On the End-to-End Performance of a Mixed RF-FSO link with a Decode-and-Forward Relay

2019 ◽  
Vol 40 (3) ◽  
pp. 323-332 ◽  
Author(s):  
Himanshu Khanna ◽  
Mona Aggarwal ◽  
Swaran Ahuja
Keyword(s):  
Atmospheric Turbulence ◽  
Error Rate ◽  
Path Loss ◽  
Symbol Error Rate ◽  
Free Space Optical ◽  
Short Term ◽  
Decode And Forward ◽  
Pointing Error ◽  
The Impact

Abstract In this paper, we investigate the performance of a decode-and-forward relayed mixed radio frequency-free space optical (RF-FSO) dual-hop link. The transmitter to receiver link’s first-hop is a RF channel and the second-hop is a FSO channel. The RF link experiences long-term shadowing and short-term multi-path fading effects, while the FSO channel suffers atmospheric turbulence fading, path loss, and pointing error-induced misalignment fading. The performance of the system is analyzed considering the impact of these parameters. We model the RF link by generalized-K fading distribution and the atmospheric turbulence over the FSO link by the gamma–gamma fading. The expressions in closed form for the outage probability, symbol error rate for the system employing $q$-ary PSK modulation schemes, and the channel capacity of the system are derived. The obtained numerical results are also depicted by numerical plots.

Performance Analysis of Amplify-and-Forward Relaying FSO/SC-QAM Systems over Weak Turbulence Channels and Pointing Error Impairments

2017 ◽  
Vol 39 (1) ◽  
Author(s):  
Ha Duyen Trung
Keyword(s):  
Atmospheric Turbulence ◽  
Communication Systems ◽  
Symbol Error Rate ◽  
Aperture Size ◽  
Free Space Optical ◽  
Amplify And Forward ◽  
Pointing Error ◽  
Log Normal ◽  
The Impact ◽  
Af Relaying

AbstractIn this paper, the end-to-end performance of free-space optical (FSO) communication system combining with Amplify-and-Forward (AF)-assisted or fixed-gain relaying technology using subcarrier quadrature amplitude modulation (SC-QAM) over weak atmospheric turbulence channels modeled by log-normal distribution with pointing error impairments is studied. More specifically, unlike previous studies on AF relaying FSO communication systems without pointing error effects; the pointing error effect is studied by taking into account the influence of beamwidth, aperture size and jitter variance. In addition, a combination of these models to analyze the combined effect of atmospheric turbulence and pointing error to AF relaying FSO/SC-QAM systems is used. Finally, an analytical expression is derived to evaluate the average symbol error rate (ASER) performance of such systems. The numerical results show that the impact of pointing error on the performance of AF relaying FSO/SC-QAM systems and how we use proper values of aperture size and beamwidth to improve the performance of such systems. Some analytical results are confirmed by Monte-Carlo simulations.

Performance Analysis of Reconfigurable Intelligent Surface in a Dual-Hop DF Relay Empowered Asymmetric RF/FSO Networks

2021 ◽  
Author(s):  
Kehinde O Odeyemi ◽  
Pius A. Owolawi ◽  
Oladayo O. Olakanmi
Keyword(s):  
Performance Analysis ◽  
Closed Form ◽  
Atmospheric Turbulence ◽  
Performance Metrics ◽  
Beam Width ◽  
High Signal ◽  
Free Space Optical ◽  
Decode And Forward ◽  
Pointing Errors ◽  
The Impact

Abstract In this paper, the performance analysis of a reconfigurable intelligent surface (RIS) in a dual-hop decode-and-forward (DF) relay empowered asymmetric radio frequency (RF)/free space optical (FSO) systems is presented. The RIS-assisted RF network is subjected to Nakagami-m distribution while the RIS-assisted FSO networks experience Gamma-Gamma distribution in which both atmospheric turbulence and pointing errors are considered. Thus, the closed-form expressions for the system outage probability and average bit error rate (ABER) are derived with limited number of reflecting elements at RIS-assisted RF network and multiple number of reflecting elements at RIS-assisted FSO network. Further, to obtain more insight about the system characteristic, the asymptotic closed-form expressions are derived at high signal-to-noise ratio (SNR) for the system performance metrics. The results illustrate the impact of the system and channel parameters on the proposed system in terms of atmospheric turbulence, pointing errors under beam width condition, m-fading parameter, and number of reflecting elements. The correctness of the derived analytical expressions is validated via the Monte-Carlo simulations.

