1、 Rec. ITU-R S.1560 1 RECOMMENDATION ITU-R S.1560 Methodology for the calculation of the worst-case interference levels from a particular type of non-geostationary fixed-satellite service system using highly-elliptical orbits into geostationary fixed-satellite service satellite networks operating in
2、the 4/6 GHz frequency bands (Question ITU-R 236/4) (2002) The ITU Radiocommunication Assembly, considering a) that many fixed-satellite service (FSS) frequency bands, including the 4/6 GHz bands, may be used for both geostationary (GSO) satellite networks and non-GSO satellite systems in accordance
3、with the Radio Regulations (RR); b) in the 4/6 GHz bands non-GSO systems shall not cause unacceptable interference to GSO FSS networks in accordance with the provisions of RR No. 22.2; c) that administrations may need to calculate the worst-case interference level that is generated from a non-GSO sy
4、stem into any GSO network in the 4/6 GHz frequency bands; d) that the 4/6 GHz FSS frequency bands are heavily used by existing and planned GSO FSS networks, noting a) that information relating to non-GSO systems using highly-elliptical orbits in the FSS in frequency bands below 10 GHz has been recei
5、ved by the Radiocommunication Bureau; b) that RR No. 22.2 is an operational provision which is to be applied between adminis-trations, and it is up to the affected GSO FSS administration to determine whether a non-GSO FSS system is causing unacceptable interference to a GSO FSS network; c) that the
6、types of highly-elliptical orbit non-GSO FSS systems referenced in noting a) are characterized by the use of limited operational or “active” arcs that are spatially separated from the GSO as seen from the earth station, recommends 1 that the worst-case interference level, from a non-GSO FSS system o
7、f a type described in the notings above using highly-elliptical orbits into a GSO FSS network, be calculated by considering that all co-frequency non-GSO satellites from such a system that are transmitting towards the same geographic region of the Earth are producing their maximum power flux-density
8、 (pfd) levels; 2 that for non-GSO FSS systems operating in highly-elliptical orbits in the 4/6 GHz frequency bands, the methodology in Annex 1 to this Recommendation should be used for the calculation of the worst-case levels of interference into GSO FSS networks from non-GSO FSS 2 Rec. ITU-R S.1560
9、 systems where no transmissions to or from any non-GSO satellite are made within 40 of the GSO as viewed from any point on the Earths surface; 3 that this methodology may be used by administrations in assessing whether a non-GSO FSS system of a type described in the notings above would cause unaccep
10、table interference to a GSO FSS network. NOTE 1 Annex 2 gives an example of the use of the methodology of this Recommendation for a non-GSO FSS system of a type described in the notings above operating in sub-synchronous inclined elliptical orbits. NOTE 2 Further work is required to assess the aggre
11、gate interference from such non-GSO systems into GSO networks. NOTE 3 The methodology uses worst-case assumptions that overestimate the actual levels of interference. More refined analysis techniques could be used to assess the interference profiles in more detail. NOTE 4 The inclination of the GSO
12、satellite should be taken into account in the methodology of Annex 1. ANNEX 1 Methodology for the calculation of the worst-case interference levels from a particular type of non-GSO FSS system using highly-elliptical orbits into GSO FSS networks operating in the 4/6 GHz frequency bands The following
13、 methodology should be used for the calculation of the potential levels of interference into GSO networks operating in the 4/6 GHz frequency bands resulting from the co-frequency operation of particular types of non-GSO FSS system. The calculation methodology described in this Annex could overestima
14、te the actual levels of interference. In particular, for the downlink interference assessment, it is assumed that each of the transmitting non-GSO FSS satellites is located at the minimum angular separation from the line-of-sight (LoS) between the GSO earth station and its associated GSO satellite.
