1、 Recommendation ITU-R P.1812-4 (07/2015) A path-specific propagation prediction method for point-to-area terrestrial services in the VHF and UHF bands P Series Radiowave propagation ii Rec. ITU-R P.1812-4 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, effici
2、ent 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
3、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 of Resolution ITU-R 1. Fo
4、rms 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
5、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 (television) F Fixed service M Mobil
6、e, 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 systems SM Spectrum manag
7、ement 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 All rights reserved. No part
8、 of this publication may be reproduced, by any means whatsoever, without written permission of ITU. Rec. ITU-R P.1812-4 1 RECOMMENDATION ITU-R P.1812-4 A path-specific propagation prediction method for point-to-area terrestrial services in the VHF and UHF bands (Question ITU-R 203/3) (2007-2009-2012
9、-2013-2015) Scope This Recommendation describes a propagation prediction method suitable for terrestrial point-to-area services in the frequency range 30 MHz to 3 GHz. It predicts signal levels at the median of the multipath distribution exceeded for a given percentage of time, p%, in the range 1% p
10、 50% and a given percentage of locations, pL, in the range 1% pL 99%. The method provides detailed analysis based on the terrain profile. The method is suitable for predictions for radiocommunication systems utilizing terrestrial circuits having path lengths from 0.25 km up to about 3 000 km distanc
11、e, with both terminals within approximately 3 km height above ground. It is not suitable for propagation predictions on either air-ground or space-Earth radio circuits. This Recommendation complements Recommendation ITU-R P.1546. The ITU Radiocommunication Assembly, considering a) that there is a ne
12、ed to give guidance to engineers in the planning of terrestrial radiocommunication services in the VHF and UHF bands; b) that, for stations working in the same or adjacent frequency channels, the determination of the minimum geographical distance of separation required to avoid unacceptable interfer
13、ence due to long-distance terrestrial propagation is a matter of great importance, noting a) that Recommendation ITU-R P.528 provides guidance on the prediction of point-to-area path loss for the aeronautical mobile service for the frequency range 125 MHz to 30 GHz and the distance range up to 1 800
14、 km; b) that Recommendation ITU-R P.452 provides guidance on the detailed evaluation of microwave interference between stations on the surface of the Earth at frequencies above about 0.7 GHz; c) that Recommendation ITU-R P.617 provides guidance on the prediction of point-to-point (P-P) path loss for
15、 trans-horizon radio-relay systems for the frequency range above 30 MHz and for the distance range 100 to 1 000 km; d) that Recommendation ITU-R P.1411 provides guidance on prediction for short-range (up to 1 km) outdoor services; e) that Recommendation ITU-R P.530 provides guidance on the predictio
16、n of P-P path loss for terrestrial LoS systems; f) that Recommendation ITU-R P.1546 provides guidance on the prediction of point-to-area field strengths in the VHF and UHF bands based principally on statistical analyses of experimental data; g) that Recommendation ITU-R P.2001 provides a wide-range
17、terrestrial propagation model for the frequency range 30 MHz to 50 GHz including both fading and enhancement statistics which is well suited for use in Monte-Carlo simulations; 2 Rec. ITU-R P.1812-4 h) that Recommendation ITU-R P.2040 provides guidance on the effects of building material properties
18、and structures on radiowave propagation, recommends that the procedure given in Annex 1 should be used for the detailed evaluation of point-to-area signal levels in connection with these services. NOTE Long range propagation paths may also occur at VHF via the ionosphere. These modes are summarized
19、in Recommendation ITU-R P.844. Annex 1 1 Introduction The propagation prediction method described in this Annex is recommended for the detailed evaluation of signal levels suitable for use in connection with terrestrial point-to-area services in the VHF and UHF bands. It predicts the signal level (i
20、.e. electric field strength) exceeded for a given percentage, p%, of an average year in the range 1% p 50% and pL% locations in the range 1% pL 99%. Therefore, this method may be used to predict both the service area and availability for a desired signal level (coverage), and the reductions in this
21、service area and availability due to undesired, co- and/or adjacent-channel signals (interference). The propagation model of this method is symmetric in the sense that it treats both radio terminals in the same manner. From the models perspective, it does not matter which terminal is the transmitter
22、 and which is the receiver. However, for convenience in the models description, the terms “transmitter” and “receiver” are used to denote the terminals at the start and end of the radio path, respectively. The method is first described in terms of calculating basic transmission loss (dB) not exceede
23、d for p% time for the median value of locations. The location variability element is then characterized statistically with respect to receiver locations, in addition to the building entry loss element from Recommendation ITU-R P.2040. A procedure is then given for converting to electric field streng
24、th (dB(V/m) for an effective radiated power of 1 kW. This method is intended primarily for use with systems using low-gain antennas. However, the change in accuracy when high-gain antennas are used only affects the troposcatter element of the overall method, and the change in the predictions is smal
25、l. For example, even with 40 dBi antennas at both ends of the link the over-estimation of troposcatter signals will amount to only about 1 dB. The method is suitable for predictions for radiocommunication systems utilizing terrestrial circuits having path lengths from 0.25 km up to about 3 000 km di
26、stance, with both terminals within approximately 3 km height above ground. It is not suitable for propagation predictions on either air-ground or space-Earth radio circuits. The propagation prediction method in this Annex is path-specific. Point-to-area predictions using this method consist of serie
27、s of many P-P (i.e. transmitter-point-to-receiver-multipoint) predictions, uniformly distributed over notional service areas. The number of points should be large enough to ensure that the predicted values of basic transmission losses or field strengths thus obtained are reasonable estimates of the