Error performance analysis of optical communication over Lognormal-Rician turbulence channel using Gram-Charlier Series

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Maoke Miao ◽  
Xiaofeng Li
Keyword(s):  
Error Rate ◽  
Symbol Error Rate ◽  
High Signal ◽  
Free Space Optical ◽  
Error Performance ◽  
Maximum Ratio Combining ◽  
Rate Analysis ◽  
De Algorithm ◽  
Shift Keying ◽  
The Impact

Abstract In this paper, the symbol-error rate (SER) performance of a coherent free-space optical (FSO) communication system in lognormal-Rician turbulence channel is analyzed using the generalized Gram-Charlier (GCC) series. We proposed the differential evolution (DE) algorithm to solve the parameters in GCC efficiently. It is shown that highly accurate closed-form SER expressions are obtained for M-ary phase-shift keying (MPSK) and M-ary quadrature amplitude modulation (MQAM) schemes with maximum ratio combining (MRC) technique. The asymptotic error rate analysis is presented to reveal the performance behavior in the high signal-to-noise (SNR) regime. The effects of imperfect phase noise compensation on the error rate performance are also studied, and it is found that the impact of phase compensation error can be small enough with loop SNR ρ c more than seven.

Performance Analysis of FSO DF Relays with Log-Normal Fading Channel

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
Ha Duyen Trung
Keyword(s):  
Performance Analysis ◽  
Error Rate ◽  
Communication Systems ◽  
Free Space Optical ◽  
Error Performance ◽  
Relay Nodes ◽  
Decode And Forward ◽  
Log Normal ◽  
Optimal Average ◽  
The Impact

AbstractThis paper studies the bit error performance analysis of decode-and-forward (DF) relays-based free-space optical (FSO) communication systems using avalanche photodiode (APD). The system uses subcarrier intensity binary phase shift keying (BPSK) modulated signals and subjects to scintillation due to optical turbulence. A log-normal random process is considered to model the received signal intensity fluctuation for a clear-air condition (weak atmospheric turbulence) scenario. Mathematical expressions of the average bit error probability and bit error rate (BER) are derived by taking into account the impact of atmospheric loss, thermal-noise and shot-noise limited conditions. It can be inferred from the numerical results that using DF relay nodes can extend the transmission distance and minimize BER performance of FSO system significantly compared with the direct transmission. Moreover, the selection of APD’s gain values is essential to minimize the system’s error rate performance. Therefore, the system could achieve the minimal BER by selecting an optimal average APD gain value appropriately. Moreover, the optimal average gain values of APD significantly depend on various conditions, such as the bit rate, total transmitted power, and the number of relay nodes.

scholarly journals Partial Relay Selection for Two-Way Mixed RF/FSO DF Networks in the Presence of I/Q Imbalance

2021 ◽  
Author(s):  
Shweta Mittal ◽  
Pankaj Yadav ◽  
vivek dwivedi
Keyword(s):  
Outage Probability ◽  
Atmospheric Turbulence ◽  
Relay Selection ◽  
Research Work ◽  
Free Space Optical ◽  
Elementary Functions ◽  
Asymptotic Results ◽  
Decode And Forward ◽  
Partial Relay Selection ◽  
The Impact

Abstract In this paper, the study of mixed radio frequency (RF)/ free space optical (FSO) communication decode and forward (DF) two way relaying (TWR) has been presented. In fact, it has been considered that multiple relays are present out of which the best operational relay is selected as per the partial relay selection (PRS) methodology in the presence of outdated channel state information (CSI). Importantly, the relay nodes are assumed to operate in the presence of in phase (I) quadrature phase (Q) imbalance (IQI). The atmospheric turbulence on the FSO link has been modeled using the Malaga distribution with pointing errors. In addition to this, the impact of type of optical demodulation has been considered in the analysis. For the system model, outage probability expression has been derived in terms of Meijer-G and Fox’s H-functions. In addition to this, for the TWR system, the outage probability expressions have been modified to present asymptotic results in terms of elementary functions. The numerical analysis of the research work suggests that the overall mixed RF/FSO DF TWR system is impacted by the image rejection ratio (IRR) due to IQI, correlation between outdated CSI, atmospheric turbulence, pointing error and type of optical demodulation in addition to the amount of fading on the RF link.

SUMBER-SUMBER RESILIENSI PADA REMAJA AKHIR YANG MENGALAMI KEKERASAN DARI ORANGTUA PADA MASA KANAK-KANAK

Psibernetika ◽  
2018 ◽  
Vol 11 (1) ◽  
Author(s):  
Devina Calista ◽  
Garvin Garvin
Keyword(s):  
Late Adolescents ◽  
Long Term Effects ◽  
Short Term ◽  
Parental Affection ◽  
Resilience Factors ◽  
Childhood Violence ◽  
Past Experiences ◽  
The Impact ◽  
Depth Interviews

<p><em>Child abuse by parents is common in households. The impact of violence on children will bring short-term effects and long-term effects that can be attributed to their various emotional, behavioral and social problems in the future; especially in late adolescence that will enter adulthood. Resilience factors increase the likelihood that adolescents who are victims of childhood violence recover from their past experiences</em><em>,</em><em> become more powerful individuals and have a better life. The purpose of this study was to determine the source of resilience in late adolescents who experienced violence from parents in their childhood. This research uses qualitative research methods with in-depth interviews as a method of data collection. The result shows that the three research participants have the aspects of "I Have", "I Am", and "I Can"; a participant has "I Can" aspects as a source of resilience, and one other subject has no source of resilience. The study concluded that parental affection and acceptance of the past experience have role to the three sources of resilience (I Have, I Am, and I Can)</em></p><p><em> </em></p><p><strong><em>Keyword : </em></strong><em>Resilience, adolescence, violence, parents</em></p>

