1、 Rec. ITU-R M.1642-2 1 RECOMMENDATION ITU-R M.1642-2 Methodology for assessing the maximum aggregate equivalent power flux-density at an aeronautical radionavigation service station from all radionavigation-satellite service systems operating in the 1 164-1 215 MHz band (2003-2005-2007) Scope This R
2、ecommendation gives a methodology and the reference antenna characteristics for assessing the maximum aggregate equivalent power flux-density (epfd) level produced at the input of a station of the aeronautical radionavigation service (ARNS) by all radionavigation-satellite service (RNSS) systems ope
3、rating in any portion of the 1 164-1 215 MHz band. The ITU Radiocommunication Assembly, considering a) that in accordance with the Radio Regulations (RR), the band 960-1 215 MHz is allocated on a primary basis to the aeronautical radionavigation service (ARNS) in all the ITU Regions; b) that analyse
4、s show that RNSS signals in the 1 164-1 215 MHz band can be designed not to cause interference to the DME/TACAN ARNS receivers operating in this band; c) that a protection criterion for the ARNS has been developed and is expressed in terms of equivalent power flux-density (epfd), which is set out in
5、 Recommendation ITU-R M.1639, recognizing a) that WRC-2000 introduced a co-primary allocation for the RNSS in the frequency band 1 164-1 215 MHz, subject to conditions that require the RNSS to protect the ARNS from harmful interference; b) that WRC-03 determined that protection of the ARNS from RNSS
6、 can be achieved if the value of the epfd produced by all the space stations of all RNSS (space-to-Earth) systems in the band 1 164-1 215 MHz does not exceed the level of 121.5 dB(W/m2) in any 1 MHz band, and adopted Resolution 609 (WRC-03) in order to ensure that this level is not exceeded; c) that
7、 the ARNS is a safety service in accordance with RR No. 1.59 and special measures need to be taken by Administrations to protect these services in accordance with provision RR No. 4.10, recommends 1 that the methodology in Annex 1 and the reference ARNS characteristics in Annex 2 should be used to c
8、alculate the maximum aggregate epfd produced by emissions from all RNSS systems at any aeronautical radionavigation station. 2 Rec. ITU-R M.1642-2 Annex 1 Methodology for assessing the maximum aggregate epfd at an ARNS station from all RNSS systems operating in the 1 164-1 215 MHz band Summary of th
9、e method With the method described in this Annex it is possible to calculate the maximum aggregate epfd level of all RNSS systems in the band 1 164-1 215 MHz. This method allows different systems to be combined easily, so that the effect of changes such as including or excluding one or various syste
10、ms or the effect of changing the characteristics of specific systems can be examined during a consultation meeting. The method accommodates both non-GSO systems, with constellations of satellites in any orbits of any inclination, and GSO systems. The method is based on a two-step process: Step 1: Ca
11、lculation of the epfd of each individual RNSS system. This step may be performed by each operator independently prior to the consultation meeting, provided that results are submitted in a compatible format (see 1.3, for non-GSO systems, and 1.4, for GSO systems). Step 2: Combination of the maximum e
12、pfd of the individual systems, by superposition of the maps, if necessary at different frequencies, to obtain the maximum aggregate epfd (see 2) in the band 1 164-1 215 MHz. Description of the method 1 Method for calculating the maximum epfd from satellites of one RNSS system 1.1 Definition of epfd
13、The definition of equivalent power flux-density (epfd) is based upon RR No. 22.5C.1 as adopted at WRC-2000. When an antenna receives power, within its reference bandwidth, simultaneously from transmitters at various distances, in various directions and at various levels of incident pfd, the epfd is
14、that pfd which, if received from a single transmitter in the far field of the antenna in the direction of maximum gain, would produce the same power at the input of the receiver as is actually received from the aggregate of the various transmitters. The instantaneous epfd is calculated using the fol
15、lowing formula: =aiiNimaxriritPGGdGepfd1,1010)(4)(10log102where: Na: number of space stations that are visible from the receiver i : index of the space station considered Rec. ITU-R M.1642-2 3 Pi: RF power (in the reference bandwidth) at the input of the antenna (or RF radiated power in the case of
16、an active antenna) of the transmitting space station (dB(W/MHz) i: off-axis angle (degrees) between the boresight of the transmitting space station and the direction of the receiver Gt(i) : transmit antenna gain (as a ratio) of the space station in the direction of the receiver di: distance (m) betw
17、een the transmitting station and the receiver i: off-axis angle (degrees) between the pointing direction of the receiver and the direction of the transmitting space station Gr(i) : receive antenna gain (as a ratio) of the receiver, in the direction of the transmitting space station (see Annex 2) Gr,
18、 max: maximum gain (as a ratio) of the receiver epfd : instantaneous equivalent power flux-density (dB(W/(m2 MHz) at the receiver. NOTE 1 It is assumed that each transmitter is located in the far field of the receiver (that is, at a distance greater than 2D2/, where D is the effective diameter of th
19、e receiver antenna and is the observing wavelength in the same unit). In the case under consideration this will always be satisfied. 1.2 General consideration In the first step of the method, the maximum epfd for each constellation of RNSS satellites is calculated at each latitude and longitude over
20、 the whole surface of the Earth for each 1 MHz of spectrum occupied by the system. As the victim ARNS receiver may be mounted on an aircraft flying at an altitude up to 40 000 ft (12 192 m) (see 2 of Annex 2), the calculation should include all satellites with elevation angles from 90 down to 3.54.
