1、QUESTION ITU-R 208-3/3Propagation factors in frequency sharing issues affectingfixed-satellite services and terrestrial services(1990-1993-1995-2002-2005)The ITU Radiocommunication Assembly,consideringa) that propagation data for radio paths are required when planning the sharing of frequencychannel
2、s in radiocommunication systems;b) that, in accordance with the Radio Regulations (RR), a coordination distance orcoordination area should be determined for earth stations in the frequency bands shared betweenspace radiocommunication services and terrestrial services;c) that in the calculation of co
3、ordination distances, all pertinent propagation mechanisms andsystem factors should be taken into account;d) that in the calculation of interference between systems, more detailed consideration of thecontributing propagation mechanisms is required;e) that the World Radiocommunication Conference (WRC
4、-2000) approved a revision ofAppendix 7 (subsequently modified by WRC-03) based on material in RecommendationITU-R SM.1448 which in turn is based on material in Recommendation ITU-R P.620 covering thefrequency range 100 MHz to 105 GHz;f) that Resolution 74 ( Rev.WRC-03) describes a process to keep t
5、he technical bases ofAppendix 7 current,decides that the following Question should be studied1 What is the distribution of signal level variations (both fading and enhancement) and theirduration due to: diffraction; atmospheric mechanisms such as ducting, precipitation scatter, troposcatter and refl
6、ectingatmospheric layers; reflections from the ground and man-made structures; combinations of these mechanisms?- 2 -2 What is the dependence of these effects on location, time, path length and frequency, takinginto consideration the following points: the percentage range of greatest interest is fro
7、m 0.001% to 50%; the reference periods of interest are worst month and average year; path lengths of greatest interest are those up to 1 000 km; however, in areas where ductingis prevalent (e.g. oceans in tropical and equatorial regions) much greater distances shouldalso be considered; the frequency
8、 range of interest is approximately 100 MHz to 500 GHz?3 How may improved models and prediction procedures be developed for precipitationscatter to determine the practical significance of this mode, and how does it depend on rainfall rateand structure and on system geometry?4 What precipitation para
9、meters, in addition to rainfall intensity and height of the 0Cisotherm, can be applied to precipitation-related prediction methods to take account of differentclimates?5 What refractivity parameters can be applied to clear-air prediction methods to take accountof different climates?6 How can scatter
10、 from irregular terrain be quantified (including the effect of vegetation andman-made structures such as buildings)?7 How can interaction between an antenna and the propagation medium be taken into accountwhen considering modes of anomalous propagation (e.g. coupling into and out of ducts and theimp
11、act of use of omnidirectional, sector and high-gain antennas)?8 How may site shielding be evaluated, with special emphasis on a practical procedure forcalculating its magnitude in particular situations (e.g. small earth stations in urban areas)?9 What is the correlation of fading and enhancements of
12、 the signal on separate radio links,and its influence on the statistics of interference?10 What method best describes the differential rain attenuation statistics between a wantedpath and an unwanted path?11 What is a suitable method by which the total effect of the above-mentioned mechanismscan be
13、taken into account when evaluating interference between terrestrial and Earth-space systems;in particular, what improvements can be recommended to the interference prediction methodscontained in Recommendation ITU-R P.452 and to the propagation prediction procedures fordetermining coordination dista
14、nce contained in Recommendation ITU-R P.620, including thealignment of these two methods in order to obtain consistency between the determination ofcoordination area and detailed evaluation of interference in individual cases?12 Which are the most effective clear-air and hydrometeor-scatter propagat
15、ion models to alloweffective frequency coordination and interference potential evaluation between earth stations forgeostationary-satellite systems and those for non-geostationary satellite systems sharing the samefrequencies on a “bidirectional working” basis?NOTE 1 Priority will be given to studies relating to 2, 5, 6, 8, 9 and 10.Category: S2
