1、 Rec. ITU-R S.1592 1 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 R
2、adiocommunication 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) syst
3、ems 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 epfdin RR Tables 22-1A to 22-1D, single-entry operational limits to the epfdin RR Tables 22
4、-4A, 22-4B and 22-4C, and single-entry additional operational limits to the epfdinto 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 wi
5、ll 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 Recommen-dation ITU-R S.1503; d) that compliance of a proposed non-GSO FSS system with the single-entry operational limits to the
6、 epfd and, for certain antenna sizes, single-entry additional operational limits to the epfdis 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 operat
7、ional limits to the epfdare met, recognizing a) that administrations with assignments to GSO FSS networks in frequency bands where additional operational limits to the epfdhave been established require a reliable and independent means to determine whether a particular non-GSO FSS system is in compli
8、ance with the single-entry additional operational limits to the epfd, for their GSO FSS networks, 2 Rec. ITU-R S.1592 recommends 1 that the methodology defined in Annex 1 to this Recommendation, based on a full simu-lation of downlinks in a non-GSO FSS satellite system interfering into an operating
9、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 epfdin RR Article 22; 2 that the methodology in Annex 1 to this Recomm
10、endation, 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 An
11、nex 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 ap
12、proach 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
13、 their orbits and allows each space station and earth station to track their respective targets, while taking into account the Earths 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 ra
14、nge 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. _ *The methodology defined in Annex 1 currently applies to only non-GSO syste
15、ms using circular orbits. Further study is needed for non-circular orbits. Rec. ITU-R S.1592 3 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 Anten
16、na diameter m E Argument of latitude degrees epfdDownlink equivalent power flux-density into earth station dB(W/m2) in reference bandwidth g Acceleration due to Earths gravity M/s2 G Universal (Newtonian) gravitational constant Nm2/kg2 Gt Relative gain of transmit antenna GrRelative gain of receive
17、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 Boltzmanns constant J/K Lp Polarization isolation factor msMass of satellite
18、 kg Me Mass of the Earth kg N0 Noise power W NaNumber 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
19、-GSO satellite antenna and GSO FSS earth station antenna PtRF power at input to transmitting antenna W r Orbital radius of satellite km rcRadius 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
20、 Re Radius of perfectly spherical Earth km T Receiver noise temperature K 4 Rec. ITU-R S.1592 TABLE 1 (end) 2 Input parameters required In order for this methodology to be applied, the following input parameters will need to be provided by the non-GSO operator. Note that, in the absence of complete
21、information on all these parameters, this Recommendation gives some guidance on, for example, possible distributions of non-GSO FSS earth stations to be modelled in the simulations. 2.1 Orbit parameters Number of space stations Number of planes To Orbit period s Tw Wanted receiver noise temperature
22、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 (
23、FSR) degrees FSR-2 Topocentric angle defining boundary of exclusion zone degrees Antenna off-boresight angle degrees 3Antenna 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
24、 of non-GSO satellite relative to the Earths 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 prec
25、ession 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 Rec. ITU-R S.1592 5 For each o
26、rbital plane: orbit altitude inclination of plane longitude of the ascending node argument of latitude for each space station in the orbital plane. Precession. 2.2 Antenna parameters Non-GSO space stations: antenna radiation pattern maximum transmit gain (dBi) maximum number of co-frequency and co-p
27、olarization antenna beams and their spatial orientation. Non-GSO earth stations: antenna radiation pattern maximum receive gain (dBi) location (latitude, longitude). 2.3 Operational and computational parameters Frequency/polarization reuse plan, if used Minimum elevation angle for communication Simu
28、lation time period Simulation time step Implementation of downlink power control on range, if used by non-GSO system Implementation of GSO arc avoidance technique, if used by non-GSO system Traffic model, if appropriate (for example, see Fig. 9). 3 The orbital model The orbital model characterizes s
29、atellite motions in a geocentric inertial coordinate frame, shown in Fig. 1, the origin of which is at the centre of the Earth. The x axis is on the equatorial plane and points towards the vernal equinox (the first point in the constellation Aries), the z axis is the mean rotation axis of the Earth
30、and points towards the North Pole, and the y axis is determined as the cross product of the unit vectors in the z and x direction, i.e. = xzy. Extension of the equatorial plane to infinity, intersecting a hypothetical sphere of infinite radius (the celestial sphere), defines the celestial plane. 6 R
