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    Characterization of terahertz band transmittance from sea-level to drone altitudes
    (Institute of Electrical and Electronics Engineers Inc., 2021) Saeed, Akhtar; Saleem, Ammar; Gürbüz, Özgür; Akkaş, Mustafa Alper
    Terahertz (THz) communications has been recognized as a candidate technology for the next generation networks as the THz band offers large bandwidth and data rates, catering for the problem of spectrum scarcity. However, THz band propagation is highly affected by atmospheric absorption due to water vapor molecules, in addition to the high spread loss. Modeling of the absorption loss is essential for a realistic closed form THz path loss model, which can be employed in link level analysis and formulations. For this purpose, in this paper, we characterize the THz transmittance i.e., absorption gain using the data obtained from Line-by-Line Radiative Transfer Model (LBLRTM) tool, considering the available frequency channels selected via water-filling, altitudes from sea-level to drone altitudes and various transmission ranges. We analyze the modeling of transmittance as a function of: (1) Frequency, (2) Distance and (3) Altitude, using different statistical models including, Polynomial, Exponential and Gaussian models. Numerical results depict that modeling transmittance as a function of distance and altitude are feasible approaches using the exponential and the polynomial models, respectively. This work can be extended to characterize the transmittance for all frequencies over the entire THz band, and also for higher altitudes and longer ranges. © 2021 IEEE.
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    Joint Resource Allocation for Terahertz Band Drone Communications
    (Ieee-Inst Electrical Electronics Engineers Inc, 2024) Saeed, Akhtar; Erdem, Mikail; Saleem, Ammar; Gurbuz, Ozgur; Akkas, Mustafa Alper
    This article proposes a joint resource allocation approach for Terahertz (THz) band (0.75-4.4 THz) drone-to-drone communications, studying spectrum and power allocation together with antenna beamwidth adjustment. Considering various drone (mis)alignment and mobility scenarios under a 3D sectored antenna model, the capacity of the proposed spectrum allocation scheme, MaxActive, is compared to existing Common Flat Band (CFB) and standard (STD) schemes, each with water-filling (WF) and equal power (EP) allocations. Results show that up to 6 orders of magnitude improvements are observed with beamwidth optimization, and MaxActive with EP performs close to CFB and STD schemes with WF in all scenarios, even under realistic beam misalignment fading instances (low and high). For drone-to-drone communications, our results prove that the THz band can provide high capacity, in the order of Tbps, which can be preserved well with beam alignment/adjustment. Evaluating also the complexity of all considered resource allocation techniques, it is concluded that MaxActive with EP allocation stands out as the most feasible scheme in terms of practical implementation with the best performance.