1、76 Earth station Rec. ITU-R SA.1163-2 -194.0 dBW per 100 Hz() RECOMMENDATION ITU-R SA. 1 163-2 INTERFERENCE CRITERIA FOR SERVICE LINKS IN DATA COLLECTION SYSTEMS IN THE EARTH EXPLORATION-SATELLITE AND METEOROLOGICALSATELLITE SERVICES (Question ITU-R 142/7) (1995-1997-1999) The ITU Radiocommunication
2、 Assembly, considering a) that the hypothetical reference system specified in Recommendation ITU-R SA. 1020 defines links for data collection, and data collection platform interrogation; b) that interference criteria are needed to ensure that systems can be designed to achieve adequate performance i
3、n the presence of interference; c) that the interference criteria may be determined using the methodology described in Recommendation ITU-R SA. 1022 and the performance objectives listed in Recommendation ITU-R SA. 1 162; d) that interference criteria assists in the development of criteria for shari
4、ng bands among systems, including those operating in other services; e) that systems in the Earth exploration-satellite (including meteorological-satellite) service must accept an interference threshold at least as high as the threshold of permissible interference; f) that Annex 1 presents the param
5、eters of representative systems that provide the basis for permissible levels of interference for pertinent transmissions in the Earth exploration-satellite service, recommends 1 that the interference levels specified in Table 1 be used as the permissible total levels of interfering signal power at
6、the antenna output of stations operating for service links in the Earth exploration-satellite and meteoro- logical-satellite services. TABLE 1 Interference criteria for service links of stations in the Earth exploration-satellite and meteorological-satellite services Frequency band (MHz) 40 1-403 Ea
7、rth-to-space 137-138 space-to-Earth 40 1-403 Earth-to-space 1670-1 690 space-to-Earth Function and type of earth station Non-GSO data collection, low-gain antenna Non-GSO data collection, command and data acquisition (CDA) station GSO data collection, low-gain antenna GSO data collection, CDA statio
8、n Station subject to interference Space station interfering signal power (dBW) in the reference bandwidth to be exceeded no more than 20% of the time -178.8 dBW per 1 600 Hd) Earth station -158.3 dBW per 8.32 kHz() -187.4 dBW per 100 Hd2) Interfering signal power (dBW) in the reference bandwidth to
9、be exceeded no more thanp% of the time -174.7 dBW per i 600 Hd) p=o.1 _ -151.1 dBW per 8.32 kHz() p = 0.1 -173.4 dBW per 100 Hd3) -181.5 dBW per 100 Hd3) p = 0.025 p = 0.1 COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services= 4855212 053hb
10、Ob 2TT Ten. !TLT-? s 4.1153-2 TABLE 1 (end) GSO data collection Earth station -187.3 dBW per 100 Hz() 1 platform interrogation 77 Function and type of earth station Frequency band (MHz) Station subject to interference 2025-2110 Earth-to-space 460-470 space-to Earth I I GSO data collection, CDA stati
11、on Interfering signal power (dBW) in the reference bandwidth to be exceeded no more than 20% of the time -188.9 dBW per 100 HA2) Interfering signal power (dBW) in the reference bandwidth to be exceeded no more thanp% of the time -183.7 dBW per 100 Hz() p = 0.025 -182.1 dBW per 100 HA3) p = 0.1 () Th
12、e interfering signal powers (dBW) in the reference bandwidths are specified for reception at elevation angles 5“. (*) The interfering signal powers (dBW) in the reference bandwidths are specified for reception at elevation angles 3“. (3) The interfering signal powers (dBW) in the reference bandwidth
13、s are specified for reception at elevation angles OO. NOTE 1 - The total interfering signal power level that may be exceeded for no more than x% of the time, where x is less than 20% but greater than the specified short-term time percentage p% of the time), may be determined by interpolation between
14、 the specified values using a logarithmic scale (base 1 O) for percentage of time and a linear scale for interfering signal power density (dB). NOTE 2 - Although the interference criteria are based on the systems described in Annex 1, the interference criteria apply to all systems that operate in th
15、e subject frequency bands and which provide the specified service functions. NOTE 3 -The interference criteria are specified with respect to the percentage of time of reception by the earth station. Thus, receiver performance statistics associated with reception from or by one particular satellite (
16、Le., cumulative distribution of bit error rate (BER) are the same as the statistics for reception from several similar satellites. The total time of reception includes time periods associated with signal acquisition (Le. before and during local ascension of the satellite), receiver synchronization t
