2026· IEEE Transactions on Wireless Communications· Vol 25, pp. 22211-22226· 0 citations· 31 references
Computer Science
Abstract
Free-space optical (FSO) communication has emerged as a promising technology, but its performance is highly dependent on line-of-sight (LOS) conditions. To address this limitation, we propose a multistage optical intelligent reflecting surface (OIRS)-assisted FSO communication system, which utilizes multiple OIRS nodes to dynamically reflect and redirect optical signals toward the receiver, even in the absence of direct LOS paths. In this work, we first establish a generalized geometric misalignment loss (GML) model for multistage OIRS systems under both two-dimensional (2D) and three-dimensional (3D) deployment scenarios. Building on the 3D GML model, we construct a comprehensive statistical channel model by incorporating Gamma-Gamma (GG) atmospheric turbulence and attenuation losses. Furthermore, we propose a multi-OIRS-assisted unmanned aerial vehicle (UAV)-based non-terrestrial network (NTN) system and analyze its performance. We derive semi closed-form expressions for the outage probability (OP), average bit error rate (BER), channel capacity, and moments of the signal-to-noise ratio (SNR). Additionally, we present asymptotic expressions for OP and BER in the high-SNR regime and determine the diversity order of the system.
Integrating optical intelligent reflecting surfaces (IRSs) into aerial platforms, such as unmanned aerial vehicles (UAVs), has been proposed to relax the line-of-sight (LoS) constraint, extend coverage, and enhance deployment flexibility of free space optical (FSO) systems. However, misalignment errors induced by the UAV hovering, in both position and orientation, may degrade connectivity and impair the end-to-end channel quality. In this paper, we develop novel expressions for the electric fields incident on and reflected by an optical IRS, based on the Huygens-Fresnel principle. The resulting expressions are applicable for any combination of incident and reflected propagation directions. Building on this framework, we derive a closed-form statistical channel model that captures the geometric and misalignment losses of an FSO link assisted by a UAV-mounted IRS in the presence of random UAV fluctuations. In particular, we develop a statistical model for the beam misalignment at the receiver lens, assuming Gaussian fluctuations in both the UAV position and orientation. The proposed analytical model is validated through Monte Carlo (MC) simulations and is further used to provide practical design guidelines regarding the optimal placement of the UAV-mounted IRS for the minimization of the outage probability.
Ferdaous Tarhouni, V. Papanikolaou, L. Cottatellucci et al.· 0 citations
Underwater Visible Light Communication (UVLC) offers high data rates, low latency, and strong physical-layer security, making it as an alternative to acoustic and RF systems for real-time underwater applications. However, its performance is severely degraded by absorption, scattering, and turbulence-induced fading. To enhance link reliability, recent advances in Non-Orthogonal Multiple Access (NOMA) and Intelligent Reflecting Surfaces (IRS) are being integrated into UVLC systems. NOMA enables simultaneous multiuser access through power-domain multiplexing, improving spectral efficiency and connectivity, while IRS enhances signal strength and coverage by intelligently reflecting and directing optical beams. Motivated by these benefits, we propose a hybrid IRSNOMA framework for UVLC to improve link reliability and mitigate turbulence effects. A composite channel model is formulated by combining direct and IRS-reflected paths under absorption, scattering, and turbulence modeled using the Exponential Generalized Gamma (EGG) distribution with pointing errors. Closed-form expressions for the outage probability and average bit error rate (ABER) are derived in terms of the Meijer-G function. System performance is evaluated under various configurations, and Monte Carlo simulations validate the analytical results, demonstrating excellent match and highlighting the effectiveness of the proposed IRSNOMA-assisted UVLC design.
