55 research outputs found
Dual-Polarized Massive MIMO-RSMA Networks: Tackling Imperfect SIC
The polarization domain provides an extra degree of freedom (DoF) for
improving the performance of multiple-input multiple-output (MIMO) systems.
This paper takes advantage of this additional DoF to alleviate practical issues
of successive interference cancellation (SIC) in rate-splitting multiple access
(RSMA) schemes. Specifically, we propose three dual-polarized downlink
transmission approaches for a massive MIMO-RSMA network under the effects of
polarization interference and residual errors of imperfect SIC. The first
approach implements polarization multiplexing for transmitting the users' data
messages, which removes the need to execute SIC in the reception. The second
approach transmits replicas of users' messages in the two polarizations, which
enables users to exploit diversity through the polarization domain. The third
approach, in its turn, employs the original SIC-based RSMA technique per
polarization, and this allows the BS to transmit two independent superimposed
data streams simultaneously. An in-depth theoretical analysis is carried out,
in which we derive tight closed-form approximations for the outage
probabilities of the three proposed approaches. Accurate approximations for the
ergodic sum-rates of the two first schemes are also derived. Simulation results
validate the theoretical analysis and confirm the effectiveness of the proposed
schemes. For instance, under low to moderate cross-polar interference, the
results show that, even under high levels of residual SIC error, our
dual-polarized MIMO-RSMA strategies outperform the conventional
single-polarized MIMO-RSMA counterpart. It is also shown that the performance
of all RSMA schemes is impressively higher than that of single and
dual-polarized massive MIMO systems employing non-orthogonal multiple access
(NOMA) and orthogonal multiple access (OMA) techniques
RSMA for Dual-Polarized Massive MIMO Networks: A SIC-Free Approach
Aiming at overcoming practical issues of successive interference cancellation
(SIC), this paper proposes a dual-polarized rate-splitting multiple access
(RSMA) technique for a downlink massive multiple-input multiple-output (MIMO)
network. By modeling the effects of polarization interference, an in-depth
theoretical analysis is carried out, in which we derive tight closed-form
approximations for the outage probabilities and ergodic sum-rates. Simulation
results validate the accuracy of the theoretical analysis and confirm the
effectiveness of the proposed approach. For instance, under low to moderate
cross-polar interference, our results show that the proposed dual-polarized
MIMO-RSMA strategy outperforms the single-polarized MIMO-RSMA counterpart for
all considered levels of residual SIC error.Comment: arXiv admin note: substantial text overlap with arXiv:2211.0085
Structure and stability of finite gold nanowires
Finite gold nanowires containing less than 1000 atoms are studied using the
molecular dynamics simulation method and embedded atom potential. Nanowires
with the face-centered cubic structure and the (111) oriented cross-section are
prepared at T=0 K. After annealing and quenching the structure and vibrational
properties of nanowires are studied at room temperature. Several of these
nanowires form multi-walled structures of lasting stability. They consist of
concentrical cylindrical sheets and resemble multi-walled carbon nanotubes.
Vibrations are investigated by diagonalization of the dynamical matrix. It was
found that several percents of vibrational modes are unstable because of
uncompleted restructuring of initial fcc nanowires.Comment: 4 figures in gif forma
Diferentes composições de substratos e ambientes protegidos na formação de mudas de pé-franco de tamarindeiro
"Delirium Day": A nationwide point prevalence study of delirium in older hospitalized patients using an easy standardized diagnostic tool
Background: To date, delirium prevalence in adult acute hospital populations has been estimated generally from pooled findings of single-center studies and/or among specific patient populations. Furthermore, the number of participants in these studies has not exceeded a few hundred. To overcome these limitations, we have determined, in a multicenter study, the prevalence of delirium over a single day among a large population of patients admitted to acute and rehabilitation hospital wards in Italy. Methods: This is a point prevalence study (called "Delirium Day") including 1867 older patients (aged 65 years or more) across 108 acute and 12 rehabilitation wards in Italian hospitals. Delirium was assessed on the same day in all patients using the 4AT, a validated and briefly administered tool which does not require training. We also collected data regarding motoric subtypes of delirium, functional and nutritional status, dementia, comorbidity, medications, feeding tubes, peripheral venous and urinary catheters, and physical restraints. Results: The mean sample age was 82.0 \ub1 7.5 years (58 % female). Overall, 429 patients (22.9 %) had delirium. Hypoactive was the commonest subtype (132/344 patients, 38.5 %), followed by mixed, hyperactive, and nonmotoric delirium. The prevalence was highest in Neurology (28.5 %) and Geriatrics (24.7 %), lowest in Rehabilitation (14.0 %), and intermediate in Orthopedic (20.6 %) and Internal Medicine wards (21.4 %). In a multivariable logistic regression, age (odds ratio [OR] 1.03, 95 % confidence interval [CI] 1.01-1.05), Activities of Daily Living dependence (OR 1.19, 95 % CI 1.12-1.27), dementia (OR 3.25, 95 % CI 2.41-4.38), malnutrition (OR 2.01, 95 % CI 1.29-3.14), and use of antipsychotics (OR 2.03, 95 % CI 1.45-2.82), feeding tubes (OR 2.51, 95 % CI 1.11-5.66), peripheral venous catheters (OR 1.41, 95 % CI 1.06-1.87), urinary catheters (OR 1.73, 95 % CI 1.30-2.29), and physical restraints (OR 1.84, 95 % CI 1.40-2.40) were associated with delirium. Admission to Neurology wards was also associated with delirium (OR 2.00, 95 % CI 1.29-3.14), while admission to other settings was not. Conclusions: Delirium occurred in more than one out of five patients in acute and rehabilitation hospital wards. Prevalence was highest in Neurology and lowest in Rehabilitation divisions. The "Delirium Day" project might become a useful method to assess delirium across hospital settings and a benchmarking platform for future surveys
Understanding Factors Associated With Psychomotor Subtypes of Delirium in Older Inpatients With Dementia
Understanding UAV-Based WPCN-Aided Capabilities for Offshore Monitoring Applications
Despite the immense progress in the recent years, efficient solutions for
monitoring remote areas are still missing today. This is especially notable in
the context of versatile maritime and offshore use cases, owing to a broader
span of operating regions and a lack of radio network infrastructures. In this
article, we address the noted challenge by delivering a conceptual solution
based on the convergence of three emerging technologies -- unmanned aerial
vehicles (UAVs), battery-less sensors, and wireless powered communication
networks (WPCNs). Our contribution offers a systematic description of the
ecosystem related to the proposed solution by identifying its key actors and
design dimensions together with the relevant resources and performance metrics.
A system-level modeling-based evaluation of an illustrative scenario delivers
deeper insights into the considered operation and the associated trade-offs.
Further, unresolved challenges and perspective directions are underpinned for a
subsequent study
Rate-Splitting Multiple Access and its Interplay with Intelligent Reflecting Surfaces
Rate-splitting multiple access (RSMA) has recently appeared as a powerful
technique for improving the downlink performance of multiple-input
multiple-output (MIMO) systems. By flexibly managing interference, RSMA can
deliver high spectral and energy efficiency, as well as robustness to imperfect
channel state information (CSI). In another development, an intelligent
reflecting surface (IRS) has emerged as a method to control the wireless
environment through software-configurable, near-passive, sub-wavelength
reflecting elements. This article presents the potential of synergy between IRS
and RSMA. Three important improvements achievable by IRS-RSMA schemes are
identified, supported by insightful numerical examples, and mapped to beyond-5G
use cases, along with future research directions.Comment: IEEE Communications Magazine, May 202
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