# Performance Analysis of UAV-Assisted Hybrid FSO/RF Communication Systems under Various Weather Conditions

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## Abstract

**:**

## 1. Introduction

#### 1.1. Related Works

#### 1.2. Motivation and Contributions

- To our knowledge, we, firstly, propose a multi-hop parallel hybrid FSO/RF communication system architecture with and without PE based on the UAV relay.
- New mathematical expressions for the end-to-end system in terms of average bit error rate and outage probability are derived under EW turbulence and Nakagami fading channels for four binary subcarrier modulation schemes.
- The effects of different weather environments, modulation methods, receiver apertures, RF fading parameters, pointing errors, and relay structures on the performance of our considered systems are analyzed through numerical evaluationnumerical simulations. As far as we know, no existing work considered the impact of weather environments and aperture averaging on UAV-assisted FSO communication.

## 2. System and Channel Models

#### 2.1. One-Hop FSO SublinkSubsystem under Various Weather Conditions

#### 2.2. One-Hop RF SublinkSubsystem under Various Weather Conditions

#### 2.3. One-Hop Hybrid FS0/RF System Based on a Selective Combination Scheme

## 3. System Performance Analysis

#### 3.1. Average Bit Error Rate

#### 3.2. Outage Probability

## 4. Numerical Results

## 5. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 2.**The relationship between BER performance and transmitted powertransmission of the hybrid FSO/RF direct link without PE under different weather conditions and modulation schemes. (

**a**) Clear air. (

**b**) Haze. (

**c**) Light fog. (

**d**) Light rain.

**Figure 3.**The relationship between the BER performance and transmittedtransmission power of hybrid FSO/RF direct links without PE. (

**a**) ${m}_{x,y}=1$$m=1$. (

**b**) ${m}_{x,y}=2$m = 2.

**Figure 4.**The relationship between the BER performance and transmittedtransmission power of UAV-assisted hybrid systems and the hybrid direct link without PE. (

**a**) ${m}_{x,y}=1$$m=1$. (

**b**) ${D}_{x,y}=10$ cm.

**Figure 5.**The relationship between outage probability and transmittedtransmission power of hybrid FSO/RF direct links without PE. (

**a**) ${m}_{x,y}=1$$m=1$. (

**b**) ${m}_{x,y}=2$$m=2$.

**Figure 6.**The relationship between outage probability and transmittedtransmission power of UAV-assisted hybrid systems and hybrid FSO/RF direct links without PE. (

**a**) ${m}_{x,y}=1$$m=1$. (

**b**) ${D}_{x,y}=10$ cm.

**Figure 7.**The relationship between BER performance and transmitted power of the hybrid FSO/RF direct links and UAV-assisted hybrid systems with PE under different parameters. (

**a**) Different weather. (

**b**) Different ${m}_{x,y}$. (

**c**) Different ${D}_{x,y}$. (

**d**) Different ${\sigma}_{x,y}^{s}$.

**Figure 8.**The relationship between outage probability and transmitted power of UAV-assisted hybrid systems and hybrid FSO/RF direct links with PE. (

**a**) Different ${D}_{x,y}$. (

**b**) Different ${\sigma}_{x,y}^{s}$.

Weather Condition | ${\mathit{C}}_{\mathit{n}}^{2}$ [${\mathbf{m}}^{-2/3}$] | ${\mathit{\omega}}_{\mathit{x},\mathit{y}}^{\mathit{FSO}}$ [dB/Km] | ${\mathit{\omega}}_{\mathit{x},\mathit{y}}^{\mathit{Rain}}$ [dB/Km] | ${\mathit{\omega}}_{\mathit{x},\mathit{y}}^{\mathit{Oxg}}$ [dB/Km] |
---|---|---|---|---|

Clear air | $5\times {10}^{-14}$ | $0.43$ | 0 | 15.1 |

Haze | $1.7\times {10}^{-14}$ | $4.2$ | 0 | 15.1 |

Light fog | $3\times {10}^{-15}$ | $7.7$ | 0 | 15.1 |

light rain ($2.5$ mm/h) | $6\times {10}^{-15}$ | $1.98$ | $1.50$ | 15.1 |

Binary Modulation Scheme | p | q |
---|---|---|

Coherent binary phase shift keying (CBPSK) | $0.5$ | 1 |

Differential binary phase shift keying (DBPSK) | 1 | 1 |

Coherent binary frequency shift keying(CBFSK) | $0.5$ | $0.5$ |

Non-coherent binary frequency shift keying (NBFSK)(NBPSK) | 1 | $0.5$ |

FSO Subsystem | RF Subsystem | ||
---|---|---|---|

Parameters | Value | Parameters | Value |

Wavelength, ${\lambda}_{x,y}^{FSO}$ | 1550 nm | Wavelength of 60 GHz RF, ${\lambda}_{x,y}^{RF}$ | 5 mm |

Divergence angle, ${\theta}_{x,y}$ | 1 mrad | Nakagami fading parameter, ${m}_{x,y}$ | 2 |

Receiver aperture diameter, ${D}_{x,y}$ | 10 cm or 20 cm | Transmit antenna gain, ${G}_{x,y}^{t}$ | 44 dBi |

Responsivity, ${R}_{x,y}^{FSO}$ | $0.5$ A/W | Receive antenna gain, ${G}_{x,y}^{r}$ | 44 dBi |

Noise Variance, ${\left({\sigma}_{x,y}^{FSO}\right)}^{2}$ | ${10}^{-14}{\mathrm{A}}^{2}/\mathrm{Hz}$ | Noise Variance, ${\left({\sigma}_{x,y}^{RF}\right)}^{2}$ | $-85$ dBm |

Transmission distance, ${L}_{x,y}$ | 1 km | Oxygen attenuation, ${\omega}_{x,y}^{oxg}$ | $15.1$ dB/km |

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**MDPI and ACS Style**

Wu, Y.; Kong, D.; Wang, Q.; Li, G.
Performance Analysis of UAV-Assisted Hybrid FSO/RF Communication Systems under Various Weather Conditions. *Sensors* **2023**, *23*, 7638.
https://doi.org/10.3390/s23177638

**AMA Style**

Wu Y, Kong D, Wang Q, Li G.
Performance Analysis of UAV-Assisted Hybrid FSO/RF Communication Systems under Various Weather Conditions. *Sensors*. 2023; 23(17):7638.
https://doi.org/10.3390/s23177638

**Chicago/Turabian Style**

Wu, Yan, Dejin Kong, Qian Wang, and Gang Li.
2023. "Performance Analysis of UAV-Assisted Hybrid FSO/RF Communication Systems under Various Weather Conditions" *Sensors* 23, no. 17: 7638.
https://doi.org/10.3390/s23177638