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 wellaccepted Maseng-Bakken model in -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.Index Terms-Rain attenuation, satellite link, spatial structure, stochastic differential equations (SDEs).
Performance evaluation tools for wireless cellular systems are very important for the establishment and testing of future internet applications. As the complexity of wireless networks keeps growing, wireless connectivity becomes the most critical requirement in a variety of applications (considered also complex and unfavorable from propagation point of view environments and paradigms). Nowadays, with the upcoming 5G cellular networks the development of realistic and more accurate channel model frameworks has become more important since new frequency bands are used and new architectures are employed. Large scale fading known also as shadowing, refers to the variations of the received signal mainly caused by obstructions that significantly affect the available signal power at a receiver's position. Although the variability of shadowing is considered mostly spatial for a given propagation environment, moving obstructions may significantly impact the received signal's strength, especially in dense environments, inducing thus a temporal variability even for the fixed users. In this paper, we present the case of lognormal shadowing, a novel engineering model based on stochastic differential equations that models not only the spatial correlation structure of shadowing but also its temporal dynamics. Based on the proposed spatio-temporal shadowing field we present a computationally efficient model for the dynamics of shadowing experienced by stationary or mobile users. We also present new analytical results for the average outage duration and hand-offs based on multi-dimensional level crossings. Numerical results are also presented for the validation of the model and some important conclusions are drawn.
High Altitude Platform Networks (HAPNs) comprise an emerging communication solution promising to exploit many of the best aspects of terrestrial and satellite-based systems. Nevertheless, while offering advantageous propagation characteristics, HAP networks are still subject to large fades due to atmospheric precipitation and especially due to rain, for the allocated high frequency bands, necessary though to deliver high data rates. Multi-HAP or orbital HAP diversity is an effective technique to reduce the large fade margins required to assure the specified quality of service (QoS). Received signals from multiple HAPs can be combined at the terminal station with the use of various signal processing techniques. The subject of this paper is to present physical statistical models for the evaluation of the outage probability of a dual-HAP orbital diversity system using either SC (selection combining) or MRC (maximal ratio combining) techniques. The analytical probabilistic models are interesting since we have rain attenuation correlated fading channels. Extended numerical results are presented in the final section of the paper comparing MRC and SC reception techniques. Some significant conclusions are drawn.
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