scholarly journals Analysis of signal quality in FSO systems with PolSK modulation

2020 ◽  
Vol 17 (2) ◽  
pp. 171-186
Author(s):  
Jelena Todorovic ◽  
Branimir Jaksic ◽  
Petar Spalevic ◽  
Djoko Bandjur ◽  
Milos Bandjur
Keyword(s):  
Signal To Noise Ratio ◽  
Free Space Optical ◽  
Link Distance ◽  
Negative Exponential Distribution ◽  
Shift Keying ◽  
Negative Exponential ◽  
Atmospheric Channel ◽  
Polsk Modulation ◽  
The Impact

In this paper, the quality of the Polarization Shift Keying (PolSK) modulated signal in a Free Space Optical (FSO) system is analyzed. The atmospheric channel is statistically modeled with four different distributions, namely, the Gamma-Gamma distribution, Negative Exponential distribution, Kdistribution, and I-K distribution. For all four channel models, the Average Bit Error Rate (ABER) at the receiving side of the system is determined in an analytically closed form. The results are graphically presented and discussed in order to determine the impact of certain parameters on the ABER, i.e., the quality of the received signal in the PolSK modulated FSO system. These parameters are the Signal-to-Noise Ratio (SNR), the FSO link distance, the wavelength at which the signal is transmitted, and the atmospheric turbulence strength.

scholarly journals Effect of Atmospheric Turbulences on BPSK

2021 ◽  
Vol 10 (5) ◽  
pp. 353-357
Author(s):  
Priyanka Bhardwaj ◽  
Aadi Jain ◽  
Manveen . ◽  
Richita Kamal ◽  
Rishab Chittlangia
Keyword(s):  
Open Space ◽  
Signal To Noise Ratio ◽  
Modulation Scheme ◽  
Free Space Optical ◽  
Air Turbulence ◽  
And Performance ◽  
Log Normal ◽  
Negative Exponential ◽  
The Impact ◽  
Bpsk Modulation

FSO (Free-Space Optical Communications) is a type of optical communication that is transmitted over an open space. The irradiance fluctuation in a clear atmosphere is caused by Temperature variations in the atmosphere are minor but erratic. As a result, the Signal-to-Noise Ratio (SNR) is reduced, and performance is reduced. BPSK has the best performance when scintillation is not considered. Thus, BPSK is investigated in this work under the impact of air turbulence and meteorological variables. The comparison of BPSK modulation scheme is done by simulating turbulence in Log Normal and Negative Exponential Channel.

scholarly journals BER analysis of amplify-and-forward relaying FSO systems using APD receiver over strong atmospheric turbulence channels

2019 ◽  
Vol 9 (5) ◽  
pp. 3678
Author(s):  
Duong Huu Ai ◽  
Van Loi Nguyen
Keyword(s):  
Atmospheric Turbulence ◽  
Closed Form Expression ◽  
Free Space Optical ◽  
Amplify And Forward ◽  
Transmission Distance ◽  
Link Distance ◽  
Optimal Value ◽  
Atmospheric Loss ◽  
The Impact ◽  
Relay Stations

<span lang="EN-US">In this paper, we theoretically analyze the performance of amplify-and-forward (AF) serial relaying free-space optical (FSO) systems using avalanche photodiodes (APD) and subcarrier quadrature amplitude modulation (SC-QAM) over strong atmospheric turbulence channels modelled by gamma-gamma distribution. Closed-form expression for average bit error rate (BER) of system is theoretically derived talking into account APD shot noise, thermal noise as well as the impact of atmospheric loss and turbulence. The numerical results show that using AF relay stations can extend the transmission distance and help to improve performance of FSO system significantly when compared with the direct transmission. Moreover, the selection of APD gain value is indispensable to the system performance. The proposed system could be achieved the best performance by selecting an optimal APD gain value. In addition, the optimal value of APD gain also significantly depends on various conditions, such as link distance, the number of relay stations and APD receiver noise.</span>

scholarly journals Improving Image Transmission by Using Polar Codes and Successive Cancellation List Decoding

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Álvaro Garcia ◽  
Maria De Lourdes Melo Guedes Alcoforado ◽  
Francisco Madeiro ◽  
Valdemar Cardoso Da Rocha Jr.
Keyword(s):  
Signal To Noise Ratio ◽  
Additive White Gaussian Noise ◽  
Structural Similarity ◽  
Image Transmission ◽  
Polar Codes ◽  
Code Construction ◽  
Successive Cancellation ◽  
Natural Choice ◽  
Shift Keying

