1、Li855212 05YlQ56 801 W INTERNATIONAL TELECOMMUNICATION UNION Rad i oco m m u ni ca t io n Bu rea u Geneva, 1996 HANDBOOK RADIOWAVE PROPAGATION INFORMATION FOR COMMUNICATIONS PREDICTIONS FOR EARTH-TO-SPACE PATH N:BRSGBSG3HBKWBK96CHPTRl E. WW6 4855212 054LBLO 4bT E . - 111 - PREFACE This Handbook has
2、been developed by experts of Working Party 3M (Point-to-point and Earth-space propagation) of ITU-R Study Group 3 (Radiowave propagation), under the chairmanship of Mr. M.P.M. Hall (U.K.). Major contributors to the Handbook were: Dr. Dr. Dr. Mr. Ms. Dr . Prof. Dr. Mr. Dr. Mrs. Jeremy Allnutt J.P.V.
3、Poiares Baptista Asoka Dissanayake Glenn Feldhake Fatim Haidara Yoshio Karasawa Marlene Pontes David Rogers Erkki Salonen Haim Soicher Carol Wilson The Handbook was edited by Mrs Carol Wilson and Dr. David Rogers. N:BRSGBSG3HBKHBK96CHPTRl E. WW6 Previous page is blank. 4855232 054LBbL 3Tb O . iv . T
4、ABLE OF CONTENTS Page CHAPTER 1 . INTRODUCTION 1.1 1.2 Relationship of this Handbook to Recommendations of ITU-R Study Group 3 . Application of the Earth-space Handbook . CHAPTER 2 - PROPAGATION EFFECTS OF THE TROPOSPHERE AND THE IONOSPHERE CHAPTER 3 . PROPAGATION LOSS Attenuation due to atmospheric
5、 gases . 3.1 3.1.1 Procedure for calculating gaseous attenuation Attenuation by precipitation and clouds 3.2.1 3.2 Prediction of attenuation statistics for an average year (from point rainfall rate) . 3.2.1 . 1 Basis of prediction method for rain attenuation 3.2.1.2 Equivalent rain cell length . 3.2
6、.1.3 Effective rain height 3.2.1.4 Specific attenuation . 3.2.2 Long-term frequency and polarization scaling of rain attenuation statistics 3.2.3 Seasonal variations - worst month . 3.2.4 Discussion of model evaluation (testing) 3.2.5 Example calculation 3.2.6 Cloud attenuation 3.3 Diversity and spa
7、tial features of rain . 3.3.1 Site diversity 3 . 3.1.1 Reference distribution . 3.3.1.2 Diversity improvement factor . 3.3.1.3 Diversity gain 3.3.1.4 Instantaneous diversity gain 3 3.1.5 Comparison of diversity improvement factor and diversity gain as measurement parameters . 3.3.1.6 Example calcula
8、tions using the recommended site diversity prediction procedures 3 3.1.7 Factors affecting site diversity performance . Statistical distribution of signal level for large areas 3 3.3.1 Orbital diversity . Time diversity . . ?-I ? 3.3.2 3.3.3 Other diversity schemes 3.3.3.2 Frequency diversity . 3 .
