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Publication Metadata only Data-driven abnormal behavior detection for autonomous platoon(IEEE Computer Society, 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; 113507Autonomous platoon is a technique where co-operative adaptive cruise control (CACC) enabled vehicles are organized into groups of close following vehicles through communication. It is envisioned that with the increased demand for autonomous vehicles, platoons would be a part of our life in near future. Although many efforts have been devoted to implement the vehicle platooning, ensuring the security remains challenging. Due to lack of security, platoons would be subject to modified packets which can mislead the platoon and result in platoon instability. Therefore, identifying malicious vehicles has become an important requirement. In this paper, we investigate a data-driven abnormal behavior detection approach for an autonomous platoon. We propose a novel statistical learning based technique to detect data anomalies. We demonstrate that shared speed value among platoon members would be sufficient to detect the misbehaving vehicles.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 IEEE 802.11p and visible light hybrid communication based secure autonomous platoon(IEEE-Inst Electrical Electronics Engineers Inc, 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; 113507Autonomous vehicle platoon is an enhancement of autonomous behavior, where vehicles are organized into groups of close proximity through wireless communication. Platoon members mostly communicate with each other via the current dominant vehicular radio frequency (RF) technology, IEEE 802.11p. However, this technology leads security vulnerabilities under various attacks from adversaries. Visible light communication (VLC) has the potential to alleviate these vulnerabilities by exploiting the directivity and impermeability of light. Utilizing only VLC in vehicle platoon, on the other hand, may degrade platoon stability since VLC is sensitive to environmental effects. In this paper, we propose an IEEE 802.11p and VLC-based hybrid security protocol for platoon communication, namely SP-VLC, with the goal of ensuring platoon stability and securing platoon maneuvers under data packet injection, channel overhearing, jamming, and platoon maneuver attacks. We define platoon maneuver attack based on the identification of various scenarios where a fakemaneuver packet is transmitted by amalicious actor. SP-VLC includesmechanisms for the secret key establishment, message authentication, data transmission over both IEEE 802.11p and VLC, jamming detection and reaction to switch to VLC only communication and secure platoon maneuvering based on the joint usage of IEEE 802.11p and VLC. We develop a simulation platform combining realistic vehicle mobility model, realistic VLC and IEEE 802.11p channel models, and vehicle platoon management. We show the functionality of the SP-VLC protocol under all possible security attacks by performing extensive simulations. Ourfindings demonstrate that SP-VLC protocol generates less than 0.1% difference in the speed of and distance between platoon members during security attacks in comparison to 25% and 10% in that of previously proposed IEEE 802.11p and IEEE 802.11p-VLC hybrid protocols, respectively.Publication Open Access Index modulation based coordinate interleaved orthogonal design for secure communications(Institute of Electrical and Electronics Engineers (IEEE), 2021) Yıldırım, İbrahim; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; Özpoyraz, Burak; Faculty Member; Master Student; Department of Electrical and Electronics Engineering; College of Engineering; Graduate School of Sciences and Engineering; 149116; N/AIn this paper, we propose a physical layer security scheme that exploits a novel index modulation (IM) technique for coordinate interleaved orthogonal designs (CIOD). Utilizing the diversity gain of CIOD transmission, the proposed scheme, named CIOD-IM, provides an improved spectral efficiency by means of IM. In order to provide a satisfactory secrecy rate, we design a particular artificial noise matrix, which does not affect the performance of the legitimate receiver, while deteriorating the performance of the eavesdropper. We derive expressions of the ergodic secrecy rate and the theoretical bit error rate upper bound. In addition, we analyze the case of imperfect channel estimation by taking practical concerns into consideration. It is shown via computer simulations that the proposed scheme outperforms the existing IM-based schemes and might be a candidate for future secure communication systems.Publication Open Access Machine learning based channel modeling for Vehicular Visible Light Communication(Institute of Electrical and Electronics Engineers (IEEE), 2021) Department of Electrical and Electronics Engineering; Ergen, Sinem Çöleri; Turan, Buğra; Faculty Member; Other; PhD Student; Department of Electrical and Electronics Engineering; College of Engineering; Graduate School of Sciences and Engineering; 7211; N/AVehicular Visible Light Communication (VVLC) is preferred as a vehicle-to-everything (V2X) communications scheme due to its highly secure, low complexity and radio frequency (RF) interference free characteristics, exploiting the line-of-sight (LoS) propagation of visible light and usage of already existing vehicle light emitting diodes (LEDs). Current VVLC channel models