1、CCIR RECMN*1002 93 W Y855212 0520916 54T W Rec. ITU-R S.1002 77 RECOMMENDATION ITU-R S.1002 ORBIT MANAGEMENT TECHNIQUES FOR THE FIXED-SATELLITE SERVICE (Question ITU-R 49/4 (1990)* (1993) The ITU Radiocommunication Assembly, considering that there is a need to manage portions of the geostationary-sa
2、tellite orbit (GSO) in order to achieve an that it is advantageous to develop one or more sets of generalized parameters which could be used to that the generalized parameters can be modelled accurately by one or more computer programs to aid in the that there are currently computer programs which c
3、an assist in the management and use of the orbit, a) efficient utilization of both the GSO and the radio spectrum; b) adequately describe fixed-satellite networks in order to facilitate the orbit management process; c) management of the orbit; d) recommends that to assist in orbit management of a po
4、rtion of the GSO, generalized parameters may be used as described that efficient computer algorithms which optimize the use of the orbit, as given in Annex 2 may be used. 1. in Annex 1; 2. Generaiized satellite network parameters for orbit management 1. Introduction Studies have been made to quantif
5、y the benefits of introducing an optimization process for identifying orbitai positions for new networks through example exercises. The results of exercises indicate that, if the positions for new networks had been selected at random and non-optimized positions had been selected, a significant advan
6、tage would have been forgone by comparison with a selection made using the optimization process. Moreover, particularly with a large number of existing networks, the optimization process can result in savings of time and effort in inter-system coordination activity. The orbit management process ther
7、efore consists of identifying a set of generalized parameters and developing efficient computer algorithms and implementation methodologies. 2. Method based on A, B, C and D parameters 2.1 Network parameters A, B, C und D The A, B, C, D generalized parameters specify the interference-producing capab
8、ility (variables A and c and the interference sensitivity (variables B and D) of a satellite network. * Former CCIR Question 4914. CCIR RECMN*1002 93 Y855212 05209l17 486 W 78 Rec. lTU-R S.1002 Since many different combinations of implementation parameters (such as antenna characteristics and transm
9、itter powers) can result in a similar set of parametric values, it can be applied irrespective of the modulation characteristics and specific frequency used. The generalized parameters selected by the World Administrative Radio Conference on the use of the Geostationary-Satellite Orbit and on the Pl
10、anning of Space Services Utilizing It (Geneva, 1988) (WARC ORB-88) for the allotment plan are the A, B, C, D parameters based on power density averaged over the signal bandwidth. The purpose of this set is to generalize not only the standard parameters used, but also the type of traffic assumed in t
11、he allotment plan. Under this concept, the required input powers into the standard earth station and the particular space station antennas are first determined during the planning process. These are then converted into power density (Pl and Pz (dB(W/Hz) by dividing by the bandwidth of the signal typ
12、e, which is in turn used to compute and record the plans generalized, A, B, C and D parameters. The equations shown below describe the A, B, C, D generalized parameters where: A : uplink off-axis e.i.r.p. density averaged over the necessary bandwidth of the modulated carrier B : uplink off-axis rece
13、iver sensitivity* to interfering e.i.r.p. density averaged over the necessary bandwidth of the modulated carrier C : downlink off-axis e.i.r.p. density averaged over the necessary bandwidth of the modulated carrier D : downlink off-axis receiver sensitivity* to interfering e.i.r.p. density averaged
14、over the necessary bandwidth of the modulated carrier where: pl : gi : gi(q) : 82 : g2() : Agz(y9 = g2 / g2 (w) : p3 : power density, averaged over the necessary bandwidth of the modulated carrier, fed into the transmitting earth station antenna (WkIz) maximum gain of the earth station transmitting
15、antenna (numerical power ratio) earth station transmitting antenna radiation pattern (numerical power ratio) maximum gain of the space station receiving antenna gain in the space station receiving antenna in the direction of the earth station (numerical power ratio) discrimination of the space stati
16、on receiving antenna (numerical power ratio) power density, averaged over the necessary bandwidth of the modulated carrier, fed into the space station transmitting antenna (Whiz) maximum space station transmitting antenna gain (numerical power ratio) space station transmitting antenna gain in the di
17、rection of the earth station g3 : g3(w) : * Note that here the meaning is susceptibility to interference rather than the precise technical definition of sensitivity. CCIR RECMN*kL002 93 W 4855232 0520918 312 = Rec. lTU-R S.1002 79 Ag3(y) = g3 I g3(y) : discrimination of the space station transmittin
