1、192 Rec. ITU-R PI.533-4 RECOMMENDATION ITU-R PI.533-4 HF PROPAGATION PREDICTION METHOD* (Question 223/3) ( 197 8- 1982- 1990- 1992- 1 994) The ITU Radiocommunication Assembly, considering a that the ex-CCIR developed and evaluated three separate computer-based methods of field-strength estimation as
2、 presented in Report ITU-R PI.252, Supplement to Report ITU-R PI.252, Report IT-R PI.894 and Annex 1 of this Recommendation which has been derived from Report ITU-R PI.894; b) that tests against ITU-R Data Bank D1 show that the method of Annex 1 has comparable accuracy to the other more complex meth
3、ods; cl that associated computer codes have been formulated and made available to the Radiocommunication Bureau (see Resolution ITU-R 63), recommends that the information contained in Annex 1 should be used in computerized prediction of sky-wave propagation that administrations and ITU-R should ende
4、avour to improve prediction methods to enhance operational 1. at frequencies between 2-30 MHz; 2. facilities and to improve accuracy. ANNEX 1 CONTENTS 1. 2. 3. 3.1 3.2 3.3 3.4 3.5 3.5.1 3.5.1.1 3.5.1.2 3.5.2 3.5.2.1 3.5.2.2 Introduction Location of control points Basic and operational maximum usable
5、 frequencies Basic maximum usable frequencies E-layer critical frequency (foE) E-layer basic MUF F2-layer characteristics F2-layer basic MUF Lowest-order mode Paths up to d, (km) (d- : maximum hop length for F2 mode) Paths longer than dttlM (km) Higher-order modes (paths up to 9 O00 km) Paths up to
6、d, (km) Paths longer than d, (km) * A computer program associated with prediction procedures described in this Recommendation is available from the Radiocommunication Bureau; for details see Resolution ITU-R 63. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Info
7、rmation Handling ServicesRec IT-R PI.533-4 193 3.6 4. 5. 5.1 5.1.1 5.1.2 5.1.3 5.2 5.3 6. 7. 8. 9. 10. The path operational MUF E-layer maximum screening frequency (f,) Median sky-wave field strength Paths up to 7 O00 km Modes considered Elevation angle Field-strength determination Paths longer than
8、 9 O00 km Paths between 7 O00 and 9 O00 km Median available receiver power Monthly median signal-to-noise ratio Signai-to-noise ratios for other percentages of time Lowest usable frequency (LUF) Basic circuit reliability (BCR) 1. Introduction This propagation prediction method for use in the estimat
9、ion of reliability and compatibility between frequencies of about 3 MHz and 30 MHz derives from a method first proposed in 1983 by CCIR Interim Working Party 6/12 with later refinements following considerations by the WARC for HF broadcasting, the CCIR, ITU-R, broadcasting and other organizations. T
10、he procedure applies a ray-path analysis for path lengths up to 7000 km, composite mode empirical formulations from the fit to measured data beyond 9 O00 km and a smooth transition between these two approaches over the 7 000-9 O00 km distance range. Monthly median basic MUF, incident sky-wave field
11、strength and available receiver power from a lossless receiving antenna of given gain are determined. Signal strengths are standardized against an ITU-R measurement data bank. The method requires the determination of a number of ionospheric characteristics and propagation parameters at specified “co
12、ntrol points”. A computer program in both mainframe and microcomputer versions has been developed for this prediction method. Information on the availability of the program is found in Resolution ITU-R 63. 2. Location of control points Propagation is assumed to be along the great-circle path between
13、 the transmitter and receiver locations via E modes (up to 4000 km range) and F2 modes (for all distances). Depending on path length and reflecting layer, control points are selected as indicated in Table 1. 3. Basic and operational maximum usable frequencies The estimation of operational MUF, the h
14、ighest frequency that would permit acceptable operation of a radio service, is in two stages: first, the estimation of basic MUF from a consideration of ionospheric parameters and second, the determination of a correction factor to allow for propagation mechanisms at frequencies above the basic MUF.
