101 research outputs found
Energy Efficient Massive MIMO Array Configurations
The high spectral efficiency of massive MIMO (Multiple Input Multiple Output)
is mainly achieved through the exploitation of spatial multiplexing, i.e. by
using a high number of MIMO layers that are applied simultaneously to many
users. The power consumption of a massive MIMO base station is determined by
the hardware driving a high number of antenna ports and elements. This paper
focuses on practical deployment situations with varying user load. During hours
with low number of users a certain significant part of hardware power
consumption would remain with conventional massive MIMO processing, while the
full potential of spectral efficiency cannot be exploited due to the low number
of users, resulting in low power efficiency and cost. We investigate the impact
of different hybrid array architectures on spectral efficiency, average user
throughput and power consumption and show how to design a massive MIMO system
with significantly improved energy efficiency for a given target scenario,
while maintaining a targeted service quality
Minimizing Energy Consumption in MU-MIMO via Antenna Muting by Neural Networks with Asymmetric Loss
Transmit antenna muting (TAM) in multiple-user multiple-input multiple-output
(MU-MIMO) networks allows reducing the power consumption of the base station
(BS) by properly utilizing only a subset of antennas in the BS. In this paper,
we consider the downlink transmission of an MU-MIMO network where TAM is
formulated to minimize the number of active antennas in the BS while
guaranteeing the per-user throughput requirements. To address the computational
complexity of the combinatorial optimization problem, we propose an algorithm
called neural antenna muting (NAM) with an asymmetric custom loss function. NAM
is a classification neural network trained in a supervised manner. The
classification error in this scheme leads to either sub-optimal energy
consumption or lower quality of service (QoS) for the communication link. We
control the classification error probability distribution by designing an
asymmetric loss function such that the erroneous classification outputs are
more likely to result in fulfilling the QoS requirements. Furthermore, we
present three heuristic algorithms and compare them with the NAM. Using a 3GPP
compliant system-level simulator, we show that NAM achieves energy
saving compared to the full antenna configuration in the BS with
reliability in achieving the user throughput requirements while being around
and less computationally intensive than the greedy
heuristic algorithm and the fixed column antenna muting algorithm,
respectively.Comment: Submitted to IEEE Transactions on Vehicular Technolog
CRAP: Clutter Removal with Acquisitions Under Phase Noise
The emergence of Integrated Sensing and Communication (ISAC) in future 6G
networks comes with a variety of challenges to be solved. One of those is
clutter removal, which should be applied to remove the influence of unwanted
components, scattered by the environment, in the acquired sensing signal. While
legacy radar systems already implement different clutter removal algorithms,
ISAC requires techniques that are tailored to the envisioned use cases and the
specific challenges that communications deployments bring along, like phase
noise due to clock errors between transmitter and receiver. To that end, in
this work we introduce Clutter Removal with Acquisitions Under Phase Noise
(CRAP). We propose to vectorize the time-frequency channel acquired in a radio
frame in a high-dimensional space. In an offline clutter acquisition step,
singular value decomposition is used to determine the major clutter components.
At runtime, the clutter is then estimated and removed by a subspace projection
of the acquired radio frame onto the clutter components.
