Pub Date : 2024-11-18DOI: 10.1109/OJCOMS.2024.3500782
Tianle Liu;Khawaja Fahad Masood;Jun Tong;Jiguang He;and Jiangtao Xi
This paper studies the estimation of low-rank multiple-input multiple-output (MIMO) wideband channels in orthogonal frequency division multiplexing (OFDM) systems which are commonly considered for high-frequency wireless communications, e.g., at millimeter wave (mmWave) and Terahertz (THz) bands. To reduce the overhead for channel estimation, we propose a novel solution based on two-fold sampling of the original channel matrix. A subchannel associated with a subset of subcarriers and antennas is first selected by deterministic sampling. Low-rank matrix completion (LRMC) based on random sampling is then used to further reduce the training overhead. Utilizing the Toeplitz structure of the covariance matrices of uniform linear arrays, the angles and delays are then estimated separately at low complexities using super-resolution algorithms. Finally, the path gains are estimated and associated with the path angles and delays, followed by the extrapolation of the full-dimensional channel. As only a small number of antennas and subcarriers are required in the training, the overall training overhead and computational complexity are very low. Numerical results demonstrate that the proposed two-fold sampling-based estimator can achieve high-accuracy channel estimation. Besides, the sampling patterns and complexity of the proposed estimator are analysed, which shows that the proposed solution can be configured to provide different performance-complexity tradeoffs.
{"title":"Two-Fold Sampling-Based Super-Resolution Estimation of Low-Rank MIMO-OFDM Channels","authors":"Tianle Liu;Khawaja Fahad Masood;Jun Tong;Jiguang He;and Jiangtao Xi","doi":"10.1109/OJCOMS.2024.3500782","DOIUrl":"https://doi.org/10.1109/OJCOMS.2024.3500782","url":null,"abstract":"This paper studies the estimation of low-rank multiple-input multiple-output (MIMO) wideband channels in orthogonal frequency division multiplexing (OFDM) systems which are commonly considered for high-frequency wireless communications, e.g., at millimeter wave (mmWave) and Terahertz (THz) bands. To reduce the overhead for channel estimation, we propose a novel solution based on two-fold sampling of the original channel matrix. A subchannel associated with a subset of subcarriers and antennas is first selected by deterministic sampling. Low-rank matrix completion (LRMC) based on random sampling is then used to further reduce the training overhead. Utilizing the Toeplitz structure of the covariance matrices of uniform linear arrays, the angles and delays are then estimated separately at low complexities using super-resolution algorithms. Finally, the path gains are estimated and associated with the path angles and delays, followed by the extrapolation of the full-dimensional channel. As only a small number of antennas and subcarriers are required in the training, the overall training overhead and computational complexity are very low. Numerical results demonstrate that the proposed two-fold sampling-based estimator can achieve high-accuracy channel estimation. Besides, the sampling patterns and complexity of the proposed estimator are analysed, which shows that the proposed solution can be configured to provide different performance-complexity tradeoffs.","PeriodicalId":33803,"journal":{"name":"IEEE Open Journal of the Communications Society","volume":"5 ","pages":"7434-7446"},"PeriodicalIF":6.3,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10755153","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142777615","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-18DOI: 10.1109/OJCOMS.2024.3500777
Mahmoud M. Salim;Suhail I. Al-Dharrab;Daniel Benevides da Costa;Ali H. Muqaibel
This paper investigates the tradeoff between sum-rate and energy efficiency in cognitive cooperative non-orthogonal multiple access (C-NOMA) with spectrum sharing. In C-NOMA networks for this study, we consider a multi-antenna secondary source and full-duplex relays equipped with power splitting (PS)-based radio frequency (RF) and renewable energy harvesting capabilities. Practical aspects such as full-duplex self-interference, non-linear RF energy harvesting (EH), hardware impairments, imperfections in channel state information and successive interference cancellation are incorporated into the model. We formulate two nonconvex mixed-integer nonlinear programming objective functions to maximize sum-rate and energy efficiency of the C-NOMA network, meeting IoT service requirements. These functions consider transmit power, PS factor for RF harvesting, NOMA power coefficients, qualityof- service, and EH constraints. Specifically, we propose the practical cognitive C-NOMA with EH (PCCN-EH) algorithm. It identifies and selects the best channel gain for relays from the multiple antennas at the secondary source. Relying on particle swarm optimization, we optimize transmit powers, PS factor, and power coefficients. We propose a novel relay selection scheme employing the relay optimization circle. Furthermore, we examine the computational complexity of the PCCN-EH algorithm, demonstrating a manageable complexity with efficiency and feasibility for practical deployment. Through extensive simulations, the proposed PCCN-EH algorithm demonstrates significant performance in sum-rate and energy efficiency across various scenarios, showing remarkable results against benchmarks.
