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Yayın Cognitive cooperative MAC with one primary and two secondary users: achievable rates and optimal power control(IEEE-INST Electrical Electronics Engineers Inc, 2014-11) Edemen, Çağatay; Kaya, OnurWe consider a three-user fading cognitive cooperative multiple access channel (MAC) with one primary and two secondary transmitters. We propose two encoding/decoding strategies with varying levels of cooperation, based on block Markov superposition encoding and backward decoding. The first is an overlay model, where the secondary users (SUs) aid the transmission of the primary user (PU) by causally decoding the PU message and forwarding it while also cooperating among each other. The second is an underlay model, where the SUs cooperate by decoding and forwarding each other's messages while treating the signal received from the PU as noise. In either case, the PU is guaranteed to operate at its maximum achievable single user rate. We characterize the achievable SU rate region for both models and maximize this region as a function of the transmit powers. The simulation results show that the SU rate region can be significantly enlarged, particularly using the overlay model.Yayın Equilibrium and stability analysis of delayed neural networks under parameter uncertainties(Elsevier Science Inc, 2012-02-15) Faydasıçok, Özlem; Arik, SabriThis paper proposes new results for the existence, uniqueness and global asymptotic stability of the equilibrium point for neural networks with multiple time delays under parameter uncertainties. By using Lyapunov stability theorem and applying homeomorphism mapping theorem, new delay-independent stability criteria are obtained. The obtained results are in terms of network parameters of the neural system only and therefore they can be easily checked. We also present some illustrative numerical examples to demonstrate that our result are new and improve corresponding results derived in the previous literature.Yayın Mülteci barınaklarının uydu görüntülerinden çoklu-sınıflı çizge-kesme bölütleme ve gölge bilgisi kullanılarak otomatik sezimi(IEEE, 2014-04-23) Kucur Ergünay, Şerife Seda; Kahraman, Fatih; Ateş, Hasan FehmiBu çalışmada, mülteci kamplarında bulunan yaşam alanlarının/barınakların (çadır, konteynır vb.) uydu ve hava görüntülerinden otomatik olarak sezimi ve sayımına yönelik bir yöntem tanıtılmaktadır. Mülteci kamplarındaki barınakların çok yüksek çözünürlüklü (VHR) görüntülerde dahi çok küçük boyuta sahip, belli bir alanda çok sık ve bazen karmaşık şekilde yerleştirilmiş ve arkaplan ile ayrıştırılması zor nesnelere denk geliyor olması otomatik barınak/çadır sezim ve sayımını zorlaştırmaktadır. Bahsedilen problemin çözümüne yönelik olarak çok sınıflı çizge-kesme (graph-cut) bölütlemesi ve gölge bilgisinin kullanıldığı özgün bir yöntem çalışma kapsamında önerilmektedir. Buna göre, ilk adımda çizge-kesme bölütleme yöntemi ve morfoloji işlemleri uygulanarak çadır sezimi yapılmıştır. Bu adımda sezilememiş çadırların bulunabilmesi için ikinci bir adımda çadırların gölge bilgisinden faydalanılmıştır. En son adımda gradyan-tabanlı eşikleme yöntemi ile yanlış tespitlerin elenmesi amaçlanmıştır. Önerilen yöntem, özellikle karmaşık yerleşim düzenine sahip mülteci kampları (çadırkent) üzerinde test edilmiştir. Yöntemin başarımı kesinlik (precision) ve geri getirme (recall) kriterlerine göre belirlenmiştir. Elde edilen ortalama kesinlik ve geri getirme başarımları sırasıyla %91.9 ve %90.0 olup problemin zorluğu göz önünde bulundurulduğunda umut vadedici bir sonuçtur.Yayın Generic BER analysis of VLC channels impaired by 3D user-mobility and imperfect CSI(Institute of Electrical and Electronics Engineers Inc., 2021-07) Reddy Sekhar, K.; Miramirkhani, Farshad; Mitra, Rangeet; Turlapaty, Anish ChandVisible light communications (VLC) has emerged as a high-speed, low-cost, and green supplement for the existing radio frequency (RF) based infrastructures. However, the performance of VLC based systems is found to degrade significantly due to detrimental outages caused by non-negligible variations in the VLC channel-gain, that are jointly induced by radial user-mobility and random photodetector-orientation (together designated as 3D mobility in this letter). In addition to the 3D user-mobility mentioned above, the performance of VLC based systems is further limited by imperfect channel-state information (CSI). Such degradations in the VLC-link caused by the aforementioned factors necessitate the quantification of performance-metrics for further benchmarking/receiver-design. In this work, an analytical expression for bit-error rate (BER) is derived for a single LED indoor VLC system considering the radial user-mobility, random receiver orientation, and imperfect CSI altogether. Further, the derived BER expressions are validated using computer-simulations using typical VLC channel models from the literature. A close agreement between the analytical and the simulated BER is observed, which verifies the accuracy of the presented analysis.Yayın A New speech coding algorithm using zero cross and phoneme based SYMPES(IEEE, 2013-07-11) Şişman, Burak; Güz, Ümit; Gürkan, Hakan; Yarman, Bekir Sıddık BinboğaIn this work, a new low bit rate hybrid speech coding approach which combines the benefits of the SYMPES (Systematic