Sinan KURT | TOBB University of Economics and Technology (original) (raw)

Papers by Sinan KURT

IEEE Antennas and Propagation Magazine, 2017

IEEE EUROCON 2015 - International Conference on Computer as a Tool (EUROCON), 2015

In this study we use large signal closed loop transfer function and complex quality factor to des... more In this study we use large signal closed loop transfer function and complex quality factor to design a low phase noise feedback oscillator. The method offers two major advantages. First it evaluates the closed loop transfer function, which inherently takes into account the impedance mismatch between the elements of the loop and the nonlinear behavior of the active device. These factors affect the loaded quality factor of the frequency stabilization element, as well as the location of frequency at which minimum phase noise is obtained. Secondly the method uses complex quality factor to estimate the frequency of best phase noise performance. Unlike the conventional quality factor which only uses the derivative of phase response, complex quality factor takes into account both amplitude and phase variations and provide better insight for low noise design. It has been shown experimentally that complex quality factor changes significantly for saturated loop. By using complex quality factor of saturated loop, phase noise performance can be more accurately predicted compared to the methods which do not take saturation effects into account.

Frequency Modulated Continuous Wave (FMCW) radar has wide application areas in both civil and mil... more Frequency Modulated Continuous Wave (FMCW) radar has wide application areas in both civil and military use. The range resolution is a critical concept for these FMCW radars as for the other radar types. There are theoretical restrictions in the range resolution. In addition, the non-ideal properties of the modules used in the systems negatively affects the range resolution. The transmitter leakage, non-linear frequency sweep, FM to AM distortion and measurement errors are some of the critical non-ideal properties. The problems arising from these non-ideal properties further restrict the range resolution of FMCW radars. Another important concept for the range resolution that can be obtained from FMCW radars is the signal processing method. This thesis deals with the non-ideal properties of the system modules and techniques to reduce their effects on the range resolution. Furthermore, the signal processing methods used for FMCW radar signals and the possible improvement techniques for...

2015 9th European Conference on Antennas and Propagation (EuCAP), 2015

Locally corrected Nyström (LCN) method is applied for the solution of volume integral equations ... more Locally corrected Nyström (LCN) method is applied for the solution of volume integral equations (VIEs). Unlike the conventional method of moments (MoM) procedure, LCN method does not use divergence conforming basis and testing functions to reduce the order of singularity of the integrand. Therefore LCN method needs to handle kernels with higher order singularities. For VIEs, worst singularity is due to the double derivative operator acting on free space Green's function and resulting integrals are referred to strongly singular integrals. Using finite part interpretation, we converted strongly singular integrals to regular integrals, for the solution of which conventional numerical methods can be applied. We have solved a three-dimensional scattering problem from a dielectric cube and showed the validity of the method.

For civil and military purposes FMCW radars are widely used. The theoretical background is welles... more For civil and military purposes FMCW radars are widely used. The theoretical background is wellestablished. Nevertheless, improvement of various aspects of these radars is still required. Signal processing is one of the crucial points of the system which determines the capabilities of the radar. In this study a zero crossing detector implementation, which can be efficiently used for target detection and range calculation in short range FMCW range detector is proposed. The duration between consecutive zero-crossings are used as the data instead of the number of cycles per unit time. Experimental evaluation of its performance is also given.

International Journal of Communication Systems

Packet size optimization is a critical issue in wireless sensor networks (WSNs) for improving man... more Packet size optimization is a critical issue in wireless sensor networks (WSNs) for improving many performance metrics (eg, network lifetime, delay, throughput, and reliability). In WSNs, longer packets may experience higher loss rates due to harsh channel conditions. On the other hand, shorter packets may suffer from greater overhead. Hence, the optimal packet size must be chosen to enhance various performance metrics of WSNs. To this end, many approaches have been proposed to determine the optimum packet size in WSNs. In the literature, packet size optimization studies focus on a specific application or deployment environment. However, there is no comprehensive and recent survey paper that categorizes these different approaches. To address this need, in this paper, recent studies and techniques on data packet size optimization for terrestrial WSNs, underwater WSNs, wireless underground sensor networks, and body area sensor networks are reviewed to motivate the research community to further investigate this promising research area. The main objective of this paper is to provide a better understanding of different packet size optimization approaches used in different types of sensor networks and applications as well as introduce open research issues and challenges in this area.

