1、 Recommendation ITU-R F.1107-2(05/2011)Probabilistic analysis for assessing interference into the fixed service from satellites using the geostationary orbitF SeriesFixed serviceii Rec. ITU-R F.1107-2 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient
2、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 regulatory and policy functions of the Radiocommunication Sector are perf
3、ormed 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 for ITU-T/ITU-R/ISO/IEC referenced in Annex 1 of Resolution ITU-R 1. Forms
4、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 ITU-T/ITU-R/ISO/IEC and the ITU-R patent information database can also be f
5、ound. 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 service (sound) BT Broadcasting service (television) F Fixed service M Mobile, r
6、adiodetermination, 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 coordination between fixed-satellite and fixed service systems SM Spectrum managemen
7、t 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. Electronic Publication Geneva, 2011 ITU 2011 All rights reserved. No part of
8、this publication may be reproduced, by any means whatsoever, without written permission of ITU. Rec. ITU-R F.1107-2 1 RECOMMENDATION ITU-R F.1107-2*Probabilistic analysis for assessing interference into the fixed service from satellites using the geostationary orbit (1994-2002-2011) Scope This Recom
9、mendation provides methods for assessing sharing criteria for interference from satellites using the geostationary orbit into digital fixed wireless systems. Annex 1 provides the approach to calculate interference into digital systems, and provides an outline of a calculation methodology and include
10、s examples and a software model to implement the methodology. The ITU Radiocommunication Assembly, considering a) that emissions from space stations operating in the geostationary orbit and sharing the same spectrum may produce interference in receiving stations of the fixed service (FS); b) that it
11、 may be impractical to coordinate between the many terrestrial stations and the many space stations, and that, therefore, sharing criteria should be established to preclude the need for detailed coordination; c) that in devising such sharing criteria, account needs to be taken of the operational and
12、 technical requirements of networks in the satellite service as well as of the requirements of the FS and measures available to them; d) that it has been determined that a probabilistic basis for developing sharing criteria results in a more efficient use of the spectrum than from criteria developed
13、 using worst case analysis; e) that it is difficult and burdensome to assemble sufficient statistically accurate information about real existing and planned terrestrial and satellite system stations; f) that computer simulations of FS and satellite services operating in the geostationary orbit can g
14、enerate statistically accurate information suitable for determining sharing criteria for a wide variety of sharing scenarios, recommends 1 that information derived from computer simulations of FS and satellite services operating from the geostationary orbit and using the same spectrum may be accepta
15、ble for developing sharing criteria; 2 that when developing sharing criteria with respect to digital systems in the FS, the material in Annex 1 to assess interference from FS into digital FS should be taken into account. *This Recommendation should be brought to the attention of Radiocommunication S
16、tudy Groups 4, 6 and 7. 2 Rec. ITU-R F.1107-2 Annex 1 Information for assessing the interference into digital fixed service systems from emissions of space stations operating in the geostationary orbit 1 Introduction This Annex presents additional information that is necessary for assessing the inte
17、rference into such FS systems employing digital modulation. The methodology provides statistics for both the interference-to-noise ratio (I/N) values of individual stations and the fractional degradation of performance (FDP) values of routes. The methodology employed for assessing the route FDP as d
18、escribed in 3 is only valid when the I/N of a receiver station of that route is not so large as to drive the receiver into a non-linear range. The user is therefore encouraged to assess the I/N per receiver statistics, as described in 2, before assessing the FDP statistics on a multihop basis, as de
19、scribed in 3. This Annex applies to digital FS systems where multipath fading generally predominates and does not apply to those systems where precipitation attenuation generally predominates. 2 Station-by-station analysis In the case of digital point-to-point (P-P) and point-to-multipoint (P-MP) FS
