On the Sum of Fisher-Snedecor F Variates and its Application to Maximal-Ratio Combining

Capitalizing on the recently proposed Fisher-Snedecor F composite fading model, in this letter, we investigate the sum of independent but not identically distributed (i.n.i.d.) Fisher-Snedecor F variates. First, a novel closed-form expression is derived for the moment generating function of the instantaneous signal-to-noise ratio. Based on this, the corresponding probability density function and cumulative distribution function of the sum of i.n.i.d. Fisher- Snedecor F variates are derived, which are subsequently employed in the analysis of multiple branch maximal-ratio combining (MRC). Specifically, we investigate the impact of multipath and shadowed fading on the outage probability and outage capacity of MRC based receivers. In addition, we derive exact closed-form expressions for the average bit error rate of coherent binary modulation schemes followed by an asymptotic analysis which provides further insights into the effect of the system parameters on the overall performance. Importantly, it is shown that the effect of multipath fading on the system performance is more pronounced than that of shadowing.Comment: 5 pages, 3 figure

Entropy and Energy Detection-based Spectrum Sensing over F Composite Fading Channels

In this paper, we investigate the performance of energy detection-based spectrum sensing over F composite fading channels. To this end, an analytical expression for the average detection probability is firstly derived. This expression is then extended to account for collaborative spectrum sensing, square-law selection diversity reception and noise power uncertainty. The corresponding receiver operating characteristics (ROC) are analyzed for different conditions of the average signal-to-noise ratio (SNR), noise power uncertainty, time-bandwidth product, multipath fading, shadowing, number of diversity branches and number of collaborating users. It is shown that the energy detection performance is sensitive to the severity of the multipath fading and amount of shadowing, whereby even small variations in either of these physical phenomena can significantly impact the detection probability. As a figure of merit to evaluate the detection performance, the area under the ROC curve (AUC) is derived and evaluated for different multipath fading and shadowing conditions. Closed-form expressions for the Shannon entropy and cross entropy are also formulated and assessed for different average SNR, multipath fading and shadowing conditions. Then the relationship between the Shannon entropy and ROC/AUC is examined where it is found that the average number of bits required for encoding a signal becomes small (i.e., low Shannon entropy) when the detection probability is high or when the AUC is large. The difference between composite and traditional small-scale fading is emphasized by comparing the cross entropy for Rayleigh and Nakagami-m fading. A validation of the analytical results is provided through a careful comparison with the results of some simulations.Comment: 30 pages, 11 figures, 1 table, Submitted to IEEE TCO

Reconfigurable Intelligent Surface Enabled IoT Networks in Generalized Fading Channels

This paper studies an Internet-of-Things (IoT) network employing a reconfigurable intelligent surface (RIS) over generalized fading channels. Inspired by the promising potential of RIS-based transmission, we investigate a RIS-enabled IoT network with the source node employing a RIS-based access point. The system is modelled with reference to a receivertransmitter pair and the Fisher-Snedecor F model is adopted to analyse the composite fading and shadowing channel. Closedform expressions are derived for the system with regards to the average capacity, average bit error rate (BER) and outage probability. Monte-Carlo simulations are provided throughout to validate the results. The results investigated and reported in this study extend early results reported in the emerging literature on RIS-enabled technologies and provides a framework for the evaluation of a basic RIS-enabled IoT network over the most common multipath fading channels. The results indicate the clear benefit of employing a RIS-enabled access point, as well as the versatility of the derived expressions in analysing the effects of fading and shadowing on the network. The results further demonstrate that for a RIS-enabled IoT network, there is the need to balance between the cost and benefit of increasing the RIS cells against other parameters such as increasing transmit power, especially at low SNR and/or high to moderate fading/shadowing severity

Full-Duplex Energy-Harvesting Enabled Relay Networks in Generalized Fading Channels

This paper analyzes the performance of a full-duplex decode-and-forward relaying network over the generalized \kappa-\mu fading channel. The relay isenergy-constrained and relies entirely on harvesting the power signal transmitted by the source based on the time-switching relaying protocol. A unified analytical expression for the ergodic outage probability is derived for the system under consideration. This is then used to derive closed-form analytical expressions for three special cases of the \kappa-\mu fading model, namely, Nakagami-m, Rice and Rayleigh. Monte Carlo simulations are provided throughout to verify the correctness of our analysis

Performance Analysis of Intelligent Reflecting Surface Aided Wireless Networks with Wireless Power Transfer

The low efficiency of wireless power transfer (WPT) poses a key challenge for energy-constrained wireless networks. To address this issue, in this letter, the integration of intelligent reflecting surface (IRS) into a WPT network is investigated. To this end, an accurate approximation for the probability density function of the end-to-end cascaded fading channel is presented. By leveraging the derived result, accurate closed-form expressions of the outage probability (OP) and average symbol error probability (ASER) are derived for the proposed IRS-aided WPT system. To gain further insight into the system performance, asymptotic closed-form expressions for the ASER and OP are further derived and interesting observations are reported. Particularly, our asymptotic analysis reveals that the achievable diversity in the underlying scenario is independent of the reflective elements of the IRS. The analytical derivations, corroborated by simulation results, demonstrate that IRSs can be promising candidates for the realization of a highly efficient power transfer enabled wireless network.acceptedVersionPeer reviewe

On the Secrecy Capacity of Fisher - Snedecor F Fading Channels

The performance of physical-layer security of the classic Wyner's wiretap model over Fisher-Snedecor F composite fading channels is considered in this work. Specifically, the main channel (i.e., between the source and the legitimate destination) and the eavesdropper's channel (i.e., between the source and the illegitimate destination) are assumed to experience independent quasi-static Fisher-Snedecor F fading conditions, which have been shown to be encountered in realistic wireless transmission scenarios in conventional and emerging communication systems. In this context, exact closed-form expressions for the average secrecy capacity (ASC) and the probability of non-zero secrecy capacity (PNSC) are derived. Additionally, an asymptotic analytical expression for the ASC is presented. The impact of shadowing and multipath fading on the secrecy performance is investigated. Our results show that increasing the fading parameter of the main channel and/or the shadowing parameter of the eavesdropper's channel improves the secrecy performance. The analytical results are compared with Monte-Carlo simulations to validate the analysis

The N∗ Fisher-Snedecor F Cascaded Fading Model

The Fisher-Snedecor F distribution was recently proposed as an accurate and tractable composite fading model in the context of device-to-device communications. The present work derives the product of the Fisher-Snedecor F composite fading model, which is useful in characterizing fading effects in numerous realistic communication scenarios. To this end, novel analytic expressions are first derived for the probability density function, the cumulative distribution function and the moment of the product of N statistically independent, but not necessarily identically distributed, Fisher-Snedecor F random variables. Capitalizing on these expressions, we derive tractable closed-form expressions for channel quality estimation of the proposed model as well as the corresponding outage probability and average bit error probability for binary modulations. The offered results are corroborated by extensive Monte-Carlo simulation results, which verify the validity of the derived expressions. It is shown that the number of cascaded channels affects considerably the corresponding performance, as a variation of over an order of magnitude is observed across all signal-to-noise ratio regimes