251 research outputs found
Cell-free massive MIMO surveillance of multiple untrusted communication links
No full textA cell-free massive multiple-input multiple-output (CF-mMIMO) system is considered for enhancing the monitoring performance of wireless surveillance, where a large number of distributed multi-antenna aided legitimate monitoring nodes (MNs) proactively monitor multiple distributed untrusted com munication links. We consider two types of MNs whose task is to either observe the untrusted transmitters or jam the untrusted receivers. We first analyze the performance of CF mMIMO surveillance relying on both maximum ratio (MR) and partial zero-forcing (PZF) combining schemes and derive closed form expressions for the monitoring success probability (MSP) of the MNs. We then propose a joint optimization technique that designs the MN mode assignment, power control, and MN weighting coefficient control to enhance the MSP based on the long-term statistical channel state information knowledge. This challenging problem is effectively transformed into tractable forms and efficient algorithms are proposed for solving them. Numerical results show that our proposed CF-mMIMO surveil lance system considerably improves the monitoring performance with respect to a full-duplex co-located massive MIMO proactive monitoring system. More particularly, when the untrusted pairs are distributed over a wide area and use the MR combining, the proposed solution provides nearly a thirty-fold improvement in the minimum MSP over the co-located massive MIMO baseline, and forty-fold improvement, when the PZF combining is employed
Reconfigurable massive MIMO: harnessing the power of the electromagnetic domain for enhanced information transfer
No full textThe capacity of commercial massive multiple-input multiple-output (mMIMO) systems is constrained by the limited array aperture at the base station, and cannot meet the everincreasing traffic demands of wireless networks. Given the array aperture, holographic MIMO with infinitesimal antenna spacing can maximize the capacity, but is physically unrealizable. As a promising alternative, reconfigurable mMIMO is proposed to harness the unexploited power of the electromagnetic (EM) domain for enhanced information transfer. Specifically, the reconfigurable pixel antenna technology provides each antenna with an adjustable EM radiation (EMR) pattern, introducing extra degrees of freedom for information transfer in the EM domain. In this article, we present the concept and benefits of availing the EMR domain for mMIMO transmission. Moreover, we propose a viable architecture for reconfigurable mMIMO systems, and the associated system model and downlink precoding are also discussed. In particular, a three-level precoding scheme is proposed, and simulation results verify its considerable spectral and energy efficiency advantages compared to traditional mMIMO systems. Finally, we further discuss the challenges, insights, and prospects of deploying reconfigurable mMIMO, along with the associated hardware, algorithms, and fundamental theory
Web Application Design for Community Environmental Incident Reporting
No full textThis thesis focuses on the design and development of "EnvironEyes" a web-based application created to facilitate community-driven environmental incident reporting. Aimed at enhancing environmental awareness and improving community safety, the platform allows residents to report incidents efficiently using their internet-enabled devices. The application integrates features that support user-friendly navigation and real-time updates, fostering quick responses from local authorities. Through this initiative, the platform enhances proactive community engagement by making environmental reporting accessible to all, thus contributing to better environmental quality and safety. Analysis of user interactions and feedback highlights the platform's effectiveness in promoting environmental responsibility among residents. This research demonstrates the pivotal role of digital tools in community-based environmental management and provides a framework for future enhancements to increase user engagement and system functionality.Complete
Author Correction: RNAs coordinate nuclear envelope assembly and DNA replication through ELYS recruitment to chromatin
No full textIn the original version of this Article, the affiliation details for Antoine Aze, Michalis Fragkos, Stéphane Bocquet, Julien Cau and Marcel Méchali incorrectly omitted ‘CNRS and the University of Montpellier’. This has now been corrected in both the PDF and HTML versions of the Article.</jats:p
A child of the Academy? : investigating Euclid's philosophical background
No full textA prevalent idea among contemporary scholars is that Euclid belonged to, or was heavily influenced by the Platonic philosophical tradition. To a certain extent, this impression is not new; the quest for Euclid's philosophical background was probably triggered and enhanced by his late commentators, Greeks and Arabs, who appear confident that he had one. For instance, al-Qifti writes: 'Euclid...called the author of geometry, a philosopher of somewhat ancient date...' and al-Nadim in the Fihrist names Euclid as '...one of the mathematical philosophers...' Proclus, five centuries earlier than al-Nadim, was more specific: '[Euclid] was a follower of Plato by choice, and familiar with this philosophy'. In this paper, I propose to explore the extant accounts on Euclid's philosophical background. (Michalis Sialaros, University of London
Post - Independence Cypriot Dramaturgy (1960 Onwards)
