424 research outputs found
Joint Beamforming and Reflection Design for RIS-assisted ISAC Systems
No full textIn this paper, we investigate the potential of employing reconfigurable
intelligent surface (RIS) in integrated sensing and communication (ISAC)
systems. In particular, we consider an RIS-assisted ISAC system in which a
multi-antenna base station (BS) simultaneously performs multi-user multi-input
single-output (MU-MISO) communication and target detection. We aim to jointly
design the transmit beamforming and receive filter of the BS, and the
reflection coefficients of the RIS to maximize the sum-rate of the
communication users, while satisfying a worst-case radar output signal-to-noise
ratio (SNR), the transmit power constraint, and the unit modulus property of
the reflecting coefficients. An efficient iterative algorithm based on
fractional programming (FP), majorization-minimization (MM), and alternative
direction method of multipliers (ADMM) is developed to solve the complicated
non-convex problem. Simulation results verify the advantage of the proposed
RIS-assisted ISAC scheme and the effectiveness of the developed algorithm.Comment: accepted by EUSIPCO2022, 5 pages, 3 figure
Interlayer stress absorbing composite (ISAC) for mitigating reflection cracking in asphalt concrete overlays
No full text"This study deals with the design of a composite material which could effectively alleviate/mitigate the problem of reflection cracking in an AC overlay. After reviewing various case histories and having identified the problem areas in the treatments currently in use, a composite material consisting of two geotextile layers containing a thin viscoelastic rubber asphalt layer named, ""Interlayer Stress Absorbing Composite (ISAC)"" was proposed."To approach the design problem of the ISAC system effectively properties of the materials intended to be used in the system were first identified. Various models and laboratory testing procedures were used for this purpose. A Climate-Materials-Structural (CMS) pavement model was used to establish the pavement temperature range in Northern Illinois. A number of geotextiles were selected and tested for their engineering properties. Several samples of rubber asphalt were prepared by blending various ratios of crumb rubber with different types and ratios of asphalt cements. These materials were tested at different temperatures and the effects of temperature and rate of deformation on stiffness were investigated."After having selected the materials suitable for the ISAC system, based on their properties, a prototype ISAC system was fabricated in the laboratory and was then checked against slippage under an overlay with a vehicle making a sharp turn or applying sudden brakes. The computer program ""CIRCLY"" was used for this purpose. Testing equipment was developed to evaluate the interfacial shear strength and laboratory testing was performed to determine the shear strength of the fabricated ISAC layer under an AC overlay. Required stiffens was achieved in the ISAC core material by adding hydrated lime in the rubber asphalt."After completion of the component property testing program, the ISAC layer was fabricated and prepared for laboratory evaluation. A testing device was developed in the laboratory that simulated field conditions to evaluate an AC overlay over a cracked PCC slab with and without an ISAC system. The performance of the ISAC system was evaluated by comparing crack growth in the overlay of a control pavement section with that in an overlay over the ISAC treated PCC slab.Made available in DSpace on 2011-05-07T12:29:42Z (GMT). No. of bitstreams: 2
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MIMO-OFDM ISAC Waveform Design for Range-Doppler Sidelobe Suppression
No full textIntegrated sensing and communication (ISAC) is a key enabling technique for future wireless networks owing to its efficient hardware and spectrum utilization. In this paper, we focus on dual-functional waveform design for a multi-input multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) ISAC system, which is considered to be a promising solution for practical deployment. Since the dual-functional waveform carries communication information, its random nature leads to high range-Doppler sidelobes in the ambiguity function, which in turn degrades radar sensing performance. To suppress range-Doppler sidelobes, we propose a novel symbol-level precoding (SLP) based waveform design for MIMO-OFDM ISAC systems by fully exploiting the temporal degrees of freedom (DoFs). Our goal is to minimize the range-Doppler integrated sidelobe level (ISL) while satisfying the constraints of target illumination power, multi-user communication quality of service (QoS), and constant-modulus transmission. To solve the resulting non-convex waveform design problem, we develop an efficient algorithm using the majorization-minimization (MM) and alternative direction method of multipliers (ADMM) methods. Simulation results show that the proposed waveform has significantly reduced range-Doppler sidelobes compared with signals designed only for communications and other baselines. In addition, the proposed waveform design achieves target detection and estimation performance close to that achievable by waveforms designed only for radar, which demonstrates the superiority of the proposed SLP-based ISAC approach.13 pages, 9 figures, submitted to IEEE TW
iSac: Intimacy based Access Control for Social Network Sites
