TY - GEN A1 - Tiwari, Krishan Kumar A1 - Grass, Eckhard A1 - Kraemer, Rolf T1 - Noise Performance of Orthogonal RF Beamforming for THz Radio Communications T2 - IEEE Computing and Communication Workshop and Conference (CCWC 2019), Las Vegas, USA, 07 - 09 January 2019 Y1 - 2019 SN - 978-1-7281-0554-3 U6 - https://doi.org/10.1109/CCWC.2019.8666546 PB - IEEE ER - TY - GEN A1 - Tiwari, Krishan Kumar A1 - Sark, Vladica A1 - Grass, Eckhard A1 - Kraemer, Rolf T1 - Monopulse-Based THz Beam Tracking for Indoor Virtual Reality Applications T2 - Mobilkommunikation : Technologien und Anwendungen : Vorträge der 24. ITG-Fachtagung, 15.-16. Mai 2019 in Osnabrück Y1 - 2019 SN - 978-3-8007-4961-4 SP - 10 EP - 13 PB - VDE Verlag GmbH CY - Berlin ; Offenbach ER - TY - GEN A1 - Tiwari, Krishan Kumar A1 - Grass, Eckhard A1 - Thompson, John S. A1 - Kraemer, Rolf T1 - Beam Entropy of 5G Cellular Millimetre-Wave Channels T2 - 90th IEEE Vehicular Technology Conference (VTC-Fall 2019), Honolulu, USA, 22 - 25 September 2019 N2 - In this paper, we obtain and study typical beam entropy values for millimetre-wave (mm-wave) channel models using the NYUSIM simulator for frequencies up to 100 GHz for the fifth generation (5G) and beyond 5G cellular communication systems. The beam entropy is used to quantify sparse MIMO channel randomness in beamspace. Lower relative beam entropy channels are suitable for memory- assisted statistically-ranked (MarS) and hybrid radio frequency (RF) beam training algorithms. High beam entropies can potentially be advantageous for low overhead secured radio communications by generating cryptographic keys based on the channel randomness in beamspace, especially for sparse multiple-input multiple- output (MIMO) channels. Urban microcell (UMi) and urban macrocell (UMa) cellular scenarios have been investigated in this work for 28, 60, 73, and 100 GHz carrier frequencies and the rural macrocell (RMa) scenario for 3.5 GHz. Y1 - 2019 SN - 978-1-7281-1220-6 SN - 978-1-7281-1219-0 SN - 978-1-7281-1221-3 U6 - https://doi.org/10.1109/VTCFall.2019.8891530 SN - 2577-2465 SN - 1090-3038 ER - TY - GEN A1 - Tiwari, Krishan Kumar A1 - Grass, Eckhard A1 - Thompson, John S. A1 - Kraemer, Rolf T1 - Memory-Assisted Statistically-Ranked RF Beam Training Algorithm for Sparse MIMO T2 - 2020 IEEE 91st Vehicular Technology Conference (VTC2020-Spring) Y1 - 2019 SN - 978-1-7281-5207-3 SN - 978-1-7281-4053-7 U6 - https://doi.org/10.1109/VTC2020-Spring48590.2020.9129037 SN - 2577-2465 SN - 1090-3038 ER - TY - GEN A1 - Tiwari, Krishan Kumar A1 - Flisgen, Thomas A1 - Heinrich, Wolfgang A1 - Caire, Giuseppe T1 - Array-fed RIS : validation of Friis-based modeling using full-wave simulations T2 - Proceedings of the 2025 16th German Microwave Conference (GeMiC), March 17-19, 2025, Dresden, Germany N2 - Space-fed large antenna arrays offer superior efficiency, simplicity, and reductions in size, weight, power, and cost (SWaP-C) compared to constrained-feed systems. Historically, horn antennas have been used for space feeding, but they suffer from limitations such as bulky designs, low aperture efficiency (≈ 50%), and restricted degrees of freedom at the continuous aperture. In contrast, planar patch arrays achieve significantly higher aperture efficiency (> 90%) due to their more uniform aperture distribution, reduced weight, and increased degrees of freedom from the discretized aperture. Building on these advantages, we proposed an array-fed Reflective Intelligent Surface (RIS) system, where an active multi-antenna feeder (AMAF) optimizes power transfer by aligning with the principal eigenmode of the AMAF-RIS propagation matrix T. While our previous studies relied on the Friis transmission formula for system modeling, we now validate this approach through full-wave simulations in CST Microwave Studio®. By comparing the Friis-based matrix, TFriis, with the full-wave solution, Tfull.wave, we validate the relevance of the Friis-based modeling for top-level system design. Our findings confirm the feasibility of the proposed AMAF-RIS architecture for next generation communication systems. Y1 - 2025 SN - 978-3-9820397-4-9 U6 - https://doi.org/10.23919/GeMiC64734.2025.10979163 SP - 611 EP - 614 PB - Institute of Electrical and Electronics Engineers (IEEE) CY - New York, NY ER -