Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7148

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Author: search.filters.author.Altunbas, IbrahimWoS Q: search.filters.wosQuartile.Q1

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  • Article
    Citation - WoS: 1
    Citation - Scopus: 1
    Multi-Haps Thz Satellite Communication: Error and Capacity Analyses Under I/Q Imbalance
    (Ieee-inst Electrical Electronics Engineers inc, 2024) Ahrazoglu, Evla Safahan; Altunbas, Ibrahim; Erdogan, Eylem
    Satellite communication (SatCom) has become an important field of research to accomplish the requirements of next-generation wireless communication systems such as high data rates and capacity while providing global coverage. Besides traditional communication applications, SatCom is gathering more and more attention as it enhances the performance of sensing applications, such as environmental monitoring, atmospheric pollution monitoring, and so on. To deliver worldwide service and improve accurate data collection in sensor networks, high-altitude platform station (HAPS) systems can be employed in SatCom. Moreover, utilizing terahertz (THz) frequencies in HAPS-assisted SatCom systems offers incredibly high bandwidths, enabling extreme data rates and higher resolution in sensing applications. In this article, a THz SatCom system model is considered where K number of HAPS systems are deployed to assist the transmission between a low-Earth-orbit satellite and a ground station by utilizing variable-gain amplify-and-forward (AF) relaying. The symbol error rate (SER) and ergodic capacity analyses are performed in the presence of attenuation depending on the atmospheric conditions, fading, pointing error (PE), and in-phase and quadrature (I/Q) imbalance. Theoretical findings are validated through Monte-Carlo simulations.
  • Article
    Citation - WoS: 4
    Citation - Scopus: 3
    Design of Energy Efficient Multi-Haps Assisted Hybrid Rf/Fso Satellite Communication Systems With Optimal Placement
    (IEEE-Inst Electrical Electronics Engineers Inc, 2025) Ece Turk, Sare; Safahan Ahrazoglu, Evla; Erdogan, Eylem; Altunbas, Ibrahim
    Satellites and high altitude platform station (HAPS) systems are expected to become the key elements of non-terrestrial networks with the recent advances on sixth-generation (6G) wireless networks. In this article, motivated by the mounting interest in HAPS systems both from academia and industry, we propose a multi-HAPS aided optical satellite communication architecture using hybrid radio frequency (RF)/free space optical (FSO) communication to provide enhanced throughput, and reliability. The proposed architecture can be used in railways, transcontinental highways or maritime communications to provide enhanced coverage, throughput and reliability. To quantify the overall performance of the proposed scenario, outage probability, ergodic capacity, throughput, energy efficiency are obtained and validated. Additionally, the impact of outdated channel state information and channel estimation errors are considered, severely affecting the system performance by causing signal-to-noise ratio loss and outage floors. Furthermore, we find optimum HAPS distance and obtain the number of HAPS systems that is required for reliable communications. The results show that serial placement of HAPS systems at optimum distances can enhance the system performance and energy efficiency.