Electrical & Electronics Engineering

Permanent URI for this collectionhttps://hdl.handle.net/10679/44

Browse

Now showing 1 - 20 of 677

Unknown
Unmanned aerial vehicle relay networks
(Help Cookies Privacy Statement Accessibility Modern Slavery Act Statement Legal notices The Institution of Engineering and Technology, 202) Adam, Evşen Yanmaz; Electrical & Electronics Engineering; Davoli, L.; Ferrari, G.; ADAM, Evşen Yanmaz
N/A
Unknown
SCARA with Path trajectory
(2008) Elamassie, Mohammed; Elamassie, Mohammed
The following Matlab project contains the source code and Matlab examples used for SCARA with Path trajectory. By defining the initial position and final position the robot will follow the path between these two points
Unknown
Improving the performance of wireless H.264 video broadcasting through a cross-layer design
(IEEE, 2009) Atıcı, Çağdaş; Sunay, Mehmet Oğuz; Computer Science; SUNAY, Mehmet Oğuz; Atıcı, Çağdaş
In a wireless video broadcasting service, number of users receiving the service and the average video quality of the received stream have to be maximized for improving the system performance. To solve this problem optimally, one may adjust parameters at the physical and the application layers in a cross-layer fashion while utilizing the characteristics of the videothat is being transmitted. In this paper, we propose a multiobjective optimized, cross-layer video broadcasting scheme for a wireless system capable of supporting a multitude of transmission data-rates using the H.264/AVC. The multi-objective, cross-layer optimization aims to find the H.264/AVC as well as the physical layer system parameters jointly to reach the optimal compromise between maximizing the average received video PSNR and minimizing the video broadcast service outage probability. Simulations conducted for the ITU Pedestrian A and Vehicular B channels show that further gains in system performance can be achieved for video broadcasting when such a cross-layer design is used.
Unknown
Capacity of wireless ad-hoc broadcast networks under realistic channel models
(IEEE, 2009) Atıcı, Çağdaş; Sunay, Mehmet Oğuz; Computer Science; SUNAY, Mehmet Oğuz; Atıcı, Çağdaş
In a wireless broadcasting scenario, some of the nodes can help the source node by forwarding the received information. Due to the interference from multiple transmissions, selection of these nodes directly affects the performance of the system under a given total power and hop constraint. In this paper, we first analytically find the number and the positions of the rebroadcasting nodes that achieve the optimal broadcast capacity under the continuum model. Following the results of this part, we propose two heuristics, one centralized and another distributed, for relay selection in practical scenarios. Then, we discuss the broadcast capacity performances of these algorithms under different system settings. The results illustrate that using a distributed relay selection method brings significant gains to the broadcast capacity under a realistic system model.
Unknown
On the broadcast capacity of wireless multihop interference networks
(IEEE, 2009) Atıcı, Çağdaş; Sunay, Mehmet Oğuz; Computer Science; SUNAY, Mehmet Oğuz; Atıcı, Çağdaş
This paper is concerned with wireless broadcasting in multihop networks where a selected number of relay nodes may aid the source node in the broadcast under a given total energy and hop constraint. We study an ad-hoc network with infinitely many nodes and analytically find the number and positions of rebroadcasting relay nodes to achieve the optimal broadcast capacity. The interference due to multiple transmissions in the geographical area is taken into account. Based on the theoretical findings, we then propose one distributed and one centralized heuristic for relay selection in wireless broadcasting. We discuss the broadcast capacity performances and CSI (channel state information) requirements of these algorithms. The results illustrate that the benefits of peer-assisted broadcasting are more pronounced in the centralized relay selection algorithm when compared to the fully randomized and distributed selection under a realistic system model.
Unknown
Pseudoscalar-meson-octet-baryon coupling constants in two-flavor lattice QCD
(American Physical Society, 2009-04-01) Erkol, Güray; Oka, M.; Takahashi, T. T.; Natural and Mathematical Sciences; ERKOL, Güray
We evaluate the πΝΝ, π∑∑, πΛ∑, KΛN and K∑N coupling constants and the corresponding monopole masses in lattice QCD with two flavors of dynamical quarks. The parameters representing the SU(3)-flavor symmetry are computed at the point where the three quark flavors are degenerate at the physical s-quark mass. In particular, we obtain α ≡ F/(F+D) = 0.395(6). The quark-mass dependences of the coupling constants are obtained by changing the u- and the d-quark masses. We find that the SU(3)-flavor parameters have weak quark-mass dependence and thus the SU(3)-flavor symmetry is brokenby only a few percent at each quark-mass point we consider.
