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In this paper, we consider the transmission of confidential information over a κ-µ fading channel in the presence of an eavesdropper, who also observes κ-µ fading. In particular, we obtain novel analytical solutions for the probability of strictly positive secrecy capacity (SPSC) and the lower bound of secure outage probability (SOP L ) for channel coefficients that are positive, real, independent and non-identically distributed (i.n.i.d.). We also provide a closed-form expression for the probability of SPSC when the µ parameter is assumed to only take positive integer values. We then apply the derived results to assess the secrecy performance of the system in terms of the average signal-to-noise ratio (SNR) as a function of the κ and µ fading parameters. We observed that for fixed values of the eavesdropper's average SNR, increases in the average SNR of the main channel produce a higher probability of SPSC and a lower secure outage probability (SOP). It was also found that when the main channel experiences a higher average SNR than the eavesdropper's channel, the probability of SPSC improved while the SOP was found to decrease with increasing values of κ and µ for the legitimate channel. The versatility of the κ-µ fading model, means that the results presented in this paper can be used to determine the probability of SPSC and SOP L for a large number of other fading scenarios such as Rayleigh, Rice (Nakagami-n), Nakagami-m, One-Sided Gaussian and mixtures of these common fading models. Additionally, due to the duality of the analysis of secrecy capacity and co-channel interference, the results presented here will also have immediate applicability in the analysis of outage probability in wireless systems affected by co-channel interference and background noise. To demonstrate the efficacy of the novel formulations proposed here, we use the derived equations to provide a useful insight into the probability of SPSC for a range of emerging applications such as cellular device-to-device, vehicle-to-vehicle and body centric fading channels using data obtained from field measurements. Index TermsFading channels, κ − µ fading, secrecy capacity, co-channel interference, device-to-device communications, vehicular communications, body centric communications. N. Bhargav and S. L. Cotton are with the Wireless

We derive closed form outage probability expressions for fixed-gain (FG) and variable-gain (VG) two-way amplifyand-forward (AF) relay networks subject to a nonlinear transmission at the relay. We then derive an explicit expression for the relay gain that optimizes the network's performance. Finally, we show that if the source nodes have no access to the distortion characteristics of the relay's amplifier, which inhibits self-interference removal, the network's performance will change negligibly.

In this letter, we consider a Rician fading envelope which is impacted by dual shadowing processes. We conveniently refer to this as the double shadowed Rician fading model which can appear in two different formats, each underpinned by a different physical signal reception model. The first format assumes a Rician envelope where the dominant component is fluctuated by a Nakagami-m random variable (RV) which is preceded (or succeeded) by a secondary round of shadowing brought about by an inverse Nakagami-m RV. The second format considers that the dominant component and scattered waves of a Rician envelope are perturbed by two different shadowing processes. In particular, the dominant component experiences variations characterized by the product of a Nakagami-m and an inverse Nakagami-m RV, whereas the scattered waves are subject to fluctuations influenced by an inverse Nakagami-m RV. Using the relationship between the shadowing properties of the two formats, we develop unified closed-form and analytical expressions for their probability density function, cumulative distribution function, moment-generating function and moments. All of the expressions are validated through Monte Carlo simulations and reduction to a number of special cases.

In this paper, new, exact expressions for the probability density functions and the cumulative distribution functions of the ratio of random envelopes involving the α-µ, η-µ, and κ-µ fading distributions are derived. The expressions are obtained in terms of easily computable infinite series and also in terms of the multivariable Fox H-function. Some special cases of these ratios, namely, Hoyt/Hoyt, η-µ/Nakagami-m, κ-µ/Nakagami-m, κ-µ/η-µ with an integer µ for the η-µ variate, η-µ/η-µ with an integer µ for only one of the η-µ, and their reciprocals are found in novel exact closed-form expressions. In addition, simple closed-form expressions for the asymptotes of the probability density functions and cumulative distribution functions of all ratios, both for the lower and upper tails of the distributions are derived. In the same way, asymptotes for the bit error rate on a binary signaling channel are obtained in closed-form expressions. To demonstrate the practical utility of these new formulations, an application example is provided. In particular, the secrecy capacity of a Gaussian wire-tap channel used for device-to-device and vehicle-to-vehicle communications is characterized using data obtained from field measurements conducted at 5.8 GHz.