arXiv subjects

Bora Bozkurt

Publications and source records attributed to Bora Bozkurt.

5 recordsLinked to original sources

arXiv2026

Radar-Assisted Beam Management Framework for mmWave NTNs: Overhead Reduction and Physical Layer Security Application

Fast and low-overhead beam management is a critical requirement for the practical deployment of non-terrestrial networks (NTNs) operating at millimeter-wave and higher frequencies. In this paper, we propose a radar-assisted beam selection framework for NTNs that limits the set of candidate beams by utilizing spatial sensing information such as the angle-of-departure (AoD) and distance estimations. To provide theoretical insight into the expected worst-case overhead, we conduct a probabilistic analysis under idealized conditions, where an approximation of the worst-case beam selection overhead is proposed and its statistics are derived under Gaussian error. Additionally, the proposed framework is applied to a physical-layer security (PLS) scenario by leveraging the radar's capability to detect passive targets that represent unintended users. The simulation results show that the unintended user's power is suppressed below -135 dBm, while an additional beamforming gain of roughly 2 dB is attained for the legitimate users.

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arXiv2025

Toward 6G Downlink NOMA: CRC-Aided GRAND for Noise-Resilient NOMA Decoding in Beyond-5G Networks

Non-Orthogonal Multiple Access (NOMA) technology has emerged as a promising technology to enable massive connectivity and enhanced spectral efficiency in next-generation wireless networks. In this study, we propose a novel two-user downlink power-domain NOMA framework that integrates a Cyclic Redundancy Check (CRC)-aided Guessing Random Additive Noise Decoding (GRAND) with successive interference cancellation (SIC). Unlike conventional SIC methods, which are susceptible to error propagation when there is low power disparity between users, the proposed scheme leverages GRAND's noise-centric strategy to systematically rank and test candidate error patterns until the correct codeword is identified. In this architecture, CRC is utilized not only to detect errors but also to aid the decoding process, effectively eliminating the need for separate Forward Error Correction (FEC) codes and reducing overall system overhead. Furthermore, the strong user enhances its decoding performance by applying SIC that is reinforced by GRAND-based decoding of the weaker user's signals, thereby minimizing error propagation and increasing throughput. Comprehensive simulation results over both Additive White Gaussian Noise (AWGN) and Rayleigh fading channels, under varying power allocations and user distances, show that the CRC-aided GRAND-NOMA approach significantly improves the Bit Error Rate (BER) performance compared to state-of-the-art NOMA decoding techniques. These findings underscore the potential of integrating universal decoding methods like GRAND into interference-limited multiuser environments for robust future wireless networks.

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arXiv2025

Theoretical and Experimental Assessment of Large Beam Codebook at mmWave Devices: How Much is Enough?

Modern millimeter wave (mmWave) transceivers come with a large number of antennas, each of which can support thousands of phase shifter configurations. This capability enables beam sweeping with fine angular resolution, but results in large codebook sizes that can span more than six orders of magnitude. On the other hand, the mobility of user terminals and their randomly changing orientations require constantly adjusting the beam direction. A key focus of recent research has been on the design of beam sweeping codebooks that balance a trade-off between the achievable gain and the beam search time, governed by the codebook size. In this paper, we investigate the extent to which a large codebook can be reduced to fewer steering vectors while covering the entire angular space and maintaining performance close to the maximum array gain. We derive a closed-form expression for the angular coverage range of a steering vector, subject to maintaining a gain loss within $\gamma$ dB (e.g., 2\, dB) with respect to the maximum gain achieved by an infinitely large codebook. We demonstrate, both theoretically and experimentally, that a large beam-steering codebooks (such as the $1024^{16}$ set considered in our experiment) can be reduced to just a few steering vectors. This framework serves as a proof that only a few steering vectors are sufficient to achieve near-maximum gain, challenging the common belief that a large codebook with fine angular resolution is essential to fully reap the benefits of an antenna array.

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arXiv2024

Beam Codebook Refinement for mmWave Devices with Random Orientations: Concept and Experimental Validation

There is a growing interest in codebook-based beam-steering for millimeter-wave (mmWave) systems due to its potential for low complexity and rapid beam search. A key focus of recent research has been the design of codebooks that strike a trade-off between achievable gain and codebook size, which directly impacts beam search time. Statistical approaches have shown promise by leveraging the likelihood that certain beam directions (equivalently, sets of phase-shifter configurations) are more probable than others. Such approaches are shown to be valid for static, non-rotating transmission stations such as base stations. However, for the case of user terminals that are constantly changing orientation, the possible phase-shifter configurations become equally probable, rendering statistical methods less relevant. On the other hand, user terminals come with a large number of possible steering vector configurations, which can span up to six orders of magnitude. Therefore, efficient solutions to reduce the codebook size (set of possible steering vectors) without compromising array gain are needed. We address this challenge by proposing a novel and practical codebook refinement technique, aiming to reduce the codebook size while maintaining array gain within $γ$ dB of the maximum achievable gain at any random orientation of the user terminal. We project that a steering vector at a given angle could effectively cover adjacent angles with a small gain loss compared to the maximum achievable gain. We demonstrate experimentally that it is possible to reduce the codebook size from $1024^{16}$ to just a few configurations (e.g., less than ten), covering all angles while maintaining the gain within $γ=3$ dB of the maximum achievable gain.

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arXiv2024

Unlocking Potential: Integrating Multihop, CRC, and GRAND for Wireless 5G-Beyond/6G Networks

As future wireless networks move towards millimeter wave (mmWave) and terahertz (THz) frequencies for 6G, multihop transmission using Integrated Access Backhaul (IABs) and Network-Controlled Repeaters (NCRs) will be highly essential to overcome coverage limitations. This paper examines the use of Guessing Random Additive Noise (GRAND) decoding for multihop transmissions in 3GPP networks. We explore two scenarios: one where only the destination uses GRAND decoding, and another where both relays and the destination leverage it. Interestingly, in the latter scenario, the Bit Error Rate (BER) curves for all hop counts intersect at a specific Signal-to-Noise Ratio (SNR), which we term the GRAND barrier. This finding offers valuable insights for future research and 3GPP standard development. Simulations confirm the effectiveness of GRAND in improving communication speed and quality, contributing to the robustness and interconnectivity of future wireless systems, particularly relevant for the migration towards mmWave and THz bands in 6G networks. Finally, we investigate the integration of multihop transmission, CRC detection, and GRAND decoding within 3GPP networks, demonstrating their potential to overcome coverage limitations and enhance overall network performance.

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