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Performance of Double-Stacked Intelligent Metasurface-Assisted Multiuser Massive MIMO Communications in the Wave Domain

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IEEE Transactions on Wireless Communications 2025年第5期24卷 4205-4218页

作者： Papazafeiropoulos, Anastasios Kourtessis, Pandelis Chatzinotas, Symeon Kaklamani, Dimitra I. Venieris, Iakovos S. University of Hertfordshire Communications and Intelligent Systems Research Group HatfieldAL10 9AB United Kingdom SnT at the University of Luxembourg Luxembourg University of Hertfordshire Communications and Intelligent Systems Research Group HatfieldAL10 9AB United Kingdom School of Electrical and Computer Engineering National Technical University of Athens Microwave and Fiber Optics Laboratory Intelligent Communications and Broadband Networks Laboratory Zografou Athens15780 Greece

Although reconfigurable intelligent surface (RIS) is a promising technology for shaping the propagation environment, it consists of a single-layer structure within inherent limitations regarding the number of beam steering patterns. Based on the recently revolutionary technology, denoted as stacked intelligent metasurface (SIM), we propose its implementation not only on the base station (BS) side in a massive multiple-input multiple-output (mMIMO) setup but also in the intermediate space between the base station and the users to adjust the environment further as needed. For the sake of convenience, we call the former BS SIM (BSIM), and the latter channel SIM (CSIM). To this end, we achieve hybrid wave-based combining at the BS and wave-based configuration at the intermediate space. Specifically, we propose a channel estimation method with reduced overhead, being crucial for SIM-assisted communications. Next, we derive the uplink sum spectral efficiency (SE) in closed form in terms of statistical channel state information (CSI). Notably, we optimize the phase shifts of both BSIM and CSIM simultaneously by using the projected gradient ascent method (PGAM). Compared to previous works on SIMs, we study the uplink transmission in a mMIMO setup, channel estimation in a single phase, a second SIM at the intermediate space, and simultaneous optimization of the two SIMs. Simulation results show the impact of various parameters on the sum SE, and demonstrate the superiority of our optimization approach compared to the alternating optimization (AO) method. © 2002-2012 IEEE.

关键词： Channel state information

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Channel Estimation for Stacked Intelligent Metasurfaces in Rician Fading Channels

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IEEE Wireless Communications Letters 2025年第5期14卷 1411-1415页

作者： Papazafeiropoulos, Anastasios Kourtessis, Pandelis Kaklamani, Dimitra I. Venieris, Iakovos S. University of Hertfordshire Communications and Intelligent Systems Research Group HatfieldAL10 9AB United Kingdom Microwave and Fiber Optics Laboratory Greece National Technical University of Athens Intelligent Communications and Broadband Networks Laboratory School of Electrical and Computer Engineering Zografou Athens15780 Greece

The recent combination of the rising architectures, known as stacked intelligent metasurface (SIM) and holographic multiple-input multiple-output (HMIMO), drives toward breakthroughs for next-generation wireless communication systems. Given the fact that the number of elements per surface of the SIM is much larger than the base station (BS) antennas, the acquisition of the channel state information (CSI) in SIM-aided multi-user systems is challenging, especially when a line-of-sight (LoS) component is present. Thus, in this letter, we address the channel procedure under conditions of Rician fading by proposing a protocol in terms of a minimum mean square error (MMSE) estimator for wave-based design in a single phase. Moreover, we derive the normalized mean square error (NMSE) of the suggested estimator, and provide the optimal phase shifts minimising the NMSE. Numerical results illustrate the performance of the new channel estimation protocol. © 2012 IEEE.

关键词： Mean square error

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A timestamp model for determining real-time communications in intelligent networks

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computer COMMUNICATIONS 1997年第4期20卷 211-218页

作者： Patel, A OConnell, S Computer Networks and Distributed Systems Research Group Department of Computer Science University College Dublin Dublin 4 Ireland

The provision of services such as credit card facilities using Intelligent networks (IN) depends upon the ability to process real-time data. If their data is deliberately delayed during transit, these services may not be able to function accurately. This paper examines INs and highlights their vulnerability to network delay attacks. In particular, the nature of rear-time communications and the main approach that has been developed to determine whether received data is being sent in real-time or not is discussed. The deficiencies in this approach in terms of its ability to counteract the different forms of a network delay attack are highlighted and an alternative method which addresses these drawbacks is presented. Finally, the results achieved following the implementation and subsequent testing of the alternative approach are discussed. (C) 1997 Elsevier Science B.V.

