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Performance of Free Space Optical Communication Base on Orbital Angular Momentum with Pointing Errors
摘要： Due to the misalignment of the receiver, the spiral spectrum appears to be extended when the Laguerre-Gaussian beam is applied to atmospheric laser communication. This paper investigates the spiral spectrum spread of the Laguerre-Gaussian beam in the case of receiver misalignment. The analytical expression of Laguerre-Gaussian spiral spectrum under the influence of alignment error is studied by mathematical derivation and simulation. The results show that the detection probability of the original orbital angular momentum (OAM) state varies with the lateral displacement distance and the inclination angle. The bit error rate and channel capacity of each channel were studied to verify the effects of misalignment in multiple OAM communication systems.
关键词： Orbital Angular Momentum,Laguerre-Gaussian beam,Pointing Errors,Free Space Optical Communication,Spiral Spectrum
更新于2025-09-23 15:19:57
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Moment-based Approach for Statistical and Simulative Analysis of Turbulent Atmospheric Channels in FSO Communication
摘要： Free Space Optical (FSO) or wireless optical communication networks involve atmosphere as the channel, which at times can be turbulent in nature, thus degrading the system performance. These turbulent channels can be analysed by introducing various channel models and modulation techniques. Various researchers have analysed the performance by presenting different approaches for each type of channel model. In this paper, we present a uni?ed approach for the performance analysis of Log-normal, Nakagami-n (Rician) and Rayleigh statistical models by deriving the exact closed form expressions for average bit error probability and the outage probability of each model. It is achieved by using alternative form of Q-function and Gauss-Hermite Quadrature approximation to the moment-generating function of the output Signal-to-Noise Ratio (SNR). Further, de?nite expressions for each type of modulation technique are also derived to describe the channel fading in FSO communication system. The system of interest includes M-ary Phase Shift Keying (M-PSK) and M-ary Quadrature Amplitude Modulation (M-QAM) techniques. Moreover, the average output SNR, average received irradiance and the amount of fading (fading strength) are also expressed in simple closed forms for above mentioned turbulent channels. In addition to this, the performance of FSO system in presence of atmospheric turbulence and pointing errors is also investigated. The statistical model is examined for zero and nonzero boresight point errors modelled by Rayleigh and Rician distributions in Log-normal fading channel. The composite Log-normal PDFs along with asymptotic error rate and outage probability are also presented for such system. The effect of Tikhonov distributed phase noise arised due to BPSK modulation on BER performance is evaluated on three turbulent channels by deriving its closed-form expression using moment based approach.The mathematical analysis is veri?ed by comparing numerical results with Monte-Carlo Simulated values and graphs.
关键词： Rayleigh,SNR,BER,phase noise,Log-normal,Nakagami-n,path loss,outage probability,pointing errors
更新于2025-09-19 17:15:36
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Signal Quality Assessment for Transdermal Optical Wireless Communications under Pointing Errors
摘要： In this paper, we assess the signal quality of the out-body to in-body optical communication link, which can be used as a fundamental enabler of novel biomedical appliances, such as medical implants, as well as biological and chemical components monitoring. In particular, we present a mathematical understanding of the transdermal system, which takes into account the optical channel characteristics, the integrated area limitations of the in-body unit, the transceivers’ pointing errors and the particularities of the optical units. Moreover, to accommodate the propagation characteristics, we present a novel simplified, but accurate, transdermal path-gain model. Finally, we extract low-complexity closed-form expressions for the instantaneous and average signal to noise ratio of the transdermal optical link (TOL). Numerical and simulation results are provided for several insightful scenarios and reveal that pointing errors can significantly affect the reliability and effectiveness of the TOL; hence, it should be taken into account in the analysis and design of such systems.
关键词： optical wireless communications,pointing errors,transdermal optical wireless links
更新于2025-09-19 17:15:36
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[IEEE 2019 6th NAFOSTED Conference on Information and Computer Science (NICS) - Hanoi, Vietnam (2019.12.12-2019.12.13)] 2019 6th NAFOSTED Conference on Information and Computer Science (NICS) - Alignment Error Mitigation Techniques for Airborne Free-Space Optical Communication Systems
摘要： We present our recent research activities on the mitigation of impacts of angle-of-arrival fluctuations and alignment errors on the performance of free-space optical communication systems. We report on the adaptive beam control technique and wide field-of-view receiver based on multi-core fiber for the transmitter and receiver, respectively.
关键词： pointing errors,Free-space optical communication (FSOC) systems,angle-of-arrival (AoA) fluctuations
更新于2025-09-19 17:13:59
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Transmit laser selection for two hop decode and forward FSO communication with pointing errors
摘要： In this letter, two systems have been proposed for efficient unidirectional free space optical (FSO) cooperative communication-one with only transmit laser selection (TLS) and the other using optical spatial modulation (OSM) along with TLS. Performance analysis of such systems for Gamma-Gamma (G-G) fading channels both with and without Pointing errors have been carried out in terms of outage probability and average symbol error probability (ASEP). Our proposed TLS system over G-G channel (with pointing error) yields a signal to noise ratio (SNR) gain of at least 10 dBm over the conventional FSO system.
