Publications with Fulltext
Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/6
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Publication Open Access Optical scanners for high resolution RSD systems(Society of Photo-optical Instrumentation Engineers (SPIE), 2002) DeWitt, F.; Luanava, S.; Department of Electrical and Electronics Engineering; Ürey, Hakan; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 8579This paper outlines the design trade-offs and measured results of scanner architectures for use in high resolution Retinal Scanning Displays: Mechanical resonant for horizontal scanning, and MEMS-based pinch correction and vertical linear scanners. Analysis steps and techniques used to model and minimize dynamic deformations are covered. This paper also discusses two types of scanners and associated mirror flatness issues. Dynamic flatness modeling and performance results are presented, followed by thermally induced deformations and possible athermalize solutions for MEMS-type scanning mirrors. Theory, FEA dynamic and thermal analysis, experimental results, and methods to reduce mirror deformation are discussed.Publication Open Access Deep learning-aided 6G wireless networks: a comprehensive survey of revolutionary PHY architectures(Institute of Electrical and Electronics Engineers (IEEE), 2022) Department of Electrical and Electronics Engineering; Başar, Ertuğrul; Özpoyraz, Burak; Doğukan, Ali Tuğberk; Gevez, Yarkın; Altun, Ufuk; Faculty Member; Master Student; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; 149116; N/A; N/A; N/A; N/ADeep learning (DL) has proven its unprecedented success in diverse fields such as computer vision, natural language processing, and speech recognition by its strong representation ability and ease of computation. As we move forward to a thoroughly intelligent society with 6G wireless networks, new applications and use cases have been emerging with stringent requirements for next-generation wireless communications. Therefore, recent studies have focused on the potential of DL approaches in satisfying these rigorous needs and overcoming the deficiencies of existing model-based techniques. The main objective of this article is to unveil the state-of-the-art advancements in the field of DL-based physical layer methods to pave the way for fascinating applications of 6G. In particular, we have focused our attention on four promising physical layer concepts foreseen to dominate next-generation communications, namely massive multiple-input multiple-output systems, sophisticated multi-carrier waveform designs, reconfigurable intelligent surface-empowered communications, and physical layer security. We examine up-to-date developments in DL-based techniques, provide comparisons with state-of-the-art methods, and introduce a comprehensive guide for future directions. We also present an overview of the underlying concepts of DL, along with the theoretical background of well-known DL techniques. Furthermore, this article provides programming examples for a number of DL techniques and the implementation of a DL-based multiple-input multiple-output by sharing user-friendly code snippets, which might be useful for interested readers.Publication Open Access Index modulation aided subcarrier mapping for dual-hop OFDM relaying(Institute of Electrical and Electronics Engineers (IEEE), 2019) Wen, Miaowen; Chen, Xuan; Wu, Yik-Chung; Zhang, Wensong; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 149116There is a recent surge of research interest in the study of performance-enhancing techniques for orthogonal frequency division multiplexing (OFDM)-based relay systems. Among those, subcarrier mapping has been verified to be an effective one for boosting the system capacity and improving the error performance. However, it has to be performed at the relay, which subsequently conveys the subcarrier permutation information to the destination. The existing signaling scheme occupies a portion of subcarriers to this end, leading to a loss of spectral efficiency. In this paper, we propose a novel signaling scheme to eliminate this overhead by transferring the subcarrier permutation to the mode permutation that can be implicitly conveyed without consuming additional spectrum resources. We adopt phase rotation for mode design considering both non-adaptive and adaptive modulation, and illustrate the proposed scheme by taking the dual-hop OFDM relaying with semi-blind amplify-and-forward protocol as an example. An asymptotically tight upper bound on the bit error rate (BER) of the proposed scheme is derived in closed-form over Rayleigh fading channels. BER simulation results validate the analysis and show that the proposed scheme asymptotically approaches the ideal case that assumes perfect knowledge of subcarrier permutation information at the destination and significantly outperforms the existing scheme in the asymptotic signal-to-noise ratio region at the same spectral efficiency.Publication Open Access Channel sensing in molecular communications with single type of ligand receptors(Institute of Electrical and Electronics Engineers (IEEE), 2019) Kuşcu, Murat; Department of Electrical and Electronics Engineering; Akan, Özgür Barış; Faculty Member; Department of Electrical and Electronics Engineering; College of EngineeringMolecular communication (MC) uses molecules as information carriers between nanomachines. MC channel in practice can be crowded with different types of molecules, i.e., ligands, which can have similar binding properties causing severe cross-talk on ligand receptors. Simultaneous sensing of multiple ligand types provides opportunities for eliminating interference of external molecular sources and multi-user interference, and developing new multiple access techniques for MC nanonetworks. In this paper, we investigate channel sensing methods that use only a single type of receptors and exploit the amount of time receptors stay bound and unbound during ligand-receptor binding reaction to concurrently estimate the concentration of