531 research outputs found
Survey of Spectrum Sharing for Inter-Technology Coexistence
Increasing capacity demands in emerging wireless technologies are expected to
be met by network densification and spectrum bands open to multiple
technologies. These will, in turn, increase the level of interference and also
result in more complex inter-technology interactions, which will need to be
managed through spectrum sharing mechanisms. Consequently, novel spectrum
sharing mechanisms should be designed to allow spectrum access for multiple
technologies, while efficiently utilizing the spectrum resources overall.
Importantly, it is not trivial to design such efficient mechanisms, not only
due to technical aspects, but also due to regulatory and business model
constraints. In this survey we address spectrum sharing mechanisms for wireless
inter-technology coexistence by means of a technology circle that incorporates
in a unified, system-level view the technical and non-technical aspects. We
thus systematically explore the spectrum sharing design space consisting of
parameters at different layers. Using this framework, we present a literature
review on inter-technology coexistence with a focus on wireless technologies
with equal spectrum access rights, i.e. (i) primary/primary, (ii)
secondary/secondary, and (iii) technologies operating in a spectrum commons.
Moreover, we reflect on our literature review to identify possible spectrum
sharing design solutions and performance evaluation approaches useful for
future coexistence cases. Finally, we discuss spectrum sharing design
challenges and suggest future research directions
CEECS integration into regional production networks. Trade effects of EU-accesion
We estimate a gravity model that incorporates the extensive margin of trade and accounts for firm heterogeneity to evaluate the effect of the EU-accession on CEECs trade in intermediates and final goods for the period 1999-2009. The importance of production networks is captured by including imports of intermediates as a determinant of a countryâs exports of final goods. We find a positive and significant effect of the EU-accession on CEECs trade in intermediate and final goods. Hence, the elimination of âbehind the borderâ trade barriers has a positive impact on increasing not only trade volumes but also trade varieties.gravity equation; panel data; production networks; economic integration; trade flows.
Risk-Informed Interference Assessment for Shared Spectrum Bands: A Wi-Fi/LTE Coexistence Case Study
Interference evaluation is crucial when deciding whether and how wireless
technologies should operate. In this paper we demonstrate the benefit of
risk-informed interference assessment to aid spectrum regulators in making
decisions, and to readily convey engineering insight. Our contributions are: we
apply, for the first time, risk assessment to a problem of inter-technology
spectrum sharing, i.e. Wi-Fi/LTE in the 5 GHz unlicensed band, and we
demonstrate that this method comprehensively quantifies the interference
impact. We perform simulations with our newly publicly-available tool and we
consider throughput degradation and fairness metrics to assess the risk for
different network densities, numbers of channels, and deployment scenarios. Our
results show that no regulatory intervention is needed to ensure harmonious
technical Wi-Fi/LTE coexistence: for the typically large number of channels
available in the 5 GHz band, the risk for Wi-Fi from LTE is negligible,
rendering policy and engineering concerns largely moot. As an engineering
insight, Wi-Fi coexists better with itself in dense, but better with LTE, in
sparse deployments. Also, both main LTE-in-unlicensed variants coexist well
with Wi-Fi in general. For LTE intra-technology inter-operator coexistence,
both variants typically coexist well in the 5 GHz band, but for dense
deployments, implementing listen-before-talk causes less interference
LTE in Unlicensed Bands is neither Friend nor Foe to Wi-Fi
Proponents of deploying LTE in the 5 GHz band for providing additional
cellular network capacity have claimed that LTE would be a better neighbour to
Wi-Fi in the unlicensed band, than Wi-Fi is to itself. On the other side of the
debate, the Wi-Fi community has objected that LTE would be highly detrimental
to Wi-Fi network performance. However, there is a lack of transparent and
systematic engineering evidence supporting the contradicting claims of the two
camps, which is essential for ascertaining whether regulatory intervention is
in fact required to protect the Wi-Fi incumbent from the new LTE entrant. To
this end, we present a comprehensive coexistence study of Wi-Fi and
LTE-in-unlicensed, surveying a large parameter space of coexistence mechanisms
and a range of representative network densities and deployment scenarios. Our
results show that, typically, harmonious coexistence between Wi-Fi and LTE is
ensured by the large number of 5 GHz channels. For the worst-case scenario of
forced co-channel operation, LTE is sometimes a better neighbour to Wi-Fi -
when effective node density is low - but sometimes worse - when density is
high. We find that distributed interference coordination is only necessary to
prevent a "tragedy of the commons" in regimes where interference is very
likely. We also show that in practice it does not make a difference to the
incumbent what kind of coexistence mechanism is added to LTE-in-unlicensed, as
long as one is in place. We therefore conclude that LTE is neither friend nor
foe to Wi-Fi in the unlicensed bands in general. We submit that the systematic
engineering analysis exemplified by our case study is a best-practice approach
for supporting evidence-based rulemaking by the regulator.Comment: accepted for publication in IEEE Acces
REVIEW OF THE MAIN EQUIPMENT USED FOR SEPARATING CONTAMINANTS FROM WHEAT SEEDS, CLASSIFICATION ACCORDING TO THEIR FUNCTIONAL ROLE
Wheat seed cleaning require a complex set of operations to be performed in order to remove impurities from the grain mass and obtain high quality final products. These operations are carried out in a technological flow, starting from harvesting until the final processing stage, depending on the crop destination. The stages used to clean the wheat grain are usually following the operations: cleaning in aerodynamic separators, cleaning with sieves, sorting in indent cylinder separator, additional cleaning in special cleaning machines. The paper presents a synthesis of the primary processing phases of wheat seeds for the use in the food industry depending on their functional role
ASPECTS REGARDING BIOMASS FROM ENERGEIC PLANTS (ENERGETIC WILLOW â SALIX MINIMALIS) GRINDING PROCESS FOR PELLETIZATION
         Using energetic plants like energetic willow in the process of developing renewable energy processes, is under heavy research and development by scientists. Energetic crops are subjected to a technological process mainly for easy maneuverability purposes. An important processing phase is energetic plant grinding. The present paper describes researches regarding the grinding process of ha hammer mill using energetic willow as feeding material. 4 types of hammers and 5 grinding speeds were used. Starting from this data the necessary energy consumption for a 5 mm sieve was calculated
ASPECTS REGARDING BIOMASS FROM ENERGEIC PLANTS (ENERGETIC WILLOW â SALIX MINIMALIS) GRINDING PROCESS FOR PELLETIZATION
         Using energetic plants like energetic willow in the process of developing renewable energy processes, is under heavy research and development by scientists. Energetic crops are subjected to a technological process mainly for easy maneuverability purposes. An important processing phase is energetic plant grinding. The present paper describes researches regarding the grinding process of ha hammer mill using energetic willow as feeding material. 4 types of hammers and 5 grinding speeds were used. Starting from this data the necessary energy consumption for a 5 mm sieve was calculated
UV DISINFECTION - A METHOD OF PURIFYING WASTEWATER FROM FARMS â A REVIEW
The livestock industry increased significantly globally due to increasing demand for animal products. There are however, growing concerns on the environmental risks, associated with the disposal of untreated livestock wastewater into streams and rivers. Disinfection is considered to be the primary mechanism for the inactivation/ destruction of pathogenic organisms to prevent the spread of waterbornediseases to downstream users and the environment.Water disinfection using ultraviolet light is a newer process that currently has a limited use area [5].The purpose of this paper is to present the ultraviolet disinfection process used for the treatment of waste water
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