Korea Research Institute of Ships and Ocean Engineering, Daejeon 34103, Republic of Korea.
Department of Ship and Ocean Engineering Major, University of Science and Technology, Daejeon 34113, Republic of Korea.
Sensors (Basel). 2023 May 24;23(11):5046. doi: 10.3390/s23115046.
There is an increasing need for an independent terrestrial navigation system, owing to the increasing reliance on global navigation satellite systems (GNSS). The medium-frequency range (MF R-Mode) system is considered a promising alternative; however, the skywave effect caused by ionospheric changes at night can degrade its positioning accuracy. To address this problem, we developed an algorithm to detect and mitigate the skywave effect on MF R-Mode signals. The proposed algorithm was tested using data collected from Continuously Operating Reference Stations (CORS) monitoring the MF R-Mode signals. The skywave detection algorithm is based on the signal-to-noise ratio (SNR) induced by the groundwave and skywave composition, whereas the skywave mitigation algorithm was derived from the I and Q components of the signals obtained through IQ modulation. The results demonstrate a significant improvement in the precision and standard deviation of the range estimation using CW1 and CW2 signals. The standard deviations decreased from 39.01 and 39.28 m to 7.94 and 9.12 m, respectively, while the precision (2-sigma) increased from 92.12 and 79.82 m to 15.62 and 17.84 m, respectively. These findings confirm that the proposed algorithms can enhance the accuracy and reliability of MF R-Mode systems.
由于对全球导航卫星系统 (GNSS) 的依赖程度不断增加，因此对独立的地面导航系统的需求日益增长。中频范围 (MF R-Mode) 系统被认为是一种很有前途的替代方案；然而，夜间电离层变化引起的天波效应会降低其定位精度。为了解决这个问题，我们开发了一种算法来检测和减轻 MF R-Mode 信号中的天波效应。所提出的算法使用从连续运行参考站 (CORS) 收集的数据进行了测试，这些数据用于监测 MF R-Mode 信号。天波检测算法基于地波和天波成分引起的信噪比 (SNR)，而天波缓解算法则源自通过 IQ 调制获得的信号的 I 和 Q 分量。结果表明，使用 CW1 和 CW2 信号进行的距离估计的精度和标准偏差有了显著提高。CW1 和 CW2 信号的标准偏差分别从 39.01 和 39.28 米降低到 7.94 和 9.12 米，而精度（2-sigma）分别从 92.12 和 79.82 米提高到 15.62 和 17.84 米。这些发现证实，所提出的算法可以提高 MF R-Mode 系统的准确性和可靠性。
