1、 Rec. ITU-R SF.1843 1 RECOMMENDATION ITU-R SF.1843 Methodology for determining the power level for high altitude platform stations ground terminals to facilitate sharing with space station receivers in the bands 47.2-47.5 GHz and 47.9-48.2 GHz (2007) Scope This Recommendation presents a methodology
2、and its applications to determine the power level for the ground terminals of HAPS to promote frequency sharing with an FSS space station receiver in the bands 47.2-47.5 GHz and 47.9-48.2 GHz. The ITU Radiocommunication Assembly, considering a) that new technology is being developed utilizing teleco
3、mmunication relays located on high altitude platform stations; b) that WRC-97 made provision for the operation of high altitude platform stations (HAPS), also known as stratospheric repeaters, within the fixed service in the bands 47.2-47.5 GHz and 47.9-48.2 GHz; c) that the bands 47.2-47.5 GHz and
4、47.9-48.2 GHz are allocated to the fixed-satellite service (FSS) in the Earth-to-space direction; d) that ITU-R was invited to study, as a matter of urgency, power limitations applicable for HAPS ground stations to facilitate sharing with space stations receivers; e) that because systems in the FS u
5、sing HAPS can use the full range of elevation angles, sharing with the FSS may present difficulties; f) that Recommendation ITU-R F.1500 contains the characteristics of systems in the fixed service using HAPS, recognizing a) that according to No. 5.552A of the Radio Regulations (RR), the allocation
6、to the FS in the bands above, is designated for use by HAPS, recommends 1 that the methodology given in Annex 1 should be used to determine the maximum level of transmit power applicable for HAPS ground terminals to facilitate sharing with space station receivers in the bands 47.2-47.5 GHz and 47.9-
7、48.2 GHz, in the ground-to-HAPS direction. 2 Rec. ITU-R SF.1843 Annex 1 Methodology 1 System characteristics 1.1 The high altitude platform system The parameters used in this analysis are given in Recommendation ITU-R F.1500 and are as follows: TABLE 1 HAPS coverage zones (platform at 21 km) Coverag
8、e area Elevation angles (degrees) Ground range (km) UAC(1)90-30 0-36 SAC(2)30-15 36-76.5 RAC(3)15-5 76.5-203 (1)UAC: Urban area coverage. (2)SAC: Suburban area coverage. (3)RAC: Rural area coverage. TABLE 2 Ground terminal transmitter parameters Communication to Transmitter power density(dB(W/2 MHz)
9、 Antenna gain (dBi) UAC(1)8.2 23 SAC(2)7 38 RAC(3)1.5 38 (1)UAC: Urban area coverage. (2)SAC: Suburban area coverage. (3)RAC: Rural area coverage. Rec. ITU-R SF.1843 3 1.2 GSO FSS satellite station The parameters used in this analysis are given in Recommendation ITU-R SF.1481-1 and are as follows: T
10、ABLE 3 GSO FSS satellite parameters Maximum antenna gain (dBi) 51.8 Interference criterion (dB(W/MHz) 150.5 Antenna pattern Recommendation ITU-R S.672-4 2 Interference analysis This section investigates interference from HAPS ground terminals into an FSS space station receiver. For the aggregate int
11、erference analysis, the HAPS coverage areas are populated with ground terminals and the interference received at the FSS space station is calculated for a number of trials, where each trial corresponds to a random distribution of HAPS ground terminals in full distribution based on Recommendations IT
12、U-R F.1500 and ITU-R SF.1481-1. The parameters of HAPS ground terminals used in the analysis are shown in Table 4. It is assumed that a fully loaded platform would be able to support 100 co-channel ground terminals in each of the three coverage areas and that the main lobe of a receiving antenna bea
13、m pattern of an FSS space station receiver is always directed to the nadir of HAPS to consider the sharing condition. TABLE 4 Transmitting parameters of HAPS ground terminals Coverage area RAC SAC UAC Range of elevation angles (degrees) 5-15 15-30 30-90 Number of ground terminals 100 100 100 Antenna
