Publications with Fulltext
Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/6
Browse
13 results
Search Results
Publication Open Access Capacity analysis for joint radar-communication capable coherent MIMO radars(Elsevier, 2020) Department of Electrical and Electronics Engineering; Arık, Muharrem; Akan, Özgür Barış; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of EngineeringRecently, huge attention is attracted to the concept of integrating communication and radar missions within the same platform. Joint Radar-Communications (JRC) system gives an important opportunity to reduce spectrum usage and product cost while doing concurrent operation, as target sensing via radar processing and establishing communication links. A JRC-capable coherent MIMO radar system have been proposed recently in the literature. Several methods are introduced to reach dual goal as a notable null level towards the direction of interest of the radar and MIMO radar waveform orthogonality. Due to the limitations originated form the JRC operation, communication channel may encounter unwanted amplitude variations. This unwanted modulation normally affects the communication performance by its nature, due to the fades on radiated signal amplitude towards the direction of communication. However, the effect of this unintentional modulation on communication channel is yet to be investigated. In this paper, the communication channel for JRC capable phase-coded coherent MIMO radars is analyzed and investigated under additive white Gaussian noise and Rayleigh/Rician fading conditions. Communication capacity is evaluated for each channel condition. The results reveal that, using the single-side limited null direction fixed waveform generation method displays the best capacity performance under all channel conditions.Publication Open Access Predicting new iron garnet thin films with perpendicular magnetic anisotropy(Elsevier, 2020) N/A; Department of Electrical and Electronics Engineering; Zanjani, Saeedeh Mokarian; Onbaşlı, Mehmet Cengiz; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 258783Magnetic iron garnets are insulators with low Gilbert damping with many applications in spintronics. Many emerging spintronic applications require perpendicular magnetic anisotropy (PMA) although garnets have only a few PMA types (i.e. terbium and samarium garnet). More and stable PMA garnet options are needed for investigating new spintronic phenomena. In this study, we predict 20 new epitaxial magnetic iron garnet film/substrate pairs with stable PMA at room temperature. The effective anisotropy energies of 10 different garnet films that are lattice-matched to 5 different commercially available garnet substrates (total 50 film/substrate pairs) have been calculated using shape, magnetoelastic and magnetocrystalline anisotropy terms. Strain type, tensile or compressive depending on substrate choice, as well as the sign and the magnitude of the magnetostriction constants of garnets determine if a garnet film may possess PMA. We show the conditions in which Samarium, Gadolinium, Terbium, Holmium, Dysprosium and Thulium garnets may possess PMA on the investigated garnet substrate types. New PMA garnet films with tunable saturation moment and field may improve spin-orbit torque memory and compensated magnonic thin film devices.Publication Open Access Learned holographic light transport: invited(The Optical Society (OSA) Publishing, 2021) Akşit, Kaan; Department of Electrical and Electronics Engineering; Kavaklı, Koray; Ürey, Hakan; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; N/A; 8579Computer-generated holography algorithms often fall short in matching simulations with results from a physical holographic display.Our work addresses this mismatch by learning the holographic light transport in holographic displays. Using a camera and a holographic display, we capture the image reconstructions of optimized holograms that rely on ideal simulations to generate a dataset. Inspired by the ideal simulations, we learn a complex-valued convolution kernel that can propagate given holograms to captured photographs in our dataset. Our method can dramatically improve simulation accuracy and image quality in holographic displays while paving the way for physically informed learning approaches.Publication Open Access Fundamentals of green communications and computing: modeling and simulation(Institute of Electrical and Electronics Engineers (IEEE), 2012) Department of Electrical and Electronics Engineering; Akan, Özgür Barış; Malak, Derya; Kocaoğlu, Murat; Faculty Member; Department of Electrical and Electronics Engineering; College of EngineeringA layered architecture incorporates the concept of minimum energy consumption for communication links and computer networks with multiple terminals, where emission-reduction approaches based on information theory are impractical.Publication Open Access Multiple-input multiple-output generalized frequency division multiplexing with index modulation(Elsevier, 2019) Öztürk, Ersin; Çırpan, Hakan