Millimeter-Wave Propagation Channel Characterization for Short-Range Wireless Communications

This paper presents and analyzes the results of millimeter-wave 60-GHz frequency range propagation channel measurements that are performed in various indoor environments for continuous-route and direction-of-arrival (DOA) measurement campaigns. The statistical parameters of the propagation channel, such as the number of paths, the RMS delay spread, the path loss, and the shadowing, are inspected. Moreover, the interdependencies of different characteristics of the multipath channel are also investigated. A linear relationship between the number of paths and the delay spread is found, negative cross correlation between the shadow fading and the delay spread can be established, and an upper bound exponential model of the delay spread and the path loss is developed to estimate the worst case of the RMS delay spread at given path loss. Based on the DOA measurements that are carried out in a room [line of sight (LOS)] and in a corridor with both LOS and nonline-of-sight (NLOS) scenarios, radio-wave propagation mechanisms are studied. It is found that considering the direct wave and the first-order reflected waves from smooth surfaces is sufficient in the LOS cases. Transmission loss is very high; however, diffraction is found to be a significant propagation mechanism in NLOS propagation environments. The results can be used for the design of 60-GHz radio systems in short-range wireless applications.     

Reversible temperature effects in the matrix IR spectra of halogenated 2-propanols

The reversible temperature effects in the IR spectra of CCl₃CHOHCCl₃ and of a few other halogenated 2-propanols in N₂, CO and mixed N₂-Ar matrices have been studied. Alcohol-nitrogen complexes are formed reversibly and irreversibly in matrices containing nitrogen.     

Characterization of Doppler spectra for mobile communications at 5.3 GHz

Tapped-delay-line (TDL) channel models are developed from a measured database for outdoor and indoor mobile communications at 5.3 GHz. Meanwhile, several types of Doppler spectra are found at the different taps of the TDL models. For simulation purposes, a general three-dimensional autocorrelation function of the scattered waves is derived and connected to the distributions of angles of arrival of the waves and antenna radiation patterns. Furthermore, the propagation mechanisms of the different types of Doppler spectra observed in the TDL models are explained based on the comparisons between measured and simulated results where the Fourier transformations are performed on the autocorrelation functions to obtain the Doppler power spectra.     

Propagation characteristics for wideband outdoor mobilecommunications at 5.3 GHz

In this paper, empirical channel models and parameters are derived from the wideband measured data at 5.3 GHz in outdoor mobile communications. The path loss exponents and intercepts are obtained by using the least square method. The mean excess delay and mean root-mean-square (rms) delay spread are within 29-102 ns and 22-88 ns, respectively. The correlation distances and bandwidths are within 1-11 λ and 1.2-11.5 MHz, respectively, when the envelope correlation coefficients equal 0.7 in line-of-sight cases. These correlation values depend strongly on the base station antenna heights. The window length for averaging out the fast fading components is about 1-2 m for microcells and picocells. The multipath number distributions follow both Poisson's and Gao's distributions, but Gao's distribution is better in the high probability region. Large excess delays up to 1.2 μs and rms delay spread about 0.42 μs are found in the urban rotation measurements, where the receiver is close to a large open square     

Intervalley-scattering-induced electron-phonon energy relaxation in many-valley semiconductors at low temperatures

We report on the effect of elastic intervalley scattering on the energy transport between electrons and phonons in many-valley semiconductors. We derive a general expression for the electron-phonon energy flow rate at the limit where elastic intervalley scattering dominates over diffusion. Electron heating experiments on doped n-type Si samples with electron concentrations (3.5-16.0) x 10(25) m(-3) are performed at sub-Kelvin temperatures. We find a good agreement between the theory and the experiment.