15、 COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services194 O d-. Rec. ITU-R PI.533-4 M M T + 1000,R - 1000 - M T + do12,R - dol2 - - TABLE 1 Locations of control points for the determination of basic MUF, E-layer screening, ray-path mirror-r
16、eflection heights and ionospheric absorption a) Basic MUF and associated electron gyrofrequency O 3.33 and x, =flfoF2 1 1, wherefis the wave frequency hi = h or 800 km, whichever is the smaller h = Al + BI 2.4-a for B1 and a 2 O = Al + BI otherwise Al = 140 + (H - 47)El B1 = 150 + (H - 17)Fl - A1 El
17、 = - 0.09707 X, + 0.6870 xr2 - 0.7506 X, + 0.6 FI is such that: F1 = - 1.862 + 12.95 - 32.03 + 33.50 - 10.91 for x, I 1.71 Fi = 1.21 + 0.2 for x, 1.71 a varies with distance d and skip distance d, as: U = (d - d,)/( H + 140) d, = 160 + (H + 43)G G = - 2.102 + 19.50 - 63.15 + 90.47 - 44.73 G = 19.25
18、for x, I 3.7 for x, 3.7 Forx3.33andxr For x 5 3.33 h, = 115 + H J + Ud or 800 km, whichever is the smaller with J = -0.71263 + 5.863 - 16.13 + 16.07 and U = 8 x 10-5(H - 80)(1 + 11-.) + 1.2 x 1C3Hy-3.6 In the case of paths up to d,ar (km) h, is evaluated at the mid-point of the path: for longer path
19、s it is determined for all the control points given in Table lc) and the mean value is used. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesRec. IT-R PI.533-4 51.3 Field strength determination For each mode w selected in $ 5.1.1, the
20、median field strength is given by: 199 dB( 1 pV/m) (15) where: f: transmitting frequency (MHz) P, : transmitter power (dB(1 kW) G,: transmitting antenna gain at the required azimuth angle and elevation angle (A) relative to an isotropic antenna (dB) Lbf: .basic free-space transmission loss (a) given
21、 by: with: p : virtual slant range (km) n with ._ c p = 2Ro 1 Li : absorption loss (dB) given by: d - sin - 2 RO - cos * + &-I k 677.2 n . sec i 1 cf + f)l.98 + 10.2 . k - C Ij j= 1 L. = Ij = (1 + 0.0037 R12) . (00.881 xj)1.3 1 The minimum value of k C i, is set to 0.1, and: i: k: fH angle of incide
22、nce at 110 km number of control points (from Table Id) mean of the values of electron gyrofrequency, for a height of 100 km, determined at the control points given in Table Id) solar zenith angle at thejth control point or 102.15 whichever is the smaller. The equation-of-time, for the middle of the
23、month in question, is incorporated in the calculation of this parameter. XJ : COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services200 Rec. ITU-R PI.533-4 For frequencies above the basic MUF, the absorption continues to vary with frequency
24、and is calculated assuming the same ray-paths as those at the basic MUF. L,: correction term to the absorption loss for E modes which do not penetrate the whole of the absorbing layer: forf O, L, = O dB . if L, fb: 2 L, = 130 i - 11 or 8 1 dB whichever is the smaller. For F2 modes forffb: ?li L, = 3
25、6 i - 13 dB dB or 62 dB whichever is the smaller. summed ground-reflection loss at intermediate reflection points: for an n-hop mode L, : LR = 2(n - 1) dB (24) LI, : factor to allow for auroral and other signal losses, given in Table 2. Each value is evaluated in terms of the geomagnetic latitude G,
26、 (N or S of equator) and local time t for an earth-centred dipole with pole at 78.5 N, 48.2“ W: mean values for the control points of Table Id) are taken. In the Northern Hemisphere, winter is taken as December-February, equinox as March-May and September-November and summer as June-August. In the S
27、outhern Hemisphere, the months for winter and summer are interchanged. For G, 90, cosi1% is taken as zero. i90 : I: given in Table 4. angle of incidence at a height of 90 km COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services204 1 1 1 1 1
28、 1 Geographic latitudes ON 1.05 1.02 1.02 1 1 1 One terminal 35“ N 35“ N 35“ N 35“ N-35“ S 35“ N-35“ S 35“ s Other terminai 35“ N 35“ N-35“ S 35“ s 35“ N-35“ S 35“ s 35O s Rec. ITU-R PI.533-4 TABLE 4 Values of I used in the equation for fL J 1.1 1 .os 1 .os 1 1 1 - F 1 .os 1 .o2 1 .o2 1 1 1 - M A -
29、1 1 1 1 1 1 M - 1 1 1 .o2 1 1 .o2 1.0s Month J - 1 1 1 .os 1 1 .os 1.1 J 1 1 1 .os 1 1 .os 1.1 A 1 1 1 .o2 1 1 .o2 1 .O5 S D - 1.1 1 .os 1 .os 1 1 1 A, : winter-anomaly factor determined at the path mid-point which is unity for geographic latitudes O to 30“ and at 90“ and reaches the maximum values
30、given in Table 5 at 60“. The values at intermediate latitudes are found by linear interpolation. TABLE 5 Values of the winter-anomaly factor A,. at 60“ geographic latitude used in the equation for fL The values offL are calculated at each hour until the local time tr whenfL I 2fm where: MHz During t
31、he next three hoursfL is calculated from: fL = 2jLN ,-0.23 t (33) where t is the time in hours after t,. For subsequent hoursfL = fLNuntil the time when equation (31) gives a higher value. ITU-R RECflN PI.533-4 94 = 4855232 0522983 T39 = COPYRIGHT International Telecommunications Union/ITU Radiocomm
