1、Rec. ITU-R M.1456 1 RECOMMENDATION ITU-R M.1456* MINLMUM PERFORMANCE CHARACTERISTICS AND OPERATIONAL CONDITIONS FOR HIGH ALTITUDE PLATFORM STATIONS PROVLDING LMT-2000 IN THE BANDS 1 885-1 980 MHz, 2 010-2 025 MHz AND 2 110-2 170 MHz IN REGIONS 1 AND 3 AND 1885-1 980 MHz AND 2 110-2 160 MHz IN REGION
2、 2* (2000) The ITU Radiocommunication Assembly, considering a) wireless access using the proposed IMT-2000 terrestrial component radio transmission technologies and protocols; that high altitude platform stations (HAPS)* have the possibility of delivering IMT-2000 mobile and fixed b) services to cov
3、erage areas that range in size from metropolitan to wider areas; that each HAPS uses a phased array antenna to project hundreds of spot beams to provide telecommunication cl that for non-HAPS terrestrial systems, such as tower-based systems, the illumination of areas outside the intended operational
4、 area is dependent on the characteristics of the tower-mounted antenna and the propagation attenuation. For HAPS, the dependence is more on the characteristics of the HAPS mounted antenna especially the side- lobe performance and pointing accuracy. As the coverage area of a HAPS increases the antenn
5、a performance becomes more demanding; d) that the characteristics of Co-channel sharing and coordination between HAPS systems and other IMT-2000 systems are determined by the performance of the HAPS antennas, the IMT-2000 radio interface used by the HAPS and the HAPS coverage area; e) that the level
6、s of out-of-band interference from HAPS into receiving mobile earth stations, fixed stations, space science stations and mobile stations operating in adjacent channels can be reduced by the HAPS use of filters or guardbands to limit out-of-band (OoB) emission levels; f) worldwide to the fixed servic
7、e and the mobile service; that the bands 1885-1 980 MHz, 2010-2025 MHz and 2 110-2 170 MHz are allocated on a primary basis * This Recommendation should be brought to the attention of Radiocommunication Study Groups 4 and 9. The use of HAPS systems in these bands shall be optional for administration
8、s. Each administration shall retain its individual authority over technical and regulatory matters pertaining to the sharing, coordination and implementation of HAPS systems in these bands. * HAPS is defined in RR No. S1.66A as “A station located on an object at an altitude of 20 to 50 km and at a s
9、pecified, nominal, fixed point relative to the Earth.” A HAPS system consists of a HAPS, several ground stations, and numerous mobile and fixed subscriber stations. Each HAPS deploys a multibeam antenna capable of projecting numerous spot beams within its coverage area. The HAPS system mobile and fi
10、xed subscriber stations are identical to those used with traditional terrestrial IMT-2000 tower-based systems. Links between two HAPS and links between HAPS and HAPS system ground stations will not be in bands designated for IMT-2000 and will utilize non-IMT-2000 frequencies. Use of any proposed fre
11、quencies by HAPS for these links will need to be studied and coordinated. * The HAPS systems will be global in nature but national in service provision. Each HAPS will be positioned above commercial airspace at an altitude that is high enough to provide service to a large footprint but that is low e
12、nough to provide dense coverage. HAPS will offer a new means of providing IMT-2000 with minimal ground network infrastructure. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services2 Rec. ITU-R M.1456 g) that the bands 1980-2010 MHz and 2170
13、-2200 MHz are allocated on a primary basis worldwide to the MSS, that the band 2 160-2 170 MHz is allocated on a primary basis to the MSS in Region 2 and that the band 2 010-2 025 MHz is also allocated on a Co-primary basis in Region 2 to the MSS (Earth-to-space); h) that RR No. S5.388 states that “
14、the bands 1885-2025 MHz and 2 110-2200 MHz are intended for use, on a worldwide basis, by administrations wishing to implement International Mobile Telecommunications-2000 (IMT-2000). Such use does not preclude the use of these bands by other services to which they are allocated. The bands should be
15、 made available for IMT-2000 in accordance with Resolution 212 (Rev.WRC-97)“; j) that, however, administrations may use non-IMT-2000 systems in the mobile service in these bands, recommends 1 that radio interfaces of HAPS providing IMT-2000 in the bands 1885-1 980 MHz, 2010-2025 MHz and 2 110-2 170
16、MHz in Regions 1 and 3, and 1885-1 980 MHz and 2 110-2 160 MHz in Region 2 should comply with Recommendation ITU-R M. 1457; 2 that for the purpose of protecting stations operated by neighbouring administrations from Co-channel interference, administrations using HAPS as base stations to provide IMT-
