Modeling of the Division Point of Different Propagation Mechanisms in the Near-Region Within Arched Tunnels

Abstract

An accurate characterization of the near-region propagation of radio waves inside tunnels is of practical importance for the design and planning of advanced communication systems. However, there has been no consensus yet on the propagation mechanism in this region. Some authors claim that the propagation mechanism follows the free space model, others intend to interpret it by the multi-mode waveguide model. This paper clarifies the situation in the near-region of arched tunnels by analytical modeling of the division point between the two propagation mechanisms. The procedure is based on the combination of the propagation theory and the three-dimensional solid geometry. Three groups of measurements are employed to verify the model in different tunnels at different frequencies. Furthermore, simplified models for the division point in five specific application situations are derived to facilitate the use of the model. The results in this paper could help to deepen the insight into the propagation mechanism within tunnel environments.

Measurement and Analysis of Extra Propagation Loss of Tunnel Curve

“…2 and 3, there are two types of arched tunnels in the modern subway systems. To keep coherence to our previous publications, such as [40] and [41], these two types of tunnels are still named Arched 'Type I" tunnel and Arched 'Type II" tunnel, respectively. 'Type I" consists of three plane walls and an arched roof, and 'Type II" includes arched walls and roof, but a plane floor, which is more like a semi-circle.…”

“…The same or similar terminology is used in [35] and [46], but note that the attenuation unit in [dB/100 m] or [dB/1000 m] in these publications are defined by "total loss", including the original loss in the straight tunnel and the extra loss resulting from the curve, whereas the EL_curve [dB/100 m] defined in this paper means only the "extra loss" of tunnel curve. The advantage of distinguishing the extra loss from the total loss is that the extra loss of tunnel curve can be added to the loss predicted for straight tunnels, so that the existing models for straight tunnels, such as the models in [15]- [25], [27], [28], [40], [41], still can work in curved tunnels.…”

Measurements and Analysis of Large-Scale Fading Characteristics in Curved Subway Tunnels at 920 MHz, 2400 MHz, and 5705 MHz

“…1 and 2, there are two types of arched tunnels in the modern subway systems. In order to keep coherence to our previous publications, such as [27], [47], these two types of tunnels are still named Arched "Type I" tunnel and Arched "Type II" tunnel, respectively. "Type I" consists of three plane walls and an arched roof; "Type II" includes arched walls and roof, but a plane floor, more like a semicircle.…”

Shadow fading cross-correlation of multi-frequencies in curved subway tunnels

“…There are two types of arched tunnels in the modern subway systems, named Arched "Type I" and Arched "Type II" as mentioned with more details in [16] [17]. Arched "Type I" tunnel is composed of three plane walls and an arched roof with dimensions 7.59 × 5.52 m. Arched "Type II" tunnel includes arched walls and a plane floor roof with dimensions 8.41 × 6.87 m, which is more similar to a semicircular shape than "Type I".…”