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.
Prediction method of fade dynamics on Earth-space paths
The ITU Radiocommunication Assembly, considering a) that for a variety of radiocommunication services, design objectives have to be met that require information on the dynamics of outage events; b) that for the evaluation of parameters associated with the risk of failure to provide a certain quality and reliability of service, the probability of occurrence of fades of a certain duration must be known; c) that for the evaluation of internal parameters inside a fade mitigation technique (FMT) control loop (used to improve the quality and reliability of service), the probability of occurrence of fade slope corresponding to a given attenuation threshold must be known; d) that there is a need to provide engineering information for the calculation of fade duration, interfade duration and fade slope statistics, recommends 1 that the methods described in Annex 1 § 2.2 be used for the calculation of the statistics of fade duration due to the combined effects of attenuation (gases, clouds and rain) and scintillation on Earth-space paths; 2 that the methods described in Annex 1 § 3.2 be used for the calculation of the statistics of fade slope due to attenuation on Earth-space paths.
Fade slope analysis for Alaska, Florida, and New Mexico ACTS propagation data at 20 and 27.5 GHz
This paper analyzes fade slope for the Alaska, Florida, and New Mexico Advanced Communications Technology Satellite (ACTS) propagation data at 20 and 27.5 GHz for the first two years of the experiment (December 1, 1993-November 30, 1995). The propagation experiment will continue to collect data for at least another 21 months. Fade slope is examined on a statistical basis for the three sites. The Florida and New Mexico receiver sites have very different weather characteristics but almost identical elevation angles, while the Alaska receiver terminal has an extremely low elevation angle. The cumulative statistics illustrate the relationship between fade slope, fade level, transmission frequency, and elevation angle for all three sites.