scholarly journals Analytical approach of an FSO Link with alamouti- type STBC considering weak atmospheric turbulence

2018 ◽  
Vol 53 (3) ◽  
pp. 205-210
Author(s):  
MS Islam ◽  
M Morshed ◽  
RC Roy ◽  
MHA Begum
Keyword(s):  
Fading Channels ◽  
Atmospheric Turbulence ◽  
Analytical Approach ◽  
Direct Detection ◽  
Maximal Ratio Combining ◽  
Free Space Optical ◽  
Hardware Complexity ◽  
Receiver Diversity ◽  
Log Normal ◽  
Ber Performance

An analytical approach is proposed to evaluate the bit error rate (BER) performance of a direct detection on-off keying (OOK) free space optical link over log-normal atmospheric turbulence-induced fading channels based on modified Alamouti code presented by Simon and Vilnrotter and maximal ratio combining (MRC) at the receiver. Simulations show that due to coding and diversity at the receiver, a significant improvement in the BER performance is obtained at a given BER. For diversity order of 2 in both transmitter and in receiver, the amount of BER improvement is 6.6dB at BER 10-5. Further increment of the receiver diversity from 2 to 4 gives additional 3dB improvement at the same BER. A drastic improvement of the BER performance is also possible for increasing number of receiver diversity which may increase hardware complexity. Simulation results are demonstrated to confirm the analytical results.Bangladesh J. Sci. Ind. Res.53(3), 205-210, 2018

Performance Analysis of a Multiple Subcarrier Modulated FSO Communication System using Direct Detection Optical Receiver under the Effect of Weak Atmospheric Turbulence

2020 ◽  
Vol 41 (4) ◽  
pp. 453-461
Author(s):  
Bobby Barua ◽  
S. P. Majumder
Keyword(s):  
Atmospheric Turbulence ◽  
Direct Detection ◽  
Optical Receiver ◽  
Closed Form Expression ◽  
Free Space Optical ◽  
Power Penalty ◽  
Link Distance ◽  
Distance Data ◽  
Channel Analysis ◽  
Log Normal

AbstractIn this paper, an analytical approach is presented to evaluate the bit error rate (BER) of a free space optical (FSO) link with radio frequency (RF) multiple subcarrier modulation, taking into account the effect of weak atmospheric turbulence considering a direct detection optical receiver followed by RF synchronous demodulator for each sub-channel. Analysis is carried out to find a closed-form expression for conditional BER at the output of the RF demodulators conditioned on a given value of atmospheric turbulence-induced fading and intermodulation distortion (IMD). The average BER for each sub-channel is then found by averaging the conditional BER over the probability density function of the atmospheric turbulence modeled as log-normal distribution. Degradations of BER due to atmospheric turbulence are evaluated for several values of system parameters like number of RF subcarrier, turbulence variance, link distance, data rate and power penalty suffered by the system due to atmospheric turbulence and IMD. For a given system bandwidth, it is found that the maximum power penalty occurs when the subcarrier number is around four and the performance gradually improves with increase in the number of subcarrier. For example, at a system bandwidth of 20 GHz with subcarrier number 4, the power penalty at a BER of 10–9 is found to be 30 dB for a link distance of 3.6 km, whereas the power penalty reduces to 13 dB when the number of subcarrier is increased to 32.

scholarly journals Adaptive selective relaying in cooperative free-space optical systems over atmospheric turbulence and misalignment fading channels

2014 ◽  
Vol 22 (13) ◽  
pp. 16629 ◽  
Author(s):  
Rubén Boluda-Ruiz ◽  
Antonio García-Zambrana ◽  
Carmen Castillo-Vázquez ◽  
Beatriz Castillo-Vázquez
Keyword(s):  
Fading Channels ◽  
Atmospheric Turbulence ◽  
Free Space ◽  
Optical Systems ◽  
Free Space Optical ◽  
Space Optical Systems

Performance Comparison of Free-Space Optical (FSO) Communication Link Under OOK, BPSK, DPSK, QPSK and 8-PSK Modulation Formats in the Presence of Strong Atmospheric Turbulence

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
A. K. M. Sharoar Jahan Choyon ◽  
Ruhin Chowdhury
Keyword(s):  
Phase Shift ◽  
Atmospheric Turbulence ◽  
Free Space ◽  
Communication Systems ◽  
Communication Link ◽  
Phase Shift Keying ◽  
Free Space Optical ◽  
Modulation Formats ◽  
Shift Keying ◽  
Ber Performance