9、3 . 3 . 3 ? ? ?*? 4 5 5 6 7 7 8 8 8 9 10 11 11 13 14 15 15 15 16 19 24 25 26 26 26 N:BRSGBSG3HBKHBK96CHPTRI E.WW6 4855232 0543862 232 I -v- 3.4 3.5 Characteristics of precipitation events . 27 3.4.1 Duration of individual fades 28 3.4.2 Interfade and inter-event intervals . 31 3.4.3 Rates of change
10、of attenuation 33 3.4.4 Correlation of instantaneous values of attenuation at different frequencies . 34 Sand and dust effects . 34 3.5.1 General 34 3.5.2 Categories of dust storms 35 3.5.3 Propagation impairment prediction models for dust effects 37 3.5.4 Typical propagation impairment prediction r
11、esults . 38 References for Chapter 3 . CHAPTER 4 . SKY NOISE TEMPERATURE CONTRIBUTIONS . 4.1 4.2 Galactic and other extraterrestrial noise sources . 4.3 Noise from the surface of the Earth and man-made sources . 4.4 Example problem . References for Chapter 4 . CHAPTER 5 - PATH DEPOLARIZATION Atmosph
12、eric noise temperature effects on Earth-space paths . 5.1 5.2 5.3 Introduction 5.1.1 5.1.2 Systems importance of depolarization . 5.1.3 5.1.4 Polarization states 5.1.5 Physical causes of depolarization Cross-polarization isolation and discrimination Polarization orthogonality and mismatch Relation b
13、etween depolarization and attenuation Computation of long-term XPD statistics . Ice depolarization Dependence on time percentage Dependence on path configuration Evaluations of model performance Long-term frequency and polarization scaling Faraday rotation in the ionosphere 5.3.2 Precipitation effec
14、ts . 5.3.2.1 Differential attenuation 5.3.2.2 Differential phase 5.2.1 5.2.1 . 1 5.2.1.2 Frequency dependence 5.2.1.3 5.2.2 5.2.3 5.2.4 5.2.5 Dependence of XPD and XPI on physical processes . 5.3.1 Joint statistics of XPD and attenuation 40 46 46 46 47 47 48 49 49 49 49 50 50 51 53 53 53 54 55 56 57
15、 57 58 58 58 58 58 59 N:BRSGBSG3HBKHBK96CHPTRI E . WW6 W 4655232 0543863 179 . vi . 5.4 5.5 5.6 Data relevant to cross-polarization compensation . Incorporation of path XPD into system XPI Example calculation of path XPD . Step-by-step application of the method . Example of a system application . 5.
16、6.1 5.6.2 References for Chapter 5 . CHAPTER 6 . CLEAR AIR EFFECTS 6.1 6.2 Loss due to defocusing and wave-front incoherence . Scintillation and multipath effects . 6.2.1 General 6.2.2 Background of the scintillation model 6.2.2.1 Seasonal and diurnal variations . 6.2.2.2 Frequency dependence 6.2.2.
17、3 Elevation angle dependence 6.2.2.4 Antenna aperture diameter dependence . 6.2.2.5 Probability density function (PDF) of signal-level variations Accuracy and applicable range of the prediction method . 6.2.3.1 6.2.3.2 Accuracy and applicability of PDF prediction Signal variations at elevation angle
18、s lower than about 5“ . 6.2.4.2 Characteristics of low-angle fading . 6.2.2.6 Polarization dependence Accuracy and applicability of r.m.s. fluctuation prediction 6.2.3 6.2.4 6.2.4.1 Empirical model 6.3 Propagation delays . 6.4 Angle of arrival References for Chapter 6 . CHAPTER 7 . TRANSIONOSPHERIC
19、PROPAGATION 7.1 7.2 7.3 Introduction Total Electron Content (TEC) . Effects due to background ionization 7.3.1 Faraday rotation . 7.3.2 Group delay . 7.3.3 Dispersion 7.3.4 Doppler frequency shift . 7.3.5 Direction of arrivai of the ray 7.3.6.1 Auroral absorption . 7.3.6.2 Polar cap absorption 7.3.6
20、 Absorption . 59 60 61 61 63 66 69 69 69 69 70 70 72 72 72 72 73 73 73 74 74 75 78 78 80 81 82 83 83 83 83 84 86 86 86 87 87 87 N:BRSGBSG3HBKWBK96CHPTR 1 E . WW6 7.4 Effects due to ionization irregularities . 7.4.1 Scintillation effects 7.4.2 Geographic, seasonal and solar dependence 7.4.3 Scintilla
21、tion models . 7.5 Conclusion . References for Chapter 7 . CHAPTER 8 . SURFACE REFLECTIONS AND LOCAL ENVIRONMENTAL EFFECTS (OF PARTICULAR INTEREST TO MOBILE- SATELLITE SYSTEMS) . 8.1 Introduction 8.2 Effects of the Earths surface . 8.2.1 Reflection from the Earth 8.2.1.1 Specular reflection from a pl
22、ane Earth 8.2.1.2 Specular reflection fi-om a smooth spherical Earth . 8.2.1.3 Divergence factor 8.2.1.4 Reflection from rough surfaces . 8.2.1.5 Reflection multipath Fading due to sea reflection . 8.2.2.1 General 8.2.2.2 Sea surface characteristics . 8.2.2.3 Fading calculation model 8.2.3 Shadowing
