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</div> <div class="control"> <button class="button is-small is-link">Go</button> </div> </div> </form> </div> </div> <ol class="breathe-horizontal" start="1"> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2503.17721">arXiv:2503.17721</a> <span> [<a href="https://arxiv.org/pdf/2503.17721">pdf</a>, <a href="https://arxiv.org/format/2503.17721">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> </div> </div> <p class="title is-5 mathjax"> RIS-based Physical Layer Security for Integrated Sensing and Communication: A Comprehensive Survey </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Li%2C+Y">Yongxiao Li</a>, <a href="/search/eess?searchtype=author&query=Khan%2C+F">Feroz Khan</a>, <a href="/search/eess?searchtype=author&query=Ahmed%2C+M">Manzoor Ahmed</a>, <a href="/search/eess?searchtype=author&query=Soofi%2C+A+A">Aized Amin Soofi</a>, <a href="/search/eess?searchtype=author&query=Khan%2C+W+U">Wali Ullah Khan</a>, <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Asif%2C+M">Muhammad Asif</a>, <a href="/search/eess?searchtype=author&query=Han%2C+Z">Zhu Han</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2503.17721v1-abstract-short" style="display: inline;"> Integrated Sensing and Communication (ISAC) is a crucial component of future wireless networks, enabling seamless integration of Communication and Sensing (C\&S) functionalities. However, ensuring security in ISAC systems remains a significant challenge, as both C\&S data are susceptible to adversarial threats. Physical Layer Security (PLS) has emerged as a key framework for mitigating these risks… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2503.17721v1-abstract-full').style.display = 'inline'; document.getElementById('2503.17721v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2503.17721v1-abstract-full" style="display: none;"> Integrated Sensing and Communication (ISAC) is a crucial component of future wireless networks, enabling seamless integration of Communication and Sensing (C\&S) functionalities. However, ensuring security in ISAC systems remains a significant challenge, as both C\&S data are susceptible to adversarial threats. Physical Layer Security (PLS) has emerged as a key framework for mitigating these risks at the transmission level. Reconfigurable Intelligent Surfaces (RIS) further enhance PLS by dynamically shaping the radio environment to improve both secrecy along with C\&S performance. This survey begins with an overview of RIS, PLS, and ISAC fundamentals, establishing a foundation for understanding their integration. The state-of-the-art RIS-assisted PLS approaches in ISAC systems are then categorized into passive RIS and Active RIS (ARIS) paradigms. Passive RIS-based techniques focus on optimizing system throughput, covert communication, and Secrecy Rates (SRs), alongside improving sensing Signal-to-Noise Ratio (SNR) and Weighted Sum Rate (WSR) under various constraints. ARIS-based strategies extend these capabilities by actively optimizing beamforming to enhance secrecy and covert rates while ensuring robust sensing under communication and security constraints. By reviewing both passive and ARIS-based security frameworks, this survey highlights the transformative role of RIS in strengthening ISAC security. Furthermore, it explores key optimization methodologies, technical challenges, and future research directions for integrating RIS with PLS to ensure secure and efficient ISAC in next-generation 6G wireless networks. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2503.17721v1-abstract-full').style.display = 'none'; document.getElementById('2503.17721v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 22 March, 2025; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2025. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2503.17205">arXiv:2503.17205</a> <span> [<a href="https://arxiv.org/pdf/2503.17205">pdf</a>, <a href="https://arxiv.org/format/2503.17205">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> </div> </div> <p class="title is-5 mathjax"> Minimum Mean Squared Error Holographic Beamforming for Sum-Rate Maximization </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Khan%2C+W+U">Wali Ullah Khan</a>, <a href="/search/eess?searchtype=author&query=Alexandropoulos%2C+G+C">George C. Alexandropoulos</a>, <a href="/search/eess?searchtype=author&query=Ahmed%2C+M">Manzoor Ahmed</a>, <a href="/search/eess?searchtype=author&query=Chatzinotas%2C+S">Symeon Chatzinotas</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2503.17205v1-abstract-short" style="display: inline;"> This paper studies the problem of hybrid holographic beamforming for sum-rate maximization in a communication system assisted by a reconfigurable holographic surface. Existing methodologies predominantly rely on gradient-based or approximation techniques necessitating iterative optimization for each update of the holographic response, which imposes substantial computational overhead. To address th… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2503.17205v1-abstract-full').style.display = 'inline'; document.getElementById('2503.17205v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2503.17205v1-abstract-full" style="display: none;"> This paper studies the problem of hybrid holographic beamforming for sum-rate maximization in a communication system assisted by a reconfigurable holographic surface. Existing methodologies predominantly rely on gradient-based or approximation techniques necessitating iterative optimization for each update of the holographic response, which imposes substantial computational overhead. To address these limitations, we establish a mathematical relationship between the mean squared error (MSE) criterion and the holographic response of the RHS to enable alternating optimization based on the minimum MSE (MMSE). Our analysis demonstrates that this relationship exhibits a quadratic dependency on each element of the holographic beamformer. Exploiting this property, we derive closed-form optimal expressions for updating the holographic beamforming weights. Our complexity analysis indicates that the proposed approach exhibits only linear complexity in terms of the RHS size, thus, ensuring scalability for large-scale deployments. The presented simulation results validate the effectiveness of our MMSE-based holographic approach, providing useful insights. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2503.17205v1-abstract-full').style.display = 'none'; document.getElementById('2503.17205v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 21 March, 2025; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2025. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2503.15787">arXiv:2503.15787</a> <span> [<a href="https://arxiv.org/pdf/2503.15787">pdf</a>, <a href="https://arxiv.org/format/2503.15787">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Emerging Technologies">cs.ET</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Networking and Internet Architecture">cs.NI</span> </div> </div> <p class="title is-5 mathjax"> Enhancing Physical Layer Security in Cognitive Radio-Enabled NTNs with Beyond Diagonal RIS </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Khan%2C+W+U">Wali Ullah Khan</a>, <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Lagunas%2C+E">Eva Lagunas</a>, <a href="/search/eess?searchtype=author&query=Chatzinotas%2C+S">Symeon Chatzinotas</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2503.15787v1-abstract-short" style="display: inline;"> Beyond diagonal reconfigurable intelligent surfaces (BD-RIS) have emerged as a transformative technology for enhancing wireless communication by intelligently manipulating the propagation environment. This paper explores the potential of BD-RIS in improving cognitive radio enabled multilayer non-terrestrial networks (NTNs). It is assumed that a high-altitude platform station (HAPS) has set up the… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2503.15787v1-abstract-full').style.display = 'inline'; document.getElementById('2503.15787v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2503.15787v1-abstract-full" style="display: none;"> Beyond diagonal reconfigurable intelligent surfaces (BD-RIS) have emerged as a transformative technology for enhancing wireless communication by intelligently manipulating the propagation environment. This paper explores the potential of BD-RIS in improving cognitive radio enabled multilayer non-terrestrial networks (NTNs). It is assumed that a high-altitude platform station (HAPS) has set up the primary network, while an uncrewed aerial vehicle (UAV) establishes the secondary network in the HAPS footprint. We formulate a joint optimization problem to maximize the secrecy rate by optimizing BD-RIS phase shifts and the secondary transmitter power allocation while controlling the interference temperature from the secondary network to the primary network. To solve this problem efficiently, we decouple the original problem into two sub-problems, which are solved iteratively by relying on alternating optimization. Simulation results demonstrate the effectiveness of BD-RIS in cognitive radio-enabled multilayer NTNs to accommodate the secondary network while satisfying the constraints imposed from the primary network. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2503.15787v1-abstract-full').style.display = 'none'; document.getElementById('2503.15787v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 19 March, 2025; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2025. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">6, 4</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2503.10866">arXiv:2503.10866</a> <span> [<a href="https://arxiv.org/pdf/2503.10866">pdf</a>, <a href="https://arxiv.org/format/2503.10866">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Emerging Technologies">cs.ET</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> </div> </div> <p class="title is-5 mathjax"> Beyond Diagonal RIS Enhanced Cognitive Radio Enabled Multilayer Non-Terrestrial Networks </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Khan%2C+W+U">Wali Ullah Khan</a>, <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Lagunas%2C+E">Eva Lagunas</a>, <a href="/search/eess?searchtype=author&query=Chatzinotas%2C+S">Symeon Chatzinotas</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2503.10866v1-abstract-short" style="display: inline;"> Beyond diagonal reconfigurable intelligent surfaces (BD-RIS) have emerged as a transformative technology for enhancing wireless communication by intelligently manipulating the propagation environment. Its interconnected elements offer enhanced control over signal redirection, making it a promising solution for integrated terrestrial and non-terrestrial networks (NTNs). This paper explores the pote… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2503.10866v1-abstract-full').style.display = 'inline'; document.getElementById('2503.10866v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2503.10866v1-abstract-full" style="display: none;"> Beyond diagonal reconfigurable intelligent surfaces (BD-RIS) have emerged as a transformative technology for enhancing wireless communication by intelligently manipulating the propagation environment. Its interconnected elements offer enhanced control over signal redirection, making it a promising solution for integrated terrestrial and non-terrestrial networks (NTNs). This paper explores the potential of BD-RIS in improving cognitive radio enabled multilayer non-terrestrial networks. We formulate a joint optimization problem that maximizes the achievable spectral efficiency by optimizing BD-RIS phase shifts and secondary transmitter power allocation while controlling the interference temperature from the secondary network to the primary network. To solve this problem efficiently, we decouple the original problem and propose a novel solution based on an alternating optimization approach. Simulation results demonstrate the effectiveness of BD-RIS in cognitive radio enabled multilayer NTNs. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2503.10866v1-abstract-full').style.display = 'none'; document.getElementById('2503.10866v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 13 March, 2025; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2025. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">5,5</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2503.08423">arXiv:2503.08423</a> <span>  </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> </div> </div> <p class="title is-5 mathjax"> Survey on Beyond Diagonal RIS Enabled 6G Wireless Networks: Fundamentals, Recent Advances, and Challenges </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Khan%2C+W+U">Wali Ullah Khan</a>, <a href="/search/eess?searchtype=author&query=Ahmed%2C+M">Manzoor Ahmed</a>, <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Di+Renzo%2C+M">Marco Di Renzo</a>, <a href="/search/eess?searchtype=author&query=Lagunas%2C+E">Eva Lagunas</a>, <a href="/search/eess?searchtype=author&query=Mahmood%2C+A">Asad Mahmood</a>, <a href="/search/eess?searchtype=author&query=Shah%2C+S+T">Syed Tariq Shah</a>, <a href="/search/eess?searchtype=author&query=Dobre%2C+O+A">Octavia A. Dobre</a>, <a href="/search/eess?searchtype=author&query=Querol%2C+J">Jorge Querol</a>, <a href="/search/eess?searchtype=author&query=Chatzinotas%2C+S">Symeon Chatzinotas</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2503.08423v2-abstract-short" style="display: inline;"> Beyond Diagonal Reconfigurable Intelligent Surfaces (BD-RIS) represent a groundbreaking innovation in sixth-generation (6G) wireless networks, enabling unprecedented control over wireless propagation environments compared to conventional diagonal RIS (D-RIS). This survey provides a comprehensive analysis of BD-RIS, detailing its architectures, operational principles, and mathematical modeling whil… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2503.08423v2-abstract-full').style.display = 'inline'; document.getElementById('2503.08423v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2503.08423v2-abstract-full" style="display: none;"> Beyond Diagonal Reconfigurable Intelligent Surfaces (BD-RIS) represent a groundbreaking innovation in sixth-generation (6G) wireless networks, enabling unprecedented control over wireless propagation environments compared to conventional diagonal RIS (D-RIS). This survey provides a comprehensive analysis of BD-RIS, detailing its architectures, operational principles, and mathematical modeling while highlighting its performance benefits. BD-RIS classifications, including single-connected, fully-connected, and group-connected architectures, and their reflective, transmissive, hybrid, and multi-sector operating modes are examined. Recent advances in BD-RIS-enabled 6G networks are reviewed, focusing on critical areas such as channel estimation, sum-rate and spectral efficiency optimization, energy efficiency enhancement, and security. The survey identifies fundamental challenges in BD-RIS research, including hardware design limitations, adaptive channel estimation, and the impact of non-ideal hardware effects. Future research directions for BD-RIS are proposed, emphasizing the integration of artificial intelligence and machine learning (AI/ML), joint optimization of communication and sensing, and enhanced physical layer security (PLS). This study concludes by underscoring BD-RIS's transformative potential to redefine 6G wireless networks, offering valuable insights and lessons for future research and development. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2503.08423v2-abstract-full').style.display = 'none'; document.getElementById('2503.08423v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 March, 2025; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 11 March, 2025; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2025. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">As significant revisions have been requested by one of the co-authors due to certain technical flaws in the paper, and addressing these concerns will require substantial time, we kindly request the complete withdrawal of the current version from the arXiv platform until the corrected version is ready</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2503.01741">arXiv:2503.01741</a> <span> [<a href="https://arxiv.org/pdf/2503.01741">pdf</a>, <a href="https://arxiv.org/format/2503.01741">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> </div> </div> <p class="title is-5 mathjax"> Secrecy Rate Maximization for 6G Reconfigurable Holographic Surfaces Assisted Systems </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Khan%2C+W+U">Wali Ullah Khan</a>, <a href="/search/eess?searchtype=author&query=di+Renzo%2C+M">Marco di Renzo</a>, <a href="/search/eess?searchtype=author&query=Mahmood%2C+A">Asad Mahmood</a>, <a href="/search/eess?searchtype=author&query=Querol%2C+J">Jorge Querol</a>, <a href="/search/eess?searchtype=author&query=Chatzinotas%2C+S">Symeon Chatzinotas</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2503.01741v1-abstract-short" style="display: inline;"> Reconfigurable holographic surfaces (RHS) have emerged as a transformative material technology, enabling dynamic control of electromagnetic waves to generate versatile holographic beam patterns. This paper addresses the problem of secrecy rate maximization for an RHS-assisted systems by joint designing the digital beamforming, artificial noise (AN), and the analog holographic beamforming. However,… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2503.01741v1-abstract-full').style.display = 'inline'; document.getElementById('2503.01741v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2503.01741v1-abstract-full" style="display: none;"> Reconfigurable holographic surfaces (RHS) have emerged as a transformative material technology, enabling dynamic control of electromagnetic waves to generate versatile holographic beam patterns. This paper addresses the problem of secrecy rate maximization for an RHS-assisted systems by joint designing the digital beamforming, artificial noise (AN), and the analog holographic beamforming. However, such a problem results to be non-convex and challenging. Therefore, to solve it, a novel alternating optimization algorithm based on the majorization-maximization (MM) framework for RHS-assisted systems is proposed, which rely on surrogate functions to facilitate efficient and reliable optimization. In the proposed approach, digital beamforming design ensures directed signal power toward the legitimate user while minimizing leakage to the unintended receiver. The AN generation method projects noise into the null space of the legitimate user channel, aligning it with the unintended receiver channel to degrade its signal quality. Finally, the holographic beamforming weights are optimized to refine the wavefronts for enhanced secrecy rate performance Simulation results validate the effectiveness of the proposed framework, demonstrating significant improvements in secrecy rate compared to the benchmark method. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2503.01741v1-abstract-full').style.display = 'none'; document.getElementById('2503.01741v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 3 March, 2025; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2025. