Improving Interpolation Accuracy of Path Loss in Kriging using Anisotropy of Shadowing Correlation

One of the useful methods of ensuring stable communication for autonomous vehicles is to predict communication quality using radio environment maps. We propose a Kriging method for constructing radio environment maps to improve interpolation accuracy by using anisotropy of the shadowing correlation on the distance and azimuth-angle plane based on the base-station position. Using $2.2-\mathrm{GHz}$ band path-loss data measured in an urban area, we evaluated the accuracy when interpolating the total measurement data of approximately 14,000 points from sample data of 10 and 100 points. We compared the proposed method with four conventional methods: nearest neighbor interpolation, K-nearest neighbors, inverse distance weighting, and conventional ordinary kriging. The median and minimum root means square errors when sample data were extracted 30 times were approximately 8.2 and 6.4 dB when the number of samples was 10, and approximately 4.7 and 4.2 dB when the number of samples was 100. These results indicate that the proposed method can interpolate with higher accuracy than the conventional methods.