Research on real-time elimination of UWB radar ranging abnormal value data

For indoor positioning, ultra-wideband (UWB) radar comes to the forefront due to its strong penetration, anti-jamming, and high precision ranging abilities. However, due to the complex indoor environment and disorder of obstacles, the problems of diffraction, penetration, and ranging instability caused by UWB radar signals also emerge. During the experiment of indoor positioning with UWB radar ranging module P440, it was found that the distance information measured in a short time was unstable, because of the complex indoor environment and unpredictable noise signal. Therefore, the abnormal value migration of the positioning trajectory occurred in real-time positioning. To eliminate this phenomenon and provide more accurate results, the abnormal values need to be removed. It is not difficult to eliminate abnormal value accurately based on a large number of data, but it is still a difficult problem to ensure the stability of the positioning system by using a small amount of measurement data in a short time to eliminate abnormal value in real-time ranging data. Thus, this paper focuses on the experimental analysis of a UWB-based indoor positioning system. To improve the stability of UWB radar ranging data and increase the overall accuracy, this paper studies a large number of UWB radar ranging data by using high-frequency ranging instead of mean value to train estimation model. Based on the Gaussian function outlier detection, abnormal values are eliminated. By using the training distance estimation model and estimating the distance value, the ranging error obtained is nearly 50 % lower than the peak and mean ranging errors in general.

Bell’s Spaceships: The Views from Bow and Stern

Unravelling apparent paradoxes has proven to be a powerful tool for understanding the complexities of special relativity. In this paper, we focus upon one such paradox, namely Bell’s spaceship paradox, examining the relative motion of two uniformly accelerating spaceships. We consider the view from either spaceship, with the exchange of photons between the two. This recovers the well-known result that the leading spaceship loses sight of the trailing spaceship as it is redshifted and disappears behind what is known as the ‘Rindler horizon’. An immediate impact of this is that if either spaceship tries to measure the separation through ‘radar ranging’, bouncing photons off one another, they would both eventually fail to receive any of the photon ‘pings’ that they emit. We find that the view from this trailing spaceship is, however, starkly different, initially, seeing the leading spaceship with an increasing blueshift, followed by a decreasing blueshift. We conclude that, while the leading spaceship loses sight of the trailing spaceship, for the trailing spaceship the view of the separation between the two spaceships, and the apparent angular size of the leading spaceship, approach asymptotic values. Intriguingly, for particular parameterisation of the journey of the two spaceships, these asymptotic values are identical to those properties seen before the spaceships began accelerating, and the view from the trailing spaceship becomes identical to when the two spaceships were initially at rest.