1、 Rec. ITU-R S.1323-2 1 RECOMMENDATION ITU-R S.1323-2 Maximum permissible levels of interference in a satellite network (GSO/FSS; non-GSO/FSS; non-GSO/MSS feeder links)*in the fixed-satellite service caused by other codirectional FSS networks below 30 GHz (Questions ITU-R 205/4, ITU-R 206/4 and ITU-R
2、 231/4) (1997-2000-2002) The ITU Radiocommunication Assembly, considering a) that emissions from the earth stations as well as from the space station of a satellite network (geostationary-satellite orbit (GSO)/fixed-satellite service (FSS); non-GSO/FSS; non-GSO/mobile-satellite service (MSS) feeder
3、links) in the FSS may result in interference to another such network when both networks operate in the same bands; b) that the system designer and its operator should have control over the overall performance of a network and have the capability to provide the required quality of service; c) that it
4、 is necessary to protect a network of the FSS (GSO/FSS; non-GSO/FSS; non-GSO/MSS feeder links) from interference by other such networks and that the inclusion of additional link margin above that necessary to compensate for rain fading, e.g. to compensate for equipment aging, is not to be considered
5、 as part of that protection; d) that Article 5 of the Radio Regulations (RR), Nos. 5.441, 5.484A, 5.487A, 5.516 indicate that in certain frequency bands “Non-geostationary-satellite systems in the fixed-satellite service shall not claim protection from geostationary-satellite networks in the fixed-s
6、atellite service operating in accordance with the Radio Regulations, irrespective of the dates of receipt by the Bureau of the complete coordination or notification information, as appropriate, for the non-geostationary-satellite systems in the fixed-satellite service and of the complete coordinatio
7、n or notification information, as appropriate, for the geostationary-satellite networks, and No. 5.43A does not apply.”; e) that in the frequency bands specified in RR No. 22.5I, the limits contained therein apply to non-GSO FSS systems; f) that to allow an operator to exercise control over the qual
8、ity of service there needs to be a limit on the aggregate interference a network must be able to tolerate from emissions of all other networks; _ *The methodologies for determination of short-term interference criteria contained in this Recommendation are intended to address interference to GSO/FSS,
9、 non-GSO/FSS and non-GSO/MSS feeder links. However, the applicability of these methodologies for all such networks requires further verification. 2 Rec. ITU-R S.1323-2 g) that to limit the aggregate interference from all other networks, there needs to be a limit on the interference a network should
10、be expected to tolerate from any one other network and this single entry interference should allow accommodation of an appropriate number of interfering systems; h) that in frequency bands above 10 GHz where very high signal attenuation may occur for short periods of time, it may be desirable for sy
11、stems to make use of some form of fade compensation to counteract signal fading; j) that in interference situations involving non-GSO systems, FSS networks (GSO/FSS; non-GSO/FSS; non-GSO/MSS feeder links) are potentially exposed to high levels of interference for short periods of time which could af
12、fect the short-term performance or availability of these networks; k) that the long-term interference allowance from non-GSO systems to GSO FSS networks should be a small percentage of the existing long-term allowance into a GSO FSS network; and in addition to that allowance; l) that if not limited
13、short-term interference events may cause loss of synchronization or other unstable conditions even under clear-sky conditions which may cause a degradation or loss of service for periods longer than the interference event; m) that the permissible interference resulting from short-term interference e
14、vents has to be specified differently for FSS operation in different frequency bands due to the different propagation characteristics of signals in these different bands; n) that the effect of non-GSO interference into GSO systems that employ adaptive downlink coding is not the same as the effects d
15、ue to rain, and that studies performed so far indicate the need to consider these non-GSO interference effects on at least a per-beam basis (in the GSO system) rather than on a per-link basis; o) that propagation effects should account for no more than 90% of the unavailability of an FSS link, recom
16、mends 1 that a GSO FSS network operating in the frequency bands below 30 GHz should be designed and operated in such a manner that in any satellite link performance objectives can be met when the aggregate interfering power from the earth and space station emissions of all other GSO FSS networks ope
17、rating in the same frequency band or bands, assuming clear-sky conditions on the interference paths, does not exceed at the input to the demodulator: 1.1 25% of the total system noise power under clear-sky conditions when the network does not practice frequency reuse; 1.2 20% of the total system noi