based on deterministic and stochastic methods provide limited accuracy for path loss prediction since deterministic methods heavily depend on site-specific geometry and stochastic models average out the model parameters without considering environmental effects. Moreover, there exists no wireless channel model that can be adopted for channel frequency response (CFR) prediction. In this paper, we propose novel framework for the machine learning (ML) based channel modeling of the VVLC with the goal of improving the model accuracy for path loss and building the CFR model through the consideration of multiple input variables related to vehicle mobility and environmental effects. The proposed framework incorporates multiple measurable input variables, e.g., distance, ambient light, receiver inclination angle, and optical turbulence, with the exploitation of feed forward neural network based multilayer perceptron neural network (MLP-NN), radial basis function neural network (RBF-NN) and decision tree based Random Forest learning methods. The framework also includes data pre-processing step, with synthetic minority over-sampling technique (SMOTE) data balancing, and hyper-parameter tuning based on iterative grid search, to further improve the accuracy. The accuracy of the proposed ML based channel modeling is demonstrated on the real-world VVLC vehicle-to-vehicle (V2V) communication channel data. The proposed MLP-NN, RBF-NN, and Random Forest based channel models generate highly accurate path loss predictions with 3.53 dB, 3.81 dB, 3.95 dB root mean square error(RMSE), whereas the best performing stochastic model based on two-term exponential fitting provides prediction accuracy of 7 dB RMSE. Moreover, MLP-NN and RBF-NN models are demonstrated to predict VVLC CFR with 3.78 dB and 3.60 dB RMSE, respectively.Publication Metadata only Multihop-cluster-based IEEE 802.11p and LTE hybrid architecture for VANET safety message dissemination(Institute of Electrical and Electronics Engineers (IEEE), 2016) N/A; 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; N/A; 7211; 113507Several vehicular ad hoc network (VANET) studies have focused on communication methods based on IEEE 802.11p, which forms the standard for wireless access for vehicular environments. In networks employing IEEE 802.11p only, the broadcast storm and disconnected network problems at high and low vehicle densities, respectively, degrade the delay and delivery ratio of safety message dissemination. Recently, as an alternative to the IEEE 802.11p-based VANET, the usage of cellular technologies has been investigated due to their low latency and wide-range communication. However, a pure cellular-based VANET communication is not feasible due to the high cost of communication between the vehicles and the base stations and the high number of handoff occurrences at the base station, considering the high mobility of the vehicles. This paper proposes a hybrid architecture, namely, VMaSC-LTE, combining IEEE 802.11p-based multihop clustering and the fourth-generation (4G) cellular system, i.e., Long-Term Evolution (LTE), with the goal of achieving a high data packet delivery ratio (DPDR) and low delay while keeping the usage of the cellular architecture at a minimum level. In VMaSC-LTE, vehicles are clustered based on a novel approach named Vehicular Multihop algorithm for Stable Clustering (VMaSC). The features of VMaSC are cluster head (CH) selection using the relative mobility metric calculated as the average relative speed with respect to the neighboring vehicles, cluster connection with minimum overhead by introducing a direct connection to the neighbor that is already a head or a member of a cluster instead of connecting to the CH in multiple hops, disseminating cluster member information within periodic hello packets, reactive clustering to maintain the cluster structure without excessive consumption of network resources, and efficient size-and hop-limited cluster merging mechanism based on the exchange of cluster information among CHs. These features decrease the number of CHs while increasing their stability, therefore minimizing the usage of the cellular architecture. From the clustered topology, elected CHs operate as dual-interface nodes with the functionality of the IEEE 802.11p and LTE interface to link the VANET to the LTE network. Using various key metrics of interest, including DPDR, delay, control overhead, and clustering stability, we demonstrate the superior performance of the proposed architecture compared with both previously proposed hybrid architectures and alternative routing mechanisms, including flooding and cluster-based routing via extensive simulations in ns-3 with the vehicle mobility input from the Simulation of Urban Mobility. The proposed architecture also allows achieving higher required reliability of the application quantified by the DPDR at the cost of higher LTE usage measured by the number of CHs in the network.Publication Metadata only On the performance of MIMO OFDM-based intra-vehicular VLC networks(Institute of Electrical and Electronics Engineers (IEEE), 2016) Narmanloğlu, Ömer; 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; 7211Vehicular hotspots for on-board Internet access using Long Term Evolution (LTE) as the backhaul network has recently gained popularity. Currently, Wi-Fi is the most common technology to provide in-vehicle access, where data has been relayed through on board LTE receiver. Despite its wide