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EDEMEN, Çağatay

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Çağatay

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    FSO-based backhauling for airborne THz base stations
    (IEEE, 2023) Elamassie, Mohammed; Edemen, Çağatay; Uysal, Murat; Electrical & Electronics Engineering; ELAMASSIE, Mohammed; EDEMEN, Çağatay; UYSAL, Murat
    Airborne nodes in the form of high-altitude platform stations (HAPSs) or unmanned aerial vehicles (UAVs) can be used for backhauling and wireless access. In this paper, we investigate the cascaded free space optical (FSO)/terahertz (THz) link in which the FSO link serves as a backhaul between the gateway and the airborne node. In contrast, the THz link provides wireless communication between the airborne node and the user. We present channel models, including the atmospheric attenuation, geometrical loss, and fading effect. The FSO sub-system builds upon intensity-modulation direct-detection (IM/DD), while the THz sub-system employs coherent modulation and demodulation. Under the assumption of decode-and-forward relaying, we derive the end-to-end bit error rate (BER). We present numerical results to demonstrate the performance of cascaded airborne links.
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    Cognitive cooperative MAC with one primary and two secondary users: Achievable rates and optimal power control
    (IEEE, 2014-11) Edemen, Çağatay; Kaya, O.; Electrical & Electronics Engineering; EDEMEN, Çağatay
    We 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.
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    Book ChapterPublicationMetadata only
    IEEE 802.15.7: Visible light communication standard
    (2017-01-01) Uysal, Murat; Edemen, Çağatay; Baykaş, T.; Sarbazi, E.; Shams, P.; Uğurdağ, Hasan Fatih; Celebi, H.; Electrical & Electronics Engineering; UYSAL, Murat; EDEMEN, Çağatay; UĞURDAĞ, Hasan Fatih
    Visible light communications (VLC) use the visible spectrum (wavelengths of 390-750 nm or frequency band of 400-790 THz) and provide wireless communication using omnipresent light-emitting diodes (LEDs). Since the human eye perceives only the average intensity when light changes fast enough, it is possible to transmit data using LEDs without a noticeable effect on the lighting output and the human eye. Simultaneous use of LEDs for both lighting and communications purposes is a sustainable and energy-efficient approach that has the potential to revolutionize how we use light. VLC can be used in a wide range of short- and medium-range communication applications including wireless local, personal, and body area networks (WLAN, WPAN, and WBANs), vehicular networks, and machine-to-machine communication among many others. Besides energy efficiency, VLC offer several other inherent advantages over radio frequency (RF)-based counterparts, such as immunity to electromagnetic interference, operation on unlicensed bands, additional physical security, and a high degree of spatial confinement allowing a high reuse factor.