Characteristics of the NLoS Bias for an Outdoor-to-Indoor Scenario at 2.45 GHz and 5.2 GHz

Time-based localization by terrestrial cellular mobile radio as a complement to global navigation satellite systems has gained significant attention. However, under non-line-of-sight (NLoS) conditions, the performance of positioning receivers is degraded by an additional bias. This NLoS bias is defined as the additional propagation distance between the first detectable path and the geometric line of sight. In this letter, we address the NLoS bias as obtained by a channel measurement campaign at different carrier frequencies in an outdoor-to-indoor scenario. It turns out that the obtained NLoS bias is mainly uncorrelated between different base-station links. Furthermore, the NLoS bias is found to be strongly dependent on the geometry of the scenario. In so-called "mild" scenarios, we found out that the NLoS bias is small and almost frequency-independent. In scenarios we call "severe," the NLoS bias is large and frequency-dependent. Additionally, we present the joint probability distributions of the NLoS bias, the normalized power of the first detectable path, and its angle of arrival for carrier frequencies of 2.45 and 5.2 GHz. Moreover, the decorrelation distance of the NLoS bias for a moving receiver is evaluated.