This paper investigates the transmission of grey scale images encoded with polar codes and de-coded with successive cancellation list (SCL) decoders in the presence of additive white Gaussian noise. Po-lar codes seem a natural choice for this application be-cause of their error-correction efficiency combined with fast decoding. Computer simulations are carried out for evaluating the influence of different code block lengths in the quality of the decoded images. At the encoder a default polar code construction is used in combination with binary phase shift keying modulation. The results are compared with those obtained by using the clas-sic successive cancellation (SC) decoding introduced by Arikan. The quality of the reconstructed images is assessed by using peak signal to noise ratio (PSNR) and the structural similarity (SSIM) index. Curves of PSNR and SSIM versus code block length are presented il-lustrating the improvement in performance of SCL in comparison with SC.

scholarly journals Classroom acoustics: Listening problems in children

2019 ◽  
Vol 27 (1) ◽  
pp. 47-59 ◽  
Author(s):  
Flavia Gheller ◽  
Elisa Lovo ◽  
Athena Arsie ◽  
Roberto Bovo
Keyword(s):  
Auditory Processing ◽  
Signal To Noise Ratio ◽  
Cognitive Effort ◽  
Listening Skills ◽  
Noisy Environments ◽  
Acoustic Characteristics ◽  
Classroom Acoustics ◽  
Acoustic Quality ◽  
The Impact

The acoustic quality of classrooms is crucial for children’s listening skills and consequently for their learning. Listening abilities in kids are still developing, and an environment with inadequate acoustic characteristics may create additional problems in speech perception and phonetic recognition. Background noise or reverberation may cause auditory processing problems and greater cognitive effort. There are also other elements which can make difficulty in listening and understanding in noisy environments an even more serious problem, such as learning disabilities, mild to severe hearing loss or bilingualism. Therefore, it is important to improve the acoustic quality of the classrooms, taking into account the specific needs of children in terms of signal-to-noise ratio and reverberation time, in order to ensure a proper quality of listening. The aim of this work is to analyse, through the review of previous studies, the impact that the acoustic of classrooms has on children’s listening skills and learning activities.

scholarly journals Travel Time Model of Left-Turning Vehicles at Signalized Intersection

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Leng Jun-qiang ◽  
Feng Yu-qin ◽  
Zhai Jing ◽  
Bao Lei ◽  
He Yi
Keyword(s):  
Travel Time ◽  
Flow Rate ◽  
Signalized Intersection ◽  
Time Model ◽  
Through Flow ◽  
Negative Exponential Distribution ◽  
The Common ◽  
Queue Theory ◽  
Negative Exponential ◽  
The Impact

The travel time of left-turning vehicles at signalized intersection was discussed. Under the assumption that the opposing through vehicles headway follows M3 distribution, the travel time model was established on the basis of gap theory and queue theory. Comparison was done with the common model based on the assumption that the opposing through vehicles headway follows negative exponential distribution. The results show that the model in this paper has stronger applicability and its most relative error is less than 15%. In addition, the sensitivity analysis was done. The results show that the opposing through flow rate has significant impact on travel time. The impact of left-turning flow rate and following headway is light when the opposing through flow rate is small, the threshold is about 0.18 veh/s. The model established in this paper can well calculate travel time of left-turning vehicles at intersection, and the methodology may provide reference to other occasions.

scholarly journals Impact of pointing error on SISO/MISO drones swarm-based free space optical system in weak turbulence regime

2021 ◽  
Vol 23 (2) ◽  
pp. 918
Author(s):  
Abdullah Jameel Mahdi ◽  
Wamidh Jalil Mazher ◽  
Osman Nuri Ucan
Keyword(s):  
Free Space ◽  
Communication Systems ◽  
High Performance ◽  
Signal To Noise Ratio ◽  
Weather Conditions ◽  
Free Space Optical ◽  
Single Input Single Output ◽  
Pointing Error ◽  
Single Output ◽  
Link Distance

<p>Applying the drone-based free space optical (FSO) technology is recent in communication systems. The FSO technology hashigh-security features dueto narrow beamwidth, insusceptible to interferences, free license and landline connection is not appropriate. However, these advantages face many obstacles that affect the system's performance, such as random weather conditions and misalignment. The pointing error Hpis one of the critical factors of the channel gain H. The related parameters of the Hp factor: the pointing error angles θr and the path length Z, were manipulated to extract the applicable values at various receiver diameter values. The proposed system has two topologies: single input single output (SISO) and multiple input single output (MISO), flying in weak atmospheric turbulence. The simulation was done using MATLAB software 2020. The average bit error rate (ABER) for the system versus signal-to-noise ratio (SNR) were verified and analyzed. The results showed that at θr=10<sup>−3</sup>rad, Z increased in the range 10~100m for each one-centimeter increase of DR. At θr=10<sup>−2</sup>rad, the applicable Z was nearly 10% of the link distance Z when θr=10<sup>−3</sup>rad was applied. Consequently, an increase in θr must correspond decrease in Z and vice versa to maintain the system at high performance.</p>

scholarly journals Performance Evaluation of FSO Communications under Sand-Dust Conditions

