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

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

Antimicrobial and cytotoxic activities of short carbon chain unsaturated sucrose esters

A library of C3–C5 unsaturated 6-O-sucrose esters have been investigated for their antibacterial, antifungal, and cytotoxic activities. Most of the target compounds showed good inhibitory activity against a variety of clinically and food contaminant important microbial pathogens. In particular, 6-O-methacryloyl sucrose 2 and 1′,2,3,3′,4,4′,6′-hepta-O-acetyl-6-O-methacryloyl sucrose 9 were the most active bactericides against all the tested bacteria with minimal inhibitory concentrations (MICs) ranging between 0.24 and 1.40 μM. The compound 9 showed also the highest antifungal activity with MICs from 0.28 to 1.10 μM. The synthesized compounds possessed low cytotoxicity against human breast, lung, cervical, and hepatocellular carcinoma cell lines without showing toxicity for non-tumor liver cells. Thus, this library of short carbon chain unsaturated sucrose esters represent promising leads for the development of new generation of sucrose-based antimicrobial agents.This work has been supported by Fundação para a Ciência e a Tecnologia through grant nos. PEst-C/EQB/ LA0006/2013 and PEst-OE/AGR/UI0690/2014. The authors thank Serbian Ministry of Education, Science, and Technological Development for financial support (grant number 173032).info:eu-repo/semantics/publishedVersio

Synthesis, characterization, antimicrobial and antitumor activities of sucrose Octa(N-ethyl)carbamate

Sucrose octa(N-ethyl)carbamate was synthesized directly from sucrose and ethyl isocyanate, and its structure was confirmed by various analytical methods, such as 1H and 13C NMR, FTIR, m.p., MS, and optical rotation. Its antibacterial, antifungal and cytotoxic activities were investigated. It exhibited strong inhibition against all bacteria tested, namely S. aureus (MIC 0.18±0.006), B. cereus (MIC 0.094±0.000), M. flavus (MIC 0.28±0.01), L. monocytogenes (MIC 0.18±0.006), P. aeruginosa (MIC 0.094±0.002), S. typhimurium (MIC 0.094±0.002), E. coli (MIC 0.18±0.006) and E. cloacae (MIC 0.18±0.006) and strong antifungal activity towards T. viride (MIC 0.09 ± 0.006), A. versicolor (MIC 0.18 ± 0.01), A. ochraceus (MIC 0.375 ± 0.01) and P. ochrochloron (MIC 0.375 ± 0.04). Furthermore, it showed moderate antitumor potential against human breast (GI50357.20±14.12), colon (GI50 332.43±11.19) and cervical (GI50 282.67±3.97) cell lines and, more important, without hepatotoxicity.This work has been supported by Fundação para a Ciência e a Tecnologia through grants No. PEst- C/EQB/LA0006/2013 and PEst-OE/AGR/UI0690/2011. The authors thank to Serbian Ministry of Education and Science for financial support (grant No. 173032). The NMR spectrometers are part of The National NMR Facility, supported by Fundação para a Ciência e a Tecnologia (RECI/BBBBQB/ 0230/2012).info:eu-repo/semantics/publishedVersio

FINITE-ELEMENT MODELLING OF THE TYMPANIC MEMBRANE RETRACTION POCKET UNDER NEGATIVE PRESSURE IN THE TYMPANIC CAVITY

The finite-element calculation of the static stress-strain state of the middle ear was made in this paper. The malleus, incus and stapes models were constructed on the basis of tomographic data. The tympanic membrane model was obtained using the equations of elliptic hyperboloids. The tympanic membrane consists of the pars tensa and pars flaccida, which have different thicknesses and elasticity moduli. Absolute deformations of the tympanic membrane were defined at different values of negative pressure in the tympanic cavity. The critical values of elastic modulus for the pars tensa posterosuperior quadrant were found for the point at which the tympanic membrane touches the auditory ossicles. Obtained results can be used to predict the thickness of a cartilaginous graft which is overlaid on the posterosuperior quadrant of the pars tensa in order to eliminate the retraction pocket

FINITE-ELEMENT MODELLING OF THE TYMPANIC MEMBRANE RETRACTION POCKET UNDER NEGATIVE PRESSURE IN THE TYMPANIC CAVITY

The finite-element calculation of the static stress-strain state of the middle ear was made in this paper. The malleus, incus and stapes models were constructed on the basis of tomographic data. The tympanic membrane model was obtained using the equations of elliptic hyperboloids. The tympanic membrane consists of the pars tensa and pars flaccida, which have different thicknesses and elasticity moduli. Absolute deformations of the tympanic membrane were defined at different values of negative pressure in the tympanic cavity. The critical values of elastic modulus for the pars tensa posterosuperior quadrant were found for the point at which the tympanic membrane touches the auditory ossicles. Obtained results can be used to predict the thickness of a cartilaginous graft which is overlaid on the posterosuperior quadrant of the pars tensa in order to eliminate the retraction pocket

Antimicrobial and cytotoxic activities of 1,2,3-triazole-sucrose derivatives

A library of 1-(1′,2,3,3′,4,4′,6-hepta-O-acetyl-6′-deoxy-sucros-6′-yl)-1,2,3-triazoles have been investigated for their antibacterial, antifungal and cytotoxic activities. Most of the target compounds showed good inhibitory activity against a variety of clinically and food contaminant important microbial pathogens. In particular, 1-(1′,2,3,3′,4,4′,6-hepta-O-acetyl-6′-deoxy-sucros-6′-yl)-4-(4-pentylphenyl)-1,2,3- triazole (5) was highly active against all the tested bacteria with minimal inhibitory concentrations (MICs) ranging between 1.1 and 4.4 μM and bactericidal concentrations (MBCs) from 2.2 and 8.4 μM. The compound 1-(1′,2,3,3′,4,4′,6-hepta-O-acetyl-6′-deoxy-sucros-6′-yl)-4-(4-bromophenyl)-1,2,3-triazole (3) showed antifungal activity with MICs from 0.6 to 4.8 μM and minimal fungicidal concentrations (MFCs) ranging between 1.2 and 8.9 μM. Furthermore, some of the compounds possessed moderate cytotoxicity against human breast, lung, cervical and hepatocellular carcinoma cell lines, without showing toxicity for nontumor liver cells. The above mentioned derivatives represent promising leads for the development of new generation of sugar-triazole anti fungal agents.This work has been supported by Fundação para a Ciência e a Tecnologia through grant Nos. PEst-C/EQB/LA0006/2013 and PEst-OE/AGR/UI0690/2014. T.M. Potewar and R.C. Calhelha are grateful to Fundação para a Ciência e a Tecnologia for their pos-doctoral Grant Nos. SFRH/ BPD/65173/2009 and SFRH/BPD/68344/2010, respectively. The authors thank to Serbian Ministry of Education, Science and Technological Development for financial support (grant number 173032). The NMR spectrometers are part of The National NMR Facility, supported by Fundação para a Ciência e a Tecnologia (RECI/BBB-BQB/0230/2012)