1、 Recommendation ITU-R P.452-16 (07/2015) Prediction procedure for the evaluation of interference between stations on the surface of the Earth at frequencies above about 0.1 GHz P Series Radiowave propagation ii Rec. ITU-R P.452-16 Foreword The role of the Radiocommunication Sector is to ensure the r
2、ational, 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 regulatory and policy functions of the Radi
3、ocommunication 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 for ITU-T/ITU-R/ISO/IEC referenced in Annex 1
4、 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 ITU-T/ITU-R/ISO/IEC and the ITU-R patent info
5、rmation 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 service (sound) BT Broadcasting service (televisio
6、n) 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 coordination between fixed-satellite and fixed service
7、 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. Electronic Publication Geneva, 2015 ITU 2015 Al
8、l rights reserved. No part of this publication may be reproduced, by any means whatsoever, without written permission of ITU. Rec. ITU-R P.452-16 1 RECOMMENDATION ITU-R P.452-16 Prediction procedure for the evaluation of interference between stations on the surface of the Earth at frequencies above
9、about 0.1 GHz (Question ITU-R 208/3) (1970-1974-1978-1982-1986-1992-1994-1995-1997-1999-2001-2003-2005-2007-2009-2013-2015) Scope This Recommendation contains a prediction method for the evaluation of interference between stations on the surface of the Earth at frequencies from about 0.1 GHz to 50 G
10、Hz, accounting for both clear-air and hydrometeor scattering interference mechanisms. Keywords Interference, Ducting, Tropospheric scatter, Diffraction, Hydrometeor Scattering, Digital Data Products The ITU Radiocommunication Assembly, considering a) that due to congestion of the radio spectrum, fre
11、quency bands must be shared between different terrestrial services, between systems in the same service and between systems in the terrestrial and Earth-space services; b) that for the satisfactory coexistence of systems sharing the same frequency bands, interference prediction procedures are needed
12、 that are accurate and reliable in operation and acceptable to all parties concerned; c) that propagation predictions are applied in interference prediction procedures which are often required to meet “worst-month” performance and availability objectives; d) that prediction methods are required for
13、application to all types of path in all areas of the world, recommends 1 that the interference prediction procedure given in Annex 1 be used for the evaluation of the available propagation loss over unwanted signal paths between stations on the surface of the Earth for frequencies above about 0.1 GH
14、z. Annex 1 1 Introduction Congestion of the radio-frequency spectrum has made necessary the sharing of many frequency bands between different radio services, and between the different operators of similar radio services. In order to ensure the satisfactory coexistence of the terrestrial and Earth-sp
15、ace systems 2 Rec. ITU-R P.452-16 involved, it is important to be able to predict with reasonable accuracy the interference potential between them, using propagation predictions and models which are acceptable to all parties concerned, and which have demonstrated accuracy and reliability. Many types
16、 and combinations of interference path may exist between stations on the surface of the Earth, and between these stations and stations in space, and prediction methods are required for each situation. This Annex addresses one of the more important sets of interference problems, i.e. those situations
17、 where there is a potential for interference between radio stations located on the surface of the Earth. The models contained within Recommendation ITU-R P.452 work from the assumption that the interfering transmitter and the interfered-with receiver both operate within the surface layer of atmosphe
18、re. Use of exceptionally large antenna heights to model operations such as aeronautical systems is not appropriate for these models. The prediction procedure has been tested for radio stations operating in the frequency range of about 0.1 GHz to 50 GHz. The models within Recommendation ITU-R P.452 a
19、re designed to calculate propagation losses not exceeded for time percentages over the range 0.001 p 50%. This assumption does not imply the maximum loss will be at p = 50%. The method includes a complementary set of propagation models which ensure that the predictions embrace all the significant in
20、terference propagation mechanisms that can arise. Methods for analysing the radio-meteorological and topographical features of the path are provided so that predictions can be prepared for any practical interference path falling within the scope of the procedure up to a distance limit of 10 000 km.
