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Publication Metadata only 3DTV and 3D video communications(Assoc Computing Machinery, 2010) Department of Electrical and Electronics Engineering; Tekalp, Ahmet Murat; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 26207With wider availability of low cost multi-view cameras, 3D displays, and broadband communication options, 3D media is destined to move from the movie theater to home and mobile platforms. In the near term, popular 3D media will most likely be in the form of stereoscopic video with associated spatial audio. Recent trials indicate that consumers are willing to watch stereoscopic 3D media on their TVs, laptops, and mobile phones. While it is possible to broadcast 3D stereoscopic media (two-views) over digital TV platforms today, streaming over IP will provide a more flexible approach for distribution of 3D media to users with different connection bandwidths and different 3D displays. In the intermediate term, free-view 3D video and 3DTV with multi-view capture are next steps in the evolution of 3D media technology. Recent free-view 3D auto-stereoscopic displays can display multi-view video, ranging from 5 to 200 views. Transmission of multi-view 3D media, via broadcast or on-demand, to end users with varying 3D display terminals and bandwidths is one of the biggest challenges to realize the vision of bringing 3D media experience to the home and mobile devices. This requires flexible rate-scalable, resolution-scalable, view-scalable, view-selective, and packet-loss resilient transport methods. In this talk, first I will briefly review the state of the art in 3D video formats, coding methods, IP streaming protocols and streaming architectures. We will then take a look at 3D video transport options. There are two main platforms for 3D broadcasting: standard digital television (DTV) platforms and the IP platform. I will summarize the approach of European project DIOMEDES which is developing novel methods for adaptive streaming of multi-view video over a combination of DVB and IP platforms. I will also summarize additional challenges associated with real-time interactive 3D video communications for applications such as 3D telepresence. Finally, open research challenges for the long term vision of haptic video and holographic 3D video will be presented.Publication Metadata only A communication theoretical analysis of synaptic multiple-access channel in hippocampal-cortical neurons(IEEE-Inst Electrical Electronics Engineers Inc, 2013) N/A; N/A; Department of Electrical and Electronics Engineering; Malak, Derya; Akan, Özgür Barış; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 6647Communication between neurons occurs via transmission of neural spike trains through junctional structures, either electrical or chemical synapses, providing connections among nerve terminals. Since neural communication is achieved at synapses, the process of neurotransmission is called synaptic communication. Learning and memory processes are based on the changes in strength and connectivity of neural networks which usually contain multiple synaptic connections. In this paper, we investigate multiple-access neuro-spike communication channel, in which the neural signal, i.e., the action potential, is transmitted through multiple synaptic paths directed to a common postsynaptic neuron terminal. Synaptic transmission is initiated with random vesicle release process from presynaptic neurons to synaptic paths. Each synaptic channel is characterized by its impulse response and the number of available postsynaptic receptors. Here, we model the multiple-access synaptic communication channel, and investigate the information rate per spike at the postsynaptic neuron, and how postsynaptic rate is enhanced compared to single terminal synaptic communication channel. Furthermore, we analyze the synaptic transmission performance by incorporating the role of correlation among presynaptic terminals, and point out the postsynaptic rate improvement.Publication Metadata only A communication theoretical modeling and analysis of underwater magneto-inductive wireless channels(Ieee-Inst Electrical Electronics Engineers Inc, 2012) N/A; Department of Electrical and Electronics Engineering; Gülbahar, Burhan; Akan, Özgür Barış; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; 234525; 6647Underwater physical medium is a challenging environment for communication using radio frequency (RF) or acoustic waves due to strong attenuation, delay, multi-path fading, power and cost limitations. Discovered a century ago, magneto-inductive (MI) communication technique stands as a strong alternative paradigm due to its independence of environmental impairments including multi-path fading, dynamic channels and high propagation delays experienced by acoustic waves. Furthermore, MI technique yields networking solutions exploiting low-cost, easily-deployable and flexible antenna structures, and the possibility of forming networks of magnetic waveguides defeating path loss. In this work, highly power efficient and fully connected underwater communication networks (UWCNs) composed of transceiver and relay induction coils are presented. Three dimensional (3D) UWCNs are analysed in terms of basic communication metrics, i.e, signal-to-noise ratio, bit-error rate, connectivity and communication bandwidth. The performance studies of realistic 3D networks covering hundreds of meters sea depths and a few km(2) areas show that fully connected multi-coil networks with communication bandwidths extending from a few to tens of KHz are possible. Furthermore, the performance