Asymptotically Exact Approximations for the Symmetric Difference of Generalized Marcum-Q Functions

(c) 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works. DOI: 10.1109/TVT.2014.2337263In this paper, we derive two simple and asymptotically exact approximations for the function defined as ΔQm(a, b) =Δ Qm(a, b) - Qm(b, a). The generalized Marcum Q-function Qm(a, b) appears in many scenarios in communications in this particular form and is referred to as the symmetric difference of generalized Marcum Q-functions or the difference of generalized Marcum Q-functions with reversed arguments. We show that the symmetric difference of Marcum Q-functions can be expressed in terms of a single Gaussian Q-function for large and even moderate values of the arguments a and b. A second approximation for ΔQm(a, b) is also given in terms of the exponential function. We illustrate the applicability of these new approximations in different scenarios: 1) statistical characterization of Hoyt fading; 2) performance analysis of communication systems; 3) level crossing statistics of a sampled Rayleigh envelope; and 4) asymptotic approximation of the Rice Ie-function.Universidad de Málaga. Campus de Excelencia Internacional. Andalucía Tech

Sobre los diferenciales y clasificaciones soberanos de economías emergentes

En este trabajo se analizan modelos alternativos de clasificación soberana emergente. Aunque un número pequeño de indicadores económicos fundamentales explica las clasificaciones de manera razonablemente precisa, las variaciones de esos indicadores económicos fundamentales se pueden explicar, en sí mismas, por un puñado de factores mundiales. Por otro lado, hay que tomar en cuenta además las variables financieras mundiales relacionadas con la aversión al riesgo para poder explicar la considerable reducción de los diferenciales a finales de 2006. La prueba es que las clasificaciones sí importan. Por último, el trabajo descubre que los indicadores mundiales de aversión al riesgo han perdido importancia para los diferenciales de mercados emergentes y que el efecto de los últimos acontecimientos en la situación de préstamos hipotecarios de alto riesgo en EE. UU. es de menor magnitud que el efecto de las “noticias promedio” sobre los diferenciales de canjes de incumplimiento crediticio de las economías emergentes.

A New Framework for the Performance Analysis of Wireless Communications under Hoyt (Nakagami-q) Fading

(c) 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works. DOI:10.1109/TIT.2017.2655342We present a novel relationship between the distribution of circular and non-circular complex Gaussian random variables. Specifically, we show that the distribution of the squared norm of a non-circular complex Gaussian random variable, usually referred to as the squared Hoyt distribution, can be constructed from a conditional exponential distribution. From this fundamental connection we introduce a new approach, the Hoyt transform method, that allows to analyze the performance of a wireless link under Hoyt (Nakagami-q) fading in a very simple way. We illustrate that many performance metrics for Hoyt fading can be calculated by leveraging well-known results for Rayleigh fading and only performing a finite-range integral. We use this technique to obtain novel results for some information and communication-theoretic metrics in Hoyt fading channels.Universidad de Málaga. Campus de Execelencia Internacional. Andalucía Tech

Analysis of energy detection of unknown signals under Beckmann fading channels

(c) 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.The Beckmann fading is a general multipath fading model which includes Rice, Hoyt and Rayleigh fading as particular cases. However, the generality of the Beckmann fading also implies a significant increased mathematical complexity. Thus, relatively few analytical results have been reported for this otherwise useful fading model. The performance of energy detection for multi-branch receivers operating under Beckmann fading is here studied, and the inherent analytical complexity is here circumvented by the derivation of a closed-form expression for the generalized moment generating function (MGF) of the received signal-to-noise ratio (SNR), which is a new and useful result, as it is key for evaluating the receiver operating characteristics. The impact of fading severity on the probability of missed detection is shown to be less critical as the SNR decreases. Monte Carlo simulations have been carried out in order to validate the obtained theoretical expressions.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Proyecto MINECO-FEDER TEC2013-42711-R y TEC2013-44442-P. Junta de Andalucía P11-TIC-7109

