Uncertainty Analysis Methodology for Measurements of Dynamic Millimeter-Wave Channels

Quantification of uncertainties in the results of channel sounding measurements is important for their interpretation and further usage. In this paper, a novel uncertainty analysis methodology to quantify uncertainties of condensed parameters in measurements of dynamic millimeter-wave channels is presented. The bandwidth limitation and multipath threshold are identified as important impairments. Therefore, the methodology provides three uncertainty metrics for condensed parameters, namely a standard uncertainty to quantify the impact of random variations; a bias due to the multipath threshold; and a total bias including the impact of the bandwidth limitation. These uncertainty metrics are highly channel dependent. Therefore, the proposed methodology creates reference channels, which are representative of corresponding measured channels. Hardware and processing impairments are included in the analysis via a Monte Carlo simulation. This results in a general methodology that can quantify uncertainties in both static and dynamic channel measurements of any wideband channel sounder. The methodology is implemented, verified and demonstrated for the TU/e channel sounder, which exemplifies how it can be used. The proposed methodology can improve the analysis, interpretation and reporting of channel measurement results.</p

Impact of Human Blockage on Dynamic Indoor Multipath Channels at 27 GHz

Human blockage and its dynamics are potential challenges for millimeter-wave (mm-wave) mobile communication. This article presents the results of wideband measurements at 27 GHz with one human blocker close by a dynamic mobile terminal (MT) as well as one or multiple dynamic human blockers further away from an MT. The measured human blockage loss is largest when the direct path (DP) in a line-of-sight (LOS) is blocked, but this loss is limited by other multipath components (MPCs). For nonline-of-sight (NLOS) channels, it is shown that human blockage loss is typically negligible. The presented measurement results show that human blockage loss in multipath channels is much smaller than that reported in diffraction-and measurement-based models, which neglect or minimize the contribution of all MPCs other than the DP. This suggests that the multipath nature of the indoor wireless channel highly limits the impact of human blockage

Extended range ultra-wideband millimeter-wave channel sounder with over-the-air calibration

In this paper, an ultra-wideband millimeter-wave channel sounder is introduced. The channel sounder, consisting of a Vector Network Analyzer and 1 km of fiber, can perform high resolution channel sounding over long distances. A wired response calibration is compared to an over-the-air calibration. It is shown that the over-the-air calibration of the channel sounder increases the dynamic range in the power-delay-profile by 14 dB compared to the wired response calibration

Bis-N-heterocyclic Carbene Aminopincer Ligands Enable High Activity in Ru-Catalyzed Ester Hydrogenation

Bis-N-heterocyclic carbene (NHC) aminopincer ligands were successfully applied for the first time in the catalytic hydrogenation of esters. We have isolated and characterized a well-defined catalyst precursor as a dimeric [Ru₂(L)₂Cl₃]­PF₆ complex and studied its reactivity and catalytic performance. Remarkable initial activities up to 283 000 h^–1 were achieved in the hydrogenation of ethyl hexanoate at only 12.5 ppm Ru loading. A wide range of aliphatic and aromatic esters can be converted with this catalyst to corresponding alcohols in near quantitative yields. The described synthetic protocol makes use of air-stable reagents available in multigram quantities, rendering the bis-NHC ligands an attractive alternative to the conventional phosphine-based systems