arXiv subjects

F. J. Lopez-Martinez

Publications and source records attributed to F. J. Lopez-Martinez.

7 recordsLinked to original sources

arXiv2024

The Multi-cluster Two-Wave Fading Model

We introduce and characterize the Multi-cluster Two-Wave (MTW) fading model, which generalizes \textit{both} the Durgin's Two-Wave with Diffuse Power (TWDP) and the $κ$-$μ$ models under a common umbrella. The MTW model consists of an arbitrary number of clusters of waves each of which may include one or two dominant (specular) components. The chief probability functions of the MTW fading model are obtained, including the probability density function, the cumulative distribution function and the generalized moment-generating function. \textcolor{black}{The proposed model is empirically validated using channel measurements in the sub-THz band and} a number of applications are exemplified, including the outage probability in noise-limited and interference-limited scenarios and the energy detection probability. %Exact expressions for the outage capacity are also obtained. A composite Inverse Gamma (IG)/MTW model is also investigated, thus extending the proposed propagation model to include shadowing.

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arXiv2021

Capacity of Backscatter Communication under Arbitrary Fading Dependence

We analyze the impact of arbitrary dependence between the forward and backward links in backscatter communication systems. Specifically, we quantify the effect of positive and negative dependence between these fading links on channel capacity, using Copula theory. The benefits of this approach are highlighted over the classical framework of linear dependence based on Pearson's correlation coefficient, which is also analyzed. Results show that for a fixed transmit power budget, capacity grows with positive dependence as well as with fading severity in the low signal-to-noise ratio (SNR) regime. Conversely, fading dependence becomes immaterial in the high SNR regime.

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arXiv2020

On the Effect of Correlation on the Capacity of Backscatter Communication Systems

We analyse the effect of correlation between the forward and backward links on the capacity of backscatter communication systems. To that aim, we obtain an analytical expression for the average capacity under a correlated Rayleigh product fading channel, as well as closed-form asymptotic expressions for the high and low signal-to-noise ratio (SNR) regimes. Our results show that correlation is indeed detrimental for a fixed target SNR; contrarily to the common belief, we also see that correlation can be actually beneficial in some instances when a fixed power budget is considered.

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arXiv2018

Statistical Characterization of Second Order Scattering Fading Channels

We present a new approach to the statistical characterization of the second order scattering fading (SOSF) channel model, which greatly simplifies its analysis. Exploiting the unadvertised fact that the SOSF channel can be seen as a continuous mixture of Rician fading channels, we obtain expressions for its probability density function and cumulative density function that are numerically better-behaved than those available in the literature. Our approach allows for obtaining new results for the SOSF model, such as a closed-form expression for its moment-generating function, as well as the characterization of the average channel capacity. Relevantly, and somehow counterintuitively, we observe that in the presence of a strong line-of-sight (LOS) component, the channel capacity of a LOS plus double-Rayleigh scattered diffuse component is larger than its LOS plus Rayleigh (i.e Rician-like) counterpart.

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arXiv2016

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

The 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.

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arXiv2013

Connections between the Generalized Marcum Q-Function and a class of Hypergeometric Functions

This paper presents a new connection between the generalized Marcum-Q function and the confluent hypergeometric function of two variables, phi3. This result is then applied to the closed-form characterization of the bivariate Nakagami-m distribution and of the distribution of the minimum eigenvalue of correlated non-central Wishart matrices, both important in communication theory. New expressions for the corresponding cumulative distributions are obtained and a number of communication-theoretic problems involving them are pointed out.

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arXiv2012

On the Bivariate Nakagami-$m$ Cumulative Distribution Function: Closed-form Expression and Applications

In this paper, we derive exact closed-form expressions for the bivariate Nakagami-$m$ cumulative distribution function (CDF) with positive integer fading severity index $m$ in terms of a class of hypergeometric functions. Particularly, we show that the bivariate Nakagami-$m$ CDF can be expressed as a finite sum of elementary functions and bivariate confluent hypergeometric $Φ_3$ functions. Direct applications which arise from the proposed closed-form expression are the outage probability (OP) analysis of a dual-branch selection combiner in correlated Nakagami-$m$ fading, or the calculation of the level crossing rate (LCR) and average fade duration (AFD) of a sampled Nakagami-$m$ fading envelope.

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