Prediction of fading and link budget in land-satellite (LEO) communication Tal Nir & Ziv Gitelman Department of Communication Systems Engineering , Ben-Gurion University

ROADMAP INTRODUCTION MULTI-PARAMETRIC ALGORITHM SIMULATIONS COMPARISON WITH OTER ALGORITHM CONCLUSIONS

ROADMAP INTRODUCTION MULTI-PARAMETRIC ALGORITHM SIMULATIONS COMPARISON WITH OTER ALGORITHM CONCLUSIONS

Overview Satellites form an essential part of today’s technology: Satellite TV or Direct Broadcasting (DBS) of radio and television; Global Positioning System (GPS) and the new Galileo system; Surveying and weather monitoring satellites. First satellite launched into space: Sputnik (1957). Today: over 800 active satellites.

Satellite Communication When using a satellite for long distance communications, the satellite acts as a repeater. An earth station transmits the signal up to the satellite (uplink), which in turn retransmits it to the receiving earth station (downlink). Different frequencies are used for uplink/downlink. Source: Cryptome [Cryptome.org]

Classification of Satellite Orbits Circular or elliptical orbit Circular with center at earth’s center Elliptical with one focus at earth’s center Orbit around earth in different planes Equatorial orbit above earth’s equator Polar orbit passes over both poles Other orbits referred to as inclined orbits Altitude of satellites Geostationary orbit (GEO) Medium earth orbit (MEO) Low earth orbit (LEO)

MEO vs LEO Satellite Characteristics Circular orbit range altitude under 2000 km 5000 to 12,000 km Orbit period from 1.5 to 2 hours 6 hours Diameter of coverage about 8000 km 10,000 to 15,000 km Round-trip signal propagation delay less than 20 ms less than 50 ms Max. satellite visible time up to 20 min few hours System must cope with large Doppler shifts

Geometry Terms Elevation angle - the angle from the horizontal to the point on the center of the main beam of the antenna when the antenna is pointed directly at the satellite Minimum elevation angle Coverage angle - the measure of the portion of the earth's surface visible to the satellite

Satellite Link Performance Factors Distance between earth station antenna and satellite antenna For downlink, terrestrial distance between ground based station antenna and “aim point” of satellite Buildings’ overlay profile and their random distribution above the rough terrain

Propagation Model Reflection Diffraction Scattering Source: P M Shankar

Link Budget Average Path Loss, Lav, dB Fading describes how the received signal amplitude changes with time. To describe statistical characteristics of multipath phenomena different statistical distributions are usually used Most complicated scenario with strong multipath fading can be sucsessfully described by Rayleigh PDF and CDF 11

Rayleigh Fading Distribution Describes the received signal envelope distribution for channels, where all the components are non-LOS: i.e. there is no-line-of–sight (NLOS) component. It can arise when a two-dimensional vector has elements that are normally distributed, are uncorrelated, and have equal variance 12

ROADMAP INTRODUCTION MULTI-PARAMETRIC ALGORITHM SIMULATIONS COMPARISON WITH OTER ALGORITHM CONCLUSIONS

General problem hmax=110 hmin=10 LEO (/MEO)

Multi-Parametric ALGORITHM Vertical plane : CDF(z1,z2)

Multi-Parametric ALGORITHM Horizontal plane : Profile Horizontal plane- Distributions and density of buildings. CDF(R) :

Multi-Parametric ALGORITHM Vertical plane : CDF(z1,z2) = Horizontal plane : CDF(R)=> p1:= Single scattering p2:= Double scattering p3:= Triple scattering [ We consider worst case taken CDF of Rayleigh ]

ROADMAP INTRODUCTION MULTI-PARAMETRIC ALGORITHM SIMULATIONS COMPARISON WITH OTER ALGORITHM CONCLUSIONS

SIMULATIONS Simulation Setup: Simulator written in Mathematica Simulations performed for city of Stockholm

Simulation Results

SIMULATIONS Simulation Results : 1;

ROADMAP INTRODUCTION MULTI-PARAMETRIC ALGORITHM SIMULATIONS COMPARISON WITH OTER ALGORITHM CONCLUSIONS

Existing Algorithms Empirical – cannot be used for many scenarios Statistical – do not exactly predict total Path Loss (Loo model, Lutz model) Physical – Statistical - every time needs information about geometry of the local buildings (long time) Multiparametric stohastic – currently used

ROADMAP INTRODUCTION MULTI-PARAMETRIC ALGORITHM SIMULATIONS COMPARISON WITH OTER ALGORITHM CONCLUSIONS

CONCLUSIONS In practical meaning, the multi-parametric algorithm is a new tool to investigate a signal strength fading, based on propagation multipath phenomena, by using features of the built-up terrain and antennas location compared with building height profile

Thank you Any Questions ?

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