Procedure for Predefined Envelope and Signature Sequences) and zero cross and phoneme based segmentation is proposed. In the new approach, the SYMPES structure is developed in the phoneme based fashion. In order to achieve lower bit rates, some drawbacks such as computational complexity, relatively high encoding times etc. of the SYMPES are also eliminated in the new version. Experimental results show that in almost same bit rates very promising speech quality is obtained compared to the other conventional methods such as CELP (Code Excited Linear Predictive) coding algorithm.Yayın 2W wideband microwave PA design for 824-2170 MHz band using normalized gain function method(IEEE, 2013) Köprü, Ramazan; Kuntman, Hulusi Hakan; Yarman, Bekir Sıddık BinboğaIn this work, we present the design of a 2W linear wideband microwave PA (power amplifier) targeted to operate in 824-2170 MHz mobile frequency range covering GSM850, EGSM, DCS, PCS and WCDMA. The design is basically based on the NGF (Normalized Gain Function) method which is very recently introduced into the literature. NGF is defined as the ratio of T and |S-21|(2), i.e. T-NGF= T/|S-21|(2), shape of the gain function of the amplifier to be designed and the shape of the transistor forward gain function, respectively. Synthesis of input/output matching networks (IMN/OMN) of the amplifier requires target gain functions, which are mathematically generated in terms of TNGF. The particular transistor used in the design is FP31QF, a 2W HFET from TriQuint Semiconductor. Theoretical PA performance obtained in Matlab is shown to be in a very high agreement with the simulated performance in MWO (Microwave Office) of AWR Inc.Yayın Energy harvesting cooperative multiple access channel with data arrivals(IEEE, 2016) Gürakan, Berk; Kaya, Onur; Ulukuş, ŞennurWe consider an energy harvesting two user cooperative Gaussian multiple access channel (MAC), where both of the users harvest energy from nature. The data packets arrive intermittently over time. The users overhear each other's transmitted signals and can cooperate by forming common messages. We find the optimal offline transmit power and rate allocation policy that maximize the departure region. We first show that there exists an optimal policy, in which the single user rate constraints in each time slot are tight, yielding a one to one relation between the powers and rates. Then, we formulate the departure region maximization problem as a weighted sum rate maximization in terms of rates only. Next, we propose a sequential convex approximation method to approximate the problem at each step and show that it converges to the optimal solution. Finally, we solve the approximate problems using an inner outer decomposition method. Numerically, we observe that higher data rates can be supported with the same amount of energy.Yayın A survey of algorithms and architectures for H.264 sub-pixel motion estimation(World Scientific, 2012-05) Fatemi, Mohammad Reza Hosseiny; Ateş, Hasan Fehmi; Salleh, Rosli BinThis paper reviews recent state-of-the-art H. 264 sub-pixel motion estimation (SME) algorithms and architectures. First, H.264 SME is analyzed and the impact of its functionalities on coding performance is investigated. Then, design space of SME algorithms is explored representing design problems, approaches, and recent advanced algorithms. Besides, design challenges and strategies of SME hardware architectures are discussed and promising architectures are surveyed. Further perspectives and future prospects are also presented to highlight emerging trends and outlook of SME designs.Yayın A low loss, low voltage and high Q active inductor with multi-regulated cascade stage for RF applications(Institute of Electrical and Electronics Engineers Inc., 2015) Momen, Hadi Ghasemzadeh; Yazgı, Metin; Köprü, RamazanNumerous structural planning of active inductors have been proposed as of not long ago in literature which showing tuning conceivable outcomes, low chip area and offering integration facility, they constitute promising architecture to replace passive inductors in RF circuits. The modified of a conventional active inductor based on Gyrator-C topology consisting of both transconductance stages realized by common-source configuration with multi-regulated cascade stage is presented. The Q factor and value of active inductor is adjusted with bias current and flexible capacitance, respectively. Multi regulated cascade stage is used to boost gain of input impedance and inductor value and decrease series resistance of designed inductor witch caused loss. The circuit is suitable for low voltage operation, high quality factor and low power dissipation. Simulation results are provided for 90 nm TSMC CMOS process with 1 V supply voltage. Self-resonance frequency and power consumption of active inductor is 8.9 GHz and 1.2 mW, respectively.Yayın Teaching aliasing and spectral leakage through the sampling of images(Institute of Electrical and Electronics Engineers Inc., 2019-05-29) Tavşanoğlu, Ahmet VedatAliasing and spectral leakage are artifacts of sampling and rectangular windowing, respectively, whose manifestations are noticed in both the spatial and frequency domains. This paper aims to provide a classroom example which enables the recognition and mathematical interpretation of such phenomena.