21、2 Interference propagation mechanisms Interference may arise through a range of propagation mechanisms whose individual dominance depends on climate, radio frequency, time percentage of interest, distance and path topography. At any one time a single mechanism or more than one may be present. The pr
22、incipal interference propagation mechanisms are as follows: Line-of-sight (Fig. 1): The most straightforward interference propagation situation is when a line-of-sight transmission path exists under normal (i.e. well-mixed) atmospheric conditions. However, an additional complexity can come into play
23、 when subpath diffraction causes a slight increase in signal level above that normally expected. Also, on all but the shortest paths (i.e. paths longer than about 5 km) signal levels can often be significantly enhanced for short periods of time by multipath and focusing effects resulting from atmosp
24、heric stratification (see Fig. 2). Diffraction (Fig. 1): Beyond line-of-sight (LoS) and under normal conditions, diffraction effects generally dominate wherever significant signal levels are to be found. For services where anomalous short-term problems are not important, the accuracy to which diffra
25、ction can be modelled generally determines the density of systems that can be achieved. The diffraction prediction capability must have sufficient utility to cover smooth-earth, discrete obstacle and irregular (unstructured) terrain situations. Tropospheric scatter (Fig. 1): This mechanism defines t
26、he “background” interference level for longer paths (e.g. more than 100-150 km) where the diffraction field becomes very weak. However, except for a few special cases involving sensitive receivers or very high power interferers (e.g. radar systems), interference via troposcatter will be at too low a
27、 level to be significant. Rec. ITU-R P.452-16 3 FIGURE 1 Long-term interference propagation mechanisms P .04 52 -01T r opo s phe r i c s c a t t e rD i f f r a c t i onL i ne - of - s i ght Surface ducting (Fig. 2): This is the most important short-term propagation mechanism that can cause interfere
28、nce over water and in flat coastal land areas, and can give rise to high signal levels over long distances (more than 500 km over the sea). Such signals can exceed the equivalent “free-space” level under certain conditions. FIGURE 2 Anomalous (short-term) interference propagation mechanisms P .04 52
29、 -02H ydr om e t e or s c a t t e rE l e va t e d l a ye rr e f l e c t i on/ r e f r a c t i onD uc t i ngL i ne - of - s i ght w i t hm ul t i pa t h e nha nc e m e nt s Elevated layer reflection and refraction (Fig. 2): The treatment of reflection and/or refraction from layers at heights up to a
30、few hundred metres is of major importance as these mechanisms enable signals to overcome the diffraction loss of the terrain very effectively under favourable path geometry situations. Again the impact can be significant over quite long distances (up to 250-300 km). 4 Rec. ITU-R P.452-16 Hydrometeor
31、 scatter (Fig. 2): Hydrometeor scatter can be a potential source of interference between terrestrial link transmitters and earth stations because it may act virtually omnidirectionally, and can therefore have an impact off the great-circle interference path. However, the interfering signal levels ar
32、e quite low and do not usually represent a significant problem. A basic problem in interference prediction (which is indeed common to all tropospheric prediction procedures) is the difficulty of providing a unified consistent set of practical methods covering a wide range of distances and time perce
33、ntages; i.e. for the real atmosphere in which the statistics of dominance by one mechanism merge gradually into another as meteorological and/or path conditions change. Especially in these transitional regions, a given level of signal may occur for a total time percentage which is the sum of those i
34、n different mechanisms. The approach in this procedure has been to define completely separate methods for clear-air and hydrometeor-scatter interference prediction, as described in 4 and 5 respectively. The clear-air method consists of separate models for diffraction, ducting/layer-reflection, and t
35、roposcatter. All three are applied for every case, irrespective of whether a path is LoS or transhorizon. The results are then combined into an overall prediction using a blending technique that ensures for any given path distance and time percentage that the signal enhancement in the equivalent not
36、ional line-of-sight model is the highest attainable. 3 Clear-air interference prediction 3.1 General comments Although the clear-air method is implemented by three separate models, the results of which are then blended, the procedure takes account of five basic types of propagation mechanism: line-o
37、f-sight (including signal enhancements due to multipath and focusing effects); diffraction (embracing smooth-earth, irregular terrain and sub-path cases); tropospheric scatter; anomalous propagation (ducting and layer reflection/refraction); height-gain variation in clutter (where relevant). 3.2 Der
38、iving a prediction 3.2.1 Outline of the procedure The steps required to achieve a prediction are as follows: Step 1: Input data The basic input data required for the procedure is given in Table 1. All other information required is derived from these basic data during the execution of the procedure.
