1、 Rec. ITU-R F.1608 1 RECOMMENDATION ITU-R F.1608 Frequency sharing between systems in the fixed service using high altitude platform stations and conventional systems in the fixed service in the bands 47.2-47.5 and 47.9-48.2 GHz (Question ITU-R 212/9) (2003) The ITU Radiocommunication Assembly, cons
2、idering a) that new technology utilizing telecommunication relays located at fixed points in the stratosphere is being developed (see Note 1); b) that systems utilizing one or more high altitude platform stations (HAPS) located at fixed points in the stratosphere may possess desirable attributes for
3、 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) that such systems would be able to provide coverage to metropolitan regions with high eleva
4、tion angles, and to outlying rural areas or neighbouring countries with low elevation angles; d) that broadband digital services provided by such systems in the fixed service are intended to provide widespread communications information infrastructures promoting the global information infrastructure
5、; e) that the radio spectrum above 30 GHz is allocated to a variety of radio services and that many different systems are already using or planning to use these allocations; f) that there is an increasing demand for access to these allocations; g) that according to No. 5.552A of the Radio Regulation
6、s (RR) the allocation to the fixed service in the bands 47.2-47.5 GHz and 47.9-48.2 GHz is designated for use by HAPS; h) that according to Resolution 122 (Rev.WRC-2000), administrations are urged to facilitate coordination between HAPS in the fixed service operating in the bands 47.2-47.5 GHz and 4
7、7.9-48.2 GHz and other co-primary services in their territory and adjacent territories; j) that because of the visible range of HAPS frequency sharing between HAPS networks and other conventional fixed service systems may present difficulties on a co-area, co-frequency basis, recommends 1 that the c
8、haracteristics of systems in the fixed service using HAPS given in Recommen-dation ITU-R F.1500 may be used in analysing sharing possibilities between HAPS systems in the fixed service and other conventional systems in the fixed service in the bands 47.2-47.5 GHz and 47.9-48.2 GHz; 2 Rec. ITU-R F.16
9、08 2 that in analysing the sharing possibilities between systems in the fixed service using HAPS and other conventional systems in the fixed service, such as is done in Annex 2, the methodology described in Annex 1 may be used; 3 that in those areas where a ubiquitous HAPS service is envisioned, suc
10、h as the urban and suburban coverage areas, co-area frequency sharing with conventional fixed service systems will be difficult. For the typical HAPS system described in Recommendation ITU-R F.1500, with symmetric service areas around the HAPS nadir point, the limit of ubiquitous service is likely t
11、o be at the outer edge of the suburban coverage area, at about 80 km from nadir; 4 that in those areas where a ubiquitous HAPS service is not envisioned, such as the rural coverage area, sharing with other fixed service systems could be feasible provided there is sufficient angular discrimination be
12、tween conventional systems in the fixed service and HAPS systems operating in the fixed service. Such angular discrimination may only be possible if the conventional fixed service systems are located outside the visible range of the HAPS platform; 5 that in those areas where the HAPS coverage is lim
13、ited to only the urban area coverage (UAC) or to both the UAC and the suburban area coverage (SAC), sharing with conventional fixed service systems will only be possible if they are deployed beyond the visible range of the HAPS platform; 6 that further studies could identify additional operational s
14、cenarios and mitigation techniques that could facilitate frequency sharing. NOTE 1 It is recognized that systems utilizing HAPS have a potential applicability to various services such as mobile and broadcasting services. This Recommendation considers the use of HAPS in the fixed service. Annex 1 The
15、 methodology to be used in the analysis of frequency sharing between systems in the fixed service using HAPS and conventional fixed service systems 1 Introduction This Annex provides the basis for methodology for the investigation of the interference scenarios and sharing possibilities between fixed
16、 service systems using HAPS and conventional fixed service systems. To be specific, the frequency bands identified for the fixed service systems using HAPS are 47.2-47.5 GHz and 47.9-48.2 GHz. These bands are part of the band 47.2-50.2 GHz which is also allocated to the fixed-satellite (Earth-to-spa
17、ce) and mobile services. There are some fixed service applications in the 47.2-47.5 GHz and 47.9-48.2 GHz bands; Recommendation ITU-R F.758 discusses the considerations necessary in the development of sharing criteria. The bands are not currently in use by the mobile service and no parameters are Re
