Charilaos I. Kourogiorgas

Cooperative Hybrid Land Mobile Satellite---Terrestrial Broadcasting Systems: Outage Probability Evaluation and Accurate Simulation

Next generation communication networks incorporate Land Mobile Satellite (LMS) systems in order to provide greater areas of coverage and higher throughput for specific applications. Cooperation between satellite communication networks and terrestrial relays is or increasing the system’s performance and availability. In this paper, the outage performance of a cooperative hybrid satellite and terrestrial system configuration is analytically evaluated assuming that the satellite links suffer from shadowed Rician fading, while the terrestrial link suffers from the Nakagami-m fading. Two cooperative relaying strategies are examined and the final formulas for the calculation of the outage probability are given. Moreover, a block diagram for the generation of time series for the reliable simulations of the outage probability of the cooperative hybrid land mobile satellite systems is given. The theoretical results and the simulation results almost coincide. Moreover, extended numerical results investigate the impact, of different shadowing conditions and more generally of the satellite links elevation angles, on the overall cooperative LMS system performance.

Channel Model for Satellite Communication Links Above 10GHz Based on Weibull Distribution

Modern satellite communication networks will employ frequencies above 10GHz. At these frequency bands, rain attenuation is the dominant fading mechanism. In this paper, a novel channel model, a synthesizer for generating rain attenuation time series for satellite links operating at 10GHz and above is presented. The proposed channel model modifies Maseng-Bakken (M-B) model since it generates rain attenuation time series that follow the Weibull distribution. The new stochastic dynamic model is based on the first-order Stochastic Differential Equations (SDEs) and considers rain attenuation induced on a slant path as a Weibull-based stochastic process. Moreover, the theoretical expressions for the computation of the exceedance probability of hitting time random variable are presented. The hitting time statistics may be employed for the optimum design of Fade Mitigation Techniques (FMTs). The synthesizer is verified in terms of the exceedance probability and the theoretical CCDF of hitting time comparing to these derived from the simulations in the numerical results section.

Cloud Attenuation Statistics Prediction From Ka -Band to Optical Frequencies: Integrated Liquid Water Content Field Synthesizer

The impact of cloud impairments on satellite links is increasing with the employment of higher frequency bands. In this paper, a model for predicting cloud attenuation statistics for satellite communication systems operating from Ka-band to optical range is presented. The cloud attenuation must be accurately quantified for the reliable design of satellite communication systems. A stochastic dynamic model for the generation of integrated liquid water content (ILWC) fields is proposed. The model is based on the stochastic differential equations and incorporates the spatial and temporal behavior of ILWC. Classifying the cloud types based on the cloud vertical extent and using the microphysical properties of clouds, the well-known Mie scattering theory and the global statistics for ILWC by International Telecommunications Union-Radio (ITU-R), a unified space-time model for the prediction of induced attenuation due to clouds for frequencies above Ka-band up to optical range is presented. The proposed model is tested in terms of first order statistics, compared first with ITU-R P.840-6 model and then with data obtained in the literature, showing encouraging results. Moreover, the probability of cloud occurrence for optical satellite single and site diversity system is calculated. Finally, the limitations and the applicability of the proposed model are discussed.

Satellite-based sensor networks: M2M Sensor communications and connectivity analysis

In this paper, we study the performance of satellite-based sensor networks. In particular, we consider dense networks of M2M sensor devices deployed in several geographical locations. The M2M sensor devices are locally grouped into clusters and communicate with a satellite gateway. The proposed network architecture is a potential solution for remote monitoring and surveillance networks usually deployed on border and non-habitable areas. We also consider the employment of Ka band for the broadband satellite connection. Consequently, an efficient clustering methodology is proposed for the M2M sensor devices while the feasibility of the proposed system in terms of connectivity of the satellite gateways using high data rate terrestrial links operating at frequencies above 10 GHz, is investigated. Finally, we present realistic satellite link budget analysis using either GEO or LEO Ka band satellites.

Outage performance of dual branch diversity techniques in broadband fixed wireless access networks

New physical–mathematical models for the calculation of the outage probability of the maximal ratio combining and selection combining dual branch spatial diversity schemes for broadband fixed wireless access networks operating above 10 GHz are presented. At these frequency bands and considering line-of-sight conditions, rain attenuation is the dominant fading mechanism, which should be taken into account in the radio communications system design. The models are based on bivariate inverse Gaussian (IG) distribution and on the adoption of a spatial correlation coefficient for the convergent terrestrial wireless links. IG distribution has been shown that models accurately the rain attenuation fading for both temperate and tropical climatic regions. The models are validated with numerical results and some useful conclusions are drawn.