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Minghua Cao ◽  
Huiqin Wang ◽  
Yu Yao ◽  
Shanglin Hou
Keyword(s):  
Weather Conditions ◽  
Superior Performance ◽  
Dust Particles ◽  
Signal Pulse ◽  
Free Space Optical ◽  
Pulse Delay ◽  
Negative Exponential Distribution ◽  
Dust Weather ◽  
The Impact ◽  
Sand Dust

Sand-dust weather conditions are considered the primary challenge to free-space optical (FSO) communications. It may cause severe attenuation that is malignant to FSO link performance. This study investigates the impact of sand-dust particles on a laser signal using the radiation propagation method and the small-angle approximation method. Numerical simulation shows that in sand-dust weather conditions, the multiple scattering effect is dominant and results in signal pulse delay and pulse broadening. Furthermore, the signal attenuation follows a negative exponential distribution to the laser wavelength. Superior performance can be achieved by employing a longer wavelength laser to reduce pulse delay and mutual interference.

Statistical evaluation of the performance of free-space-optical link affected by optical turbulence with gamma-gamma distribution through time series generated by simulation

2021 ◽  
Vol 67 (1 Jan-Feb) ◽  
pp. 146
Author(s):  
J. A. Lopez-Leyva ◽  
A. Arvizu-Mondragon ◽  
J. Santos-Aguilar ◽  
F. J. Mendieta-Jimenez
Keyword(s):  
Time Series ◽  
Gamma Distribution ◽  
Statistical Evaluation ◽  
Signal To Noise Ratio ◽  
Optical Power ◽  
Practical Implementation ◽  
Free Space Optical ◽  
Optical Turbulence ◽  
The Mean ◽  
The Impact

In this article, the statistical evaluation of the performance of FSO links subject to dynamic fluctuations of atmospheric optical turbulence that affect the instantaneous value of the received optical power is presented. We reproduce this temporal domain effect with time series generated by simulation considering the optical turbulence as a stochastic process with Gamma-Gamma probability distribution. Also, a phase screen was used in order to observe the impact that optical turbulence has over the optical information field's spatial phase. With our simulations, it is possible to get the two most essential performance parameters required for the practical implementation of FSO links. We obtained the mean signal-to-noise ratio (SNR) and the mean bit error rate (BER) of FSO links affected by optical turbulence with Gamma-Gamma distribution.  The methodology presented in this paper may be readily used to design and implement real-world FSO links.

Analysis of the impact of measurement matrices in compressive sensing for medical images

2020 ◽  
pp. 591-600
Author(s):  
G. Kowsalya ◽  
H. A. Christinal ◽  
D. A. Chandy ◽  
S. Jebasingh ◽  
C. Bajaj
Keyword(s):  
Compressive Sensing ◽  
Sparse Representation ◽  
Medical Images ◽  
Signal To Noise Ratio ◽  
Basis Pursuit ◽  
Measurement Matrix ◽  
Compressed Images ◽  
The Impact ◽  
Reconstruction Time

Compressive sensing of images is based on three key components namely sparse representation, construction of measurement matrix and reconstruction of images. The visual quality of reconstructed image is prime important in medical images. We apply Discrete Cosine Transform (DCT) for sparse representation of medical images. This paper focuses on the analysis of measurement matrices on compressive sensing of MRI images. In this work, the Gaussian and Bernoulli type of random matrices are considered as measurement matrix. The compressed images are reconstructed using Basis Pursuit algorithm. Peak-signal-to noise ratio and reconstruction time are the metrics taken for evaluating the performance of measurement matrices towards compressive sensing of medical images.

Performance analysis of free space optical system incorporating circular polarization shift keying and mode division multiplexing

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Meenu ◽  
Anshu Sharma ◽  
Rahul Malhotra
Keyword(s):  
Circular Polarization ◽  
Free Space ◽  
Heavy Rain ◽  
Weather Conditions ◽  
Detailed Comparison ◽  
Free Space Optical ◽  
Light Rain ◽  
Link Distance ◽  
Mode Division Multiplexing ◽  
Shift Keying

Abstract In this work, a free-space optical (FSO) communication system with the integration of mode division multiplexing and circular polarization shift keying (CpolSK) is proposed at 2 × 40 Gbps using LG00 and LG01 modes. Effects of diverse weather conditions such as clear weather, light rain, moderate rain, heavy rain, thin fog, thick fog, and heavy fog are studied on system performance. Further, a detailed comparison of CpolSK and polarization shift keying (PolSK) is performed at different FSO lengths in terms of log bit error rate. For implementation, analysis, and comparison, Optiwave Optisystem software is used and results show that CpolSK covers 100 km link distance and PolSK limits to 90 km only. Also, LG00 mode performs better than LG01 mode under all weather instabilities in the proposed system.

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