Prediction of Deep Fading Locations in Path Gain for Antenna Deployment in Tunnels

ABSTRACT In this letter, we propose closed‐form formulas for predicting the locations of deep fading in path gain for tunnel scenarios based on modal analysis. Deep fading, which may severely undermine the stability of wireless communication systems, arises from the destructive interference among the dominant modal components. By identifying the locations where two dominant modes are counter‐phase, the deep fading locations can be predicted, and the related formulas are developed. Based on the analysis, we propose an antenna deployment method for a distributed antenna system to mitigate the deep fading in tunnels. With this method, the deep fading can be mitigated by configuring the spacing between two distributed transmitting antennas. For validation, practical tunnel scenarios are modeled and analyzed using the ray tracing and the modal methods. Numerical results validate our proposed formulas and demonstrate the effectiveness of the deep fading mitigation method.