1、 Rec. ITU-R SF.1481-1 1 RECOMMENDATION ITU-R SF.1481-1 Frequency sharing between systems in the fixed service using high-altitude platform stations and satellite systems in the geostationary orbit in the fixed-satellite service in the bands 47.2-47.5 and 47.9-48.2 GHz (Questions ITU-R 251/4 and ITU-
2、R 218/9) (2000-2002) The ITU Radiocommunication Assembly, considering a) that new technology is being developed utilizing telecommunication relays located on high altitude platforms at fixed points in the stratosphere (see Note 1); b) that systems utilizing one or more high altitude platform station
3、s (HAPS) located at fixed points in the stratosphere may possess desirable attributes for high-speed broadband digital communications, including interactive video and other applications, with significant potential for frequency reuse and capable of providing service to a high density of users; c) th
4、at such systems would be able to provide coverage to metropolitan regions with high elevation angles and short path lengths, and to outlying rural areas or neighbouring countries with low elevation angles but without reducing capacity; d) that broadband digital services provided by such systems in t
5、he fixed service (FS) are intended to provide widespread communications information infrastructures promoting the global information infrastructure (GII) network; e) that in areas of high population and business densities, users of these services are expected to be ubiquitous; f) that the radio spec
6、trum above 30 GHz is allocated to a variety of radio services and that many different systems are already using or planning to use these frequency band allocations; g) that the bands 47.2-47.5 GHz and 47.9-48.2 GHz are allocated to the fixed-satellite service (FSS), including non-GSO systems, in the
7、 Earth-to-space direction; h) there is an increasing demand for access to these allocations; j) that according to Radio Regulations (RR) No. 5.552A the allocation to the FS in the bands 47.2-47.5 GHz and 47.9-48.2 GHz, is designated for use by HAPS; k) that according to Resolution 122 (Rev.WRC-2000)
8、, administrations are urged to facilitate coordination between HAPS systems in the fixed service operating in the bands 47.2-47.5 GHz and 47.9-48.2 GHz and other co-primary radio services in their territory and adjacent territories; l) that because systems in the FS using HAPS can use the full range
9、 of elevation angles, sharing with the FSS may present difficulties; 2 Rec. ITU-R SF.1481-1 m) that such high-altitude platform systems may not present the same sharing difficulties with broadcasting-satellite feeder link use of the FSS bands; n) that due to high diffraction losses at these frequenc
10、ies, interference may be mitigated by taking advantage of local shielding to reduce side lobe radiation; o) that a typical FS system using HAPS is described in Recommendation ITU-R F.1500, recommends 1 that to facilitate sharing in the bands 47.2-47.5 GHz and 47.9-48.2 GHz FSS earth stations should
11、utilize antennas with diameters of at least 2.4 m, or other types of antenna with similar performance; 2 that, when installing user terminals or gateway stations in the FS using HAPS, or FSS earth stations, advantage should be taken of local topography or of man-made features so as to maximize the s
12、hielding of side lobe radiation while maintaining system performance. This may include locating antennas at the minimum acceptable height above ground level; 3 that in those areas where a HAPS system is intended to provide an ubiquitous service, sharing with FSS earth stations is not expected to be
13、generally feasible. For the typical HAPS system described in Recommendation ITU-R F.1500, with symmetrical service areas around the HAPS nadir point, the limit of the ubiquitous service is likely to be at the outer edge of the suburban area coverage, at about 80 km from nadir; 4 that in the rural co
14、verage area, beyond 80 km radius, the provision of an ubiquitous service is not anticipated and sharing with FSS earth stations could be feasible provided the FSS earth stations have sufficient angular discrimination between the HAPS platform and the FSS satellite. Often such angular discrimination
15、may only be achievable if the FSS earth station is located outside the HAPS coverage region or if the boresight of the FSS satellite points away from the HAPS coverage area; 5 that for co-located FSS earth stations and HAPS user terminals in the rural coverage area, the maximum separation distance t
16、aking account of local shielding would be approximately 30 km. But this is strongly dependent on the geometries of earth stations relative to the user terminals and in many cases may be less than 1 km; 6 that in analysing the sharing feasibilities between systems in the FS using HAPS and systems in
17、the FSS, such as is done in Annex 4, the methodology in Annex 1 and the information in Annexes 2 and 3 be provisionally used (see Notes 2 to 5); 7 that further studies could identify additional operational scenarios and mitigation techniques which could facilitate frequency sharing. NOTE 1 It is rec