No full textParticipation in social networking sites has dramatically increased in recent years. Users on social networking sites spend lots of time generating large quantities of various personal content items (eg. diaries, albums, and comments) and browsing these varieties of content everyday. However, existing social networking sites do not provide effective access control mechanisms to assure the privacy of user-generated content. A user's personal content on social networking sites may be exposed to other users without any access control. This paper presents iSac, a novel intimacy-based social access control mechanism on social networking sites. iSac allows a user to make his access control policy on social networking sites according to intimacy degrees of him with respect to other users. iSac will first outline a user's activity profile according to his atomic social activities with respect to his seed friends. Then we adopt Naive-Bayes algorithm to calculate the intimacy degrees and rankings of all the user's friends. A content owner can make his access control policy by assigning a range of intimacy degrees. Users whose intimacy degrees are in the acceptable range can visit the content owner's personal content. Our experiments which use data collected from RenRen in China prove that iSac can effectively differentiate a user's friends by intimacy degrees so as to provide a novel access control mechanism with an improved granularity.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000310381500076&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Computer Science, Theory & MethodsEngineering, Electrical & ElectronicEICPCI-S(ISTP)
Performance Analysis and Power Allocation for Massive MIMO ISAC Systems
No full textAbstract
Integrated sensing and communications (ISAC) is envisioned as a key feature in future wireless communications networks. Its integration with massive multiple-input-multiple-output (MIMO) techniques promises to leverage substantial spatial beamforming gains for both functionalities. In this work, we consider a massive MIMO-ISAC system employing a uniform planar array with zero-forcing and maximum-ratio downlink transmission schemes combined with monostatic radar-type sensing. Our focus lies on deriving closed form expressions for the achievable communications rate and the Cramér–Rao lower bound (CRLB), which serve as performance metrics for communications and sensing operations, respectively. The expressions enable us to investigate important operational characteristics of massive MIMO-ISAC, including the mutual effects of communications and sensing as well as the advantages stemming from using a very large antenna array for each functionality. Further-more, we devise a power allocation strategy based on successive convex approximation to maximize the communications rate while guaranteeing the CRLB constraints and transmit power budget. Extensive numerical results are presented to validate our theoretical analyses and demonstrate the efficiency of the proposed power allocation approach.Abstract
Integrated sensing and communications (ISAC) is envisioned as a key feature in future wireless communications networks. Its integration with massive multiple-input-multiple-output (MIMO) techniques promises to leverage substantial spatial beamforming gains for both functionalities. In this work, we consider a massive MIMO-ISAC system employing a uniform planar array with zero-forcing and maximum-ratio downlink transmission schemes combined with monostatic radar-type sensing. Our focus lies on deriving closed form expressions for the achievable communications rate and the Cramér–Rao lower bound (CRLB), which serve as performance metrics for communications and sensing operations, respectively. The expressions enable us to investigate important operational characteristics of massive MIMO-ISAC, including the mutual effects of communications and sensing as well as the advantages stemming from using a very large antenna array for each functionality. Further-more, we devise a power allocation strategy based on successive convex approximation to maximize the communications rate while guaranteeing the CRLB constraints and transmit power budget. Extensive numerical results are presented to validate our theoretical analyses and demonstrate the efficiency of the proposed power allocation approach
A decision theory approach to standing order procurement of NASA reports
No full textExplains various package deal procurement methods including standing order method for library documents. Enumerates different standing order services of NTIS for technical reports. Describes the NASA information system. Discusses and analyses the economy of NASA FS service by applying decision theory approach and considering the various costs as well as saving aspects/advantages. Explains the non-economic factors to be considered in evaluating such a service. Suggests ways of making NASA FS service more beneficial to the library of ISRO Satellite Centre (ISAC)
A Novel Joint Angle-Range-Velocity Estimation Method for MIMO-OFDM ISAC Systems
No full textIntegrated sensing and communication (ISAC) is emerging as a key technique for next-generation wireless systems. In order to expedite the practical implementation of ISAC in pervasive mobile networks, it is crucial to have widely deployed base stations with radar sensing capabilities. Thus, the utilization of standardized multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) hardware architectures and waveforms is pivotal for realizing seamless integration of effective communication and sensing functionalities. In this paper, we introduce a novel joint angle-range-velocity estimation algorithm for MIMO-OFDM ISAC systems. This approach exclusively depends on the format of conventional MIMO-OFDM waveforms that are widely adopted in wireless communications. Specifically, the angle-range-velocity information of potential targets is jointly extracted by utilizing all the received echo signals within a coherent processing interval (CPI). The proposed joint estimation algorithm can achieve larger signal-to-noise-ratio (SNR) processing gains and higher resolution by fully exploiting the echo signals and jointly estimating the angle-range-velocity information. A theoretical analysis for maximum unambiguous range, resolution, and SNR processing gains is provided to verify the advantages of the proposed joint estimation algorithm. Finally, the results of extensive numerical experiments are presented to demonstrate that the proposed joint estimation approach can achieve significantly lower root-mean-square-error (RMSE) performance for angle/range/velocity estimation for both single- and multi-target scenarios.13 pages, 8 figures, submitted to IEEE Tran