14、 gain (dBi) 38 38 23 Power (dBW) 1.5 7 8.2 Channel bandwidth (MHz) 2 2 2 4 Rec. ITU-R SF.1843 In this analysis, the interference scenario is assumed as shown in Fig. 1. The earth station is located at the nadir (the centre of HAPS coverage) and the satellite is located at latitude = 0 and longitude
15、= 0, while the position of HAPS coverage is varied with only the latitude (longitude = 0). The expected received power density at the space station receiver can be calculated by equation (1) as used in Recommendation ITU-R SF.1481-1: Pr= P + Gt Ltf+ Gr Lrf La Lp 10 log B 20 log (4d/) 60 dB(W/MHz) (1
16、) where: Pr: expected received carrier power density (dB(W/MHz) : transmitting output power density (dB(W/MHz) Gt: transmitting antenna gain (dBi) Ltf: antenna feeder loss (dB) Gr: gain of the receiving antenna (dBi) Lrf: receiving antenna feeder loss (dB) a: atmospheric absorption for a particular
17、elevation angle (dB) Lp: attenuation due to other propagation effects (dB) B: bandwidth (MHz) d: distance of signal path (km) : wavelength (m). Rec. ITU-R SF.1843 5 The bandwidth of HAPS ground terminals is assumed to be 2 MHz as described in Recommendation ITU-R F.1500. For the antenna beam pattern
18、s of HAPS ground terminals, Recommendations ITU-R F.1245 and F.699 are referred to. Taking into account the maximum antenna gains described in Table 4, antenna beam patterns for cases where the ratio between the antenna diameter and the wavelength is less than or equal to 100, in both Recommendation
19、s above, are considered. As an example of the antenna beam patterns, Fig. 2 shows the antenna beam pattern from Recommendation ITU-R F.1245 has a lower side lobe than that from Recommendation ITU-R F.699. Figure 3 shows an example of the interference cumulative distribution function (CDF) with the l
20、atitude of a HAPS platform and earth station of the satellite for 1 000 trials, with the parameters based on Table 4. In this example the antenna beam pattern of Recommendation ITU-R F.699-6 was used for HAPS ground terminals. If the interference criterion for the FSS space station is 150.5 dB(W/MHz
21、) as mentioned in Recommendation ITU-R SF.1481, all cases with the latitude exceed the interference criterion. For situations below 70 latitude, as the latitude becomes higher, the interference from HAPS ground terminals into the FSS space station is increased. If the latitude is above 70, the inter
22、ference is decreased again. Figure 4 shows the CDF difference using the antenna beam patterns of Recommendations ITU-R F.699 and F.1245. The result shows HAPS ground terminals with the antenna beam pattern of Recommendation ITU-R F.1245 give less interference to the space station receiver than those
23、 with the antenna beam pattern of Recommendation ITU-R F.699 at the same latitude. 6 Rec. ITU-R SF.1843 Rec. ITU-R SF.1843 7 3 Transmitting power level of HAPS ground terminals To reduce interference power from HAPS ground terminals to the FSS space station, the maximum power level from the ground t
24、erminals should be specified. This section shows examples to specify the maximum power level from the ground terminals of HAPS with antenna beam patterns mentioned in Recommendations ITU-R F.699 and F.1245. The power reduction of the HAPS ground terminals given in Recommendation ITU-R F.1500 is carr
25、ied out so that interference avoidance of HAPS ground terminals with FSS space stations can be achieved even in co-coverage areas. It is assumed that HAPS ground terminals have a power control scheme. As shown in Figs. 3 and 4, since the interference is different from the latitude of HAPS nadir and
26、the antenna beam patterns of HAPS ground terminals, it is necessary to specify the appropriate power with the latitude and antenna beam pattern. Table 5 shows the parameters for the HAPS ground terminals with the power reduction when the antenna beam pattern of Recommendation ITU-R F.699 is applied
27、to the HAPS ground terminals. In the cases of C and D in the Table, HAPS ground terminals in SAC and RAC are excluded since the possibility that main beams of HAPS ground terminals are directed to the FSS space station receiver is increased due to the low elevation angle in higher latitude. TABLE 5
