1、 Rec. ITU-R M.1654 1 RECOMMENDATION ITU-R M.1654*A methodology to assess interference from broadcasting-satellite service (sound) into terrestrial IMT-2000 systems intending to use the band 2 630-2 655 MHz (Question ITU-R 229/8) (2003) Summary This Recommendation is an example methodology to assess
2、the interference from BSS (sound) into terrestrial IMT-2000 systems intending to use the band 2 630-2 655 MHz and that could be used to determine the impact of BSS (sound) on terrestrial IMT-2000 in the context of co-frequency sharing through the development of pfd masks, where applicable. This meth
3、odology contains an algorithm that can be used to calculate a single entry pfd mask for BSS (sound) satellites for a given scenario to meet an Isat/Nth criterion within a tolerance of 1 dB at any location on the Earth. Attachment 1 to Annex 1 sets out an example of the application of a methodology a
4、ssessing the possible impact in terms of a loss of coverage or cell size reduction. It has been recognized that the interference into a cellular network can be assessed in terms of coverage reduction (particularly in noise-limited networks such as in rural areas) as well as in terms of availability
5、reduction (particularly in capacity-limited networks such as in urban areas). These approaches may be complementary, and additional study is required on these further aspects. Further study is required on alternative example methods assessing the possible impact. The use of this Recommendation to ca
6、lculate pfd values in the context of co-frequency sharing should carefully take into account all parameters including operational constraints on BSS (sound) systems, as well as the likely different IMT-2000 sharing scenarios. In particular, it should be noted that if this Recommendation is used to d
7、erive pfd values to be applied as hard limits, worst-case assumptions are not deemed appropriate. As this Recommendation contains a methodology for assessing multiple satellite interference, its use is not advised in the process of coordination. The ITU Radiocommunication Assembly, considering a) th
8、at a methodology is required to assess the possible aggregate interference from BSS (sound) into terrestrial IMT-2000 systems intending to use the band 2 630-2 655 MHz and for the development of pfd masks, where applicable, with a view to achieving the objectives in Resolutions 223 (WRC-2000) and 53
9、9 (WRC-2000), *NOTE The following countries Saudi Arabia, Djibouti, Egypt, United Arab Emirates, Jordan, Kuwait, Morocco, Mauritania, Syrian Arab Republic, Tunisia and Yemen object to the approval of this Recommendation and are not bound by it. 2 Rec. ITU-R M.1654 recognizing a) that Resolution 539
10、(WRC-2000), inter alia, contains provisional pfd threshold levels for BSS (sound) systems using non-GSO satellites in the band 2 630-2 655 MHz; b) that Resolution 539 (WRC-2000) invites ITU-R to conduct the necessary technical studies in time for WRC-03 relating to frequency sharing between systems
11、in the BSS (sound) and terrestrial services in the band 2 535-2 655 MHz with a view to avoid placing undue constraints on either service, recommends 1 that the example methodology described in Annex 1 of this Recommendation could be used to assess interference from, and possible impact of, BSS (soun
12、d) on terrestrial IMT-2000 systems intending to use the band 2 630-2 655 MHz in the context of co-frequency operation through the development of pfd masks. NOTE 1 The example methodology described in Annex 1 of this Recommendation may also be applied for assessing interference of co-frequency operat
13、ion involving any satellite service system using various orbital configurations, including the geostationary orbit or highly elliptical orbit types. Annex 1 A methodology to assess interference from BSS (sound) into terrestrial IMT-2000 systems intending to use the band 2 630-2 655 MHz 1 Input data
14、and scenarios 1.1 Characteristics of the systems A given scenario will consist of BSS (sound) satellite networks using non-GSO space stations employing highly-elliptical orbits (HEO) and/or space stations using the GSO interfering into terrestrial IMT-2000 systems (base and/or mobile stations). Sect
15、ions 1.1.11and 1.1.2 list the necessary parameters, respectively for terrestrial IMT-2000 stations and BSS (sound) systems, to assess aggregate interference from BSS (sound) to terrestrial IMT-2000 stations. 1.1.1 Terrestrial IMT-2000 stations Receiver characteristics: thermal noise level; noise fac
16、tor. 1Additional system specific input parameters for terrestrial IMT-2000 stations would be required for usage of Methods 2a and 2b in 3.1.2. The detailed list of these parameters is provided in Attachment 1. Rec. ITU-R M.1654 3 Antenna characteristics: maximum gain; polarization; feed loss; 3 dB b
