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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
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Publication Metadata only Automatic PMD compensation by unsupervised polarization diversity combining coherent receivers(IEEE-Inst Electrical Electronics Engineers Inc, 2008) Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Erdoğan, Alper Tunga; Demir, Alper; Faculty Member; Faculty Member; Master Student; Department of Electrical and Electronics Engineering; College of Engineering; College of Engineering; 41624; 3756; N/AA new automatic scheme to compensate the inter-symbol interference caused by fiber polarization mode dispersion (PMD) is introduced. The proposed method makes use of the orthogonal polarization components by combining them through adaptive electronic filters, which are adjusted through a low-complexity unsupervised updating method. The simplicity of the proposed unsupervised method is its most critical feature in terms of enabling real-time and all-hardware implementation. Simulation results are provided for a fiber channel with 40 Gsymbols/s signalling rate and a mean DGD level greater than the symbol period, where it is demonstrated that the PMD can be effectively compensated with a 2 dB signal-to-noise ratio penalty relative to PMD-free channel.Publication Metadata only Spectrum-aware underwater networks cognitive acoustic communications(IEEE-Inst Electrical Electronics Engineers Inc, 2012) Asaf Behzat; Akan; N/A; Department of Electrical and Electronics Engineering; Biçen, Ahmet Ozan; Akan, Özgür Barış; Master Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 6647In this article, CAC to empower SUN inspiring from CR paradigm in wireless terrestrial communications is proposed. Spectrum scarcity in UAC due to the uniquely challenging underwater acoustic spectrum is discussed, and the need for spectrum-aware communication techniques is pointed out. We explore the capacity gain that can be achieved via CAC in SUN by simulation experiments and investigate the advantages and limitations of SUN along with its tradeoffs for DSA and OSA separately. Clearly, SUN can reach higher capacities than traditional fixed-spectrum approaches with the help of CAC capability. We expect that this article will provide better recognition for the capabilities of SUN and actuate further research efforts to explore this favorable area.Publication Metadata only Energy-efficient data transmission for capacitive-coupled human body communication systems(Ieee-Inst Electrical Electronics Engineers Inc, 2021) Filipovic, Luka; Herceg, Marijan; Vlaovic, Jelena; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 149116In this letter, an energy-efficient and low-complexity method for capacitive-coupled human body communication (CC-HBC) systems is proposed. In the proposed method, called impedance shift keying CC-HBC, the change of impedance between the transmitter's signal and the ground electrode is used to map information. In particular, the transmitter changes the condition of an electrical field generated by the receiver by changing the impedance between its signal and ground electrodes. Subsequently, by detecting the changes in the electric field, the receiver can demodulate the information sent by the transmitter. The CC-HBC channel is obtained using the transfer function method, while the performance of the proposed scheme is compared with frequency shift keying and on-off keying modulations.Publication Metadata only Peer-to-peer multipoint video conferencing using layered video(IEEE, 2006) N/A; Department of Electrical and Electronics Engineering; Department of Computer Engineering; Akkuş, İstemi Ekin; Civanlar, Mehmet Reha; Özkasap, Öznur; Master Student; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Department of Computer Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; 16372; 113507A new peer-to-peer architecture for multipoint video conferencing is presented. It targets end points with low bandwidth network connections (single video in and out), Allowing them to create a multipoint conference without any additional networking and computing resources than what is needed for a point-to-point conference. the new architecture is based on use of layered video coding with two layers at the end points. It allows each conference participant to see any other participant at any given time under all multipoint configurations of any number of users with a caveat that some participants may have to receive only the base layer video. Layered encoding approaches usable within this architecture are described. a protocol for implementation of the new approach has been developed and simulated. Its performance is analyzed.Publication Metadata only Index modulation-based flexible non-orthogonal multiple access(IEEE-Inst Electrical Electronics Engineers Inc, 2020) N/A; N/A; Department of Electrical and Electronics Engineering; Arslan, Emre; Doğukan, Ali Tuğberk; Başar, Ertuğrul; PhD Student; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 149116Non-orthogonal multiple access (NOMa) is envisioned as an efficient candidate for future communication systems. This letter proposes a novel orthogonal frequency division multiplexing (ofDM) with index modulation (IM)-based NOMa scheme, called ofDM-IM NOMa, for future multi-user communication systems. inspired by IM and classical NOMa-ofDM, users utilize flexibility by adjusting power allocation factors and subcarrier activation ratios. Our new scheme allows different service users to share available resources as in classical NOMa, more efficiently. It is shown that ofDM-IM NOMa reliably supports a high and low data rate user at