{"title":"Rate-Energy Optimization for Hybrid-Powered Full-Duplex Relays in Cognitive C-NOMA With Impairments","authors":"Mahmoud M. Salim;Suhail I. Al-Dharrab;Daniel Benevides da Costa;Ali H. Muqaibel","doi":"10.1109/OJCOMS.2024.3500777","DOIUrl":"https://doi.org/10.1109/OJCOMS.2024.3500777","url":null,"abstract":"This paper investigates the tradeoff between sum-rate and energy efficiency in cognitive cooperative non-orthogonal multiple access (C-NOMA) with spectrum sharing. In C-NOMA networks for this study, we consider a multi-antenna secondary source and full-duplex relays equipped with power splitting (PS)-based radio frequency (RF) and renewable energy harvesting capabilities. Practical aspects such as full-duplex self-interference, non-linear RF energy harvesting (EH), hardware impairments, imperfections in channel state information and successive interference cancellation are incorporated into the model. We formulate two nonconvex mixed-integer nonlinear programming objective functions to maximize sum-rate and energy efficiency of the C-NOMA network, meeting IoT service requirements. These functions consider transmit power, PS factor for RF harvesting, NOMA power coefficients, qualityof- service, and EH constraints. Specifically, we propose the practical cognitive C-NOMA with EH (PCCN-EH) algorithm. It identifies and selects the best channel gain for relays from the multiple antennas at the secondary source. Relying on particle swarm optimization, we optimize transmit powers, PS factor, and power coefficients. We propose a novel relay selection scheme employing the relay optimization circle. Furthermore, we examine the computational complexity of the PCCN-EH algorithm, demonstrating a manageable complexity with efficiency and feasibility for practical deployment. Through extensive simulations, the proposed PCCN-EH algorithm demonstrates significant performance in sum-rate and energy efficiency across various scenarios, showing remarkable results against benchmarks.","PeriodicalId":33803,"journal":{"name":"IEEE Open Journal of the Communications Society","volume":"5 ","pages":"7419-7433"},"PeriodicalIF":6.3,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10755121","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142777686","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-18DOI: 10.1109/OJCOMS.2024.3501856
Dogan Kutay Pekcan;Hongyi Liao;Ender Ayanoglu
To maximize the received power at a user equipment, the problem of optimizing a reconfigurable intelligent surface (RIS) with a limited phase range and nonuniform discrete phase shifts with adjustable gains is addressed. Necessary and sufficient conditions to achieve this maximization are given. These conditions are employed in two algorithms to achieve the global optimum in linear time. Depending on the phase range limitation, it is shown that the global optimality is achieved in NK or fewer and $N(K+1)$ or fewer steps, where N is the number of RIS elements and K is the number of discrete phase shifts which may be placed nonuniformly over the limited phase range. In addition, we define two quantization algorithms that we call nonuniform polar quantization (NPQ) algorithm and extended nonuniform polar quantization (ENPQ) algorithm, where the latter is a novel quantization algorithm for RISs with a significant phase range restriction. With NPQ, we provide a closed-form solution for the approximation ratio with which an arbitrary set of nonuniform discrete phase shifts can approximate the continuous solution. We also show that with a phase range limitation, equal separation among the nonuniform discrete phase shifts maximizes the normalized performance. Furthermore, for a larger RIS phase range limitation, we show that the gain of increasing K is only marginal, whereas, ON/OFF selection for the RIS elements can bring significant performance compared to the case when the RIS elements are strictly ON.
