Context-Aware Handover Policies in HetNets

Next generation cellular systems are expected to entail a wide variety of wireless coverage zones, with cells of different sizes and capacities that can overlap in space and share the transmission resources. In this scenario, which is referred to as Heterogeneous Networks (HetNets), a fundamental challenge is the management of the handover process between macro, femto and pico cells. To limit the number of handovers and the signaling between the cells, it will hence be crucial to manage the user's mobility considering the context parameters, such as cells size, traffic loads, and user velocity. In this paper, we propose a theoretical model to characterize the performance of a mobile user in a HetNet scenario as a function of the user's mobility, the power profile of the neighboring cells, the handover parameters, and the traffic load of the different cells. We propose a Markov-based framework to model the handover process for the mobile user, and derive an optimal context-dependent handover criterion. The mathematical model is validated by means of simulations, comparing the performance of our strategy with conventional handover optimization techniques in different scenarios. Finally, we show the impact of the handover regulation on the users performance and how it is possible to improve the users capacity exploiting context information

A Bayesian multi-factor model of instability in prices and quantities of risk in U.S. financial markets

This paper analyzes the empirical performance of two alternative ways in which multi-factor models with time-varying risk exposures and premia may be estimated. The first method echoes the seminal two-pass approach advocated by Fama and MacBeth (1973). The second approach extends previous work by Ouysse and Kohn (2010) and is based on a Bayesian approach to modelling the latent process followed by risk exposures and idiosynchratic volatility. Our application to monthly, 1979-2008 U.S. data for stock, bond, and publicly traded real estate returns shows that the classical, two-stage approach that relies on a nonparametric, rolling window modelling of time-varying betas yields results that are unreasonable. There is evidence that all the portfolios of stocks, bonds, and REITs have been grossly over-priced. On the contrary, the Bayesian approach yields sensible results as most portfolios do not appear to have been misspriced and a few risk premia are precisely estimated with a plausibile sign. Real consumption growth risk turns out to be the only factor that is persistently priced throughout the sample.Econometric models ; Stochastic analysis ; Financial markets

Efficient Spectrum Management as an Enabler Towards 5G Cellular Systems

Advanced spectrum sharing and resource management techniques are needed in future wireless cellular networks to ensure high data rates to the end users. New system architec- tures will be required, taking into account aspects such as like spectrum resources availabil- ity, deployment and operational costs, as well as power consumption. Thus, it becomes key for the development of the fifth generation of cellular networks (5G) to pursue an efficient exploitation of the wireless medium, in the sense of both using advanced physical (PHY) layer techniques, and also seeking coordination among operators. In this thesis, we analyze the problem of spectrum management within the next generation of cellular networks and we propose new algorithms for spectrum sharing and for interference coordination. In the first part of the thesis, we focus on the spectrum sharing between operators. Firstly, we develop a Long Term Evolution (LTE) standard compliant simulation environ- ment extending the open-source network simulator ns3 to support multi-input multi-output (MIMO) systems and advanced beamforming systems. Then, we present a mathematical analysis for the network performance of non-orthogonal spectrum sharing, connecting it directly with the statistics of the radio channel and we develop some spectrum sharing al- gorithms considering different aspects of the operators coexistence. The analysis is further extended to the performance evaluation of more complex digital beamforming techniques developed in a multi-input-single-output (MISO) system allowing to reach a Pareto equi- librium between the operators. Finally, we consider also an orthogonal spectrum sharing scenario investigating the impact of asymmetries and dynamics of the user demands on the implementation of spectrum sharing techniques. In the second part of the thesis, we extend the concept of spectrum management to two different scenarios. In the first scenario, we consider coordination between multiple cells, e.g. coordinated multipoint (CoMP). In particular, thanks to the exploitation of digital beamforming techniques, we present a novel distributed clustering algorithm that adapts the cluster configuration according to the users distribution and the average cluster size. In the second scenario, we extend the concept of spectrum sharing to the coexistence between different communications system in order to study the feasibility of the deployment of the cellular systems within the mmWave spectrum. In particular, we analyze the impact of the novel cellular networks on the fixed satellite system (FSS). In the last part of the thesis, we focus on the mobility management of the users in a het- erogeneous network. Firstly, we focus on the average performance experienced by a mobile user while crossing a pico/femtocell, as a function of the handover parameters to provide an approximate expression of the average Shannon capacity experienced by a mobile user when crossing the femtocell. Then, we propose a Markov-based framework to model the user state during the handover process and, based on such a model, we derive an optimal context-dependent handover criterion

A study on the coexistence of fixed satellite service and cellular networks in a mmWave scenario

The use of a larger bandwith in the millimeter wave (mmWave) spectrum is one of the key components of next generation cellular networks. Currently, part of this band is allocated on a co-primary basis to a number of other applications,such as the fixed satellite services (FSSs). In this paper, we investigate the coexistence between a cellular network and FSSs in a mmWave scenario. In light of the parameters recommended by the standard and the recent results presented in the literature on the mmWave channel model, we analyze different BSs deployments and different antenna configurations at the transmitters. Finally, we show how, exploiting the features of a mmWave scenario, the coexistence between cellular and satellite services is feasible and the interference at the FSS antenna can be kept below recommended levels

A cooperative scheduling algorithm for the coexistence of fixed satellite services and 5G cellular network

