Frequency Scaling Of Rain Attenuation Research Articles

A simple real‐time frequency scaling technique for rain attenuation and its performance

SummaryA new algorithm has been proposed for frequency scaling of rain attenuation. It uses the real‐time estimates of a spatial variation index in the rain rate profile suggested in simple atmospheric model (SAM) to obtain the scaled attenuation. Measured data are used to validate the algorithm which showed a typical accuracy of better than 2.5 dB for 95% confidence. The time profile of a model parameter derived from measured values has also been effectively utilized to envisage the rain cell movement, particularly for high elevation conditions. Simulated data with predefined rain rate profiles were also used for validations. The relative contributions of the model error and the measurement noise to the final error were obtained. The errors are attributed to the modelling mismatch and intermediate parameter estimation error. The estimation accuracy of the algorithm was found to worsen with reducing elevation. The overall error remains within 3 dB for 0.5 dB of measurement noise and up to lowest elevation of 30°. The simple approach of the model in conjunction with the adequate accuracy makes this algorithm a potential candidate to be used for real‐time open‐loop fade mitigation.

Short-Term Rain Attenuation Frequency Scaling for Satellite Up-Link Power Control Applications

In this paper, a novel stochastic dynamic model for the short-term frequency scaling of rain attenuation is presented. The model captures the dynamic characteristics of the instantaneous frequency scaling factor and provides the means to incorporate them in simultaneous rain attenuation time series generation, as well as in analytical calculations. Moreover, an analytical framework is proposed for rain attenuation prediction at a given frequency based on the rain attenuation measured at another frequency. The proposed model can be used for the timely activation of an open-loop up-link power control scheme in broadband satellite communication networks operating at frequencies above 10 GHz. It is applied to simulated rain attenuation data that have been obtained using the Synthetic Storm Technique on rain rate experimental data. Finally, it is shown how the new model improves the performance of an up-link power control scheme in terms of system availability.

Frequency scaling of rain attenuation based on microphysical characteristics for SatCom links

‘Frequency scaling’ relates to the variation of propagation effects as a function of frequency. The frequency scaling ratio between the Ka and V bands, derived using a model based on an integrated parameter such as rain rate, is inadequate. In fact, propagation variations due to the microphysical characteristics of rain need to be considered in order to improve the existing scaling model, particularly at higher frequencies. Many different laws for raindrop size distribution, combined with one year of measured drop size distribution (DSD), are used to study propagation sensitivity to drop size and shape. A statistical study of the normalised DSD has been carried out, and two scaling models are proposed in which microphysical considerations are taken into account. Italsat and Olympus data have been used to validate this approach.

Frequency Scaling of Rain Attenuation for Satellite Communication Links

Frequency Scaling of Rain Attenuation for Satellite Communication Links

Frequency scaling of rain attenuation for satellite communication links

One year of copolarized signal data from the OLYMPUS satellite's 12, 20, and 30 GHz beacons were examined for frequency scaling of attenuation. The statistics of the ratios of attenuation in dB for the frequency pairs 30/20, 20/12, and 30/12 GHz computed at each 0.1 s-sample instant were found to be nearly independent of fade depth. It was found that attenuation in dB scales with frequency to the 1.9 power. Also, attenuation ratios computed from the separate statistics of attenuation at each frequency for the same level of occurrence are very close to those found from instantaneous attenuation ratios.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Instantaneous frequency scaling of rain attenuation at 11.6-17.8 GHz with SIRIO data

The ratio of simultaneous attenuation measurements performed at 11.6 and 17.8 (or 17.0 GHz) with the Italian satellite SIRIO is discussed. The main application of this information is in the field of the "up-path power control" in earth-space telecommunication systems for which the requirement of estimating the uplink attenuation form measurements on the downlink will probably be taken into consideration as a tool to keep constant the total power received on board. The analysis shows that the average ratio between attenuations at 17.8 and 11.6 GHz, conditioned to the downlink attenuation (11.6 GHz) tends to decrease slightly with attenuation; it turns out to be very close to the ratio between equiprobable values of attenuation computed from the concurrent cumulative distributions (long-term frequency scaling ratio); the standard deviation is of the order of 10 percent of the average value and also exhibits some tendency to decrease; both the overall cumulative distributions and the conditional ones are well fitted by log-normal probability models with standard deviation (of the natural logarithm) constant and equal to 0.13-0.14 up to 5.5 dB in the downlink attenuation.

Frequency scaling of rain attenuation at centimeter and millimeter waves using a path‐averaged drop size distribution

The applicability of several frequency scaling methods of rain attenuation is discussed based upon the cumulative distributions of rain attenuations at 81.8, 34.5, and 11.5 GHz measured in the same horizontal propagation path of 1.3 km for 1 year. A frequency scaling method (MISD) based upon the concept of a path‐averaged raindrop size distribution N−(D) is newly applied to statistical prediction of the attenuation and is shown to be effective at millimeter wave bands where attenuation changes remarkably depending upon the raindrop size distribution, although the usefulness of MISD has been verified for time‐sequential data. The size distribution determined from the statistical data at the three frequencies is given by N−(D) = 26,000 R−(−0.294)exp [−(5.6 R−0.283D)], 10 ≤ R− ≤ 70 mm/h, where R− is the path‐averaged rainfall rate in millimeters per hour and D is the diameter of a raindrop in millimeters. Frequency dependence of attenuation calculated by using this size distribution shows that the prediction of rain attenuation based upon the Laws and Parsons size distribution results in an underestimation at frequencies above 80 GHz.

Frequency scaling of rain attenuation

A simple method of frequency scaling for rain attenuation is presented. This method includes a correction factor for rain inhomogeneity and takes into account the high correlation between peak rainfall rate and attenuation. The results are compared with Drufuca's empirical method. The discrepancies between theoretical scaling and empirical scaling are found to be reduced by about a factor of two when the corrections presented herein are incorporated.