Unknown
Spin content of Λ in QCD sum rules
(American Physical Society, 2009-06-01) Erkol, Güray; Oka, M.; Natural and Mathematical Sciences; ERKOL, Güray
We calculate the isoscalar axial-vector coupling constants of the Λ hyperon using the method of QCD sum rules. A determination of these coupling constants reveals the individual contributions of the u, d, and the s quarks to the spin content of Λ. Our results for the light-quark contributions are in agreement with those from experiment assuming flavor SU(3). We also find that the flavor-SU(3)-breaking effects are small and the contributions from the u and the d quarks to the Λ polarization are negatively polarized as in the flavor-SU(3) limit.
Unknown
Performance analysis of cooperative diversity networks with imperfect channel estimation over Rician fading channels
(IEEE, 2010) Ikki, S. S.; Feteiha, M.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
In this paper, we examine the effect of channel estimation error on the error and outage probabilities of a multi-relay system with amplify-and-forward relaying over frequency-flat Rician fading channel. We consider orthogonal relaying and study both conventional cooperative systems (i.e., all relays participate in the relaying phase) and opportunistic cooperative systems (i.e., only the best relay participates in the relaying phase). Based on the derivation of effective signal-to-ratio (SNR) at the receiver taking into account channel estimation error, we obtain closed-form expressions for error and outage probabilities in high SNR regime. Such closed form solutions are highly desirable because they allow for rapid and efficient evaluation of system performance. Computer simulations are used to validate our analytical results.
Metadata only
Kuvvetlendir-ve-aktar tipi işbirlikli haberleşme sistemlerinde zaman senkronizasyonu
(IEEE, 2010) Odabaşıoğlu, N.; Ak, S.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
The synchronization problem in wireless communication systems becomes more important especially in cooperative communication systems than it is for other diversity systems because all terminals in the cooperation use their own local oscillators. In this study, a maximum likelihood based receiver is proposed as a solution to time synchronization problem in cooperative communication systems. The bit error rate performance of the proposed receiver is demonstrated by using computer simulations. Based on experimental results, we see that a considerable amount of power gain can be obtained using the proposed receiver. This power gain is increased as the time difference between signals arriving to the receiver from different terminals goes up.
Metadata only
Channel estimation for amplify-and forward relaying: cascaded against disintegrated estimators
(IEEE, 2010) Amin, O.; Gedik, B.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
The authors investigate the performance of amplify-and-forward relaying with two different pilot-symbol-assisted channel estimation methods. In the first estimation method, the cascaded channel consisting of source-to-relay and relay-to-destination links is estimated at the destination terminal. No channel estimator is required at the relay terminal. In the second estimation method, the estimation of cascaded channel is disintegrated into separate estimations of source-to-relay and relay-to-destination links which are carried out at the relay and the destination terminals, respectively. The latter method involves feed-forwarding a quantised version of the source-to-relay channel estimate to the destination terminal. Through the derivation of mean squared error (MSE) diversity gain analysis and Monte-Carlo simulations, the authors investigate the performance of amplify-and-forward relaying with these channel estimation methods. Our results demonstrate that full diversity can be achieved in the presence of channel estimation. The authors further show that cascaded channel estimator outperforms its competitor with a small number of quantisation bits. As the number of employed quantisation bits increase, disintegrated channel estimator approaches to its competitor eventually outperforming it.
