Coverage Analysis of 5G Intelligent High-Speed Railway System Based on Beamwidth-Adaptive Free-Space Optical Communication
Abstract
1. Introduction
- We construct a model of an intelligent HSR system based on beamwidth-adaptive FSO communication with narrow-strip-shaped cells. In this model, the cell diameter and cell edge are defined, and two scenarios of transmitter beamwidth (i.e., wide beam and narrow beam) are considered. When the transmitter emits a wide beam, the channel gain includes geometric loss, atmospheric attenuation, and atmospheric turbulence. When the transmitter emits a narrow beam, the channel gain includes pointing error, atmospheric attenuation, and atmospheric turbulence.
- We propose a beamwidth-adaptive FSO communication system. By incorporating an additional transmitter controller and infrared emitter into the transmitter unit, as well as an additional receiver controller and infrared receiver into the receiver unit, the system is capable of adaptively managing the on or off state of the ATP module.
- We propose a beamwidth-adaptive method. During the handover process, the receiver controller assesses the beam width of the target transmitter by detecting the signal strength received from the target transmitter. In conjunction with the infrared emitter, infrared receiver, and transmitter controller, it adaptively controls the on or off state of the ATP modules in both the transmitter and receiver, thereby achieving dynamic alignment and tracking of the optical beams. Specifically, when the target transmitter emits a wide beam, the system keeps the ATP module off to conserve energy; when a narrow beam is transmitted, the ATP module is activated to ensure precise beam alignment between the transmitter and receiver.
- We analyze the coverage performance at the cell edge by studying the statistical characteristics of the received signal-to-noise ratio (SNR). Based on the definition of ECP and utilizing integral formulas of the Meijer’s G-function, closed-form expressions of ECP are derived for both the wide-beam and narrow-beam cases.
- We present the average coverage performance of the cells, which is characterized by the percentage of CCA. The closed-form expressions of the percentage of CCA for the cases of wide beams and narrow beams are derived by utilizing the mathematical definition, the integral formula of the Meijer’s G-function, and the composite trapezoidal integration approximation method.
- Numerical results are presented, showing good agreement between theoretical and simulation results, thereby validating the accuracy of the derived expressions. In addition, the effects of cell diameter, transmit power, SNR threshold, and weather visibility on coverage performance are analyzed.
2. System and Channel Models
2.1. System Model
2.2. Channel Model
2.2.1. Geometric Loss
2.2.2. Atmospheric Attenuation
2.2.3. Atmospheric Turbulence
2.2.4. Pointing Error
3. Proposed Beamwidth-Adaptive FSO Communication System and Method
3.1. Beamwidth-Adaptive System
3.2. Beamwidth-Adaptive Method
Algorithm 1 Beamwidth-adaptive Method |
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4. Coverage Performance Analysis
4.1. ECP Analysis
4.2. Percentage of CCA Analysis
5. Numerical Results
Algorithm 2 Monte-Carlo simulation method |
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5.1. Power Consumption Comparison
5.2. Results of ECP
5.3. Results of Percentage of CCA
6. Conclusions
- We propose a beamwidth-adaptive FSO communication system and a beamwidth-adaptive method. When the target transmitter emits a wide beam, the system keeps the ATP module off to conserve energy; when a narrow beam is transmitted, the ATP module is activated to ensure precise beam alignment between the transmitter and receiver. This method effectively enables the system to adaptively adjust the state of the ATP module based on the target transmitter’s width during receiver movement, utilizing handover detection and signal power threshold judgment, thereby enhancing communication reliability and energy efficiency.
- For the HSR system based on a beam-adaptive FSO communication system, closed-form expressions of the ECP and the percentage of CCA are derived. All theoretical results match well with simulations, demonstrating the accuracy of the derived expressions for performance evaluation without time-consuming simulations.
- The wide-beam system should be prioritized in small coverage scenarios to ensure coverage quality while saving energy consumption from ATP system activation. The narrow-beam configuration is preferred for large coverage scenarios to meet coverage performance requirements.
- The wide-beam systems perform better in low-power deployment scenarios due to their tolerance to alignment errors, ensuring better initial cell coverage. Narrow-beam systems excel in high-power scenarios, as their energy concentration enables more significant performance improvements with increasing power. System designers should select appropriate beam configurations based on power constraints to optimize the percentage of CCA.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
Abbreviations
5G-R | Fifth generation-railway |
ATP | Acquisition-tracking-pointing |
BSs | Base stations |
CCA | Cell coverage area |
ECP | Edge coverage probability |
FSO | Free-space optical |
GSM-R | Global system for mobile communication-railway |
HSR | High-speed railway |
LTE-R | Long term evolution-railway |
OOK | On-off keying |
Probability density function | |
RF | Radio frequency |
SNR | Signal-to-noise ratio |
Appendix A
Appendix B
Appendix C
Appendix D
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Parameters | Symbols | Values |
---|---|---|
Photoelectric conversion efficiency | R | 0.8 |
Receiver diameter | B | 0.2 m |
Divergence angle | 0.01 rad | |
Noise standard deviation | A/Hz | |
Beam wavelength | 850 nm | |
Effective number of large-scale cells | 3.99 | |
Amount of fading parameter | 2 | |
Average optical power of the classic scattering component received by off-axis eddies | 0.2 | |
Average optical power of the coherent contributions | 0.5 | |
Beam waist radius | ||
Number of sub-intervals in the composite trapezoidal integral | n | 1000 |
Number of Snapshots | N |
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Dong, S.; Zeng, Z.-Z.; Zhang, D.-T.; Sun, Z.-Q.; Wang, J.-Y. Coverage Analysis of 5G Intelligent High-Speed Railway System Based on Beamwidth-Adaptive Free-Space Optical Communication. Sensors 2025, 25, 4906. https://doi.org/10.3390/s25164906
Dong S, Zeng Z-Z, Zhang D-T, Sun Z-Q, Wang J-Y. Coverage Analysis of 5G Intelligent High-Speed Railway System Based on Beamwidth-Adaptive Free-Space Optical Communication. Sensors. 2025; 25(16):4906. https://doi.org/10.3390/s25164906
Chicago/Turabian StyleDong, Shuai, Zhi-Zhao Zeng, Dan-Ting Zhang, Zi-Qi Sun, and Jin-Yuan Wang. 2025. "Coverage Analysis of 5G Intelligent High-Speed Railway System Based on Beamwidth-Adaptive Free-Space Optical Communication" Sensors 25, no. 16: 4906. https://doi.org/10.3390/s25164906
APA StyleDong, S., Zeng, Z.-Z., Zhang, D.-T., Sun, Z.-Q., & Wang, J.-Y. (2025). Coverage Analysis of 5G Intelligent High-Speed Railway System Based on Beamwidth-Adaptive Free-Space Optical Communication. Sensors, 25(16), 4906. https://doi.org/10.3390/s25164906