28-GHz Channel Characterization for a Short Tunnel

This letter investigates the channel propagation characterization in a short tunnel through a time-domain channel measurement at 28-GHz frequency band. The statistic parameters of the channel, such as root-mean-square delay spread (RMS-DS), K-factor, and shadowing are studied, and the results reveal that the parameters align better to the normal distribution. RMS-DS is positively correlated with the shadowing but negatively correlated with the K-factor. We also deduced that the K-factor is negatively correlated with the shadowing. From the angular measurements, it is inferred that the signal propagation in the tunnel is around 0° and 180° directions, and the maximum number of reflections at 30 and 75 m are 6 and 8, respectively. Furthermore, it is found that the angular spread pursues a decreasing function of transmitter-receiver distance.