{"title":"Received Power Maximization Using Nonuniform Discrete Phase Shifts for RISs With a Limited Phase Range","authors":"Dogan Kutay Pekcan;Hongyi Liao;Ender Ayanoglu","doi":"10.1109/OJCOMS.2024.3501856","DOIUrl":"https://doi.org/10.1109/OJCOMS.2024.3501856","url":null,"abstract":"To maximize the received power at a user equipment, the problem of optimizing a reconfigurable intelligent surface (RIS) with a limited phase range and nonuniform discrete phase shifts with adjustable gains is addressed. Necessary and sufficient conditions to achieve this maximization are given. These conditions are employed in two algorithms to achieve the global optimum in linear time. Depending on the phase range limitation, it is shown that the global optimality is achieved in NK or fewer and \u0000<inline-formula> <tex-math>$N(K+1)$ </tex-math></inline-formula>\u0000 or fewer steps, where N is the number of RIS elements and K is the number of discrete phase shifts which may be placed nonuniformly over the limited phase range. In addition, we define two quantization algorithms that we call nonuniform polar quantization (NPQ) algorithm and extended nonuniform polar quantization (ENPQ) algorithm, where the latter is a novel quantization algorithm for RISs with a significant phase range restriction. With NPQ, we provide a closed-form solution for the approximation ratio with which an arbitrary set of nonuniform discrete phase shifts can approximate the continuous solution. We also show that with a phase range limitation, equal separation among the nonuniform discrete phase shifts maximizes the normalized performance. Furthermore, for a larger RIS phase range limitation, we show that the gain of increasing K is only marginal, whereas, ON/OFF selection for the RIS elements can bring significant performance compared to the case when the RIS elements are strictly ON.","PeriodicalId":33803,"journal":{"name":"IEEE Open Journal of the Communications Society","volume":"5 ","pages":"7447-7466"},"PeriodicalIF":6.3,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10756629","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142777838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-14DOI: 10.1109/OJCOMS.2024.3499370
Giuseppe Caso;Mohammad Rajiullah;Konstantinos Kousias;Usman Ali;Nadir Bouzar;Luca De Nardis;Anna Brunstrom;Ozgu Alay;Marco Neri;Maria-Gabriella Di Benedetto
Fifth Generation (5G) systems have been commercially available worldwide for at least a couple of years, with mid-band Non-Standalone (NSA) being the deployment mode preferred by Mobile Network Operators (MNOs). Empirical analyses have provided so far key insights on 5G NSA performance from different perspectives, but most of these works consider short time periods to drive conclusions. In this paper, we investigate the evolution of 5G NSA considering deployment, performance, and services, including positioning. We perform a large-scale measurement campaign in two phases (2021 and 2023), covering six MNOs in two European countries, Italy and Sweden. Our results show significant differences in network deployment and performance, with increasing network density and frequencies but, at times, decreasing downlink throughput performance. For the latter, we identify worse radio coverage and connectivity issues as root causes. By using a standardized methodology, we also evaluate the performance of new services such as real-time gaming and augmented/virtual reality, and reveal that stable 5G connectivity is key to meet their requirements. Similarly, we highlight the negative effects of roaming on performance. Finally, we evaluate 5G fingerprinting positioning systems and show that a higher accuracy is achievable in denser 5G deployments.
