1、208 CCIR RECMN*738 72 4855232 0538828 700 W Rec. 738 RECOMMENDATION 738 PROCEDURE FOR DETERMiNiNG IF COORDINATION IS REQUIRED BETWEEN GEOSTATIONARYSATELLITE NETWORKS SHARING THE SAME FREQUENCY BANDS (Question 49/4) (1992) The CCIR, considering that FSS networks may share the same frequency bands; th
2、at they may cause and experience mutual interference; that this mutual interference can be minimized through coordination: that it is necessary to determine whether there is a need for coordination, a) b) c d recognizing that under Article 11 of the Radio Regulations, the need for coordination is de
3、termined by Appendix 29, recommends that the method given in Annex 1, called the ATIT method, be used to determine if coordination is required 1. between geostationary-satellite networks sharing the same frequency bands: 2. greater than 6%; 3. Note I - The AT/T method gives an apparent increase in e
4、quivalent satellite link noise temperature, and treats the effect of interference as an increase in thermal noise in the wanted network. The power of the interfering signal is assumed to be spread evenly over the frequency bandwidth, with a power density equal to its maximum power density. The ratio
5、 ATIT is expressed as a percentage. Note 2 - The above approach is similar to that in Appendix 29 of the Radio Regulations and is applicable with the data provided under Appendix 4 of the Radio Regulations. It also includes additional information to facilitate the application of Appendix 29. Note 3
6、- The threshold value of 6% is consistent with Appendix 29. that coordination be required when the calculated value of AT/T of the potentially interfered with network is that the following Notes will be considered part of this Recommendation. ANNEX 1 Method of calculation for determining if coordina
7、tion is required between geostationary-satellte networks sharing the same frequency bands 1. Characteristics of networks Radiocommunication satellites require frequency assignments in two bands, one for the up link and the other for the down link. It is current practice for frequency bands to be ass
8、ociated in pairs, one of each pair being used for up links and the other for down links. Case I below is concerned with the possibility of interference between two systems which have been assigned frequency bands in this way. However, it should be feasible to use a pair of frequency bands _. CCIR RE
9、CMN*738 92 4855212 0518829 647 H Rec. 738 209 in the reverse sense (bidirectional use) for some systems, the up-link band for one network being the same as the down-link band for the network using an adjacent satellite; this is Case II. These two cases cover all relative satellite positions from clo
10、sely-spaced to near-antipodal positions. Let A be a satellite link of network R associated with satellite S and A be a satellite link of network R associated with satellite S. The symbols such as a, b and c refer to satellite link A and symbols such as a, b and c refer to Satellite link A (see Figs.
11、 la and lb). FIGURE la Geometry - Case I -Wanted and interfering networks sharing the same frequency band in the same direction of transmission S S I Wanted network R Interfering network R The parameters are defined as follows (for satellite link A): T : the equivalent satellite link noise temperatu
12、re, referred to the output of the receiving antenna of the earth station (K); T,: the receiving system noise temperature of the space station, referred to the output of the receiving antenna of the space station (K); Te: the receiving system noise temperature of the earth station, referred to the ou
13、tput of the receiving antenna of the earth station (K); AT : apparent increase in the equivalent noise temperature for the entire satellite link referred to the output of the receiving earth station antenna, caused by interference emissions from other satellite networks: 210 Rec. 738 FIGURE lb Geome
14、try - Case II -Wanted and interfering networks sharing the same frequency band in opposite directions of transmission (bidirectional use) Wanted network R Interfering network R ATs : apparent increase in the rece,. -.ig system noise temperature a emission, referred to the output of the receiving ant
15、enna of this satellite (K); apparent increase in the receiving system noise temperature of the earth station eR, caused by an interfering emission, referred to the output of the receiving antenna of this station (K); maximum power density per Hz delivered to the antenna of satellite S (averaged over
16、 the worst 4 kz band for a carrier frequency below 15 GHz or over the worst 1 MHz band above 15 GHz) e satellite S, Caus% -y an interfeug ATe: ps: wm); g3(q) : transmitting antenna gain of satellite S in the direction q (numerical power ratio); q : qe : Note - The product psg3(qe) is the maximum e.i
17、.r.p. per Hz of satellite S in the direction of the receiving earth station eR of satellite link A, direction, from satellite S, of the receiving earth station eR of Satellite link A; direction, from satellite S, of the receiving earth station eR of satellite link A; CCIR RECMN*?38 92 4855232 053883