32、unicationsLicensed by Information Handling ServicesRec. IT-R PI.533-4 5.3 Paths between 7000 and 9 O00 km 205 In this distance range the median sky-wave field strength Eli is determined by interpolation between values Ers and Er. Ers is the root-sum-squared field strength given by equation (25) for
33、up to the three strongest of the possible six F2 modes meeting the three criteria given in 8 5.1.1. Etl refers to a composite mode as given by equation (26). with (4 - XJ D - 7000 2 O00 Xi = Xs + where: x, = 100.01 Et, The basic MF for the path is equal to the lower of the F2 (dm)MUF values given fr
34、om equation (3) for the two control points noted in Table la). 6. Median available receiver power For distance ranges up to 7 O00 km, where field strength is calculated by the method of 8 5.1, for a given mode w having sky-wave field strength Em (dB(1 pV/m) at frequencyf(MHz), the corresponding avai
35、lable signal power P, (dBW) from a lossless receiving antenna of gain G, (dB relative to an isotropic radiator) in the direction of signal incidence is: The resultant median available signal power P, (dBW) is given by summing the powers arising from the different modes, each mode contribution depend
36、ing on the receiving antenna gain in the direction of incidence of that mode. For N modes contributing to the summation: N P, = lologo c 1OP-O dBW w=l For distance ranges beyond 9000 km, where field strength is calculated by the method of 9 5.2, the field strength Ell is for the resultant of the com
37、posite modes. In this case P, is determined using equation (33, where G, is the largest value of receiving antenna gain at the required azimuth in the elevation range O to 8“. In the intermediate range 7000 to 9000 km, the power is determined from equation (34) using the powers corresponding to E, a
38、nd Erl. 7. Monthly median signal-to-noise ratio Recommendation ITU-R PI.372 provides values of median atmospheric noise power for reception on a short vertical lossless monopole antenna above perfect ground and also gives corresponding man-made noise and cosmic noise intensities. Let the resultant e
39、xternal noise factor be Fa (dB(kTb) at frequencyf(MH2) where reception is on such an ideal short lossless vertical monopole over a perfectly conducting ground plane with k the Boltzmann constant and T a reference temperature of 288 K. Then, in general, when using some other practical reception anten
40、na the resultant noise factor may differ from this value of Fa (see Recommendation IT-R PI.372). However, in the absence of complete noise measurement data for different antennas, as a first approximation, it is appropriate to assume that the same Fa applies. Hence the monthly median signai-to-noise
41、 ratio SIN (dB) achieved within a bandwidth b (Hz) is: ITU-R RECMN PI.533-4 94 m 4855232 0522984 975 COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services206 Rec. ITU-R PI.533-4 8. Signal-to-noise ratios for other percentages of time Use is
42、 made of equations (1 1) and (12) of Report ITU-R PI.266 to determine the signal-to-noise ratio for a specified percentage of time in terms of the within-an-hour and day-to-day decile deviations of the signais and the noise. Signal fading allowances are those adopted by the Second Session of the Wor
43、ld Administrative Radio Conference for the Planning of HF Bands Allocated to the Broadcasting Service (Geneva, 1987) (WARC HFBC-87) with a short-term upper decile deviation of 5 dB and a lower decile deviation of 8 dB. For long-term signal fading the decile deviations are taken as a function of the
44、ratio of operating frequency to the path basic MUF as given in Table2 of Recommendation ITU-R PI.842. In the case of atmospheric noise, the decile deviations of noise power arising from day-to-day variability are taken from Recommendation ITU-R PI.372. No allowance for within-an-hour variability is
45、currently applied. For man- made noise, in the absence of direct information on temporal variability, the decile deviations are taken as those given in Recommendation ITU-R PI.372 which strictly relate to a combination of temporal and spatial variability. The combined within-an-hour and day-to-day d
46、ecile variability of galactic noise is taken as +2 dB. 9. Lowest usable frequency (LUF) The LUF is defined in Recommendation ITU-R PI.373. Consistent with this definition, this is evaluated as the lowest frequency, expressed to the nearest 0.1 MHz, at which a required signal-to-noise ratio is achiev
47、ed by the monthly median signal-to-noise. 10. Basic circuit reliability (BCR) The BCR is defined in Recommendation ITU-R PI.842. It is evaluated on the basis of signallnoise ratios incorporating within-an-hour and day-to-day decile variations of both signal field strength and noise background. Distr
48、ibution about the median uses a distribution formulation from Recommendation ITU-R PI.842. Caution is given that this approach makes no allowance for system degradation due to signal dispersion such as can be particularly important when dealing with digital transmissions. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services
