End-to-End Simulation of 5G mmWave Networks

Due to its potential for multi-gigabit and low latency wireless links, millimeter wave (mmWave) technology is expected to play a central role in 5th generation cellular systems. While there has been considerable progress in understanding the mmWave physical layer, innovations will be required at all layers of the protocol stack, in both the access and the core network. Discrete-event network simulation is essential for end-to-end, cross-layer research and development. This paper provides a tutorial on a recently developed full-stack mmWave module integrated into the widely used open-source ns--3 simulator. The module includes a number of detailed statistical channel models as well as the ability to incorporate real measurements or ray-tracing data. The Physical (PHY) and Medium Access Control (MAC) layers are modular and highly customizable, making it easy to integrate algorithms or compare Orthogonal Frequency Division Multiplexing (OFDM) numerologies, for example. The module is interfaced with the core network of the ns--3 Long Term Evolution (LTE) module for full-stack simulations of end-to-end connectivity, and advanced architectural features, such as dual-connectivity, are also available. To facilitate the understanding of the module, and verify its correct functioning, we provide several examples that show the performance of the custom mmWave stack as well as custom congestion control algorithms designed specifically for efficient utilization of the mmWave channel.Comment: 25 pages, 16 figures, submitted to IEEE Communications Surveys and Tutorials (revised Jan. 2018

Information-Centric Design and Implementation for Underwater Acoustic Networks

Over the past decade, Underwater Acoustic Networks (UANs) have received extensive attention due to their vast benefits in academia and industry alike. However, due to the overall magnitude and harsh characteristics of underwater environments, standard wireless network techniques will fail because current technology and energy restrictions limit underwater devices due to delayed acoustic communications. To help manage these limitations we utilize Information-Centric Networking (ICN). More importantly, we look at ICN\u27s paradigm shift from traditional TCP/IP architecture to improve data handling and enhance network efficiency. By utilizing some of ICN\u27s techniques, such as data naming hierarchy, we can reevaluate each component of the network\u27s protocol stack given current underwater limitations to study the vast solutions and perspectives Information-Centric architectures can provide to UANs. First, we propose a routing strategy used to manage and route large data files in a network prone to high mobility. Therefore, due to UANs limited transmitting capability, we passively store sensed data and adaptively find the best path. Furthermore, we introduce adapted Named Data Networking (NDN) components to improve upon routing robustness and adaptiveness. Beyond naming data, we use tracers to assist in tracking stored data locations without using other excess means such as flooding. By collaborating tracer consistency with routing path awareness our protocol can adaptively manage faulty or high mobility nodes. Through this incorporation of varied NDN techniques, we are able to see notable improvements in routing efficiency. Second, we analyze the effects of Denial of Service (DoS) attacks on upper layer protocols. Since UANs are typically resource restrained, malicious users can advantageously create fake traffic to burden the already constrained network. While ICN techniques only provide basic DoS restriction we must expand our detection and restriction technique to meet the unique demands of UANs. To provide enhanced security against DoS we construct an algorithm to detect and restrict against these types of attacks while adapting to meet acoustic characteristics. To better extend this work we incorporate three node behavior techniques using probabilistic, adaptive, and predictive approaches for detecting malicious traits. Thirdly, to depict and test protocols in UANs, simulators are commonly used due to their accessibility and controlled testing aspects. For this section, we review Aqua-Sim, a discrete event-driven open-source underwater simulator. To enhance the core aspect of this simulator we first rewrite the current architecture and transition Aqua-Sim to the newest core simulator, NS-3. Following this, we clean up redundant features spread out between the various underwater layers. Additionally, we fully integrate the diverse NS-3 API within our simulator. By revamping previous code layout we are able to improve architecture modularity and child class expandability. New features are also introduced including localization and synchronization support, busy terminal problem support, multi-channel support, transmission range uncertainty modules, external noise generators, channel trace-driven support, security module, and an adapted NDN module. Additionally, we provide extended documentation to assist in user development. Simulation testing shows improved memory management and continuous validity in comparison to other underwater simulators and past iterations of Aqua-Sim

Diminishing commodity prices and capital flight in a dutch disease and resource curse environment: The case of Bolivia

Diminishing commodity prices and increasing world interest rates are the two main expected outcomes from slowdown of emerging economies and growth recovery of advanced economies in the post financial crisis. A CGE model is used to analyze commodity shocks in a natural resource country framework with two export oriented resource sectors (gas & oil and minerals) and mainly two emerging tradable sectors (food and manufacturing) with dominant import substitution orientation. Positive shocks of unusual magnitude in the pre-crisis generate strong Dutch disease (DD) effects but also unusual levels of government income, savings and investment, giving rise to a growth opportunity. A negative shock to the mineral sector in the post-crisis does not reverse the growth opportunity as long as the gas & oil sector remains strong. However, policy would be required to help absorb the labor released and in the long-run structural reforms are needed to significantly diminish built-in DD effects in this sector. If in addition a significant negative shock hits the gas & oil sector, the economy can experience negative growth. Having a stabilization fund would help in this scenario, but to avoid it altogether sector policy is more important. Additionally, a DSGE model with tradable/non-tradable sectors and skilled/unskilled savers/not savers workers is calibrated to analyze the conditions under which capital flight might occur under increasing world interest rates in the post-crisis. These conditions require a significant degree of macroeconomic deterioration which is not being observed, but point to some key variables to follow, such as the level of net external assets held by the country

Diminishing commodity prices and capital flight in a dutch disease and resource curse environment: The case of Bolivia