Full text linkHow did playwriting evolve in Cyprus since independence (1960 and afterwards)? There is a systematic absence of studies on the subject. The author of this article analyzes the work of some of the most important playwrights of the period (Rina Katselli, Michalis Pitsillidis, Panos Ioannidis, Michalis Pasiardis and Yiorgos Neophytou) and describes their main carcteristics. Even though the writers of the 1960s continue to write in the naturalistic mode, others courageously follow more contemporary trends.How did playwriting evolve in Cyprus since independence (1960 and afterwards)? There is a systematic absence of studies on the subject. The author of this article analyzes the work of some of the most important playwrights of the period (Rina Katselli, Michalis Pitsillidis, Panos Ioannidis, Michalis Pasiardis and Yiorgos Neophytou) and describes their main carcteristics. Even though the writers of the 1960s continue to write in the naturalistic mode, others courageously follow more contemporary trends.Comment évolue l’écriture théâtrale pendant la période de l’indépendance (depuis 1960)? Il n’existe pas d’études systématiques sur ce sujet. Dans cet article sont analysées des œuvres de quelques auteurs dramatiques les plus représentatifs (Rina Katselli, Michalis Pitsillidis, Panos Ioannidis, Michalis Pasiardis et Yiorgos Neophytou) et sont résumées les lignes directrices de leur œuvre. Bien que les auteurs de la décennie 1960 continuent de créer en suivant la tradition du théâtre éthographique (théâtre de mœurs), on assiste à des efforts plus audacieux, qui tendent à une écriture théâtrale plus contemporaine
Optimal Per-Antenna ADC Bit Allocation in Correlated and Cell-Free Massive MIMO
No full textIn Massive MIMO base stations (BSs), the hardware design needs to balance high spectral efficiency (SE) with low complexity. The level of hardware impairments (HWIs) indicates how strong the signal distortion introduced by hardware imperfections is. In particular, the analog-to-digital converters (ADCs) have an important impact on signal distortion and power consumption. This article addresses the fundamental problem of selecting the optimal hardware quality in the Massive MIMO space. In particular, we examine the optimal HWI and ADC bit allocation per BS antenna to maximize the SE. The results show that in co-located arrays with low channel gain variations across antennas, equal ADC bit allocation is optimal. In contrast, cell-free Massive MIMO systems benefit the most from optimizing the ADC bit allocation achieving improvements in the order of 2 [bit-per-channel-use] per user equipment when using regularized zero-forcing (RZF). In addition, when including the impact of power consumption in cell-free Massive MIMO with RZF, allocating low values of mixed ADC bit resolutions across the BS antennas can increase the energy efficiency up to 30% compared to equal ADC bit allocation
Optimal Per-Antenna ADC Bit Allocation in Correlated and Cell-Free Massive MIMO
No full textIn Massive MIMO base stations (BSs), the hardware design needs to balance high spectral efficiency (SE) with low complexity. The level of hardware impairments (HWIs) indicates how strong the signal distortion introduced by hardware imperfections is. In particular, the analog-to-digital converters (ADCs) have an important impact on signal distortion and power consumption. This article addresses the fundamental problem of selecting the optimal hardware quality in the Massive MIMO space. In particular, we examine the optimal HWI and ADC bit allocation per BS antenna to maximize the SE. The results show that in co-located arrays with low channel gain variations across antennas, equal ADC bit allocation is optimal. In contrast, cell-free Massive MIMO systems benefit the most from optimizing the ADC bit allocation achieving improvements in the order of 2 [bit-per-channel-use] per user equipment when using regularized zero-forcing (RZF). In addition, when including the impact of power consumption in cell-free Massive MIMO with RZF, allocating low values of mixed ADC bit resolutions across the BS antennas can increase the energy efficiency up to 30% compared to equal ADC bit allocation
Inverse identification of buffeting and self-excited wind loads on the hardanger bridge from acceleration data
No full textThe traditional wind load assessment for long-span bridges rely on assumed models for the wind field and aerodynamic coefficients from wind tunnel tests, which usually introduces some uncertainties. It is therefore desired to develop tools that can utilize full-scale vibration response data from existing bridges in order to study the wind loading in detail for in-situ conditions. This paper presents a novel case study of inverse identification of dynamic wind loads on the 1310 m long Hardanger bridge, a suspension bridge equipped with a network of accelerometers. The identification method used is an extented Kalman-type filter for joint input, state, and parameter estimation. A system model considering the still-air modes in addition to a quasi-steady submodel for the self-excited forces of the bridge is presente. The coefficients for self-excited lift and pitching moment are considered unknown and are jointly estimated with the buffeting forces.Dynamics of StructuresOffshore Engineerin
Multi-pair two-way massive MIMO relaying with zero forcing: Energy efficiency and power scaling laws
Full text linkIn this paper, we study a multi-pair two-way half-duplex decode-and-forward (DF) massive multiple-input multiple-output (MIMO) relaying system, in which multiple single-antenna user pairs can exchange information through a massive MIMO relay. For low-complexity transmission, zeroforcing reception/zero-forcing transmission (ZFR/ZFT) is employed at the relay. First, we analytically study the large-scale approximations of the sum spectral efficiency (SE). Furthermore, we focus on three specific power scaling laws to study the trade off between the transmit powers of each pilot symbol, each user and the relay, and also focus on how the transmit powers scale with the number of relay antennas, M, to maintain a finite SE performance. Additionally, we consider a practical power consumption model to investigate the energy efficiency (EE), and illustrate the impact of M and the interplay between the power scaling laws and the EE performance. Finally, we consider the system fairness via maximizing the minimum achievable SE among all user pairs
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