{"title":"The Chronicles of 5G Non-Standalone: An Empirical Analysis of Performance and Service Evolution","authors":"Giuseppe Caso;Mohammad Rajiullah;Konstantinos Kousias;Usman Ali;Nadir Bouzar;Luca De Nardis;Anna Brunstrom;Ozgu Alay;Marco Neri;Maria-Gabriella Di Benedetto","doi":"10.1109/OJCOMS.2024.3499370","DOIUrl":"https://doi.org/10.1109/OJCOMS.2024.3499370","url":null,"abstract":"Fifth Generation (5G) systems have been commercially available worldwide for at least a couple of years, with mid-band Non-Standalone (NSA) being the deployment mode preferred by Mobile Network Operators (MNOs). Empirical analyses have provided so far key insights on 5G NSA performance from different perspectives, but most of these works consider short time periods to drive conclusions. In this paper, we investigate the evolution of 5G NSA considering deployment, performance, and services, including positioning. We perform a large-scale measurement campaign in two phases (2021 and 2023), covering six MNOs in two European countries, Italy and Sweden. Our results show significant differences in network deployment and performance, with increasing network density and frequencies but, at times, decreasing downlink throughput performance. For the latter, we identify worse radio coverage and connectivity issues as root causes. By using a standardized methodology, we also evaluate the performance of new services such as real-time gaming and augmented/virtual reality, and reveal that stable 5G connectivity is key to meet their requirements. Similarly, we highlight the negative effects of roaming on performance. Finally, we evaluate 5G fingerprinting positioning systems and show that a higher accuracy is achievable in denser 5G deployments.","PeriodicalId":33803,"journal":{"name":"IEEE Open Journal of the Communications Society","volume":"5 ","pages":"7380-7399"},"PeriodicalIF":6.3,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10753472","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142777884","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-14DOI: 10.1109/OJCOMS.2024.3498334
Moatasim Mahmoud;Stamatia Rizou;Andreas S. Panayides;Nikolaos V. Kantartzis;George K. Karagiannidis;Pavlos I. Lazaridis;Zaharias D. Zaharis
360° videos and virtual reality (VR) are among the defining applications for a new era of immersive multimedia technologies. However, streaming high-quality 360° videos constitutes a challenge for service providers and network operators, especially in multi-user scenarios. The massive data rates and the unique features of omnidirectional videos necessitate the development of novel streaming techniques. In this paper, we propose an optimized multi-user tiled 360° video streaming framework. Specifically, we formulate the problem of tile quality selection in multi-user bandwidth-constrained communications and propose an algorithm that assigns the quality levels of transmitted tiles. The proposed framework is designed to maximize the perceived quality within the users’ viewports by considering 360° video quality assessment (360° VQA) metrics and tile viewing percentages. To simulate our solution in practical settings, we employ a long short-term memory (LSTM) model to perform viewport prediction and make the assessment based on real-life viewing data. Simulation results of our proposed framework show significant improvement in the delivered viewports’ quality and robustness against increasing the number of users.
{"title":"Optimized Tile Quality Selection in Multi-User 360° Video Streaming","authors":"Moatasim Mahmoud;Stamatia Rizou;Andreas S. Panayides;Nikolaos V. Kantartzis;George K. Karagiannidis;Pavlos I. Lazaridis;Zaharias D. Zaharis","doi":"10.1109/OJCOMS.2024.3498334","DOIUrl":"https://doi.org/10.1109/OJCOMS.2024.3498334","url":null,"abstract":"360° videos and virtual reality (VR) are among the defining applications for a new era of immersive multimedia technologies. However, streaming high-quality 360° videos constitutes a challenge for service providers and network operators, especially in multi-user scenarios. The massive data rates and the unique features of omnidirectional videos necessitate the development of novel streaming techniques. In this paper, we propose an optimized multi-user tiled 360° video streaming framework. Specifically, we formulate the problem of tile quality selection in multi-user bandwidth-constrained communications and propose an algorithm that assigns the quality levels of transmitted tiles. The proposed framework is designed to maximize the perceived quality within the users’ viewports by considering 360° video quality assessment (360° VQA) metrics and tile viewing percentages. To simulate our solution in practical settings, we employ a long short-term memory (LSTM) model to perform viewport prediction and make the assessment based on real-life viewing data. Simulation results of our proposed framework show significant improvement in the delivered viewports’ quality and robustness against increasing the number of users.","PeriodicalId":33803,"journal":{"name":"IEEE Open Journal of the Communications Society","volume":"5 ","pages":"7301-7316"},"PeriodicalIF":6.3,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10753298","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142713778","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In most multiple-input multiple-output (MIMO) communication systems, antennas are spaced at least half a wavelength apart to reduce mutual coupling. In this configuration, the maximum array gain is equal to the number of antennas. However, when the antenna spacing is significantly reduced, the array gain of a compact array can become proportional to the square of the number of antennas, greatly exceeding that of traditional MIMO systems. Achieving this “superdirectivity” requires complex calculations of the excitation coefficients (beamforming vector), which is a challenging task. In this paper, we address this problem with a novel double coupling-based superdirective beamforming method. In particular, we categorize the antenna coupling effects to impedance coupling and field coupling. By characterizing these two coupling in model, we derive the beamforming vector for superdirective arrays. We prove that the field coupling matrix has the unique solution for an antenna array, and itself has the ability to fully characterize the distorted coupling field. Based on this proven theorem, we propose a method that accurately calculates the coupling matrix using only a number of angle sampling points on the order of the number of antennas. Moreover, a prototype of an independently-controlled superdirective antenna array is developed. Full-wave electromagnetic simulations and real-world experiments validate the effectiveness of our proposed approaches, and superdirectivity is achieved in reality by a compact array with 4 and 8 dipole antennas.