18、se power under clear-sky conditions when the network does practice frequency reuse; 2 that for a GSO FSS network as mentioned in recommends 1, the internetwork interference caused by the earth and space station emissions of any one other GSO FSS network operating in the same frequency band or bands
19、should be limited to 6% of the total system noise power under clear-sky conditions; Rec. ITU-R S.1323-2 3 3 that for a GSO/FSS network the internetwork interference caused by the earth and space station emissions of all other satellite networks operating in the same frequency band and that can poten
20、tially cause interference of time-varying nature, should: 3.1 be responsible for at most 10% of the time allowance for the BER (or C/N value) specified in the short-term performance objectives of the desired network and corresponding to the shortest percentage of time (lowest C/N value); 3.2 in the
21、case of networks using adaptive coding, be responsible for at most a 10% decrease in the amount of reserve capacity available to links that require heavier coding to compensate for rain fading, on the assumption that the network maintains, with the use of this reserve capacity the same level of perf
22、ormance as it did with no time-varying interference present. Further studies are needed for bands other than 30/20 GHz; 4 that non-GSO FSS systems operating in frequency bands subject to RR Nos. 5.441, 5.484A, 5.487A and 5.516 should include in their interference budget, as a guide only, an allocati
23、on of 10% increase of the time allowance for the BER (or C/N value) specified in the short-term performance objectives of the desired network and corresponding to the shortest percentage of time (lowest C/N value) caused by the aggregate emissions from the earth and space stations of all GSO FSS net
24、works; 5 that for a non-GSO (non-GSO/FSS; non-GSO/MSS feeder links) network in frequency bands subject to RR No. 9.11A (which is not subject to the limits in RR Nos. 22.5C, 22.5D and 22.5F), the internetwork interference caused by the aggregate emissions from the earth and space stations of all GSO
25、FSS networks operating in the same frequency band should: 5.1 be responsible for at most 10% of the time allowance for the BER (or C/N value) specified in the short-term performance objectives of the desired network and corresponding to the shortest percentage of time (lowest C/N value); 5.2 in the
26、case of networks using adaptive coding, provisionally be responsible for at most a 10% (until review by further studies) decrease in the amount of reserve capacity available to links that require heavier coding to compensate for rain fading, on the assumption that the network maintains, with the use
27、 of this reserve capacity, the same level of performance as it did with no time-varying interference present. Further studies are needed to validate this approach for the case of interference from other non-GSO systems; 6 that for a non-GSO (non-GSO/FSS; non-GSO/MSS feeder links) network the interne
28、twork interference caused by the aggregate emissions from earth and space stations of all other non-GSO satellite networks operating in the same frequency band should: 6.1 be responsible for at most 10% of the time allowance for the BER (or C/N value) specified in the short-term performance objectiv
29、es of the desired network and corresponding to the shortest percentage of time (lowest C/N value); 6.2 in the case of networks using adaptive coding, provisionally be responsible for at most a 10% (until review by further studies) decrease in the amount of reserve capacity available to links that re
30、quire heavier coding to compensate for rain fading, on the assumption that the network 4 Rec. ITU-R S.1323-2 maintains, with the use of this reserve capacity, the same level of performance as it did with no time-varying interference present. Further studies are needed to validate this approach; 7 th
31、at, when applying Methodologies A and A described in Annex 1 or Procedure D described in Annex 2, there is no need for a long-term allowance to be defined because, since simultaneous effects of fading and interference are taken into consideration, then a full charac-terization of the interference ma
32、sk results from the conditions in recommends 3, 4, 5 and 6; 8 that, when applying Methodology B described in Annex 1, a long-term allowance should be additionally defined because simultaneous effects of fading and interference are not taken into account; 9 that this allowance corresponding to long-t
33、erm interference, when used in addition to recommends 3, 4, 5 and 6, should be expressed by requiring that the aggregate interference should not exceed 6% of the total system noise power for more than 10% of the time; 10 that the verification of whether the internetwork interference caused by the ea