28、median values, with respect to locations, of the corresponding quantities for the elemental areas that they represent. Rec. ITU-R P.1812-4 3 In consequence, it is assumed that users of this Recommendation are able to specify detailed terrain profiles (i.e. elevations above mean sea level) as functio
29、ns of distance along the great circle paths (i.e. geodesic curves) between the terminals, for many different terminal locations (receiver-points). For most practical applications of this method to point-to-area coverage and interference predictions, this assumption implies the availability of a digi
30、tal terrain elevation database, referenced to latitude and longitude with respect to a consistent geodetic datum, from which the terrain profiles may be extracted by automated means. If these detailed terrain profiles are not available, then Recommendation ITU-R P.1546 should instead be used for pre
31、dictions. In view of the foregoing, the location variability element of this Recommendation and the building entry loss model element of Recommendation ITU-R P.2040 are characterized via the statistics of lognormal distributions with respect to receiver locations. Although this statistical character
32、ization of the point-to-area propagation problem would appear to make the overall model unsymmetrical (i.e. non-reciprocal), users of this Recommendation should note that the location variability could, in principle, be applied at either end of the path (i.e. either terminal), or even both (i.e. the
33、 transmitter and the receiver). However, the location variability correction is only meaningful in situations when exact location of a given terminal is unknown and a statistical representation over that terminals potential locations is required. There are unlikely to be many situations where this c
34、ould meaningfully be applied to the transmitter location. If the locations of both terminals are known exactly and this procedure is being used in P-P mode, then this Recommendation is only applicable with pL = 50%. A similar point is true regarding building entry losses. The argument is slightly mo
35、re complicated than for location variability owing to the fact that the median entry loss correction is non-zero. At the transmitter end, users should also add the building entry loss to the basic transmission loss if the transmitter is inside a building, but users must also be aware that the use of
36、 median loss values may be misleading if the transmitter is not in a “median” location. 2 Model elements of the propagation prediction method This propagation prediction method takes account of the following model elements: line-of-sight (LoS) diffraction (embracing smooth-Earth, irregular terrain a
37、nd sub-path cases) tropospheric scatter anomalous propagation (ducting and layer reflection/refraction) height-gain variation in clutter location variability building entry losses (from Recommendation ITU-R P.2040). 3 Input parameters 3.1 Basic input data Table 1 describes the basic input data, whic
38、h defines the radio terminals, the frequency, and the percentage time and locations for which a prediction is required. The latitude and longitude of the two stations are stated as basic inputs on the basis that they are needed to obtain the path profile. Radiometeorological parameters must be obtai
39、ned for a single location associated with the radio path, and for a long path the path-centre should be selected. It is appropriate to obtain the radiometeorological parameters for the transmitter location when predicting its coverage area. 4 Rec. ITU-R P.1812-4 TABLE 1 Basic input data Parameter Un
40、its Minimum Maximum Description f GHz 0.03 3.0 Frequency (GHz) p % 1.0 50.0 Percentage of average year for which the calculated signal level is exceeded pL % 1 99 Percentage of locations for which the calculated signal level is exceeded t, r degrees 80 +80 Latitude of transmitter, receiver t, r degr
41、ees 180.0 180.0 Longitude of transmitter, receiver (positive = East of Greenwich) htg, hrg m 1 3 000 Antenna centre height above ground level Polarization Signal polarisation, e.g. vertical or horizontal ws m 1 100 Width of street. The value of 27 should be used unless specific local values are avai
42、lable. Polarisation in Table 1 is not a parameter with a numerical value. The information is used in 4.3.3 in connection with equations (29a), (29b) and (30). 3.2 Terrain profile A terrain profile for the radio path is required for the application of the propagation prediction method. In principle,
43、this consists of three arrays each having the same number of values, n, as follows: di: distance from transmitter of i-th profile point (km) (1a) hi: height of i-th profile point above sea level (m) (1b) gi hi representative clutter height of i-th profilepoint (m) (1c) where: i: 1, 2, 3 . n = index
44、of the profile point n: number of profile points. There must be at least one intermediate profile point between the transmitter and the receiver. Thus n must satisfy n 3. Such a small number of points is appropriate only for short paths, less than of the order of 1 km. Note that the first profile po
45、int is at the transmitter. Thus d1 is zero and h1 is the terrain height at the transmitter in metres above sea level. Similarly, the n-th profile point is at the receiver. Thus dn is the path length in km, and hn the terrain height at the receiver in metres above sea level. No specific distance betw
46、een profile points is given. Assuming that profiles are extracted from a digital terrain elevation model, a suitable spacing will typically be similar to the point spacing of the source data. The profile points are not required to be equally-spaced, but it is desirable that they are at a similar spa
47、cing for the whole profile. It is desirable to have information on ground cover (clutter) along the path. It is convenient to store clutter categories in an additional array of n points to match the profile height data. The “representative clutter height R” referred to in equation (1c) concerns stat
48、istical height information associated with ground cover classification, such as vegetation and buildings, i.e., a single height value assigned to each ground cover /clutter class. Adding representative clutter heights Rec. ITU-R P.1812-4 5 to a profile is based on the assumption that the heights hi
49、represent the bare surface of the Earth. If the radio path passes over woodland or urbanization where diffraction or sub-path obstruction occurs, in general the effective profile height will be higher because the radio signal will travel over the clutter. Thus a more suitable representation of the profile can be obtained by adding representative heights to account for the clutter. The appropriate addition is not necessarily physical, such as rooftop heights in the case of buildings. Where gaps exist between clutter objects, as seen by the
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