15、In a realistic situation, if one of the non-GSO satellites is located at this minimum angular separation, the other non-GSO satellites will be located at some larger angular separation and the interference contributions from these other satellites will be lower. Hence, the overall calculated T/T deg
16、radation would be less than those calculated using this methodology. For both the uplink and the downlink interference assessments, the number of transmitting satellites or earth stations used in this analysis of maximum interference is at the time when a handoff is occurring. This handoff will only
17、 occur for short periods of time (generally, about 0.1%) and will result in an overestimation of the maximum interference that would occur for the majority of the time. More refined analysis techniques could be used to assess the interference profiles in more detail. Rec. ITU-R S.1560 3 1 Data conce
18、rning the non-GSO system The following information is required concerning the non-GSO system: 1.1 Space-to-Earth transmissions D-min: Minimum angular separation of the active transmitting non-GSO satellites from the LoS between the GSO earth station and its associated GSO satellite (degrees). pfdD-n
19、on-GSO-max: Maximum pfd at the Earths surface caused by transmissions from each non-GSO satellite in the constellation (dB(W/(m2 1 Hz). ND: Maximum number of co-frequency non-GSO satellites transmitting towards the same geographic region of the Earth, as well as an indication of the number of such s
20、atellites as a function of the percentage of time. 1.2 Earth-to-space transmissions U-min: Minimum angular separation of the GSO from the LoS between the transmitting non-GSO earth station and its associated non-GSO satellite (degrees). e.i.r.p.non-GSO-max: Maximum off-axis equivalent isotropically
21、radiaded power (e.i.r.p.) spectral density from the transmitting non-GSO earth station corresponding to the minimum angular separation, U-min(dB(W/Hz). NU: Maximum number of co-frequency transmitting non-GSO earth stations within a geographic region of the Earth that is likely to be received by a si
22、ngle GSO satellite receive beam. 2 Data concerning the GSO network The following information is required concerning the GSO network: 2.1 Receive earth station sensitivity GGSO-ES-max: Assumed maximum off-axis gain of the GSO receive earth station in a direction corresponding to the minimum angular s
23、eparation, D-min, of the non-GSO satellite when it is actively transmitting (dBi). Recommendation ITU-R S.465 provides guidance in this respect. TGSO-ES: Assumed clear-sky receive system noise temperature (including receive antenna noise) of the GSO downlink. To err on the conservative side this nee
24、d not include degradations caused to the overall link resulting from the uplink (K). 2.2 Satellite receive sensitivity GGSO-SS-max: Assumed maximum GSO satellite receive antenna gain (dBi). TGSO-SS: Assumed clear-sky receive system noise temperature of the GSO uplink. To err on the conservative side
25、 this need not include the overall link including downlink (K). 4 Rec. ITU-R S.1560 3 Calculation of downlink interference into the GSO network The following three Steps are performed to calculate the degradation to the GSO network downlink receive system noise temperature from one non-GSO satellite
26、 system: Step D1: calculate the maximum interfering signal power spectral density (PSD), I0-ES, from a single non-GSO satellite at the GSO earth station antenna output: +=4log102-0 maxESGSOmaxGSOnonDESGpfdI dB(W/Hz) (1) where is the wavelength. Step D2: calculate the noise PSD, N0, at the GSO earth
27、station antenna output: N0-ES= 10 log (k TGSO-ES) dB(W/Hz) (2) where k is Boltzmanns constant. Step D3: calculate the degradation to downlink receive system noise temperature (T/TD) from the constellation of non-GSO satellites: =10-0-010/ESESNIDDNTT (3) 4 Calculation of uplink interference into the
28、GSO network The following four Steps are performed to calculate the degradation to the GSO network uplink receive system noise temperature from one non-GSO satellite system: Step U1: calculate the maximum pfd spectral density at the GSO space station (pfdU-non-GSO-max) from a single non-GSO transmit
29、ting earth station. Note that this equation assumes that the non-GSO transmitting earth station is located at the minimum distance from a GSO satellite. It should be noted that at this earth station location, the resultant separation angle will be greater than the minimum separation angle that is us
30、ed in the analysis. However, since even the minimum separation angle will be greater than 40, the reduction in the side lobe gain of the non-GSO earth stations antenna is unlikely to fully compensate for reduction in interference path loss. Thus, this will probably overestimate the interference that
31、 is received. )(2-)78635(4log10 =maxGSOnonmaxGSOnonUpriepfd (4) Step U2: calculate the interfering signal PSD, I0-SS, at the GSO space station antenna output: +=4log102-0 maxSSGSOmaxGSOnonUSSGpfdI (5) where is the wavelength. Rec. ITU-R S.1560 5 Step U3: calculate the noise PSD, N0, at the GSO space
32、 station antenna output: N0-SS= 10 log (k TGSO-SS) dB(W/Hz) (6) where k is Boltzmanns constant. Step U4: calculate the degradation to uplink receive system noise temperature, T/TU: =10-0-010/SSSSNIUUNTT (7) 5 Multiple non-GSO FSS systems The above methodology, if applied to the situation where there