31、ec. ITU-R S.1592 1592-01zyEIFIGURE 1Representation of Keplerian orbital elementsx, (vernal equinox)Equatorial planeEarths centreOrbit planeThe orbital model is based on Newtons Laws of Motion for a satellite orbiting in a circle around a perfectly spherical Earth. This model is simple to implement s
32、ince the motion is characterized by a constant satellite orbital radius, r, and a constant velocity, v, which are related through Newtons Second Law of Motion: 22rmGMrmses= (1) where: ms : mass of the satellite v: constant velocity of the satellite G: universal gravitational constant (Nm2/kg2) r: or
33、bit radius Me : mass of the Earth (kg). Equation (1) can be written in the form: rRRGMrGMeeee222= (2) where Reis the radius of a perfectly spherical Earth (km). At the surface of the Earth, 2eeRmGMmg = (3) where g is the acceleration due to gravity at the Earths surface: 22m/seeRGMg = (4) Rec. ITU-R
34、 S.1592 7 and equation (2) can be rewritten in the form: rgRe= (5) The orbital period, To, is then given by the expression (Keplers Third Law): grRrTeo322 = (6) These equations describe completely the dynamics of circular orbital motion about a perfectly spherical Earth. The motion is characterized,
35、 in the geocentric coordinate system shown in Fig. 1, by specifying the position of the satellite using the Keplerian orbital parameters: : right ascension of the ascending node, i.e. where the satellite moves from south to north, of the orbit RAAN, measured from the x axis in the equatorial plane (
36、x-y plane); I : inclination of the orbit, i.e. the angle from the equatorial plane to the orbital plane of the satellite; and E : argument of latitude, i.e., the angle from the line of nodes (the line determined by the intersection of the orbital plane and the celestial equator) to the radius vector
37、 at the position of the satellite. The true anomaly, i.e. the angle on the plane of the satellites orbit between the perigee and the position of the satellite, as seen from the centre of the Earth, is a function of the angular position of the satellite at time t0and its angular velocity and can be e
38、xpressed as: tEE +=0(7) where: E0 : angular position of the satellite at time t0(degrees) r/= : angular velocity of the satellite (degrees/s). Similarly, the RAAN of an orbit can also be expressed as a function of time to account for orbital precession: tr+=0(8) where: 0 : RAAN of the satellite at t
39、ime t0(degrees) r : orbital precession rate of the satellite (degrees/s): 422)(cosJ23rrRIer= (9) where: : Earth attraction constant (km3/s2) J2: second harmonic Earth potential constant. 8 Rec. ITU-R S.1592 The position of the satellite can then be represented in terms of the geocentric inertial coo
40、rdinate system as: +=EIEIEEIErzyxsinsinsincoscoscossinsincossincoscos(10) and the velocity of the satellite is similarly represented in terms of the geocentric inertial coordinate system, ignoring the relatively long-term variation in , as +=EI EIEEIErdtdzdtdydtdxcossincoscoscossinsincoscossinsincos
41、/(11) 4 Calculation of interference In this methodology, the interference being considered is from the downlink of a non-GSO FSS satellite system into receiving earth stations operating to GSO FSS satellites. Figure 2 illustrates the geometry of the wanted and interference paths. 1592-0221FIGURE 2In
42、terference geometryGSO satelliteNon-GSO satelliteWanted signal pathsInterference signal pathIf power control is not used, the interference-to-noise ratio, I0/N0, can be determined from the following equation: 221222104)()(1414)()(RGGLBTkPLRGGBTkPNIrtpttprttt=0(12) Rec. ITU-R S.1592 9 where: Pt : ava
43、ilable transmit power (W) T: noise temperature of the receiver (K) Bt : transmit bandwidth (Hz) )(1tG: relative gain as a numerical ratio of the non-GSO satellite transmit antenna )(2rG: relative gain as a numerical ratio of the GSO FSS earth station receive antenna : wavelength of the transmitter (
44、m) R: interference path length (m) Lp : polarization isolation factor k: Boltzmanns constant (1.38 10 23J/K). The range gain product for the non-GSO satellite downlink into the earth station downlink from the GSO satellite is given by: 2214)()(RGGrt(13) If there is no path length compensating power
45、control on the links between the satellite and the earth station, this expression includes all the elements in equation (12) which may vary with time. The interference ratio, I0/N0, is then determined by multiplying the range gain product by the constant factor: pttLBTkP 142(14) If power control is
46、used on a non-GSO satellite to account for differences in range between the satellite and the earth station, then this must be taken into account in the simulation. The transmitting satellite reduces or increases its transmit power as it moves towards or away from the receiving earth station in orde
47、r to maintain constant power received at the non-GSO FSS earth station. The input parameter for the simulation is the desired receiver power density at the input to the wanted antenna, Pr(dB(W/Hz), which can be expressed as: 24)0()(=wtttrRGBRPP (15) where: Rw : wanted signal path length, i.e. the di
48、stance between the satellite and the earth station (m) Pt (R) : transmit power required to set up the link Prcan be related to the carrier-to-noise ratio at the wanted receiver: 2004)0()0()()0()(=wwrwtttwrwrRTkGGBRPTkGRPNC(16) 10 Rec. ITU-R S.1592 where: Grw (0) : maximum gain of the interfered with
49、 earth station receive antenna Tw : interfered with earth station receiver noise temperature (K). When power control on range is considered, the level of interference is determined from the following equation: pwtrtrprtttLTkRRGGGPLRGGBTkRPNI11)0()()(14)()()(22122100=(17) To assess the interference from non-GSO