20、 systems, it is appropriate to evaluate interference in terms of FDP as defined for the time varying interference from non-geostationary satellites in Annex 3 to Recommendation ITU-R F.1108. As an analogy, when there is only one FS station, FDPhopdue to interference entries from geostationary satell
21、ites can be defined at the input of a receiver as follows, taking into account that the interference level is almost time-invariant: ThopNIFDP = (1) where: I : aggregate interference (W/MHz) from visible satellites into the FS receiver NT: receiver thermal noise (W/MHz). A methodology proposed in Ap
22、pendix 2 of this Annex may be used for evaluating the I/N statistics. When it is necessary to determine the effect of interference on digital FS receivers employing diversity, a different formula may be more appropriate for evaluating FDPhopas described in Annex 4 to Recommendation ITU-R F.1108. 3 M
23、ulti-hop P-P FS systems For digital FS systems with n hops operating at frequencies where multipath fading generally predominates and acknowledging that, in general, the performance objectives for multi-hop P-P FS systems are specified on a route basis, two probabilistic assessment methods may be em
24、ployed. One Rec. ITU-R F.1107-2 3 is described in 2 and another is to evaluate the FDP for the route defined as the ratio of total interference power to total noise power for one direction of a route as follows: TnkkrouteNnIFDP=1)(2) where Ikis the aggregate interference falling into the k-th receiv
25、er from visible satellites. It should be noted that equation (2) is based on the assumptions that: the digital signal is regenerated at each repeater; the fading has Rayleigh characteristics. It should also be noted that, for evaluating FDProutefor digital FS systems employing diversity, an appropri
26、ate formula different from equation (2) should be used. Further studies are required. Although there are a variety of fading types, Rayleigh fading is regarded as the most severe fading encountered in line-of-sight paths and is a determining factor in the evaluation of FS system performance. The fea
27、ture of Rayleigh fading is that the probability of 10 dB deeper fading, for example, becomes smaller by a factor of 1/10. Therefore, if there exists a time-invariant interference in a hop whose level is equal to the thermal noise level (I/N = 0 dB), the probability of severely errored seconds (or th
28、e probability of unavailable time) will become twice as much as that of the case where there is no interference. The FDP concept has certain limitations, the most important assumption is that the FS receiver operation remains within a linear response range. If there is an exceptionally high level of
29、 interference so that the FS receiver operation falls into a non-linear response range, the FDP concept will not apply or will underestimate the effect of interference (see paragraph following equation (16) in Annex 3 to Recommendation ITU-R F.1108). However, as long as the FS receiver operation is
30、maintained within a linear response range, equation (2) is valid for multi-hop FS digital systems. The discussion in the preceding section does not result in a conclusion that only FDP should be evaluated on a route basis. Station basis evaluation of FDP will be also useful for understanding the eff
31、ects of interference. A typical hop distance of long haul systems is assumed to be 50 km, but a shorter hop distance may be appropriate for short haul systems, depending on various factors including the operating frequency and propagation effects. For example, in the case of an operating frequency i
32、n the 1-3 GHz range, random selection between specified limits (e.g. between 10 and 30 km) may be appropriate as typical hop distances. FS routes under survey should be selected according to the Monte Carlo simulation approach with the route starting point randomly selected within a user specified t
33、est box identified by latitude and longitude limits. In performing route analysis for digital systems subject to multipath fading, it may not be necessary that each individual hop meets the I/N criterion. The overall route performance, however, must meet the fractional degradation of performance cri
34、terion. This issue is explained below. Where multipath is the dominant fade mechanism, Recommendation ITU-R P.530 relates the probability of an outage on a hop P(hop outage) to the link thermal fade margin (TFM): P(hop outage) = K d 3.6 f 0.89 (1 + | hr he|/d )1.4 10TFM/104 Rec. ITU-R F.1107-2 where
