1、 Recommendation ITU-R F.2011 (01/2012) Evaluation of interference from high-altitude platform (HAPS) gateway links (HAPS-to-ground direction) in the fixed service to conventional fixed wireless systems in the range 5 850-7 075 MHz F Series Fixed service ii Rec. ITU-R F.2011 Foreword The role of the
2、Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use of the radio-frequency spectrum by all radiocommunication services, including satellite services, and carry out studies without limit of frequency range on the basis of which Recommendations are adopted. The
3、 regulatory and policy functions of the Radiocommunication Sector are performed by World and Regional Radiocommunication Conferences and Radiocommunication Assemblies supported by Study Groups. Policy on Intellectual Property Right (IPR) ITU-R policy on IPR is described in the Common Patent Policy f
4、or ITU-T/ITU-R/ISO/IEC referenced in Annex 1 of Resolution ITU-R 1. Forms to be used for the submission of patent statements and licensing declarations by patent holders are available from http:/www.itu.int/ITU-R/go/patents/en where the Guidelines for Implementation of the Common Patent Policy for I
5、TU-T/ITU-R/ISO/IEC and the ITU-R patent information database can also be found. Series of ITU-R Recommendations (Also available online at http:/www.itu.int/publ/R-REC/en) Series Title BO Satellite delivery BR Recording for production, archival and play-out; film for television BS Broadcasting servic
6、e (sound) BT Broadcasting service (television) F Fixed service M Mobile, radiodetermination, amateur and related satellite services P Radiowave propagation RA Radio astronomy RS Remote sensing systems S Fixed-satellite service SA Space applications and meteorology SF Frequency sharing and coordinati
7、on between fixed-satellite and fixed service systems SM Spectrum management SNG Satellite news gathering TF Time signals and frequency standards emissions V Vocabulary and related subjects Note: This ITU-R Recommendation was approved in English under the procedure detailed in Resolution ITU-R 1. Ele
8、ctronic Publication Geneva, 2012 ITU 2012 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without written permission of ITU. Rec. ITU-R F.2011 1 RECOMMENDATION ITU-R F.2011* Evaluation of interference from high-altitude platform (HAPS) gateway links (HAPS
9、-to-ground direction) in the fixed service to conventional fixed wireless systems in the range 5 850-7 075 MHz (2012) Scope This Recommendation provides a method for the evaluation of interference between fixed service (FS) systems using high-altitude platform stations (HAPS) gateway links (HAPS-to-
10、ground) and conventional fixed wireless systems in the range 5 850-7 075 MHz in response to the technical study invited by Resolution 734 (Rev.WRC-07). The method is used to determine areas where specific values of I/N would be exceeded in an FS receiver. Results include plots and calculations of th
11、e areas for various specified I/N values. The ITU Radiocommunication Assembly, considering a) that new technology utilizing high-altitude platform stations (HAPS) in the stratosphere has been developed to provide high-capacity services; b) that some administrations intend to operate the systems usin
12、g HAPS in the bands allocated for such use by the Table of Frequency Allocations or by footnotes for the fixed service; c) that in addition to such service links, there is a requirement for gateway links which can connect the service links to the public switched telephone network (PSTN), broadband d
13、ata networks, cellular telephone systems and sound and television broadcasting providers; d) that WRC-07 adopted Resolution 734 (Rev.WRC-07) requesting ITU-R sharing studies with a view to identifying two channels of 80 MHz each for gateway links for HAPS in the range from 5 850 to 7 075 MHz, in ban
14、ds already allocated to the fixed service, while ensuring the protection of existing services; e) that large portions of this band are heavily used by existing services, recommends that, in response to the technical study stated in considering d), to evaluate interference from HAPS gateway links (HA
15、PS-to-ground) in the fixed service to conventional fixed wireless systems in the range 5 850-7 075 MHz the methodology described in Annex 1 should be used. * This Recommendation has been prepared in support of World Radiocommunication Conference 2012 (WRC-12) Agenda item 1.20. In the event that WRC-
16、12 does not identify spectrum for gateway links for high-altitude platform stations in this band, the Recommendation will be suppressed. 2 Rec. ITU-R F.2011 Annex 1 Evaluation of interference from high-altitude platform gateway links (HAPS-to-ground direction) in the fixed service to conventional fi
17、xed wireless systems in the range 5 850-7 075 MHz 1 Introduction This Annex presents a methodology for determining the ratio of interference power to noise power at the input of a point-to-point receiver in the fixed service due to operation of HAPS gateway downlinks. This is one of the interference
18、 cases that should be considered under WRC-12 Agenda item 1.20. The parameters and models used in the analysis are described in Section 2; the possible I/N criteria that might be applied are described in Section 3; the methodology is described, applied and the results obtained with it are presented
