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[IEEE 2018 Second International Conference on Electronics, Communication and Aerospace Technology (ICECA) - Coimbatore (2018.3.29-2018.3.31)] 2018 Second International Conference on Electronics, Communication and Aerospace Technology (ICECA) - FSO Link Performance Analysis with Different Modulation Techniques under Atmospheric Turbulence
摘要： Free space optics (FSO) has achieved prominence in extremely large bandwidth, unlicensed spectrum and low power secure transmission in the field of wireless communication. Despite the advantages, it is deeply impacted due to atmospheric turbulence and fog weather conditions. This paper considers different modulation schemes under the presence of atmospheric turbulence and fog conditions. The desired expression of bit error rate (BER) is obtained by modeling the turbulence as gamma-gamma distributed channel and under this channel condition, 16-PPM has provided better performance than other schemes. BER is considered for the channel performance evaluation. This analysis can help to adopt a modulation technique according to the channel condition.
关键词： Bit error rate (BER),gamma-gamma distribution,atmospheric turbulence,Free space optics (FSO),Meijer’s G function
更新于2025-09-23 15:21:21
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BER Performance Analysis of an Orthogonal FDM Free Space Optical Communication System with Homodyne Optical Receiver over Turbulent Atmospheric Channel
摘要： Atmospheric turbulence induced fading may severely impair free-space optical (FSO) communication systems, affecting the quality of the propagated laser beam and lead to significant performance degradation. Recent research works reveal that performance can be improved by using orthogonal FDM. In this paper, an analytical approach is presented to evaluate the bit error rate performance of an OFDM FSO link with optical intensity modulation and coherent homodyne receiver taking into consideration the effect of strong atmospheric turbulence. The turbulence effect is modeled as gamma-gamma distribution and the performance results are evaluated in terms of average CNR and BER. Power penalty suffered by the system due to the effect of turbulence at a given BER is evaluated for several system parameters viz. link distance, local oscillator turbulence parameter, power etc. It is noticed that effect of turbulence can be significantly reduced by increasing the number of OFDM subcarrier. For example, power penalty for BER of 10–9 at a link distance of 3,600 m is 6 dB when number of subcarrier is 4 and can be reduced to 0.5 dB by increasing the number of subcarrier to 64. In addition, by utilizing coherent optical receiver and synchronous demodulation at the receiving end, we have introduced local oscillator (LO) for both Optical and RF state which have ability to track the signal’s phase changes over time relative to the LO’s phase and helps the system to remain stable.
关键词： subcarrier multiplexer,carrier to noise ratio (CNR),coherent optical receiver,free space optical (FSO) communication,gamma-gamma distribution
更新于2025-09-23 15:21:01
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Exact distributions for bit error rate and channel capacity in free-space optical communication
摘要： Bit error rate (BER) and channel capacity are two important metrics to assess the performance of free-space optical communication (FSOC) systems. Due to the fading of the optical signal owing to the atmospheric effects, these two quantities behave as random variables. Most of the studies in this direction have focused on the calculation of only the average of these quantities. However, since the complete information about a random variable is encoded in its distribution, it is more informative to examine the latter itself. In this work, the authors derive exact probability density function (PDF) expressions for the BER and the channel capacity for an arbitrary irradiance model. In particular, they investigate these exact results for log-normal, gamma-gamma, and K distributions. For the BER analysis, they focus on the binary phase shift keying and quadrature phase shift keying modulation schemes. The authors' analytical reults are found to be in conformity with Monte Carlo simulations. The exact PDFs of the BER and the channel capacity reveal that there are several instances when the average is unable to capture the actual behaviour of these quantities, and therefore one must be careful in drawing conclusions based on the first moment only.
关键词： binary phase shift keying,bit error rate,quadrature phase shift keying,gamma-gamma distribution,channel capacity,log-normal distribution,K distribution,probability density function,free-space optical communication
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