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The average bit error rate (BER) for binary phase-shift keying (BPSK) modulation in free-space optical (FSO) links over turbulence atmosphere modeled by the exponentiated Weibull (EW) distribution is investigated in detail. The effects of aperture averaging on the average BERs for BPSK modulation under weak-to-strong turbulence conditions are studi...
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In [1] the authors look at a new Hyperbolic Sine-Weibull (HSW) family of distributions with cdf. of type M (t; a, β, λ) = 2e a (e a − 1) 2 cosh a 1 − e −λt β − 1 where t > 0, a > 0, β > 0, λ > 0. The authors illustrated that this distribution provides a better fit to real data sets that Weibull, Hyperbolic Sine Exponential and other distributions....
The turbulence in the channel will increase the bit error rate of the FSO system, which can resist the influence of atmospheric turbulence in many ways. In this paper, spatial pulse position modulation (SPPM) is combined with Polar code to improve error performance. The influence of list length on the decoding performance of CRC-SCL and the perform...
In this study, we consider two dual-hop FSO systems with decode-and-forward protocol. The FSO system is assumed to be equipped with RF link used as a backup in case the FSO link experiences strong atmospheric turbulence or pointing errors. The two system models differ by the setup of the RF link. A single-hop RF backup link is used for the first sy...
We conduct a research on free space optical (FSO) communication system that is applied for transmission in wireless sensor networks (WSN), which is based on the hybrid pulse position modulationbinary phase shift keying-subcarrier intensity modulation (PPM-BPSK-SIM) undergoes novel Exponentiated Weibull fading channels. When battery-charged sensor t...
![Parameter of FSO and RF sub-systems [3], [4]](profile/Shubha-Sharma-2/publication/335744000/figure/tbl1/AS:801925746417672@1568205405326/Parameter-of-FSO-and-RF-sub-systems-3-4_Q320.jpg)
The performance of a free space optics (FSO) transmission suffers from the atmospheric turbulence and the attenuation in foggy environment. By employing relay nodes, the error rate and the coverage area of the FSO communication system can be significantly improved. However, the pointing errors, generated because of the building sway, have the poten...
Citations
... Free-space optical communication system is a prominent technology for the future broadband optical networks because of its huge bandwidth capacity, required no license, high data rate, easy to deployment, simple hardware architecture, low cost and full duplex communication (Wang et al. 2014;Vincent 2006;Chinta et al. 2009;Chao et al. 2021). Nowadays, high speed FSO communication system is considered for inter satellite data transmission link where pointing error due to misalignment causes severe performance degradation Ebrahim et al. 2022). ...
In this research article, we investigate the impact of different atmospheric turbulence along with polarization crosstalk on the bit error rate (BER) performance of a non-Hermitian orthogonal frequency division modulated (OFDM) free-space optical (FSO) system with polarization diversity. Analysis is carried out for a non-Hermitian coherent optical OFDM followed by differential quadrature phase shift keying FSO system with polarization diversity in presence of atmospheric turbulence for all weather conditions. We considered Log-normal, Gamma-Gamma and Negative exponential turbulence fading model for weak, medium and strong atmospheric turbulent channel respectively and for cross polarization induced crosstalk, the random misalignment angle is Maxwellian distributed. The system average BER is calculated by averaging the conditional BER over the probability density function of the channel irradiance along with Maxwellian distributed random misalignment angle. Results are evaluated in terms of BER, power penalty due to polarization crosstalk along with atmospheric turbulence and receiver sensitivity due to OFDM. Results show that the system suffers almost 7.5, 11 and 16 dB power penalty due to polarization crosstalk along with weak, medium and strong turbulence respectively at a constant BER of 10–12 when the system link length is 3000 m. It is clearly observed that, almost 19, 16 and 10 dB receiver sensitivity is achieved when number of subcarriers increase into 512 for weak, medium and strong turbulence conditions, respectively at a constant BER of 10–12.
... During the last two decades, free space optical (FSO) communication systems have been getting research interests due to unlicensed frequency spectrum, very high data rate and ease of connectivity (Wang et al. 2014;Vincent 2006;Chinta et al. 2009;Chao et al. 2021). Nowadays, FSO is widely used for both short distance and long distance communication such as radio-frequency wireless near ground which is short-distance connections and in satellite communications which is long distance communication (Wang et al. 2014). ...