{"title":"A Superdirective Beamforming Approach With Impedance Coupling and Field Coupling for Compact Antenna Arrays","authors":"Liangcheng Han;Haifan Yin;Mengying Gao;Jingcheng Xie","doi":"10.1109/OJCOMS.2024.3497985","DOIUrl":"https://doi.org/10.1109/OJCOMS.2024.3497985","url":null,"abstract":"In most multiple-input multiple-output (MIMO) communication systems, antennas are spaced at least half a wavelength apart to reduce mutual coupling. In this configuration, the maximum array gain is equal to the number of antennas. However, when the antenna spacing is significantly reduced, the array gain of a compact array can become proportional to the square of the number of antennas, greatly exceeding that of traditional MIMO systems. Achieving this “superdirectivity” requires complex calculations of the excitation coefficients (beamforming vector), which is a challenging task. In this paper, we address this problem with a novel double coupling-based superdirective beamforming method. In particular, we categorize the antenna coupling effects to impedance coupling and field coupling. By characterizing these two coupling in model, we derive the beamforming vector for superdirective arrays. We prove that the field coupling matrix has the unique solution for an antenna array, and itself has the ability to fully characterize the distorted coupling field. Based on this proven theorem, we propose a method that accurately calculates the coupling matrix using only a number of angle sampling points on the order of the number of antennas. Moreover, a prototype of an independently-controlled superdirective antenna array is developed. Full-wave electromagnetic simulations and real-world experiments validate the effectiveness of our proposed approaches, and superdirectivity is achieved in reality by a compact array with 4 and 8 dipole antennas.","PeriodicalId":33803,"journal":{"name":"IEEE Open Journal of the Communications Society","volume":"5 ","pages":"7262-7277"},"PeriodicalIF":6.3,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10753354","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142713959","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Scalable optical wireless networks are crucial to address the demand for ultra-broadband wireless connectivity in future workspaces and living environments. This study presents a novel theoretical framework for the dual-carrier modular optical phased array (MOPA) architecture, specifically tailored for indoor wireless communication networks. We introduce the non-uniform spherical wave (NUSW) model for a near-field analysis of electromagnetic radiation in a single-carrier MOPA, extending this to dual-carrier configurations. Our analysis demonstrates enhanced beam-focusing capabilities and significant suppression of grating lobes in the dual-carrier system. Expanding on this theoretical model, we perform a comprehensive numerical analysis of a dual-carrier MOPA system installed on a planar ceiling within an indoor room. To quantitatively assess grating lobe suppression, we propose a novel figure-of-merit (FoM) and compare the beam-focusing performance of both single- and dual-carrier MOPA systems. Furthermore, we introduce a new symmetrical excitation mechanism combined with spatial modulation for data symbol encoding within the MOPA architecture. Our results reveal that this approach provides high-level physical layer security (PLS) for wireless communication. By integrating amplitude shift keying (ASK) with spatial modulation, we evaluate the bit error rate (BER) against signal-to-noise (SNR) ratio across different symmetrical excitation scenarios. This evaluation demonstrates that our system achieves efficient digital signal communication with reduced complexity and robust performance under real-world noise conditions. Our findings advance the understanding of optical phased array systems and underscore their potential for secure, high-performance indoor wireless communication.