18、g antenna (numerical power ratio) g4 : maximum gain of the earth station receiving antenna (numerical power ratio) g4(p) : earth station receiving antenna radiation pattern (numerical power ratio) (prime) : denotes parameters for the interfering network. Thus, the equation for the ratio of the wante
19、d power density to unwanted power density (as defined above), is given by: reducing simply to: where (c/r) hence, the signals used in the system must enable operation when (C/O c (C/OF1. An increase in the value of one of these parameters may be offset by a reduction in the value of the other, in ac
20、cordance with the relationship: When the condition A S Apl is respected, tbe power radiated by the earth station, pl, can be reduced by way of a corresponding increase in the gain of the earth station antenna, gi, i.e., in the size of the antenna reflector. Here, gl(q) will increase in the area of t
21、he main beam of the earth station antenna pattern but, gl(cp) will not change in the area of the sidelobes. The interference caused to the space stations of other systems will not be altered or reduced. The parameter B will not be affected, in other words there will be no deterioration in the system
22、s noise immunity on the uplink. If the same earth-station antenna is used for reception, then its gain on reception g4 will increase, and the parameter D will be reduced in the area of the sidelobes, but the systems noise immunity with respect to interfering CCIR RECMN*LUU2 93 4855212 0520922 843 W
23、Rec. ITU-R S.1002 83 satellites located within the main beam of the antenna pattern will remain unchanged. If it is applied in a system with a relatively large service area, such a modification of the parameters pl and g1, g4 makes the systems more uniform, and is usuaily advantageous from the econo
24、mic viewpoint. Increasing gl, 94 is effective in cases where the magnitude of B and D needs to be reduced outside the main beam. The same effect may also be achieved by reducing g2() and g4(p) in the area of the sidelobes by way of more sophisticated antenna design. The need to improve the values of
25、 B and D may arise at the stage of converting an allotment into an assignment, due to the fact that the values of these parameters obtained (even if they correspond to the planned values Bpi, D,i) are insufficient to achieve the (C/l)z required for the signal transmission methods used in the system.
26、 Similar modification of the actual parameters p3 (reduction) and g3 (increase, i.e., an increase in the dimensions of the space station transmitting antenna) also results in a reduction in radiated power (C) outside the main beam; this reduction is brought about not only by the reduction in p3 but
27、also in g3(yf). However, such a modification is constrained by a reduction in service area. 3. Method based on the use of isolation Two isolation methods, conventional isolation and link isolation, are described in Annex 4 of Recommendation ITU-R S.740* . The following process is described for the l
28、ink isolation but is equally applicable for the conventional isolation method. Orbital positions for entering satellites are identified using the following optimizing sequence: Phase 1 The available link isolation matrices for ail possible combinations of entering networks and for all possible combi
29、nations of the existing and entering networks are generated. Figure 1 schematically shows an example of the link isolation matrix corresponding to the interference from the network J to the network I. The lowest value among all elements of the link isolation matrix implies the minimum available link
30、 isolation ALZmjn (I, J) for the interference from the network J to the network I. In the same way, the minimum link isolation ALImjn (JI I) from the network I to the network J can be derived. Phase 2 The calculation of the minimum available isolation among the existing and entering networks is made
31、 following the above-mentioned procedure, using the preferred orbital locations submitted by the administrations for the new networks. Phase 3 An ordering of the entering networks is determined using the evolutional model. In this model, the best ordering for ail entering networks in the given arran
32、gement of the existing networks is determined under an assumed launching sequence for the entering networks and a given link isolation criterion which is in excess of the required link isolation of a high proportion of carrier combinations. Phase 4 For the satellite ordering as determined above, fur
33、ther adjustment of the positions of new entrants is undertaken such that the minimum available isolation in the most affected network is maximized on the basis of the following objective function: where: I, J ?belong to? ail existing and entering networks. * Former CCIR Recommendation 740. CCIR RECM
