On the Design of Rate Adaptation for Relay-Assisted Satellite Hybrid FSO/RF Systems

<p>This paper addresses the design of hybrid free-space optical/radio frequency (FSO/RF) systems for a high-altitude platform (HAP)-aided relaying satellite communication for mobile networks supported by unmanned aerial vehicle (UAV). While prior work primarily focused on fixed-rate design, which frequently switches between FSO and RF lead to reduce the system performance, we propose a rate adaptation design that gradually adjusts the data rate in each link when its channel state fluctuates. The proposed design's downlink performance is analyzed, taking into account many challenging issues, including beam spreading loss, cloud attenuation, statistical behaviors of the atmospheric turbulence in the dual-hop channel, and pointing misalignment due to the UAV hovering. Different performance metrics are analytically derived based on channel modelings, such as outage probability, average transmission rate, achievable spectrum efficiency, and average transmission rate. The numerical results quantitatively confirm the effectiveness of our proposed system under the impact of UAV hovering misalignment and atmospheric-related issues like clouds and turbulence. Finally, Monte-Carlo simulations validate the accuracy of theoretical results.</p>

On the Design of Rate Adaptation for Relay-Assisted Satellite Hybrid FSO/RF Systems

10.36227/techrxiv.15177573 ◽

2021 ◽

Author(s):

Hoang Le ◽

Thang Nguyen

Keyword(s):

Satellite Communication ◽

Performance Metrics ◽

Transmission Rate ◽

Rate Adaptation ◽

Spectrum Efficiency ◽

Free Space Optical ◽

Fixed Rate ◽

Rf Systems ◽

Average Transmission ◽

<p>This paper addresses the design of hybrid free-space optical/radio frequency (FSO/RF) systems for a high-altitude platform (HAP)-aided relaying satellite communication for mobile networks supported by unmanned aerial vehicle (UAV). While prior work primarily focused on fixed-rate design, which frequently switches between FSO and RF lead to reduce the system performance, we propose a rate adaptation design that gradually adjusts the data rate in each link when its channel state fluctuates. The proposed design's downlink performance is analyzed, taking into account many challenging issues, including beam spreading loss, cloud attenuation, statistical behaviors of the atmospheric turbulence in the dual-hop channel, and pointing misalignment due to the UAV hovering. Different performance metrics are analytically derived based on channel modelings, such as outage probability, average transmission rate, achievable spectrum efficiency, and average transmission rate. The numerical results quantitatively confirm the effectiveness of our proposed system under the impact of UAV hovering misalignment and atmospheric-related issues like clouds and turbulence. Finally, Monte-Carlo simulations validate the accuracy of theoretical results.</p>

Average Transmission Rate and Outage Performance of Relay-Assisted Satellite Hybrid FSO/RF Systems

10.36227/techrxiv.14971587 ◽

2021 ◽

Author(s):

Thang Nguyen

Keyword(s):

Monte Carlo ◽

Monte Carlo Simulations ◽

Free Space ◽

System Performance ◽

Performance Metrics ◽

Transmission Rate ◽

Free Space Optical ◽

Fixed Rate ◽

Rf Systems ◽

<div> <div> <div> <p>This paper proposes a rate adaptation design for high altitude platform (HAP)-aided relaying satellite hybrid free-space optical/radio-frequency (FSO/RF) systems. The design allows switching between two links gradually to reduce the fre- quent link switching in error-prone environments of conventional fixed-rate hybrid FSO/RF systems. System performance metrics, including average transmission rate and outage probability, are analytically studied under the presence of clouds and fading of FSO and RF channels modeled respectively by Gamma-Gamma and Rician distributions. The numerical results quantitatively highlight the effectiveness of our proposed systems over the conventional ones. Moreover, Monte-Carlo simulations are also performed to validate the accuracy of the analytical model. </p> </div> </div> </div>

Average Transmission Rate and Outage Performance of Relay-Assisted Satellite Hybrid FSO/RF Systems

10.36227/techrxiv.14971587.v1 ◽

2021 ◽

Author(s):

Thang Nguyen

Keyword(s):