21、Calculation of the epfd distribution of each system is only necessary at a single reference frequency, preferably the frequency at which signal power is maximum. The RNSS signal spectral shape should be supplied to a consultation meeting, so that results of the calculation can then be multiplied by
22、the appropriate spectral shaping factors to obtain the results at any other frequency. 1.3 Method for calculating the maximum epfd for a non-GSO RNSS system The simulation methodology given in Appendix 1 to Annex 1, which is based entirely on Recommendation ITU-R S.1325, may be used to accomplish th
23、is. The methodology, given in Appendix 2 to Annex 1, is based entirely on an analytical technique. The method could be used for obtaining prompt estimates but it does not yield an exact upper bound result. 1.4 Method for calculating the maximum epfd for a GSO RNSS system The maximum epfd for each GS
24、O satellite is required to be calculated at each latitude and longitude over the whole surface of the Earth for each 1 MHz of spectrum occupied by the system. In this case the epfd will not be dependent on time, so a single table of results can be calculated directly. 4 Rec. ITU-R M.1642-2 2 Method
25、for calculating the maximum aggregate epfd from all RNSS systems 2.1 Data required for each system Each non-GSO RNSS system not having a geosynchronous period will, having followed the methodology of 1.3, provide a consultation meeting with a list of maximum epfd versus latitude (applicable at all l
26、ongitudes) and a signal spectral shape. Each non-GSO RNSS system having a geosynchronous period will, having followed the methodology of 1.3, provide a consultation meeting with a list of maximum epfd versus latitude and longitude, and a signal spectral shape. Each GSO RNSS system will, having follo
27、wed the methodology of 1.4, provide a consultation meeting with a table of maximum epfd versus latitude and longitude and a signal spectral shape. 2.2 Combination of epfds of systems with similar signal characteristics The determination of aggregate epfd of RNSS systems with the same frequency of si
28、gnal spectral maximum may be achieved using three steps: Step 1a: point-by-point summation of maximum epfds in the 1 MHz of the band where the signal has maximum power at each latitude of all the non-GSO (not having a geosynchronous period) lists to obtain the list of non-GSO (not having a geosynchr
29、onous period) aggregate epfd versus latitude; Step 1b: point-by-point summation of maximum epfds in the 1 MHz of the band where the signal has maximum power at each latitude and longitude of all the non-GSO (having a geosynchronous period) lists to obtain the list of non-GSO (having a geosynchronous
30、 period) aggregate epfd versus latitude and longitude; Step 2: point-by-point summation of maximum epfds in the 1 MHz of the band where the signal has maximum power at each point of latitude and longitude of all the GSO tables to obtain the table of GSO aggregate epfd versus latitude and longitude;
31、Step 3: point-by-point summation of the list of non-GSO (not having a geosynchronous period) aggregate epfd versus latitude, and the list of non-GSO (having a geosynchronous period) aggregate epfd versus latitude and longitude to each longitude column of the table of GSO aggregate epfd versus latitu
32、de and longitude to obtain the overall the table of aggregate epfd versus latitude and longitude. Examination of the highest epfd in this table will reveal whether the protection criterion in Recommendation ITU-R M.1639 in any 1 MHz of the band is respected. 2.3 Combination of epfds of systems with
33、different signal characteristics It should be noted that the maximum aggregate epfd will be frequency dependent. If the spectra of all the RNSS systems under consideration have their maxima at the same frequency, a single analysis will suffice. However, if different systems have different maxima, ei
34、ther because they use different centre frequencies with overlapping spectra or because they use different modulation techniques, then analysis of the maximum aggregate epfd will require frequency to be taken into account. The determination of maximum aggregate epfd of RNSS systems with different cen
35、tre frequencies will require, as a minimum, the above three steps to be performed at each frequency for which any one system has its signal spectral maximum, and may also require analysis at intermediate frequencies. For each frequency, each list or table will be factored by the appropriate spectral