关键词： real-time communications IN network delay attack clock synchronisation

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SECURITY MANAGEMENT FOR OSI networks

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computer COMMUNICATIONS 1994年第7期17卷 544-553页

作者： PATEL, A Computer Networks and Distributed Systems Research Group Department of Computer Science University College Dublin Belfield Dublin 4 Ireland

Security management is one of the key functional areas in open systems network management. Two key aspects of security management are managing user security services and providing security to network management systems. These are examined in tum to give the reader an overview of the state-of-the-art in security management. The ISO OSI Reference Model is used as a basis to present the security threats, security services and mechanisms which have to be managed. Telecommunications management networks are used as an example of management applications which both provide management and require the provision of security and security management services. The OSI approach to network management is examined in detail. This is followed by a survey of the categories of OSI security management activities, and a discussion of the security management needs of various common security services. The need for security for network management systems is examined.

关键词： SECURITY MANAGEMENT NETWORK MANAGEMENT OPEN systems ODP OSI TMN

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Performance analysis of an HDLC-based protocol with data compression

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computer COMMUNICATIONS 1997年第7期20卷 567-575页

作者： Ruplitsch, M Patel, A Computer Networks and Distributed Systems Research Group Department of Computer Science University College Dublin Belfield Dublin 4 Ireland

Several international standards for asynchronous data compression are available today. In 1993 the International Telecommunication Union (ITU) started to research possible ways to compress synchronous data. Special attention was given to compatibility with previous asynchronous standards, namely V.42bis. In September 1993 a proposal for modification of the V.42bis standard to make ii applicable to synchronous data was published. In this paper a prototype of a synchronous data link layer protocol based on the ITU proposals is described. The protocol chosen is HDLC based. The V.42bis compression standard is adapted to serve the needs of a synchronous protocol. A functional model is designed followed by a performance analysis of the protocol. The analysis shows a decrease of the compression ratio due to the adaption of the compression algorithm. (C) 1997 Elsevier Science B.V.

关键词： data compression HDLC data link LAP error correction

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An Efficient Multi-band Infrared Small Objects Detection Approach for Low-Altitude Artificial Intelligence of Thing

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IEEE Internet of Things Journal 2025年

作者： Peng, Yuhuai Wang, Jing Wang, Wenqian Liu, Lei Atiquzzaman, Mohammed Guizani, Mohsen Dustdar, Schahram Northeastern University School of Computer Science and Engineering Shenyang110819 China Zhiyuan Research Institute Hangzhou310024 China Northeastern University School of Computer Science and Engineering Shenyang110819 China Xidian University State Key Laboratory of Integrated Service Networks Xi'an710071 China University of Oklahoma School of Computer Science NormanOK73019 United States Mohamed Bin Zayed University of Artificial Intelligence Department of Machine Learning Masdar United Arab Emirates Technische Universität Wien Distributed Systems Group Vienna1040 Austria

As a cutting-edge technology of low-altitude Artificial Intelligence of Thing (AIoT), UAV object detection significantly enhances the surveillance services capabilities of low-altitude AIoT. However, the difficulty of object detection is exacerbated by the high proportion of small and obscure objects in the captured images. To address the mentioned challenges, we present an efficient multi-band infrared small object detection approach for low-altitude intelligent surveillance services. Firstly, we propose the Multi-band infrared Image Fusion algorithm based on Cascade-GAN (MIF-CGAN), which produces fused images with high information entropy and high contrast. Then, the Transformer-based Multi-scale Dense Small Object Detection (MsDSOD) algorithm is proposed. The algorithm consists of the Global-Local Object Detection (G-LOD) network, the Object Dense Area Extraction (O-DAE) module, and the Weighted Boxes Fusion (WBF) module. It extracts small objects features at different scales from infrared images and fuses the global and local detection results to accurately identify small objects in dense scenes. Furthermore, compared to the traditional algorithms, the mean Average Precision (mAP) of MsDSOD is improved by 0.80% and the Average Precision in small object detection (APs) is improved by 0.72%. The proposed algorithm is optimally suited to deal with complex scenes with dense small objects and background occlusion. © 2014 IEEE.

关键词： Infrared imaging

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Requirements and the concept of cooperative system management

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International Journal of Network Management 1998年第3期8卷 139-158页

作者： Bhushan, Bharat Patel, Ahmed Computer Networks and Distributed Systems Research Group Department of Computer Science University College Dublin Belfield Dublin 4 Ireland.