18、ognized that systems utilizing HAPS have a potential applicability to various services such as mobile and broadcasting services. In this Recommendation the application is focused on the FS in the bands 47.2-47.5 and 47.9-48.2 GHz. Rec. ITU-R SF.1481-1 3 NOTE 2 The information in Annexes 2 and 3 is f
19、or a specific system being developed. Further study is required for developing widely applicable interference criteria. NOTE 3 Parameters for broadcasting-satellite service (BSS) feeder links cited in Annex 3 are taken from Report ITU-R BO.2016. Parameters for the GSO FSS systems used are also cited
20、 in Annex 3. NOTE 4 There may be a need to develop the maximum allowable power flux-density at satellites on the GSO due to aggregate interference caused by ground user terminals of high altitude platform networks. NOTE 5 The assessment of aggregate interference may be improved by developing a simul
21、ation model that takes into account geographical distributions and antenna characteristics of the ground terminals in the high-altitude platform networks. ANNEX 1 Methodology for studying frequency sharing between high-density systems in the FS using HAPS and the FSS 1 Introduction This Annex presen
22、ts the interference criteria and the prediction procedures to be used for sharing analyses between high-density systems in the FS using HAPS and FSS systems. The frequency bands considered are 47.2-47.5 GHz and 47.9-48.2 GHz. The characteristics of a typical network using HAPS for the high-density F
23、S application are given in Recommendation ITU-R F.1500, some relevant parameters are summarized in Annex 2. Typical system parameters for GSO BSS feeder links and for GSO FSS systems are given in Annex 3. 2 Calculation procedure The e.i.r.p. density in a 1 MHz reference bandwidth can be calculated f
24、rom the following equation: dB(W/MHz)log10 BLGPprietft+= where: P : transmitter output power density (dB(W/MHz) Gt: transmitting antenna gain (dBi) Ltf: antenna feeder loss (dB) B : bandwidth. The elements to be taken into account in estimating the total path loss are given in Recommendation ITU-R P
25、.1409. A formula for atmospheric attenuation is also given in Recommendation ITU-R SF.1395. 4 Rec. ITU-R SF.1481-1 The expected received power density can be calculated from: 60)/4(log20log10 += dBLLLGLGPPparfrtftrdB(W/MHz) (1) where: Pr: expected received carrier power density (dB(W/MHz) P : transm
26、itting 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) La: atmospheric absorption for a particular elevation angle (dB) Lp: attenuation due to other propagation effects (
27、dB) : wavelength (m) d : distance (km). ANNEX 2 System characteristics for a typical high-altitude platform network 1 The high-altitude platform system The description of a typical system is given in Recommendation ITU-R F.1500. The system comprises a high-altitude platform in a nominally fixed loca
28、tion in the stratosphere at a height of 21 to 25 km. Communication is between the platform and user terminals on the ground in a cellular arrangement permitting substantial frequency reuse. User terminals are described as being within one of three zones: urban, suburban and rural area coverages (UAC
29、, SAC and RAC, respectively). 1.1 Coverage areas The coverage areas are defined in terms of the elevation angle at the ground to the HAPS. The depression angles at the platform are closely similar. Table 1 gives the angles and the corresponding ground coverage range measured from nadir. TABLE 1 Cove
30、rage zones Ground range (km) Coverage area Elevation angles (degrees) Platform at 21 km Platform at 25 km UAC 90-30 0-36 0-43 SAC 30-15 36-76.5 43-90.5 RAC 15-5 76.5-203 90.5-234 Rec. ITU-R SF.1481-1 5 1.2 Platform station Typical transmitter and antenna characteristics for a platform station are gi
31、ven in Table 2. Communications with user terminals will use time division multiplexed (TDM) 4-PSK modulation, and with gateway stations will use high-level modulation, 64-QAM. TABLE 2 Platform station transmitter parameters 1.3 User terminals and gateway stations The corresponding parameters for the
32、 ground stations are given in Table 3. In the up direction the user terminals will use demand assigned multicarrier TDMA with 4-PSK modulation, while gateway stations will use similar techniques to those from the platform. TABLE 3 Ground station transmitter characteristics 1.4 Antenna radiation patt
33、erns The antenna radiation patterns for platform antennas conform to Recommendation ITU-R S.672. Communication to Transmitter power (dBW) Antenna gain (dBi) UAC 1.3 30 SAC 1.3 RAC 3.5 41 Gateway (UAC) 0 35 Gateway (SAC) 9.7 38 Communication to Transmitter power (dBW) Antenna gain (dBi) UAC 8.2 23 SA
34、C 7 38 RAC 1.5 Gateway (UAC) 1.7 46 Gateway (SAC) 13.4 46 6 Rec. ITU-R SF.1481-1 ANNEX 3 System parameters for FSS 1 System parameters for BSS feeder links 2 System parameters of a GSO FSS Earth-to-space link BSS feeder-link parameters Modulation 4-PSK Frequency (GHz) 48.2 Bandwidth (MHz) 1 Transmit
35、ting antenna (earth station): Power (dB(W/MHz) 3 Gain (dBi) 57.7 Feeder loss (dB) 2.5 e.i.r.p. (dB(W/MHz) 58.2 Elevation angle (degrees) 55 Path length (km) 36 780 Free space loss (dB) 217.4 Atmospheric absorption (dB) 1.2 Earth station Uplink frequency (GHz) 47.2-50.2 Maximum antenna gain (2.4 m/0.