34、N*3002 93 4855232 0520923 7T = 84 Transponder number of wanted network J Rec. ITU-R S.1002 FIGURE la Link isolation matrix No.1 No. 2 Transponder number of wanted network I No. 1 Link isolation for No. 2 Link isolation for Jll + I21 JI2 -+ I21 JI1 -+ I22 Ji2 + 122 Link isolation for J2i + I21 522 +
35、I21 J21 -+ I22 J22 -+ 122 FIGURE lb Assumed link connections No. 1 No. 2 Link Links Il I21 122 No. 1 No. 2 Links Links Jll J12 J2i In 4. Method based on the use of normalized ATIT In this method, the available normalized ATIT for each carrier type classified in accordance with Annex 1 of Recommendat
36、ion ITU-R S.739* is used. The optimization process is carried out in the following way: Phase 1 Identification of possible cases of interference. * Former CCIR Recommendation 739. CCIR RECNN*L002 93 D 4855232 0520924 616 Rec. U-R S.1002 85 Phase 2 In the case of network pairs deployed in a potential
37、 interference configuration, comparison of satellite antenna radiation patterns and service areas for determination of cross-gains (gain of one satellite antenna in the direction of an earth station in the other network) for the worst-case earth station sites. Phase 3 Determination of relative noise
38、 temperature increases for each network pair in a potential interference si tua tion. Phase 4 Determination of required spacings between satellites by comparing relative temperature increases computed in phase 3 with maximum acceptable increases defined in Table 3 (Annex 3 of Report 454 (Annex to Vo
39、lume IV of the ex-CCIR. (Dsseldorf, 1990), taking into account a 25 log p decrease in earth station antenna sidelobes: where: cpij required : required spacing between the two satellites under consideration - pij : spacing used in phase 3 computations (new satellites located at the mid-point of their
40、 service arc) (ATIT), : relative temperature increase computed in phase 3 (ATIT), : maximum acceptable relative temperature increase for the carriers involved. The required spacing for a satellite pair is the maximum value obtained from applying equation (2) to all carrier pairs which might be in an
41、 interference configuration. Phase 5 Determination of orbital locations of new satellites in order to maximize the ratios of the available orbitai spacing to the required spacing among the satellite population. This optimization process is equivalent to minimizing the relative excess of interference
42、 in the most affected network, expressed by the ratio between the available normalized (ATIT), to the required value (AT1T)n. Therefore the objective function is: 5. Method based on the use of Characteristic Orbital Spacing (COS) The process of choosing tentative orbit positions for new satellite ne
43、tworks and then making minor modifications to these tentative positions can be carried out to reduce the problems caused by the timing of the individual stages. When the complete coordination of the network takes place within a five year time-frame and the construction of the space station is simila
44、rly time-consuming, the overall process can be done in three phases, as follows: Phase 1 Initial tentative choice of orbital position CCIR RECMN*L002 93 4855212 0520925 552 = 86 RW. ITU-R S.1002 Sub-phase 1.1 Choose an arc within which the new or replacement satellite might be coordinated and operat
45、ed. This arc should be wide enough so that it is highly likely that a solution can be found, but not larger than necessary because the complexity of the problem increases as the number of satellites in the arc considered increases. Sub-phase 1.2 Calculate the generalized parameters qii for each of t
46、he existing networks in the arc being considered, and the new network. Also calculate the parameters qij relating to the interaction between network i and network j (94 is defined as the spacing between networks i and j necessary to protect network i a specified amount from network j). Sub-phase 1.3
47、 Use the q matrix of sub-phase 1.2 to find an orbital arrangement among the networks involved to allow the new networks to be included in the arc under consideration. If no position can be found the arc under consideration must be widened and/or the parameters used to determine the qg matrix must be
48、 tightened. Sub-phase 1.3 is then repeated. Phase 2 Detailed coordination of networks at the orbit positions chosen in phase 1 under Article 11 of the Radio Regulations is carried out in this phase. This includes traffic coordination and timing of traffic introduction as required, imposing constrain
49、ts on earth station antenna characteristics and location as necessary, etc. Phase 3 This phase is unnecessaq if phase 2 can be completed successfully. If, however, it is not possible, phase 1 is carried out again with the pij elements reduced to find an orbital arrangement within which phase 2 can be completed successfully. 6. Method based on the principie of network homogeneity Two mutually affected FSS networks are inhomogeneous when the first network requires more protection against interference from the second than the second requires against interference from