Ali; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 149116The demand for wireless access continues to grow with the new applications which create a broad range of technical challenges. Although orthogonal frequency division multiplexing (OFDM) with multiple numerologies concept will likely address the current technical challenges of fifth generation (5G) wireless networks, the sufficiency of OFDM-based physical layer (PHY) is quite disputable due to massive growth trend on the number of wireless users and applications for future wireless networks. Therefore, enhanced radio access technologies (RATs) are needed to fulfill the technical requirements of beyond 5G networks. Generalized frequency division multiplexing (GFDM) has attracted tremendous attention over the past few years because of its advantages in terms of out-of-band (OOB) emission, spectral efficiency and latency. Index modulation (IM) techniques convey digital information by utilizing transmission entities in an innovative way and offer attractive advantages such as energy and spectral efficiency without increasing the computational complexity. On the other hand, multiple-input multiple-output (MIMO) transmission is an unquestionable technology to enable increased spectral efficiency. In this paper, a novel MIMO-GFDM scheme, which combines spatial multiplexing (SMX) MIMO transmission, GFDM and IM, is proposed in order to provide an efficient transmission scheme for beyond 5G wireless networks. A minimum mean squared error (MMSE)-QR decomposition-based near-optimum detector is proposed for the receiver side and bit error rate, OOB emission, spectral efficiency and computational complexity of the proposed scheme are compared with classical SMX-OFDM and SMX-GFDM schemes via computer simulations. It has been demonstrated that the proposed SMX-GFDM-IM scheme can be considered as a viable PHY scheme for beyond 5G wireless networks.Publication Open Access Rescue: wireless power-enabled communication architecture for earthquake rescue operations(Elsevier, 2020) Ergül, Özgür; Department of Electrical and Electronics Engineering; Badırkhanlı, Orkhan; Akan, Özgür Barış; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of EngineeringIn a natural disaster such as an earthquake, it is vital to know the number of people trapped under the ruins. To address this problem, we propose RESCUE - wiREless backScattering CommUnication based disastEr recovery system. RESCUE is composed of special Radio-frequency identification (RFID) readers and sensors that are used to determine the total number of people under the ruins. Passive wireless sensor nodes are placed inside the building during construction and are equipped with a camera that is activated during an earthquake. After the earthquake, communication to the passive tags of sensors is achieved by wireless power transfer from a reader located outside the ruins. Tags harvest this energy and send the image data stored by the camera. We also design an antenna structure to maximize simultaneous wireless information and power transfer (SWIPT) for devices under ruins. We analyze the communication channel between reader and sensors and derive a channel model over ruins. Furthermore, we obtain the results of experimental study where we validate the derived channel model. Results show that RESCUE can collect the desired data in a relatively short time, and hence, is a promising disaster recovery system architecture.Publication Open Access Light-efficient augmented reality 3D display using highly transparent retro-reflective screen(Optical Society of America (OSA), 2017) Department of Electrical and Electronics Engineering; Ürey, Hakan; Soomro, Shoaib Rehman; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 8579; N/AWe propose and demonstrate a light efficient 3D display using a highly transparent desktop-size augmented reality screen. The display consists of a specially designed transparent retro-reflective screen and a pair of low power pico-projectors positioned close to the viewer’s eyes to provide stereo views. The transfer screen is an optically clear sheet partially patterned with retro-reflective microspheres for high optical gain. The retro-reflective material buried in the screen reflect incident light back towards the projectors with narrow scattering angle and facilitates the viewer to perceive a very bright content. The tabletop prototype mainly consists of an in-house fabricated large AR screen (60x40cm2) and a pair of laser scanning 30 lumen pico-projectors. The display is tested for different viewing configurations, different display parameters such as retro-reflective coefficient, eye-box size, polarization maintainability, stereo crosstalk and brightness. The AR prototype display provides 75% optical transparency, exceptional brightness (up to 1000 cd/m2 when viewed through beam-splitters and 350 cd/m2 with bare eyes) and negligible crosstalk in 3D mode (<5% and <1% when viewed through beam-splitters and polarizers respectively) for the working distance of up to 2 meters.