18、c. ITU-R F.1608 3 available on which to base typical interference analysis. It should be noted, however, that the high density of small user terminals envisaged for use by the HAPS-based network (HAPN) is expected to render sharing with mobile service systems very difficult. 2 Technical characterist
19、ics The technical characteristics for a typical HAPN operating in the bands 47.2-47.5 GHz and 47.9-48.2 GHz are given in Recommendation ITU-R F.1500. This text gives information on both the technical parameters of the equipment and on the gains and directivity of antennas mounted on a HAPS. Technica
20、l characteristics for terrestrial fixed service systems operating in the band 47.2-50.2 GHz are given in Recommendation ITU-R F.758. Reference antenna patterns are given in Recommendation ITU-R F.699. The propagation characteristics for free space path loss, atmospheric gaseous absorption, and hydro
21、meteor attenuation and scattering are given in various Recommendations in the ITU-R P-Series. 3 Sharing study methodology Recommendation ITU-R F.1500 indicates that a typical HAPN may offer up to 2 100 cells, with a 7-times frequency reuse factor, within a service diameter of 468 km. In addition the
22、re may be up to 40 gateway stations within a diameter of 181 km. Dependent on the bandwidth assigned to an individual HAPN, there may be up to 330 000 simultaneous user terminals in operation from a subscriber base of more than 5 million. Each of these user terminals will have an antenna directed to
23、wards the HAPS. The 2 100 beams from the HAPS will extend across the whole of the coverage area, with frequency reuse. Conventional fixed service usage of the band may be either for wide bandwidth links between well-defined fixed locations, or for high-density fixed links where the location and orie
24、ntation of each link may not be specified in advance. For both of these types of conventional application the link length will be limited by both terrain and screening and by atmospheric and hydrometeor absorption. Due to the multiplicity of potential links, the methodology for undertaking sharing s
25、tudies will have to be based on determining the potential interference between a pair of stations, including the appropriate antenna directivity characteristics, and calculating for many such cases using a random selection of station locations within the coverage areas and subject to appropriate fre
26、quency reuse, bandwidth, etc. considerations. Some preliminary studies of this kind have been undertaken, with 720 million cases in the simulations. These have indicated that co-channel sharing between terrestrial fixed stations and HAPN user terminals will be very difficult, and that necessary geog
27、raphical separation between a HAPN coverage and a conventional fixed service station depends on the gain, and thus on the orientation of the fixed link. For such adjacent area coverages simulation using unobstructed plane Earth paths will not be adequate and the method should include Earth curvature
28、 and the probability of screening from terrain or surface features. 4 Rec. ITU-R F.1608 Similarly for interference simulation for the HAPS terminals, adjacent area sharing depends on the location and direction of the fixed links, but in this case there is a smaller probability of diffraction screeni
29、ng due to the oblique paths. Annex 2 Frequency sharing between the conventional fixed service and HAPS systems 1 HAPS in the fixed service Recommendation ITU-R F.1500 contains details of the preferred characteristics of a typical HAPS system in the fixed service. These characteristics are given in T
30、ables 1 to 4: TABLE 1 HAPS coverage zones TABLE 2 Platform station transmitter parameters TABLE 3 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 RAC: rural area coverage Coverage area
31、Transmitter power (dBW) Antenna gain (dBi) UAC 1.3 30 SAC 1.3 30 RAC 3.5 41 Coverage area Transmitter power (dBW) Antenna gain (dBi) UAC 8.2 23 SAC 7 38 RAC 1.5 38 Rec. ITU-R F.1608 5 TABLE 4 Interference criteria for HAPS systems 1608-010 1836547290108126141621804035302520151050510Guac()Gsac()Gain(
32、dBi)Off-axis angle (degrees)FIGURE 1Antenna reference radiation pattern envelopes for HAPS user terminals(based on Recommendation ITU-R F.699)2 Overview of other fixed service systems in the bands 47.2-47.5 GHz and 47.9-48.2 GHz Table 5 gives parameters of conventional fixed service systems in the 4
33、7 GHz band as provided in Recommendation ITU-R F.758. System 1 will be used as the interference source (because it has the highest spectral e.i.r.p.), and System 3 as the victim (because it is the system most sensitive to interference). User terminal HAPS Interference criteria (dB(W/MHz) 149 151.6 6
34、 Rec. ITU-R F.1608 TABLE 5 Terrestrial service fixe system radio characteristics 3 Interference analysis The interference analysis is based on the scenarios identified in Fig. 2. 1608-0212FIGURE 2Interference scenariosConventional terrestrial fixed service linkHAPS user terminalInterference pathWant
