Electrical - Electronic Engineering / Elektrik - Elektronik Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/11
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Article Citation - WoS: 1Citation - Scopus: 2Blind Recognition of Alpha-Stable Random Carrier Signals by an Eavesdropper in Random Communication Systems(Institution of Engineering and Technology, 2019) Ahmed, Areeb; Savacı, Ferit AcarInvisibility of alpha-stable (alpha -stable) noise as carrier signals, in the presence of additive white Gaussian noise (AWGN) as channel noise, is a key factor to ensure covert transmission by employing random communication systems (RCSs). This study introduces a novel blind recognition method for an eavesdropper to detect the presence of real-valued symmetric and skewed alpha -stable random carrier signals in the presence of AWGN. The introduced method is based on the proposed random carrier signal recogniser (RCSR), which consists of fractional lower-order auto-covariance block, threshold control block and the random carrier signal recognition indicator. The proposed RCSR first detects the possible presence of alpha -stable random carrier signals and then recognises the impulsiveness and skewness parameters, exploited by the transmitter and the intended receiver, to extract covertly conveyed binary information. However, the determined covert range can be adopted to perform secure transmission by RCSs. The simulation results reflect the simplicity of the proposed method as it is capable of performing effectively in real time by utilising extremely less number of observed samples.Article Numerical Investigations of Resistive Wall Wake Potentials(Institution of Engineering and Technology, 2020) Yaman, FatihThe aim of this Letter is to examine and identify longitudinal resistive wall wake potential behaviours of medium-beta long bunches and ultra-relativistic short bunches using different beam and pipe properties for particle accelerator applications. The lack of detailed analysis in current literature for the chosen set of parameters ignites this work. Since computations of wake potentials for the considered beam parameters by particle-in-cell codes are extremely difficult the author uses an analytical approach. Numerical integrations are evaluated for large domains with fine discretisations. The author observes that conductivity of beam pipe has a larger impact on medium-beta long bunches, variation of beam velocity effects wakes of short bunches more significantly, beam radii changes may have a contribution to instability for low energy short bunches. Interesting numerical results are presented and their physical explanations are discussed in this Letter.Article Citation - WoS: 5Citation - Scopus: 5Inverse System Approach To Design Alpha-Stable Noise Driven Random Communication System(Institution of Engineering and Technology, 2020) Savacı, Ferit Acar; Ahmed, AreebIn the proposed random communication system (RCS), the alpha-stable (alpha-stable) noise as a random carrier drives the transmitter which is modelled by the linear dynamical system and the skewness parameter of the random carrier encodes the binary messages. By selecting the receiver as the inverse system of the transmitter, the output of the receiver is ensured to be alpha-stable noise whose skewness parameters are then estimated to decode the binary messages. The response of a linear system to an alpha-stable process is again alpha-stable process, however, the skewness parameters of the response differs from that of the input which can only be recovered at the output of the inverse system. Hence, estimation of skewness parameter by an eavesdropper, without using the inverse system, will not reveal the true binary messages while the intended receiver truly decodes the binary messages. The proposed inverse system based RCS provides efficient performance which is shown by comparing the bit error rate of the intended receiver and an eavesdropper where the enhancement in covertness is shown by evaluating the covertness values of the proposed RCS.Article Citation - WoS: 1Citation - Scopus: 1Spatial Signature for Secure Miso-Ofdm Systems(Institution of Engineering and Technology, 2018) Özbek, Berna; Karabulut Kurt, GüneşPhysical layer security is a promising approach to establish secure communications based on the characteristics of wireless channels. A spatial signature based secure multiple-input single-output (MISO) orthogonal frequency division multiplexing (OFDM) system is proposed to disrupt the reception of a passive eavesdropper by holding two practically relevant assumptions: a limited feedback link for legitimate node and the unavailability of channel state information of eavesdropper. The proposed algorithm achieves a higher average secrecy rate than the conventional secure MISO-OFDM systems in presence of a limited feedback link.Article Citation - WoS: 9Citation - Scopus: 13Synchronisation of Alpha-Stable Levy Noisebased Random Communication System(Institution of Engineering and Technology, 2018) Ahmed, Areeb; Savacı, Ferit AcarIn this study, the pilot-assisted synchronisation method for a random communication system (RCS) has been proposed. The pilot symbol, which has alpha-stable distribution, has been used to establish synchronisation and to maintain covertness in the RCS. The introduced synchronisation block (SB) consists of fractional lower-order covariance-based correlators (FLOCCs), threshold detectors (TDs) and the synchronisation control block. To measure the performance of the proposed SB, the performance criterion, i.e. confidence ratio (CR), has been proposed. The reliability of the proposed SB can be enhanced by altering the CR and the achieved CR by using the FLOCCs and TDs in SB.Article Citation - WoS: 103Citation - Scopus: 122One-Day Ahead Wind Speed/Power Prediction Based on Polynomial Autoregressive Model(Institution of Engineering and Technology, 2017) Karakuş, Oktay; Kuruoğlu, Ercan Engin; Altınkaya, Mustafa AzizWind has been one of the popular renewable energy generation methods in the last decades. Foreknowledge of power to be generated from wind is crucial especially for planning and storing the power. It is evident in various experimental data that wind speed time series has non-linear characteristics. It has been reported in the literature that nonlinear prediction methods such as artificial neural network (ANN) and adaptive neuro fuzzy inference system (ANFIS) perform better than linear autoregressive (AR) and AR moving average models. Polynomial AR (PAR) models, despite being non-linear, are simpler to implement when compared with other non-linear AR models due to their linear-in-the-parameters property. In this study, a PAR model is used for one-day ahead wind speed prediction by using the past hourly average wind speed measurements of Ceşme and Bandon and performance comparison studies between PAR and ANN-ANFIS models are performed. In addition, wind power data which was published for Global Energy Forecasting Competition 2012 has been used to make power predictions. Despite having lower number of model parameters, PAR models outperform all other models for both of the locations in speed predictions as well as in power predictions when the prediction horizon is longer than 12 h.Article Reduced Feedback Link Design for Devicerelaying Enhanced Multiple-Input Singleoutput Orthogonal Frequency-Division Multiple Access Wireless Systems(Institution of Engineering and Technology, 2016) Özbek, BernaDevice-relaying enhanced multiple-input single-output (MISO) orthogonal frequency-division multiple access (OFDMA) systems are one of the promising and cost-effective methods to satisfy data rate requirements of future wireless networks. To implement device relaying in MISO-OFDMA systems efficiently, the channel state information belonging to all links is required at the base station. However, the feedback load increases with the number of users, device-relay candidates, antennas and subcarriers. A novel scheduling and a joint feedback link design and relay selection algorithm in device-relaying enhanced downlink MISO-OFDMA systems are proposed, while reducing the feedback load significantly without sacrificing the system performance.Article Citation - WoS: 5Citation - Scopus: 5Robust Output Tracking Control of an Unmanned Aerial Vehicle Subject To Additive State Dependent Disturbance(Institution of Engineering and Technology, 2016) Tanyer, İlker; Tatlıcıoglu, Enver; Zergeroglu, Erkan; Deniz, Meryem; Bayrak, Alper; Özdemirel, BarbarosIn this study, an asymptotic tracking controller is developed for an aircraft model subject to additive, state-dependent, non-linear disturbance-like terms. Dynamic inversion technique in conjunction with robust integral of the sign of the error term is utilised in the controller design. Compared to the previous studies, the need of acceleration measurements of the aircraft have been removed. In addition, the proposed controller design utilises only the output of aircraft dynamics. Lyapunov based analysis is applied to prove global asymptotic convergence of the tracking error signal. Numerical simulation results are presented to illustrate the performance of the proposed robust controller.Article Citation - WoS: 2Citation - Scopus: 2Enhancing Stereo Matching Performance by Colour Normalisation and Specularity Removal(Institution of Engineering and Technology, 2011) Ozan, Şükrü; Gümüştekin, ŞevketA method to enhance the performance of stereo matching is presented. The position of the specular light reflection on an object surface varies due to the change in the position of the camera, light source, object or all combined. Additionally, there may be situations exhibiting a colour shift owing to a change in the light source chromaticity or camera white balance settings. These variations cause misleading results when stereo matching algorithms are applied. In this reported work, a single-image-based statistical method is used to normalise source images. This process effectively eliminates non-saturated specularities regardless of their positions on the object. The effect of specularity removal is tested on stereo image pairs. © 2011 The Institution of Engineering and Technology.Article Citation - WoS: 14Citation - Scopus: 16Charge Feedback-Based Robust Position Tracking Control for Piezoelectric Actuators(Institution of Engineering and Technology, 2012) Salah, M. H.; McIntyre, M. L.; Dawson, Darren M.; Wagner, John R.; Tatlıcıoğlu, Envern this study, the Coleman-hysteresis model is utilised in the piezoelectric actuator (PZTA) dynamic model and a non-linear robust control strategy is then developed to actively control the displacement of the PZTA effective tip. The proposed control technique is designed based on the partial knowledge of the hysteresis model while the mass of the PZTA is assumed to be uncertain. The piezoelectric charge measurement is utilised in the controller design to reduce the effects of the hysteresis. Lyapunov-based stability analysis techniques are utilised to ensure that a desired displacement trajectory is accurately tracked. Representative numerical results are presented and discussed to demonstrate the tracking performance of several desired displacement trajectories with different frequencies and amplitudes. Finally, comparisons with a standard PID controller and a sliding mode controller were performed to examine the effectiveness of the proposed control design. © 2012 The Institution of Engineering and Technology.