2016 IEEE SENSORS, 2016

In Wireless Sensor Networks (WSNs) data transmission by using the highest available power level l... more In Wireless Sensor Networks (WSNs) data transmission by using the highest available power level leads to energy wastage on certain links. Therefore, assigning the optimal transmission power for each link in a WSN is necessary to prolong the network lifetime. Transceivers of WSN nodes perform transmission power control by selecting one of the available discrete transmission power levels. As such, the power level set of a WSN transceiver is an important tool for achieving energy efficiency, yet, the power level sets are determined without considering their effects on WSN lifetime. In this study, we investigate the characteristics of the optimal transmission power level sets from WSN lifetime maximization perspective. Index Terms—wireless sensor networks, transmission power control, network lifetime, mixed integer programming, optimal power levels set.

2016 International Conference on Applied Electronics (AE), 2016

In this study a new frequency hopping scheme which relies on digital up-conversion of baseband da... more In this study a new frequency hopping scheme which relies on digital up-conversion of baseband data is proposed. Since the frequency of the local oscillator is kept constant and hopping is achieved in the baseband, the time required for the frequency jump is independent of the frequency step, allowing a narrow loop bandwidth and low noise performance for conventional phase locked loops (PLLs). Moreover the spurious signals resulting from the modulator is around-70 dBc, which is a lower value when compared to spurious signal performance of commercially available direct digital synthesis (DDS) integrated circuits. We have analyzed the error vector magnitude (EVM) and frequency hopping speed on a practical setup and have shown that quite satisfactory results can be obtained with the proposed scheme.

IEEE Transactions on Industrial Electronics, 2016

Wireless sensor networks (WSNs) are envisioned to be an important enabling technology for smart g... more Wireless sensor networks (WSNs) are envisioned to be an important enabling technology for smart grid (SG) due to the low cost, ease of deployment, and versatility of WSNs. Limited battery energy is the tightest resource constraint on WSNs. Transmission power control and data packet size optimization are powerful mechanisms for prolonging network lifetime and improving energy efficiency. Increasing transmission power will reduce the bit error rate (BER) on some links, however, utilizing the highest power level will lead to inefficient use of battery energy because on links with low path loss achieving low BER is possible without the need to use the highest power level. Utilizing a large packet size is beneficial for increasing the payload-to-overhead ratio, yet, lower packet sizes have the advantage of lower packet error rate. Furthermore, transmission power level assignment and packet size selection are interrelated. Therefore, joint optimization of transmission power level and packet size is of utmost importance in WSN lifetime maximization. In this study, we construct a detailed link layer model by employing the characteristics of Tmote Sky WSN nodes and channel characteristics based on actual measurements of SG path loss for various environments. A novel mixed integer programming framework is created by using the aforementioned link layer model for WSN lifetime maximization by joint optimization of transmission power level and data packet size. We analyzed the WSN performance by systematic exploration of the parameter space for various SG environments through the numerical solutions of the optimization model. Index Terms—Mixed integer programming (MIP), network lifetime, packet size optimization, smart grid, transmission power control, wireless sensor networks.