AbstractFree-space optical (FSO) communication system provides several advantages over radio frequency (RF) system offering high bandwidth, low cost, small space requirements and more secure transmission which is free from Electromagnetic Interference (EMI). However, when the transmitted light signal passes through the atmosphere it experiences attenuation and fluctuations due to atmospheric turbulence. This paper analyzes the bit error rate (BER) performance of FSO communication systems under strong atmospheric turbulence for on-off keying (OOK), binary phase-shift keying (BPSK), differential phase shift keying (DPSK), quadrature phase shift keying (QPSK) and 8-phase shift keying (8-PSK) for link distances of 500, 1,000, 1,500 and 2,000 m. The probability density function (pdf) of the received irradiance is modelled using the gamma-gamma distribution model. It is found that the system exhibits the best BER performance and compensates the lowest power penalty at BER of 10 - 9 for BPSK modulation compared with other modulation techniques which makes BPSK more appropriate to be used with FSO turbulent system.

Effect of Pointing Error on BER Performance of a Multi-wavelength OCDMA FSO System with SIK Dual Detector Receiver

2019 ◽  
Vol 40 (3) ◽  
pp. 247-253
Author(s):  
A. K. M. Nazrul Islam ◽  
S. P. Majumder
Keyword(s):  
Standard Deviation ◽  
Direct Detection ◽  
Code Length ◽  
Free Space Optical ◽  
Pointing Error ◽  
Multi Wavelength ◽  
Dual Detector ◽  
Multi Access ◽  
Code Division Multiple ◽  
Ber Performance

Abstract A novel analytical approach is presented to evaluate the bit error rate (BER) performance of a multi-wavelength optical code division multiple access (MW-OCDMA) free space optical (FSO) system using optical domain encoder and sequence inverse keying (SIK) balanced photodetector direct detection receiver taking the effect of pointing errors into considerations. The analysis is carried out to find the expression for the signal, multi-access interference (MAI) and crosstalk at the output of the SIK receiver in presence of pointing error. The BER performance results are evaluated for different values of standard deviation of pointing error, code length, number of simultaneous user and other system parameters. It is found that, MW-OCDMA system offers improved BER performance over single wavelength OCDMA FSO system. However, the performance of an MW-OCDMA system is degraded due to the effect of pointing error between the laser transmitter and optical receiver and the system suffers significant power penalty at a given BER of 10−9. The penalty is found to be 11.0 dB, 24.0 dB and 30 dB for jitter standard deviation of 1.3, 1.8 and 2.5 respectively when code length is 512 and number of user is 8 for number of wavelength 8. Further, the penalty can be greatly reduced by increasing the code length for a given number of user and number of wavelength.

scholarly journals Performance Analysis of RIS-Assisted FSO Communications over Fisher–Snedecor F Turbulence Channels

2021 ◽  
Vol 11 (21) ◽  
pp. 10149
Author(s):  
Caslav Stefanovic ◽  
Máximo Morales-Céspedes ◽  
Ana García Armada
Keyword(s):  
Fading Channels ◽  
Direct Detection ◽  
Signal To Noise Ratio ◽  
Moment Generating Function ◽  
Cumulative Distribution ◽  
Model Parameters ◽  
Free Space Optical ◽  
F Distribution ◽  
The Moment ◽  
Analytical Expressions

The Fisher–Snedecor (F-S) F distribution has recently been introduced as a tractable turbulence-induced (TI) fading model that fits well with the experimental data. This paper provides a performance evaluation of a free-space optical (FSO) re-configurable intelligent surface (RIS)-assisted communications (ACs) link over the F-S F TI fading channels, assuming the intensity modulation–direct detection (IM–DD) technique. In particular, novel and closed-form (C-F) analytical expressions for the probability density function (PDF) and cumulative distribution function (CDF) of the end-to-end signal-to-noise ratio (SNR) in terms of Gaussian hyper-geometric functions are efficiently derived. Capitalizing on the obtained results, novel C-F analytical expressions for the moment generating function (MMGF), outage probability (OP), average bit error rate (BER) and ergodic channel capacity (Cγ) of the FSO RIS-ACs system over the F-S F TI fading channels are provided and numerically evaluated under the various TI fading severity conditions. Furthermore, the second-order (S-O) statistical expressions for the level crossing rate (LCR) and average fade duration (AFD) are obtained and thoroughly examined for various FSO RIS-ACs system model parameters.

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