The Role of Licence-Exemption in Spectrum Reform

Spectrum reform initiatives in the US and Europe have identified a need to move away from the traditional command and control approach towards flexible and tradable licences and licence-exemption. Current regulatory initiatives are tending to focus on the flexible licensing route, and there is a risk that licence-exemption will be sidelined during the important formative years of this major policy transition. This must not happen; licence-exemption supports innovation and entrepreneurship and is an important second leg of a market-based spectrum management regime. A current case in point is the transition in UHF frequency bands from analogue to digital TV, where licence exempt use of resulting gaps in the spectrum could yield enormous benefits for citizens and consumers.spectrum policy, spectrum management, wireless services, deregulation, Telecommunications, regulation, Networks

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

The Role of Licence-Exemption in Spectrum Reform

Spectrum reform initiatives in the US and Europe have identified a need to move away from the traditional command and control approach towards flexible and tradable licences and licence-exemption. Current regulatory initiatives are tending to focus on the flexible licensing route, and there is a risk that licence-exemption will be sidelined during the important formative years of this major policy transition. This must not happen; licence-exemption supports innovation and entrepreneurship and is an important second leg of a market-based spectrum management regime. A current case in point is the transition in UHF frequency bands from analogue to digital TV, where licence exempt use of resulting gaps in the spectrum could yield enormous benefits for citizens and consumers

The Role of Licence-Exemption in Spectrum Reform

Spectrum reform initiatives in the US and Europe have identified a need to move away from the traditional command and control approach towards flexible and tradable licences and licence-exemption. Current regulatory initiatives are tending to focus on the flexible licensing route, and there is a risk that licence-exemption will be sidelined during the important formative years of this major policy transition. This must not happen; licence-exemption supports innovation and entrepreneurship and is an important second leg of a market-based spectrum management regime. A current case in point is the transition in UHF frequency bands from analogue to digital TV, where licence exempt use of resulting gaps in the spectrum could yield enormous benefits for citizens and consumers

Совершенствование транспортных комплексов гранитных карьеров

Проведен анализ основных технологических схем транспортирования горной массы в условиях гранитных карьеров Украины. Предложены новые технологические схемы карьерного транспорта с использованием канатных напочвенных дорог.Проведен анализ основных технологических схем транспортирования горной массы в условиях гранитных карьеров Украины. Предложены новые технологические схемы карьерного транспорта с использованием канатных напочвенных дорог

Accretion and outflow of gas in Markarian 509

A major uncertainty in models for photoionised outflows in AGN is the distance of the gas to the central black hole. We present the results of a massive multiwavelength monitoring campaign on the bright Seyfert 1 galaxy Mrk 509 to constrain the location of the outflow components dominating the soft X-ray band. Mrk 509 was monitored by XMM-Newton, Integral, Chandra, HST/COS and Swift in 2009. We have studied the response of the photoionised gas to the changes in the ionising flux produced by the central regions. We were able to put tight constraints on the variability of the absorbers from day to year time scales. This allowed us to develop a model for the time-dependent photoionisation in this source. We find that the more highly ionised gas producing most X-ray line opacity is at least 5 pc away from the core; upper limits to the distance of various absorbing components range between 20 pc up to a few kpc. The more lowly ionised gas producing most UV line opacity is at least 100 pc away from the nucleus. These results point to an origin of the dominant, slow (v<1000 km/s) outflow components in the NLR or torus-region of Mrk 509. We find that while the kinetic luminosity of the outflow is small, the mass carried away is likely larger than the 0.5 Solar mass per year accreting onto the black hole. We also determined the chemical composition of the outflow as well as valuable constraints on the different emission regions. We find for instance that the resolved component of the Fe-K line originates from a region 40-1000 gravitational radii from the black hole, and that the soft excess is produced by Comptonisation in a warm (0.2-1 keV), optically thick (tau~10-20) corona near the inner part of the disk.Comment: 4 pages, 1 figure, Proceedings of IAUS 290 "Feeding Compact Objects: Accretion on All Scales", C. M. Zhang, T. Belloni, M. Mendez & S. N. Zhang (eds.

Optical modes in oxide-apertured micropillar cavities

We present a detailed experimental characterization of the spectral and spatial structure of the confined optical modes for oxide-apertured micropillar cavities, showing good-quality Hermite-Gaussian profiles, easily mode-matched to external fields. We further derive a relation between the frequency splitting of the transverse modes and the expected Purcell factor. Finally, we describe a technique to retrieve the profile of the confining refractive index distribution from the spatial profiles of the modes.Comment: 4 pages, 3 figure