28、Sharing parameters with latitude of HAPS nadir (using the antenna beam pattern of Recommendation ITU-R F.699) UAC SAC RAC Case Latitude of HAPS and SAT ES Transmitter parameters Elevation angles (90-30) Elevation angles (30-15) Elevation angles (15-5) Number of ground terminals 100 100 100 Antenna g
29、ain 23 dBi 38 dBi 38 dBi A 0 30 Power 13.2 dBW 7 dBW 1.5 dBW Number of ground terminals 100 100 100 Antenna gain 23 dBi 38 dBi 38 dBi B 30 50 Power 13.2 dBW 12 dBW 6.5 dBW Number of ground terminals 100 Antenna gain 23 dBi C 50 58 Power 13.2 dBW Number of ground terminals 100 Antenna gain 23 dBi D 5
30、8 Power 8.2 dBW Remark Case A: 5 dB power reduction only in UAC. Case B: 5 dB power reduction in all. Case C: 5 dB power reduction in UAC with no users in SAC and RAC. Case D: No power reduction with no users in SAC and RAC. 8 Rec. ITU-R SF.1843 Table 6 shows the parameters for the HAPS ground termi
31、nals with the power reduction when the antenna beam pattern of Recommendation ITU-R F.1245 is applied to the HAPS ground terminals. Due to the same reason as stated above, in the cases of C and D in the Table, HAPS ground terminals in SAC and RAC are also excluded. TABLE 6 Sharing parameters with la
32、titude of HAPS nadir (using the antenna beam pattern of Recommendation ITU-R F.1245) UAC SAC RAC Case Latitude of HAPS and SAT ES Transmitter parameters Elevation angles (90-30) Elevation angles (30-15) Elevation angles (15-5) Number of ground terminals 100 100 100 Antenna gain 23 dBi 38 dBi 38 dBi
33、A 0 30 Power 10.7 dBW 7 dBW 1.5 dBW Number of ground terminals 100 100 100 Antenna gain 23 dBi 38 dBi 38 dBi B 30 50 Power 12.2 dBW 11 dBW 5.5 dBW Number of ground terminals 100 Antenna gain 23 dBi C 50 58 Power 10.7 dBW Number of ground terminals 100 Antenna gain 23 dBi D 58 Power 8.2 dBW Remark Ca
34、se A: 2.5 dB power reduction only in UAC. Case B: 4 dB power reduction in all. Case C: 2.5 dB power reduction in UAC with no users in SAC and RAC. Case D: No power reduction with no users in SAC and RAC. Figure 5 shows the possibility of interference avoidance of HAPS ground terminals with an FSS sp
35、ace station by up to 5 dB power reduction of HAPS ground terminals. Figure 6 shows the possibility of interference avoidance of HAPS ground terminals with an FSS space station by up to 4 dB power reduction of HAPS ground terminals. For the low latitude (below 30) the power of HAPS ground terminals i
36、n UAC is an important factor, but for high latitude (above 30) those in SAC and RAC are the dominant factor. Figures 5 and 6 show that all cases do not exceed the interference criterion. Rec. ITU-R SF.1843 9 10 Rec. ITU-R SF.1843 If HAPS ground terminals are equipped with a power control system, the
37、y can reduce the transmit power in clear-sky conditions, not exceeding the interference criterion of the FSS space station receiver in a co-coverage area. In clear-sky conditions, the reduction can be achieved up to the amounts of rain attenuation given in Recommendation ITU-R F.1500, e.g. 11.2 dB,
38、14.9 dB and 22.4 dB in UAC, SAC and RAC, respectively. In this analysis, the power reduction (for example: maximum 5 dB in the case of the parameters in Table 5, maximum 4 dB in Table 6) is assumed to show the possibility of interference avoidance in a co-coverage area. The reduction would be applic
39、able in co-coverage areas. In rainy conditions, the reduced power would be restored. 4 Summary This Annex presents a methodology and its applications to determine the power level for the ground terminals of HAPS to promote frequency sharing between HAPS ground terminals and an FSS space station in t
40、he bands 47.2-47.5 GHz and 47.9-48.2 GHz. Power reduction can meet the interference criterion, when the parameters shown in Tables 5 and 6 are used (i.e. power control range of 5 dB). In summary, this Annex shows the possibility of interference avoidance of an FSS space station receiver from HAPS ground terminals equipped with a power control range of 5 dB.