19、in Section 4 for the case where the HAPS platform is transmitting to only one gateway station. In Section 5, consideration is given to the aggregate interference when the HAPS platform is transmitting to multiple gateway ground stations in a symmetrical configuration. In Section 6, considerations ar
20、e given to the effect of other parameters on the results obtained. The focus of the studies in this document is on the band 5 925-6 875 MHz, because this band is heavily used by the FS. 2 System description and parameters The HAPS system under consideration in this study provides communication to fi
21、ve gateway stations. Figure 1, which is taken from Recommendation ITU-R F.1891, shows the geometric configuration of the system. The characteristics of the signals transmitted by the HAPS platform transmitter are the ones given in Recommendation ITU-R F.1891. They are summarized in Table 1. FIGURE 1
22、 Example of HAPS gateway station configuration and internal HAPS network interference F . 5- 10 06 - 01HAPS21 kmq1H A P S -G S5 4ab32fwN a di rU A C z oneN ot t o s c a l e . L ook a ngl e sa re c ons i de ra bl y d i s t ort e d.Want edsi gnalI nterferingsignalInterferingsi gnal36 kmra di usRec. IT
23、U-R F.2011 3 TABLE 1 Characterization of the HAPS platform transmitter Parameter Symbol Value Frequency (GHz) 6.5 Transmit power (dBW) 22 Bandwidth (MHz) 11 Transmit power density (dBW/MHz) Pt 32.4 Transmit feeder loss (dB) 4.1 Maximum antenna gain (dBi) Gtmax 30 Main beam 3 dB beamwidth (degrees) 5
24、.2 Reference antenna pattern bh degrees from maximum (dBi) Gh(bh) Resolution 221 (Rev.WRC-07) Height of HAPS platform (km) Ah 21.0 The following HAPS antenna is considered in these analyses: Resolution 221 (Rev.WRC-07) array antenna: This is the antenna pattern that appears in Resolution 221 (Rev.WR
25、C-07). It has a near side-lobe level of 25 dB below the main-beam gain of 30 dBi. The gain for angles more than 63 from the main-beam axis is 43 dBi as shown in Fig. 2. No working model of an antenna conforming to this pattern has been manufactured or demonstrated. FIGURE 2 Gain pattern for Resoluti
26、on 221, antenna having a maximum gain of 30 dBi F . 5- 1006- 02402002040600 10 20 30 40 50 60 70 80 90A ngl e (de gre e s )Antenagain(dBi)for30dBiantennaRe s ol ut i on 221 re fe re nc e a nt e nna pa t t e rn4 Rec. ITU-R F.2011 The characteristics assumed for the FS receiver are summarized in Table
27、 2. These values are consistent with values in Recommendation ITU-R F.758. TABLE 2 FS parameters Parameter Symbol Value Frequency (GHz) fGHz 6.5 Maximum antenna gain (dBi) Grmax 45.0 Reference antenna pattern gain br degrees from maximum (dBi) Gr(br) Recommendation ITU-R F.699 Antenna height (km) Af
28、 0.060 Antenna elevation angle (degrees) a 0.0 Feeder loss (dB) Lf 3.0 Receiver noise temperature (Kelvins) Teff 725 Reference bandwidth (MHz) B 1.0 Receiver noise floor (dBW/MHz) NT 140.0 The interfering signal power at a fixed service receiver is determined by the following equation: fbrrhhtr LLGG
29、PI bb )()( (1) where all terms have been defined in Tables 1 and 2 except for Lb, the propagation loss. The propagation loss is determined as: )l o g (20)l o g (204.92 kmGHzb dfL (2) where dkm is the length of the propagation path in kilometres from the HAPS platform transmitter to the FS receiving
30、antenna. The interference power is assumed to propagate on a straight line path within the plane of the great circle determined from the positions of the HAPS transmitter, the FS receiver, and the centre of the Earth where the Earth is assumed to have a radius (8 504 km) that is 4/3 of its actual va
31、lue (6 378 km). This allows the effect of atmospheric refraction to be taken into account. The I/N ratio used in this study is the difference between the value of the interference power Ir of equation (1) and the noise power NT given in Table 2 with both values given in dBW/MHz. 3 Interference crite
32、ria Before discussing the simulation methodologies it is necessary to determine the appropriate interference criteria to be applied in this sharing situation. The interference criteria used by the fixed service is considered to be a matter for each administration to decide. In the Radio Regulations
33、HAPS is considered to be an application within the fixed service; however, it is not clear how administrations would choose to treat it. For the purpose of discussion, a HAPS transmitting station will be treated here as any other FS transmitting station. Rec. ITU-R F.2011 5 At the present time there
34、 is no agreed value for acceptable interference from HAPS. On the assumption that the HAPS system is entering into an environment heavily used by the FS and already shared with the FSS, any new HAPS system, if permitted under RR No. 4.15A, should be allowed to add to the interference noise only incr
35、ementally. Assuming a 20% allowance for the total contribution of interference from all sources to the total noise, a value of 10% of this allowance could be allocated to HAPS interference. This would result in an I/N criterion of about 17 dB for HAPS systems. Administrations may choose other allowa
36、nces and allocations, but a range of I/N values between 10 and 20 dB would appear to be of the greatest interest. This is the range that will receive the greatest attention in the following developments. To cover all eventualities results have been calculated for all I/N ratios between 0 and 20 dB.