17、eamwidth2; vertical and azimuthal antenna radiation patterns over a range of elevation angles2; downtilt of the antenna2; site sectorization2. Location of the receivers (for example, an area bounded by latitude(s) and longitude(s) data). 1.1.2 BSS (sound) systems The various combination of a constel
18、lation of BSS (sound) systems that could operate in the 2 630-2 655 MHz band should be in accordance with the expected number of co-frequency satellites visible at the same location on the surface of the Earth. These may include non-GSO and/or GSO satellites. GSO satellites, assumed equally spaced a
19、cross the GSO arc: nominal geographical longitude on the geostationary satellite orbit. For non-GSO HEO satellite systems, the following parameters are to be provided: number of orbital planes, number of space stations per orbital plane and number of space stations simultaneously transmitting on the
20、 active arc, period of the space stations; altitude and longitude of the apogee and perigee for each space station; inclination angle for each orbital plane with respect to Earth equatorial plane; start and end of the active arc for each space station. Interference produced by BSS (sound) satellites
21、 is typically modelled by pfd masks as a function of elevation angle (dB(W/(m2 MHz)3. Information on the polarization used by the satellite transmitters would be required to assess polarization discrimination if needed (see factor Piin equations (1) and (2) in 3.1.1). There are two approaches to the
22、 analysis. These are: static approach the location of the satellite is fixed at a single point; orbital simulation approach time variation of the satellite is included4. 2Only applies to base station receivers. 3The modelling by this method may result in a worst-case situation of interference from G
23、SO BSS (sound) satellites. 4It is considered that this approach, while requiring more complex simulation tools, will produce more accurate results. 4 Rec. ITU-R M.1654 2 Presentation of the results The results should be expressed in terms of Isat/Nth received at each receiver (in the case of sectora
24、l base station receivers, one receiver per sector should be used). It is recognized that when assessing interference from satellite systems into an IMT-2000 network, the effect of this interference would be spread over large areas, thus leading to an interference assessment in terms of Isat/Nth5. It
25、 may also include results of Isat/Nth which take into account the combined impact for each base station sector coverage area of the receiver. The results should be expressed in a transparent, simple and comprehensive manner. 3 Method of calculation and production of the results 3.1 Assessment of the
26、 interference into an IMT-2000 base station 3.1.1 Aggregation of the interference from multiple satellites into a given IMT-2000 base station receiver The calculation steps for the aggregation of the interference from satellites is summarized below: considering a set of non-GSO and/or GSO satellites
27、 orbiting around Earth; considering assumed pfd masks at the Earths surface used to model the emissions of each non-GSO and/or GSO satellite; considering an IMT-2000 base station with sectoral antenna, characterized by its latitude, longitude, orientation and tilt angle; calculate the azimuth, eleva
28、tion and off-axis angles between the IMT-2000 base station and each satellite of the assumed constellation; calculate the aggregate interference at the receiver entrance from all visible satellites (i.e., whose elevation angle is positive) with an overlapping bandwidth with terrestrial IMT-2000 and
29、the subsequent Isat/Nth IMT-2000 base station receiver (sector) at a given latitude and longitude (lat, long), and pointing in a given direction (orientation, tilt angle). The subsequent Isat/Nth is given by the following formula: +=10/)4/(log10)_,_()_(101log10, 2_1iisatniPFLielevationriazimuthrGiel
30、evationpfdNthangletiltnorientatiolonglatNthIsat(1) 5The use of C/(N + I) interference assessment into IMT-2000 is only used in contexts where interference impacts only a limited numbers of cells. Such assessment is not suitable for situations involving satellite interference into large numbers of st
31、ations of different networks where wanted signal carrier power levels vary for each user with factors such as time, traffic loading, user location and power control. Rec. ITU-R M.1654 5 where: Isat/Nth (lat, long, orientation, tilt angle) : is the resulting aggregate Isat/Nth from all visible space
32、stations with an overlapping bandwidth with terrestrial IMT-2000 at the IMT-2000 receiver (dB) pfdi(elevation_i) : pfd at the terrestrial IMT-2000 station from visible BSS (sound) space station i (dB(W/(m2 MHz) elevation_i : elevation of the space station i seen from the IMT-2000 base station (it is
33、 the angle of arrival of the space station i incident wave to the IMT-2000 base station, above the horizontal plane) (degrees) G(r_azimuth_i, r_elevation_i) : off-axis gain of the IMT-2000 base station sector towards the space station i (dBi) r_azimuth_i : relative azimuth of the space station i see