35、ed pathHAPS platform1 and 2: Scenarios as mentioned in 3.1 and 3.2.3.1 Interference between HAPS user terminals and conventional systems in the fixed service (Scenario 1) This section examines the following interference scenarios: interference from conventional systems in the fixed service into HAPS
36、 user terminals; System 1 2 3 4 Modulation 2-FSK 4-QAM 16-QAM 256-QAM Capacity (Mbit/s) 1.544 44.736 90 310 Channel bandwidth (MHz) 5 50 50 50 Maximum antenna gain (dBi) 46 46 46 46 Maximum transmitter power (dBW) 11 12 2 2 Maximum e.i.r.p. (dB(W/MHz) 28 17 27 27 Receiver bandwidth (MHz) 2 50 50 50
37、Receiver noise figure (dB) 11 13 5 5 Receiver thermal noise (dB(W/MHz) 133 133 137 137 Interference criteria (dB(W/MHz) 143 143 147 147 Rec. ITU-R F.1608 7 interference from HAPS user terminals into conventional systems in the fixed service. The analysis is based on single and multiple interference
38、sources. A separation distance is determined between the HAPS user terminals and conventional systems in the fixed service such that the relevant interference criterion is not exceeded. The results of previous studies indicate that co-area frequency sharing will be difficult especially in areas wher
39、e a ubiquitous HAPS service is envisioned and is only likely to be possible in special situations where carefully selected antenna locations and path geometries are favourable. Hence, the separation distances in this study are calculated on the basis that the conventional systems in the fixed servic
40、e are located outside the HAPS coverage area. 3.1.1 Interference analysis based on a single interference source Table 6 gives the calculated values of the separation distance for the single interference analysis. It is assumed that the HAPS user terminal and the conventional systems in the fixed ser
41、vice are located at a height of 10 m. TABLE 6 Separation distances for interference between HAPS user terminals and conventional fixed service systems 3.1.2 Interference analysis based on multiple sources The multiple interference analysis is based on a Monte-Carlo approach, taking actual United Kin
42、gdom terrain data into account. The aggregate interference at the receiver was calculated for each of 1 000 000 trials, where each trial corresponds to a random distribution of interfering transmitters. The path loss from each transmitter to the receiver was calculated using Recommendation ITU-R P.4
43、52. A cumulative distribution function (CDF) of interference at the receiver was then generated. This CDF does not correspond to the time for which interference may be experienced, but rather to the likelihood, given the random location of terminals. 3.1.3 Interference from conventional systems in t
44、he fixed service into HAPS user terminals For the case of interference from conventional systems in the fixed service into a HAPS user terminal the parameters shown in Table 7 have been assumed. Sites in Cambridgeshire, United Kingdom, at Breckland and Great Bardfield, were chosen. Breckland is made
45、 up of low-lying/flat terrain while Great Bardfield is made up of very hilly/rough terrain. The separation distance RAC SAC UAC Interference scenario Separation distance (km) Fixed service into HAPS user terminal 26.5 26.5 29.5 HAPS user terminal into fixed service 28 28 31 8 Rec. ITU-R F.1608 betwe
46、en the HAPS user terminal and the area populated with interfering transmitters was set to 30 km (approximately equal to separation distance derived from the single interference analysis in 3.1.1). TABLE 7 Parameters used to assess aggregate interference from conventional systems in the fixed service
47、 into a HAPS user terminal The results of the simulations are illustrated in Figs. 3 and 4. 1608-031000908070605040302010150 145 140 135 130 125 120FIGURE 3CDF of interference for aggregate interference from conventional systemsin the fixed service into HAPS user terminal located at the edge of a UA
48、C(based on fixed service systems located at Breckland)CDFInterference criteriaInterference (dB(W/MHz)Probability(%)Terrestrial fixed service system transmitters Density 0.02 sites/km2Location 10 km radius around TL660900 (Breckland) or TL675300 (Great Bardfield) HAPS user terminal receiver Location
49、Madingley, Cambridge (TL388595) Rec. ITU-R F.1608 9 1608-041000908070605040302010210 200 190 180 170 160 150 140FIGURE 4Interference CDF for aggregate interference from conventional systems in the fixed service into a HAPS user terminal located at the edge of a UAC(based on fixed service systems located at Great Bardfield)CDFInterference criteriaInterference (dB(W/MHz)Probability(%)It can be seen from Figs. 3 and 4 that the difference in the terrain accounts for a substantial difference (about 40 dB) in the interference received at the HAPS u
