1、HTTP:/WWW.ITU.INT/DMS_PUB/ITU-R/OPB/QUE/R-QUE-SG03.206-3-2000-MSW-E.DOC 16.10.03 14.07.10QUESTION ITU-R 206-3/3Propagation data and prediction methods for fixed- andbroadcasting-satellite services(1990-1993-1995-1997-2000)The ITU Radiocommunication Assembly,consideringa) that, in the design of fixed
2、- and broadcasting-satellite services, an accurate knowledge ofthe distributions in time and space of radiowave propagation phenomena in the lower atmosphere,and of their dependence on various factors, is important to the determination of system performanceand of interference to and from space stati
3、ons;b) that radiowave propagation data for the fixed- and broadcasting-satellite services arerestricted to certain areas and link parameters (e.g. frequency, polarization, elevation angle) and thatfurther data are needed,decides that the following Question should be studied1 What is the long-term st
4、atistical distribution in time and space, including consideration ofdiurnal aspects and the worst month, of: co-polar attenuation (CPA), tropospheric scintillation, and cross-polar discrimination(XPD) induced by constituents in the lower atmosphere; refraction, beam divergence, and incoherence of ra
5、diowaves passing through the loweratmosphere?2 What is the dependence of these distributions on the antenna size, frequency, polarization,angle of elevation, geographic latitude, rain climate, and atmospheric composition, as well as theeffects of terrain, vegetation, and man-made structures, on thes
6、e distributions?3 What method should be used for the prediction of these distributions, and their dependenceon the above parameters, in particular low elevation angle effects?4 What precipitation parameters, in addition to rainfall intensity, can be applied toprecipitation-related prediction methods
7、 to take account of different climates?5 What are the statistical characteristics of building and vehicle signal entry loss, and howdoes the loss depend on frequency, path elevation angle, and the location within the structure orvehicle?6 What refractivity parameters, in addition to, or instead of,
8、refractivity gradient statistics inthe first 100 m of the atmosphere, can be applied to clear-air prediction methods to take account ofdifferent climates?7 What methods should be used to take account of both the simultaneous and the long-termcumulative effects of radiowave propagation mechanisms occ
9、urring at the same time along thesame path (e.g. tropospheric scintillation and rain attenuations)?8 What is: the frequency of occurrence and duration of fades exceeding specified values and the rateof change of received signals in these fades;- 2 -3/1-EHTTP:/WWW.ITU.INT/DMS_PUB/ITU-R/OPB/QUE/R-QUE-
10、SG03.206-3-2000-MSW-E.DOC 16.10.03 14.07.10 the proportion of fades occurring during the available time as defined inRecommendation ITU-R F.557?9 What information is required on the dynamics of the propagation medium to enableimpairment countermeasure techniques (e.g. up-link power control, site diversity, depolarization,pre-compensation and resource sharing) to be designed?10 How is link performance affected in the case of a varying elevation angle?NOTE 1 Priority is to be given to studies relating to 3, 4 and 5._