17、2000 should use antennas that comply with the following antenna pattern: G(v) = X - 6Olog(w) dBi for w2 7.3 = 0.1 F, the condition for the dominance of the aggregated far side- lobe level in the determination of the coordination distance. Equation (1 1) is only valid for very narrow HAPS coverage. I
18、n the opposite limit where because of the rapid side-lobe attenuation, the interference is dominated by a single beam, the interference power to thermal noise ratio of the victim handset receiver is approximately: where: (ZreceivedlN)centre : received aggregate interference power-to-noise ratio meas
19、ured at the boresight of the outermost HAPS beam 80 : tilt angle of the last HAPS beam 8: tilt angle of the victim handset relative to HAPS 6 G(8 - 80) = G(8 - 80) - G,: differential antenna gain 6 FSL(8) = 20 log(cos(80) - 20 log(cos(8) : differential free space path loss (FSL) between the HAPS tra
20、nsmitters and the victim handset relative to the free space path loss at the boresight of the last beam. Since the interference power received by the victim handset inside the main lobe of the HAPS emission is typically too large to be permissible, only the inverse sixth power law regime of the ante
21、nna radiation pattern will be of relevance for this discussion. In the inverse sixth power law regime, 6 G(8 - 80) can be expressed, by setting 8 - 80 = v2q + v2, as 6 G(8 - eo) = -LN - 60 log(1 + ri) = -LN - 60 y dB where: Y = log(1 +Y LN: near side-lobe level relative to the peak gain (dB) as requ
22、ired by the system design. For this study LN is taken to be 32 dB. For main coverage radius less than 132km, the free space path loss is a much slower function of the tilt angle 8 than the antenna gain variation. Hence it is a good approximation to replace the differential free space loss term with
23、just the first two terms of its Taylor series expansion, using 8 = eo + (i + q)v2 = eo + loy v2. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services8 Rec. ITU-R M.1456 6 FSL(0) = 20 log(cos(00) - 20 log(cos(00 + 1oy w2) LI= 20 log(cos(00)
24、 - 20 log(cos(00 + 2) + 20 w2 tan(00 + w2) y (14) = 20log(cos(0o) - 201og(cos(00 + w2) + 20w2 tan(00 + w2)y Let D = (Ireceived/N)centre - Threshold - LN, the coordination distance can be obtained from the solution for y, where Threshold = -10 dB is the permissible ZIN threshold for HAPS interfering
25、into victim mobile stations. y = D - 2Olog(cos(0) + 2Oog(cos(0 + w2)/60 + 201q2tan(o + w2)I (15) The required coordination distance (relative to nadir of HAPS) follows by using the relationship: An empirical formula derived from equation (16) that takes into account the aggregated interference level
26、 in equation (1 1) is given below: Rcoordination = tan(o + loy 2)h + (i - h/(158 os(0)(lrurn x 10-7.3+B - i)1/2 h km (17) The approximation method yields fairly accurate results when compared to actual multibeam computation. This is shown in Fig. 3: FIGURE 3 Comparison of approximate and multibeam c
27、omputation (HAPS using CDMA format) 1 O00 960 920 880 840 800 760 E 720 680 a 640 =; 600 h 3 560 .s 520 e 480 o 440 0 400 2 360 .5 $ 320 e?l 280 240 200 160 120 80 40 O 8 14 20 26 32 38 44 50 56 62 68 74 80 86 92 98 104 110 116 122 128 134 140 146 152 158 HAPS coverage radius (km) Multibeam calculat
28、ion - Approximate formula 1456-03 COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesRec. ITU-R M.1456 9 As can be seen from Fig. 3, the approximate formula yields results that are within 1% of those obtained from the explicit multibeam c
29、alculation for coverage radius up to 132 km. Note that if a mobile station is beyond the horizon, it should not receive interference from HAPS because of the visibility constraint. If the HAPS is deployed at 22 km altitude, its horizon is approximately 600 km measured from nadir. Because of heavy cl
30、utter attenuation, the visible horizon and the radio horizon should be roughly the same. 2.1 HAPS into the fixed service The interference to a point-to-point (P-P) fixed service from HAPS operating in the same bands as the fixed service will require a coordination distance between the nadir of HAPS
31、and the fixed service antenna that is a function of fixed service antenna gain, its boresight angle relative to HAPS, and HAPS coverage radius. Such P-P service typically uses antennas with sufficient directivity to optimize long-range communications. Assuming that the fixed service antenna points a
32、pproximately in the horizontal direction, the interference power received by the fixed service antenna from HAPS can be written as follows: where: eeceived(8) : power received on the ground as a function of the tilt angle 8 r: distance from nadir of the nearest HAPS beam Gvictim(cp, r): antenna gain
33、 of the fixed service antenna as a function of both the off-boresight angle relative to HAPS nadir and the distance of the fixed service from nadir. The latter can be expressed as a function of the off-boresight angle a defined by: a = COS-T cos(cp/(r2 + h 2 ) 112 1 Owing to the high pfd values of f
