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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
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Publication Metadata only A physical channel model for nanoscale neuro-spike communications(IEEE-Inst Electrical Electronics Engineers Inc, 2013) Balevi, eren; Department of Electrical and Electronics Engineering; Akan, Özgür Barış; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 6647Nanoscale communications is an appealing domain in nanotechnology. Novel nanoscale communications techniques are currently being devised inspired by some naturally existing phenomena such as the molecular communications governing cellular signaling mechanisms. Among these, neuro-spike communications, which governs the communications between neurons, is a vastly unexplored area. The ultimate goal of this paper is to accurately investigate nanoscale neuro-spike communications characteristics through the development of a realistic physical channel model between two neurons. The neuro-spike communications channel is analyzed based on the probability of error and delay in spike detection at the output. The derived communication theoretical channel model may help designing novel artificial nanoscale communications methods for the realization of future practical nanonetworks, which are the interconnections of nanomachines.Publication Metadata only Analysis and optimization of duty-cycle in preamble-based random access networks(Springer, 2013) Fischione, C.; Park, P.; Department of Electrical and Electronics Engineering; Ergen, Sinem Çöleri; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 7211Duty-cycling has been proposed as an effective mechanism for reducing the energy consumption in wireless sensor networks (WSNs). Asynchronous duty-cycle protocols where the receiver wakes up periodically to check whether there is a transmission and the sender transmits preambles to check if the receiver is awake are widely used in WSNs due to the elimination of complex control mechanisms for topology discovery and synchronization. However, the intrinsic simplicity of the asynchronous mechanism has the drawback of smaller energy saving potential that requires the optimization of the duty cycle parameters. In this paper, we propose a novel method for the optimization of the duty-cycle parameters in preamble-based random access networks based on the accurate modeling of delay, reliability and energy consumption as a function of listen time, sleep time, traffic rate and medium access control (MAC) protocol parameters. The challenges for modeling are the random access MAC and the sleep policy of the receivers, which make it impossible to determine the exact time of data packet transmissions, and thus difficult to investigate the performance indicators given by the delay, reliability and energy consumption to successfully receive packets. An analysis of these indicators is developed as a function of the relevant parameters of the network and it is used in the minimization of the energy consumption subject to delay and reliability requirements. The optimization provides significant reduction of the energy consumption compared to the previously proposed protocols in the literature.Publication Metadata only EASER: energy aware scalable and reactive replication protocol for MANETs(Springer, 2016) N/A; N/A; Department of Computer Engineering; Department of Computer Engineering; Azar, Saeed Nourizadeh; Karaağaçlı, Kaan; Özkasap, Öznur; PhD Student; Undergraduate Student; Faculty Member; Department of Computer Engineering; N/A; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; N/A; N/A; 113507Mobile ad hoc networks (MANETs) depend on the nodes' collaboration to communicate and transfer data, and scaling the network size up greatly increases the energy needed to transfer data among far away nodes. To preserve nodes' energy and increase the network lifetime, data replication protocols have been proposed, which mainly increase data availability by creating nearby local copies of required data. In this work, first we provide a review of energy aware data replication protocols in MANETs. Then, by considering nodes' energy consumption, we propose EASER: Energy Aware Scalable and rEactive data Replication protocol. Our simulation results and comparison with SCALAR, energy aware ZRP and AODV protocols show that EASER provides improved network lifetime and data accessibility as the network size scales up with considering node energy levels.Publication Metadata only Optimal power control, rate adaptation, and scheduling for uwb-based intravehicular wireless sensor networks(Institute of Electrical and Electronics Engineers (IEEE), 2013) N/A; Department of Electrical and Electronics Engineering; Şadi, Yalçın; Ergen, Sinem Çöleri; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 7211The intravehicular wireless sensor network (IVWSN) is a promising new research area that can provide part cost, assembly, maintenance savings, and fuel efficiency through the elimination of the wires and enables new sensor technologies to be integrated into vehicles, which would otherwise be impossible using wired means such as Intelligent Tire. The close interaction of communication with control systems, strict reliability, energy efficiency, and delay requirements in such a harsh environment that contains a large number of reflectors that operate at extreme temperatures are distinguishing properties of this network. In this paper, we investigate optimal power control, rate adaptation, and scheduling for an ultrawideband-based IVWSN for one-electronic-control-unit (ECU) and multiple-ECU cases. For the one-ECU case, we show that the optimal rate and power allocation is independent of the optimal scheduling algorithm. We prove the NP-hardness of the scheduling problem and formulate the optimal solution as a mixed-integer linear programming (MILP) problem. We then propose a 2-approximation algorithm, which is the smallest period into the shortest subframe first (SSF) algorithm. For the multiple-ECU case, where the concurrent transmission of links is possible, we formulate the optimal power control as a geometric-programming problem and optimal scheduling problem as an MILP problem where the number of variables is exponential in the number of links. We then propose a heuristic algorithm-the maximum-utility-based concurrency allowance algorithm-based on the idea of significantly improving the performance of the SSF algorithm in the existence of multiple ECUs by determining the sets of maximum utility.Publication Metadata only An alternating service model with self-similar input to provide guaranteed QoS in wireless internet(IEEE, 2006) Iftikhar, Mohsin; Landfeldt, Bjorn; Department of Mathematics; Çağlar, Mine; Faculty Member; Department of Mathematics; College of Sciences; 105131Over the past few years, we have witnessed a growing popularity of new wireless architectures such as 3G, WiFi and Wi-Max due to the increase in demand for wireless Internet access. The all-IP based future mobile and wireless network model is expected to be the most dominant architecture for QoS provisioning in