37、4 Description and application of the I/N methodology The I/N at an FS receiver, using the parameters specified in Tables 1 and 2, would depend on its position in the layout of Fig. 1 and on the azimuth of the main beam axis of its antenna. This section considers the case where the HAPS platform tran
38、smits to only a single gateway station on the surface of the Earth. All geographic locations are specified by their great circle distance from the point on the surface of the Earth that is directly below the HAPS platform. In HAPS terminology, the point on the surface of the Earth directly below the
39、 HAPS platform is often described as the HAPS nadir. In this Annex, it will be designated as the HAPS Sub-Platform Point (SPP). The other coordinate needed to specify a geographic location is the azimuth angle of the great circle path from the SPP to the point. This angle is measured at the HAPS SPP
40、 in a counter-clockwise direction from the azimuth to the gateway station. The method described in this section is to determine the locations where a given I/N level will be exceeded for the two extreme pointing azimuths of the FS antenna at each location. One case is where the azimuth of the FS rec
41、eiving antenna is directed along the great circle toward the HAPS SPP. The other is where the azimuth of the FS receiving antenna is directed 180 from the direction toward the HAPS SPP. The areas where a given I/N ratio will be exceeded for the case where the FS antenna is pointed toward SPP will be
42、 called a coordination area since a frequency coordination process would be needed to determine whether that I/N would be exceeded for a particular receiver. The geographical region, if any, where the I/N ratio would be exceeded for the case where the FS antenna is pointed away from SPP will be call
43、ed an exclusion zone because there is no pointing angle for which the I/N ratio would not be exceeded. As used in this Annex, an exclusion zone is specific to the model parameters and to the I/N value chosen for an interference criterion. The radial extent of a coordination or exclusion zone is dete
44、rmined by stepping along a great circle path from the HAPS SPP and determining at each step whether an edge of a particular I/N geographical region has been encountered. The calculation numbers successive areas on each azimuth where a threshold I/N ratio is exceeded. All of the elemental areas with
45、the same number are considered to be part of the same composite geographical region. Figure 3 shows the results of such a calculation for an I/N threshold of 20 dB using the HAPS array antenna transmitting to a gateway station that is 36 km from the SPP and using the parameters from Tables 1 and 2.
46、(The characteristic values of Tables 1 and 2 are used for all subsequent calculations unless otherwise noted.) The I/N threshold of 20 dB was chosen for Fig. 3 and the following figures to illustrate cases where exclusion zones exist. For this case, the coordination area is identified with the dotte
47、d line and the exclusion zone with the solid line. These areas surround the location of the gateway station and, therefore, must result from the coupling of the main-beam gain of the HAPS array to the side lobes of the FS antenna. Because the gain pattern of the HAPS array 6 Rec. ITU-R F.2011 antenn
48、a rolls off so rapidly with the angle from main-beam axis, there is no area due to the HAPS side lobes coupling energy to the main lobe of an FS receiving antenna for this case. Rather than provide plots for other I/N ratios, Table 3 summarizes the results for various I/N thresholds by tabulating th
49、e areas of the coordination area and exclusion zone for each I/N. For this example all of the entries in the Area 2 column are zero, which means that there is only one coordination area. The entries in the column for the area of Area 2 are zero and the entries for the total coordination area are the same as those for Area 1. Note that in cases where Area 2 is zero, Area 1 is a contiguous geographical region. Where Area 2 is not zero, the various components of Area 1 may not be contiguous. This result is discussed further in Section 6 of this Annex. When there is a g