acceptance, coexistence and contention based data rate limitations with Wi-Fi necessitates alternatives for in-vehicle data access schemes. This paper investigates the performance of hybrid LTE and visible light communication (VLC) networks using LTE as the backhaul and VLC as the on-board access network.Under the consideration of vehicle interior unique channel characteristics and light emitting diode (LED) deployment flexibility, best transmitter configuration using repetition coding (RC) and spatial multiplexing (SM) multiple input multiple output (MIMO)modes is determined. Proposed configurations based on direct current biased optical orthogonal frequency-division multiplexing(DCO-OFDM) are compared with respect to their bit-error-rate (BER) performances. Furthermore, the performance of intravehicular VLC networks for single and multi-user scenarios is investigated.Publication Metadata only On the reliability analysis of C-V2X Mode 4 for next generation connected vehicle applications(Institute of Electrical and Electronics Engineers (IEEE), 2022) Karaağaç, Sercan; N/A; N/A; N/A; N/A; N/A; Department of Electrical and Electronics Engineering; Reyhanoğlu, Aslıhan; Kar, Emrah; Kümeç, Feyzi Ege; Kara, Yahya Şükür Can; Turan, Buğra; Ergen, Sinem Çöleri; Researcher; Researcher; Researcher; Researcher; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; N/A; N/A; N/A; N/A; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; N/A; N/A; 7211Vehicle-to-Everything Communication (V2X) technologies are provisioned to play an important role in increasing road safety by enabling advanced connected vehicle applications such as cooperative perception, cooperative driving, and remote driving. However, the reliability of the technology is limited mainly due to wireless communication channel characteristics. Therefore, investigation of V2X reliability aspects is crucial to utilize the technology efficiently. In this paper, we provide simulation and measurement-based reliability analysis of Cellular Vehicle-to-Everything (C-V2X) Mode 4 technology for various message sizes and Modulation and Coding Schemes (MCS) selections. We demonstrate that the Packet Delivery Ratio (PDR), a key communication performance metric, heavily depends on message size and selected MCS.Publication Metadata only Performance analysis of OTSM under hardware impairments and imperfect CSI(IEEE-Inst Electrical Electronics Engineers Inc, 2024) Doosti-Aref, Abed; Masouros, Christos; Zhu, Xu; Arslan, Hüseyin; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; Ergen, Sinem Çöleri; Department of Electrical and Electronics Engineering; College of EngineeringOrthogonal time sequency multiplexing (OTSM) has been recently proposed as a single-carrier waveform offering similar bit error rate to orthogonal time frequency space (OTFS) and outperforms orthogonal frequency division multiplexing (OFDM) in doubly-spread channels (DSCs);however, with a much lower complexity making it a potential candidate for 6G wireless networks. In this paper, the performance of OTSM is explored by considering the joint effects of multiple hardware impairments (HWIs) such as in-phase and quadrature imbalance (IQI), direct current offset (DCO), phase noise, power amplifier non-linearity, carrier frequency offset, and synchronization timing offset for the first time in the area. First, the discrete-time baseband signal model is obtained in vector form under all mentioned HWIs. Second, the system input-output relations are derived in time, delay-time, and delay-sequency (DS) domains in which the parameters of all mentioned HWIs are incorporated. Third, analytical expressions are derived for the pairwise and average bit error probability under imperfect channel state information (CSI) as a function of the parameters of all mentioned HWIs. Analytical results demonstrate that under all mentioned HWIs, noise stays additive white Gaussian, effective channel matrix is sparse, DCO appears as a DC signal at the receiver interfering with only the zero sequency, and IQI redounds to self-conjugated sequency interference in the DS domain. Simulation results reveal the fact that by considering the joint effects of all mentioned HWIs and imperfect CSI not only OTSM outperforms OFDM by 29%in terms of energy of bit per noise but it performs same as OTFS in high mobility DSCs. IEEEPublication Metadata only Physical layer implementation of standard compliant vehicular VLC(Institute of Electrical and Electronics Engineers (IEEE), 2016) Narmanloğlu, Ömer; 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; 7211Visible light communication (VLC) has recently gained popularity as a complementary technology to radio frequency (RF) based alternatives for vehicular communications as a low-cost, secure and RF interference free technology. In this paper, we propose IEEE 802.15.7 standard-compliant physical layer (PHY) implementation and experimental evaluation, using commercial off-the-shelf (COTS) automotive light emitting diode (LED) fog light for the purpose of low-latency safety message dissemination. We first show that the standard is applicable to line of sight (LoS) vehicle-to-vehicle (V2V) VLC. We then demonstrate that the proper selection of modulation coding schemes (MCS) plays an important role in order to minimize bit-error-rate (BER) for the reliable transmission with varying inter-vehicle distances. We also addressed the angular limitations of COTS automotive LED light for viable vehicular VLC.