关键词： cooperative communication,Free space optical communication,transmit laser selection,pointing errors,Gamma-Gamma fading,optical spatial modulation
更新于2025-09-12 10:27:22
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Novel approximate and asymptotic expressions of the outage probability and BER in gamma-gamma fading FSO links with generalized pointing errors
摘要： In this paper, a novel closed-form approximate probability density function (PDF) at high signal-to-noise ratio (SNR) for the composite gamma-gamma (GG) atmospheric turbulence with a generalized pointing error model using the Beckmann distribution is derived in terms of an appropriate gamma distribution by a moment generating function (MGF) matching approach. Based on the obtained PDF, novel closed-form approximate and asymptotic expressions for the outage probability and the average bit-error rate (BER) are derived. Then, the average BER performance and the outage performance of the considered FSO system at high SNR are investigated with different turbulence conditions, receiver aperture sizes, nonzero boresight, and different jitter variances. Numerical results and Monte Carlo simulation results verify the accuracy of our derived approximate and asymptotic expressions over a wide SNR range. This work can be further extended as well to diversity links.
关键词： High SNR,Gamma-gamma distribution,Free-space optical communication,Beckmann distribution,Pointing errors,Atmospheric turbulence
更新于2025-09-10 09:29:36
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[IEEE 2018 11th International Symposium on Communication Systems, Networks and Digital Signal Processing (CSNDSP) - Budapest (2018.7.18-2018.7.20)] 2018 11th International Symposium on Communication Systems, Networks & Digital Signal Processing (CSNDSP) - M-ary ASK Modulation in FSO System with SIMO over Log-normal Atmospheric Turbulence with Pointing Errors
摘要： In this paper, we analyze the average bit error rate (BER) and outage probability performances of a free-space optical (FSO) system. We used M-ary amplitude shift keying modulation (M-ary ASK) scheme. Lognormal atmospheric turbulence with the effect of pointing errors (PE) and, path loss is employed to model the FSO channel. However, to overcome the degradation in BER performance due to pointing errors, the single-input-multiple-output technique with maximal ratio combining diversity is used. For instance, the average BER for M=2 without using SIMO is 1.944×10?6 at 0 dBm transmitted power, while the average BER for M=2 with using SIMO technique with N=2 become 1.512×10-11 at 0 dBm. The asymptotic expression for average BER and the closed-form expression for outage probability are both driven and tested with and without SIMO.
关键词： pointing errors,Free Space Optical,log-normal atmospheric turbulence,single-input-multiple-output (SIMO),outage probability,M-ary amplitude shift keying modulation (M-ary ASK)
更新于2025-09-10 09:29:36
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Pointing errors effect on fiber coupling efficiency for Gaussian-beam wave through atmospheric turbulence channel in FSO links
摘要： In this paper, we theoretically study the pointing errors effect on fiber coupling efficiency for Gaussian-beam wave with consideration of atmospheric turbulence. A numerical expression of the average fiber coupling efficiency is derived based on mutual coherence function of Gaussian-beam wave and effective transmitter parameters. Numerical results show that the coupling efficiency can be evidently degraded by the pointing errors and pointing errors effect also changes optimum design parameter. And other factors, such as path length and the refractive index structure constant, are also analyzed. It is anticipated that this work is helpful to investigate pointing errors effect on optical wave propagation in the atmospheric turbulence.
关键词： Optical communications,Pointing errors,Free-space optical communications,Fiber coupling
更新于2025-09-09 09:28:46
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Impact of transmission techniques in asymmetric RF/FSO system over Nakagami- <i>m</i> and gamma-gamma fading channels with pointing errors
摘要： In this paper, the performance of transmission techniques on the fixed‐gain amplify‐and‐forward–based asymmetric radio frequency/free space optical (RF/FSO) communication system is studied. The RF link and FSO link are, respectively, modeled by the Nakagami‐m and Gamma‐Gamma fading channels under the effect of zero boresight and non‐zero boresight pointing errors subject to heterodyne detection. Maximum ratio transmission (MRT) and orthogonal space‐time block coding (OSTBC) techniques are the transmission scenarios considered at the system source while selection combining is used for reception at the relay and destination for the signal detection. Moreover, a unified cumulative density distribution (CDF) of end‐to‐end signal‐to‐noise ratio is derived for the system. By utilizing this channel statistical CDF, the closed‐form expressions for the outage probability and average bit error rate for the M‐ary phase shift keying modulation are then obtained for the system. The analysis presented illustrates that both the atmospheric turbulence and pointing error significantly degrade the system performance. Based on this, the MRT transmission technique offers a better performance compared with the OSTBC techniques under the same system conditions. The accuracy of the analytical results is verified by Monte‐Carlo simulations.
关键词： transmit diversity,free space optical,Nakagami‐m fading,pointing errors,atmospheric turbulence
更新于2025-09-09 09:28:46