On the Outage Probability Prediction of Time Diversity Scheme in Broadband Satellite Communication Systems

A novel model for the outage probability prediction in time diversity satellite communication (SatCom) systems operating above 10GHz is proposed. Due to the migration of operating frequency at Ka band and above, atmospheric phenomena afiect the signal. Rain is the dominant fading mechanism. Diversity techniques are the probable solution of the compensation of rain fading. Among the diversity techniques, time diversity has been identifled as an e-cient and cost efiective technique. A method for the prediction of outage performance and diversity gain of time diversity SatCom systems is presented based on the physical assumptions of a well accepted dynamic stochastic model. The new method is tested against with simulated and experimental data with encouraging results.

A New Method for the Prediction of Outage Probability of LOS Terrestrial Links Operating Above 10 GHz

In this letter, a new method for the prediction of outage probability due to rain attenuation for line-of-sight (LOS) terrestrial links operating above 10 GHz is presented. Assuming that rain attenuation and rain rate follow the inverse Gaussian (IG) distribution and by employing a spatial structure of the specific rain attenuation, we propose an analytical method for the calculation of the IG statistical parameters of rain attenuation in terms of the IG rain rate statistical parameters. The proposed model is validated with experimental data included in the database of the Study Group 3 (DBSG3) of the International Telecommunication Union (ITU), and it is also compared to last version of ITU-R. P.530-14 rain attenuation prediction model for terrestrial links. The results are very encouraging since the overall performance of the new model is better compared to the ITU-R P. 530-14 one.

Prediction of Joint Rain Attenuation Statistics Induced on Earth–Satellite Multiple Site Diversity Systems Using Gaussian Copula

A novel prediction model of the joint exceedance probability of rain attenuation in Earth–satellite site diversity systems based on the Gaussian copula is presented. The proposed model is based on a number of experimental data of two-site diversity systems with different configurations. The proposed model outperforms the existing model for two-site diversity given in Recommendation ITU-R P.618-12 and the recently presented model based on the Clayton copula. The method is generalized to multiple-site diversity prediction. Results for a few existing three-site diversity experiments are evaluated.

On Rain Attenuation Time Series Generation: A New Simple Copula-based Channel Model for Satellite Slant Paths

The use of copulas decreases and almost vanishes the dependence of stochastic synthesizers from theoretical distributions, since empirical distributions can also be used. Therefore, in this correspondence, a novel rain attenuation time series synthesizer based on a Gaussian copula function is proposed. First, the Gaussian copula is tested for the modeling of joint exceedance probability of rain attenuation on a temporal domain with good results. Afterward, taking an advantage of the results from the previous tests, two expressions are proposed for the modeling of the Gaussian copula parameter as a function of time for the temperate and tropical regions. These expressions may be refined using more experimental beacon data in various climatic regions and for different satellite link characteristics. The synthesizer is based on the generation of time series from copula functions. It reproduces the first-order statistics and it is independent of the distribution that may describe well the rain attenuation used as input. The synthesizer is validated on the first-order statistics, for no time delay and with time delay and on the second-order statistics.

Rain attenuation time series synthesizer for LEO satellite systems operating at Ka band

The increasing demand for delivering high data rates in Earth Observation systems using Low Earth Orbit (LEO) satellites has led the migration of operating frequency to Ka band. In this high frequency band rain attenuation is the dominant factor for the degradation of the quality of the link and Fade Mitigation Techniques (FMTs) are necessary in order to implement the links. However, FMTs require the prediction of time series of rain attenuation. In this paper a synthesizer is proposed which will be able to produce rain attenuation time series for LEO slant paths. The input parameters for this model are the elevation angle dependent statistical parameters of rain attenuation (long-term and dynamic) for a given elevation angle. Furthermore, in this paper an accurate methodology is provided to calculate the dynamic input parameter of the induced rain attenuation on the elevation angle-dependent slant path. The geographical coordinates of the sub-satellite points are derived from the AGIs software tool Satellite Tool Kit (STK).