18、L 2T5 Rec. 738 211 Ils : pe: direction, from satellite S, of satellite S; maximum power density per Hz delivered to the antenna of the transmitting earth station eT (averaged over the worst 4 kHz band for a carrier frequency below 15 GKZ or over the worst 1 MHz band above 15 GHz) (WHz); g2() : recei
19、ving antenna gain of satellite S in the direction 6 (numerical power ratio): SA : 6d : 6d : direction, from satellite S, of the transmitting earth station eT of Satellite link A; direction, from satellite S, of the transmitting earth station eT of satellite link A: direction, from satellite S, of sa
20、tellite S; gi(cp) : transmitting antenna gain of the earth station eT in the direction of satellite S (numerical power ratio); g4(cp) : receiving antenna gain of the earth station t?R in the direction of satellite S (numerical power ratio): topocentric angular separation between the two satellites,
21、taking the longitudinal station-keeping tolerances into account. Note - Only the topocentric angle cp should be used in dealing with Case I: geocentric angular separation in degrees between the two satellites, taking the longitudinal station- keeping tolerance into account. Note - Only the geocentri
22、c angle pg should be used in dealing with Case II, Boltzmanns constant (1.38 x 10-23 JE): free-space transmission loss on the down link (numerical power ratio); evaluated from satellites to the receiving earth station eR for satellite link A; free-space transmission loss on the up link (numerical po
23、wer ratio): evaluated from the earth station eT to satellite S for satellite link A; free-space transmission loss on the inter-satellite link (numerical power ratio), evaluated from satellite S to satellite S; transmission gain of a specific satellite link subject to interference evaluated from the
24、output of the receiving antenna of the space station S to the output of the receiving antenna of the earth station eR (numerical power ratio, usually less than 1). In the foregoing symbols, the gains gi(q) and g4(cp) are those of the earth stations concerned. In the event of precise numerical data r
25、elating to earth-station antennas not being available, the reference radiation pattern given in Recommendation 465 should be used. 2. Calculation of the equivalent Satellite link noise temperature and the transmission gain 2.1 Introduction The purpose of this section is to provide some guidance for
26、determining, for simple frequency changing transponders, values of equivalent satellite link noise temperatures and transmission gains and in particular the sets of values for: - - the lowest equivalent link noise temperature and the associated transmission gain, and the value of transmission gain a
27、nd associated equivalent link noise temperature that correspond to the highest ratio of transmission gain to equivalent satellite link noise temperature. CCIR RECMN*738 92 4855212 0518832 131 W 212 Rec. 738 The equivalent satellite link-noise temperature T, referred to the output of the receiving an
28、tenna of the earth station, and the transmission gain y of a satellite link using simple frequency-changing transponders, can be determined in several ways. 2.2 General formulation 2.2.1 Method 1 The transmission gain is expressed as follows: where gi and g4 are the maximum (on-axis) transmitting an
29、d receiving earth station antenna gains, respectively (see Fig. la). 2.2.2 Method 2 The transmission gain is expressed as follows: The equivalent link noise temperature is expressed as follows: where: (CYNO) : up-link carrier-to-noise density ratio including only thermal and other background noises
30、(numerical ratio) (C/NO)d : down-iink carrier-to-noise density ratio including only thermal and other background noises (numerical ratio) totai link equivalent carrier-to-noise density ratio including intra-satellite impairment (intra- satellite interference, intermodulation), thermal and other back
31、ground noises (numerical ratio) e.i.r.p., : satellite saturation e.i.r.p. (W) h: the wavelength (m) of the up-link frequency BOi : transponder input back-off with respect to single carrier saturation (numerical value) BOo : transponder output back-off with respect to single carrier saturation (numer
32、ical value) W, : saturation power flux-density at the satellite (W/m2). The product of the satellite saturation power flux-density and the satellite receiving antenna gain (Le. W, . g2( let these links be called A and A respectively (the parameters such as a , b and 7 relate to link A. Then: In the
33、same way, the increase AT in the equivalent noise temperature for the entire satellite link referred to the output of the receiving antenna of the receiving earth station eR under the effect of the interference caused by network R is given by the following equations: When both satellites share the s