Simulation results prove that CRAP offers benefits over prior art techniques
robust to phase noise. In particular, our proposal does not suppress zero
Doppler information, thereby enabling the detection of slow targets. Moreover,
we show CRAP's real-time applicability in a millimeter-wave ISAC proof of
concept, where a pedestrian is tracked in a cluttered lab environment.Comment: 8 pages, 6 figures. This work has been submitted to the IEEE for
possible publication. Copyright may be transferred without notice, after
which this version may no longer be accessibl
Multi-Target Localization in Multi-Static Integrated Sensing and Communication Deployments
In future wireless communication networks, existing active localization will
gradually evolve into more sophisticated (passive) sensing functionalities. One
main enabler for this process is the merging of information collected from the
network's nodes, sensing the environment in a multi-static deployment. The
current literature considers single sensing node systems and/or single target
scenarios, mainly focusing on specific issues pertaining to hardware
impairments or algorithmic challenges. In contrast, in this work we propose an
ensemble of techniques for processing the information gathered from multiple
sensing nodes, jointly observing an environment with multiple targets. A
scattering model is used within a flexibly configurable framework to highlight
the challenges and issues with algorithms used in this distributed sensing
task. We validate our approach by supporting it with detailed link budget
evaluations, considering practical millimeter-wave systems' capabilities. Our
numerical evaluations are performed in an indoor scenario, sweeping a variety
of parameter to analyze the KPIs sensitivity with respect to each of them. The
proposed algorithms to fuse information by multiple nodes show significant
gains in terms of targets' localization performance, with up to 35\% for the
probability of detection, compared to the baseline with a mono-static setup.Comment: 8 pages, 10 figures, 1 table. This work has been submitted to the
IEEE for possible publication. Copyright may be transferred without notice,
after which this version may no longer be accessibl
Effect of the Reversed L-Shaped Osteotomy on the Round Sign: Not All Hallux Valgus Deformities May Need Proximal Derotation to Correct the Radiographic Appearance of Metatarsal Pronation
Background
Metatarsal pronation has been claimed to be a risk factor for hallux valgus recurrence. A rounded shape of the lateral aspect of the first metatarsal head has been identified as a sign of persistent metatarsal pronation after hallux valgus correction. This study investigated the derotational effect of a reversed L-shaped (ReveL) osteotomy combined with a lateral release to correct metatarsal pronation. The primary hypothesis was that most cases showing a positive round sign are corrected by rebalancing the metatarsal-sesamoid complex. We further assumed that the inability to correct the round sign might be a risk factor for hallux valgus recurrence.
Methods
We retrospectively evaluated 266 cases treated with a ReveL osteotomy for hallux valgus deformity. The radiologic measurements were performed on weightbearing foot radiographs preoperatively, at an early follow-up (median, 6.2 weeks), and the most recent follow-up (median, 13 months). Univariate and multivariate logistic regression analyses identified risk factors for hallux valgus recurrence (hallux valgus angle [HVA] ≥ 20 degrees).
Results
A preoperative positive radiographic round sign was present in 40.2% of the cases, of which 58.9% turned negative after the ReveL osteotomy (P 30 degrees (odds ratio [OR] = 5.3, P 15 degrees (OR = 74.9; P < .001), and postoperative positive round sign (OR = 5.3, P = .008). Cases with a positive round sign at the most recent follow-up had a significantly higher recurrence rate than those with a negative round sign (22.7% vs 5.9%, P < .001).
Conclusion
The ReveL osteotomy corrected a positive round sign in 58.9%, suggesting that not all hallux valgus deformities may need proximal derotation to negate the radiographic appearance of the round sign. A positive round sign was found to be an independent risk factor for hallux valgus recurrence. Further 3-dimensional analyses are necessary to better understand the effects and limitations of distal translational osteotomies to correct metatarsal pronation.
