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Nowadays, unmanned aerial vehicle (UAV) communication systems are commonly considered as one of the key enabling technologies for 6G. The hybrid free space optical (FSO)/radio frequency (RF) system has the advantages of both FSO and RF links to improve communication system performance, and the relay-assisted system adopts multi-hop transmission and cooperative diversity methods to extend communication coverage. Thus, a joint consideration of UAV-assistedUAV assisted relay in hybrid FSO/RF transmission is meaningful. In this paper, we aim to analyze the performance of UAV-assisted multi-hop parallel hybrid FSO/RF communication systems with and without pointing errors (PE) in terms of Bit Error Rate (BER) and outage probability. In our considered system, the FSO sub-link adopts the Exponential Weibull turbulence model and the RF sub-link suffers the Nakagami fading model. With these, new mathematical formulas of both BER and outage probability are derived under the UAV-assisted hybrid FSO/RF with different modulation methods. Through numerical evaluationnumerical simulations, the performances of UAV-assisted hybrid FSO/RF systems are analyzed under different weather conditions, modulation methods, optical receiver aperture, RF fading parameters, pointing errors, and relay structures. The results demonstrate that (1) compared to hybrid FSO/RF direct links, UAV-assisted hybrid FSO/RF systems can further improve system performance; (2) the performance of UAV-assisted hybrid FSO/RF systems varies with different relay structures; (3) large receiver aperture and RF fading parameters can further improve the communication performance of hybrid FSO/RF direct links and UAV-assisted hybrid FSO/RF systems.

In this paper, the performance of dual-hop relay transmission in modern wireless communication systems is analyzed by considering two fundamental relaying techniques, namely, Amplify-and-Forward (AF) and Decode-and-Forward (DF). The propagation conditions on the source–relay (S-R) and relay–destination (R-D) links are modeled using the κ-μ statistical distribution, which effectively captures the fading characteristics in both line-of-sight (LoS) and non-line-of-sight (NLoS) environments. The analysis focuses on key performance metrics, including the outage probability (Pout) and average bit error probability (Pe), for Binary Phase Shift Keying (BPSK) and Quadrature Phase Shift Keying (QPSK) modulation schemes, assuming transmission via a single relay without a direct S–D link. Closed-form expressions for the considered metrics are derived based on the κ-μ model and verified by numerical evaluation. In addition to classical analytical modeling, a Generative Artificial Intelligence (GenAI)-enabled workflow is incorporated as a supportive tool in order to aid in automated analysis, the interpretation of the results in the context of network management under varying channel and system parameters based on the Pout and Pe calculations with the aim to tackle the underlying complexity and cognitive load of infrastructure adaptation and re-configuration operations. The combined analytical and GenAI-assisted approach provides valuable insights for the optimization, design, and continuous evolution of robust relay-based architectures in next-generation wireless networks.

Badarneh and da Costa (IEEE Wirel Commun Lett, 2024. https://doi.org/10.1109/LWC.2024.3353620 ) introduced the fluctuating fading distribution by taking the signal envelope to be the ratio of two independent random variables, one having the Nakagami m distribution and the other a uniform random variable. The Nakagami m distribution corresponds to signals following the normal distribution which may not always hold in practice. In this paper, we derive twenty other fluctuating fading distributions. For each distribution, we give explicit expressions for the average channel capacity and the average bit error rate. Their correctness is checked numerically.

Recently, free-space optical (FSO) communication systems utilizing unmanned aerial vehicle (UAV) relays have garnered significant attention. Integrating UAV relays into FSO communication and employing cooperative diversity techniques not only fulfill the need for long-distance transmission but also enable flexible adjustments of relay positions based on the actual environment. This paper investigates the performance of a parallel-UAV-relay-based FSO communication system. In the considered system, the channel fadings include atmospheric loss, atmospheric turbulence, pointing errors, and angle-of-arrival fluctuation. Using the established channel model, we derive a tractable expression for the probability density function of the total channel gain. Then, we derive closed-form expressions of the system outage probability (OP) and average bit error rate (ABER). Moreover, we also derive the asymptotic OP and ABER for a high-optical-intensity regime. Our numerical results validate the accuracy of the derived theoretical expressions. Additionally, the effects of the number of relay nodes, the field of view, the direction deviation, the signal-to-noise ratio threshold, the atmospheric turbulence intensity, the transmit power, and the transmission distance on the system’s performance are also discussed.

In this paper, the performance of an indoor visible light communication (VLC) system in the presence of Gaussian-plus-Laplacian additive noise is investigated. Initially, a realistic VLC system model is established by considering the effects of channel gain and Gaussian-plus-Laplacian additive noise. Theoretical expressions of the average bit error rate (ABER) and average channel capacity are derived, respectively. To show the system performance at a high signal-to-noise ratio, the asymptotic ABER expression is obtained. Numerical results show that all theoretical results agree well with the simulation results. Moreover, the effects of Laplacian noise scale parameter, dimming target, Lambertian order, and the radius of the receiver zone on system performance are also discussed.

