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Publication Metadata only Compressed training adaptive MIMO equalization(IEEE, 2016) N/A; Department of Electrical and Electronics Engineering; Yılmaz, Baki Berkay; Erdoğan, Alper Tunga; Researcher; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 41624This article proposes an adaptive equalization framework for flat fading multi-input multi-output(MIMO) systems, where the main goal is to significantly reduce the number of training symbols. The proposed approach exploits the special boundedness property of digital communication signals along with training symbols to adapt receiver equalizer filter. The corresponding framework is built upon some convex settings where the infinity norm is used to utilize the special constellation structure for the efficient adaptation process. As a fundamental result, through the duality between l(infinity) and l(1) norms, the proposed approach establishes an interesting link between adaptive equalization problem and compressed sensing problems. Using this link, the aim of the proposed optimization settings can be viewed as achieving the desired sparseness of the perfect equalization channel with compressed amount of training symbols. Based on this connection, we can prescribe that the training size is on the order of logarithm of the number of sources without any prior sparsity assumption on the wireless channel model. This promises a significant reduction in training symbols especially for the base stations employing very large number of antennas such as Massive MIMO applications. The numerical examples verify the analytical results and demonstrate the practical benefits of the proposed approach.Publication Metadata only Cooperative MIMO-OFDM based inter-vehicular visible light communication using brake lights(Elsevier, 2018) Narmanlıoğlu, Omer; T; Uysal, Murat; N/A; Department of Electrical and Electronics Engineering; Turan, Buğra; Ergen, Sinem Çöleri; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 7211Inter-vehicular connectivity to enhance road safety and support highly autonomous driving is increasingly becoming popular. Despite the prevalent works on radio-frequency (RF) based vehicular communication schemes, visible light communication (VLC) is considered to be a promising candidate for vehicular communications due to its low complexity and RF interference-free nature. Deployment of multiple light emitting diodes (LEDs) enables multiple-input multiple-output (MIMO) transmission in the context of vehicular VLC. This paper investigates applicability of both point-to-point (direct) vehicular VLC and decode-and-forward relaying based cooperative vehicular VLC including relay terminals between source and destination terminals to enhance road safety based on real world measurements. We consider direct current biased optical orthogonal frequency division multiplexing (DCO-OFDM) based MIMO transmission scheme and evaluate the performances of different MIMO modes including repetition code (RC) and spatial multiplexing (SM), different modulation orders with different transmitter receiver selection mechanisms to support line-of-sight (LoS) and beyond LoS multi-hop vehicular VLC. The results reveal that the selection of the closest transmitters to the receivers provides better performance due to high signal-to-noise-ratio requirements for RC mode whereas SM suffers from channel correlation. Usage of all possible transmitters does not always yield better performance due to the power division at the transmitter side. on the other hand, the performance of RC shows more degradation on higher-order modulations that are required to yield the same throughput with SM. Therefore, considering the higher order modulation requirement for RC based VLC, SM is concluded to be a favorable MIMO scheme for cooperative vehicular VLC. We further demonstrate the benefits of multi-hop transmission over direct transmission with respect to different number of relay vehicles as a consequence of varying inter-vehicular distances between source and destination vehicles.Publication Metadata only Data-driven anomaly detection in autonomous platoon(Institute of Electrical and Electronics Engineers (IEEE), 2018) N/A; Department of Electrical and Electronics Engineering; Department of Computer Engineering; Uçar, Seyhan; Ergen, Sinem Çöleri; Özkasap, Öznur; PhD 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; 7211; 113507Technology brings autonomous vehicles into a reality where vehicles cruise themselves without human input. Vehicular platoon, on the other hand, is a group of autonomous vehicles that are organized into close proximity through wireless communication. In an autonomous platoon, vehicles cooperatively send data to each other to adjust their speed and distance to the leader, the first vehicle in the platoon. However, this cooperative data exchange can lead to security risks. A misbehaving platoon member could alter the data packets which may cause platoon instability. Therefore, identifying the modified packets has become an important requirement. In this paper, we investigate data-driven anomaly detection mechanisms for the autonomous platoon. We propose a novel statistical learning based technique to detect the modified packets and misbehaving vehicles. We demonstrate that the distance change to the leader would be sufficient to detect anomalies and