John D. Kanellopoulos

On the rain attenuation dynamics: spatial-temporal analysis of rainfall rate and fade duration statistics

Knowledge about the dynamic characteristics of rain attenuation is of utmost importance for many applications in terrestrial and satellite communication systems operating at frequencies above 10 GHz. Long-term rain rate statistics and rain rate duration statistics are usually available from meteorological data. In this paper, a spatial–temporal analysis is employed in order to evaluate the rain attenuation power spectrum of a terrestrial/satellite path. The predicted power spectrum is compared with experimental data. Based on the spectral analysis of rainfall rate a method for converting rain rate duration statistics to link fade duration statistics is also proposed. Fade duration statistics are presented for terrestrial and satellite links and compared with available experimental data. The agreement between the predicted results and the experimental data has been found to be quite encouraging. Finally, numerical results are presented for various climatic zones, elevation angles and frequencies. Some very useful conclusions concerning the dynamic properties of rain attenuation for a microwave path are deduced. Copyright

Long-term rain attenuation probability and site diversity gain prediction formulas

Simple models for long-term induced rain attenuation on a slant path and site diversity gain are presented in this work. As verified by numerous tests against the ITU-R databank and other data from the literature, the proposed models exhibit a very good performance. The novel slant path rain attenuation prediction model compared to the ITU-R one exhibits a similar behavior at low time percentages and a better root-mean-square error performance for probability levels above 0.02%. Moreover, comparing the proposed site diversity gain model with other widely accepted models from the literature, an improved performance is observed for distances less than 15 km, while the model performs equally well for greater distances. Furthermore, a sensitivity test between the proposed and Hodges formula with respect to the separation distance D is also carried out. While the lower limit of the proposed model is found to be D=1.7 km, its extension covering large-scale site diversity is successfully compared with experimental data coming from Japan. The set of presented models exhibits the advantage of easy implementation with little complexity and is considered useful for educational and back of the envelope computations.

Intercell Radio Interference Studies in Broadband Wireless Access Networks

Capacity has become of primary importance in broadband wireless access (BWA) networks due to the ever-increasing demand for multimedia services and the possibility of providing wireless Internet, leading to their standardization by IEEE (802.16 WirelessMAN) and ETSI (BRAN HIPERACCESS). The major factor limiting capacity in such systems is interference originating from adjacent cells, namely intercell interference. This paper presents a general analysis of intercell interference for a spectrally efficient BWA cellular configuration. It examines the statistical properties of the carrier-to-interference ratio in both downstream and upstream channels. The focus is on the spatial inhomogeneity of rain attenuation over multiple paths, which is the dominant fading mechanism in the frequency range above 20 GHz, especially when two-layered [i.e., line-of-sight (LOS) and non-LOS] architectures are involved. Besides attenuation from precipitation, various architectural and propagation aspects of local multipoint distribution service systems are investigated through simulations, and worst-case interference scenarios are identified

Statistics of differential rain attenuation on converging terrestrial propagation paths

Rain attenuation is considered to be one of the main causes of interference impairments for terrestrial communication systems operating at frequencies above 10 GHz. A method to predict the cumulative distribution of differential rain attenuation on two converging microwave links is proposed. It is based on a convective raincells model for the structure of the rainfall medium, as well as the lognormal assumption for the point rainfall distribution. The degradation of the carrier-to-interference ratio under rainy conditions is also examined. Numerical results are compared with a set of available experimental data for the differential rain attenuation over pairs of terrestrial links in Brazil.

Cell-site diversity performance of millimeter-wave fixed cellular systems operating at frequencies above 20 GHz

The dominant propagation factor affecting the reliability of millimeter-wave fixed cellular systems operating at frequencies above 20 GHz is rain attenuation. Cell-site diversity is an available method to reduce the rain outage time for these systems. The paper presents an analytical procedure for the evaluation of the outage performance of a cell-site diversity system. Numerical results are compared with available experimental data taken from Canada and the UK. The agreement was found to be quite encouraging. The dependence of cell-site diversity gain on climatic conditions is also investigated and some useful conclusions are deduced.

Multidimensional Rain Attenuation Stochastic Dynamic Modeling: Application to Earth–Space Diversity Systems

A stochastic dynamic model for the induced rain attenuation on multiple radio links is presented in this paper. The model is considered as a generalization of the well-known and well-accepted Maseng–Bakken model in

A comparison of copolar and cochannel satellite interference prediction models with experimental results at 11.6 and 20 GHz

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On the Earth-Space Site Diversity Modeling: A Novel Physical-Mathematical Outage Prediction Model

-dimensions. It incorporates the spatial and time behavior of the rain attenuation phenomena and provides an analytical expression for the transition probability distribution. It consists of a system of stochastic differential equations (SDEs), which, except for the solid mathematical formulation of the correlated rain attenuation stochastic processes, constitutes the general framework for the calculation of other statistical quantities useful for the radio system designers. The long-term statistics and the dynamic properties of rain attenuation are used for the parameterization of the model, without the constraint of any built-in assumptions of the rain field. Finally, the proposed model is used for the generation of correlated rain attenuation time series on multiple satellite communication slant paths and especially to diversity schemes, including site and orbital (angle) diversity. The derived results from the model are tested with respect to experimental long-term statistics for various geometries with very encouraging results. The limitations and the ranges of applicability of the model for Earth–space diversity systems are reported, and the sensitivity of the model on the crucial parameters is discussed.

Performance of N-branch receive diversity combining in correlated lognormal channels

One of the main propagation effects on interference between adjacent Earth–space paths is the differential rain attenuation. In the present paper, two existing copolar and cochannel satellite interference prediction models are compared with experimental data of this kind, derived from radar or attenuation measurements. The comparison shows a quite satisfactory agreement and this combined with the fact that the data refer to satellites quite displaced in the geostationary orbit leads to the following conclusion: the predictive models under consideration can be used not only for fixed satellite systems but also for mobile systems using general antennas with low gains. Copyright

Scattering from conducting cylinders embedded in a lossy medium

A novel model based on the bivariate inverse Gaussian (IG) distribution is presented for the prediction of the outage performance of a dual site diversity Earth-space system. In the present paper, the exceeded rain attenuation induced on each Earth-space path is assumed that follows the IG distribution. The joint rain attenuation exceedance probability is calculated using the long-term statistical parameters of rain attenuation on each individual slant path and adopting a spatial correlation coefficient of rain attenuation variables as a function of the separation distance of the two Earth-stations. The Earth-Space path Database of Study Group 3 (DBSG3) of International Telecommunication Union (ITU) is employed in order to compare the performance of the new method with the ITU-R P.618-10 outage model. The numerical results from the comparison tests are very encouraging.