Cooperation among various types of management functions is necessary to allow management functions to interwork in providing and using information services for systems management. To understand these tasks from the point of view of cooperative working, this article discusses the requirements and presents the concept of cooperative system management.

关键词： Management information systems

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STARS-Enabled Full-Duplex Two-Way mMIMO System Under Spatially-Correlated Channels

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IEEE Transactions on Vehicular Technology 2025年

作者： Papazafeiropoulos, Anastasios Kourtessis, Pandelis Chatzinotas, Symeon Kaklamani, Dimitra I. Venieris, Iakovos S. University of Hertfordshire Communications and Intelligent Systems Research Group HatfieldAL10 9AB United Kingdom University of Luxembourg SnT Luxembourg Microwave and Fiber Optics Laboratory Greece National Technical University of Athens Intelligent Communications and Broadband Networks Laboratory School of Electrical and Computer Engineering Athens Zografou15780 Greece

Low-cost reconfigurable intelligent surfaces (RISs) are being considered as promising physical-layer technology for next-generation wireless networks due to their ability to re-engineer the propagation environment by tuning their elements. Although RIS-aided systems have many advantages, one of their major bottlenecks is that they can provide coverage only in front of the surface. Fortunately, simultaneous transmitting and reflecting surface (STARS)-assisted systems have emerged to fill this gap by providing 360° wireless coverage. In parallel, full-duplex (FD) communication offers a higher achievable rate through efficient spectrum utilization compared to the half-duplex (HD) counterpart. Moreover, two-way/bi-directional communications in an FD system can further enhance the system's spectral efficiency. Hence, in this paper, we propose a STARS-enabled massive MIMO deployment in an FD two-way communication network for highly efficient spectrum utilization, while covering the dead zones around the STARS. This model enables simultaneous information exchange between multiple nodes, while potentially doubling the spectral efficiency (SE). By invoking the use-and-then-forget (UaTF) combining scheme, we derive a closed-form expression for an achievable SE at each user of the system considering both uplink and downlink communications based on statistical channel state information (CSI), while also accounting for imperfect CSI and correlated fading conditions. Moreover, we formulate an optimization problem to obtain an optimal passive beamforming matrix design at the STARS that maximizes the sum achievable SE. The considered problem is non-convex and we propose a provably-convergent low-complexity algorithm, termed as projected gradient ascent method (ProGrAM), to obtain a stationary solution. Extensive numerical results are provided to establish the performance superiority of the FD STARS-enabled system over the HD STARS-enabled and FD conventional RIS (cRIS)-enabled coun

关键词： Digital television

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An External Broker Interface Based on Existing Trading Protocols

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Electronic Commerce research 2002年第4期2卷 337-358页

作者： Patel, Ahmed Blinov, Mikhail Computer Networks and Distributed Systems Research Group Department of Computer Science University College Dublin Belfield Dublin 4 Ireland

This paper presents an approach to the specification of external interfaces of an electronic broker used in the Architecture for Electronic Brokerage systems (AEBS). The external interface specified by the AEBS architecture provides both rich functionality and backward compatibility with trading methods that are currently in use in the electronic marketplace. This is achieved by defining the interface at two levels: the external protocol interface and the external object interface. The external protocol interface has been defined in terms of traditional protocols in order to provide access to basic brokerage services for customers and suppliers that already operate in the electronic market. This facilitates the easy introduction of a broker to the market since no modifications are required on the customer or supplier side to use the new brokerage services. The advanced external object interface has been designed and defined using the CORBA model. This provides other actors that need advanced brokerage services with access to the full functionality of a broker. This paper focuses on the design of the external protocol interface of a brokerage system. © 2002, Kluwer Academic Publishers.

关键词： Electronic commerce

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Channel Estimation for Stacked Intelligent Metasurfaces in Rician Fading Channels

arXiv

引用

arXiv 2025年

作者： Papazafeiropoulos, Anastasios Kourtessis, Pandelis Kaklamani, Dimitra I. Venieris, Iakovos S. Communications and Intelligent Systems Research Group University of Hertfordshire HatfieldAL10 9AB United Kingdom Microwave and Fiber Optics Laboratory Greece Intelligent Communications and Broadband Networks Laboratory School of Electrical and Computer Engineering National Technical University of Athens Zografou Athens15780 Greece

关键词： Mean square error

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