34、ully loaded HAPS systems within HAPS primary coverage areas, Co-channel sharing within HAPS coverage area is clearly not possible, and this is borne out by explicit multibeam computation of the aforementioned scenario. Outside HAPS main coverage area, equation (20) is valid where 6 G(8 - 80) and 6 F
35、SL(8) have already been defined, and Gs(a(cp, r) = Gvichm(cp, r). This leads to equations (21) and (22): where: Figure 4 gives the required coordination distances as a function of the cosine angle of boresight of the fixed service antenna relative to nadir HAPS for 8, 37, 87, 110 and 158 km HAPS cov
36、erage, respectively. The fixed service antenna is assumed to have a 31 dBi gain, and a directivity pattern in accordance with Recommendation ITU-R F.699. The reference antenna radiation patterns for antennas on HAPS platforms are given in Appendix 1 to Annex 1. The approximation method yields accura
37、te results only when the coverage radius is small (5 60 km). This is shown in Fig. 5. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services10 Rec. ITU-R M.1456 FIGURE 4 Coordination distance versus azimuth and coverage radius (HAPS using TD
38、MA format) 158 km coverage radius - - - - - - - - - 110 km coverage 87 km coverage . 8 km coverage 37 km coverage 145644 COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesRec. ITU-R M.1456 11 FIGURE 5 Coordination distance versus azimuth
39、 and coverage radius, comparison of exact and approximate results (HAPS using CDMA format) 100 90 80 87 km coverage radius 37 km coverage 8 km coverage - - - - - - - - - 87 km coverage (approximately) . 37 km coverage (approximately) - . - . - . - 8 km coverage (approximately) 1456-05 COPYRIGHT Inte
40、rnational Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services12 Rec. ITU-R M.1456 2.2 Interference from HAPS using IMT-2000 CDMA format into IMT-2000 mobile stations The interference criterion of ZIN = -10 dE3 will be used. It makes no difference whether the int
41、erfered mobile station uses an IMT-2000 CDMA or TDMA format or not, only the level of interference from HAPS matters. It is clear from Fig. 1 that such sharing is entirely feasible for smaller radius HAPS coverage. Even for a main coverage radius of 62 km, a victim tower-based system can provide the
42、 IMT-2000 service in the same frequency band assuming that its coverage area is at least 33 km from the nearest HAPS main beam. Figure 6 shows the relationship between the coordination distance and the HAPS coverage, and Fig. 7 shows the distance between the coordination boundary and the nadir of HA
43、PS as a function of HAPS coverage radius. The results in Fig. 7 are summarized in Table 1. FIGURE 6 Coordination distance versus radius of main HAPS coverage area (HAPS using CDMA format) h E ?5 o .3 Y o 3 o 800 768 736 704 672 640 608 576 5 44 512 480 448 416 384 352 320 288 256 224 192 160 128 96
44、64 32 O HAPS coverage radius (km) 1456-06 COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesRec. ITU-R M.1456 13 FIGURE 7 Coordination boundary measured from nadir versus coverage radius (HAPS using CDMA format) E 480 448 .Ci 416 384 3 3
45、52 0 320 2 288 .5 256 2 224 192 160 128 96 64 32 O Y .3 HAPS coverage radius (km) 1456-08 COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesRec. ITU-R M.1456 Radius 8 11 15 19 23 27 32 37 43 49 55 62 70 78 87 97 107 of coverage Coordinat
46、ion 34 38 41 45 50 55 61 68 76 86 98 114 136 164 205 264 353 distance (measured from nadir) Coordination 26 26 26 27 27 28 29 30 33 37 43 52 65 86 118 167 246 distance (measured from the nearest beam centre) 15 119 490 371 FIGURE 9 Coordination boundary measured from nadir versus coverage (HAPS usin
47、g TDMA format) 1 O00 960 920 880 840 800 760 E 720 680 o 640 =; 600 560 .ci 520 480 3 440 0 400 2 360 .5 320 e?l 280 240 200 160 120 80 40 O h 3 Y $ 8 14 20 26 32 38 44 50 56 62 68 74 80 86 92 98 104 110 116 122 128 134 140 146 152 158 HAPS coverage radius (km) 2456-09 TABLE 2 Coordination distances
48、 (km) for different radius of coverage (km) using equation (22) (HAPS using TDMA format) COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services16 Rec. ITU-R M.1456 If the number of beams of the interfering HAPS system is different from 700,
49、or if the permissible interference criterion is different from the Z/N = -10 dB used above, then equation (22) should be used for the determination of the minimum coordination distance. 2.4 HAPS into IMT-2000 CDMA TDD base stations There are two kinds of base station antennas, omnidirectional and sectoral. Typical omnidirectional base station antennas have a peak horizontal gain of about 15 dBi, and a 3 dB vertical beamwidth of -5.1“. For sectoral antennas, a typical example is a 90“ sector antenna with a 3 dB beamwidth of 90“ in the horizontal (azimuth