Publication Metadata only Predicting new iron garnet thin films with perpendicular magnetic anisotropy(Elsevier, 2020) Department of Electrical and Electronics Engineering; Zanjani, Saeedeh Mokarian; Onbaşlı, Mehmet Cengiz; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 258783Magnetic iron garnets are insulators with low Gilbert damping with many applications in spintronics. Many emerging spintronic applications require perpendicular magnetic anisotropy (PMA) although garnets have only a few PMA types (i.e. terbium and samarium garnet). More and stable PMA garnet options are needed for investigating new spintronic phenomena. In this study, we predict 20 new epitaxial magnetic iron garnet film/substrate pairs with stable PMA at room temperature. The effective anisotropy energies of 10 different garnet films that are lattice-matched to 5 different commercially available garnet substrates (total 50 film/substrate pairs) have been calculated using shape, magnetoelastic and magnetocrystalline anisotropy terms. Strain type, tensile or compressive depending on substrate choice, as well as the sign and the magnitude of the magnetostriction constants of garnets determine if a garnet film may possess PMA. We show the conditions in which Samarium, Gadolinium, Terbium, Holmium, Dysprosium and Thulium garnets may possess PMA on the investigated garnet substrate types. New PMA garnet films with tunable saturation moment and field may improve spin-orbit torque memory and compensated magnonic thin film devices.Publication Open Access ARIMA based time variation model for beneath the chassis UWB channel(SpringerOpen, 2016) Department of Electrical and Electronics Engineering; Ergen, Sinem Çöleri; Demir, Utku; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 7211; N/AIntra-vehicular wireless sensor network (ivwsn) enables the integration of the wireless sensor network technology into the vehicle architecture through either eliminating the wires between the existing sensors and the corresponding electronic controller units (ecus) or empowering new sensor technologies that are not currently implemented due to technical limitations. Ultra-wideband (uwb) has been determined to be the most appropriate technology for ivwsns since it provides energy efficiency through the low duty-cycle operation and high reliability by exploiting the large bandwidth. In this paper, we propose a time variation model for uwb-based ivwsn-based on the extensive amount of data collected from the transmitter and receiver antennas at various locations and separation distances beneath the chassis of a vehicle moving at different speeds on different types of roads. We adopt the commonly used saleh-valenzuela (sv) model to represent the clustering phenomenon in the received power delay profiles (pdps). The proposed novel time variation model then determines the time evolution of the pdps by representing the changes in their cluster breakpoints, slopes, and break point amplitudes with the auto-regressive integrated moving average (arima) model. Arima(5,1,0) has been demonstrated to fit the breakpoint, cluster slope, and breakpoint amplitude sequences collected at different vehicle speeds with different transmitter and receiver locations on asphalt and stone roads by using box-jenkins procedure. This model is validated with diagnostic checking. The absolute values of the model coefficients are observed to be mostly larger on asphalt road than their counterparts on the stone road while exhibiting no dependence on the vehicle speed nor the location of transmitter and receiver antennas.Publication Open Access Rapid alleviation of Parkinson's disease symptoms via electrostimulation of intrinsic auricular muscle zones(Frontiers, 2017) Cakmak, Yusuf O.; Apaydin, Hulya; Kiziltan, Gunes; Gunduz, Aysegul; Ozsoy, Burak; Cakmak, Ozgur O.; Ozdemir, Yasemin G.; Ertan, Sibel; Department of Electrical and Electronics Engineering; Ölçer, Selim; Ürey, Hakan; Other; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; N/A; 8579Background: Deep brain stimulation of the subthalamic nucleus (STN-DBS) and the pedunculopontine nucleus (PPN) significantly improve cardinal motor symptoms and postural instability and gait difficulty, respectively, in Parkinson's disease (PD). Objective and Hypothesis: Intrinsic auricular muscle zones (IAMZs) allow the potential to simultaneously stimulate the C2 spinal nerve, the trigeminal nerve, the facial nerve, and sympathetic and parasympathetic nerves in addition to providing muscle feedback and control areas including the STN, the PPN and mesencephalic locomotor regions. Our aim was to observe the clinical responses to IAMZ stimulation in PD patients.Method: Unilateral stimulation of an IAMZ, which includes muscle fibers for proprioception, the facial nerve, and C2, trigeminal and autonomic nerve fibers, at 130 Hz was performed in a placebo-and sham-controlled, double-blinded, within design, two-armed study of 24 PD patients.Results: The results of the first arm (10 patients) of the present study demonstrated a substantial improvement in Unified Parkinson's Disease Ratings Scale (UPDRS) motor scores due to 10 min of IAMZ electrostimulation (p = 0.0003, power: 0.99) compared to the placebo control (p = 0.130). A moderate to large clinical difference in the improvement in UPDRS motor scores was observed in the IAMZ electrostimulation group. The results of the second arm (14 patients) demonstrated significant improvements with dry needling (p = 0.011) and electrostimulation of the IAMZ (p < 0.001) but not with sham electrostimulation (p = 0.748). In addition, there was a significantly greater improvement in UPDRS motor scores in the IAMZ electrostimulation group compared to the IAMZ dry needling group (p < 0.001) and the sham electrostimulation (p < 0.001) groups. The improvement in UPDRS motor scores of the IAMZ electrostimulation group (Delta UPDRS = 5.29) reached moderate to high clinical significance, which was not the case for the dry needling group (Delta UPDRS = 1.54). In addition, both arms of the study demonstrated bilateral improvements in motor symptoms in response to unilateral IAMZ electrostimulation. Conclusion: The present study is the first demonstration of a potential role of IAMZ electrical stimulation in improving the clinical motor symptoms of PD patients in the short term.