Level of Evidence
Level IV, case series
A Neuroscientific Perspective
This review investigates how recent neuroimaging findings on vulnerability for
depression and the mechanisms of mindfulness may serve to inform and enhance
the understanding that is guiding the use of mindfulness training in the
prevention and treatment of recurrent and chronic depression. In particular,
we review evidence suggesting that alterations in default-mode-network
activity and connectivity represent a fundamental deficit underlying cognitive
vulnerability for depression and explore the ways in which mindfulness
meditation may reverse such alterations. Furthermore, we discuss findings from
studies that have investigated the effects of mindfulness on emotion-
regulatory capacities. These findings suggest mindful emotion regulation has a
characteristic neural signature that is particularly conducive to therapeutic
learning. We conclude that training in mindfulness has unique strengths for
addressing neural mechanisms associated with cognitive vulnerabilities for
recurrent and chronic depression and propose future lines of research to more
effectively harness this potential
Auswirkung differenzierter mechanischer Bodenbelastungen auf die Erträge von Erbse, Hafer und Erbse-Hafer-Gemenge
Die nachhaltige Erhaltung und Steigerung der Bodenfruchtbarkeit ist für ökologisch wirtschaftende Betriebe von höchster Bedeutung. Im Ökologischen Landbau hängt das Niveau der Bodenfruchtbarkeit – abgesehen von den kaum zu beeinflussenden standörtlichen Gegebenheiten – sehr von der Leistungsfähigkeit der Leguminosen ab. Vor allem durch ihre Fähigkeit, Luftstickstoff zu binden und diesen für ihr eigenes Wachstum sowie für die Folgekulturen verfügbar zu machen, bilden Leguminosen die Grundlage der Bodenfruchtbarkeit im Ökologischen Landbau. In der Konsequenz bedeutet dies, dass Beeinträchtigungen der Leistungsfähigkeit der Leguminosen nicht nur deren eigenen Ertrag sondern auch die Leistungsfähigkeit der gesamten Fruchtfolge am Standort begrenzen. Speziell für vieharme oder viehlose Öko-Betriebe könnte es gewinnbringend sein, großkörnige Leguminosen (Erbse, Ackerbohne) ergänzend zu Kleegras zur Erhaltung der Bodenfruchtbarkeit in die Fruchtfolge zu integrieren. Andererseits reagieren aber gerade Körnerleguminosen besonders empfindlich auf Beeinträchtigungen, sei es durch geringe Verfügbarkeit von Nährstoffen wie Phosphor und Kali, durch das Vorhandensein von boden- oder samenbürtigen Pathogenen oder durch Verdichtungen im Wurzelraum. Die Bodenbearbeitung im Öko-Anbau ist vergleichsweise intensiv, und das Risiko für Bodenverdichtungen daher hoch. Ziel ist es, Aussagen über den Einfluss von Bodenverdichtungen auf den Ertrag von Erbsen machen zu können. Zusätzlich soll geklärt werden, welchen Einfluss mechanische Bodenbeanspruchung auf die Bestandsentwicklung, das Auftreten von Wurzel- und Sprosskrankheiten und den Schädlingsbefall von Erbsen, Erbsen-Hafer-Gemenge und Hafer hat. Dazu wurden an vier Standorten in Deutschland im Rahmen eines von der Bundesanstalt für Landwirtschaft und Ernährung geförderten Verbundprojektes „Belastungsversuche“ angelegt
5GNOW: Challenging the LTE Design Paradigms of Orthogonality and Synchronicity
LTE and LTE-Advanced have been optimized to deliver high bandwidth pipes to
wireless users. The transport mechanisms have been tailored to maximize single
cell performance by enforcing strict synchronism and orthogonality within a
single cell and within a single contiguous frequency band. Various emerging
trends reveal major shortcomings of those design criteria: 1) The fraction of
machine-type-communications (MTC) is growing fast. Transmissions of this kind
are suffering from the bulky procedures necessary to ensure strict synchronism.
2) Collaborative schemes have been introduced to boost capacity and coverage
(CoMP), and wireless networks are becoming more and more heterogeneous
following the non-uniform distribution of users. Tremendous efforts must be
spent to collect the gains and to manage such systems under the premise of
strict synchronism and orthogonality. 3) The advent of the Digital Agenda and
the introduction of carrier aggregation are forcing the transmission systems to
deal with fragmented spectrum. 5GNOW is an European research project supported
by the European Commission within FP7 ICT Call 8. It will question the design
targets of LTE and LTE-Advanced having these shortcomings in mind and the
obedience to strict synchronism and orthogonality will be challenged. It will
develop new PHY and MAC layer concepts being better suited to meet the upcoming
needs with respect to service variety and heterogeneous transmission setups.
Wireless transmission networks following the outcomes of 5GNOW will be better
suited to meet the manifoldness of services, device classes and transmission
setups present in envisioned future scenarios like smart cities. The
integration of systems relying heavily on MTC into the communication network
will be eased. The per-user experience will be more uniform and satisfying. To
ensure this 5GNOW will contribute to upcoming 5G standardization.Comment: Submitted to Workshop on Mobile and Wireless Communication Systems
for 2020 and beyond (at IEEE VTC 2013, Spring
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