... During the last two decades, free space optical (FSO) communication systems have been getting research interests due to unlicensed frequency spectrum, very high data rate and ease of connectivity (Wang et al. 2014;Vincent 2006;Chinta et al. 2009;Chao et al. 2021). Nowadays, FSO is widely used for both short distance and long distance communication such as radio-frequency wireless near ground which is short-distance connections and in satellite communications which is long distance communication (Wang et al. 2014). Spatial diversity is a very attractive technique to mitigate fading due to atmospheric turbulence of the received signal. ...
In this paper, we proposed an analytical model for a non-Hermitian orthogonal frequency division modulation system considering space time block coding (STBC) with polarization diversity in presence of strong atmospheric turbulence and compare the bit error rate (BER) performance with the same system considering space frequency block coding (SFBC). We developed this analytical model to calculate the impact of crosstalk and fading on system performance due to cross polarization and strong atmospheric turbulence respectively. The analytical expressions for signal to noise plus crosstalk ratio are derived for a certain amount of random misalignment angle. We consider two different independent probability density functions one is Maxwellian distribution and another is Gamma-Gamma distribution for angular misalignment and strong turbulence respectively. The average BER is found by averaging the conditional BER over this two probability density functions. It is noticed that, receiver sensitivity improvement due to STBC coding is almost 4.5 dB at a BER of 10–12 compare to 7.5 dB due to SFBC coding reported earlier by the authors. From the analytical results, we clearly found that SFBC coding performs better than STBC coding for the same system’s constraints. Finally, results of our proposed work are verified with others earlier published results and it is found that our result is almost 2 dB better than the published results.
... Thus, we have selected an EW model in the present study due to its ability to incorporate aperture averaging of intensity fluctuations, in addition to its usefulness in efficiently representing the irradiance fluctuations over all turbulence conditions. The PDF of the turbulence-induced intensity fluctuations using the EW model is given by [46][47][48] ...
Free-space optical (FSO) communication systems employ unguided light beams propagating through the atmosphere to carry a large volume of data. The reliability of such data transfer can be hampered by various atmospheric effects. Based on an analytical model of a differential phase-shift keying FSO system through exponentiated Weibull turbulence, we investigate the effectiveness of beam width optimization and improved beam alignment, along with aperture averaging on the average channel capacity. Our results show significant signal deterioration produced due to the aerosol-induced optical turbulence, which substantially shadows the performance gain achieved through beam width optimization. Strong aerosol-induced atmospheric heating and the consequent enhanced optical scintillations result in reduction of the channel capacity by as much as 50% of its value when these effects are not considered or negligible. FSO systems are more resilient to aerosol-induced optical turbulence when the normalized beam width is less, and the average channel capacity can be significantly improved by improved beam alignment. These variations are weakly dependent under poor transmitter–receiver alignment conditions. Furthermore, the receiver aperture has a strong control on the link performance. While FSO systems with higher magnitude of normalized beam width have improved performance under all aperture diameter conditions; for a given beam configuration, large aperture diameter ensures a significant improvement in the link performance due to reduction in effects of scintillations.
... In [6,7], the BER performance of an OOK modulation system under the condition of atmospheric turbulence, which is based on EW model with and without pointing error, has been researched. In [8,9], the BER and outage probability for various binary modulation schemes of the FSO communication system, which is based on EW model with and without the misalignment errors, have been studied. In [10], the advantages and disadvantages of FSO communication as well as various turbulence channel models have been discussed. ...
... The empirical formulas of these three parameters have been given in [20]. Similar to [6,8], this paper adopts the three parameter values obtained by experiments in [19] to analyze the performance of OOK modulation, because these values are more accurate than those obtained from the empirical formulas. ...
... where ( ) and ( ) are additive white Gaussian noise (AWGN) with the variance 2 , which is used to model the thermal noise and the background radiation [11,16,17]. The down converted signal is represented as [16] ( ) = ( ) ( ) + ( ). ...