—Propagation models are used to abstract the actual propagation characteristics of electromagneti... more —Propagation models are used to abstract the actual propagation characteristics of electromagnetic waves utilized for conveying information in a compact form (i.e., a model with a few number of parameters). Correct modeling of propagation and path loss is of paramount importance in Wireless Sensor Network (WSN) system design and analysis. Most of the important performance metrics commonly employed for WSNs like energy dis-sipation, route optimization, reliability, and connectivity are affected by the utilized propagation model. However, in many studies on WSNs, overly simplistic and unreal-istic propagation models are utilized. One of the reasons for utilization of such impractical propagation models is the lack of awareness on experimentally available WSN specific propagation and path loss models. In this paper, necessary background information is given, succinctly, on general wireless propagation modeling and salient WSN specific constraints on path loss modeling are summarized. Building upon the provided background, an overview of the experimentally verified propagation models for WSNs are presented and quantitative comparisons of propagation models employed in WSN research under various scenarios and frequency bands are provided.

—In this study we use large signal closed loop transfer function and complex quality factor to de... more —In this study we use large signal closed loop transfer function and complex quality factor to design a low phase noise feedback oscillator. The method offers two major advantages. First it evaluates the closed loop transfer function, which inherently takes into account the impedance mismatch between the elements of the loop and the nonlinear behavior of the active device. These factors affect the loaded quality factor of the frequency stabilization element, as well as the location of frequency at which minimum phase noise is obtained. Secondly the method uses complex quality factor to estimate the frequency of best phase noise performance. Unlike the conventional quality factor which only uses the derivative of phase response, complex quality factor takes into account both amplitude and phase variations and provide better insight for low noise design. It has been shown experimentally that complex quality factor changes significantly for saturated loop. By using complex quality factor of saturated loop, phase noise performance can be more accurately predicted compared to the methods which do not take saturation effects into account.

— Locally corrected Nyström (LCN) method is applied for the solution of volume integral equations... more — Locally corrected Nyström (LCN) method is applied for the solution of volume integral equations (VIEs). Unlike the conventional method of moments (MoM) procedure, LCN method does not use divergence conforming basis and testing functions to reduce the order of singularity of the integrand. Therefore LCN method needs to handle kernels with higher order singularities. For VIEs, worst singularity is due to the double derivative operator acting on free space Green's function and resulting integrals are referred to strongly singular integrals. Using finite part interpretation, we converted strongly singular integrals to regular integrals, for the solution of which conventional numerical methods can be applied. We have solved a three-dimensional scattering problem from a dielectric cube and showed the validity of the method.

Modeling propagation in Wireless Sensor Networks (WSNs) is a vital issue in system design and ana... more Modeling propagation in Wireless Sensor Networks (WSNs) is a vital issue in system design and analysis. Energy efficiency, routing performance, Quality-of-Service, coverage and almost all aspects of WSNs are inherently related with the employed propagation model. Yet, in WSN research, even after more than a decade long continuing and widening research history, very simplistic and impractical propagation models are still utilized. In this paper, we briefly provide the necessary background on propagation modeling and concisely overview experimentally verified propagation models for WSNs.

2013 IFIP Wireless Days (WD), 2013

2014 IEEE Military Communications Conference, 2014

Network lifetime is the ultimate objective in evaluating the performance of Wireless Sensor Netwo... more Network lifetime is the ultimate objective in evaluating the performance of Wireless Sensor Networks (WSNs). To assess the network lifetime correctly for a particular WSN deployment, utilizing realistic abstractions for modeling various aspects of system components are crucial. The overwhelming majority of the studies on WSN lifetime maximization utilize well known theoretical path loss models like two-ray model, however, such models do not lead to realistic path loss results. In fact, recent studies on path loss estimation for near-ground WSN deployments reveal that the use of theoretical path loss models result in significant path loss estimation errors, therefore, empirical models developed for the specific scenario under consideration should be utilized to obtain accurate path loss characteristics. In this study, we formulate a detailed link level model of WSNs utilizing Mica2 motes and based on the link layer model, we construct a novel Mixed Integer Program (MIP) to analyze the effects of path loss models on WSN lifetime. By exploring the parameter space through numerical evaluations of the MIP model, we characterize the impact of path loss models on WSN lifetime.