Browsing by Author "Yanikomeroglu, H."

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Composite fading model for aerial MIMO FSO links in the presence of atmospheric turbulence and pointing errors
(IEEE, 2021-06) Khallaf, H. S.; Kato, K.; Mohamed, E. M.; Sait, S. M.; Yanikomeroglu, H.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
In this letter, we introduce accurate approximation expressions for composite fading channel model and outage probability of multiple-input multiple-output (MIMO) free space optical (FSO) link between two unmanned aerial vehicles (UAVs) in hovering state. In our derivations, we consider the effects of weather attenuation, random fluctuations in UAVs' positions and orientations, and atmospheric turbulence. Our proposed model is unified with respect to turbulence effect, which means it is valid for different atmospheric turbulence models. We show the accuracy of the proposed model through comparisons with Monte Carlo simulations under different channel conditions.
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Device-to-device communication in 5G cellular networks: challenges, solutions, and future directions
(IEEE, 2014-05) Tehrani, M. N.; Uysal, Murat; Yanikomeroglu, H.; Electrical & Electronics Engineering; UYSAL, Murat
In a conventional cellular system, devices are not allowed to directly communicate with each other in the licensed cellular bandwidth and all communications take place through the base stations. In this article, we envision a two-tier cellular network that involves a macrocell tier (i.e., BS-to-device communications) and a device tier (i.e., device-to-device communications). Device terminal relaying makes it possible for devices in a network to function as transmission relays for each other and realize a massive ad hoc mesh network. This is obviously a dramatic departure from the conventional cellular architecture and brings unique technical challenges. In such a two-tier cellular system, since the user data is routed through other users' devices, security must be maintained for privacy. To ensure minimal impact on the performance of existing macrocell BSs, the two-tier network needs to be designed with smart interference management strategies and appropriate resource allocation schemes. Furthermore, novel pricing models should be designed to tempt devices to participate in this type of communication. Our article provides an overview of these major challenges in two-tier networks and proposes some pricing schemes for different types of device relaying.