{"title":"Symmetrical Modular Optical Phased Array With Combined Spatial and Amplitude Modulation for Scalable Indoor Wireless Networks","authors":"Kosala Herath;Malin Premaratne;Sharadhi Gunathilake;Ampalavanapillai Nirmalathas","doi":"10.1109/OJCOMS.2024.3496866","DOIUrl":"https://doi.org/10.1109/OJCOMS.2024.3496866","url":null,"abstract":"Scalable optical wireless networks are crucial to address the demand for ultra-broadband wireless connectivity in future workspaces and living environments. This study presents a novel theoretical framework for the dual-carrier modular optical phased array (MOPA) architecture, specifically tailored for indoor wireless communication networks. We introduce the non-uniform spherical wave (NUSW) model for a near-field analysis of electromagnetic radiation in a single-carrier MOPA, extending this to dual-carrier configurations. Our analysis demonstrates enhanced beam-focusing capabilities and significant suppression of grating lobes in the dual-carrier system. Expanding on this theoretical model, we perform a comprehensive numerical analysis of a dual-carrier MOPA system installed on a planar ceiling within an indoor room. To quantitatively assess grating lobe suppression, we propose a novel figure-of-merit (FoM) and compare the beam-focusing performance of both single- and dual-carrier MOPA systems. Furthermore, we introduce a new symmetrical excitation mechanism combined with spatial modulation for data symbol encoding within the MOPA architecture. Our results reveal that this approach provides high-level physical layer security (PLS) for wireless communication. By integrating amplitude shift keying (ASK) with spatial modulation, we evaluate the bit error rate (BER) against signal-to-noise (SNR) ratio across different symmetrical excitation scenarios. This evaluation demonstrates that our system achieves efficient digital signal communication with reduced complexity and robust performance under real-world noise conditions. Our findings advance the understanding of optical phased array systems and underscore their potential for secure, high-performance indoor wireless communication.","PeriodicalId":33803,"journal":{"name":"IEEE Open Journal of the Communications Society","volume":"5 ","pages":"7317-7340"},"PeriodicalIF":6.3,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10752674","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142713958","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-13DOI: 10.1109/OJCOMS.2024.3497799
Sirine Ben Ati;Hayssam Dahrouj;Mohamed-Slim Alouini
Given the drastic demand for stringent digital services, augmenting terrestrial communications with satellite services promises to meet the rush-to-gold-like demand for scarce radio resources. Our paper investigates the problem of coexisting satellite-ground networks consisting of several satellites and several ground base-stations, all operating at the millimeter-wave band. Such coexistence of space and ground communications becomes prone to wireless interference, and so the cross-development of intelligent resource allocation techniques becomes indispensable for assessing the benefit of such hybrid space-ground networks. The paper assumes that a fraction of the ground base-stations connects to a centralized computing processor (i.e., cloud) using fronthaul links with limited capacity. The paper further assumes that each satellite connects with its own earth-station, which in turn connects with a ground base-station, hereafter denoted by satellite-associated base-station, that aims at serving a part of the ground-users. The system performance depends, therefore, on both the intra- and inter-mode interference between the satellites and cloud-connected base-stations, and the integrated access-backhaul interference between the satellite to earth-station and satellite-associated base-station to users. The paper then aims at maximizing the sum rate of the considered network under power, user-connectivity, and ground fronthaul constraints, in order to jointly determine the satellite-associated base-stations and cloud-connected base-stations served users’ beamforming vectors. The paper addresses such an intricate non-convex optimization problem using a combination of well-chosen inner convex approximations, coupled with proper outer loop correction steps. The numerical simulations show how effective our proposed algorithm is at mitigating the system multi-mode interference, particularly in congested networks.