next-generation wireless networks, mainly due to its scalability and capability of inter-working heterogeneous wireless access networks. Recently, the rapid growth of various wireless infrastructures and the interesting mixture of wireless traffic generated by large number of devices (PDAs, Laptops and cell-phones) have diverted the attention of wireless research community towards understanding the nature of traffic carried by different wireless architectures. A series of recent studies on GPRS aggregated traffic, WAP and Web traffic has proven that wireless traffic exhibits strong long-range dependency. However, much of the current understanding of wireless traffic modeling builds on classical Poisson distributed traffic, which can yield misleading results and hence poor wireless network planning. In this paper, we contribute to the accurate modeling of wireless IP traffic by considering two different types of traffic that exhibit long-range dependency and self-similarity. We consider a model of two queues based on G/M/1 queueing system and analyze it on the basis of 1-limited polling service and find exact bounds on packet delay.Publication Metadata only Clarification of issues on the closed-form Green's functions in stratified media(Institute of Electrical and Electronics Engineers (IEEE), 2005) Dural, G.; Department of Electrical and Electronics Engineering; Aksun, M. İrşadi; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 28358The closed-form Green's functions (CFGF), derived for the vector and scalar potentials in planar multilayer media, have been revisited to clarify some issues and misunderstandings on the derivation of these Green's functions. In addition, the range of validity of these Green's functions is assessed with and without explicit evaluation of the surface wave contributions. As it is well-known, the derivation of the CFGF begins with the approximation of the spectral-domain Green's functions by complex exponentials, and continues with applying the Sommerfeld identity to cast these approximated spectral-domain Green's functions into the space domain in closed forms. Questions and misunderstandings of this derivation, which have mainly originated from the approximation process of the spectral-domain Green's functions in terms of complex exponentials, can be categorized and discussed under the topics of: 1) branch-point contributions; 2) surface wave pole contributions; and 3) the accuracy of the obtained CFGF. When these issues are clarified, the region of validity of the CFGF so obtained may be defined better. Therefore, in this paper, these issues will be addressed first, and then their origins and possible remedies will be provided with solid analysis and numerical demonstrations.Publication Metadata only Receive quadrature reflecting modulation for ris-empowered wireless communications(Institute of Electrical and Electronics Engineers (IEEE), 2021) Yuan, Jing; Wen, Miaowen; Li, Qiang; Alexandropoulos, George C.; Chen, Gaojie; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 149116In this paper, we propose a novel reconfigurable intelligent surface (RIS)-based modulation scheme, named RIS-aided receive quadrature reflecting modulation (RIS-RQRM), by resorting to the concept of spatial modulation. In RIS-RQRM, the whole RIS is virtually partitioned into two halves to create signals with only in-phase (I-) and quadrature (Q-) components, respectively, and each half forms a beam to a receive antenna whose index carries the bit information. Furthermore, we design a low-complexity and non-coherent detector for RIS-RQRM, which measures the maximum power and polarities of the I- and Q- components of received signals. Approximate bit error rate (BER) expressions are derived for RIS-RQRM over Rician fading channels. Simulation results show that RIS-RQRM outperforms the existing counterparts without I/Q index modulation in terms of BER in the low signal-to-noise ratio region.Publication Metadata only Biological foraging-inspired communication in intermittently connected mobile cognitive radio ad hoc networks(Institute of Electrical and Electronics Engineers (IEEE), 2012) N/A; Department of Electrical and Electronics Engineering; Atakan, Barış; Akan, Özgür Barış; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 6647Publication Metadata only Adaptive path-following control for autonomous semi-trailer docking(Institute of Electrical and Electronics Engineers (IEEE), 2022) Aydemir, Eren; N/A; Department of Mechanical Engineering; Mamuş, Ayşe Ezgi; Lazoğlu, İsmail; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 179391Maneuvering a truck-trailer system while docking is extremely challenging. This article aims to alleviate this problem by presenting an enhanced path-following control framework for autonomous semi-trailer docking. In the proposed system, adaptive controllers that utilize gain scheduling are introduced for forward and reverse path-following tasks in docking maneuvers to increase the robustness and path-following performance. The system includes an improved pure pursuit controller with adaptive look-ahead distance for forward path following; a cascade controller of reverse pure pursuit and a gain-scheduled LQ control for reverse path-following. In the evaluation of the path-following performance of forward and reverse controllers, the closed-loop system of path-following controllers with the truck-trailer kinematic model is simulated in MATLAB/Simulink for various test cases, and the results are compared with those of other studies. Furthermore, different docking scenarios are generated via the cascade path planning algorithm for autonomous semitrailer docking. These are tested with a high degree semi-trailer model within the IPG TruckMaker simulation environment, and with a full truck-trailer vehicle in the test field. The results of both simulations and physical testing clearly demonstrate improvements in terms of the control problem formulation, i.e., the stabilized path-following is obtained with acceptable path-following errors.Publication Metadata only Design and integration of a bimorph thermal microactuator with electrostatically actuated microtweezers(Institute of Electrical and Electronics Engineers (IEEE), 2008) Yilmaz, Mehmet; Yalcinkaya, Arda D.; Leblebici, Yusuf; Zervas, Michalis; Department of Mechanical Engineering; Alaca, Burhanettin Erdem; Faculty Member; Department of Mechanical Engineering; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştirmalari Merkezi (KUYTAM); College of Engineering; 115108A multi-digit gripper is proposed that consists of two electrostatically actuated end-effectors operating in the plane of the device and three thermal end-effectors operating out of plane. The integration of thermal and electrostatic actuation mechanisms is realized by using a three-mask monolithic process. First mask is used to define the silicon electrostatic actuator on SOI wafer. Second mask is used to obtain the bimorph thermal microactuator made of polyimide and aluminum layers on top of the electrostatic actuator. Third and the final mask is used to release the integrated electrostatic and thermal microactuators.