misbehavior.Publication Metadata only Delay constrained energy minimization in UWB wireless networks(Institute of Electrical and Electronics Engineers (IEEE), 2013) N/A; Department of Electrical and Electronics Engineering; Şadi, Yalçın; Ergen, Sinem Çöleri; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; 246556; 7211We study the optimal power control, rate adaptation and scheduling for energy minimization subject to delay, traffic demand, transmit power and SNIR constraints in Ultra-Wideband wireless networks. We first show that power control is not required for delay constrained energy minimization. We then formulate optimal scheduling problem as an exponential size Linear Programming (LP) problem for which we propose the Pricing Minimization based Column Generation Method (PMCGM). PM-CGM decomposes the exponential size LP problem into two sub-problems Restricted Master Problem (RMP) and Pricing Problem (PP) and solves it iteratively. We solve the corresponding delay minimization problem for the initialization of the RMP and propose a pricing minimization based polynomial time algorithm to solve the non-linear integer PP formulation. Simulations illustrate that PM-CGM algorithm decreases the runtime required to solve the large scale LP problem considerably while performing very close-to-optimal for different network scenarios.Publication Metadata only Distributed management of service-enabled flow-paths across multiple SDN domains(IEEE, 2015) Civanlar, Seyhan; Lokman, Erhan; Kaytaz, Bülent; Department of Electrical and Electronics Engineering; Tekalp, Ahmet Murat; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 26207Future Internet may be comprised of interconnected multiple software-defined networks (SDN), where each domain is administered by a different controller or control plane. Provisioning of an end-to-end flow-path across such a network with specific service levels requires collaboration between domain controllers across control planes. A service-enabled flow-path shall be quality of service (QoS) enabled, reliable and/or secure, which requires a transport path with certain quantitative service level requirements such as high throughput, low packet loss, or high availability. Each SDN controller can autonomously determine such end-to-end flow-paths when all other SDN controllers periodically advertise to other controllers its available service-enabled paths. Doing so, each SDN controller is presented with several service-enabled path alternatives, crossing other domains, to choose from. We propose a multi-domain SDN controller design, wherein each SDN controller shares its network's "summarized" topology of service-enabled paths with other SDN controllers, such that all domains (controllers) have real-time autonomous decision making capability for end-to-end flow-path selection. We also describe how an SDN controller can reserve and release a flow traversing other SDN domains.Publication Metadata only Distributed-collaborative managed dash video services(Institute of Electrical and Electronics Engineers (IEEE), 2017) N/A; N/A; Department of Electrical and Electronics Engineering; Şahin, Kemal Emrecan; Bağcı, Kadir Tolga; Tekalp, Ahmet Murat; Master 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; 26207We propose a new distributed-collaborative managed DASH video service architecture over software defined networks (SDN) that enables fair and stable video quality to heterogeneous resolution clients. The proposed service is managed by the video service provider (VSP) in collaboration with the network service provider (NSP), where groups of clients sharing a network slice with a reserved throughput collaborate with each other to compute their own fair-share bitrates. Our novel distributed service architecture allows each client to share its buffer status with other clients in the same collaboration group so that each client can estimate a group-buffer-status aware fair-share bitrate, enforce this rate by TCP receive-window size control over a network slice reserved for the group, and perform application-level DASH video rate adaptation that is consistent with this enforced fair bitrate. Experimental results show that the proposed collaborative video service outperforms the traditional competitive DASH clients in terms of (i) minimizing quality fluctuations per client, (ii) fairness among heterogeneous DASH clients, and (iii) maximizing the total goodput of reserved network slice.Publication Metadata only Dual channel visible light communications for enhanced vehicular connectivity(IEEE Computer Society, 2016) N/A; N/A; Department of Electrical and Electronics Engineering; Department of Computer Engineering; Turan, Buğra; Uçar, Seyhan; Ergen, Sinem Çöleri; Özkasap, Öznur; PhD Student; PhD Student; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Department of Computer Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; N/A; 7211; 113507Visible Light Communication (VLC) has recently been proposed as a low-cost and low-complexity technology for vehicular communications. In this paper, we propose the usage of dual channel VLC with the goal of providing enhanced vehicular connectivity to disseminate safety-critical messages and perform an experimental study to determine the spatial and angular limits of an off-the-shelf automotive Light Emitting Diode (LED) fog light. Single channel VLC refers to the independent transmission