23、 and blockage . 8.2.3.2 Building shadowing . Fading in AMSS due to land reflection . Interference from adjacent satellite systems 8.2.5.1 General 8.2.5.2 Basic assumptions of the model 8.2.5.3 Prediction accuracy . 8.2.6 Example problem . 8.2.7 Results of experimental measurements . 8.2.7.1 LMSS mea
24、surements . 8.2.7.2 Measurements of sea-reflection multipath effects . 8.3 Local environmental effects . 8.3.1 Noise contribution of local environment . 8.3.2 Ship superstructurehlockage . 8.3.3 Motion of mobile antenna . 8.2.2 8.2.3.1 Tree shadowing . 8.2.4 8.2.5 88 88 89 90 92 93 95 95 95 96 96 97
25、 98 99 101 102 102 102 104 111 111 115 117 118 118 118 120 120 123 123 126 127 127 128 129 N:BRSGBSG3WBKWBK96CHPTRi E.WW6 YB552L2 054Lb5 T4L 11111 . viii . References for Chapter 8 . 9.1 Equiprobable summation . CHAPTER 9 . COMBINED EFFECTS MODELLING 9.2 Convolution . 9.3 Temporal segmentation . 9.4
26、 Root-Square summing . 9.5 Example . References for Chapter 9 . 131 134 134 135 135 136 136 137 N:BRSGBSG3HBKWBK96CHPTRl E.WW6 E Y855212 05418bb 988 -1- CHAPTER 1 INTRODUCTION 1.1 The Handbook on “Radiowave Propagation Information for Predictions for Earth-Space Path Communications” supplies backgro
27、und and supplementary information on radiowave propagation effects. It serves as a companion volume and guide to the Recommendations that are maintained by Study Group 3 (SG 3) of the ITU Radiocommunication Sector (ITU-R) to assist in the design of Earth-space communication systems. This handbook is
28、 intended to be used in conjunction with the published SG 3 Recommendations to assist the user in the application of those Recommendations. It applies to SG 3 Recommendations containing impairment prediction methods and engineering advice on radiowave propagation for the fixed-satellite service (FSS
29、); broadcasting-satellite service (BSS); maritime mobile-satellite service (MMSS); land mobile-satellite service (LMSS); and aeronautical mobile-satellite service (AMSS). Specific versions of the corresponding Recommendations that are used throughout this handbook are: Relationship of this Handbook
30、to Recommendations of ITU-R Study Group 3 ITU-R P.618-4: ITU-R P.679-1: ITU-R P.680-1: ITU-R P.681-2: ITU-R P.682-1: ITU-R P.53 1-3: Propagation data and prediction methods required for the design of Earth-space telecommunications systems, Geneva, 1996. Propagation data required for the design of br
31、oadcasting-satellite systems. Geneva, 1994. Propagation data required for the design of Earth-space maritime mobile telecommunication systems, Geneva, 1994. Propagation data required for the design of Earth-space land mobile telecommunication systems, Geneva, 1996. Propagation data required for the
32、design of Earth-space aeronautical mobile telecommunication systems, Geneva, 1994. Ionospheric effects influencing radio systems involving spacecraft, Geneva, 1 994. This handbook is keyed to the above Recommendations and uses the same terminology and notation. Reference is made to equation numbers
33、in the Recommendations, for application as a companion volume. Duplication of propagation data from the Recommendations is intentionally minimal, and the prediction methods are found in the Recommendations. It is preferable, of course, to use the latest version of the Recommendations for system calc
34、ulations. Proper application of the Recommendations for the Earth-space services requires radiometeorological and other data from additional ITU-R Recommendations. In addition, significant background material can be found in the ITU-R Handbook on Radiometeorology. The versions of the other Recommend
35、ations referred to in this handbook are the following: ITU-R P.3 1 1-7: Acquisition, presentation and analysis of data in studies of tropospheric ITU-R P.372-6: ITU-R P.453-5: ITU-R P.526-4: propagation, Geneva, 1994. Radio Noise, Geneva, 1994. The radio refractive index: its formula and refractivit
36、y data, Geneva, 1996. Propagation by diffraction, Geneva, 1996. N:BRSGBSG3HBKHBK96CHPTRl E.WW6 4855212 0541867 814 -2- ITU-R P.527-3: ITU-R P.530-6: ITU-R P.581-2: ITU-R P.676-2: ITU-R P.834-1: ITU-R P.836: ITU-R P.837-1: ITU-R P.838: ITU-R P.839: ITU-R P.840-1: ITU-R P.841: ITU-R P. 1057: Electrica