39、Rec. ITU-R P.452-16 5 TABLE 1 Basic input data Parameter Preferred resolution Description f 0.01 Frequency (GHz) p 0.001 Required time percentage(s) for which the calculated basic transmission loss is not exceeded t, r 0.001 Latitude of station (degrees) t, r 0.001 Longitude of station (degrees) htg
40、, hrg 1 Antenna centre height above ground level (m) hts, hrs 1 Antenna centre height above mean sea level (m) Gt, Gr 0.1 Antenna gain in the direction of the horizon along the great-circle interference path (dBi) Pol N/A Signal, e.g. vertical or horizontal NOTE 1 For the interfering and interfered-
41、with stations: t : interferer r : interfered-with station. Polarization in Table 1 is not a parameter with a numerical value. The information is used in 4.2.2.1 in connection with equations (30a), (30b) and (31). Step 2: Selecting average year or worst-month prediction The choice of annual or “worst
42、-month” predictions is generally dictated by the quality (i.e. performance and availability) objectives of the interfered-with radio system at the receiving end of the interference path. As interference is often a bidirectional problem, two such sets of quality objectives may need to be evaluated in
43、 order to determine the worst-case direction upon which the minimum permissible basic transmission loss needs to be based. In the majority of cases the quality objectives will be couched in terms of a percentage “of any month”, and hence worst-month data will be needed. The propagation prediction mo
44、dels predict the annual distribution of basic transmission loss. For average year predictions the percentages of time p, for which particular values of basic transmission loss are not exceeded, are used directly in the prediction procedure. If average worst-month predictions are required, the annual
45、 equivalent time percentage, p, of the worst-month time percentage, pw, must be calculated for the path centre latitude using: %10 078.0816.0 444.0186.0)l o g ()l o g ( Lw Gpp (1) where: : fraction of the path over water (see Table 3). 45fo r2c o s1.145fo r2c o s1.17.07.0LG (1a) If necessary the val
46、ue of p must be limited such that 12 p pw. Note that the latitude (degrees) is deemed to be positive in the Northern Hemisphere. 6 Rec. ITU-R P.452-16 The calculated result will then represent the basic transmission loss for the required worst-month time percentage, pw%. Step 3: Radiometeorological
47、data The prediction procedure employs three radio-meteorological parameters to describe the variability of background and anomalous propagation conditions at the different locations around the world. N (N-units/km), the average radio-refractive index lapse-rate through the lowest 1 km of the atmosph
48、ere, provides the data upon which the appropriate effective Earth radius can be calculated for path profile and diffraction obstacle analysis. Note that N is a positive quantity in this procedure. 0 (%), the time percentage for which refractive index lapse-rates exceeding 100 N-units/km can be expec
49、ted in the first 100 m of the lower atmosphere, is used to estimate the relative incidence of fully developed anomalous propagation at the latitude under consideration. The value of 0 to be used is that appropriate to the path centre latitude. N0 (N-units), the sea-level surface refractivity, is used only by the troposcatter model as a measure of location variability of the troposcatter scatter mechanism. As the scatter path calculation is based on a path geometry determined by annual or worst-month values