17、o the data, and synchronized reception of data. Consequently, for interrogation by satellites in low-Earth orbit, the time required for initial signal acquisition and synchronization may constitute up to several tens of seconds out of total satellite visibility periods averaging on the a small perce
18、ntage of time p, p I i%) assume that the satellite is located at the minimum elevation angle associated with the applicable performance objective. This yields the BER performance exceeded for all but p% of the time because EdNo and BER are monotonically related to elevation angle. NOTE 4 - The eleva
19、tion angle exceeded for all but 20% of the time during reception is well approximated by the angle exceeded for all but 20% of the time that the satellite is visible above the minimum elevation angle specified in the performance objective. This approximation is made in the performance analyses prese
20、nted in hex 1 because the underlying cumulative time error cannot exceed 1% (.e. p% of the time) and the associated total error in satellite antenna gain, free space loss, excess path loss, and earth station parameter values are negligible. The resulting elevation angle that is exceeded for all but
21、20% of the time of reception yields the BER performance exceeded for all but 20% of the time because EdNo and BER are monotonically related to elevation angle. NOTE 5 - Data collection platform interrogation from non-GSO satellites will be available in the near future. I order of 9 min. However, the
22、 analyses of short-term performance that are presented in Annex 1 (Le., performance exceeded for all but ANNEX 1 Basis for interference criteria 1 Introduction This Annex presents the parameters used as inputs to the methodology described in Recommendation ITU-R SA. 1022 to determine the interferenc
23、e criteria. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services4855232 053bb07 33b = 78 Ree. ITU-R SA4.i!63-3 2 Meteorological-satellite service in the 401-403 MHz band uplink 2.1 ARGOS interfering critena The ARGOS data collection system
24、 (DCS) uplink (see Fig. 2) transmits split-phase, Manchester-encoded, phase-shift keyed (PSK) signals through satellites in low-Earth orbit and operates at a 400 bids data transmission rate. The data collection platform (DCP) typically uses a low-gain (5 dBi maximum at 20“ elevation angle) antenna a
25、nd can be a mobile or fixed platform. The satellite DCS processor regenerates the uplink DCS data, multiplexes the data with other telemetry, and transmits the digital data to the ground in the 137-138 MHz band. Because of the DCS data regeneration in the satellite, downlink performance can be separ
26、ated fiom uplink performance in deriving interference criteria. Figure 1 provides statistics of the ARGOS DCS uplink power measured at the satellite receiver. Table 2 provides the basis for developments of the ARGOS interference criteria. FIGURE 1 ARGOS DCS uplink (measurements) 1 O0 90 80 70 60 50
27、40 30 20 10 n “ -167 -165 - 160 - 155 - 150 - 145 -140 -138 Received signal power (dBW) 1163-01 COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services= Y855212 053bb08 072 Short-term (O. 1%) uplink received power Long-term (20%) uplink recei
28、ved power Rec. ITU-R SA.1163-2 -167 dBW From Fig. 1 -161 dBW From Fig. i 79 Short-term uplink C/NO Long-term uplink C/NO TABLE 2 33.8 dB/Hz 39.8 dB/Hz System performance used as a basis for DCS interference criteria when using low orbiting satellites Required uplink C/NO Short-term uplink margin Par
29、ameter 38.8 dB/Hz BER= i x 10-5 2 dB implementation loss 1 .O dB modulation loss -5.0 dB I Value I Long-term uplink interference criterion Short-term uplink interference criterion Downlink e.i.r.p. -178.8 dB(W/1.6 WZ) -174.7 dB(W/1.6 WZ) -17.5 dBW q = 1/3, Mmin = 1.2 dB q = 1, Mmin = 1.0 dB I Uplink
30、 noise temperature I 600 K I Downlink loss Downlink G/T 145.8 dB -5.6 dB(Kl) Data rate Required downlink C/NO Downlink margin I Long-term uplink margin 8.32 biffs 53.4 dB/Hz BER= 1 x lo4 3 dB implementation loss 0.7 dB modulation loss 6.3 dB I 1.0 dB I Noise power density Long-term downlink interfer
31、ence criterion -195.4 dB(W/Hz) - 1 5 8.3 dB( W/8.3 2 kHz) q= 1/3 Short-term downlink interference criterion I Downlink C/NO -151.1 dB(W/8.32 Hz) q=l I 59.7dB/Hz I 2.2 Interference to the GOES DCPR links DCPs in the GOES DCS transmit Manchester-encoded BPSK signals (DCP reports) in the 401-403 MHz ba
32、nd to the GOES satellite at a data rate of 100 bits. The satellite relays these DCP reports (DCPR) to the CDA station in the 1 670- 1 690 MHz band. The satellite transponder, which is channelized to accommodate several hundred simultaneous DCPR transmissions, has an automatic gain control (AGC) that
33、 maintains the downlink DCPR e.i.r.p. constant regardless of the transponder input power. Because the DCPR data are not regenerated in the satellite, the DCPR signals must share this fixed downlink power with interfering signals that enter the satellite transponder in the 401-403 MHz band. Moreover,
