Rec. Itu-r s. 1592




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Rec. ITU-R S.1592

RECOMMENDATION ITU-R S.1592

Methodology to assess compliance of non-geostationary fixed-satellite service


satellite systems in circular orbits with the additional operational limits on downlink equivalent power flux-density in Article 22 of
the Radio Regulations

(2002)
The ITU Radiocommunication Assembly,



considering

a) that the World Radiocommunication Conference (Istanbul, 2000) (WRC-2000) adopted, in Article 22 of the Radio Regulations (RR), limits to the downlink equivalent power flux-density (epfd) radiated by non-geostationary (GSO) fixed-satellite service (FSS) systems in certain frequency bands, to protect GSO FSS and broadcasting-satellite service (BSS) networks operating in the same frequency bands;

b) that RR Article 22 includes single-entry validation limits to the epfd in RR Tables 22-1A to 22 1D, single-entry operational limits to the epfd in RR Tables 22-4A, 22-4B and 22-4C, and single entry additional operational limits to the epfd into antennas of certain sizes in RR Table 22 4A1, which apply to non-GSO FSS systems for the protection of GSO FSS networks;

c) that compliance of a proposed non-GSO FSS system with the single-entry validation limits will be evaluated by the Radiocommunication Bureau (BR), under RR Nos. 9.35 and 11.31, based on masks of pfd provided by the non-GSO FSS operator, using software defined in Recommen­dation ITU-R S.1503;

d) that compliance of a proposed non-GSO FSS system with the single-entry operational limits to the epfd and, for certain antenna sizes, single-entry additional operational limits to the epfd is subject to verification by administrations;

e) that RR Appendix 4, as modified by WRC-2000, requires an administration responsible for a non GSO FSS system to ensure that the single-entry additional operational limits to the epfd are met,



recognizing

a) that administrations with assignments to GSO FSS networks in frequency bands where additional operational limits to the epfd have been established require a reliable and independent means to determine whether a particular non-GSO FSS system is in compliance with the single entry additional operational limits to the epfd, for their GSO FSS networks,



recommends

1 that the methodology defined in Annex 1 to this Recommendation, based on a full simu­lation of downlinks in a non-GSO FSS satellite system interfering into an operating GSO FSS earth station with a 3 m or 10 m antenna, be used to assess the levels of interference generated by the non-GSO FSS system, in order to verify compliance by the non-GSO FSS system with the additional operational limits to epfd in RR Article 22;

2 that the methodology in Annex 1 to this Recommendation, based on full simulation of downlinks in a non-GSO FSS satellite system interfering into a GSO FSS network, be used by GSO operators as guidance to assess the levels of interference generated by non-GSO systems into any diameter antenna of planned or operational GSO FSS networks.

NOTE 1  Annex 2 discusses an approach that could be used to demonstrate that additional operational limits are met by an operational non-GSO system interfering into an operational GSO FSS earth station. In contrast with Annex 1, which is based on a full simulation approach, Annex 2 is based on the pfd mask approach adopted in Recommendation ITU-R S.1503.

ANNEX 1

Methodology to assess compliance with additional operational limits of the interference generated by non-GSO FSS systems* sharing
frequency bands with GSO FSS networks

1 Introduction


This methodology is based on modelling the satellite systems in their orbits and allows each space station and earth station to track their respective targets, while taking into account the Earth’s rotation. A simulation of this model is sampled over a period of time at a suitably fine sampling rate, and at each sample the range gain product is computed. This range gain product can be related directly to the level of interference, and the sampled data can be evaluated to determine the percentage of time that the range gain product for all interference paths exceeds a given level.

TABLE 1


Symbols and definitions used in this Annex


a

Angular velocity of satellite in Earth-fixed coordinates

degrees/s

Bt

Transmit bandwidth

Hz

Ctraffic

Traffic coefficient depending on local time



D

Antenna diameter

m

E

Argument of latitude

degrees

epfd

Downlink equivalent power flux-density into earth station

dB(W/m2) in reference bandwidth

g

Acceleration due to Earth’s gravity

M/s2

G

Universal (Newtonian) gravitational constant

Nm2/kg2

Gt

Relative gain of transmit antenna



Gr

Relative gain of receive antenna



Grmax

Maximum gain of GSO FSS earth station receiving antenna



Grw

Maximum gain of wanted receive antenna



I

Inclination of satellite orbit

degrees

I0

Interference power

W

J2

Second harmonic Earth potential constant



k

Boltzmann’s constant

J/K

Lp

Polarization isolation factor



ms

Mass of satellite

kg

Me

Mass of the Earth

kg

N0

Noise power

W

Na

Number of transmitting non-GSO satellites visible from GSO FSS receiving earth station



Ncoarse

Integer ratio of coarse time step size to fine step size to define dual time step simulations



Nhits

Number of mainbeam-to-mainbeam coupling events between non-GSO satellite antenna and GSO FSS earth station antenna



Pt

RF power at input to transmitting antenna

W

r

Orbital radius of satellite

km

rc

Radius of non-GSO service area cell

km

rg

Radius of GSO

km

rn

Orbital radius of non-GSO satellite

km

R

Range between non-GSO satellite and GSO FSS earth station

m

Re

Radius of perfectly spherical Earth

km

T

Receiver noise temperature

K

TABLE 1 (end)




To

Orbit period

s

Tw

Wanted receiver noise temperature

K

t

Simulation time increment

s



Earth station elevation angle

degrees



Topocentric angle defining exclusion zone for non-GSO satellite switching strategy

degrees

coarse

Topocentric angle defining coarse step size in dual time-step simulation

degrees

FSR-1

Topocentric angle defining fine step region (FSR)

degrees

FSR-2

Topocentric angle defining boundary of exclusion zone

degrees



Antenna off-boresight angle

degrees

3

Antenna 3 dB beamwidth

degrees



Wavelength

m



Earth attraction constant

km3/s2

v

Constant velocity of satellite

degrees/s

ve

Orbital velocity of the Earth

degrees/m

vr

Orbital velocity of non-GSO satellite relative to the Earth’s surface

degrees/s

vn

Orbital velocity of non-GSO satellite

degrees/s



Angular velocity of satellite

degrees/s



Right ascension of the ascending node (RAAN)

degrees

0

RAAN at time t0

degrees

e

Rotational angular velocity of the Earth

degrees/s

r

Orbital precession rate of satellite

degrees/s



GSO arc avoidance switching angle

degrees

d

GSO arc avoidance switching angle desired at the edge of non-GSO service area cell

degrees

m

GSO arc avoidance angle to be modelled to achieve desired switching angle at edge of cell

degrees


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