35、: K : geoclimatic factor d : link length (km) f : frequency (GHz) hrand he: transmit and receive antenna heights (metres above sea level or another common reference) TFM : thermal fade margin on a hop (dB). CNCNCTFMTlog10= where: :log10TNCunfaded carrier-to-noise ratio (C/N) (dB) CNC : value of C/N
36、at which the performance criterion is just met (dB). Setting K d 3.6 f 0.89 (1 + | hr he|/d)1.4 10CNC/10= Then: P(hop outage) = NT/C Thus P(hop outage before satellite interference) = NT/C P(hop outage after aggregate satellite interference) = (NT+ I )/C where C, NTand I are in consistent power unit
37、s. If it is assumed that: each hop is designed to have a similar nominal probability of outage before satellite interference; hop fades are independent and sufficiently rare that the outage probabilities may be added, then the net nominal probability of outage for the route is: P(route outage) = (P(
38、hop outage)number of hops in route Thus, the fractional increase in the probability of a route outage due to a degraded fade margin on each hop within the route is simply: FDP(route outage) )()()(ceinterferenwithoutoutageroutePceinterferenwithoutoutageroutePceinterferenwithoutagerouteP= +=)/()/()/)(
39、CNCNCINTTT=TNIRec. ITU-R F.1107-2 5 i.e. the route FDP is the total route interference power divided by the total route noise power: ratiopoweraasTNnI= %100TNnI= Thus the FDP approach for the assessment of the impact of interference on a FS route and the usage of percentages (rather than dB) is appr
40、opriate. In P-MP systems, most links are single hop therefore equation (1) would apply. In P-P systems, multihop deployments are typical, therefore equation (2) will apply. 4 P-MP FS systems Interference to hub stations in P-MP systems should be evaluated according to 2 in the case of digital modula
41、tion, but it should be noted that these stations employ omnidirectional or sectoral antennas. Reference radiation patterns in the elevation plane for such antennas are described in Recommendation ITU-R F.1336. If appropriate, the effect of downward beam tilting of the antennas may be evaluated in th
42、e interference assessment. Interference into subscriber stations in P-MP FS systems should also be evaluated according to 2 in the case of digital modulation. For this case, it is generally assumed that the azimuthal directions of subscriber station antennas are uniformly distributed over 0-360 noti
43、ng that, in general, orbit avoidance is not feasible for these systems. 5 Test area A large number of FS routes and stations (to ensure stability and convergence of the statistics) are randomly distributed in latitude, longitude and azimuth in a user-defined test area. To ensure a uniform exposure t
44、o all arrival angles, the test area longitude dimension should be an integral multiple of the satellite spacing in the case of uniformly spaced satellites and the latitude dimension of the test area should be sufficiently large. Alternatively, the test area can be defined to encompass an administrat
45、ions territory so that parameters specific to that administrations systems may be evaluated. In this case, the satellite locations may be specified. 6 Satellite constellation A full orbit of equally spaced satellites is usually assumed when investigating a new satellite service. Alternatively, user-
46、defined satellite locations should be accommodated. Another option would permit random locations within a specified orbital arc. The model should permit orbit avoidance in those situations where this technique is practical for the FS. In general, ubiquitous deployment FS systems cannot take advantag
47、e of this technique. 7 pfd mask All satellites are assumed to transmit the maximum levels allowed by the assumed pfd mask. This is a conservative assumption with respect to the level of interference. The mask consists of straight-line segments of pfd versus arrival angle (from 0 to 90). The model sh
48、ould allow multiple segments to be specified. 6 Rec. ITU-R F.1107-2 Statistical pfd masks to account for satellite service area coverages may also be derived. Further studies are required. 8 FS parameters The noise figure (or thermal noise floor) and feeder loss common to all FS stations in the comp
49、uter simulation must be specified. In addition, the common antenna gain and pattern must be specified. The following default patterns could be included in an antenna file for selection by the user, for example: Recommendation ITU-R F.1245, recommends 2, for P-P systems co-polar with the interferers. Recommendation ITU-R F.1245, Note 7, for P-P systems with linear/circular discrimi-nation in main beam-to-main beam coupling conditions. Recommendation ITU-R F.1245, Annex 1, for P-P system
