Estimation of the K-Factor for Temporal Fading From Single-Snapshot Wideband Measurements

The Ricean K-factor is the ratio of the power of the deterministic multipath component (MPC) and the power of all other stochastic MPCs. The classical moment-based method has been successfully used to estimate the K-factor from time series measurements. In this paper, we apply this method to estimate the K-factor for narrowband temporal selectivity, based upon the analysis of frequency-selectivity in single-snapshot wideband measurements. We also derive the theoretical bias of this estimator and find it depends jointly on the number of channel transfer function envelope samples across the measurement bandwidth, the correlation among such samples, and the K-factor values. Qualitative analysis indicates that the bias increases nearly linearly with the K-factor (K ≥ 1 on the linear scale) and is affected by correlation amongst the samples. Furthermore, the bias is inversely proportional to the number of samples. Simulations confirm the validity of the derivations. Moreover, a measurement campaign is designed at 28 GHz with a system bandwidth of 400 MHz in an urban microcell scenario. The proposed estimator is used to extract the statistics of the K-factor in line of sight and non-line of sight scenarios. The relationship between the K-factor and distance is investigated and a linear model is used to characterize it.