34、n from the IMT-2000 base station sector (it is determined by the difference between the azimuth of the space station i seen from the base station and the azimuth of the orientation of the IMT-2000 base station sector) (degrees) r_elevation_i : relative elevation of the space station i (the angle of
35、arrival of the space station i incident wave to the IMT-2000 base station, above the horizontal plane, plus the tilt angle of the IMT-2000 base station (a downtilt angle has a positive value) (degrees) : wavelength (m) FL : terrestrial IMT-2000 receiver feeder loss (dB) Pi: expected averaged polariz
36、ation discrimination between transmitting antenna of space station i and the IMT-2000 base station receiving antenna (dB) n_sat : number of satellites Nth : terrestrial IMT-2000 station receiver thermal noise (W/MHz). 6 Rec. ITU-R M.1654 In the static approach, the non-GSO HEO type satellite(s) is (
37、are) assumed to transmit at its (their) apogee. In the orbit simulation approach, the HEO satellite is transmitting from its simulated location on the active arc at each time increment and equation (1) is computed for each time increment (t) and becomes equation (2): +=10/)()4/(log10)(_),(_()(_(101l
38、og10, 2_1tPFLtielevationrtiazimuthrGtielevationpfdNthtangletiltnorientatiolonglatNthIsatiisatni(2)The notations in equation (2) have equivalent meaning to those in equation (1). The static approach enables tables or figures recording Isat/Nth values at the terrestrial IMT-2000 receiver to be determi
39、ned as a function of the relative longitude, latitude, tilt angle and orientation of the terrestrial IMT-2000 station for a given distribution of BSS (sound) satellites transmitting at their pfd mask. The orbit simulation approach can produce further combined information on the received interference
40、 with the corresponding time duration, or the percentage of time a given Isat/Nth level of interference is experienced. 3.1.2 Assessment of the interference received at a given IMT-2000 site In addition to the assessment of the interference received at an IMT-2000 individual sector, it may be of int
41、erest to consider also the impact of the interference into IMT-2000 sites, taking into account the combined impact on each sector area. The combined impact of the satellite interference over a site is to be evaluated in regard to the particular concerns of the scenario envisaged. For example, in cas
42、es where rural areas are of special concern, the impact on the loss of coverage is of the more critical impact on the system, and additional base stations would be required to overcome the effect of the interference. In this case, the interference threshold can be specified as an Isat/Nth derived fr
43、om a loss of coverage analysis. In other words, it is also an evaluation of the percentage of the number of base stations needed to overcome the effect of interference on an IMT-2000 site deployment scheme. With single sector cells, using azimuth independent antennas, this Isat/Nth can be directly c
44、ompared against the value determined during simulation. However, with three sectors/cell, and if each sector has its own receiver, then three Isat/Nths will be calculated. Rec. ITU-R M.1654 7 Figure 1 shows the key elements that need to be considered: 1654-01Direction ofinterferenceSector reducedby
45、interferenceNormalsector sizeAverage sectorsizeAll sectors assumedreduced by interferenceSector-2Sector-3Base stationSector-1FIGURE 1Impact on three-sector cell of direction dependent interferenceIn Fig. 1, interference reduces the coverage of Sector 1 but not Sectors 2 and 3. The actual impact over
46、 a large area would depend upon cell planning. Below, are three approaches suggested to calculate the Isat/Nths: Method 1 (worst case): assumes cell planning is undertaken with the minimum base station (BS) spacing distance in all azimuths, i.e.: =NthIsatNthIsatNthIsatNthIsatsectorsectorsector 321,m
47、ax(3) where: Isatsectori/Nth : Isat/Nth value calculated in sector i. Method 2a (average): calculate the average loss of coverage over the three sectors and convert back into an Isat/Nth, which is equivalent to assuming cell planning optimizes the network such that the distance between BS varies by
48、azimuth to exactly adjust for interference: = +NthIsatANthIsatANthIsatANthIsatAsectorsectorsectorsectorsectorsectorcell33221131(4) where Acellis the average cell site area in presence of interference, as a combination of each compounding sector areas Asector1, Asector2and Asector3, which are the sec
49、tor areas for cells 1, 2 and 3 receiving interference Isatsector1, Isatsector2and Isatsector3respectively. The detailed calculation steps can be found in Appendix 1. 8 Rec. ITU-R M.1654 Method 2b (weighted average): assumes that cell planning is between the worst and best values, and calculates the weighted average loss of coverage over the three sectors and converts back into an adjusted Isat/Nth (see also Att