STRATEGIES DEVELOPED BY LEADING EU AGRI-FOOD COOPERATIVES IN THEIR GROWTH MODEL

The rationale for this paper is the problem relating to the growth of agricultural cooperatives in Spain in recent years in comparison to increasingly concentrated food distribution, which captures most of the value added. This paper analyses the evolution and status of other countries within Europe where the need for business consolidation has been successfully addressed. For this purpose, there have been identified 7 cases to be studied: Kerry group, Irish Dairy Board, Arla Foods, The Greenery BV, Danish Crown, Agrifirm and DLG. The specific results of interviews with the senior management of this cooperatives were analyzed and organized into four blocks in which the issues raised are grouped (legal and institutional framework, strategic vision, business growth models and market standing). A number of specific aims are also pursued:  Identify the main barriers and problems faced by this type of cooperatives.  Show the strategies developed by leading cooperatives in their sector within the current comparative context.  Become familiar with the different growth models these cooperatives use to achieve and maintain their market standing.Agribusiness,

On the Calculation of the Incomplete MGF with Applications to Wireless Communications

(c) 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works. DOI: 10.1109/TCOMM.2016.2626440The incomplete moment generating function (IMGF) has paramount relevance in communication theory, since it appears in a plethora of scenarios when analyzing the performance of communication systems. We here present a general method for calculating the IMGF of any arbitrary fading distribution. Then, we provide exact closed-form expressions for the IMGF of the very general κ-μ shadowed fading model, which includes the popular κ-μ, η-μ, Rician shadowed, and other classical models as particular cases. We illustrate the practical applicability of this result by analyzing several scenarios of interest in wireless communications: 1) physical layer security in the presence of an eavesdropper; 2) outage probability analysis with interference and background noise; 3) channel capacity with side information at the transmitter and the receiver; and 4) average bit-error rate with adaptive modulation, when the fading on the desired link can be modeled by any of the aforementioned distributions.Universidad de Málaga. Campus de Execelencia Internacional. Andalucía Tech

Does post merger financial performance improve after agrifood mergers of cooperatives? An empirican analysis

This study was carried out to characterize the mergers and acquisitions undertaken in the Spanish agrifood sector during the period 1995-2005 and has two objectives. Firstly, it aims to determine the manner in which economic-financial factors influence the type of merger carried out (merger by formation of a new legal person and merger by acquisition), and the role played by cooperatives (acquirer, acquired or cooperative involved in a merger by formation). Secondly, it aims to determine whether these mergers have contributed to reaching any of the objectives they were set out to achieve: improving the economic-financial situation of the companies involved, increasing income and reducing relative costs. The results obtained show that on average, following a merger, there were no statistically significant improvements in the economic-financial indicators studied.Agribusiness, Agricultural Finance,

The κ-µ Shadowed Fading Model with Integer Fading Parameters

(c) 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works. DOI: 10.1109/TVT.2017.2678430We show that the popular and general κ-μ shadowed fading model with integer fading parameters μ and m can be represented as a mixture of squared Nakagami- m̂ (or Gamma) distributions. Thus, its PDF and CDF can be expressed in closed-form in terms of a finite number of elementary functions (powers and exponentials). The main implications arising from such connection are then discussed, which can be summarized as: (1) the performance evaluation of communication systems operating in κ-μ shadowed fading becomes as simple as if a Nakagami- m̂ fading channel was assumed; (2) the κ-μ shadowed distribution can be used to approximate the κ-μ distribution using a closed-form representation in terms of elementary functions, by choosing a sufficiently large value of m; and (3) restricting the parameters μ and m to take integer values has limited impact in practice when fitting the κ-μ shadowed fading model to field measurements. As an application example, the average channel capacity of communication systems operating under κ-μ shadowed fading is obtained in closed-form.Universidad de Málaga. Campus de Excelencia Internacional. Andalucía Tech

The fluctuating two-ray fading model: exact and approximate statistical characterization

El congreso en el que se ha presentado este artículo no genera libro de actas, por lo que el copyright no se ha transferido a IEEE.We introduce the Fluctuating Two-Ray (FTR) fading model, a new statistical channel model that consists of two fluctuating specular components with random phases plus a diffuse component. The PDF and MGF are expressed in closed-form, having a functional form similar to other state-of-the-art fading models. We also provide an approximate closed-form expressions for the PDF, which allow for a simple evaluation of these statistics to an arbitrary level of precision. We show that the FTR fading model provides a much better fit than Rician fading for recent small-scale fading measurements in 28 GHz outdoor millimeter-wave channels.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Proyecto MINECO-FEDER TEC2013-42711-R, TEC2014-57901-R y TEC2013-44442-P. Junta de Andalucía P2011-TIC-7109 y P2011-TIC-8238