{"title":"Interference Mitigation in Coexisting Satellites and Cloud-Assisted Ground Networks in the mmWave Band","authors":"Sirine Ben Ati;Hayssam Dahrouj;Mohamed-Slim Alouini","doi":"10.1109/OJCOMS.2024.3497799","DOIUrl":"https://doi.org/10.1109/OJCOMS.2024.3497799","url":null,"abstract":"Given the drastic demand for stringent digital services, augmenting terrestrial communications with satellite services promises to meet the rush-to-gold-like demand for scarce radio resources. Our paper investigates the problem of coexisting satellite-ground networks consisting of several satellites and several ground base-stations, all operating at the millimeter-wave band. Such coexistence of space and ground communications becomes prone to wireless interference, and so the cross-development of intelligent resource allocation techniques becomes indispensable for assessing the benefit of such hybrid space-ground networks. The paper assumes that a fraction of the ground base-stations connects to a centralized computing processor (i.e., cloud) using fronthaul links with limited capacity. The paper further assumes that each satellite connects with its own earth-station, which in turn connects with a ground base-station, hereafter denoted by satellite-associated base-station, that aims at serving a part of the ground-users. The system performance depends, therefore, on both the intra- and inter-mode interference between the satellites and cloud-connected base-stations, and the integrated access-backhaul interference between the satellite to earth-station and satellite-associated base-station to users. The paper then aims at maximizing the sum rate of the considered network under power, user-connectivity, and ground fronthaul constraints, in order to jointly determine the satellite-associated base-stations and cloud-connected base-stations served users’ beamforming vectors. The paper addresses such an intricate non-convex optimization problem using a combination of well-chosen inner convex approximations, coupled with proper outer loop correction steps. The numerical simulations show how effective our proposed algorithm is at mitigating the system multi-mode interference, particularly in congested networks.","PeriodicalId":33803,"journal":{"name":"IEEE Open Journal of the Communications Society","volume":"5 ","pages":"7483-7497"},"PeriodicalIF":6.3,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10752513","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142777845","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-13DOI: 10.1109/OJCOMS.2024.3496934
Swaroop Gopalam;Dhanushka Kudathanthirige;Iain B. Collings;Stephen V. Hanly;Hazer Inaltekin;Philip Whiting
Low Earth Orbit (LEO) satellites are increasingly being used to provide connectivity for wide area Internet of Things (IoT) sensing applications. Distributed IoT terminals are not able to coordinate their uplink transmissions to the nano-satellites, and so operate in a grant-free mode. Quality-of-Service (QoS) depends on the transmission attempt success statistics, which are time-varying. This paper presents asymptotic analysis results that characterize the IoT terminal’s transmission success process. We show that it converges to an inhomogeneous Poisson process, in the large population regime, and characterize the time-dependent intensity as a function of the terminal location and the attempt rate scheme. We also propose three terminal attempt rate schemes that are solutions to max-min optimization problems. The performance of the proposed schemes are compared in terms of individual terminal QoS as well as the population-wide QoS distribution. Performance for various IoT applications is also presented.