dependence on coil properties and network size is theoretically modelled. Results show that MI wireless communication is a promising alternative for UWCNs and future research challenges are pointed out.Publication Metadata only A correlation-based and spectrum-aware admission control mechanism for multimedia streaming in cognitive radio sensor networks(Wiley, 2017) Hosseini, Elahe S.; Esmaeelzadeh, Vahid; Berangi, Reza; Department of Electrical and Electronics Engineering; Akan, Özgür Barış; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 6647Bandwidth management and traffic control are critical issues to guarantee the quality of service in cognitive radio networks. This paper exploits a network load refinement approach to achieve the efficient resource utilization and provide the required quality of service. A connection admission control approach is introduced in cognitive radio multimedia sensor networks to provide the data transmission reliability and decrease jitter and packet end-to-end delay. In this approach, the admission of multimedia flows is controlled based on multimedia sensors' correlation information and traffic characteristics. We propose a problem, connection admission control optimization problem, to optimize the connection admission control operation. Furthermore, using a proposed weighting scheme according to the correlation of flows issued by multimedia sensors enables us to convert the connection admission control optimization problem to a binary integer-programming problem. This problem is a kind of a Knapsack problem that is solved by a branch and bound method. Simulation results verify the proposed admission control method's effectiveness and demonstrate the benefits of admission control and traffic management in cognitive radio multimedia sensor networks.Publication Metadata only A cross-layer design for Qos support in cognitive radio sensor networks for smart grid applications(Ieee, 2012) Shah, Ghalib Asadullah; Güngör, Vehbi Çağrı; Department of Electrical and Electronics Engineering; Akan, Özgür Barış; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 6647In this paper, we propose a cross-layer design to meet the QoS requirements for smart grids employing the cognitive radio sensor networks for their control and monitoring operations. Existing routing protocols pertaining to QoS support are not able to simultaneously handle traffic of different characteristics present in smart grids. Therefore, considering the traffic heterogeneity of smart grid applications exhibiting diverse QoS requirements, a set of priority classes is defined in order to differentiate the traffic for the respective service. Specifically, the problem is formulated as a weighted network utility maximization (WNUM) whose objective is to maximize the weighted sum of flows service. A cross-layer heuristic solution is provided to solve the utility optimization problem by performing joint routing, dynamic spectrum allocation and medium access. Performance of the proposed protocol is evaluated using ns-2, which shows that the number of flows belonging to each class are served according to their weight fraction with their respective data rate, latency and reliability requirement.Publication Metadata only A DASH7-based power metering system(IEEE, 2015) Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Çetinkaya, Oktay; Akan, Özgür Barış; Other; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; College of Engineering; N/A; 6647Considering the inability of the existing energy resources to satisfy the current needs, the right and efficient. use of the energy has become compulsory. To make energy sustainability permanent, management and planning activities should be carried out by arranging the working hours and decreasing the energy wasting. For all these, power metering, managing and controlling systems or plugs has been proposed in recent efforts. Starting from this point, a new DASH7-based Smart Plug (D7SP) is designed and implemented to achieve a better structure compared to ZigBee equipped models and reduce the drawbacks of current applications. DASH7 technology reaches nearly 6 times farther distances in comparison with 2.4 GHz based protocols and provides multi-year battery life as a result of using limited energy during transmission. Performing in the 433 MHz band prevents the possible interference from overcrowded 2.4 GHz and the other frequencies which helps to gather a more reliable working environment. To shorten the single connection delays and human oriented failures, the MCU was shifted directly into the plug from the rear-end device. Working hours arrangement and standby power cutting off algorithms are implemented in addition to these energy saving targeted improvements to enhance more efficient systems. With the collaboration of the conducted hardware and software oriented adjustments and DASH7-based improvements, a more reliable, mobile and efficient system has been obtained in this work.Publication Open Access A hybrid architecture for federated and centralized learning(Institute of Electrical and Electronics Engineers (IEEE), 2022) Elbir, Ahmet M.; Papazafeiropoulos, Anastasios K.; Kourtessis, Pandelis; Chatzinotas, Symeon; Department of Electrical and Electronics Engineering; Ergen, Sinem Çöleri; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 7211Many of the machine learning tasks rely on centralized learning (CL), which requires the transmission of local datasets from the clients to a parameter server (PS) entailing huge communication overhead. To overcome this, federated learning (FL) has been suggested as a promising tool, wherein