In this paper, a proposed circular polarized shift keying (CPolSK) is analyzed for free space optical (FSO) communication system under Ғ distribution channel model and Malaga ( M ) distribution channel model. The proposed CPolSK FSO system contains two feedback paths at the receiver section, in which one for correcting the polarization error in the polarization controller and the other for correcting the slow frequency fluctuations in the local oscillator (LO). Also, two 90 0 optical hybrids are used for mixing the incoming polarized signal and the polarized LO signal. Average BER (ABER) expressions and outage probability expressions are derived for the CPolSK FSO communication system under Ғ distribution channel model and M distribution channel model. The results for different atmospheric turbulence (AT) conditions, phase noise variance and polarization control error are analyzed. Also, the system outage probability for different phase noise variance 0.085 π , 0.25 π and 0.625 π for different SNR thresholds for low AT condition are analyzed. In the results, it can be observed that the ABER performance improves as AT conditions improve, as the phase noise variance decreases and as the polarization control decreases. Also, when AT conditions get worse, then to get same outage probability, we have to increase the SNR threshold. Varying the phase noise variance for δ 2 = 0.085 π to δ 2 = 0.625 π at low AT condition resulted in a power penalty of more than 4 dB for the same outage probability at 0.3. Additionally, it is observed that the M distribution channel model has a steeper slope in the outage probability against normalised threshold graph than the Ғ distribution channel model.

A general framework for performance analysis of error probability over the fluctuating two ray (FTR) fading model with maximal ratio combining (MRC) receive diversity is presented in this paper. The probability density function (PDF) of FTR fading model with MRC is derived by using characteristic function method. Furthermore, the PDF approach is used to formulate the generalized average bit error rate (ABER) expression in closed-form. These generalized expressions are relevant for various modulation schemes for L branches of diversity receivers. The expressions of ABER for coherent modulation schemes with MRC diversity are derived by employing the tight, simple, and accurate approximation of the complementary error function. The calculated results are found to be close and accurate. The expressions of ABER for non-coherent modulation schemes with MRC diversity are calculated in exact closed-form. The validity of obtained expressions is verified with the special cases of FTR model exist in the literature. The main focus of the work is on how the MRC diversity elevates the reliability in communication by diminishing the channel fluctuations due to fading.

In this paper, we have proposed an adaptive pulse position modulation—Gaussian minimum shift keying—subcarrier intensity modulation (PPM-GMSK-SIM) system over Ғ distribution channel model with pointing error. Here, in our proposed system, an adaptive method is used to mitigate the performance degradation due to atmosphere turbulence (AT). In this method, the modulation order adapts according to instantaneous AT under a target an average bit error rate (ABER) and automatically adjust the modulation order at the receiver accordingly and inform it to the transmitter to adapt the modulation order via a feedback path. We derived ABER for PPM-GMSK-SIM system over Ғ distribution channel model. Moreover, we derived an achievable spectral efficiency and ABER expressions for the adaptive PPM-GMSK-SIM system. Here, we compared the performance of proposed PPM-GMSK-SIM modulation system with the PPM-MSK-SIM modulation system over Ғ distribution channel model and observed that the proposed PPM-GMSK-SIM gives better performance than the PPM-MSK-SIM system and the improvement in the ABER performance is approximately 6 dB at ABER value is 10 - 3 in weak, moderate and strong atmospheric turbulence conditions. Also, the ABER versus received average irradiance performance is approximately 2 dB better in the weak AT and it is approximately 3 dB for moderate AT and strong AT conditions at ABER value is 10 - 3 . We compared the spectral efficiency of the adaptive PPM-GMSK-SIM for target ABER values 10 - 2 and 10 - 3 and observed that the spectral efficiency improves as target ABER decreases and compared the ABER performance of the PPM-GMSK-SIM with the adaptive PPM-MSK-SIM system over Ғ distribution channel model and observed that the system performance improves about 11 dB at SNR value is 10 - 3 .

Reconfigurable intelligent surfaces (RIS) and massive multiple input and multiple output (M-MIMO) are the two major enabling technologies for next-generation networks, capable of providing spectral efficiency (SE), energy efficiency (EE), array gain, spatial multiplexing, and reliability. This work introduces an RIS-assisted millimeter wave (mmWave) M-MIMO system to harvest the advantages of RIS and mmWave M-MIMO systems that are required for beyond fifth-generation (B5G) systems. The performance of the proposed system is evaluated under 3GPP TR 38.901 V16.1.0 5G channel models. Specifically, we considered indoor hotspot (InH)—indoor office and urban microcellular (UMi)—street canyon channel environments for 28 GHz and 73 GHz mmWave frequencies. Using the SimRIS channel simulator, the channel matrices were generated for the required number of realizations. Monte Carlo simulations were executed extensively to evaluate the proposed system’s average bit error rate (ABER) and sum rate performances, and it was observed that increasing the number of transmit antennas from 4 to 64 resulted in a better performance gain of ∼10 dB for both InH—indoor office and UMi—street canyon channel environments. The improvement of the number of RIS elements from 64 to 1024 resulted in ∼7 dB performance gain. It was also observed that ABER performance at 28 GHz was better compared to 73 GHz by at least ∼5 dB for the considered channels. The impact of finite resolution RIS on the considered 5G channel models was also evaluated. ABER performance degraded for 2-bit finite resolution RIS compared to ideal infinite resolution RIS by ∼6 dB.

In this paper, we present a practical partitioned intelligent-reflecting-surface-aided transmit spatial modulation (PIRS-TSM) scheme, where spatial modulation is implemented at the transmitter and partitioning is conducted on the IRS to enhance the spectral efficiency (SE) and reliability for multiple-input single-output (MISO) systems. The theoretical analysis of average bit error rate (ABER) based on maximum likelihood (ML) detection and the computational complexity analysis are provided. Experimental simulations demonstrate that the PIRS-TSM scheme obtains a significant ABER enhancement under the same SE compared to the existing partitioned IRS-aided transmit space shift keying or generalized space shift keying schemes by additionally carrying modulated symbols. Moreover, the system performances with different configurations of antenna numbers and symbol modulation orders under the same SE are investigated as a practical application reference.