Metadata only
Exact closed-form error probability expression for cooperative diversity networks with channel estimation errors in time selective Rayleigh fading channels
(IEEE, 2010) Ikki, S. S.; Al-Dharrab, S. I.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
In this paper, we investigate the performance of a cooperative network with adaptive decode-and-forward (DF) relaying over time-selective frequency-flat Rayleigh fading channels. In adaptive DF relaying, only a subset of the available relays with "good" channels are allowed to participate in the relaying phase. The destination combines the direct and the relayed signals using maximal ratio combining technique. Pilot-symbol-assisted modulation (PSAM) is used for the estimation of time-varying fading channel coefficients. For the system under consideration, we derive an exact closed-form expression for the average bit error rate. Such closed form solutions are highly desirable because they allow for rapid and efficient evaluation of system performance. We further present computer simulations to validate our analytical results.
Metadata only
DMT analysis of coherent free-space optical systems over atmospheric turbulence channels
(IEEE, 2010) Aghajanzadeh, S. M.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
In this paper, we investigate the diversity-multiplexing tradeoff (DMT) performance of a coherent free-space optical (FSO) communication system with multiple receive apertures over atmospheric turbulence channels. Our study builds on the recently introduced statistical model that characterizes the combined effects of turbulence-induced wavefront distortion and amplitude fluctuation in coherent receivers with phase compensation. Our results provide insight into performance mechanisms of coherent FSO systems and demonstrate significant performance gains that can be obtained through the deployment of multiple receive apertures and phase compensation techniques.
Metadata only
Performance analysis of cooperative diversity networks with imperfect channel estimation
(IEEE, 2010) Ikki, S. S.; Amin, O.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
In this paper, we investigate the effect of channel estimation error on the error rate performance of a multi-relay system with amplify-and-forward relaying. We consider orthogonal relaying and study both conventional cooperative systems (i.e., all relays participate in the relaying phase) and opportunistic cooperative systems (i.e., only the best relay participates in the relaying phase). Based on the derivation of effective signal-to-noise ratio at the receiver taking into account channel estimation error, we obtain closed-form expressions for bit error rate. Monte-Carlo simulations are further provided to confirm the analytical results.
Metadata only
Diffusion-based approach to deploying wireless sensor networks
(Inderscience, 2010) Machado, R.; Tekinay, Şirin; Zhang, W.; Wang, G.; Electrical & Electronics Engineering; TEKİNAY, Şirin
An important objective of Wireless Sensor Networks (WSNs) is to reliably sense data about the environment in which they are deployed. Reliability in WSNs has been widely studied in terms of providing reliable routing protocols for message dissemination and reliability of communication from sink to sensors. In this work, we define a reliability metric by the amount of data sensed by the network. In order to satisfy this reliability constraint, we propose a diffusion-based approach for a deployment pattern for the sensor nodes. We show that this deployment pattern achieves sufficient coverage and connectivity and requires lesser number of sensors than popular regular deployment patterns. We further obtain the bounds on establishing connectivity between nodes in the WSN and extend this analysis for heterogeneous WSNs.
Metadata only
Connectivity brokerage: from coexistence to collaboration
(IEEE, 2010) Parsa, A.; Ercan, Ali Özer; Malagon, P.; Burghardt, F.; Rabaey, J. M.; Wolisz, A.; Electrical & Electronics Engineering; ERCAN, Ali Özer
The explosive growth in the density of wirelessly connected devices and their traffic load is creating interference and gradually leading to a severe spectrum shortage. Approaches to address this challenge include dynamic spectrum allocation (cognitive radio) and pro-active interference mitigation strategies requiring coordination between heterogeneous networking technologies. This paper describes a modular and scalable methodology and architecture, called Connectivity Brokerage, that enables proactive co-existence and collaboration between diverse technologies, making joint optimization of the scarce spectrum resources possible.
Open Access
Meson-baryon coupling constants in two-flavor lattice QCD
(American Institute of Physics, 2010) Erkol, Güray; Oka, M.; Takahashi, T. T.; Natural and Mathematical Sciences; ERKOL, Güray
We evaluate the pseudoscalar-meson coupling constants and the strangeness-conservingand the strangeness-changing axial charges of octet baryons in lattice QCD with two flavors ofdynamical quarks.We find that the coupling constants and the axial charges have rather weak quarkmassdependence and the breaking in SU(3)-flavor symmetry is small at each quark-mass point weconsider.
