Abstract
To suppress the deep fading of radio waves caused by the tunnel waveguide effect, this paper presents an optimized scheme for the spatial and polarization diversities of tunnel antennas. Through the correlation coefficient analysis of path loss curves obtained by antennas placed at different positions, the two antenna positions that generate path loss curves with the lowest correlation coefficient are found, and these two antennas are defined as a diversity antenna pair. Using this scheme, the spatial diversity properties of the transmitting antenna and receiving antenna, as well as the spatial-polarization combined diversity property of the transmitting antenna, are obtained. Furthermore, the impact of antenna polarization on the spatial diversity property is investigated. The performance of the proposed scheme for spatial and polarization diversities is evaluated in terms of the intensity and uniformity of the path loss. The simulation results illustrate that the proposed diversity optimization scheme can suppress the influence of the waveguide effect and achieve more uniform and flatter radio wave coverage in a tunnel environment.
Highlights
Mobile communication has entered the fifth-generation era and is applied to various scenarios where uniform radio coverage is desired
To determine the diversity effect more intuitively, in addition to directly observing the difference between the path loss curves obtained by a diversity antenna pair and a single antenna, this paper uses the median field intensity proposed in [22] and the system field strength flatness factor proposed in [23] to evaluate the slow and fast fading characteristics of the received power, respectively, for the cases of a single antenna and a diversity antenna pair
Compared with the single receiving antenna, the receiving diversity antenna pairs in the vertical polarization can give a better distribution in the near region and remove the deep fading, the median field intensity in the near region increases by 11% and the system field strength flatness factor decreases by 5%
Summary
Mobile communication has entered the fifth-generation era and is applied to various scenarios where uniform radio coverage is desired. The radio wave coverage in the tunnel environment has been studied for a long time [1]–[3], and it can be modeled and predicted by measurements or by physics-based methods. In [6], the extra loss caused by the tunnel curvature, frequency, polarization, and area of the cross section is analyzed by measurement These measurement results can provide insights into the propagation characteristics of the studied channels, but it is time consuming and difficult to reveal the propagation mechanism. In [21], it is found that a good quality signal can be achieved in almost the entire studied area by applying a large-scale diversity for antennas These studies still have shortcomings in the suppression of deep fading caused by the waveguide effect in tunnel environments.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