Monte Carlo ◽

Monte Carlo Simulations ◽

Free Space ◽

System Performance ◽

Performance Metrics ◽

Transmission Rate ◽

Free Space Optical ◽

Fixed Rate ◽

Rf Systems ◽

<div> <div> <div> <p>This paper proposes a rate adaptation design for high altitude platform (HAP)-aided relaying satellite hybrid free-space optical/radio-frequency (FSO/RF) systems. The design allows switching between two links gradually to reduce the fre- quent link switching in error-prone environments of conventional fixed-rate hybrid FSO/RF systems. System performance metrics, including average transmission rate and outage probability, are analytically studied under the presence of clouds and fading of FSO and RF channels modeled respectively by Gamma-Gamma and Rician distributions. The numerical results quantitatively highlight the effectiveness of our proposed systems over the conventional ones. Moreover, Monte-Carlo simulations are also performed to validate the accuracy of the analytical model. </p> </div> </div> </div>

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

10.21203/rs.3.rs-610003/v1 ◽

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 ◽

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.

The Impact of Rate Adaptation Algorithms on Wi-Fi-Based Factory Automation Systems

Sensors ◽

10.3390/s20185195 ◽

2020 ◽

Vol 20 (18) ◽

pp. 5195

Author(s):

Tommaso Fedullo ◽

Federico Tramarin ◽

Stefano Vitturi

Keyword(s):

Real Time ◽

Communication Systems ◽

Transmission Rate ◽

Rate Adaptation ◽

Experimental Session ◽

Specific Rate ◽

Factory Automation ◽

Automation Systems ◽

Execution Times ◽

Factory automation systems based on the IEEE 802.11 Wi-Fi standard may benefit from its Multi-Rate Support (MRS) feature, which allows for dynamically selecting the most suitable transmission rate for the targeted application context. The MRS is implemented by means of rate adaptation algorithms (RAAs), which has already demonstrated to be effective to improve both timeliness and reliability, which are typically strict requirements of industrial real-time communication systems. Indeed, some of such algorithms have been specifically conceived for reliable real-time communications. However, the computational complexity of such algorithms has not been effectively investigated yet. In this paper, we address such an issue, particularly focusing on the execution times of some specific rate adaptation algorithms, as well as on their impact on the automation tasks. In this respect, after a formal description of the algorithms, we present the outcomes of an extensive experimental session, which includes practical measurements and realistic simulations. The obtained results are encouraging, since the measured execution times indicate that rate adaptation algorithms can be profitably adopted by industrial automation systems, allowing for improving their reliability and timeliness without impacting on the overall performance.

Average Transmission Rate and Outage Performance of Relay-Assisted Satellite Hybrid FSO/RF Systems

10.1109/atc52653.2021.9598287 ◽

2021 ◽

Author(s):

Thang V. Nguyen ◽

Hoang D. Le ◽

Ngoc T. Dang ◽

Anh T. Pham

Keyword(s):

Transmission Rate ◽

Outage Performance ◽

Rf Systems ◽

Recent Advances in Electrical & Electronic Engineering (Formerly Recent Patents on Electrical & Electronic Engineering) ◽

An Effective Congestion Control Algorithm based on Traffic Assignment and Reassignment in Wireless Sensor Network

10.2174/2352096513999200628095848 ◽

2020 ◽

Vol 13 (8) ◽

pp. 1166-1174

Author(s):

Chao Wang

Keyword(s):

Wireless Sensor Network ◽

Congestion Control ◽

Sensor Network ◽

Traffic Assignment ◽

Transmission Rate ◽

Sensor Nodes ◽

Wireless Sensor ◽

Congestion Detection ◽

Detection Technology ◽

Background: It is important to improve the quality of service by using congestion detection technology to find the potential congestion as early as possible in wireless sensor network. Methods: So an improved congestion control scheme based on traffic assignment and reassignment algorithm is proposed for congestion avoidance, detection and mitigation. The congestion area of the network is detected by predicting and setting threshold. When the congestion occurs, sensor nodes can be recovery quickly from congestion by adopting reasonable method of traffic reassignment. And the method can ensure the data in the congestion areas can be transferred to noncongestion areas as soon as possible. Results: The simulation results indicate that the proposed scheme can reduce the number of loss packets, improve the throughput, stabilize the average transmission rate of source node and reduce the end-to-end delay. Conclusion: : So the proposed scheme can enhance the overall performance of the network. Keywords: wireless sensor network; congestion control; congestion detection; congestion mitigation; traffic assignment; traffic reassignment.