Metadata only
Redundancy estimation and adaptive density control inwireless sensor networks
(Old City Publishing, 2010) Machado, R.; He, H.; Wang, G.; Tekinay, Şirin; Electrical & Electronics Engineering; TEKİNAY, Şirin
While dense random deployment satisfies coverage and sensing requirements, constructing dense networks of sensor nodes poses the problems of obtaining node location information.We provide an analytical framework for estimating the redundancy in a single-hop WSN of random deployment of nodes without the need of location information of nodes. We use an information theoretic approach to estimate the redundancy and provide the Cramer-Rao bound on the error in the estimation. We illustrate this redundancy estimation approach and calculate the bounds on the error in the estimation for a WSN with 1-redundancy. We also analytically show the inter-dependence between redundancy and network lifetime for random deployment. We further study the energy model of a WSN as interdependence between the environmental variation and its impact on the energy consumption at individual nodes. Defining network energy as the sum of residual battery energy at nodes, we provide an analytical framework for the dependence of node energy and sensitivity of network energy as a function of environmental variation and reliability parameters. Using a neural network based approach, we perform adaptive density control and show how reliability requirements and environment variation influences the rate of change of network energy.
Metadata only
Kaskat nakagami kanallara sahip röleli sistemler için dağıtılmış uzay-zaman kafes kod tasarımı
(IEEE, 2010) İlhan, H.; Altunbaş, İ.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
Bu çalışmada, tek roleli, işbirlikli ve kodlamalı bir sistemin kanallarının kaskat Nakagami dağılımlı olması durumundaki hata performans analizi yapılmıştır. Sistemin genel çiftsel hata olasılığı üst sınırı kullanılarak dağıtılmış uzay-zaman kodlar için kod tasarım ölçütü belirlenmiş ve bu ölçüt kullanılarak 4-PSK ve 8-PSK modülasyonları için 8 durumlu dağıtılmış uzay-zaman kafes kodları tasarlanmıştır. Tasarlanan kodların hata performansları bilgisayar benzetimi ile değerlendirilmiş ve referans alınan kodlarınki ile karşılaştırılmıştır.
Open Access
Axial charges of octet baryons in two-flavor lattice QCD
(Elsevier, 2010-03-15) Erkol, Güray; Oka, M.; Takahashi, T. T.; Natural and Mathematical Sciences; ERKOL, Güray
We evaluate the strangeness-conserving NN, ΣΣ, ΞΞ, ΛΣ and the strangeness-changing ΛN, ΣN, ΛΞ, ΣΞ axial charges in lattice QCD with two flavors of dynamical quarks and extend our previous work on pseudoscalar-meson–octet-baryon coupling constants so as to include πΞΞ, KΛΞ and KΣΞ coupling constants. We find that the axial charges have rather weak quark mass dependence and the breaking in SU(3)-flavor symmetry is small at each quark-mass point we consider.
Metadata only
Iterative near maximum-likelihood sequence detection for MIMO optical wireless systems
(IEEE, 2010-04) Chatzidiamantis, N. D.; Uysal, Murat; Tsiftsis, T. A.; Karagiannidis, G. K.; Electrical & Electronics Engineering; UYSAL, Murat
A major performance-limiting factor in terrestrial optical wireless (OW) systems is turbulence-induced fading. Exploiting the additional degrees of freedom in the spatial dimension, multiple laser transmitters combined with multiple receive apertures provide an effective solution for fading mitigation. Although multiple-input multiple-output (MIMO) OWsystems have been extensively studied in recent years, most of these works are mainly limited to symbol-by-symbol decoding. MLSD exploits the temporal correlation of turbulence-induced fading and promises further performance gains. In this paper, we investigate MLSD for intensity-modulation/direct-detection MIMO OW systems over log-normal atmospheric turbulence channels. Even with a low-order modulation scheme such as OOK, which is typically used inOWsystems, the complexity ofMLSD might be prohibitive. We therefore present an iterative sequence detector based on the expectation–maximization (EM) algorithm. The complexity of the proposed algorithm is considerably less than a direct evaluation of the log-likelihood function, and it is independent of the channel’s fading statistics. The Monte Carlo simulation results demonstrate that the EM-based algorithm outperforms the symbol-by-symbol decoder and achieves a performance, which lies within 0.3 dB of that of the optimal MLSD.

Browse

Browsing by Issue Date