multiple types of ligands. We derive the Cramer-Rao Lower Bound for multi-ligand estimation, and propose practical and low-complexity suboptimal estimators for channel sensing. We analyze the performance of the proposed methods in terms of normalized mean squared error (NMSE), and show that they can efficiently estimate the concentration of ligands up to 10 different types with an average NMSE far below 10(-2). Lastly, we propose a synthetic receptor design based on modified kinetic proofreading scheme to sample the unbound and bound time durations, and a chemical reaction network to perform the required computations in synthetic cells.Publication Open Access A 2D MEMS stage for optical applications(Society of Photo-optical Instrumentation Engineers (SPIE), 2006) Ataman, Çağlar; Petremand, Yves; Noell, Wilfried; Epitaux, Marc; de Rooij, Nico F.; Department of Electrical and Electronics Engineering; Ürey, Hakan; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 8579A 2D MEMS platform for a microlens scanner application is reported. The platform is fabricated on an SOI wafer with 50/μm thick device layer. Entire device is defined with a single etching step on the same layer. Through four S-shaped beams, the device is capable of producing nonlinear 2D motion from linear ID translation of two pairs of comb actuator sets. The device has a clear aperture of 2mm by 2mm, which is hallowed from the backside for micro-optics assembly. In this paper, a numerical device model and its validation via experimental characterization results are presented. Integration of the micro-optical components with the stage is also discussed. Additionally, a new driving scheme to minimize the settling time of the device in DC operation is explored.Publication Open Access Joint code-frequency index modulation for IoT and multi-user communications(Institute of Electrical and Electronics Engineers (IEEE), 2019) Minh Au; Kaddoum, Georges; Alam, Md Sahabul; Gagnon, Francois; 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 family of index modulation systems which can operate with low-power consumption and low operational complexity for multi-user communication. This is particularly suitable for non-time sensitive Internet of Things (IoT) applications such as telemetry, smart metering, and soon. The proposed architecture reduces the peak-to-average-power ratio (PAPR) of orthogonal frequency-division multiplexing (OFDM)-based schemes without relegating the data rate. In the proposed scheme, we implement joint code-frequency-index modulation (CFIM) by considering code and frequency domains for index-modulation (IM). After introducing and analysing the structure of the CFIM, we derive closed-form expressions of the bit error rate (BER) performance over Rayleigh fading channels and we provide extensive simulation results to validate our outcomes. To better exhibit the particularities of the proposed scheme, the PAPR and complexity are thoroughly examined. The obtained results show that the PAPR is reduced compared to conventional OFDM-like IM-based schemes. Therefore, the proposed system is more likely to operate in the linear regime, which can in turn be implemented into low-cost devices with cost effective amplifiers. In addition, the concept is extended to synchronous multi-user communication networks, where full functionality is obtained by using orthogonal spreading codes. With the characteristics demonstrated in this work, the proposed system would constitute an exceptional nominee for IoT applications where low-complexity, low-power consumption and high data rate are paramount.Publication Open Access The effects of annealing on gas sensing properties of ZnO nanorod sensors coated with Pd and Pt(Elsevier, 2012) Özturk, S.; Öztürk, Z.Z.; Department of Electrical and Electronics Engineering; Kılınç, Necmettin; Researcher; Department of Electrical and Electronics Engineering; College of EngineeringIn this study, hydrogen (H2) gas sensing properties of palladium (Pd) & platinum (Pt) thin films coated and uncoated vertically alinged zinc oxide (ZnO) nanorods were investigated at different temperatures. On the other hand, the effects of annealing in dry air to gas sensing properties of the nanorods were investigated. Vertically aligned ZnO nanorods were fabricated by using hydrothermal method on glass substrate, and then Pd and Pt thin films was coated on to ZnO nanorods by using thermal evaporating system. The thickness of Pd or Pt thin film was approximately 15 nm. H2 sensing measurements were done in the temperature range of 25 - 200°C. It was found that the sensor response of Pd coated ZnO nanorods were much higher than uncoated ZnO nanorods because of catalytic effect Pd thin film. Moreover, unannealed samples showed better sensor response than annealed samples due to the surface charge number. The sensor response of all samples increased with enhancing temperature.Publication Open Access Low-cost uplink sparse code multiple access for spatial modulation(Institute of Electrical and Electronics Engineers (IEEE), 2019) Al-Nahhal, Ibrahim; Dobre, Octavia A; Ikki, Salama; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 149116Spatial modulation (SM) sparse codemultiple access (SCMA) systems provide high spectral efficiency (SE) at the expense of using a high number of transmit antennas. To overcome this drawback, this paper proposes a novel SM-SCMA system operating in uplink transmission, referred to as rotational generalized SM-SCMA (RGSM-SCMA). For the proposed system, the following are introduced, first, transmitter design and its formulation, second, maximum likelihood and maximum a posteriori probability decoders, and finally, practical low-complexitymessage passing algorithm and its complexity analysis. Simulation results and complexity analysis showthat the proposed RGSM-SCMA system delivers the same SE with significant savings in the number of transmit antennas, at the expense of close bit error rate and a negligible increase in the decoding complexity, when compared with SM-SCMA.