... As a result, the in-phase and quadrature phase can be the orthogonal resources of TDD. In addition, a single SIM with TDD which uses in-phase and quadrature phase of a subcarrier as a dual branch could be beneficial considering that the previous study of TDD has concluded that the most efficient TDD is obtained with dual branch of orthogonal resources [13,17]. Fig. 1 illustrates the concept of a single SIM with TDD. ...
A single subcarrier intensity modulation (SIM) with time delay diversity (TDD) is proposed to mitigate atmospheric turbulence-induced fading in satellite optical communications. As the scintillation causes signal to fade randomly, time delay longer than the channel correlation time is used on the orthogonal phase of the subcarrier to avoid the signal totally fading. In order not to have the adaptive threshold, the maximum order of phase-shift keying (PSK) in SIM is QPSK. Therefore, it can be applied to TDD by separating QPSK into BPSK. Simulations are conducted under the atmospheric channel, which is modeled based on the Kolmogorov power-law spectrum and Taylor frozen hypotheses. The simulation results demonstrate that the in-phase and quadrature phase of the subcarrier can be adopted as the orthogonal resources in TDD scheme.
... Free-space optical (FSO) communication is an emerging technology for broadband wireless optical communication system because of its high bandwidth, spectrum without licensed, high bit rates, with very high transmission security and low hardware cost [1][2][3]. Recently, FSO is widely considered as an alternate technology for near-ground radio-frequency wireless short-range connections and also considered for long-distance communication, such as satellite communications [1]. ...
... Free-space optical (FSO) communication is an emerging technology for broadband wireless optical communication system because of its high bandwidth, spectrum without licensed, high bit rates, with very high transmission security and low hardware cost [1][2][3]. Recently, FSO is widely considered as an alternate technology for near-ground radio-frequency wireless short-range connections and also considered for long-distance communication, such as satellite communications [1]. Atmospheric turbulence provides distortion in signal intensity, and cross-polarization induces crosstalk in the received signal which severely limits the performance of a FSO communication system and also degrades the bit error rate performance significantly [4][5][6][7][8]. ...
Polarization division multiplexing (PDM) is a promising technique to increase the capacity of future free-space optical (FSO) system due to availability of optical PDM multiplexer/demultiplexer. However, there are limitations due to cross-polarization-induced crosstalk and atmospheric turbulence. A novel analytical model of a DQPSK PDM FSO link is analyzed in this paper to determine the deterioration in error rate performance considering the cross-polarization-induced crosstalk in the presence of atmospheric turbulence. A closed-form expression for signal-to-crosstalk plus noise ratio and bit error rate conditioned on a given turbulence-induced fading and a given angular misalignment due to cross-polarization at the output of optical PDM DQPSK receiver is derived. By averaging the conditional BER, the average BER is found over the probability density function of the turbulence considering a log-normal distribution and random angular misalignment which is considered to have a Maxwellian distribution. The results are given in terms of BER and system power penalty because of cross-polarization-induced crosstalk with the effect of weak atmospheric turbulence. It is noticed that system BER performance degrades significantly and power penalty is found to almost 8.2 dB, 9.2 dB and 12 dB for mean misalignment angle of 4°, 5° and 6°, respectively, at a BER of 10−10 and a given turbulence parameter C2n
= 10−14m−2/3. Finally, our analytical work is verified with others earlier published work.
... To do so, we substitute t = γ β 2 in (18), and apply the identity (19) in each term of the summation in (18) to get (16). To derive (17), we use (15) in (6) and the inequality log 2 (1+γ) ≥ log 2 (γ): (20) To solve the above integral, we use the following identity: ...
Optical wireless communication (OWC) is highly vulnerable to the atmospheric turbulence and pointing error. Performance analysis of the OWC system under the combined channel effects of pointing errors and atmospheric turbulence is desirable for its efficient deployment. The widely used Gamma- Gamma statistical model for atmospheric turbulence, which consists of Bessel function, generally leads to complicated analytical expressions. In this paper, we consider the three-parameter exponentiated Weibull model for the atmospheric turbulence to analyze the ergodic rate and average signal-to-noise ratio (SNR) performance of a single-link OWC system. We derive simplified analytical expressions on the performance under the combined effect of atmospheric turbulence and pointing errors in terms of system parameters. We also derive approximate expressions on the performance under the atmospheric turbulence by considering negligible pointing error. In order to evaluate the performance at high SNR, we also develop asymptotic bounds on the average SNR and ergodic rate for the considered system. We demonstrate the tightness of derived expressions through numerical and simulation analysis along with a comparison to the performance obtained using the Gamma-Gamma model.