Forecasting Revenue Impacts from COVID-19: The Case of Florida Municipalities

2021 ◽  
pp. 0160323X2110120
Author(s):  
Hai (David) Guo ◽  
Can Chen
Keyword(s):  
Local Government ◽  
Short Term ◽  
Fiscal Planning ◽  
Revenue Structure ◽  
Municipal Managers ◽  
The Impact

Early in the pandemic, Florida municipal managers indicated that forecasting the impact on local revenues was one of their top priorities in responding to the pandemic, yet such a tool has not been widely available. This study offers simple and straightforward fiscal planning guides for assessing the short-term and long-term impacts of the COVID 19 recession on local government revenues by estimating the revenue declines among 411 Florida municipalities from FY 2021 to FY 2023. The forecast results predict revenues will be reduced by $5.11 billion from 2019 pre-pandemic levels for Florida cities in fiscal years 2021 through 2023. The decline is forecast to be 3.54 percent in FY 2021, 4.02 percent in FY 2022, and 3.29 percent in FY 2023. The revenue structure matters for estimating the revenue decline.

scholarly journals Paleolithic Diet—Effect on the Health Status and Performance of Athletes?

Nutrients ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 1019
Author(s):  
Barbara Frączek ◽  
Aleksandra Pięta ◽  
Adrian Burda ◽  
Paulina Mazur-Kurach ◽  
Florentyna Tyrała
Keyword(s):  
Blood Pressure ◽  
Body Mass ◽  
Positive Impact ◽  
Model Assessment ◽  
Paleolithic Diet ◽  
Short Term ◽  
Positive Effects ◽  
Short And Long Term ◽  
The Impact

The aim of this meta-analysis was to review the impact of a Paleolithic diet (PD) on selected health indicators (body composition, lipid profile, blood pressure, and carbohydrate metabolism) in the short and long term of nutrition intervention in healthy and unhealthy adults. A systematic review of randomized controlled trials of 21 full-text original human studies was conducted. Both the PD and a variety of healthy diets (control diets (CDs)) caused reduction in anthropometric parameters, both in the short and long term. For many indicators, such as weight (body mass (BM)), body mass index (BMI), and waist circumference (WC), impact was stronger and especially found in the short term. All diets caused a decrease in total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and triglycerides (TG), albeit the impact of PD was stronger. Among long-term studies, only PD cased a decline in TC and LDL-C. Impact on blood pressure was observed mainly in the short term. PD caused a decrease in fasting plasma (fP) glucose, fP insulin, and homeostasis model assessment of insulin resistance (HOMA-IR) and glycated hemoglobin (HbA1c) in the short run, contrary to CD. In the long term, only PD caused a decrease in fP glucose and fP insulin. Lower positive impact of PD on performance was observed in the group without exercise. Positive effects of the PD on health and the lack of experiments among professional athletes require longer-term interventions to determine the effect of the Paleo diet on athletic performance.

Methods to Reduce Traffic Speed in High-Pedestrian Rural Areas

2003 ◽  
Vol 1828 (1) ◽  
pp. 31-37 ◽  
Author(s):  
Ali Kamyab ◽  
Steve Andrle ◽  
Dennis Kroeger ◽  
David S. Heyer
Keyword(s):  
Rural Areas ◽  
Speed Limit ◽  
Single Word ◽  
Short Term ◽  
Speed Reduction ◽  
Traffic Calming ◽  
Reduction Strategies ◽  
Long Term Impact ◽  
The Impact

Many Minnesota counties are faced with the problem of high vehicle speeds through towns or resort areas that have significant pedestrian traffic. The impact of speed reduction strategies in high-pedestrian areas in rural counties of Minnesota was investigated. Speed data were collected at two selected study sites under their existing conditions ("no-treatment" or "before" condition) and after the proposed speed reduction strategies were installed. Second "after" data conditions were collected to study the short-term and long-term impact of the implemented strategies. The traffic-calming techniques employed at the Twin Lakes site consisted of removable pedestrian islands and pedestrian crossing signs. A dynamic variable message sign that sent a single-word message ("Slow") to motorists traveling over the speed limit was installed at the Bemidji site. The research study shows that the traffic-calming strategy deployed in Twin Lakes was effective in significantly reducing the mean speed and improving speed limit compliance in both the short term and long term. Despite proven effectiveness, the deployed speed reduction treatment in Bemidji Lake failed to lower the speed at the study site. The single-word message on the sign and the location of the sign, as well as a lack of initial enforcement, were the primary reasons for such failure.

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