Path Loss Model for 3.5 GHz and 5.6 GHz Bands in Cascaded Tunnel Environments

Area of Science:

• Electrical Engineering
• Radio Propagation
• Telecommunications

Background:

• Radio propagation in tunnels is critical for mobile communication systems.
• Cascaded straight and curved tunnel sections present unique challenges for signal transmission.

Purpose of the Study:

• To develop a joint path loss model for cascaded straight and curved tunnels.
• To characterize the impact of tunnel curvature on radio signal attenuation at 3.5 GHz and 5.6 GHz.

Main Methods:

• Combined waveguide mode theory and the shooting and bouncing ray (SBR) method.
• Utilized ray-tracing (RT) to derive an empirical formula for extra loss coefficient (ELC).
• Validated the model using simulation and measurement data.

Main Results:

• Tunnel curvature introduces additional signal loss, modeled as a linear function of distance.
• An empirical formula relating ELC to curvature radius was established for specific frequency bands.
• The proposed model demonstrates high accuracy and low complexity in predicting path loss.

Conclusions:

• The developed joint path loss model effectively predicts signal attenuation in complex tunnel environments.
• The model provides a valuable tool for optimizing wireless network design in railways and subways.
• Understanding curvature-induced loss is key to enhancing radio propagation predictability.