performance in terms of estimation error and the methods can be used to develop new potential macro-scale MC applications.Master Thesis Multi-Copy Routing for Delay Tolerant Networks in Iztech(Izmir Institute of Technology, 2017) Dusenge, Babrah; Atakan, BarışDelay Tolerant Networks (DTNs) are approaches of communication that seeks to address the technical issues in intermittent networks that may lack continuous network connectivity between source and destination for message transmission. In these kinds of networks, opportunistic routing algorithms are needed, where the destination is reached through intermediate mobile nodes by use of store-carry-and-forward strategy. In this thesis, Binary Spray and Wait with Routine Awareness (BSWRA) is proposed in IZTECH. IZTECH is divided into five sub-areas (EEE department, Library, Cafeteria, Gym and Dormitory) with respect to their routine working hours. In our proposed protocol, the working time frame of IZTECH is our main interest which we refer as Routine Awareness (stipulated time frame). The Routine Awareness is added to Binary Spray and Wait (BSW) to increase chances of finding destination node. The proposed protocol improves BSW protocol on delay problem, by treating a node within a new sub-area as a source node. Furthermore, this work addresses the overhead issue in DTN protocols by revising the effect of dropping repeated messages within a sub-area. BSWRA protocol has been implemented and performance analysis has been carried out using NS2 simulator. This work examines the performance of BSWRA with popular DTN protocols (i.e. BSW, ER and PRoPHET Protocols) in terms of message delivery ratio, average end-to-end delay and overhead ratio, by observing the performance parameters of all routing protocols under varying number of nodes, message size and buffer size. The simulation results shows that generally, BSWRA protocol provides a better performance, though with 100 number of nodes and buffer size equal to100MB, ER protocol outperforms all the protocols in terms of average end-to-end delay but with the worst delivery ratio and overhead ratio.Master Thesis Event Distortion Based Clustering Algorithm for Energy Harvesting Wireless Sensor Networks(Izmir Institute of Technology, 2017) Al-Qamaji, Ali Mudheher Raghib Kafi; Atakan, Barış; Atakan, BarışWireless Sensor Network (WSN) is a set of inexpensive densely deployed wireless sensor nodes with limited functionalities and scarcity in energies, whose observations are forwarded or relayed by intermediate nodes to the Base Station (BS). In the networks with densely deployed nodes, the observations are likely to be highly correlated in the space domain. This type of correlation is referred as spatial correlation, which produces unfavorable redundant readings causing energy wasting. In this thesis, the main task is to reduce these nodes that have redundant readings by using a clustering algorithm called Event Based Clustering (EDC) algorithm. The clustering algorithm is based on exploiting the spatial correlation that is used to cluster the sensor nodes. Exploiting spatial correlation is proposed by using Vector Quantization (VQ) with respect to the distortion constraints. Furthermore, this algorithm is applied for energy harvesting sensor nodes. Also, the inessential sensor nodes that have correlated readings are reduced for improving the Energy-Efficacy (EE) with acceptable level of event signal reconstruction distortion at the sink node. After applying the EDC algorithm, the communication model is changed from single-hop model to two-hop (clustered-network) model. Hence, a theoretical framework of distortion function, i.e., accuracy level, for both single-hop and two-hop communication models is derived. Then, single-hop and two-hop communication models are compared in terms of achieved distortion level, number of alive nodes, and energy consumption for different sizes of event area. Finally, the effects of various harvested energy level on the clustered-network is studied with respect to the same terms.