34、 interfering signals transmitted directly into the CDA station in the 1 670-1 690 MHz band will further affect DCPR performance. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services4655232 0536609 TO7 9 80 Rec. ITU-R SA.1163-2 The signal p
35、ower received at the CDA station fiom a DCP via the GOES satellite is: where: El : GI: G2 : LI and L2: Gs: DCP e.i.r.p. satellite receive antenna gain CDA station receive antenna gain uplink and downlink losses satellite gain (excluding the satellite receive antenna). The noise power density and int
36、erference power density at the input to the CDA station receiver are respectively: No =k L2 qw+T2) where: TI and T2: satellite and station system noise temperatures 101 and 102: interference power densities transmitted into the satellite and into the CDA station k Boltzmanns constant. Figure 2 illus
37、trates these parameters. FIGURE 2 GOES DCPR link parameters Gain, G, - e.r.p., E2 Interference, i, (Gm, Loss, L, e.i.r.p., E, / Loss, L, I DCP I - Interference, 1, 1163-02 COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesFrom these equa
38、tions, the carrier-to-noise plus interference density ratio at the input to the station receiver can be determined Because the satellite e.i.r.p., 2, is maintained constant by the AGC, Gs varies with the transponder input power as follows: where the denominator is the transponder input power. P is t
39、he sum of the DCP e.i.r.p.s accessing the satellite transponder, and B is the transponder bandwidth. To avoid the need to consider a variety of possible DCP locations, it is assumed that Gl/Ll is the same for all DCPR links. It will be assumed that the interference allocation at the station receiver
40、 is such that a fraction p is received via the satellite and a fraction 1 - p is transmitted directly into the CDA station. Then: From Recommendation ITU-R SA. 1022, the carrier-to-noise plus interference density ratio can be expressed as: e- - M-4 c No + Io NO where M is the interference-free margi
41、n, and q is the fraction of the interference-free margin that is allowed to be consumed by the interference. From the foregoing equations: (G/T), ik L - c - I L2 E(G/T)l + kB E2(G/T)2 LI No 1+ is the interference-free carrier-to-noise density ratio, and: r is the factor by which interference degrade
42、s C/NO. The permissible interference density at the satellite receiver input is therefore Io1 = k T, QI, where: COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services. _ e.i.r.p. of a single DCP in the channel (dBW) 4 = 11855212 053bb11 667
43、Number of DCPs having this e.i.r.p. in the channel Number of DCPs having this e.i.r.p. or less O O 82 Rec. ITU-R SA.1163-2 9 5 where Mmjn is the smallest interference-free margin for which only a fraction q of the margin is consumed by the interference. Correspondingly, the permissible interference
44、density transmitted directly into the CDA station receiver in the 1 690-1 700 MHz band is 102 = k T2 Q2, where: 13 Individual DCPs assigned to a given DCPR channel time-share that channel, the bandwidth of which is 1.5 kHz. Measurements of DCP e.i.r.p. in one GOES DCPR channel over a 24 h period hav
45、e provided the statistics summarized in Table 3. Assuming that all DCPs assigned to a given channel time-share the channel equally, these data show that 20% of the time the e.i.r.p. will be 11 dBW or less, and that 0.1% of the time the e.i.r.p. will be 5 dBW or less. Permissible long-term interferen
46、ce will therefore be based on a short-term e.i.r.p. of 5 dBW, and permissible short-term interference will be based on a long-term e.i.r.p. of 11 dBW. 14 15 i6 TABLE 3 DCPR e.i.r.p. statistics 28 98 36 134 46 180 18 5 5 219 3 19 3 1 220 6 1 4 7 4 8 8 O 8 10 17 30 11 12 42 12 12 54 I 17 I 34 I 214 22
47、0 I 20 I O I Table 4 lists the values of the link parameters assumed in the calculation of the permissible interference densities Io1 and 102. To determine the total DCP e.i.r.p., the number of DCPR channels being occupied simultaneously must be postulated. Assuming an average DCP e.i.r.p. of 15 dBW
48、, and assuming that 100 DCPR channels are simultaneously active, the sum P of the DCP e.i.r.p.s will be 35 dBW. Assume also that the interference allocation at the station receiver COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services= 4855
49、232 O53bbL2 5T3 D E, (short-term) El(long-term) P 83 5 dBW 11 dBW 35 dBW 100 DCS channels From measured e.i.r.p. statistics From measured e.i.r.p. statistics is split 50-50 between that received via the satellite and that transmitted directly into the station receiver, so thatp = 1/2. Assume finally that q = 113 and Mmjn = 1.2 dB for long-term interference, and that q = 1 and Mmjn = 1.2 dB for short-term interference. Then, substituting the values from Table 4 into the equations given above for the interference densities, it is found that the interf