Diminishing commodity prices and increasing world interest rates are the two main expected outcomes from slowdown of emerging economies and growth recovery of advanced economies in the post financial crisis. A CGE model is used to analyze commodity shocks in a natural resource country framework with two export oriented resource sectors (gas & oil and minerals) and mainly two emerging tradable sectors (food and manufacturing) with dominant import substitution orientation. Positive shocks of unusual magnitude in the pre-crisis generate strong Dutch disease (DD) effects but also unusual levels of government income, savings and investment, giving rise to a growth opportunity. A negative shock to the mineral sector in the post-crisis does not reverse the growth opportunity as long as the gas & oil sector remains strong. However, policy would be required to help absorb the labor released and in the long-run structural reforms are needed to significantly diminish built-in DD effects in this sector. If in addition a significant negative shock hits the gas & oil sector, the economy can experience negative growth. Having a stabilization fund would help in this scenario, but to avoid it altogether sector policy is more important. Additionally, a DSGE model with tradable/non-tradable sectors and skilled/unskilled savers/not savers workers is calibrated to analyze the conditions under which capital flight might occur under increasing world interest rates in the post-crisis. These conditions require a significant degree of macroeconomic deterioration which is not being observed, but point to some key variables to follow, such as the level of net external assets held by the country

Essays on real business cycle modelling under adaptive learning

The thesis consists on three chapters aiming to contribute to a growing literature on adaptive learning, a form of bounded rationality that has been attracting increasing interest both in the theoretical and practical fields, as an alternative to the commonly used rational expectations hypothesis on how expectations are formed among economic agents. The first chapter investigates whether it is possible to improve the ability of the standard real business cycle model to match the main stylised facts of emerging economies, taking the case of Mexico as an illustration, by assuming that agents are not fully rational and instead form expectations according to an adaptive learning rule. Two well-known rules - recursive least squares and its constant gain variant - are considered for this purpose. The degree of difficulty of the learning process is characterised by different starting values of the algorithms as well as different constant gains. The simulations show that the model under learning generally outperforms its rational expectations counterpart. Therefore, policymakers should take into account the fact that the expected welfare gains/losses of a particular policy reform, conceived assuming a fully-rational environment, might be significantly different if, in practice, agents behave as learners. Using a heterogeneous-agent model with three types of agents, namely capitalists, skilled workers and unskilled workers - assuming constant population shares suggesting low social mobility -, and allowing for different degrees of complementarity among these within the productive structure, the second chapter welfare-evaluates tax reforms consistent with a lower long run debt-to-output ratio for the United Kingdom, both under rational expectations and heterogenous learning. This chapter shows that, relative to the other tax reforms, capital tax cuts lead to the highest aggregate welfare but are skill-biased and can thus increase inequality in the long run. That is, depending on the elasticity of substitution between capital and unskilled labour, falls in the capital tax can result in higher levels of welfare inequality, even in the absence of other frictions and increases in other forms of taxation. On the other hand, reductions in labour taxes can hurt the capitalists. This chapter shows too that including the transition period in the welfare evaluation lowers the inequality effects of capital tax reductions since the complementarity between capital and all labour inputs is higher in the short- than in the long-run. Finally, while heterogeneous learning in the shape of differing initial beliefs after the reform can lead to a form of "irrational exuberance" after a tax cut, it can also exacerbate welfare inequality. Finally, the third chapter presents an heterogeneous-agent model with two types of agents, capitalists and workers - with constant population shares given the strong evidence on low social mobility -, calibrated to Bolivia´s data in order to examine the short and long-run effectiveness and distributional effects of various fiscal rules designed to impose restrictions on the evolution of public debt as a share of output, in response to two different sources of exogenous volatility (i.e. productivity and commodity shocks) and under different ways of forming expectations, namely rational expectations and heterogenous learning. The results show that under full rationality the fiscal rules generate a trade-off between debt-stabilisation and higher income inequality while, under some conditions, heterogenous learning can help to break such trade-off so that some of the rules can perform well in both fields. However, given the significantly high levels of income inequality and dependence on commodity revenues experienced by Bolivia, finding the best performing rule in response to all the relevant exogenous shocks this economy might face, appears to be a challenging task

Land Use and Water Quality

This collection of 11 papers introduces broad topics covering various professional disciplines related to the research arena of land use and water quality. The papers exemplify the important links between agriculture and water quality in surface and ground waters as well as the pollution problems around urban areas. Advancement of new technologies for analyzing links between land use and water quality problems as well as insights into new tools for analyzing large monitoring datasets are highlighted in this collection of papers

Recreation, tourism and nature in a changing world : proceedings of the fifth international conference on monitoring and management of visitor flows in recreational and protected areas : Wageningen, the Netherlands, May 30-June 3, 2010

Proceedings of the fifth international conference on monitoring and management of visitor flows in recreational and protected areas : Wageningen, the Netherlands, May 30-June 3, 201

B!SON: A Tool for Open Access Journal Recommendation

Finding a suitable open access journal to publish scientific work is a complex task: Researchers have to navigate a constantly growing number of journals, institutional agreements with publishers, funders’ conditions and the risk of Predatory Publishers. To help with these challenges, we introduce a web-based journal recommendation system called B!SON. It is developed based on a systematic requirements analysis, built on open data, gives publisher-independent recommendations and works across domains. It suggests open access journals based on title, abstract and references provided by the user. The recommendation quality has been evaluated using a large test set of 10,000 articles. Development by two German scientific libraries ensures the longevity of the project