Mahesh Miriyala, Prathibha Praharsha Sripathi· IEEE Latin America Transacti...· 0 citations
This paper exploits the line-of-sight (LoS) and dominant single-bounce non line-of-sight (NLoS) propagation characteristics of millimeter wave (mmWave)/terahertz (THz) channels to facilitate joint position and velocity vector sensing in integrated sensing and communication (ISAC) systems. We develop a signal model that captures how the velocity vector is reflected in the angular velocity of the LoS path and the Doppler shifts of these paths, and characterize the fundamental accuracy limits through the position error bound (PEB) and the velocity error bound (VEB). Next, we propose a two-stage estimation framework to approach these bounds in practice. In the first stage, we propose a space-alternating generalized expectationmaximization (SAGE)-maximum likelihood (ML) algorithm to detect propagation paths and estimate the associated channel parameters. In the second stage, the estimated channel parameters are mapped to sensing parameters, and a weighted least squares (WLS) based fusion algorithm is developed to recover the velocity vector by adaptively combining the radial and tangential velocity information provided by the LoS path with the additional radial velocity information extracted from the dominant single-bounce NLoS paths. Furthermore, a weighted non-linear least squares (WNLS) refinement is proposed to adjust estimated sensing parameters. Simulation results demonstrate that the performance asymptotically approaches the corresponding bounds at medium to high signal-to-noise ratios (SNRs), and the proposed algorithms outperform the baselines in both position and velocity estimation accuracy.
Dong-Qi Luo, Qiang Li, Fan Jiang et al.· IEEE Transactions on Wireles...· 0 citations
This paper investigates the outage performance of unmanned aerial vehicle (UAV)-assisted free-space optical (FSO) communication systems operating in foggy channels. The analysis jointly accounts for atmospheric turbulence, fog-induced attenuation, generalized Beckmann-distributed pointing errors (PE), and angle-of-arrival (AoA) fluctuations caused by UAV orientation jitter. A comprehensive statistical channel model is developed, from which closed-form expressions for outage probability and an analytical characterization of outage capacity are derived. The effects of receiver field-of-view (FoV) limitations and multi-UAV amplify-and-forward relaying on link reliability are also investigated. Numerical results validate the proposed analysis and reveal that AoA fluctuations impose a fundamental performance limit, resulting in an outage floor, particularly under dense fog and narrow-FoV conditions. These findings provide practical design insights for improving the reliability of UAV-assisted FSO communication systems in adverse weather environments.
Mahdi Ataee, S. Sadough, Khadijeh Ali Mahmoodi· EAI Endorsed Transactions on...· 0 citations
In this paper, we study the multi-target detection problem in a movable-antenna (MA)-enabled wireless sensing system with linear arrays, in which both the direct line-of-sight (LoS) paths and the first-order non-LoS (NLoS) paths are explicitly considered. Unlike conventional fixed-position antenna arrays, MAs provide additional design degrees of freedom by enabling adaptive antenna positioning to reconfigure the propagation geometry, offering great potential to enhance the sensing performance in complex multi-target multipath scenarios. Under this setup, we first develop a cross sparsity Markov mixture prior to derive the posterior probabilities of target locations, in which the structural correlation between the LoS and NLoS paths is effectively exploited to enhance the location estimation accuracy. Based on the derived posterior probabilities, we further analyze the angular-domain sensing performance for multi-target detection by proposing a new two-dimensional (2D) ambiguity function as the performance metric. Next, we optimize the MA positions to suppress the sidelobe levels and narrow the mainlobe width of the proposed ambiguity function. Although the resulting problem is highly non-convex, we develop a low-complexity Dykstra-based projected gradient descent algorithm to solve it efficiently. Finally, simulation results verify the accuracy of the proposed ambiguity function analysis, demonstrate the substantial performance gains enabled by the proposed prior model and MAs, and show that the proposed algorithm achieves performance comparable to existing methods with significantly lower computational complexity.
This paper investigates the performance of an intelligent reflecting surface (IRS)-assisted free-space optical (FSO) communication system employing rate-splitting multiple access. The FSO channel is modeled using the Gamma–Gamma fading distribution while accounting for pointing errors and supporting both heterodyne detection and intensity modulation with direct detection. Closed-form expressions for critical performance metrics, including outage probability, average bit error rate, and average capacity, are derived and validated through numerical simulations. The analysis incorporates essential factors such as attenuation ( α), atmospheric turbulence ( β), and pointing error ( ζ), along with various power allocation strategies. The findings highlight the substantial impact of these parameters on system performance, offering valuable guidance for the optimization of IRS-assisted FSO networks.
Aswini Krishnan, Surendar Maruthu· Engineering Research Express· 0 citations
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