{"title":"Distributed IoT Communications With LEO Satellites: QoS Performance and Terminal Attempt Rate Schemes","authors":"Swaroop Gopalam;Dhanushka Kudathanthirige;Iain B. Collings;Stephen V. Hanly;Hazer Inaltekin;Philip Whiting","doi":"10.1109/OJCOMS.2024.3496934","DOIUrl":"https://doi.org/10.1109/OJCOMS.2024.3496934","url":null,"abstract":"Low Earth Orbit (LEO) satellites are increasingly being used to provide connectivity for wide area Internet of Things (IoT) sensing applications. Distributed IoT terminals are not able to coordinate their uplink transmissions to the nano-satellites, and so operate in a grant-free mode. Quality-of-Service (QoS) depends on the transmission attempt success statistics, which are time-varying. This paper presents asymptotic analysis results that characterize the IoT terminal’s transmission success process. We show that it converges to an inhomogeneous Poisson process, in the large population regime, and characterize the time-dependent intensity as a function of the terminal location and the attempt rate scheme. We also propose three terminal attempt rate schemes that are solutions to max-min optimization problems. The performance of the proposed schemes are compared in terms of individual terminal QoS as well as the population-wide QoS distribution. Performance for various IoT applications is also presented.","PeriodicalId":33803,"journal":{"name":"IEEE Open Journal of the Communications Society","volume":"5 ","pages":"7400-7418"},"PeriodicalIF":6.3,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10752551","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142777747","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-13DOI: 10.1109/OJCOMS.2024.3496872
Nourah S. AlOtaibi;Muhamad Felemban;Sajjad Mahmood
Federated Learning (FL) has transformed machine learning by facilitating decentralized, privacy-focused data processing. Despite its advantages, FL remains vulnerable to data poisoning attacks, particularly Label-Flipping Attacks (LFA). In LFA, malicious clients deliberately mislabel local data, causing the global model to misclassify certain classes, thus undermining its integrity. Although centralized detection methods have been explored, there is a notable gap in addressing LFA within the decentralized Client-Edge-Cloud architecture, which is crucial for FL systems. This study introduces an innovative edge-assisted framework for early detection of LFA, crucial for real-time applications. To our knowledge, this is the first study to propose such an edge-assisted LFA detection mechanism. Through detailed conceptual and empirical analyses of LFA behavior, we identified a key characteristic: class-wise accuracy, particularly recall for specific classes, decreases due to label flipping, significantly increases the delta discrepancy with the edge model. Our method remains effective across varying numbers of malicious clients and model sizes, without requiring prior knowledge about the malicious clients. We developed two mitigation strategies: (1) the Zero Tolerance approach, which excludes entire client updates upon detecting adversarial behavior, and (2) the Zero Masking approach, which zeros out gradients for the flipped class while preserving others. This method leverages the direct influence of final layer gradients on class predictions. Extensive evaluation using three benchmark datasets shows that the proposed edge-assisted LFA detection framework outperforms traditional cloud-based methods. We demonstrate its superiority in latency, resource efficiency, and accuracy in detecting malicious clients, outperforming state-of-the-art defenses.
{"title":"Edge-Assisted Label-Flipping Attack Detection in Federated Learning","authors":"Nourah S. AlOtaibi;Muhamad Felemban;Sajjad Mahmood","doi":"10.1109/OJCOMS.2024.3496872","DOIUrl":"https://doi.org/10.1109/OJCOMS.2024.3496872","url":null,"abstract":"Federated Learning (FL) has transformed machine learning by facilitating decentralized, privacy-focused data processing. Despite its advantages, FL remains vulnerable to data poisoning attacks, particularly Label-Flipping Attacks (LFA). In LFA, malicious clients deliberately mislabel local data, causing the global model to misclassify certain classes, thus undermining its integrity. Although centralized detection methods have been explored, there is a notable gap in addressing LFA within the decentralized Client-Edge-Cloud architecture, which is crucial for FL systems. This study introduces an innovative edge-assisted framework for early detection of LFA, crucial for real-time applications. To our knowledge, this is the first study to propose such an edge-assisted LFA detection mechanism. Through detailed conceptual and empirical analyses of LFA behavior, we identified a key characteristic: class-wise accuracy, particularly recall for specific classes, decreases due to label flipping, significantly increases the delta discrepancy with the edge model. Our method remains effective across varying numbers of malicious clients and model sizes, without requiring prior knowledge about the malicious clients. We developed two mitigation strategies: (1) the Zero Tolerance approach, which excludes entire client updates upon detecting adversarial behavior, and (2) the Zero Masking approach, which zeros out gradients for the flipped class while preserving others. This method leverages the direct influence of final layer gradients on class predictions. Extensive evaluation using three benchmark datasets shows that the proposed edge-assisted LFA detection framework outperforms traditional cloud-based methods. We demonstrate its superiority in latency, resource efficiency, and accuracy in detecting malicious clients, outperforming state-of-the-art defenses.","PeriodicalId":33803,"journal":{"name":"IEEE Open Journal of the Communications Society","volume":"5 ","pages":"7278-7300"},"PeriodicalIF":6.3,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10752632","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142713961","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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