36、9 m) (dBi) 59.7/51.2 Antenna gain pattern (dBi) 29 25 log min = 10 Earth station feeder loss (dB) 2.5 Minimum elevation angle (degrees) 20 Maximum power density (2.4 m/0.9 m) (dB(W/MHz) 1.8/6.7 Maximum e.i.r.p. density (2.4 m/0.9 m) (dB(W/MHz) 55.4/55.4 Satellite Maximum antenna gain (dBi) 51.5 Sate
37、llite G/T (dB(K1) 23.4 System noise temperature (K) 650 Beam size (degrees) 0.3 Number of beams 24 Rec. ITU-R SF.1481-1 7 ANNEX 4 Frequency sharing between HAPS systems in the FS and stations in the FSS 1 System parameters for HAPS in the FS The parameters that were used in the study were derived fr
38、om Recommendation ITU-R F.1500 and are as follows: TABLE 4 HAPS coverage zones TABLE 5 Platform station transmitter parameters TABLE 6 User terminal transmitter parameters Coverage area Elevation angles (degrees) Ground range (km) (HAPS at 21 km) UAC 90-30 0-36 SAC 30-15 36-76.5 RAC 15-5 76.5-203 Co
39、mmunication to Transmitter power (dBW) Antenna gain (dBi) UAC 1.3 30 SAC 1.3 30 RAC 3.5 41 Communication to Transmitter power (dBW) Antenna gain (dBi) UAC 8.2 23 SAC 7 38 RAC 1.5 38 8 Rec. ITU-R SF.1481-1 TABLE 7 Interference criteria for HAPS systems 1481-0140303520251015051051836547290108126141621
40、80GUAC()GSAC()Gain(dBi)FIGURE 1Antenna radiation patterns for HAPS user terminals using Recommendation ITU-R F.699Off-axis angle (degrees)2 Overview of FSS systems There are a number of FSS systems, which may become operational in the 47 GHz band (Earth-to-space link). The parameters given in Table
41、8 represent a typical GSO FSS system and were used as the basis for the analysis. User terminal HAPS Interference criterion (dB(W/MHz) 149 151.6 Rec. ITU-R SF.1481-1 9 TABLE 8 Characteristics of a typical FSS earth station 3 Interference analysis Figure 2 illustrates the interference scenarios that
42、were considered in this study. These are listed in Table 9. 1481-024321FSS satelliteFSS earth station HAPS user terminalHAPS airshipInterference pathWanted pathFIGURE 2Interference scenariosEarth station Maximum antenna gain (dBi) 57.5 Antenna diameter (m) 1.88 Maximum transmitter power before losse
43、s (dB(W/MHz) 3 Earth station losses (dB) 2.5 e.i.r.p. (dB(W/MHz) 58 Antenna pattern RR Appendix 30B Elevation angle (degrees) 55 Satellite Maximum antenna gain (dBi) 51.8 Interference criterion (dB(W/MHz) 150.5 Antenna pattern Recommendation ITU-R S.672 (Ls= 20) 10 Rec. ITU-R SF.1481-1 TABLE 9 Inter
44、ference scenarios A further scenario should be considered: an interference path from a HAPS via ground backscatter to a satellite. Some information relevant to this case is given in Recommendation ITU-R P.1409. This scenario requires further study. 3.1 Interference from FSS earth stations into HAPS
45、user terminals (Scenario 1) This section examines interference from FSS earth stations into HAPS user terminals. 3.1.1 Single interferer interference analysis This analysis is based on free space propagation and atmospheric loss. The effects of buildings and terrain irregularities were not taken int
46、o account. 1481-03d12FSS earthstationHAPS userterminalFIGURE 3Single interferer interference analysisInterfering signalWanted signal1: elevation angle of the FSS earth station2: elevation angle of the HAPS user terminald: separation distance at which the long-term interference criterion is satisfied
47、.where:Table 10 contains details of the separation distances that were obtained using the parameters given in Table 8. Interference scenario Interference source Victim system 1 FSS earth station HAPS user terminal 2 FSS earth station HAPS airship 3 HAPS user terminal FSS satellite 4 HAPS airship FSS
48、 satellite Rec. ITU-R SF.1481-1 11 TABLE 10 Required separation distances for the single interferer interference analysis 3.1.2 Building obstruction model In reality, there will not always be a line-of-sight path between the FSS earth stations and the HAPS user terminals, especially in urban and sub
49、urban areas. Therefore, it is feasible to assume that where a line-of-sight path does not exist between the HAPS user terminals and the FSS earth stations, the path loss would be such that the interference into the HAPS user terminals could be ignored. Instances like these have been modelled using Recommendation ITU-R P.1410 Propagation data and prediction methods required for the design of terrestrial broadband millimetric radio access systems operating in a frequency range of about 20-50 GHz. The Recommendation uses a simple s