of different data packets from each LED fog light, while the dual channel VLC offers the concurrent transmission of the same data packet from both lights. There is a trade-off between increasing the angular limitation and the performance of dual channel VLC, which needs to be experimentally evaluated to identify its efficient usage. We first show the dependency of the received optical power of single channel VLC on the angle and distance, and demonstrate that Lambertian model does not represent the automotive LED fog light radiation pattern accurately. We then demonstrate that dual channel usage increases the angular limitation by up to 10° compared to the single channel VLC. We also show that dual channel improves the packet delivery error rate performance at only short distances due to the photodiode (PD) saturation led by light intensity overlapping at higher distances.Publication Metadata only Dynamic control plane for sdn at scale(IEEE-Inst Electrical Electronics Engineers Inc, 2018) Görkemli, Burak; Tatlıcıoğlu, Sinan; Civanlar, Seyhan; Lokman, Erhan; Department of Electrical and Electronics Engineering; Tekalp, Ahmet Murat; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 26207As SDN migrates to wide area networks and 5G core networks, a scalable, highly reliable, low latency distributed control plane becomes a key factor that differentiates operator solutions for network control and management. In order to meet the high reliability and low latency requirements under time-varying volume of control traffic, the distributed control plane, consisting of multiple controllers and a combination of out-of-band and in-band control channels, needs to be managed dynamically. To this effect, we propose a novel programmable distributed control plane architecture with a dynamically managed in-band control network, where in-band mode switches communicate with their controllers over a virtual overlay to the data plane with dynamic topology. We dynamically manage the number of controllers, switches, and control flows assigned to each controller as well as traffic over control channels achieving both controller and control traffic load-balancing. We introduce "control flow table" (rules embedded in the flow table of a switch to manage in-band control flows) in order to implement the proposed distributed dynamic control plane. We propose methods for off-loading congested controllers and congested in-band control channels using control flow tables. A validation test-bed and experimental results over multiple topologies are presented to demonstrate the scalability and performance improvements achieved by the proposed dynamic control plane management procedures when the controller CPU and/or availability or throughput of in-band control channels becomes bottlenecks.Publication Metadata only Effects of transmit beamforming on the capacity of multi-hop MIMO relay channels(IEEE, 2007) Yılmaz, Erhan; Department of Electrical and Electronics Engineering; Sunay, Mehmet Oğuz; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; N/AIn this paper we investigate multi-hop fading relay channels where the source, the destination and the multiple relay nodes are all equipped with multiple antennas. We study the ergodic capacities of multiple relay networks based on Amplify-and-Forward (AF) and Decode-and-Forward (DF) relaying modes. We examine multi-user beamforming (MU-BF), where each data stream is assumed to be matched to a specified relay node, based on the conventional eigen-mode transmission for both modes, and derive ergodic capacity expressions. We also examine the impact of the number of selected relay nodes on the network capacity both for modes of relaying. We show that by using MU-BF at the source node and a maximum number of relay nodes selected for cooperation, the network gains from multiplexing, while beyond that number of cooperating relay nodes, it only gains from relay selection.Publication Metadata only Employing 60 GHz ISM band for 5G wireless communications(IEEE, 2014) Fadel, Etimad; N/A; Department of Electrical and Electronics Engineering; Yılmaz, Türker; Akan, Özgür Barış; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 6647Wireless data traffic is continuously increasing due to the steady rise in both connected device number and traffic per device. Wireless networks, traditionally confined below 6 giga-hertz, are getting clogged and unable to satisfy the ever-increasing demands of its users. Already aware of this, telecommunications industry and academia have been working on solutions. One of the main methods for throughput increase is operation bandwidth expansion; however, sufficient spectrum is not available within the conventional frequencies. Following various considerations, 60 GHz industrial, scientific and medical radio band has been selected as the new spectrum to be utilized and wireless personal and local area network standards for the band are already completed. In line with the stated developments, this paper proposes the use of 60 GHz band for the fifth generation (5G) communication systems. After very briefly setting the scene of the current wireless communication networks, the physical layer properties of the 60 GHz band are presented. A representative indoor simulation between the fourth generation and proposed 5G cases is set and performed. The results are assessed and compared before concluding the paper.