36、 shaping factor before summation with other lists and tables. Rec. ITU-R M.1642-2 5 Examination of the highest epfd in all of the resultant tables will reveal whether protection criterion in Recommendation ITU-R M.1639 in any 1 MHz of the band is respected. 2.4 Check of results Following determinati
37、on of the maximum aggregate epfd, a single simultaneous simulation of all RNSS systems at the ARNS station location where the absolute maximum aggregate epfd was determined may be considered to confirm results obtained using Appendix 1 or 2 to Annex 1. Appendix 1 to Annex 1 A simulation methodology
38、for determining the maximum epfd for a non-GSO RNSS system 1 Method and simulation approach description The framework for this methodology based on Recommendation ITU-R S.1325 is to model all the satellites of one RNSS system at a specific reference frequency (typically the 1 MHz portion of the 1 16
39、4-1 215 MHz band with the maximum RNSS signal spectral density). A simulation of the constellation is sampled over a period of time at a relatively fine rate. At each sample the epfd is computed for all latitude and longitude points. The maximum sample should be recorded for each latitude and longit
40、ude point. Other samples may be discarded. The result is a table, which can be shown as a map, as illustrated in Figs. 5 and 6. Following this, the maximum epfd, for each latitude should be determined, which will eliminate approximations due to limited simulation time. 2 Simulation assumptions 2.1 O
41、rbit model The orbit models to simulate the space stations in their orbits are for circular and elliptical orbits only accounting for precession of the line of nodes in the equatorial plane due to asphericity of the Earth. The orbit model represents satellite motion in a geocentric inertial coordina
42、te frame shown in Fig. 1. The origin of this inertial frame is at the centre of the Earth. The x-axis points to the first point in the constellation Aries (i.e. vernal equinox), the z-axis is the mean rotation axis of the Earth, and the y-axis is determined as the cross product of the unit vectors i
43、n the z and x direction, i.e. xzyrrr= . The orbital models are based on Newtons equation of motion for a satellite orbiting a perfectly spherical Earth in a circle and in an ellipse. For the non-GSO system using circular orbit, the characteristics of this motion that make it easy to model is that th
44、e satellite orbital radius and velocity are constant. 6 Rec. ITU-R M.1642-2 2.1.1 Earth-related constants For the Earth, the general constants are: Re: Earth radius (6 378.137 km) O : Earth centre : Earth attraction constant (3.986005 105km3/s2) J2: second harmonic Earth potential constant (1 082.63
45、 106) Te: Earth rotation period (23 h 56 4.0989“ = 86 164.0989 s) e: Earth rotation angular velocity = 2/Te 7.2921151467 105rad/s t : elapsed time since the simulated epoch (s). 2.1.2 Non-GSO satellite system space station related constants For the non-GSO satellite system space stations using circu
46、lar orbits (see Fig. 1), the constants are as follows: N : number of space stations of the non-GSO system i : index for each of the non-GSO satellites (0 i N) hsat: satellite altitude above the Earth (km) r : radius of the satellite orbit (km) = hsat+ ReI : inclination angle of the orbital plane abo
47、ve the Equator (rad) RAAN : right ascension of the ascending node i,0: RAAN of the i-th non-GSO satellite at the time t (rad) ui,0: argument of latitude of the i-th non-GSO satellite at the time t (rad) T : satellite orbit period (s) = 2 (r3/)1/2n : mean motion of a satellite (rad/s) = 2/T ui,t: arg
48、ument of latitude of the i-th satellite at the time t (rad) = ui,0+ ntr: nodal regression of the ascending node (rad/s) = 422)cos(J23rrRIei,t: RAAN of the i-th satellite at the time t (rad) = i,0+ rt :iON coordinate vector (inertial coordinate system) of a non-GSO satellite in the Earth-centred fixe
49、d coordinate frame: +=)sin()sin()cos()sin()cos()sin()cos()sin()sin()cos()cos()cos(,IuuIuuIurzyxONtititititititititiiiiiRec. ITU-R M.1642-2 7 For the non-GSO satellite system space stations using elliptical orbits (see Figs. 2 and 3), the constants are as follows: N : number of space stations of the non-GSO system i : index for each of the non-GSO satellites (0 i N) ai: semi-major axis of the i-th satellite (km) ei: eccentricity of the i-th satellite Mi,0: mean anomaly of th