RSMA-Assisted Cell-Free Massive MIMO Multi-Static ISAC System With Correlated Aging Channels
No full textInternational audienceA rate splitting multiple access (RSMA) assisted cellfree massive multiple-input multiple-output (CF-mMIMO) integrated sensing and communication (ISAC) system is investigated in this paper. The considered system model comprises several distributed transmitting access points (APs) communicating with multiple mobile vehicles (MVs) and simultaneously probing a target whose reflections are sensed by receiving APs. Using spectral efficiency (SE) as the communication metric and transmit beampattern gain and sensing SE as the sensing performance metrics, we analyze the impact of channel aging and pilot contamination over spatially correlated channels on the proposed ISAC system. We derive closed-form SE expressions that consider practical impairments including imperfect channel state information (CSI) and compare with their spatial domain multiple access (SDMA) counterpart. An analytical framework is developed through trade-off analysis to assess the system's integrated dual functionalities. Based on the trade-off analysis conducted, we formulate a joint optimization problem to maximize the communication sum SE and the sensing SE constrained on the pilot length, power allocation for the sensing and communication functionalities, and power splitting between common and private streams. The non-convex problem is optimized by adopting a nested iterative algorithm which separates the problem into three subproblems. Through simulation results, we validate our analysis and provide insights into the effects of key system parameters, including AP transmit power, Doppler shift, number of APs and resource block length on the overall system performance. Simulation results confirm the effectiveness of the RSMA CF-mMIMO system for ISAC functionalities
Allergic phenotypes in patients with respiratory allergy evaluated by microchip ISAC technique
No full textUniverzita Karlova Farmaceutická fakulta v Hradci Králové Katedra biologických a lékařských věd Autor: Bc. Petra Porubová Vedoucí práce: prof. RNDr. Ctirad Andrýs, Ph.D. Název diplomové práce: Senzibilizační profil u pacientů s respiračními formami alergického zánětu hodnocený pomocí multiplexové metody ISAC Klíčová slova: alergický zánět, specifické IgE protilátky, molekulární alergeny, multiplexová metoda, ISAC Cíl: Cílem práce bylo zhodnocení senzibilizačního profilu u pacientů s alergickou rhinitidou a/nebo s astmatem bronchiale a zjištění možných rozdílů mezi pacienty s různou závažností onemocnění. Metody: Pro stanovení specifických IgE protilátek proti 112 alergenním komponentám byla využita metoda ImmunoCAP ISAC. Hodnocený soubor zahrnoval 152 pacientů (57,9 % žen) z alergologické ambulance Ústavu klinické imunologie a alergologie Fakultní nemocnice Hradec Králové. Výsledky: Nejčastějšími alergeny v daném souboru pacientů s respiračními formami alergického zánětu byly komponenty Phl p 1 (68,4 %) a Bet v 1 (65,1 %). Rozdíly v počtu pozitivních a negativních reakcí byly prokázány mezi pacienty s různou závažností alergické rhinitidy. Byly nalezeny korelace mezi počty pozitivních/negativních reakcí a závažností astmatu bronchiale. Nejvyšší hladiny specifických IgE byly naměřeny u komponent...Charles University Faculty of Pharmacy in Hradec Králové Department of Biological and Medical Sciences Author: Bc. Petra Porubová Supervisor: prof. RNDr. Ctirad Andrýs, Ph.D. Title of diploma thesis: Allergic phenotypes in patients with respiratory allergy evaluated by microchip ISAC technique Key words: allergic inflammation, allergen specific IgE, component resolved diagnostics, microchip, ISAC Background: The aim of this diploma thesis was to evaluate the sensitization profile in the group of pacients with allergic rhinitis and/or bronhial asthma and to identify possible differences between patients with different disease severity. Methods: ImmunoCAP ISAC was used to determine specific IgE antibodies against 112 allergen components. The evaluated group included 152 patients (57.9 % women) from the allergology outpatient office of the Department of Clinical Immunology and Allergology, University Hospital Hradec Králové. Results: The most common allergens in this group of patients were the components Phl p 1 (68,4 %) and Bet v 1 (65,1 %). Differences in the number of positive and negative reactions were demonstrated between patients with different severity of allergic rhinitis. Correlations were found between the number of positive/negative reactions and the severity of bronchial asthma. And the...Department of Biological and Medical SciencesKatedra biologických a lékařských vědFaculty of Pharmacy in Hradec KrálovéFarmaceutická fakulta v Hradci Králov
First results with TIGRESS and accelerated radioactive ion beams from ISAC: Coulomb excitation of20,21,29Na
No full textThe TRIUMF‐ISAC Gamma‐Ray Escape Suppressed Spectrometer (TIGRESS) is a state‐of‐the‐art γ‐ray spectrometer being constructed at the ISAC‐II radioactive ion beam facility at TRIUMF. TIGRESS will be comprised of twelve 32‐fold segmented high‐purity germanium (HPGe) clover‐type γ‐ray detectors, with BGO∕CsI(Tl) Compton‐suppression shields, and is currently operational at ISAC‐II in an early‐implementation configuration of six detectors. Results have been obtained for the first experiments performed using TIGRESS, which examined the A = 20, 21, and 29 isotopes of Na by Coulomb excitation
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