the same resources by adjusting their subcarrier activation ratios.Publication Metadata only Compact and broadband silicon photonic multiplexers based on fast adiabatic structures(IEEE, 2021) N/A; Department of Electrical and Electronics Engineering; Görgülü, Kazım; Mağden, Emir Salih; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; N/A; College of Engineering; N/A; 276368We present the theory and experimental demonstration for compact integrated spectral multiplexers utilizing fast adiabatic structures. The demonstrated 1x2 multiplexers effectively separate/combine broadband long-pass and short-pass signals, with compact footprint and low loss. (c) 2021 The Author(s)Publication Metadata only Flexible luma-chroma bit allocation in learned image compression for high-fidelity sharper images(IEEE, 2022) N/A; Department of Electrical and Electronics Engineering; Ulaş, Ökkeş Uğur; Tekalp, Ahmet Murat; Master student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 26207High-fidelity learned image/video compression solutions are typically optimized with respect to l1 or l2 loss in RGB 444 format and evaluated by RGB PSNR. It is well-known that optimization of a fidelity criterion results in blurry images, which is typically alleviated by adding a content-based and/or adversarial loss terms. However, such conditional generative models result in loss of fidelity. In this paper, we propose a simple solution to obtain sharper images without losing fidelity based on learned flexible-rate coding using gained variational auto-encoder (gained-VAE) in the luma-chroma (YCrCb 444) domain. This allows us to implement image-adaptive luma-chroma bit allocation during inference, i.e., to increase Y PSNR at the expense of slightly lower chroma PSNR to obtain sharper images without introducing color artifacts based on the observation that Y PSNR correlates with image sharpness better than RGB PSNR. We note that the proposed inference-time image-adaptive luma-chroma bit allocation strategy can be incorporated into any VAE-based image compression model. Experimental results show that sharper images with better VMAF and Y PSNR can be obtained by optimizing models for YCrCb MSE with the proposed image-adaptive luma-chroma bit/quality allocation compared to stateof-the-art models optimizing RGB MSE at the same bpp.Publication Metadata only Managed video services over multi-domain software defined networks(IEEE Computer Society, 2016) N/A; Department of Electrical and Electronics Engineering; Bağcı, Kadir Tolga; Tekalp, Ahmet Murat; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 26207We introduce a framework for provisioning end-toend (E2E) managed video services over a multi-domain SDN, where different domains may be operated by different network providers. The proposed framework enables efficient dynamic management of network resources for network providers and ability to request the desired level of quality of experience (QoE) for end users. In the proposed fully-distributed E2E service framework, controllers of different domains negotiate with each other for the service level parameters of specific flows. The main contributions of this paper are a framework to provide E2E video services over multi-domain SDN, where functions that manage E2E services can collaborate with functions that manage network resources of respective domains, and a procedure for optimization of service parameters within each domain. The proposed framework and procedure have been verified over a newly developed large-scale multi-domain SDN emulation environment.Publication Metadata only Compact adiabatic silicon photonic filters with arbitrary and ultra-broadband response(IEEE, 2022) N/A; Department of Electrical and Electronics Engineering; Görgülü, Kazım; Mağden, Emir Salih; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; N/A; College of Engineering; N/A; 276368We present the design and experimental demonstration of compact silicon photonic filters through optimized fast adiabatic waveguides with arbitrarily wide bandwidths. Our devices achieve passbands up to 96.6 nm with flat-top and low-loss operation. (C) 2022 The Author(s)Publication Metadata only Emulation and inversion of polarization mode dispersion: a lumped system and pade approximation perspective(IEEE-Inst Electrical Electronics Engineers Inc, 2008) Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Demir, Alper; Erdoğan, Alper Tunga; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; College of Engineering; 3756; 41624Polarization mode dispersion (PMD) has been a major impediment in achieving higher speeds in optical fiber communication systems. Various approaches and techniques for the basic theoretical analysis, modeling, simulation, and compensation of PMD have been proposed in the literature. In this paper, we present a novel and fresh approach to the modeling, emulation and inversion of PMD in optical fibers. In our approach, we first build a full PMD model based on coupled mode theory as a continuous-time, lumped and lossless system. We then develop systematic model dimension reduction techniques, adapted from Krylov-subspace based methods for large electronic systems, in order to obtain compact and low complexity PMD models. The reduced complexity models produced by our technique match the full PMD model over a specifiable frequency range of interest, have the same structure as the full model, and are amenable to efficient software and low complexity hardware implementations for emulation and inversion. Furthermore, the reduced compexity PMD modeling framework we develop in this paper can serve as a general formalism for studying the compressibility of PMD models and emulators.