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2502.17428">arXiv:2502.17428</a> <span> [<a href="https://arxiv.org/pdf/2502.17428">pdf</a>, <a href="https://arxiv.org/format/2502.17428">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> </div> </div> <p class="title is-5 mathjax"> Joint Beamforming and 3D Location Optimization for Multi-User Holographic UAV Communications </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Mahmood%2C+A">Asad Mahmood</a>, <a href="/search/eess?searchtype=author&query=Thomas%2C+C+K">Christo Kurisummoottil Thomas</a>, <a href="/search/eess?searchtype=author&query=Alexandropoulos%2C+G+C">George C. Alexandropoulos</a>, <a href="/search/eess?searchtype=author&query=Querol%2C+J">Jorge Querol</a>, <a href="/search/eess?searchtype=author&query=Chatzinotas%2C+S">Symeon Chatzinotas</a>, <a href="/search/eess?searchtype=author&query=Saad%2C+W">Walid Saad</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2502.17428v1-abstract-short" style="display: inline;"> This paper pioneers the field of multi-user holographic unmanned aerial vehicle (UAV) communications, laying a solid foundation for future innovations in next-generation aerial wireless networks. The study focuses on the challenging problem of jointly optimizing hybrid holographic beamforming and 3D UAV positioning in scenarios where the UAV is equipped with a reconfigurable holographic surface (R… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2502.17428v1-abstract-full').style.display = 'inline'; document.getElementById('2502.17428v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2502.17428v1-abstract-full" style="display: none;"> This paper pioneers the field of multi-user holographic unmanned aerial vehicle (UAV) communications, laying a solid foundation for future innovations in next-generation aerial wireless networks. The study focuses on the challenging problem of jointly optimizing hybrid holographic beamforming and 3D UAV positioning in scenarios where the UAV is equipped with a reconfigurable holographic surface (RHS) instead of conventional phased array antennas. Using the unique capabilities of RHSs, the system dynamically adjusts both the position of the UAV and its hybrid beamforming properties to maximize the sum rate of the network. To address this complex optimization problem, we propose an iterative algorithm combining zero-forcing digital beamforming and a gradient ascent approach for the holographic patterns and the 3D position optimization, while ensuring practical feasibility constraints. The algorithm is designed to effectively balance the trade-offs between power, beamforming, and UAV trajectory constraints, enabling adaptive and efficient communications, while assuring a monotonic increase in the sum-rate performance. Our numerical investigations demonstrate that the significant performance improvements with the proposed approach over the benchmark methods, showcasing enhanced sum rate and system adaptability under varying conditions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2502.17428v1-abstract-full').style.display = 'none'; document.getElementById('2502.17428v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 February, 2025; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2025. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2502.17408">arXiv:2502.17408</a> <span> [<a href="https://arxiv.org/pdf/2502.17408">pdf</a>, <a href="https://arxiv.org/format/2502.17408">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> </div> </div> <p class="title is-5 mathjax"> Joint Holographic Beamforming and User Scheduling with Individual QoS Constraints </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Thomas%2C+C+K">Christo Kurisummoottil Thomas</a>, <a href="/search/eess?searchtype=author&query=Alexandropoulos%2C+G+C">George C. Alexandropoulos</a>, <a href="/search/eess?searchtype=author&query=Querol%2C+J">Jorge Querol</a>, <a href="/search/eess?searchtype=author&query=Chatzinotas%2C+S">Symeon Chatzinotas</a>, <a href="/search/eess?searchtype=author&query=Saad%2C+W">Walid Saad</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2502.17408v1-abstract-short" style="display: inline;"> Reconfigurable holographic surfaces (RHS) have emerged as a transformative material technology, enabling dynamic control of electromagnetic waves to generate versatile holographic beam patterns. This paper addresses the problem of joint hybrid holographic beamforming and user scheduling under per-user minimum quality-of-service (QoS) constraints, a critical challenge in resource-constrained networ… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2502.17408v1-abstract-full').style.display = 'inline'; document.getElementById('2502.17408v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2502.17408v1-abstract-full" style="display: none;"> Reconfigurable holographic surfaces (RHS) have emerged as a transformative material technology, enabling dynamic control of electromagnetic waves to generate versatile holographic beam patterns. This paper addresses the problem of joint hybrid holographic beamforming and user scheduling under per-user minimum quality-of-service (QoS) constraints, a critical challenge in resource-constrained networks. However, such a problem results in mixed-integer non-convex optimization, making it difficult to identify feasible solutions efficiently. To overcome this challenge, we propose a novel iterative optimization framework that jointly solves the problem to maximize the RHS-assisted network sum-rate, efficiently managing holographic beamforming patterns, dynamically scheduling users, and ensuring the minimum QoS requirements for each scheduled user. The proposed framework relies on zero-forcing digital beamforming, gradient-ascent-based holographic beamformer optimization, and a greedy user selection principle. Our extensive simulation results validate the effectiveness of the proposed scheme, demonstrating their superior performance compared to the benchmark algorithms in terms of sum-rate performance, while meeting the minimum per-user QoS constraints <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2502.17408v1-abstract-full').style.display = 'none'; document.getElementById('2502.17408v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 February, 2025; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2025. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2502.15248">arXiv:2502.15248</a> <span> [<a href="https://arxiv.org/pdf/2502.15248">pdf</a>, <a href="https://arxiv.org/format/2502.15248">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> </div> </div> <p class="title is-5 mathjax"> Holographic Joint Communications and Sensing With Cramer-Rao Bounds </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Khan%2C+W+U">Wali Ullah Khan</a>, <a href="/search/eess?searchtype=author&query=Alexandropoulos%2C+G">George Alexandropoulos</a>, <a href="/search/eess?searchtype=author&query=Querol%2C+J">Jorge Querol</a>, <a href="/search/eess?searchtype=author&query=Chatzinotas%2C+S">Symeon Chatzinotas</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2502.15248v1-abstract-short" style="display: inline;"> Joint Communication and Sensing (JCAS) technology facilitates the seamless integration of communication and sensing functionalities within a unified framework, enhancing spectral efficiency, reducing hardware complexity, and enabling simultaneous data transmission and environmental perception. This paper explores the potential of holographic JCAS systems by leveraging reconfigurable holographic su… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2502.15248v1-abstract-full').style.display = 'inline'; document.getElementById('2502.15248v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2502.15248v1-abstract-full" style="display: none;"> Joint Communication and Sensing (JCAS) technology facilitates the seamless integration of communication and sensing functionalities within a unified framework, enhancing spectral efficiency, reducing hardware complexity, and enabling simultaneous data transmission and environmental perception. This paper explores the potential of holographic JCAS systems by leveraging reconfigurable holographic surfaces (RHS) to achieve high-resolution hybrid holographic beamforming while simultaneously sensing the environment. As the holographic transceivers are governed by arbitrary antenna spacing, we first derive exact Cram茅r-Rao Bounds (CRBs) for azimuth and elevation angles to rigorously characterize the three-dimensional (3D) sensing accuracy. To optimize the system performance, we propose a novel weighted multi-objective problem formulation that aims to simultaneously maximize the communication rate and minimize the CRBs. However, this formulation is highly non-convex due to the inverse dependence of the CRB on the optimization variables, making the solution extremely challenging. To address this, we propose a novel algorithmic framework based on the Majorization-Maximization (MM) principle, employing alternating optimization to efficiently solve the problem. The proposed method relies on the closed-form surrogate functions that majorize the original objective derived herein, enabling tractable optimization. Simulation results are presented to validate the effectiveness of the proposed framework under diverse system configurations, demonstrating its potential for next-generation holographic JCAS systems. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2502.15248v1-abstract-full').style.display = 'none'; document.getElementById('2502.15248v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 21 February, 2025; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2025. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2502.03637">arXiv:2502.03637</a> <span> [<a href="https://arxiv.org/pdf/2502.03637">pdf</a>, <a href="https://arxiv.org/format/2502.03637">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Emerging Technologies">cs.ET</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Networking and Internet Architecture">cs.NI</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> </div> </div> <p class="title is-5 mathjax"> Beyond Diagonal RIS: A New Frontier for 6G Internet of Things Networks </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Khan%2C+W+U">Wali Ullah Khan</a>, <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Lagunas%2C+E">Eva Lagunas</a>, <a href="/search/eess?searchtype=author&query=Chatzinotas%2C+S">Symeon Chatzinotas</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2502.03637v1-abstract-short" style="display: inline;"> Reconfigurable intelligent surface (RIS) technology has emerged as a promising enabler for next-generation wireless networks, offering a paradigm shift from passive environments to programmable radio wave propagation. Despite the potential of diagonal RIS (D-RIS), its limited wave manipulation capability restricts performance gains. In this paper, we investigate the burgeoning concept of beyond-di… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2502.03637v1-abstract-full').style.display = 'inline'; document.getElementById('2502.03637v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2502.03637v1-abstract-full" style="display: none;"> Reconfigurable intelligent surface (RIS) technology has emerged as a promising enabler for next-generation wireless networks, offering a paradigm shift from passive environments to programmable radio wave propagation. Despite the potential of diagonal RIS (D-RIS), its limited wave manipulation capability restricts performance gains. In this paper, we investigate the burgeoning concept of beyond-diagonal RIS (BD-RIS), which incorporates non-diagonal elements in its scattering matrix to deliver more fine-grained control of electromagnetic wavefronts. We begin by discussing the limitations of traditional D-RIS and introduce key BD-RIS architectures with different operating modes. We then highlight the features that make BD-RIS particularly advantageous for 6G IoT applications, including advanced beamforming, enhanced interference mitigation, and flexible coverage. A case study on BD-RIS-assisted vehicle-to-vehicle (V2V) communication in an underlay cellular network demonstrates considerable improvements in spectral efficiency when compared to D-RIS and conventional systems. Lastly, we present current challenges such as hardware design complexity, channel estimation, and non-ideal hardware effects, and propose future research directions involving AI-driven optimization, joint communication and sensing, and physical layer security. Our findings illustrate the transformative potential of BD-RIS in shaping high-performance, scalable, and reliable 6G IoT networks. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2502.03637v1-abstract-full').style.display = 'none'; document.getElementById('2502.03637v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 5 February, 2025; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2025. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">8,4</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2501.05243">arXiv:2501.05243</a> <span> [<a href="https://arxiv.org/pdf/2501.05243">pdf</a>, <a href="https://arxiv.org/format/2501.05243">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> </div> </div> <p class="title is-5 mathjax"> Joint Communications and Sensing for 6G Satellite Networks: Use Cases and Challenges </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Thiruvasagam%2C+P">Prabhu Thiruvasagam</a>, <a href="/search/eess?searchtype=author&query=Khan%2C+W+U">Wali Ullah Khan</a>, <a href="/search/eess?searchtype=author&query=Solanki%2C+S">Sourabh Solanki</a>, <a href="/search/eess?searchtype=author&query=Alexandropoulos%2C+G+C">George C. Alexandropoulos</a>, <a href="/search/eess?searchtype=author&query=Querol%2C+J">Jorge Querol</a>, <a href="/search/eess?searchtype=author&query=Plachy%2C+J">Jan Plachy</a>, <a href="/search/eess?searchtype=author&query=Holschke%2C+O">Oliver Holschke</a>, <a href="/search/eess?searchtype=author&query=Chatzinotas%2C+S">Symeon Chatzinotas</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2501.05243v1-abstract-short" style="display: inline;"> Satellite Networks (SN) have traditionally been instrumental in providing two key services: communications and sensing. Communications satellites enable global connectivity, while sensing satellites facilitate applications such as Earth observation, navigation, and disaster management. However, the emergence of novel use cases and the exponential growth in service demands make the independent evol… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2501.05243v1-abstract-full').style.display = 'inline'; document.getElementById('2501.05243v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2501.05243v1-abstract-full" style="display: none;"> Satellite Networks (SN) have traditionally been instrumental in providing two key services: communications and sensing. Communications satellites enable global connectivity, while sensing satellites facilitate applications such as Earth observation, navigation, and disaster management. However, the emergence of novel use cases and the exponential growth in service demands make the independent evolution of communication and sensing payloads increasingly impractical. Addressing this challenge requires innovative approaches to optimize satellite resources. Joint Communications and Sensing (JCAS) technology represents a transformative paradigm for SN. By integrating communication and sensing functionalities into unified hardware platforms, JCAS enhances spectral efficiency, reduces operational costs, and minimizes hardware redundancies. This paper explores the potential of JCAS in advancing the next-generation space era, highlighting its role in emerging applications. Furthermore, it identifies critical challenges, such as waveform design, Doppler effect mitigation, and multi-target detection, that remain open for future research. Through these discussions, we aim to stimulate further research into the transformative potential of JCAS in addressing the demands of 6G and beyond SN. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2501.05243v1-abstract-full').style.display = 'none'; document.getElementById('2501.05243v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 9 January, 2025; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2025. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2411.10014">arXiv:2411.10014</a> <span> [<a href="https://arxiv.org/pdf/2411.10014">pdf</a>, <a href="https://arxiv.org/format/2411.10014">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> </div> </div> <p class="title is-5 mathjax"> Holographic MIMO for Next Generation Non-Terrestrial Networks: Motivation, Opportunities, and Challenges </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Iacovelli%2C+G">Giovanni Iacovelli</a>, <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Khan%2C+W+U">Wali Ullah Khan</a>, <a href="/search/eess?searchtype=author&query=Mahmood%2C+A">Asad Mahmood</a>, <a href="/search/eess?searchtype=author&query=Alexandropoulos%2C+G+C">George C. Alexandropoulos</a>, <a href="/search/eess?searchtype=author&query=Querol%2C+J">Jorge Querol</a>, <a href="/search/eess?searchtype=author&query=Chatzinotas%2C+S">Symeon Chatzinotas</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2411.10014v1-abstract-short" style="display: inline;"> In this article, we propose the integration of the Holographic Multiple Input Multiple Output (HMIMO) as a transformative solution for next generation Non-Terrestrial Networks (NTNs), addressing key challenges, such as high hardware costs, launch expenses, and energy inefficiency. Traditional NTNs are constrained by the financial and operational limitations posed by bulky, costly antenna systems,… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.10014v1-abstract-full').style.display = 'inline'; document.getElementById('2411.10014v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2411.10014v1-abstract-full" style="display: none;"> In this article, we propose the integration of the Holographic Multiple Input Multiple Output (HMIMO) as a transformative solution for next generation Non-Terrestrial Networks (NTNs), addressing key challenges, such as high hardware costs, launch expenses, and energy inefficiency. Traditional NTNs are constrained by the financial and operational limitations posed by bulky, costly antenna systems, alongside the complexities of maintaining effective communications in space. HMIMO offers a novel approach utilizing compact and lightweight arrays of densely packed radiating elements with real-time reconfiguration capabilities, thus, capable of optimizing system performance under dynamic conditions such as varying orbital dynamics and Doppler shifts. By replacing conventional antenna systems with HMIMO, the complexity and cost of satellite manufacturing and launch can be substantially reduced, enabling more streamlined and cost-effective satellite designs. This advancement holds significant potential to democratize space communications, making them accessible to a broader range of stakeholders, including smaller nations and commercial enterprises. Moreover, the inherent capabilities of HMIMO in enhancing energy efficiency, scalability, and adaptability position this technology as a key enabler of new use cases and sustainable satellite operations. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.10014v1-abstract-full').style.display = 'none'; document.getElementById('2411.10014v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 15 November, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2024. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2406.07910">arXiv:2406.07910</a> <span> [<a href="https://arxiv.org/pdf/2406.07910">pdf</a>, <a href="https://arxiv.org/format/2406.07910">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Emerging Technologies">cs.ET</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Networking and Internet Architecture">cs.NI</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> </div> </div> <p class="title is-5 mathjax"> Demonstration of Safe Electromagnetic Radiation Emitted by 5G Active Antenna Systems </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Kumar%2C+S">Sumit Kumar</a>, <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Astro%2C+A">Abdelrahman Astro</a>, <a href="/search/eess?searchtype=author&query=Querol%2C+J">Jorge Querol</a>, <a href="/search/eess?searchtype=author&query=Chatzinotas%2C+S">Symeon Chatzinotas</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2406.07910v1-abstract-short" style="display: inline;"> The careful planning and safe deployment of 5G technologies will bring enormous benefits to society and the economy. Higher frequency, beamforming, and small-cells are key technologies that will provide unmatched throughput and seamless connectivity to 5G users. Superficial knowledge of these technologies has raised concerns among the general public about the harmful effects of radiation. Several… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.07910v1-abstract-full').style.display = 'inline'; document.getElementById('2406.07910v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2406.07910v1-abstract-full" style="display: none;"> The careful planning and safe deployment of 5G technologies will bring enormous benefits to society and the economy. Higher frequency, beamforming, and small-cells are key technologies that will provide unmatched throughput and seamless connectivity to 5G users. Superficial knowledge of these technologies has raised concerns among the general public about the harmful effects of radiation. Several standardization bodies are active to put limits on the emissions which are based on a defined set of radiation measurement methodologies. However, due to the peculiarity of 5G such as dynamicity of the beams, network densification, Time Division Duplexing mode of operation, etc, using existing EMF measurement methods may provide inaccurate results. In this context, we discuss our experimental studies aimed towards the measurement of radiation caused by beam-based transmissions from a 5G base station equipped with an Active Antenna System(AAS). We elaborate on the shortcomings of current measurement methodologies and address several open questions. Next, we demonstrate that using user-specific downlink beamforming, not only better performance is achieved compared to non-beamformed downlink, but also the radiation in the vicinity of the intended user is significantly decreased. Further, we show that under weak reception conditions, an uplink transmission can cause significantly high radiation in the vicinity of the user equipment. We believe that our work will help in clearing several misleading concepts about the 5G EMF radiation effects. We conclude the work by providing guidelines to improve the methodology of EMF measurement by considering the spatiotemporal dynamicity of the 5G transmission. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.07910v1-abstract-full').style.display = 'none'; document.getElementById('2406.07910v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 12 June, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2024. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2309.12507">arXiv:2309.12507</a> <span> [<a href="https://arxiv.org/pdf/2309.12507">pdf</a>, <a href="https://arxiv.org/format/2309.12507">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> </div> </div> <p class="title is-5 mathjax"> Deep Reinforcement Learning for Backscatter Communications: Augmenting Intelligence in Future Internet of Things </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Khan%2C+W+U">Wali Ullah Khan</a>, <a href="/search/eess?searchtype=author&query=Lagunas%2C+E">Eva Lagunas</a>, <a href="/search/eess?searchtype=author&query=Ali%2C+Z">Zain Ali</a>, <a href="/search/eess?searchtype=author&query=Mahmood%2C+A">Asad Mahmood</a>, <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Ahmed%2C+M">Manzoor Ahmed</a>, <a href="/search/eess?searchtype=author&query=Chatzinotas%2C+S">Symeon Chatzinotas</a>, <a href="/search/eess?searchtype=author&query=Ottersten%2C+B">Bj枚rn Ottersten</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2309.12507v1-abstract-short" style="display: inline;"> Backscatter communication (BC) technology offers sustainable solutions for next-generation Internet-of-Things (IoT) networks, where devices can transmit data by reflecting and adjusting incident radio frequency signals. In parallel to BC, deep reinforcement learning (DRL) has recently emerged as a promising tool to augment intelligence and optimize low-powered IoT devices. This article commences b… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.12507v1-abstract-full').style.display = 'inline'; document.getElementById('2309.12507v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2309.12507v1-abstract-full" style="display: none;"> Backscatter communication (BC) technology offers sustainable solutions for next-generation Internet-of-Things (IoT) networks, where devices can transmit data by reflecting and adjusting incident radio frequency signals. In parallel to BC, deep reinforcement learning (DRL) has recently emerged as a promising tool to augment intelligence and optimize low-powered IoT devices. This article commences by elucidating the foundational principles underpinning BC systems, subsequently delving into the diverse array of DRL techniques and their respective practical implementations. Subsequently, it investigates potential domains and presents recent advancements in the realm of DRL-BC systems. A use case of RIS-aided non-orthogonal multiple access BC systems leveraging DRL is meticulously examined to highlight its potential. Lastly, this study identifies and investigates salient challenges and proffers prospective avenues for future research endeavors. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.12507v1-abstract-full').style.display = 'none'; document.getElementById('2309.12507v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 21 September, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">7, 3</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2309.02859">arXiv:2309.02859</a> <span> [<a href="https://arxiv.org/pdf/2309.02859">pdf</a>, <a href="https://arxiv.org/format/2309.02859">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> </div> </div> <p class="title is-5 mathjax"> Reconfigurable Intelligent Surfaces for 6G Non-Terrestrial Networks: Assisting Connectivity from the Sky </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Khan%2C+W+U">Wali Ullah Khan</a>, <a href="/search/eess?searchtype=author&query=Mahmood%2C+A">Asad Mahmood</a>, <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Lagunas%2C+E">Eva Lagunas</a>, <a href="/search/eess?searchtype=author&query=Chatzinotas%2C+S">Symeon Chatzinotas</a>, <a href="/search/eess?searchtype=author&query=Ottersten%2C+B">Bj枚rn Ottersten</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2309.02859v2-abstract-short" style="display: inline;"> This paper studies the potential of RIS-integrated NTNs to revolutionize the next-generation connectivity. First, it discusses the fundamentals of RIS technology. Secondly, it delves into reporting the recent advances in RIS-enabled NTNs. Subsequently, it presents a novel framework based on the current state-of-the-art for low earth orbit satellites (LEO) communications, wherein the signal receive… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.02859v2-abstract-full').style.display = 'inline'; document.getElementById('2309.02859v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2309.02859v2-abstract-full" style="display: none;"> This paper studies the potential of RIS-integrated NTNs to revolutionize the next-generation connectivity. First, it discusses the fundamentals of RIS technology. Secondly, it delves into reporting the recent advances in RIS-enabled NTNs. Subsequently, it presents a novel framework based on the current state-of-the-art for low earth orbit satellites (LEO) communications, wherein the signal received at the user terminal traverses both a direct link and an RIS link, and the RIS is mounted on a high-altitude platform (HAP) situated within the stratosphere. Finally, the paper concludes by highlighting open challenges and future research directions to revolutionize the realm of RIS-integrated NTNs. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.02859v2-abstract-full').style.display = 'none'; document.getElementById('2309.02859v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 October, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 6 September, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">6,5</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2308.09809">arXiv:2308.09809</a> <span> [<a href="https://arxiv.org/pdf/2308.09809">pdf</a>, <a href="https://arxiv.org/format/2308.09809">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Networking and Internet Architecture">cs.NI</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> </div> </div> <p class="title is-5 mathjax"> Adaptive Timers and Buffer Optimization for Layer-2 Protocols in 5G Non-Terrestrial Networks </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Kumar%2C+S">Sumit Kumar</a>, <a href="/search/eess?searchtype=author&query=Querol%2C+J">Jorge Querol</a>, <a href="/search/eess?searchtype=author&query=Chatzinotas%2C+S">Symeon Chatzinotas</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2308.09809v1-abstract-short" style="display: inline;"> Interest in the integration of Terrestrial Networks (TN) and Non-Terrestrial Networks (NTN); primarily satellites; has been rekindled due to the potential of NTN to provide ubiquitous coverage. Especially with the peculiar and flexible physical layer properties of 5G-NR, now direct access to 5G services through satellites could become possible. However, the large Round-Trip Delays (RTD) in NTNs re… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.09809v1-abstract-full').style.display = 'inline'; document.getElementById('2308.09809v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2308.09809v1-abstract-full" style="display: none;"> Interest in the integration of Terrestrial Networks (TN) and Non-Terrestrial Networks (NTN); primarily satellites; has been rekindled due to the potential of NTN to provide ubiquitous coverage. Especially with the peculiar and flexible physical layer properties of 5G-NR, now direct access to 5G services through satellites could become possible. However, the large Round-Trip Delays (RTD) in NTNs require a re-evaluation of the design of RLC and PDCP layers timers ( and associated buffers), in particular for the regenerative payload satellites which have limited computational resources, and hence need to be optimally utilized. Our aim in this work is to initiate a new line of research for emerging NTNs with limited resources from a higher-layer perspective. To this end, we propose a novel and efficient method for optimally designing the RLC and PDCP layers' buffers and timers without the need for intensive computations. This approach is relevant for low-cost satellites, which have limited computational and energy resources. The simulation results show that the proposed methods can significantly improve the performance in terms of resource utilization and delays. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.09809v1-abstract-full').style.display = 'none'; document.getElementById('2308.09809v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 18 August, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2023. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2308.09805">arXiv:2308.09805</a> <span> [<a href="https://arxiv.org/pdf/2308.09805">pdf</a>, <a href="https://arxiv.org/format/2308.09805">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> </div> </div> <p class="title is-5 mathjax"> Signal Processing Based Antenna Pattern Characterization for MIMO Systems </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Querol%2C+J">Jorge Querol</a>, <a href="/search/eess?searchtype=author&query=Chatzinotas%2C+S">Symeon Chatzinotas</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2308.09805v1-abstract-short" style="display: inline;"> Sophisticated antenna technologies are constantly evolving to meet the escalating data demands projected for 6G and future networks. The characterization of these emerging antenna systems poses challenges that necessitate a reevaluation of conventional techniques, which rely solely on simple measurements conducted in advanced anechoic chambers. In this study, our objective is to introduce a novel… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.09805v1-abstract-full').style.display = 'inline'; document.getElementById('2308.09805v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2308.09805v1-abstract-full" style="display: none;"> Sophisticated antenna technologies are constantly evolving to meet the escalating data demands projected for 6G and future networks. The characterization of these emerging antenna systems poses challenges that necessitate a reevaluation of conventional techniques, which rely solely on simple measurements conducted in advanced anechoic chambers. In this study, our objective is to introduce a novel endeavour for antenna pattern characterization (APC) in next-generation multiple-input-multiple-output (MIMO) systems by utilizing the potential of signal processing tools. In contrast to traditional methods that struggle with multi-path scenarios and require specialized equipment for measurements, we endeavour to estimate the antenna pattern by exploiting information from both line-of-sight (LoS) and non-LoS contributions. This approach enables antenna pattern characterization in complex environments without the need for anechoic chambers, resulting in substantial cost savings. Furthermore, it grants a much wider research community the ability to independently perform APC for emerging complex 6G antenna systems, without relying on anechoic chambers. Simulation results demonstrate the efficacy of the proposed novel approach in accurately estimating the true antenna pattern. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.09805v1-abstract-full').style.display = 'none'; document.getElementById('2308.09805v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 18 August, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2023. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2308.08579">arXiv:2308.08579</a> <span> [<a href="https://arxiv.org/pdf/2308.08579">pdf</a>, <a href="https://arxiv.org/format/2308.08579">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> </div> </div> <p class="title is-5 mathjax"> IRS Assisted MIMO Full Duplex: Rate Analysis and Beamforming Under Imperfect CSI </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Solanki%2C+S">Sourabh Solanki</a>, <a href="/search/eess?searchtype=author&query=Querol%2C+J">Jorge Querol</a>, <a href="/search/eess?searchtype=author&query=Kumar%2C+S">Sumit Kumar</a>, <a href="/search/eess?searchtype=author&query=Chatzinotas%2C+S">Symeon Chatzinotas</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2308.08579v1-abstract-short" style="display: inline;"> Intelligent reflecting surfaces (IRS) have emerged as a promising technology to enhance the performance of wireless communication systems. By actively manipulating the wireless propagation environment, IRS enables efficient signal transmission and reception. In recent years, the integration of IRS with full-duplex (FD) communication has garnered significant attention due to its potential to furthe… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.08579v1-abstract-full').style.display = 'inline'; document.getElementById('2308.08579v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2308.08579v1-abstract-full" style="display: none;"> Intelligent reflecting surfaces (IRS) have emerged as a promising technology to enhance the performance of wireless communication systems. By actively manipulating the wireless propagation environment, IRS enables efficient signal transmission and reception. In recent years, the integration of IRS with full-duplex (FD) communication has garnered significant attention due to its potential to further improve spectral and energy efficiencies. IRS-assisted FD systems combine the benefits of both IRS and FD technologies, providing a powerful solution for the next generation of cellular systems. In this manuscript, we present a novel approach to jointly optimize active and passive beamforming in a multiple-input-multiple-output (MIMO) FD system assisted by an IRS for weighted sum rate (WSR) maximization. Given the inherent difficulty in obtaining perfect channel state information (CSI) in practical scenarios, we consider imperfect CSI and propose a statistically robust beamforming strategy to maximize the ergodic WSR. Additionally, we analyze the achievable WSR for an IRS-assisted MIMO FD system under imperfect CSI by deriving both the lower and upper bounds. To tackle the problem of ergodic WSR maximization, we employ the concept of expected weighted minimum mean squared error (EWMMSE), which exploits the information of the expected error covariance matrices and ensures convergence to a local optimum. We evaluate the effectiveness of our proposed design through extensive simulations. The results demonstrate that our robust approach yields significant performance improvements compared to the simplistic beamforming approach that disregards CSI errors, while also outperforming the robust half-duplex (HD) system considerably <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.08579v1-abstract-full').style.display = 'none'; document.getElementById('2308.08579v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 16 August, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">arXiv admin note: substantial text overlap with arXiv:2308.08016</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2308.08016">arXiv:2308.08016</a> <span> [<a href="https://arxiv.org/pdf/2308.08016">pdf</a>, <a href="https://arxiv.org/format/2308.08016">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> </div> </div> <p class="title is-5 mathjax"> Robust Beamforming for IRS Aided MIMO Full Duplex Systems </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Querol%2C+J">Jorge Querol</a>, <a href="/search/eess?searchtype=author&query=Solanki%2C+S">Sourabh Solanki</a>, <a href="/search/eess?searchtype=author&query=Kumar%2C+S">Sumit Kumar</a>, <a href="/search/eess?searchtype=author&query=Chatzinotas%2C+S">Symeon Chatzinotas</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2308.08016v1-abstract-short" style="display: inline;"> In this paper, a novel robust beamforming for an intelligent reflecting surface (IRS) assisted FD system is presented. Since perfect channel state information (CSI) is often challenging to acquire in practice, we consider the case of imperfect CSI and adopt a statistically robust beamforming approach to maximize the ergodic weighted sum rate (WSR). We also analyze the achievable WSR of an IRS-assi… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.08016v1-abstract-full').style.display = 'inline'; document.getElementById('2308.08016v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2308.08016v1-abstract-full" style="display: none;"> In this paper, a novel robust beamforming for an intelligent reflecting surface (IRS) assisted FD system is presented. Since perfect channel state information (CSI) is often challenging to acquire in practice, we consider the case of imperfect CSI and adopt a statistically robust beamforming approach to maximize the ergodic weighted sum rate (WSR). We also analyze the achievable WSR of an IRS-assisted FD with imperfect CSI, for which the lower and the upper bounds are derived. The ergodic WSR maximization problem is tackled based on the expected Weighted Minimum Mean Squared Error (WMMSE), which is guaranteed to converge to a local optimum. The effectiveness of the proposed design is investigated with extensive simulation results. It is shown that our robust design achieves significant performance gain compared to the naive beamforming approaches and considerably outperforms the robust Half-Duplex (HD) system. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.08016v1-abstract-full').style.display = 'none'; document.getElementById('2308.08016v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 15 August, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2023. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2308.07266">arXiv:2308.07266</a> <span> [<a href="https://arxiv.org/pdf/2308.07266">pdf</a>, <a href="https://arxiv.org/format/2308.07266">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Information Theory">cs.IT</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> </div> </div> <p class="title is-5 mathjax"> Full Duplex Joint Communications and Sensing for 6G: Opportunities and Challenges </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Solanki%2C+S">Sourabh Solanki</a>, <a href="/search/eess?searchtype=author&query=Alexandropoulos%2C+G+C">George C. Alexandropoulos</a>, <a href="/search/eess?searchtype=author&query=Lagunas%2C+E">Eva Lagunas</a>, <a href="/search/eess?searchtype=author&query=Querol%2C+J">Jorge Querol</a>, <a href="/search/eess?searchtype=author&query=Chatzinotas%2C+S">Symeon Chatzinotas</a>, <a href="/search/eess?searchtype=author&query=Ottersten%2C+B">Bj枚rn Ottersten</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2308.07266v2-abstract-short" style="display: inline;"> The paradigm of joint communications and sensing (JCAS) envisions a revolutionary integration of communication and radar functionalities within a unified hardware platform. This novel concept not only opens up unprecedented interoperability opportunities, but also exhibits unique design challenges. To this end, the success of JCAS is highly dependent on efficient full-duplex (FD) operation, which… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.07266v2-abstract-full').style.display = 'inline'; document.getElementById('2308.07266v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2308.07266v2-abstract-full" style="display: none;"> The paradigm of joint communications and sensing (JCAS) envisions a revolutionary integration of communication and radar functionalities within a unified hardware platform. This novel concept not only opens up unprecedented interoperability opportunities, but also exhibits unique design challenges. To this end, the success of JCAS is highly dependent on efficient full-duplex (FD) operation, which has the potential to enable simultaneous transmission and reception within the same frequency band. While JCAS research is lately expanding, there still exist relevant directions of investigation that hold tremendous potential to profoundly transform the sixth generation (6G), and beyond, cellular networks. This article presents new opportunities and challenges brought up by FD-enabled JCAS, taking into account the key technical peculiarities of FD systems. Unlike simplified JCAS scenarios, we delve into the most comprehensive configuration, encompassing uplink and downlink users, as well as monostatic and bistatic radars, all harmoniously coexisting to jointly push the boundaries of both communications and sensing. The performance improvements resulting from this advancement bring forth numerous new challenges, each meticulously examined and expounded upon. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.07266v2-abstract-full').style.display = 'none'; document.getElementById('2308.07266v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 21 November, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 14 August, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2023. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2306.10865">arXiv:2306.10865</a> <span> [<a href="https://arxiv.org/pdf/2306.10865">pdf</a>, <a href="https://arxiv.org/format/2306.10865">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Information Theory">cs.IT</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> </div> </div> <p class="title is-5 mathjax"> Full-Duplex-Enabled Joint Communications and Sensing with Reconfigurable Intelligent Surfaces </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Alexandropoulos%2C+G+C">George C. Alexandropoulos</a>, <a href="/search/eess?searchtype=author&query=Slock%2C+D">Dirk Slock</a>, <a href="/search/eess?searchtype=author&query=Querol%2C+J">Jorge Querol</a>, <a href="/search/eess?searchtype=author&query=Chatzinotas%2C+S">Symeon Chatzinotas</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2306.10865v1-abstract-short" style="display: inline;"> The full-duplex (FD) technology has the potential to radically evolve wireless systems, facilitating the integration of both communications and radar functionalities into a single device, thus, enabling joint communication and sensing (JCAS). In this paper, we present a novel approach for JCAS that incorporates a reconfigurable intelligent surface (RIS) in the near-field of an FD multiple-input mu… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.10865v1-abstract-full').style.display = 'inline'; document.getElementById('2306.10865v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2306.10865v1-abstract-full" style="display: none;"> The full-duplex (FD) technology has the potential to radically evolve wireless systems, facilitating the integration of both communications and radar functionalities into a single device, thus, enabling joint communication and sensing (JCAS). In this paper, we present a novel approach for JCAS that incorporates a reconfigurable intelligent surface (RIS) in the near-field of an FD multiple-input multiple-output (MIMO) node, which is jointly optimized with the digital beamformers to enable JSAC and efficiently handle self-interference (SI). We propose a novel problem formulation for FD MIMO JCAS systems to jointly minimize the total received power at the FD node's radar receiver while maximizing the sum rate of downlink communications subject to a Cram茅r-Rao bound (CRB) constraint. In contrast to the typically used CRB in the relevant literature, we derive a novel, more accurate, target estimation bound that fully takes into account the RIS deployment. The considered problem is solved using alternating optimization, which is guaranteed to converge to a local optimum. The simulation results demonstrate that the proposed scheme achieves significant performance improvement both for communications and sensing. It is showcased that, jointly designing the FD MIMO beamformers and the RIS phase configuration to be SI aware can significantly loosen the requirement for additional SI cancellation. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.10865v1-abstract-full').style.display = 'none'; document.getElementById('2306.10865v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 19 June, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2023. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2211.10700">arXiv:2211.10700</a> <span> [<a href="https://arxiv.org/pdf/2211.10700">pdf</a>, <a href="https://arxiv.org/format/2211.10700">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Information Theory">cs.IT</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> </div> </div> <p class="title is-5 mathjax"> Intelligent Reflecting Surfaces Assisted Millimeter Wave MIMO Full Duplex Systems </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Tomasin%2C+S">Stefano Tomasin</a>, <a href="/search/eess?searchtype=author&query=Slock%2C+D">Dirk Slock</a>, <a href="/search/eess?searchtype=author&query=Chatzinotas%2C+S">Symeon Chatzinotas</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2211.10700v2-abstract-short" style="display: inline;"> Full duplex (FD) systems suffer from very high hardware cost and high power consumption to mitigate the self-interference (SI) in the analog domain. Moreover, in millimeter wave (mmWave) they rely on hybrid beamforming (HYBF) as a signal processing tool to partially deal with the SI, which presents many drawbacks such as high insertion loss and high power consumption. This article proposes the use… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.10700v2-abstract-full').style.display = 'inline'; document.getElementById('2211.10700v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2211.10700v2-abstract-full" style="display: none;"> Full duplex (FD) systems suffer from very high hardware cost and high power consumption to mitigate the self-interference (SI) in the analog domain. Moreover, in millimeter wave (mmWave) they rely on hybrid beamforming (HYBF) as a signal processing tool to partially deal with the SI, which presents many drawbacks such as high insertion loss and high power consumption. This article proposes the use of near-field (NF-) IRSs for FD systems with the objective to solve the aforementioned issues cost-efficiently. Namely, we propose to truncate the analog/hybrid beamforming stage of the mmWave FD systems and compensate it with an NF-IRS, to simultaneously and smartly control the uplink (UL) and downlink (DL) channels, while assisting in shaping the SI channel: this to obtain very strong passive SI cancellation. A novel joint active and passive beamforming design for the weighted sum-rate (WSR) maximization of a NF-IRS-assisted mmWave point-to-point FD system is presented. Results show that the proposed solution fully reaps the benefits of the IRSs only when they operate in the NF, which leads to considerably higher gains compared to the conventional massive MIMO (mMIMO) mmWave FD and half duplex (HD) systems. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.10700v2-abstract-full').style.display = 'none'; document.getElementById('2211.10700v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 14 June, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 19 November, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2022. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2112.02335">arXiv:2112.02335</a> <span> [<a href="https://arxiv.org/pdf/2112.02335">pdf</a>, <a href="https://arxiv.org/format/2112.02335">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Information Theory">cs.IT</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> </div> </div> <p class="title is-5 mathjax"> Parallel and Distributed Hybrid Beamforming for Multicell Millimeter Wave MIMO Full Duplex </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Chatzinotas%2C+S">Symeon Chatzinotas</a>, <a href="/search/eess?searchtype=author&query=Slock%2C+D">Dirk Slock</a>, <a href="/search/eess?searchtype=author&query=Lagunas%2C+E">Eva Lagunas</a>, <a href="/search/eess?searchtype=author&query=Querol%2C+J">Jorge Querol</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2112.02335v11-abstract-short" style="display: inline;"> Full duplex (FD) is an auspicious wireless technology that holds the potential to double data rates through simultaneous transmission and reception. This paper proposes two innovative designs of hybrid beamforming (HYBF) for a multicell massive multiple-input-multiple-output (mMIMO) millimeter wave (mmWave) FD system. Initially, we introduce a novel centralized HYBF (C-HYBF) scheme, which employs… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2112.02335v11-abstract-full').style.display = 'inline'; document.getElementById('2112.02335v11-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2112.02335v11-abstract-full" style="display: none;"> Full duplex (FD) is an auspicious wireless technology that holds the potential to double data rates through simultaneous transmission and reception. This paper proposes two innovative designs of hybrid beamforming (HYBF) for a multicell massive multiple-input-multiple-output (mMIMO) millimeter wave (mmWave) FD system. Initially, we introduce a novel centralized HYBF (C-HYBF) scheme, which employs the minorization-maximization (MM) method. However, while centralized beamforming designs offer superior performance, they suffer from high computational complexity, substantial communication overhead, and demand expensive computational resources. To surmount these challenges, we present a framework that facilitates per-link parallel and distributed HYBF (P&D- HYBF) in the mmWave frequency band. This cooperative approach enables each base station (BS) to independently solve its local, low-complexity sub-problems in parallel, resulting in a substantial reduction in communication overhead and computational complexity. Simulation results demonstrate that P&D-HYBF achieves comparable performance to C-HYBF, and with only a few radio-frequency (RF) chains, both designs surpass the capabilities of fully digital half duplex (HD) systems. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2112.02335v11-abstract-full').style.display = 'none'; document.getElementById('2112.02335v11-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 1 June, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 4 December, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2021. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2108.00465">arXiv:2108.00465</a> <span> [<a href="https://arxiv.org/pdf/2108.00465">pdf</a>, <a href="https://arxiv.org/format/2108.00465">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Information Theory">cs.IT</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> </div> </div> <p class="title is-5 mathjax"> Hybrid Beamforming and Combining for Millimeter Wave Full Duplex Massive MIMO Interference Channel </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Slock%2C+D">Dirk Slock</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2108.00465v2-abstract-short" style="display: inline;"> Full Duplex (FD) communication can revolutionize wireless communications as it avoids using independent channels for bi-directional communications. This work generalizes the point-to-point FD communication in millimeter wave (mmWave) band consisting of K-pairs of massive MIMO FD nodes operating simultaneously. We present a novel joint hybrid beamforming (HYBF) and combining scheme for weighted sum… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2108.00465v2-abstract-full').style.display = 'inline'; document.getElementById('2108.00465v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2108.00465v2-abstract-full" style="display: none;"> Full Duplex (FD) communication can revolutionize wireless communications as it avoids using independent channels for bi-directional communications. This work generalizes the point-to-point FD communication in millimeter wave (mmWave) band consisting of K-pairs of massive MIMO FD nodes operating simultaneously. We present a novel joint hybrid beamforming (HYBF) and combining scheme for weighted sum-rate (WSR) maximization to enable the coexistence of massive MIMO FD links cost-efficiently. The proposed algorithm relies on alternative optimization based on the minorization-maximization method. Moreover, we present a novel SI and massive MIMO interference channel aware power allocation scheme to include the optimal power control. Simulation results show significant performance improvement compared to a traditional bidirectional fully digital half-duplex (HD) system. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2108.00465v2-abstract-full').style.display = 'none'; document.getElementById('2108.00465v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 4 January, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 1 August, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2021. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2104.12367">arXiv:2104.12367</a> <span> [<a href="https://arxiv.org/pdf/2104.12367">pdf</a>, <a href="https://arxiv.org/format/2104.12367">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Information Theory">cs.IT</span> </div> </div> <p class="title is-5 mathjax"> Game-Theoretic Mode Scheduling for Dynamic TDD in 5G Systems </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Badia%2C+L">Leonardo Badia</a>, <a href="/search/eess?searchtype=author&query=Tomasin%2C+S">Stefano Tomasin</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2104.12367v1-abstract-short" style="display: inline;"> Dynamic time-division duplexing (TDD) enables independent uplink/downlink mode scheduling at each cell, based on the local traffic. However, this creates cross-interference among cells. Thus, the joint power allocation and scheduling problem becomes mixed-integer non-convex and turns out to be NP-hard. We propose a low-complexity and decentralized solution, where power allocation and scheduling ar… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2104.12367v1-abstract-full').style.display = 'inline'; document.getElementById('2104.12367v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2104.12367v1-abstract-full" style="display: none;"> Dynamic time-division duplexing (TDD) enables independent uplink/downlink mode scheduling at each cell, based on the local traffic. However, this creates cross-interference among cells. Thus, the joint power allocation and scheduling problem becomes mixed-integer non-convex and turns out to be NP-hard. We propose a low-complexity and decentralized solution, where power allocation and scheduling are decoupled. First, power is allocated in a decentralized fashion, and then modes are scheduled by a non-cooperative game to achieve the mixed-strategy Nash equilibrium. We consider two possible approaches to compute the payoffs in the game, according to the cross-interference power model and the entailed communication overhead among cells. Simulation results are presented for an outdoor dense small-cell scenario, showing that our approaches outperform static TDD significantly. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2104.12367v1-abstract-full').style.display = 'none'; document.getElementById('2104.12367v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 April, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2021. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2104.11537">arXiv:2104.11537</a> <span> [<a href="https://arxiv.org/pdf/2104.11537">pdf</a>, <a href="https://arxiv.org/format/2104.11537">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Information Theory">cs.IT</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> </div> </div> <p class="title is-5 mathjax"> Practical Hybrid Beamforming for Millimeter Wave Massive MIMO Full Duplex with Limited Dynamic Range </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/eess?searchtype=author&query=Sheemar%2C+C+K">Chandan Kumar Sheemar</a>, <a href="/search/eess?searchtype=author&query=Thomas%2C+C+K">Christo Kurisummoottil Thomas</a>, <a href="/search/eess?searchtype=author&query=Slock%2C+D">Dirk Slock</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2104.11537v7-abstract-short" style="display: inline;"> Full Duplex (FD) radio has emerged as a promising solution to increase the data rates by up to a factor of two via simultaneous transmission and reception in the same frequency band. This paper studies a novel hybrid beamforming (HYBF) design to maximize the weighted sum-rate (WSR) in a single-cell millimeter wave (mmWave) massive multiple-input-multiple-output (mMIMO) FD system. Motivated by prac… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2104.11537v7-abstract-full').style.display = 'inline'; document.getElementById('2104.11537v7-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2104.11537v7-abstract-full" style="display: none;"> Full Duplex (FD) radio has emerged as a promising solution to increase the data rates by up to a factor of two via simultaneous transmission and reception in the same frequency band. This paper studies a novel hybrid beamforming (HYBF) design to maximize the weighted sum-rate (WSR) in a single-cell millimeter wave (mmWave) massive multiple-input-multiple-output (mMIMO) FD system. Motivated by practical considerations, we assume that the multi-antenna users and hybrid FD base station (BS) suffer from the limited dynamic range (LDR) noise due to non-ideal hardware and an impairment aware HYBF approach is adopted by integrating the traditional LDR noise model in the mmWave band. In contrast to the conventional HYBF schemes, our design also considers the joint sum-power and the practical per-antenna power constraints. A novel interference, self-interference (SI) and LDR noise aware optimal power allocation scheme for the uplink (UL) users and FD BS is also presented to satisfy the joint constraints. The maximum achievable gain of a multi-user mmWave FD system over a fully digital half duplex (HD) system with different LDR noise levels and numbers of the radio-frequency (RF) chains is investigated. Simulation results show that our design outperforms the HD system with only a few RF chains at any LDR noise level. The advantage of having amplitude control at the analog stage is also examined, and additional gain for the mmWave FD system becomes evident when the number of RF chains at the hybrid FD BS is small. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2104.11537v7-abstract-full').style.display = 'none'; document.getElementById('2104.11537v7-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 3 January, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 23 April, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2021. </p> </li> </ol> <div class="is-hidden-tablet">  <span class="help" style="display: inline-block;"><a href="https://github.com/arXiv/arxiv-search/releases">Search v0.5.6 released 2020-02-24</a>  </span> </div> </div> </main> <footer> <div 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