Composite Fading Models based on Inverse Gamma Shadowing: Theory and Validation

We introduce a general approach to characterize composite fading models based on inverse gamma (IG) shadowing. We first determine to what extent the IG distribution is an adequate choice for modeling shadow fading, by means of a comprehensive test with field measurements and other distributions conventionally used for this purpose. Then, we prove that the probability density function and cumulative distribution function of any IG-based composite fading model are directly expressed in terms of a Laplace-domain statistic of the underlying fast fading model and, in some relevant cases, as a mixture of wellknown state-of-the-art distributions. Also, exact and asymptotic expressions for the outage probability are provided, which are valid for any choice of baseline fading distribution. Finally, we exemplify our approach by presenting several application examples for IG-based composite fading models, for which their statistical characterization is directly obtained in a simple form.Comment: This work has been submitted to the IEEE for publication. Copyright may be transferred without notice, after which this version may no longer be accessibl

On the Utility of the Inverse Gamma Distribution in Modeling Composite Fading Channels

We introduce a general approach to characterize composite fading models based on inverse gamma (IG) shadowing. We first determine to what extent the IG distribution is an adequate choice for modeling shadow fading, by means of a comprehensive test with field measurements and other distributions conventionally used for this purpose. Then, we prove that the probability density function and cumulative density function of any IG-based composite fading model are directly expressed in terms of a Laplace-domain statistic of the underlying fast fading model, and in some relevant cases, as a mixture of well-known state-of-the-art distributions. We exemplify our approach by presenting a composite IG/two-wave with diffuse power fading model, for which its statistical characterization is directly attained in a simple form.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Backing off from rayleigh and rice: Achieving perfect secrecy in wireless fading channels

We show that for a legitimate communication under multipath quasi-static fading with a reduced number of scatter- ers, it is possible to achieve perfect secrecy even in the presence of a passive eavesdropper for which no channel state information is available. Specifically, we show that the outage probability of secrecy capacity (OPSC) is zero for a given range of average signal-to-noise ratios (SNRs) at the legitimate and eavesdropper’s receivers. As an application example, we analyze the OPSC for the case of two scatterers, explicitly deriving the relationship between the average SNRs, the secrecy rate RS and the fading model parameters required for achieving perfect secrecy.Ministerio de Ciencia e Innovación (TEC2017-87913R) Consejería de Innovación y Ciencia (P18-RT-3175

Delivering Ultra-Reliable Low-Latency Communications via Statistical Radio Maps

High reliability guarantees for Ultra-Reliable Low-Latency Communications (URLLC) require accurate knowledge of channel statistics, used as an input for rate selection. Exploiting the spatial consistency of channel statistics arises as a promising solution, allowing a base station to predict the propagation conditions and select the communication parameters for a new user from samples collected from previous users of the network. Based on this idea, this article provides a timely framework to exploit long-range channel spatial correlation through so-called statistical radio maps, enabling URLLC communications with given statistical guarantees. The framework is exemplified by predicting the channel capacity distribution both in a location-based radio map and in a latent space rendered by a channel chart, the latter being a localization-free approach based on channel state information (CSI). It is also shown how to use the maps to select the transmission rate in a new location that achieves a target level of reliability. Finally, several future directions and research challenges are also discussed.Comment: 6 figures in total. Submitted for publicatio

Multiuser MIMO with Large Intelligent Surfaces: Communication Model and Transmit Design

This paper proposes a communication model for multiuser multiple-input multiple-output (MIMO) systems based on large intelligent surfaces (LIS), where the LIS is modeled as a collection of tightly packed antenna elements. The LIS system is first represented in a circuital way, obtaining expressions for the radiated and received powers, as well as for the coupling between the distinct elements. Then, this circuital model is used to characterize the channel in a line-of-sight propagation scenario, rendering the basis for the analysis and design of MIMO systems. Due to the particular properties of LIS, the model accounts for superdirectivity and mutual coupling effects along with near field propagation, necessary in those situations where the array dimension becomes very large. Finally, with the proposed model, the matched filter transmitter and the weighted minimum mean square error precoding are derived under both realistic constraints: limited radiated power and maximum ohmic losses.Comment: 6 pages, 3 figures; This paper is submitted to IEEE International Conference on Communications (ICC) 202

A new Approach to the Statistical Analysis of Non-Central Complex Gaussian Quadratic Forms With Applications

This paper proposes a novel approach to the statistical characterization of non-central complex Gaussian quadratic forms (CGQFs). Its key strategy is the generation of an auxiliary random variable that replaces the original CGQF and converges in distribution to it. This technique is valid for both definite and indefinite CGQFs and yields simple expressions of the probability density function (PDF) and the cumulative distribution function (CDF) that only involve elementary functions. This overcomes a major limitation of previous approaches, where the complexity of the resulting PDF and CDF does not allow for further analytical derivations. Additionally, the mean square error between the original CGQF and the auxiliary one is provided in a simple closed-form formulation. These new results are then leveraged to analyze the outage probability and the average bit error rate of maximal ratio combining systems over correlated Rician channels

An Extension of the κ -μ Shadowed Fading Model: Statistical Characterization and Applications.

Política de acceso abierto tomada de: https://v2.sherpa.ac.uk/id/publication/3582We here introduce an extension and natural generalization of both the κ-μ shadowed and the classical Beckmann fading models: the Fluctuating Beckmann (FB) fading model. This new model considers the clustering of multipath waves on which the line-of-sight (LoS) components randomly fluctuate, together with the effect of in-phase/quadrature power imbalance in the LoS and non-LoS components. Thus, it unifies a variety of important fading distributions as the one-sided Gaussian, Rayleigh, Nakagami-m, Rician, κ-μ, η-μ, η-κ, Beckmann, Rician shadowed, and the κ-μ shadowed distribution. The chief probability functions of the FB fading model, namely probability density function, cumulative distribution function, and moment generating function are derived. The second-order statistics such as the level crossing rate and the average fade duration are also analyzed. These results can be used to derive some performance metrics of interest of wireless communication systems operating over FB fading channels.Consejería de Economía, Innovación, Ciencia y Empleo of the Junta de Andalucía Spanish Government European Fund for Regional Development FEDER ( Grant Numbers: P2011-TIC-7109, P2011-TIC-8238 and TEC2014-57901-R

Effectiveness of autologous lipoinjection into the hand to improve function in patients with scleroderma: pilot study

Background: Scleroderma is a rare disease of the tissues that is characterized for being inflammatory and developing fibrosis in the skin. Typically, this disease affects middle-aged women.Methods: A study was conducted in which 10 patients with scleroderma with involvement in the sclerotic stage were included. One of the hands was chosen randomly for treatment with fatty graft processed by Coleman technique and the other hand, physiological solution was placed. Patients were evaluated at 45 and 90 days after the procedure using the Cochin Hand Functional Scale (CHFS) questionnaire, modified Rodnan scale for the skin (mRSS), grip strength with dynamometer and measurement of fingertip to palm of hand in flexion.Results: The average of CHFS before treatment was 42.30 and 25.70 at 90 days p=0.007. The average strength in the experimental hand before treatment was 11.67 and 14.58 at 90 days p=0.007, in the control hand p=0.873. The mean finger-palm tip distance before treatment was 44.80 and from 36.00 to 90 days p=0.019, in the control hand p=0.149. There is a significant difference in the degree of severity at 90 days of the mRSS of the back of the hands p=0.011 and phalanges p=0.000 between the patients with lipoinjection and physiological solution.Conclusion: Significant improvement was observed in patients with scleroderma treated with autologous lipoinjection