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 country’s 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 “behind the border” 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

CEECs integration into regional and global production networks

This paper examines the involvement of the CEECs into regional and global production networks over the period 1999 to 2009. We employ a theoretically justified gravity model which incorporates the extensive margin of trade and accounts for firm heterogeneity. We first estimate the model for highly disaggregated exports (SITC 5-digits) in final goods, and then augment it by including the corresponding imported intermediate products from the OECD together with the usual control variables. Next, we estimate the model for each trade margin (extensive and intensive) separately to evaluate the effects of economic integration on exports and imports of each category of goods. Our results indicate that the CEECs have indeed become more integrated into regional production networks and this has had a positive impact in terms of increasing trade volumes and trade varieties between the two parts of the European continent

CEECs Integration into Regional Production Networks. Trade Effects of EU-Accession

This paper examines the effect of the two most recent European Union enlargements on CEECs trade of intermediate and final products separately. A theoretically justified gravity model which incorporates the extensive margin of trade and accounts for firm heterogeneity is estimated using highly disaggregated trade data for the period 1999 to 2009. We hypothesize that the CEECs have a comparative advantage on the assembly of final goods and evaluate the effect of the EU-accession on CEECs imports in intermediates products and on CEECs export of final goods to OECD countries. To capture the importance of production networks, imported intermediate products from the OECD are added as a determinant of the corresponding exports of final goods. We find a positive and significant effect of accession on CEECs trade of intermediate and final goods. In particular, deeper integration and the consequent elimination of behind the border trade barriers have had a positive impact not only in terms of increasing trade volumes, but also in terms of increasing trade varieties between the two parts of the European continent

EU-Accession Effects on Sectoral Trade: A Helpman-Melitz-Rubinstein Approach with Panel Data

This paper estimates the effects of the EU enlargements in the 2000s for trade in parts and components and trade in final goods separately. A gravity model is applied to disaggregated trade data over the period 1999-2009 for trade between EU and OECD countries. The estimation approach accounts for firm heterogeneity and selection bias in a panel-data framework. We find a positive and significant effect of the EU-accession on CEECs trade in intermediate and final goods. The main findings indicate that the effect of EU accession is higher on trade in intermediate goods than on trade in final goods

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