the clients send only the model updates to the PS instead of the whole dataset. However, FL demands powerful computational resources from the clients. In practice, not all the clients have sufficient computational resources to participate in training. To address this common scenario, we propose a more efficient approach called hybrid federated and centralized learning (HFCL), wherein only the clients with sufficient resources employ FL, while the remaining ones send their datasets to the PS, which computes the model on behalf of them. Then, the model parameters are aggregated at the PS. To improve the efficiency of dataset transmission, we propose two different techniques: i) increased computation-per-client and ii) sequential data transmission. Notably, the HFCL frameworks outperform FL with up to 20% improvement in the learning accuracy when only half of the clients perform FL while having 50% less communication overhead than CL since all the clients collaborate on the learning process with their datasets.Publication Metadata only A low-complexity solution to angular misalignments in molecular index modulation(IEEE, 2019) Çelik, Ahmet; Gürsoy, Mustafa Can; Pusane, Ali Emre; Tuğcu, Tuna; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 149116Multiple-input multiple-output (MIMO) transmission approaches have been recently considered in the context of molecular communications due to desirable improvements they provide in terms of communication efficiency. Among these methods, molecular index modulation (molecular-IM) schemes yield a significant improvement in throughput and show promising results for future molecular MIMO research. However, existing molecular-IM methods rely on perfect spatial alignment between corresponding antennas, which may not be the case in a possible practical scenario. Motivated by this practical constraint, this study proposes a novel receiver design for molecular-IM. The proposed decoder is an augmented version of the maximum count decoder (MCD) and operates by merging MCD with a simple linear combining technique. Our numerical results show that the proposed approach yields a desirable robustness against antenna misalignments while still maintaining a simplistic receiver structure.Publication Metadata only A mechanical transduction-based molecular communication receiver for ınternet of nano things (IoNT)(Assoc Computing Machinery, 2021) N/A; Department of Electrical and Electronics Engineering; Aktaş, Dilara; Akan, Özgür Barış; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 6647Molecular conununication (MC) is one of the most promising technology to enable nanonetworks. Despite many aspects of MC have been investigated broadly, the physical design of the MC receiver has gained little interest. High-performance MC receivers based on bioFETs are proposed and extensively analyzed. However, they have some challenges such as limited detection with charged molecules, Debye screening, and the need for reference electrodes. To overcome these shortcomings, we propose a mechanical-based transducing scheme. In particular, we focus on a Flexure field-effect transistor (FET)-based MC receiver architecture, which provides exponentially high sensitivity by utilizing a nonlinear electromechanical coupling. In addition, the detection of neutral molecules with much simpler instrumentation is possible. In this paper, we analyze its fundamental performance metrics; sensitivity, noise power, signal-to-noise ratio, and the symbol error probability, from an MC theoretical perspective.Publication Metadata only A moving window approach for blind equalization using subgradient projections(IEEE, 2004) N/A; N/A; Department of Electrical and Electronics Engineering; Kızılkale, Can; Erdoğan, Alper Tunga; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 41624A novel blind equalization method based on a subgradient search over a convex cost surface is examined under a noisy channel and a modification is proposed. This is an alternative to the existing iterative blind equalization approaches such as Constant Modulus Algorithm (CMA) which mostly suffer from the convergence problems caused by their non-convex cost functions. The proposed method is an iterative algorithm, for both real and complex constellations, with a very simple update rule that minimizes the l(infinity) norm of the equalizer output under a linear constraint on the equalizer coefficients. The subgradient based algorithm has a fast convergence behavior attributed to the convex l(infinity) cost surface. A moving window based approach is used in this algorithm to both decrease algorithm's complexity and increase its immunity to noise. / Bu makalede alt-bayır izdüşümleri kullanılarak yapılan kör eşitleme metodunun gürültülü bir kanal için performansı incelenmiş ve bu performansın arttırılması için bir öneride bulunulmuştur. Bu algoritma daha önce önerilen sabit genlik algoritmasi(CMA) gibi özyineli yöntemlere bir alternatif olarak sunulmaktadır. Bilindiği gibi daha once sunulan algoritmalar dışbükey olmayan maliyet işlevlerinden dolayı yakınsallık problemi yaşamaktadırlar. Önerilen yöntem, hem gerçek hem de karmaşık burçlar (constellation) için, denkleştirici katsayıları üzerindeki doğrusal bir kısıt altında denkleştiricinin çıktısını l(infinity), normunu enküçültme esasına dayalı, basit bi güncelleme yapısına sahip özyinelemeli bir algoritmadır. Bu algoritma l(infinity) maliyet yüzeyinin karakterinden dolayı hızlı yakınsama davranışına sahiptir. Algoritmanin hem karmaşıklığını azaltacak hem de gürültüye karşı bağışıklığını yükseltecek hareketli pencereye dayalı bir yapı kullanılmıştır.