The increasing demand for higher data rates has accelerated research on the next generation of mobile cellular networks (5G). One of the key factors of 5G is the use of a larger bandwidth allocated in the millimeter wave (mmWave)frequency spectrum. In particular, one of the candidate bands is the portion of spectrum between 17 and 30 GHz that is currently used by other technologies such as fixed satellite services (FSS) and the cellular network backhaul. In this paper, we analyze the coexistence between mobile services and FSS considering the main characteristics of the mmWave spectrum recently investigated in the literature. Moreover, we present a novel cooperative scheduling algorithm based on a game theoretic framework that exploits the use of analog beamforming at the base stations (BS). Finally, we show that adopting this algorithm ensure that the system meets the regulatory recommendation concerning the interference level at the FSS and at the same time provides a good user spectral efficiency

Targeting eosinophils: severe asthma and beyond

Recent research in the field of bronchial asthma has mainly focused on eosinophilic disease phenotype. Several trials proved the efficacy and safety profile of eosinophils and interleukin (IL)-5 targeting molecules, currently approved for severe asthma and available on the market. They include mepolizumab and reslizumab, IL-5 blocking molecules, and benralizumab, targeting the IL-5 receptor and eliciting a NK cell-mediated antibody-dependent cellular cytotoxicity against eosinophils. Eosinophilic inflammation represents the common pathophysiological background of several conditions, providing the rationale for the use of the same biologics beyond asthma. Although with different evidence grade, from clinical trials to case reports, anti-IL-5 biologics have been investigated in eosinophilic granulomatosis with polyangitis, allergic bronchopulmonary aspergillosis, chronic eosinophilic pneumonia, nasal polyposis, hypereosinophilic syndrome, and eosinophilic esophagitis. However, non-negligible differences between asthma and other eosinophilic diseases, particularly in eosinophils homing (blood and/or tissues), target organs and thus clinical features, probably account for the different response to the same drug in different clinical conditions and highlights the need for tailoring the therapeutic approach by modulating the drug dose and/or by combination therapy with multiple drugs. The optimal safety and tolerability profile of anti-IL-5 drugs warrants further and larger experimental and real-life investigations, which are needed especially in the field of non-asthma eosinophilic diseases. This review aims at summarizing the rationale for the use of biologics in eosinophilic diseases and their mechanisms of action. The current efficacy and safety evidence about eosinophils and IL-5 targeting molecules in asthma and in eosinophilic conditions beyond bronchi is also discussed

Warfarin, but not rivaroxaban, promotes the calcification of the aortic valve in ApoE-/- mice.

SummaryIntroductionVitamin K antagonists, such as warfarin, are known to promote arterial calcification through blockade of gamma‐carboxylation of Matrix‐Gla‐Protein. It is currently unknown whether other oral anticoagulants such as direct inhibitors of Factor Xa can have protective effects on the progression of aortic valve calcification.AimsTo compare the effect of warfarin and rivaroxaban on the progression of aortic valve calcification in atherosclerotic mice.Results42 ApoE−/− mice fed with Western‐type Diet (WTD) were randomized to treatment with warfarin (n = 14), rivaroxaban (n = 14) or control (n = 14) for 8 weeks. Histological analyses were performed to quantify the calcification of aortic valve leaflets and the development of atherosclerosis. The analyses showed a significant increase in valve calcification in mice treated with warfarin as compared to WTD alone (P = .025) or rivaroxaban (P = .005), whereas no significant differences were found between rivaroxaban and WTD (P = .35). Quantification of atherosclerosis and intimal calcification was performed on the innominate artery of the mice and no differences were found between the 3 treatments as far as atherogenesis and calcium deposition is concerned. In vitro experiments performed using bovine interstitial valve cells (VIC) showed that treatment with rivaroxaban did not prevent the osteogenic conversion of the cells but reduce the over‐expression of COX‐2 induced by inflammatory mediators.ConclusionWe showed that warfarin, but not rivaroxaban, could induce calcific valve degeneration in a mouse model of atherosclerosis. Both the treatments did not significantly affect the progression of atherosclerosis. Overall, these data suggest a safer profile of rivaroxaban on the risk of cardiovascular disease progression

En Face Optical Coherence Tomography to Detect and Measure Geographic Atrophy

Citation: Pilotto E, Guidolin F, Convento E, et al. En face optical coherence tomography to detect and measure geographic atrophy. Invest Ophthalmol Vis Sci. 2015;56:8120-8124. DOI:10.1167/iovs.15-17366 PURPOSE. To detect and quantify geographic atrophy (GA) secondary to age-related macular degeneration using en face optical coherence tomography (OCT) and to correlate it to GA measured with fundus autofluorescence (FAF). METHODS. Twenty-four consecutive patients (27 eyes) were studied with both standard (STD)-and enhanced depth imaging (EDI)-OCT. En face OCT images were obtained at the outer retinal layer (OR) and at the choroidal layer (CH) level for both STD-and EDI-OCT. Areas of GA were measured on the en face OCT images and were correlated with the GA areas measured on blue (B)-and near infrared (NIR)-wavelength FAF images. CONCLUSIONS. En face OCT is a reliable method to detect and quantify GA, particularly when analyzed at the OR level, where the photoreceptors' loss creates an abrupt transition in OCT reflectivity. RESULTS. The intraoperator agreement i

Modeling tick-by-tick realized correlations

A tree-structured heterogeneous autoregressive (tree-HAR) process is proposed as a simple and parsimonious model for the estimation and prediction of tick-by-tick realized correlations. The model can account for different time and other relevant predictors’ dependent regime shifts in the conditional mean dynamics of the realized correlation series. Testing the model on S&P 500 Futures and 30-year Treasury Bond Futures realized correlations, empirical evidence that the tree-HAR model reaches a good compromise between simplicity and flexibility is provided. The model yields accurate single- and multi-step out-of-sample forecasts. Such forecasts are also better than those obtained from other standard approaches, in particular when the final goal is multi-period forecasting