1、C:DOCUMENTS AND SETTINGSQGV33745MY DOCUMENTSDOWNLOADSR-QUE-SG04.208-1993-MSW-E.DOC 17.10.03 15.07.10 QUESTION ITU-R 208/4 Use of statistical and stochastic methods in evaluation of interference between satellite networks in the fixed-satellite service (1993) The ITU Radiocommunication Assembly, cons
2、idering a) that the density of satellites in the geostationary-satellite orbit (GSO) is governed by the interference deemed to be acceptable to each network; b) that the computation of interference is currently performed by deterministic methods which, in general, assume worst-case conditions in ord
3、er to avoid unacceptable levels in all cases; c) that this approach sometimes leads to unduly conservative estimates, resulting in inefficient use of orbit capacity; d) that many of the technical characteristics of satellite networks which affect performance and orbit spectrum/utilization have rando
4、m effects which are either stochastic (time varying) or statistical (time invariant); e) that there are stochastic/statistical elements in the interference environment, including inter alia satellite and earth-station antenna side-lobe gains, earth-station locations, satellite station-keeping tolera
5、nces, satellite network parameters, transponder frequency plans, aggregate-to-single entry interference ratios; f) that such stochastic/statistical elements may be represented by random parameters which vary with time, with space or with operational circumstances, and are in most cases variables whi
6、ch are independent of each other; g) that mathematical techniques exist by which the joint probability density function for interference may be computed in any given case; h) that the use of such mathematical techniques would often lead to a less conservative estimate of interference but nevertheles
7、s ensure the required degree of protection to coordinating parties; j) that increased use of statistical and stochastic properties of GSO satellite network characteristics may facilitate coordination; k) that, whilst stochastic/statistical techniques would be useful in coordination exercises, there
8、may be risks in embodying them in the determination of the need to coordinate; l) that non-GSO satellites (particularly Low Earth Orbit) can also operate in the fixed-satellite service; m) that interference between non-GSO satellite networks and between non-GSO and GSO networks may have pseudo-rando
9、m characteristics, decides that the following Question should be studied 1 What elements in the calculation of inter-network interference are of a stochastic or statistical nature? - 2 - 4/1-E C:DOCUMENTS AND SETTINGSQGV33745MY DOCUMENTSDOWNLOADSR-QUE-SG04.208-1993-MSW-E.DOC 17.10.03 15.07.10 2 What
10、 is the independent parameter for each of the random elements, and what is the mathematical nature of the statistical variability? 3 How should these random variables be combined to yield overall probability density functions for the interference? 4 What confidence limits or similar criteria should
11、be used to quantify acceptable interference in terms of the overall probability density functions? 5 To what extent would the usable capacity of the GSO be increased by the application of the stochastic and statistical approaches relative to the deterministic approach? further decides 1 that the results of these studies should lead to an appropriate Recommendation by 2006. _