37、l characteristics of the surface of the Earth, Geneva, 1994. Propagation data and prediction methods required for the design of terrestrial line-of-sight systems, Geneva, 1996. The concept of “worst month”, Geneva, 1994. Attenuation by atmospheric gases, Geneva, 1996. Effects of tropospheric refract
38、ion on radiowave propagation, Geneva, 1994. Surface water vapour density, Geneva, 1994. Characteristics of precipitation for propagation modelling, Geneva, 1994. Specific attenuation model for rain for use in prediction methods, Geneva, 1994. Rain height model for prediction methods, Geneva, 1994. A
39、ttenuation due to clouds and fog, Geneva, 1994. Conversion of annual statistics to worst-month statistics, Geneva, 1994. Probability distributions relevant to radiowave propagation modelling, Geneva, 1 994. 1.2 Accurate propagation information is required to support the design, implementation and op
40、eration of most modem satellite communication systems. The propagation behaviour of radiowaves, in the ionosphere and the troposphere, near the Earths surface, or upon reflection from the surface, is of concern to telecommunication system designers intending to use an atmospheric propagation medium
41、for the transmission of electromagnetic energy between antennas in the system. Signal degradations that occur with sufficient frequency and intensity to affect the performance and availability objectives must be estimated and accounted for in the link budget as part of the system design. Methods are
42、 thus required to predict the magnitude and occurrence of relevant propagation impairments with sufficient accuracy for engineering applications. This handbook provides background on the physical causes for path impairments, the bases for the prediction methods that are found in the Recommendations,
43、 and additional information considered useful for engineering applications, including data and models that are yet inadequate for Recommendation status. As far as possible, the prediction methods are evaluated by testing with measured data from the data banks of SG 3, and the results are used to ind
44、icate the accuracy of the prediction methods and the variability of the measured data. This Handbook addresses propagation impairments for systems operating above 1 O0 MHz; this includes all current frequency allocations for satellite systems. The importance of a particular propagation impairment to
45、 an Earth-space telecommunication system depends on wave frequency and polarization, path geometq (e.g., elevation angle of the path), system performance objectives, achievable performance margins, details of the system configuration (e.g., whether dual-polarized operation is intended), and local io
46、nospheric and meteorological features. For example, rain attenuation is often the dominant path impairment at frequencies above about 1 O GHz, but is of negligible consequence for a mobile-satellite system operating at 1.5 GHz. Conversely, surface reflections, shadowing and blockage are of paramount
47、 importance for a mobile system, but seldom critical for a terminal operating in the FSS, for which terminal placement can be planned to minimize such effects. Application of the Earth-space Handbook N:BRSGBSG3iBKVIBK96CHPTR 1 E. WW6 4855212 054Lb 750 D -3- Impairment Physical causes Frequency f abo
48、ut 10 GHz f about 10 GHz 6.2 614 GHz systems f m .- Y .c) c) 20 15 10 5 O 0.0001 0.001 0.01 o. 1 1 10 percentage of time the attenuation is exceeded FIGURE 3.2 Example of rain attenuation statistics 3.2.6 Cloud attenuation The formation of clouds can be due to a variety of atmospheric processes, whi
49、ch result in cloud layers at many altitudes. The World Meteorological Office (WMO) specifies nine different cloud types for each of three cloud heights: low, middle, and high. Based on observations using these WO classifications, maps of cloud cover have been prepared Warren et al., 19861 that show that clouds of one type or another exist on average for 53% of the time over land. Any satellite-to-ground link needing to maintain communications for a large fiaction of the time will, therefore, have to be designed to operate through clouds. N
