Recently, the Fisher-Snedecor F distribution was proposed to model the turbulence in free-space optical (FSO) communications. However, the existing model does not consider pointing error impairment. To fill this gap, in this paper, we derive novel closed-form expressions for the probability density function (PDF) and cumulative distribution function (CDF) for irradiance fluctuations in the presence of pointing error impairments. Subsequently, the PDF and CDF of the received signal-to-noise ratio (SNR) are derived and employed to obtain novel closed-form expressions for the outage probability, average bit error rate, and average ergodic capacity. To gain more insight into the impact of system and turbulence channel parameters, simple and accurate asymptotic expressions are further derived. Our analytical results are supported by Monte-Carlo simulations to validate the analysis.

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.

In this letter, the impact of the non-linearity of the propagation medium is studied in fluid antennas systems (FAS) systems. First and second order statistics are deduced for FAS under α-μ fading channels. Based on this and in order to evaluate the performance of the mentioned systems, expressions are also deduced for the outage probability (OP) and ergodic channel capacity. Furthermore, an exact reduction of the OP due to N-th port for an (N-1)-port is also presented. All the expressions emerging from this study are entirely new, marking a significant contribution to the existing body of knowledge. Several curves are shown under different values for the system parameters and channel non-linearity. This is the first work in which the effect of the channel non-linearity is evidenced in a FAS.

Medical healthcare is one of the fascinating applications using Internet of Things (IoTs). The pervasive smart environment in IoTs has the potential to monitor various human activities by deploying smart devices. In our pilot study, we look at narcolepsy, a disorder in which individuals lose the ability to regulate their sleep-wake cycle. An imbalance in the brain chemical called orexin makes the sleep pattern irregular. This sleep disorder in patients suffering from narcolepsy results in them experience irrepressible sleep episodes while performing daily routine activities. This study presents a novel method for detecting sleep attacks or sleepiness due to immune system attacks and affecting daily activities measured using the S-band sensing technique. The S-Band sensing technique is channel sensing based on frequency spectrum sensing using the orthogonal frequency division multiplexing transmission at a 2 to 4 GHz frequency range leveraging amplitude and calibrated phase information of different frequencies obtained using wireless devices such as card, and omni-directional antenna. Each human behavior induces a unique channel information (CI) signature contained in amplitude and phase information. By linearly transforming raw phase measurements into calibrated phase information, we ascertain phase coherence. Classification and validation of various human activities such as walking, sitting on a chair, push-ups, and narcolepsy sleep episodes are done using support vector machine, K-nearest neighbor, and random forest algorithms. The measurement and evaluation were carried out several times with classification values of accuracy, precision, recall, specificity, Kappa, and F-measure of more than 90% that were achieved when delineating sleep attacks.

The performance of the effective capacity metric under Fisher–Snedecor fading channels is investigated. To this end, a novel exact closed‐form expression for the effective capacity is derived. Furthermore, in order to gain more insight, a simple asymptotic expression at the high signal‐to‐noise ratio regime is also provided. Additionally, expressions for the effective capacity of the Nakagami‐ m and Rayleigh distributions are deduced from the proposed results as special cases. The analytical results are compared to Monte‐Carlo simulations to prove the correctness of the analysis. The results show that fading has a more positive influence on effective capacity performance than shadowing.

In this paper, we consider Terahertz (THz) communications in the presence of pointing error impairments (misalignment) and under random fog conditions. We derive closed-form expressions, in terms of I-function, for the probability density function (PDF) and the cumulative distribution function (CDF). Then, the PDF and the CDF are employed to derive closed-form expressions for the outage probability, average symbol error rate (SER), and ergodic channel capacity. Additionally, very tight simple approximations in the high signal-to-noise ratio for the outage probability and average SER are provided. The derived expressions are validated through numerical and Monte-Carlo simulation results.