34、rth and space station emissions of any given satellite network meets the requirements of recommends 3, 4, 5 and 6 (and recommends 9, where applicable) or the derivation of an interference mask (interference levels and maximum percentages of time for which such levels could be exceeded) that would le
35、ad to recommends 3, 4, 5 and 6 (and recommends 9, where applicable) being met may be conducted using the methodologies described in Annexes 1 and 2 in connection with an appropriate, assumed number of interfering networks; 11 that the maximum level of interference noise power caused to a GSO/FSS net
36、work should be calculated on the basis of the following values for the receiving earth station antenna gain, in a direction at an angle (degrees) referred to the main beam direction: for GSO to GSO interference: =18048 11.5) = 0.89158%Downlink P(z 11.5) = 0.73372%pdfDegradation (dB)5 Consideration o
37、f degradation due to fading in links with variable elevation angle In links to and from non-GSO satellites the degradation due to fading is also a function of the elevation angle . One approximate way of taking this into account consists in determining the pdf 14 Rec. ITU-R S.1323-2 of the degradati
38、on due to fading for the average elevation angle av. However, a more precise approach is to obtain the pdf p() of the elevation angle and then express the pdf px(X) of the degradation as: () ()()=20dZZpZXpXpxx(25) Example As an example, consider the interference between the uplinks of two non-GSO sa
39、tellite systems. The interfered with non-GSO system avoids in-line events employing a 10 avoidance angle. This avoidance angle is just sufficient for the total degradation z to meet the allowable time percentage. The victim uplink uses power control with a dynamic range of 6.8 dB with a clear sky li
40、nk margin of 1 dB and a heavy rain link margin of 0 dB. The corresponding pdf for the rain fading was therefore represented with an impulse at 0 dB corresponding to the probability of x (degradation due to fading) being between 0 and 5.8 dB and a second impulse at 1 dB corresponding to the probabili
41、ty of x exceeding 6.8 dB. Figure 3 shows the rain fade x and interference degradation y pdfs for the uplink interference, where the x distribution is based on the average elevation angle. The Crane rain model is used. Figure 4 shows the corresponding total degradation z, derived from the convolution
42、 of the x and y pdfs. 1323-03110110210310410102012xyFIGURE 3pdf of rain fade, x, and interference degradation, y, using Crane modeland weighted average elevation angle(LEOSAT-2 uplink, 10 avoidance angle)0.5 1.5 2.5pdfDegradation (dB)P(x 1) 1) = 0.25783%Threshold = 0.26792%Figure 5 shows the total d
43、egradation z distribution when the elevation angle distribution is used in generating the rain fade rather than using the average elevation angle. The total degradation just meets the time allowance, similarly to the results shown in Fig. 2. 1323-05102104110210610810100123FIGURE 5pdf of total degrad
44、ation, z, using Crane model and elevation angle distribution(LEOSAT-2 uplink, 10 avoidance angle)0.5 1.5 2.5 3.5pdfDegradation (dB)P(z 1) = 0.28159%Threshold = 0.29394%16 Rec. ITU-R S.1323-2 Other examples have confirmed that computing the degradation due to fading as proposed in equation (25), or b
45、asing this calculation on the average elevation angle av,leads to essentially identical results. This justifies the use of the simpler approach i.e. to compute the degradation due to fading based on the average angle av. A procedure to consider the time variation of the parameters of a non-GSO link
46、and also take into account any possible statistical dependence between fading and interference is described in Annex 3. 6 Examples of application of Methodology A We consider here a GSO downlink that is supposed to operate in such a way that the received C/N is above a threshold value (C/N)thrduring
47、 at least 99.9% of the time. It is assumed that the degradation due to fading includes the rain attenuation directly obtained from the Crane two-component model plus the effect of the increase in noise temperature due to rain. It is further assumed that the total downlink noise also includes interfe
48、rence (both intra-system and inter-system) and that the interference is faded by the same amount as the desired signal. The degradation X, expressed as a factor, is given by: ()()()/()1(/1)(10AARsysRLLLLLX+/+=(26)where: : fraction of the total downlink noise in clear-sky which is due to interference
49、 LR:attenuation due to rain T0 :mean absorption temperature (274.8 K) TB :background temperature (2.76 K for the sky) Tsys: downlink thermal noise temperature LA: loss due to atmospheric absorption (1.07, which corresponds to 0.3 dB). In order to be above a certain threshold (C/N )thrduring 99.9% of the time, the link is designed with a margin Xmax difference between (C/N )cs, and (C/N )thr such that p(x Xmax) = 0.09% (the remaining 0.01% will account for the effects of interference). Assuming an ea
