Yazar "Yazgan, Mehmet" seçeneğine göre listele

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    Comparison of ofdm and lfm waveform schemes for ranging: a correlation perspective
    (2024) Yazgan, Mehmet; Arslan, Hüseyin; Vakalis, Stavros
    Orthogonal frequency division multiplexing (OFDM) waveforms have been employed in communications systems for years and are the key waveform candidates for beyond-fifth-generation (5G) communication networks. In this paper, we compare OFDM waveforms to linear frequency- modulated (LFM) waveforms which are widely exploited in modern radar systems. We discuss the utility of OFDM waveforms for joint communications and sensing but also provide a comparison between the two in terms of their correlation properties. OFDM waveforms exhibit improved cross-correlation properties compared to LFM waveforms which can yield excellent resistance to interference between multiple radar transmitters without any cooperation. We express the theory behind our work and include simulations supporting our claims.
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    High-accuracy indoor ranging using microwave ofdm signals
    (2024) Yazgan, Mehmet; Arslan, Hüseyin; Vakalis, Stavros
    High-accuracy wireless ranging and positioning becomes necessary in many applications, and while many waveforms promise high accuracy, their performance in cluttered environments is not optimal. This article confers about the potential of high-accuracy wireless ranging using orthogonal frequency-division multiplexing (OFDM) signals. The excellent correlation properties of OFDM signals for high-accuracy ranging in real-life environments are discussed and the Cramer-Rao lower bound (CRLB) is derived for OFDM ranging independent of the transmitted information. Simulation results and experimental measurements at a carrier frequency of 1.4 GHz with 200 MHz of bandwidth are included. Range estimation is demonstrated with a standard deviation of 1.6 mm in a realistic laboratory environment with no anechoic walls.
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    Investigation of ofdm signals for microwave ranging
    (2024) Yazgan, Mehmet; Arslan, Hüseyin; Vakalis, Stavros
    Wireless ranging and positioning plays a pivotal role across numerous applications, encompassing wireless networks, robotics, navigation, and distributed wireless systems. A common limitation encountered in many ranging algorithms relates to the requirement for waveforms with sufficiently wide bandwidth to attain precise ranging accuracy. In this study, we investigate the applicability of orthogonal frequency-division multiplexing (OFDM) signals for microwave-ranging without necessitating any modifications. OFDM, being a joint communications and sensing waveform, offers the advantage of repurposing existing communication signals for ranging purposes without additional spectrum utilization. We discuss the theoretical underpinnings of our investigation and present simulated and experimental ranging measurements employing OFDM signals, complemented by range estimation and error analyses.
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    Non-cooperative high-efficiency multi-user ranging using OFDM signals
    (2024) Yazgan, Mehmet; Arslan, Hüseyin; Vakalis, Stavros
    Joint radar and communication (JRC) is attracting increasing interest due to the finite nature of the electromagnetic spectrum and the importance of spatial positioning in modern communications networks. Focusing on the challenge of utilizing the same spectrum for both communication and sensing among multiple users, we discuss the exceptional properties of waveform orthogonal frequency-division multiplexing (OFDM) for joint communications and sensing. OFDM's excellent correlation properties make it particularly suitable for this purpose. We delve into the theory of performing ranging with OFDM signals, including their cross-correlation with other signals in the same spectral bands, and clarify how multiple users can operate in an environment without being multiplexed in the frequency or time domain. Simulations are presented alongside experimental measurements from a two-user OFDM radar system operating at center frequencies of 1.5 GHz and 1.55 GHz, demonstrating simultaneous operation and the efficient use of spectral resources.
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    Secure key exchange and transmission design using artificial noise ınjection in OFDM systems
    (Institute of Electrical and Electronics Engineers Inc., 2022) Yazgan, Mehmet; Arslan, Hüseyin
    Orthogonal frequency division multiplexing (OFDM) is such a vital waveform scheme that is utilized in fifth-generation (5G) communication systems as well as the previous one. Since the usage scenarios of 5G are quite wide, the security of those systems is currently an open and critical issue. In this paper, a promising paradigm is proposed for enhancing physical layer (PHY) security in OFDM systems. Two independent secret keys are extracted by legitimate users quantizing the channel measurements. Those key sequences are exchanged via a novel artificial noise (AN) injection method which does not result in a key mismatch. Bit error rate (BER) versus signal-to-noise ratio (SNR) performance of the adversary is still low even if the malicious node has better channel than the legitimate user. After agreement upon the same key, both legitimate parties directly employ key sequence and inter-carrier interference matrix caused by the local oscillators to produce a secrecy matrix. This matrix enables secure communication by inserting it into the transmission design.