34、ame translation frequency, then When the two satellites have different translation frequencies (calling two links of the R network A and _ and denoting the corresponding parameters a, b andc): For the two multiple-access satellites this calculation must be made for each of the satellite links establ
35、ished via one satellite in relation to all of the satellite links established via the other satellite. If only the up link or the down link of the wanted satellite network shares a frequency band with the interfering satellite network, the value for AT should be obtained from equation (3) with eithe
36、r ATs or ATe having a zero value, as appropriate. Case II - Wanted and interfering networks sharing the same frequency band in opposite directions of transmission (bidirectional use) (see Fig. 1 b) Retaining the same notation the noise temperature increase ATs referred to the output of the receiving
37、 antenna of the satellite of link A is given by: The apparent increase in equivalent link noise temperature is then given by: CCIR RECMN*738 92 4855212 0518835 940 Rec. 738 215 The increase AT in the equivalent noise temperature of the link A caused by emissions from the satellite associated with th
38、e link A is given by: If only one band is shared by the two links A and A, interference between adjacent satellite links will occur only into the link which uses the shared band for its up link. Interference between earth stations associated with reverse-frequency assignment links is to be dealt wit
39、h by coordination procedures analogous to those used for coordination between earth and terrestrial stations. 4. Consideration of polarization isolation Polarization discrimination could also be used to reduce the probability of interference between satellite networks when different polarizations ar
40、e used. In this case, the apparent increase in the equivalent satellite link noise temperature could be determined by the foilowing expressions: - Case1 - Case11 where the definitions of y, ATs and ATe have been given previously and Yll, Yd and Yss are the polarization isolation factors (numerical r
41、atio) for the up link, down link and inter-satellite link, respectively. Values of the polarization isolation factors are contained in Appendix 29 of the Radio Regulations. These values have been a matter of further study (see Recommendation 736). Since the polarization isolation factors depend on t
42、he types of polarization used by each network and the statistical distribution of orthogonal polarization levels, the polarization isolation factor described above shall be considered only if the polarization has been notified or published as requested in Article 11 of the Radio Regulations. 5. Comp
43、arison between calculated and predetermined percentage increase in equivalent satellite link noise temperature In order to determine the largest value of ATIT it is necessary to insure that ail potential situations are included. Inter-satellite network interference may be largest in either the up li
44、nk or down link, thus sufficient data should be available to calculate both situations for each space-to-Earth service area and for each projected usage in accordance with Appendix 4 of the Radio Regulations. The AT/T expression is: AT ATe yATs T=T+T when yATs/T ATeIT, the highest ATIT value occurs
45、when ?IT is maximum. When ATeIT yATs/T, the highest ATIT occurs when Tis minimum. Thus, determinations need to be made using the values of y and T associated with the maximum value of ylT and using the minimum value of T and its associated value of y. The greater of the calculated CCIR RECMNr738 72
46、W 4855212 0518836 887 W 216 Rec. 738 values of AT/T and AT /T , expressed as a percentage, should be compared with the corresponding predetermined values. The predetermined values are taken as 6% of the appropriate equivalent satellite link noise temperature (see Radio Regulations, Appendix 29): - i
47、f the calculated value of ATIT is less than, or equal to, the predetermined one, the interference level from satellite link A to satellite link A is permissible irrespective of the modulation characteristics of the two satellite links and of the precise frequencies used; - if the calculated value of
48、 ATIT is greater than the predetermined one, a detailed calculation shall be carried out following the methods and techniques set out in Reports 388 and 455, during the coordination procedure between administrations. The comparison of AT/T with the predetermined value shall be carried out in a simil
49、ar manner. As an example, it can be seen that in the case of a satellite link operating in accordance with current CCIR Recommendations using FM telephony and having a total noise in a telephone channel of 10000 pWOp including 1 O00 pWOp interference noise from terrestrial radio-relay systems and 2 O00 pWOp interference noise from other satellite links, a 6% increase in equivalent noise temperature would correspond to up to 420 pWOp of interference noise. Since, for new networks advance published after 1987, the single-entry interfere