... As mentioned above, BPSK, as a simple and low BER modulation method, has been widely concerned in WSN system. Reference [38] studied the performance of BPSK, and we take it as a comparative basis. The newly proposed PPM-BPSK-SIM combines two traditional modulation methods, PPM and BPSK-SIM. ...
We conduct a research on free space optical (FSO) communication system that is applied for transmission in wireless sensor networks (WSN), which is based on the hybrid pulse position modulationbinary phase shift keying-subcarrier intensity modulation (PPM-BPSK-SIM) undergoes novel Exponentiated Weibull fading channels. When battery-charged sensor transmission nodes with limited energy is transmitted, it is vital to study the performance of the transmission link. We have derived the exact joint probability function of the transmission link when the atmospheric turbulence and pointing errors are considering. On the basis of them, the unconditional average bit error rate (BER) for hybrid PPM-BPSK-SIM is derived, then the closed expression of the outage probability and the average channel capacity are also derived. Research results indicates that increasing the receiver aperture by aperture averaging effect can distinctly improve the performance of the link. Additionally, for any circumstances of atmospheric turbulence and pointing errors, by combining the utilization of hybrid PPM-BPSK-SIM modulation and symbol with average length greater than eight, the average BER performance can be conspicuously enhanced. The outage probability and average channel capacity of the FSO link are jointly affected by atmospheric turbulence and pointing error, and optimization strategies in different scenarios are given by our research.
... An effective modulation scheme, which may be an alternative to the conventional techniques for mitigating turbulence, i.e. aperture averaging, spatial diversity, coding and beam shaping, can mitigate the effect of scintillation. In this respect, pulse position modulation (PPM) and phase shift keying (PSK) subcarrier intensity modulation (SIM) are examined, in both weak and strong atmospheric turbulence and employing the scintillation reduction techniques [11][12][13][14][15][16][17][18][19][20][21]. ...
... where δ 0 represents the simple anisotropic factor δ 0 = (µ x µ y ) 1/2 . The simple analytical form of ρ 0 is expressed by substituting the anisotropic oceanic spectrum Φ n (κ x , κ y , 0) into equation (14), and thus the lateral coherence length of the spherical wave in the anisotropic turbulent ocean is derived as [40][41][42] By substituting the source field u (s) into equation (13) and simplifying, we obtain the average received intensity, which is also found in [43], as ...
... We note that equations (14) and (15) are not derived from the revised (or asymptotic) Rytov theory [37] but are obtained directly from [40][41][42]. In our analysis of strong turbulence, it is appropriate to use the expressions of equations (14) and (15) in evaluating the average received intensity given by equation (16) because the average received intensity, being a second-order moment, is well known to be already valid in strong turbulence [37]. ...
... During MC simulation, a total of 10 8 random variable trials were used to reduce the statistical uncertainties of the OP, ABER and EC. The parameters ( , , , , , ) used in the analytical calculation and MC simulation are selected from [16] and [33,34] respectively. The i is chosen to be 30 in computing the generalized Gauss-Laguerre quadrature numerical integral method and the same average SNR per hop are assumed (i.e., , = , = ). ...
In this paper, we investigate the performance of decode-and-forward dual-hop mixed RF/FSO system in fifth-generation (5G) cloud radio access network. To describe the 5G channel characteristics properly, we assume that the RF link follows κ−μ shadowed fading which has been recently proposed to model small-scale multipath fading as well as line-of-sight (LOS) shadowing. For the FSO link, we adopt the Exponentiated Weibull distribution which can represent irradiance fluctuations at the finite receiving aperture over a wide range of turbulence conditions. We first derive the cumulative distribution function in terms of Meijer's G function, and then use it to obtain the analytical expressions of the outage probability, average bit error rate and ergodic capacity. The system performances are analyzed with different κ−μ shadowed fading parameters, turbulence strength and receiver aperture sizes. The analytical results show an accurate match to the Monte-Carlo simulation.
