Fade Dynamics Investigation applying Statistics of Fade Duration and Level Crossing Rate
Abstract — The impact of rain attenuation on wireless communication signals is predominant because of the used high frequency (above 10 GHz). The knowledge of statistics of attenuation is very important for planning point-to-point microwave links operating in high frequency band. Describing the statistics of attenuation is possible for instance with fade duration or level crossing rate. In our examination we determine these statistics from one year measured data for a given microwave link, and we are going to make an attempt to transform the level crossing rate statistic to fade duration statistic. Keywords — Rain Attenuation Measurement, Fade duration, Level Crossing Rate. I. I NTRODUCTION O investigate wave propagation phenomena a rain attenuation and weather data measurement system was established. Currently in Hungary a number of point-to-point millimetre wave links operating in the frequency bands of 13, 15, 23 and 38 GHz. The received IF signal powers are collected with the meteorological data together using weather stations at different locations for data collection. This paper investigates the dynamics of rain attenuation. Different statistics such as fade duration, number of events and level crossing rate are important for analysis of wave propagation phenomena, because they are indicating important information about the dynamics of the received signal. These statistics can be derived from our available measured data. To prepare these second-order statistics a one year period data measured on one 38 GHz link in Hungary in 2004 is considered. Fade duration and level crossing rate statistics will be compiled for attenuation exceeding different attenuation levels (fade thresholds) from 3 up to 8 dB. The parameters of the investigated link are described in Table I. The paper is organized as follows: Section 2 presents the fade duration and level crossing rate, Section 3 describes our data processing method while Section 4 shows our fade duration estimation from LCR, concluding remarks are given in Section 5.
Statistical analysis of rain fade slope
An analysis is made of the measured distributions of the fade slope of rain attenuation, conditional for attenuation values, measured at Eindhoven University of Technology from the satellite Olympus. It is found that the distribution is similar for positive and negative fade slopes and independent of frequency in the range from 12 to 30 GHz. A distribution model for the conditional distribution is found. The only parameter of the distribution is the standard deviation, which is found to be proportional to attenuation level and dependent on rain type, on the low-pass filter bandwidth and on the time interval used in the slope calculation. The observed relation between the standard deviation and attenuation is compared with results from other measurement sites. From this comparison it is found that the fade slope standard deviation is likely to depend on elevation angle and on climate, through its dependence on rain type.
Imaging the in-plane magnetization in a Co microstructure by Fourier transform holography.
We report on experiments using Fourier transform holography to image the in-plane magnetization of a magnetic microstructure. Magnetic sensitivity is achieved via the x-ray magnetic circular dichroism effect by recording holograms in transmission at off-normal incidence. The reference beam is defined by a narrow hole milled at an inclined angle into the opaque mask. We present magnetic domain images of an in-plane magnetized cobalt element with a size of 2 μm × 2 μm× 20 nm. The domain pattern shows a multi-vortex state that deviates from the simple Landau ground state.