Estimating asymptomatic, undetected and total cases for the COVID-19 outbreak in Wuhan: a mathematical modeling study

BMC Infectious Diseases ◽

10.1186/s12879-021-06078-8 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Xi Huo ◽

Jing Chen ◽

Shigui Ruan

Keyword(s):

Disease Transmission ◽

Large Scale ◽

Transmission Rate ◽

Control Strategies ◽

Herd Immunity ◽

Antibody Prevalence ◽

Screening Process ◽

Vaccination Programs ◽

Prevalence Level ◽

Abstract Background The COVID-19 outbreak in Wuhan started in December 2019 and was under control by the end of March 2020 with a total of 50,006 confirmed cases by the implementation of a series of nonpharmaceutical interventions (NPIs) including unprecedented lockdown of the city. This study analyzes the complete outbreak data from Wuhan, assesses the impact of these public health interventions, and estimates the asymptomatic, undetected and total cases for the COVID-19 outbreak in Wuhan. Methods By taking different stages of the outbreak into account, we developed a time-dependent compartmental model to describe the dynamics of disease transmission and case detection and reporting. Model coefficients were parameterized by using the reported cases and following key events and escalated control strategies. Then the model was used to calibrate the complete outbreak data by using the Monte Carlo Markov Chain (MCMC) method. Finally we used the model to estimate asymptomatic and undetected cases and approximate the overall antibody prevalence level. Results We found that the transmission rate between Jan 24 and Feb 1, 2020, was twice as large as that before the lockdown on Jan 23 and 67.6% (95% CI [0.584,0.759]) of detectable infections occurred during this period. Based on the reported estimates that around 20% of infections were asymptomatic and their transmission ability was about 70% of symptomatic ones, we estimated that there were about 14,448 asymptomatic and undetected cases (95% CI [12,364,23,254]), which yields an estimate of a total of 64,454 infected cases (95% CI [62,370,73,260]), and the overall antibody prevalence level in the population of Wuhan was 0.745% (95% CI [0.693%,0.814%]) by March 31, 2020. Conclusions We conclude that the control of the COVID-19 outbreak in Wuhan was achieved via the enforcement of a combination of multiple NPIs: the lockdown on Jan 23, the stay-at-home order on Feb 2, the massive isolation of all symptomatic individuals via newly constructed special shelter hospitals on Feb 6, and the large scale screening process on Feb 18. Our results indicate that the population in Wuhan is far away from establishing herd immunity and provide insights for other affected countries and regions in designing control strategies and planing vaccination programs.

Impact of public health interventions to curb SARS-CoV-2 spread assessed by an evidence-educated Delphi panel and tailored SEIR model

Journal of Public Health ◽

10.1007/s10389-021-01566-2 ◽

2021 ◽

Author(s):

Bernd Brüggenjürgen ◽

Hans-Peter Stricker ◽

Lilian Krist ◽

Miriam Ortiz ◽

Thomas Reinhold ◽

...

Keyword(s):

Public Health ◽

Transmission Rate ◽

Latency Period ◽

Policy Decision ◽

Sensitivity Analyses ◽

Delphi Panel ◽

Time Step ◽

Seir Model ◽

Health Policy Decision ◽

Abstract Aim To use a Delphi-panel-based assessment of the effectiveness of different non-pharmaceutical interventions (NPI) in order to retrospectively approximate and to prospectively predict the SARS-CoV-2 pandemic progression via a SEIR model (susceptible, exposed, infectious, removed). Methods We applied an evidence-educated Delphi-panel approach to elicit the impact of NPIs on the SARS-CoV-2 transmission rate R0 in Germany. Effectiveness was defined as the product of efficacy and compliance. A discrete, deterministic SEIR model with time step of 1 day, a latency period of 1.8 days, duration of infectiousness of 5 days, and a share of the total population of 15% assumed to be protected by immunity was developed in order to estimate the impact of selected NPI measures on the course of the pandemic. The model was populated with the Delphi-panel results and varied in sensitivity analyses. Results Efficacy and compliance estimates for the three most effective NPIs were as follows: test and isolate 49% (efficacy)/78% (compliance), keeping distance 42%/74%, personal protection masks (cloth masks or other face masks) 33%/79%. Applying all NPI effectiveness estimates to the SEIR model resulted in a valid replication of reported occurrence of the German SARS-CoV-2 pandemic. A combination of four NPIs at consented compliance rates might curb the CoViD-19 pandemic. Conclusion Employing an evidence-educated Delphi-panel approach can support SARS-CoV-2 modelling. Future curbing scenarios require a combination of NPIs. A Delphi-panel-based NPI assessment and modelling might support public health policy decision making by informing sequence and number of needed public health measures.