33、 are multiple non-GSO FSS systems of this particular type operating in the 4/6 GHz frequency bands, would greatly overestimate the actual degradation to the GSO network uplink and downlink receive system noise temperatures from multiple non-GSO satellite systems. This is due to the fact that the min
34、imum angular separation from the GSO arc is assumed for each satellite. In a situation where there are multiple non-GSO systems of this type, the satellites would be distributed throughout each of the active arcs and very few would be at this minimum separation angle. As a result, this approach may
35、be used as a preliminary analysis tool for the case of multiple systems, but more detailed analysis that takes into account the locations of the satellites of each system in the active arcs would be necessary to evaluate the impact of the aggregate interference from multiple systems. ANNEX 2 Example
36、 of the application of the methodology in this Recommendation to the calculation of the worst-case interference levels from a particular type of non-GSO FSS system operating in sub-synchronous inclined highly elliptical orbits into GSO FSS networks in the 4/6 GHz frequency bands 1 Candidate non-GSO
37、system under consideration The type of non-GSO FSS system considered here proposes to use sub-synchronous inclined elliptical orbits in order to ensure a large angular separation of the active satellites from the GSO orbit. Such a system has been proposed as USAKU-H2 in ITU. This system is a highly-
38、elliptical orbit non-GSO FSS system that uses sub-synchronous inclined elliptical orbits in order to ensure a large angular separation of the active satellites from the GSO orbit. The system would provide FSS to all of the worlds populated land masses by means of its user and gateway links. Note tha
39、t this system proposes to utilize only gateway types of links in the 4/6 GHz frequency bands that are the 6 Rec. ITU-R S.1560 subject of this Recommendation. Such gateway links would use a relatively small number of large earth stations, which further minimizes any interference to GSO FSS networks.
40、A brief summary description of the system is given below, but more detailed information on this proposed system may be found in Recommendation ITU-R S.1328. The USAKU-H2 system is comprised of three five-satellite sub-constellations that have repeating ground tracks. Two of the five-satellite sub-co
41、nstellations follow separate ground tracks in the northern hemisphere, and the third sub-constellation follows a southern hemisphere ground track. The system is designed so that the satellites are active (i.e. transmit or retransmit and receive radiocommunication signals) only when in the portion of
42、 the orbit near apogee, where the satellite is travelling at the slowest rate of speed. These active arcs for each sub-constellation occur only when the satellites are at latitudes above 45 N for the northern hemisphere sub-constellations and 45 S for the southern hemisphere sub-constellation. The s
43、ystem design is such that there are three active arcs for each sub-constellation, and that none of the active arcs cross each other. At any point in time for each sub-constellation/ground track, there will be one satellite in each of the three active arcs and two satellites that are not within the a
44、ctive arcs. It should be noted that there are times when there will be two satellites in a given active arc (one at the beginning and one at the end) in order to perform housekeeping and handover activities. This system design results in the active satellites being separated from the GSO LoS by at l
45、east 40 at all times. The USAKU-H2 system thus achieves an optimized combination of very high elevation angles, low signal propagation delays compared to GSO satellites, limited satellite handoffs, and high angular separation from the GSO orbit. It also provides non-uniform distribution of capacity
46、to the northern and southern hemispheres in proportion with demand. Fig. 1 shows the sub-satellite ground tracks of the USAKU-H2 system, with the active service arcs indicated by the bold lines. 1560-01FIGURE 1Sub-satellite ground tracks of the USAKU-H2 systemRec. ITU-R S.1560 7 2 Frequency bands Th
47、e USAKU-H2 system is proposed to operate its gateway links in the 5 925-6 725 MHz (Earth-to-space) and 3 700-4 200 MHz frequency bands (space-to-Earth). Each USAKU-H2 satellite provides bent-pipe communications channels in these bands between its gateway links in these bands and its user links that
48、operate in other frequency bands. 3 Key parameters for calculation of interference to GSO FSS networks in the 4/6 GHz frequency bands For the type of non-GSO system considered in this Recommendation the following parameters are necessary for the assessment of interference into co-frequency GSO FSS n
49、etworks: 3.1 Downlink interference into GSO networks D1: Minimum angular separation of the active transmitting non-GSO satellites from the LoS between the GSO earth station and its associated GSO satellite. D2: Maximum pfd at the Earths surface caused by transmissions from each non-GSO satellite in the constellation. D3: Maximum number of co-frequency non-GSO satellites transmitting towards the same geographic region of the Earth, as well as an indication of the number of such sa
